3.4: Health Promotion
By the end of this section, you will be able to:
- Discuss the reproductive system structures and functions of those assigned female at birth across the lifespan
- Describe patient education on the various self-care measures important to promote expected growth and development from puberty onward in those assigned female at birth
Understanding the reproductive system is crucial to a person’s health promotion and disease prevention. By comprehending the intricate structures and functions of the reproductive system, nurses and health-care providers can develop effective strategies for promoting overall well-being, preventing diseases, and addressing specific reproductive health concerns. The nurse can explore the complexities of fertility, menstrual health, contraception, pregnancy, and menopause and provide the necessary information to support and empower persons AFAB.
Structures of the Reproductive System
The reproductive system plays a central role in reproduction and the production of sex hormones. Learning the anatomy is essential for understanding the physiologic processes involved in the reproductive health of persons assigned female at birth.
External Genitalia
The external genitalia, known as the vulva, of the person AFAB includes several structures that play a crucial role in sexual function, reproduction, and protection (Figure 3.3).
The mons pubis is a rounded mound of fatty tissue located above the pubic bone. It becomes covered with pubic hair during puberty . The labia majora are the outer, more prominent skin folds and fatty tissue surrounding and protecting the vaginal opening. The labia majora are often covered with pubic hair. The labia minora are the inner, smaller folds of skin located within the labia majora. They lie closer to the vaginal opening and do not have pubic hair. The labia minora can vary in size, shape, and color among people. They contain numerous sweat and oil glands.
The clitoris is responsible for most sexual arousal and orgasm and is composed of erectile tissue containing many nerves. The glans of the clitoris is positioned where the labia minora meet at the hood. The clitoris has an internal and external body. The glans lies under the hood, external to the vulva, while the corpus, suspensory ligament, root, and vestibular bulbs are on the interior of the vulva. The clitoris makes an upside-down V-shape and is attached to the pubic symphysis (Figure 3.4).
The urethral opening is located just below the clitoral hood and above the vaginal opening. The vaginal opening is also known as the introitus.
Internal Genitalia
The internal genitalia consist of the vagina, cervix, body of the uterus, fallopian tubes, and ovaries. These structures each have specific functions pertaining to sexual function and childbirth. Figure 3.5 illustrates the internal genitalia.
Vagina
The vagina is a muscular, flexible tube-like structure that varies in length and width among people. It extends from the external opening, known as the vaginal orifice, to the cervix of the uterus. Its walls comprise layers of smooth muscle, connective tissue, and stratified squamous epithelium lining. The inner lining of the vagina contains folds or ridges called rugae. Hormonal fluctuations, particularly fluctuations in estrogen , progesterone , and testosterone , influence the physiology of the vagina. Estrogen promotes the development and maintenance of the vaginal lining and the production of vaginal lubrication.
The vagina has a unique microbial environment, known as the vaginal flora, consisting of a diverse population of microorganisms, primarily Lactobacillus species, which help maintain a healthy vaginal pH and protect against infections. The vaginal pH is normally acidic, ranging between 3.8 and 4.5.
Cervix
The cervix is the lower, narrow portion of the uterus that connects the uterus to the vagina. It is a gateway between these two structures and plays a crucial role in reproductive physiology. The cervix is the mouth to the uterus. During labor, the cervix thins and opens, becoming an extension of the lower uterine segment. In the nonpregnant person, the cervix is firm and closed and prevents infections from bacteria ascending into the uterus. During nonfertile times, cervical mucus is thick and inhibits the transit of sperm into the uterus. During fertile times, cervical mucus is thin and slippery, facilitating the passage of sperm.
Uterus
The uterus is a hollow, muscular organ that plays a crucial role in supporting pregnancy and menstruation. The innermost layer of the uterus is called the endometrium. The endometrium is the layer that thickens and prepares for embryo implantation. The middle layer of the uterus is the myometrium, composed of smooth muscle tissue. The myometrium is responsible for strong contractions during labor and childbirth. It undergoes significant changes during pregnancy to accommodate the growing fetus and facilitate labor. The outer layer of the uterus is the perimetrium, consisting of a serous membrane that covers the uterus.
Ovaries
The ovaries are the organs that produce and release the egg and the hormones estrogen and progesterone. They are almond-shaped reproductive organs, each measuring approximately 3 to 5 centimeters (cm) in length and 1.5 to 3 centimeters (cm) in width. They are situated on either side of the uterus, near the lateral pelvic wall, within the ovarian fossa (a depression in the posterior pelvic wall). They have a smooth, shiny, and slightly uneven outer surface of epithelial cells; an inner, softer tissue called the ovarian medulla; and a denser region called the ovarian cortex.
Fallopian Tubes
The fallopian tubes, also called the uterine tube or oviducts, are a pair of slender, hollow tubes that extend from the uterus out toward the ovaries. The fallopian tubes play a vital role in fertilization and early embryonic development.
The infundibulum is the funnel-shaped fallopian tube opening that surrounds the ovary. At the outer end of each fallopian tube are finger-like projections called fimbriae. The fimbriae create a sweeping motion that helps capture the released egg from the ovary and guide it into the tube. The ampulla is the widest and longest part of the Fallopian tube. The isthmus is the narrowest and shortest fallopian tube segment, connecting the ampulla to the uterine cavity. It contains fewer cilia compared to the ampulla (Figure 3.6).
Pelvic Floor Muscles
The muscles of the pelvic floor support the pelvic and abdominal organs; control urinary and bowel continence, urination, and defecation; and assist in the expulsion of the fetus during childbirth (Figure 3.7). Pelvic floor muscles can be damaged by pregnancy, birth, constipation, obesity , and prolonged strain or stretching. When these muscles are damaged, the pelvic organs are no longer supported, and urinary incontinence can occur. In persons with pelvic floor damage, nurses can encourage exercise of the pelvic muscles by performing Kegels (the contraction and release of the pelvic muscles). The nurse can also explain that there are health-care providers who specialize in pelvic floor physical therapy.
Functions of the Reproductive System
The reproductive system includes internal and external structures. The reproductive system controls sexual function and reproduction. The nurse performs an assessment and gets a thorough history to identify reproductive needs or variances in function.
External Genitalia
The external genitalia are involved in sexual arousal, lubrication, protection of internal structures, the passage of urine and menstrual flow, and childbirth. Each structure within the vulva has unique functions and contributes to overall reproductive health and sexual well-being.
The mons pubis and labia majora provide cushioning and protection. The urethra allows the passage of urine, while the vaginal opening allows passage of menstrual flow and a fetus in childbirth. The clitoris contains a high concentration of nerve endings and is central to sexual arousal and orgasm.
Internal Genitalia
The vagina essentially connects the uterus to the external environment.   The lubrication is primarily the result of increased blood flow to the vaginal walls and mucus secretion from the cervix and vaginal walls. Lubrication can also vary depending on arousal level and hormonal changes.
The cervix undergoes dynamic changes during different menstrual cycle phases, sexual arousal, pregnancy, and labor and is influenced by hormones such as estrogen, progesterone, and oxytocin. Estrogen plays a vital role in cervical mucus changes and softening, while progesterone maintains the cervix's integrity during pregnancy. Oxytocin stimulates uterine contractions during labor, leading to cervical dilation.
The cervix contains numerous glands that produce mucus, which, under the influence of hormones, changes in consistency throughout the menstrual cycle. As estrogen levels rise in the cycle, the cervix becomes softer and opens slightly. The cervical mucus becomes abundant, slippery, and stretchy, resembling raw egg whites, to facilitate the passage of sperm through the cervix and into the uterus during ovulation. During sexual arousal, the cervix becomes engorged with blood, and the external os may dilate slightly, allowing easier penetration during intercourse.
The physiology of the uterus is tightly regulated by hormones, including estrogen, progesterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and oxytocin. These hormones orchestrate the cyclical changes that prepare the uterus for pregnancy and regulate uterine contractions during labor.
The ovaries undergo cyclical changes during the menstrual cycle with the goal of oogenesis. The egg cell development and maturation process within the reproductive system that occurs during the follicular phase of the menstrual cycle is called oogenesis (Figure 3.8). Oogenesis is initiated by follicle-stimulating hormone (FSH) released by the anterior pituitary gland. FSH prompts the development of an ovarian follicle, and as it grows, it produces estrogen.
Typically, only one follicle becomes dominant while the others regress. The dominant follicle continues to mature, releasing increasing amounts of estrogen as it approaches ovulation. The surge in estrogen triggers the release of luteinizing hormone (LH) from the anterior pituitary gland. This LH surge causes the dominant follicle to rupture, releasing a mature egg from the ovary, a process known as ovulation.
The physiology of the fallopian tubes is regulated by hormonal and neural control. Hormones such as estrogen and progesterone influence the motility and secretory activity of the tubal epithelium, while neural signals help coordinate muscular contractions for egg and embryo transport.
The ampulla of the fallopian tube is the usual site of fertilization, where the sperm and egg meet. The walls of the ampulla are lined with ciliated epithelial cells that help propel the egg and sperm through the tube toward the body of the uterus. After fertilization, the newly formed embryo begins to divide and undergoes early development. Ciliary movements, muscular contractions, and fluid currents in the fallopian tube help transport the developing embryo toward the uterus for implantation.
Stages of Sexual Development
The stages of sexual development in persons AFAB typically follow a predictable path from puberty to reproductive age to menopause to postmenopause. Each individual progresses through these stages at slightly different times. The stages of sexual development can be influenced by multiple factors, both modifiable and non-modifiable.
Menarche
The onset of menstruation, marking the beginning of reproductive capacity, is menarche . It is a significant milestone in physiologic and psychologic development. Menarche typically occurs during adolescence, between the ages of 10 and 16 with the average age being 12.4, although the exact timing can vary widely among people (Lacroix et al., 2023). Young persons AFAB may experience emotional and psychologic changes as they adapt to the physical changes associated with menarche.
Hormonal changes leading to the development of secondary sexual characteristics, such as the growth of breasts and the widening of hips, occur prior to the first menstrual cycle. The Tanner Scale (Figure 3.9) is often used to assess a person’s development of these characteristics.
During menarche, hormonal changes occur in the body, primarily involving the hypothalamic-pituitary-gonadal axis. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH then act on the ovaries to initiate the maturation of ovarian follicles and the release of an egg (ovulation).
The first menstrual period typically consists of relatively small amounts of blood, referred to as menarcheal bleeding. A regular menstrual cycle may take several months or even years to establish as hormonal regulation becomes more consistent. Menstrual cycles typically range from 21 to 45 days with the average being 32.2 days, with menstrual bleeding lasting around 3 to 7 days (Lacroix et al., 2023). Menarche is considered a rite of passage in many societies, and individuals may receive education and support regarding menstrual hygiene, reproductive health, and sexual education. However, cultural norms and practices can also contribute to stigma, taboos, and limited access to menstrual hygiene products and health-care services, negatively impacting individuals' well-being and empowerment . Transgender men can be traumatized by menarche and may experience significant dysphoria.
Transgender Men and Menstrual Cycles
Menstruation is a rite of passage for girls, a sign of womanhood; however, for transgender men, it is an indication that their body is not functioning correctly. This can cause gender dysphoria, depression , anxiety , and suicidal ideation. These persons should be seen by health-care providers who are sensitive to these feelings and who can offer solutions to menstruation, such as menstrual suppression and psychologic help (Weiselberg, 2022).
Menstrual Cycle
The menstrual cycle is characterized by a series of hormonal and physical changes that prepare the body for the possibility of pregnancy. The menstrual cycle typically lasts an average of 28 to 31 days but can vary from person to person. The cycle is counted from the first day of menstrual bleeding to the first day of the next period. The cycle is controlled by the interaction between the hypothalamus, pituitary gland, and ovaries, collectively known as the hypothalamic-pituitary-ovarian (HPO) axis.
The menstrual cycle actually encompasses two cycles, the ovarian cycle and the uterine cycle. They occur simultaneously. The ovarian cycle involves the changes that occur in the ovaries during the cycle, including the follicular phase (days 1 to 14) and luteal phase (days 15 to 28). The follicular phase begins with menstruation as day 1. During this phase, the pituitary gland releases follicle-stimulating hormone (FSH), which stimulates oogenesis . Ovulation occurs approximately midway through the menstrual cycle, usually around day 14, when one mature follicle releases an egg from the ovary, triggered by a luteinizing hormone (LH) surge from the pituitary gland. After ovulation, the ruptured follicle in the ovary forms the corpus luteum. This begins the luteal phase of the ovarian cycle. The corpus luteum produces progesterone, which prepares the uterus for implantation of a fertilized egg. If fertilization does not occur, the corpus luteum regresses, decreasing estrogen and progesterone levels and initiating menstruation.
The uterine proliferative phase also begins at menstruation, day 1, and ends at ovulation. During the proliferative phase, the endometrium prepares for implantation by thickening. After ovulation, the secretory phase begins, and the endometrium becomes a favorable surface for implantation. If fertilization does not occur, the uterus sheds its endometrium, blood, and tissue. This results in menstrual bleeding, typically lasting 3 to 7 days. The average blood loss during menstruation is approximately 30 to 40 milliliters (mL) over a menstrual period. This information is summarized in Figure 3.10.
Various factors influence the menstrual cycle, including a person’s age, overall health, stress levels, and hormonal imbalances. The cycle can vary in length and regularity, and changes in the menstrual cycle can indicate underlying health issues or pregnancy.
Nurses are critical in educating patients about the menstrual cycle and promoting menstrual health. Nurses can educate about what is considered a regular menstrual cycle, including the typical duration, frequency, and amount of menstrual flow. They also discuss what might be considered abnormal, such as irregular cycles or unusually heavy or painful periods. Nurses can offer guidance on proper menstrual hygiene practice s, including how to use and dispose of menstrual products (such as pads, tampons, or menstrual cups) safely and hygienically. Nurses can introduce the concept of fertility awareness , which involves tracking and understanding the menstrual cycle, observing cervical mucus, and identifying fertile days to conceive or to prevent pregnancy.
Perimenopause and Menopause
Perimenopause and menopause are two distinct but interconnected stages of reproductive aging. The transitional period leading up to menopause, during which a person's body undergoes hormonal fluctuations and reproductive changes, is perimenopause . It is characterized by irregular menstrual cycles and a decline in ovarian function leading to decreased estrogen , progesterone , and testosterone . Perimenopause usually begins 4 to 9 years prior to menopause and affects most persons AFAB in their mid-40s (Leistikow & Smith, 2022).
During perimenopause, hormones fluctuate significantly. These hormonal shifts can lead to various symptoms, including irregular periods, hot flashes, night sweats, mood swings, fatigue, sleep disturbances, vaginal dryness, changes in libido, and cognitive changes. Perimenopause has been compared to the peripartum period, in which risk of depression and mental illness is greatly increased; health-care providers and nurses must screen for perimenopausal depression as they do during the postpartum period (Leistikow & Smith, 2022). In one study, perimenopausal people had a 9 percent to 15 percent increase in dysmorphic mood and were two to four times more prone to major depressive episodes than premenopausal people (Leistikow & Smith, 2022).
The permanent cessation of ovarian function, signaling the end of reproductive capability, is menopause . It is a natural physiologic process that occurs due to the depletion of ovarian follicles and the subsequent decline in estrogen and progesterone production.
Following menopause, people may continue to experience a range of physical and emotional changes. Common symptoms include hot flashes, night sweats, vaginal dryness, mood swings, sleep disturbances, urinary changes, changes in sexual function, and changes in bone density (Leistikow & Smith, 2022).
Nurses can encourage patients to explore resources on hot flashes, hormone therapy, vaginal dryness, and sleep problems from menopause.org.
Individual experiences through perimenopause and menopause differ, with some experiencing minimal symptoms and others requiring medical interventions to manage symptoms and prevent or treat adverse health conditions. Managing perimenopause and menopause involves a multidimensional approach, including self-care practices, menopausal hormone therapy (MHT), nonhormonal medications, and complementary therapies. MHT can begin during perimenopause and is the gold standard for treatment, reducing morbidity and mortality in women. Nurses and health-care providers play a crucial role in assessing symptoms, addressing concerns, providing guidance, and tailoring treatment plans to support overall health and well-being during this transitional phase. Nurses can encourage patients to see a Menopause Society Certified Practitioner for specialized menopausal care.
Sexual Response
The sexual response is a complex physiologic and psychologic process encompassing several stages. The most recognized model of sexual response is the four-stage model proposed by Masters and Johnson in the 1960s. This model consists of four phases: excitement, plateau, orgasm, and resolution (Masters & Johnson, 1966). However, it is important to note that individual experiences of sexual response can vary.
In the excitement phase , sexual desire and arousal begin in response to sexual stimuli, such as physical touch, erotic thoughts, or visual cues. Physiologic changes occur, including increased blood flow to the genital area, vaginal lubrication, and swelling of the clitoris and labia. Breathing and heart rate may increase, and nipples can become erect.
During the plateau phase , a heightened state of arousal and sexual tension continues to build. The body prepares for a potential orgasm, with increased muscle tension and blood flow to the genital area. Vaginal lubrication increases further, and the clitoris becomes more sensitive.
 Rhythmic contractions occur in the pelvic muscles, including the uterus, vagina, and anal sphincter. Intense pleasure and release of endorphins are experienced. The resolution phase refers to the return to baseline where muscles are relaxed and pulse, blood pressure, and respirations return to normal.
It is essential to recognize that sexual response is a diverse and individual experience. Some individuals may experience variations in the stages or have different patterns of sexual response. In addition to providing information about the sexual response, nurses are prepared to discuss the importance of open communication, consent, and the person's desires and boundaries in sexual experiences. Nurses should also encourage patients to discuss problems with sexual response, such as difficulty in achieving orgasm. When nurses ask questions about difficulty with the sexual response, patients are more at ease and open to discuss sexual issues.
  Assessing the underlying causes, providing education, and referring to appropriate specialists, such as gynecologists or sex therapists, may be necessary.
Self-Care Practices and Supportive Nursing Actions
Self-care is an essential aspect of maintaining optimal health and well-being throughout life. It involves deliberate practices and behaviors supporting physical, mental, and emotional well-being. By prioritizing self-care , people can promote expected growth and development and prevent or delay the onset of various diseases and health complications. They can empower themselves with the tools to prevent diseases and maintain their overall well-being proactively.
Nurses play an important role in self-care counseling and education, as they are often at the forefront of patient care and frequently interact with people across various health-care settings. Nurses assess patients' self-care behaviors, such as diet, physical activity, sleep patterns, stress levels, and substance use . This information helps identify areas where self-care modifications may be beneficial and form the basis for personalized counseling and education.
Nutrition
Throughout the lifespan, good nutrition is crucial to health, vitality, and overall well-being. From childhood to the later stages of life, adequate and balanced nutrition is essential for optimal growth, development, disease prevention, and maintaining a healthy body.
As persons AFAB enter their reproductive years, nutrition plays a critical role. For those planning to conceive, proper nutrition supports fertility and reproductive health. A well-balanced diet, including various nutrients, vitamins, and minerals, ensures optimal hormone regulation and menstrual regularity. Reproductive persons AFAB should be encouraged to take a folic acid supplement because of its importance in preventing neural tube defect s. During pregnancy, adequate nutrition becomes paramount to support the growing fetus. It provides the essential nutrients needed for fetal development, reduces the risk of birth complications, and promotes the health of the pregnant person and fetus. Proper nutrition also plays a crucial role during lactation, providing the necessary nutrients for breast-feeding and supporting the birthing person’s and infant’s health.
As individuals transition into perimenopause and menopause, nutrition remains of utmost importance. The risk of osteoporosis increases during this stage, making adequate calcium and vitamin D intake crucial for maintaining bone health and reducing fractures. A heart-healthy diet low in saturated fats and high in fruits, vegetables, whole grains, fiber, and healthy fats helps reduce the risk of cardiovascular diseases that can become more prevalent during this time. Adequate nutrient intake is essential for maintaining energy levels, cognitive function, and a strong immune system. Nutrient-dense foods provide the necessary vitamins, minerals, and antioxidants to support cellular health and combat age-related oxidative stress.
Calcium
Calcium is an essential mineral that is vital in maintaining strong bones and teeth and supporting various bodily functions. It is advisable to obtain calcium from a variety of food sources rather than relying solely on supplements. Good dietary sources of calcium include dairy products (milk, yogurt, cheese), fortified plant-based milk alternatives (soy, almond), green leafy vegetables (broccoli, kale, spinach), canned fish with bones (such as salmon or sardines), tofu, and calcium-fortified foods (cereals, bread, orange juice).
- Generic Name: calcium carbonate , calcium gluconate , calcium citrate , calcium acetate
- Trade Name: TUMS , Eliphos , PhosLo
- Class/Action: mineral, antacid
- Route/Dosage: oral
The recommended daily calcium intake varies based on age, sex, and life stage. The following are general guidelines for calcium intake:
- Adolescents (9 to 18 years): 1,300 mg per day
- Adults (19 to 50 years): 1,000 mg per day
- Persons AFAB (51 to 70 years): 1,200 mg per day
- Older adults (71 years and older): 1,200 mg per day
It is important to note that during pregnancy and breast-feeding, calcium requirements increase to support the growing fetus's development. The recommended daily intake for pregnant and breast-feeding people is 1,000-1,300 mg per day, depending on age.
- High Alert/Black Box Warning: none
- Indications: dyspepsia, osteoporosis prevention, hypocalcemia
- Mechanism of Action: neutralizes esophageal or gastric acidity; essential component in physiologic systems and reactions
- Contraindications: hypersensitivity to calcium, hypercalcemia, dehydration, renal impairment, gastrointestinal (GI) bleeding, hyperparathyroidism
- Adverse Reactions/Side Effects: hypercalcemia, nephrolithiasis, milk-alkali syndrome, constipation, nausea, hypomagnesemia
- Nursing Implications: Encourage dose for age and stage of reproductive life.
- Parent/Family Education: The nurse will provide education to avoid foods high in iron when taking calcium; avoid taking calcium when taking a multivitamin; coffee and cigarettes should be avoided, as they impede absorption; take calcium in the morning 1 hour after breakfast with plenty of water.
(Mayo Clinic, 2022)
The most recent dietary guidelines available are the Dietary Guidelines for Americans 2020–2025, published jointly by the U.S. Department of Agriculture ( USDA ) and the U.S. Department of Health and Human Services (HHS) (2020). These guidelines provide evidence-based recommendations for healthy eating patterns to promote overall health and prevent chronic diseases.
The full Dietary Guidelines for Americans 2020–2025 provide detailed recommendations and specific guidance for different age groups, including children, adolescents, adults, and older adults.
In addition to educating patients about good nutrition habits, it is important to understand common unhealthy nutrition practices. Unhealthy nutrition practices refer to behaviors and dietary habits that negatively affect a person's health and well-being. Unhealthy nutrition practices can have both immediate and long-term consequences for health. They can contribute to obesity, diabetes , heart disease , hypertension , certain cancers, and other chronic health conditions. Additionally, poor nutrition can lead to fatigue, weakened immune function, and impaired cognitive abilities.
Disordered Eating
The term disordered eating is commonly used to describe maladaptive nutritional practices that are not severe enough to meet the diagnostic criteria for a specific eating disorder but still involve problematic attitudes and behaviors toward food and eating. Disordered eating can encompass a range of unhealthy eating patterns, including restrictive eating, binge eating, compulsive overeating, emotional overeating, yo-yo dieting, and chronic dieting.
Overeating and Obesity
Obesity in persons AFAB is a significant public health concern with far-reaching consequences for physical and mental well-being. The Centers for Disease Control and Prevention (2019) defines an adult as obese if they have a body mass index (BMI) of 30 or higher (Table 3.11). BMI can be a helpful tool but does not consider body composition and is not always an accurate determination of overweight or obesity .
| BMI | Weight Status |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25.0–29.9 | Overweight |
| 30.0 and above | Obese |
Obesity is a major risk factor for chronic conditions such as cardiovascular disease, type 2 diabetes, hypertension, dyslipidemia, certain types of cancer (including breast and uterine), and respiratory disorders. These conditions can profoundly affect the health and quality of life of persons and their offspring. Several factors contribute to obesity, including genetics, hormonal factors, sedentary lifestyle, unhealthy dietary habits, socioeconomic status, and psychosocial factors (CDC, 2022b). Nurses should be able to approach obesity from a holistic perspective, focusing on a comprehensive approach to prevention and management.
Obesity can have significant impacts on reproductive health. It increases the risk of infertility, polycystic ovary syndrome ( PCOS ), irregular menstrual cycle s, and complications during pregnancy, including gestational diabetes , preeclampsia, and cesarean delivery (Silvestris et al., 2018). Obesity can also affect fetal health and increase the risk of birth defects. Nurses play a role in educating the patient on the potential consequences of obesity as well as measures to prevent obesity or to return to a healthy weight.
Obesity can limit physical mobility and decrease overall quality of life due to reduced fitness levels, decreased energy, joint pain, and limitations in activities of daily living. Obesity also places a significant burden on health-care systems because of the increased risk of chronic diseases and related health-care utilization. This burden includes costs associated with medical visits, hospitalizations, medications, and management of comorbid conditions.
Eating Disorders
An eating disorder , unlike disordered eating, is a serious mental health condition characterized by abnormal eating patterns, attitudes, and behaviors toward food and weight. Eating disorders often involve a preoccupation with food, weight, body shape, and a distorted perception of one's body image. They can have severe physical, psychologic, and social consequences. There are several types of eating disorders, including:
- Anorexia nervosa : Anorexia is characterized by extreme restriction of food intake, an intense fear of gaining weight or becoming fat, and a distorted body image. Persons with anorexia may have significantly low body weight and engage in behaviors to control their weight, such as excessive exercise, strict dieting, or purging.
- Bulimia nervosa : Bulimia involves recurrent episodes of binge eating, followed by compensatory behaviors to prevent weight gain, such as self-induced vomiting, excessive exercise, or the misuse of laxatives or diuretics. People with bulimia may have normal body weight or fluctuating weight.
- Binge eating disorder (BED): BED is characterized by recurrent episodes of uncontrollable binge eating, often accompanied by feelings of guilt, shame, and distress. Unlike those with bulimia, persons with BED do not engage in compensatory behaviors to counteract the binge episodes, which can lead to weight gain and obesity.
- Avoidant/restrictive food intake disorder (ARFID) : ARFID is characterized by the avoidance or restriction of food due to sensory sensitivity, fear of negative consequences (e.g., choking), or an apparent lack of interest in eating. This disorder can lead to significant nutritional deficiencies and impaired growth and development.
- Other specified feeding or eating disorders (OSFED) : OSFED, previously known as Eating Disorder Not Otherwise Specified (EDNOS), encompasses a range of eating disorders that do not meet the full diagnostic criteria for anorexia, bulimia, or BED. These disorders include atypical anorexia, purging disorder, and night eating syndrome.
(Mayo Clinic, 2023)
Eating disorders require professional diagnosis and treatment, often involving a multidisciplinary approach that includes medical, nutritional, and psychologic interventions. Nurses should be prepared to screen for and recognize eating disorders. In addition, the nurse provides intervention and support, which are crucial for persons struggling with eating disorders.
Exercise
A sedentary lifestyle, characterized by little to no physical activity and prolonged periods of sitting or lying down, can have numerous negative consequences on physical and mental health. Consequences of a sedentary lifestyle include obesity and weight gain, increased risk of heart disease, reduced bone density, insulin resistance, increased risk of some cancers, and reduced overall well-being. Physical activity plays a crucial role in promoting overall well-being especially for persons AFAB. Regular aerobic exercise, such as brisk walking, jogging, cycling, or swimming, helps strengthen the heart and improve cardiovascular health (Figure 3.11).
Physical activity supports weight management and helps prevent weight gain. Regular exercise, combined with a balanced diet, assists in maintaining healthy body weight and reducing the risk of obesity. Weight-bearing exercises like walking, jogging, dancing, or weightlifting also help build and maintain bone density, reducing the risk of osteoporosis and fractures.
Exercise improves mental health and well-being by stimulating the release of endorphins, neurotransmitters that promote positive mood and reduce stress and anxiety. Exercise can positively impact hormonal balance to regulate menstrual cycles, reduce premenstrual syndrome (PMS) symptoms, and improve symptoms associated with menopause (Basile, 2020). Nurses are well trained to provide education, encouragement, and support of physical activity for all ages.
Sleep and Rest
Rest is of utmost importance for overall health and well-being. It is an essential physiologic and psychologic process that allows the body and mind to recover, rejuvenate, and perform optimally. Establishing healthy sleep patterns is important for overall well-being and especially important during hormonal changes, pregnancy, menopause, and certain health conditions.
Hormonal fluctuations during pregnancy, perimenopause , and menopause can disrupt sleep. Pregnant people often experience sleep disruptions due to physical discomfort, frequent urination, hormonal changes, and fetal movement. As pregnancy progresses, finding a comfortable sleep position can become challenging. Sleep disturbances increase as people age, and 50 percent of persons over age 65 have issues with sleep (Haufe & Leeners, 2023). Perimenopause and menopause can cause hot flashes and night sweats, leading to night awakenings and difficulty in falling back to asleep. Hormonal changes can also contribute to insomnia , mood changes, and sleep-disordered breathing.
Certain sleep disorders are more prevalent in persons AFAB, for example, insomnia, restless legs syndrome (RLS), and sleep apnea . Chronic diseases such as diabetes, obesity , cardiovascular disease, and depression can be caused or exacerbated by insufficient sleep (CDC, 2022b). Persons AFAB often juggle multiple roles and responsibilities, contributing to sleep disturbances. Stress, caregiving duties, work-life balance challenges, and demands of family life can affect sleep patterns.
Nurses are well trained to evaluate sleeping patterns and to intervene with sleep hygiene counseling. The following is a key point to recommend for good sleep hygiene:
Establish a consistent sleep schedule by going to bed and waking up at the same time every day, including weekends. An established sleep cycle helps regulate the body's internal clock and improves sleep quality.
Sexuality
Sexuality is a fundamental aspect of a person’s overall well-being, and it is essential that providers of health care address the various issues that can arise. Due to time constraints and discomfort, discussions about sexual health are often neglected, and health-care providers may shy away from initiating conversations about sexual concerns, leaving patients to struggle in silence. Nurses must create a safe, nonjudgmental environment that encourages open dialogue about sexual health.
 This knowledge gap can lead to misinformation, fear, and risky sexual behaviors. Providers of health care and nurses play a key role in discussing contraception options, including hormonal methods (e.g., oral contraceptives, contraceptive injections, patches, implant), intrauterine devices (IUDs), barrier methods (e.g., condoms), and fertility awareness -based methods. Counseling should involve a discussion of effectiveness, side effects, potential interactions with other medications, and considerations based on individual needs and preferences.
Health-care providers can address issues related to menstruation, such as irregular periods, heavy bleeding ( menorrhagia ), painful periods ( dysmenorrhea ), or premenstrual syndrome (PMS). Assessing and managing these concerns can improve a person's quality of life and overall sexual well-being.
Providing a safe and inclusive environment for LGBTQIA+ persons is essential. Health-care providers should know the unique health-care needs of lesbian, bisexual, and transgender persons and offer nonjudgmental support, appropriate screenings, and referrals as needed. A more detailed discussion of this topic is found in Chapter 2 Culturally Competent Nursing Care.
Immunizations
Immunizations are essential tools in public health that play a crucial role in preventing and controlling infectious disease s. Immunizations have significantly impacted global health and saved millions of lives. The timing of immunization s throughout the lifespan varies depending on the person’s age, health status, and specific risk factors. The CDC publishes a recommended immunization schedule on their website.
The CDC (2023h) recommends that all adults receive the COVID-19 and influenza vaccine yearly. They recommended that adults ensure they are up to date on the Tdap or Td vaccines as well. Table 3.12 presents recommendations for adult vaccines.
| Age (years) | Recommended vaccine |
|---|---|
| 19–26 | Chickenpox, COVID-19, influenza, hepatitis B, HPV, measles-mumps-rubella (MMR), and tetanus-diphtheria-whooping cough (Tdap), meningococcal |
| 27–49 | COVID-19, influenza, hepatitis B, MMR, Tdap, chickenpox, HPV |
| 50–64 | COVID-19, influenza, shingles, Tdap, hepatitis B, MMR, respiratory syncytial virus (RSV) |
| 65 and older | COVID-19, influenza, pneumococcal, shingles, Tdap, RSV |
The CDC also recommends immunizations for patients with certain health conditions, such as diabetes, cardiovascular disease, HIV, lung disease, renal disease, and weakened immune systems (2023h).
General Hygiene
General hygiene is an important aspect of education when caring for persons AFAB. Good hygiene practices can help prevent infections, maintain overall health, and promote well-being.
- Encourage people to maintain good personal hygiene habits, including regular bathing or showering, washing hands thoroughly with soap and water, and brushing their teeth at least twice daily. Emphasize the importance of proper hand hygiene to prevent spreading infections, especially before meals and after using the restroom.
- Provide education on proper menstrual hygiene practice s. Menstrual hygiene includes using clean and appropriate menstrual hygiene products (such as sanitary pads, tampons, or menstrual cups) and changing them regularly to prevent bacterial growth and reduce the risk of infections. Encourage persons to maintain cleanliness during menstruation and properly dispose of used menstrual products.
- Educate persons AFAB on maintaining good vulvar hygiene . Emphasize the importance of gentle cleaning with warm water and mild, fragrance-free cleansers. Avoid harsh soaps or douches, as they can disrupt the natural balance of vaginal flora and increase the risk of infections. Encourage wearing clean cotton underwear and changing them regularly and as soon as possible after exercising.
- Encourage the use of sunscreen to protect against harmful ultraviolet (UV) rays.
- Discuss the importance of proper wound care and cleanliness to prevent infections.
 Voiding after sexual intercourse is commonly recommended to reduce the risk of urinary tract infections (UTIs) in persons AFAB. While empirical evidence specific to this practice is limited, several mechanisms and observations support its potential effectiveness.
Nurses should ask about the patient's access to showers, soap, and hygiene products prior to teaching about hygiene. Some patients may lack running water, soap, or money. Nurses can help patients find resources for hygiene.
Mikveh Bath
The Jewish faith requires a mikveh (a ritual bath) during the process of conversion to Judaism, before getting married, and niddah (menstrual purity after the menstrual period or childbirth). The mikveh is a Jewish rite of purification that must be performed after menstruation and childbirth in order to be made pure before sexual activity can resume. Prior to going into the mikveh, Jewish law states that a person must thoroughly cleanse their body, usually by taking a shower, brushing teeth, and clipping nails. A blessing is recited either before or during the immersion (Wenger, 2021).
Self-Esteem and Empowerment
The subjective evaluation of one's worth and capabilities is one’s self-esteem . It is the degree to which a person believes in their value, abilities, and self-worth. Various factors, including personal achievements, social interactions, upbringing, and external validation, can influence self-esteem. There are key aspects of self-esteem that are important to recognize (Table 3.13).
| Key Element | Meaning |
|---|---|
| Self-worth | Feeling worthy of respect and love, irrespective of achievements or failures |
| Self-confidence | Having faith in one's abilities and feeling capable of handling life's challenges |
| Self-acceptance | Embracing oneself, including strengths and weaknesses, without harsh self-judgment |
| Self-respect | Treating oneself with kindness and not tolerating self-destructive behaviors |
Having a healthy level of self-esteem is essential for several aspects of life. Self-esteem contributes to lower levels of anxiety, depression, and stress. Healthy self-esteem enables more positive and fulfilling relationships with others. Those with higher self-esteem are more likely to set and pursue ambitious goals. Healthy self-esteem fosters the ability to bounce back from setbacks and learn from failures.
Having a healthy level of empowerment is essential for several aspects of life, and as with self-esteem, there are key elements of empowerment (Table 3.14). Empowerment fosters personal development and self-awareness. Empowered people can be catalysts for positive social change and collective empowerment. In addition, empowering communities can lead to greater resilience and problem-solving abilities.
| Key Element | Meaning |
|---|---|
| Knowledge and Information | Access to education and information empowers individuals to make informed choices. |
| Autonomy and Agency | Feeling in control of one's life and having the power to make decisions. |
| Advocacy and Support | Encouraging and supporting individuals to stand up for their rights and interests. |
| Equality and Inclusivity | Empowerment promotes equal opportunities for all, regardless of gender, race, or background. |
People with low self-esteem have negative self-perceptions and may feel unworthy or inadequate. Having low self-esteem can lead to behaviors that are problematic, such as violence, and progress to mental health issues (Auttama et al., 2021). Those with low self-esteem can experience depression, stress, and anxiety that can eventually lead to suicide (Auttama et al., 2021). They are more likely to become targets for bullies, as bullies often prey on those they perceive as vulnerable. Nurses need to be vigilant in recognizing signs of bullying, such as unexplained injuries, changes in behavior, or emotional distress. Nurses can make sure that health-care settings are safe and non-threatening by providing a private space for the patient to talk and ensuring confidentiality.
Nurses can help teach self-care and positive mental health behaviors that can lead to increased self-esteem. Research has shown that self-care behaviors for mental health allow patients to deal with stress and anxiety, making them more resilient in dealing with life’s difficulties (Auttama et al., 2021). Empowered individuals can make positive changes. Promoting empowerment includes teaching assertiveness, building resilience, and encouraging a supportive network of friends and family.
Mental Health Hygiene
Addressing mental health hygiene when providing health care is crucial for promoting overall well-being. It is essential to approach mental health hygiene holistically and individually, considering each person's unique circumstances, cultural background, and specific mental health needs.
Nurses can provide education about mental health and common mental health condition s such as anxiety , depression , and stress. Raising awareness reduces stigma and encourages people to seek support when needed. Encourage them to prioritize self-care activities that promote mental well-being. Self-care practices include engaging in regular physical exercise, practicing relaxation techniques (such as deep breathing, meditation, or mindfulness), maintaining a balanced diet, getting adequate sleep, and pursuing activities that bring joy and fulfillment.
Substance Use
Substance misuse in persons AFAB is a significant public health concern with unique considerations and consequences. The problematic use of alcohol or drugs that leads to adverse physical, psychologic, social, and functional outcomes is considered substance misuse . Substance misuse rates in persons AFAB have steadily risen in recent years, with an increasing number of persons engaging in harmful alcohol and drug use. While persons AMAB historically had higher rates of substance misuse, the gender gap has been narrowing (Fonseca et al., 2021).
Persons AFAB experience the effects of substances differently due to brain structure, metabolism, and endocrine function (McHugh et al., 2019). Factors such as body size, composition, metabolism, and the menstrual cycle can influence how substances are processed and their impact on the body. Persons AFAB may face unique risk factors for substance misuse, including a history of trauma (such as physical or sexual abuse), co-occurring mental health disorders (like depression or anxiety), and social or cultural influences contributing to substance use . They may use substances to cope with stress, trauma, or mental health issues. Societal and cultural factors, including gender roles and expectations, can influence substance use patterns in people.
Substance misuse can have specific health effects on persons AFAB. Persons AFAB metabolize alcohol differently than persons AMAB leading to higher blood alcohol levels in those AFAB (McHugh et al., 2019). Persons AFAB also have more side effects of chronic substance use as seen by changes in brain volume (McHugh et al., 2019). These patients also have higher impairment in functioning such as medical, social, family, employment, and psychiatric functions compared to those AMAB (McHugh et al., 2019). Substance misuse during pregnancy can lead to adverse outcomes for the pregnant person and fetus.
Persons AFAB may also face unique barriers to seeking help for substance misuse, such as stigma, concerns about child custody, fear of judgment, or limited access to gender-specific treatment programs and resources. In addition, substance misuse often co-occurs with mental health disorders. Depression, anxiety, and posttraumatic stress disorder (PTSD) can contribute to developing or exacerbating substance misuse issues (McHugh et al., 2019).
Addressing substance misuse in persons AFAB requires a comprehensive and gender-responsive approach. Nurses play a vital role in screening, prevention, early intervention, and referral to specialized treatment services. It is essential to provide tailored and culturally sensitive care that addresses the unique needs and experiences of those struggling with substance misuse.
Nurse
: Alexis, RN
Years in practice:
5+
Clinical setting:
rehabilitation facility
Geographic location:
Dallas, Texas
I really love working with patients in rehab. I am able to provide education, empathy, and kindness to my patients. I am able to spend time with them and get to know them because they usually stay for 30 days. Depressed patients are sometimes hard to get to know, but when they let me in, it is really special. I would not want to work in any other area besides psych.
Injury Prevention
Nurses play a vital role in injury prevention across various health-care settings. They are uniquely positioned to identify risk factors, educate patients and communities, and implement interventions to reduce the incidence of injuries. Nurses assess patients for individual risk factors that may increase their vulnerability to injuries. Assessment includes evaluating age, mobility, cognitive status, and underlying health conditions. Falls are a common cause of injury, especially among older adults. Nurses implement fall prevention strategies, such as conducting fall risk assessment s, ensuring a safe environment, and assisting patients with mobility when needed.
Occupational health nurses promote workplace safety by conducting safety training, advocating for safe working conditions, and supporting injury prevention initiatives. Furthermore, nurses monitor and report data on injuries and accidents, contributing to injury surveillance systems that help identify trends and prioritize prevention efforts.
Nurses often engage in community outreach programs to raise awareness about injury prevention and collaborate with local organizations to implement safety initiatives. Nurses are trained to recognize signs of domestic violence and abuse. They can intervene by providing support, resources, and referrals to help break the cycle of violence.
By focusing on injury prevention, nurses can significantly reduce the burden of injuries on individuals, families, and communities. Their expertise and advocacy contribute to creating safer environments and promoting overall well-being for patients and the general population.


3.8: Post-Immunization
If the health professional has administered a vaccine by injection, apply light pressure to the site for several seconds with a dry cotton ball to minimize bleeding. Adhesive bandages or cotton balls with tape are optional but avoid any blood from staining clothing. Clients should be kept under observation for at least 15 minutes after vaccination and preferably 30 minutes when a specific concern is present. Inform client to take oral analgesics such as acetaminophen or ibuprofen as needed for minor adverse reactions following vaccination. Health professionals should remind clients to report any concerns following immunization. The provider can assess the concerns and determine if it is appropriate to report an adverse event following immunization (AEFI).


4.1: Introduction to Two-Player Non-Zero-Sum Games
In this section, we introduce non-zero-sum games. In a non-zero-sum game the players' payoffs no longer need to sum to a constant value. Now it is possible for both players to gain or both players to lose.
What are some properties of a zero-sum game that may no longer hold for a non-zero-sum game? For example, in a zero-sum game is it ever advantageous to inform your opponent of your strategy? Is it advantageous to communicate prior to game play and determine a joint plan of action? Would you still want to minimize your opponents payoff?
Let's build an understanding of non-zero-sum games by looking at an example.
Alice and Bob want to go out to a movie. Bob wants to see an action movie, Alice wants to see a comedy. Both prefer to go to a movie together rather than to go alone. We can represent the situation with the payoff matrix in Table \(4.1.1\):
| Table \(4.1.1\) : Battle of the Sexes | |||
|---|---|---|---|
| Alice | |||
| Action | Comedy | ||
| Bob | Action | \((2, 1)\) | \((-1, -1)\) |
| Comedy | \((-1, -1)\) | \((1, 2)\) |
Explain why this is not a zero-sum game.
In zero-sum games, it is never advantageous to let your opponent know your strategy. Does that property still apply for games like Battle of the Sexes?
Could it be advantageous for a player to announce his or her strategy? Could it be harmful to announce his or her strategy? If possible, describe a scenario in which it would be advantageous to announce a strategy. If possible, describe a scenario in which it would be harmful to announce a strategy.
We might first try to analyze Battle of the Sexes using the same techniques as we used for zero-sum games. For example, we might start as we would in zero-sum games by looking for any equilibrium points.
Since our main goal in analyzing games has been to find equilibrium points, let's find any equilibrium points for Battle of teh Sexes. Are there any strategy pairs where players would not want to switch?
- Hint
-
There are two!
Are the equilibrium points the same (in other words, does each player get the same payoff at each equilibrium point)? Compare this to what must happen for zero-sum games.
Now that we know Battle of the Sexes has two equilibrium points, we should try to find actual strategies for Alice and Bob. Is there a good strategy for each if they play the game only once? What if they repeat the game? Recall that with zero-sum games, if there was an equilibrium, rational players always want to play it, even if the game is repeated. Does that still seem to work here? Also, how might the ability to communicate change what the players do?
Suppose the game is played repeatedly. For example, Alice and Bob have movie night once a month. Suggest a strategy for Alice and for Bob. Feel free to play the game with someone from class. Try a playing several times without communicating about your strategy before each game.
How could communication affect the choice of strategy? Now play several times where you are allowed to communicate about your strategy. Does this change your strategy?
In either case, communicating and not communicating, do you think your strategies for Alice and Bob represent a mixed strategy equilibrium?
In a zero-sum game, if there is a pure strategy equilibrium, then what happens when you repeat a game? If you repeat Battle of the Sexes, does the game always result in an equilibrium pair?
Hopefully, you are beginning to see some of the challenges for analyzing non-zero-sum games. We know there are equilibrium points in Battle of the Sexes, but even rational play may not result in an equilibrium. For the remainder of this section, let's assume that players are not allowed to communicate about strategy prior to play. Such games are called non-cooperative games. Before moving on, let's try to find the maximin strategies for our players using the graphical method, as we did with zero-sum games.
Consider Battle of the Sexes from Bob's point of view. We know that Bob wants to maximize his payoff (that has not changed). So Bob doesn't care what Alice's payoff's are. Write down Bob's payoff matrix.
Recall that the graphical method represents Bob's expected payoff depending on how often he plays each of his options. Sketch the graph associated with Bob's payoff matrix.
The area between the two lines still represents the possible expected values for Bob, depending on how often Alice plays each of her strategies. So as before, the bottom lines represent the least Bob can expect as he varies his strategy. Thus, the point of intersection will represent the biggest of these smallest values (the maximin strategy). Find this point of intersection. How often should Bob play each option? What is his expected payoff?
So no matter what Alice does, Bob can expect that over the long run he wins at least the value you found in Exercise \(4.1.12\). Make sure you understand this before moving on.
Now consider Battle of the Sexes from Alice's point of view. Write down her payoff matrix and use the graphical method to find the probability with which she should play each option and her expected payoff.
Now, from Exercise \(4.1.12\) and Exercise \(4.1.13\) you have the minimum payoff each player should expect. Note that since this is not a zero-sum game, both players can expect a positive payoff. But now we want to see how this pair of mixed strategies really works for the players.
Assume Bob plays the mixed strategy from Exercise \(4.1.12\). Calculate Alice's expected value for each of her pure strategies (\(E_2\)(Comedy) and \(E_2\)(Action)).
Are Alice's expected values equal? If not, which strategy does she prefer when Bob plays the mixed strategy from Exercise \(4.1.12\)? Does Alice want to deviate from her mixed strategy?
Now if Alice plays a pure strategy, does Bob want to change his strategy? So is the mixed strategy pair for Bob and Alice from Exercise \(4.1.12\) and Exercise \(4.1.13\) an equilibrium? In fact, if Bob changes his strategy, how does his expected value compare to the expected value for his mixed strategy?
What goes wrong with the graphical method in the case of a non-zero-sum game?
- Hint
-
Is it important for Alice to consider the minimax strategy? Does Alice have any reason to minimize Bob's payoff?
As we can see by the above example, the methods used to analyze zero-sum games may not be too helpful for non-zero-sum games. Part of the problem is that in solving zero-sum games we take into consideration that one player wants to minimize the payoff to the other player. This is no longer the case. Changing strategies may allow BOTH players to do better. A player no longer has any reason to prevent the other player from doing better.
So we know the mixed strategy won't give us an equilibrium. But suppose we start there. In other words, suppose Bob plans to play the mixed strategy from Exercise \(4.1.12\). Which pure strategy should Alice play? In response, which pure strategy should Bob play? What is the outcome? Do you end up at an equilibrium?
Now suppose Alice plans to play the mixed strategy from Exercise \(4.1.13\). Calculate the expected value for Bob for each of his pure strategies. Which pure strategy does Bob prefer to play? How will Alice respond to Bob's pure strategy? What is the outcome? Do you end up at an equilibrium?
Suppose Bob thinks Alice will try the mixed strategy and Alice thinks Bob will try the mixed strategy. Which pure strategy will each play? What is the outcome? Do you end up at an equilibrium?
Considering Exercise \(4.1.18\), Exercise \(4.1.19\), and Exercise \(4.1.20\), is it in a player's best interest to even consider playing the mixed strategy from Exercise \(4.1.12\) or Exercise \(4.1.13\)?
We've seen the limitations of the graphical method, but what about the expected value method?
Try applying the expected value method to Battle of the Sexes. What mixed strategies do you get? Explain why this method will also not result in an equilibrium. You might want to consider whether it is important for one player to minimize the expected value for the other player.
Now that we have seen how the methods that allowed us to solve zero-sum games don't work for non-zero-sum games, we will need to find new ways to approach non-zero-sum games.


We used Euler circuits to help us solve problems in which we needed a route that started and ended at the same place. In many applications, it is not necessary for the route to end where it began. In other words, we may not be looking at circuits, but trails, like the old Pony Express trail that led from Sacramento, California in the west to St. Joseph, Missouri in the east, never backtracking.
Euler Trails
If we need a trail that visits every edge in a graph, this would be called an
Euler trail
. Since trails are walks that do not repeat edges, an Euler trail visits every edge exactly once.
Example
\(\PageIndex{1}\)
: Recognizing Euler Trails
Use Figure
\(\PageIndex{2}\)
to determine if each series of vertices represents a trail, an Euler trail, both, or neither. Explain your reasoning.
a
→
b
→
e
→
g
→
f
→
c
→
d
→
e
a
→
b
→
e
→
g
→
f
→
c
→
d
→
e
→
b
→
a
→
d
→
g
g
→
d
→
a
→
b
→
e
→
d
→
c
→
f
→
g
→
e
Answer
It is a trail only. It is a trail because it is a walk that doesn’t cover any edges twice, but it is not an Euler trail because it didn’t cover edges
ad
or
dg
.
It is neither. It is not a trail because it visits
ab
and
be
twice. Since it is not a trail, it cannot be an Euler trail.
It is both. It is a trail because it is a walk that doesn’t cover any edges twice, and it is an Euler trail because it visits all the edges.
Your Turn \(\PageIndex{1}\)
Use the figure to determine if each sequence of vertices represents an Euler trail or not. If not, explain why.
1. \(e \rightarrow f \rightarrow b \rightarrow a \rightarrow d \rightarrow c \rightarrow g \rightarrow h \rightarrow e \rightarrow d\)
2. \(d \rightarrow a \rightarrow b \rightarrow f \rightarrow e \rightarrow h \rightarrow g \rightarrow c\)
3. \(d \rightarrow a \rightarrow b \rightarrow e \rightarrow f \rightarrow b \rightarrow e \rightarrow d \rightarrow c \rightarrow g \rightarrow h \rightarrow e\)
The Five Rooms Puzzle
Just as Euler determined that only graphs with vertices of even degree have Euler circuits, he also realized that the only vertices of odd degree in a graph with an Euler trail are the starting and ending vertices. For example, in Figure
\(\PageIndex{3}\)
, Graph
H
has exactly two vertices of odd degree, vertex
g
and vertex
e
. Notice the Euler trail we saw in Exercise 3 of Example
\(\PageIndex{1}\)
began at vertex
g
and ended at vertex
e
.
This is consistent with what we learned about vertices off odd degree when we were studying Euler circuits. We saw that a vertex of odd degree couldn't exist in an Euler circuit as depicted in Figure
\(\PageIndex{3}\)
. If it was a starting vertex, at some point we would leave the vertex and not be able to return without repeating an edge. If it was not a starting vertex, at some point we would return and not be able to leave without repeating an edge. Since the starting and ending vertices in an Euler trail are not the same, the start is a vertex we want to leave without returning, and the end is a vertex we want to return to and never leave. Those two vertices must have odd degree, but the others cannot.
Let’s use the Euler trail theorem to solve a puzzle so you can amaze your friends! This puzzle is called the “Five Rooms Puzzle.” Suppose that you were in a house with five rooms and the exterior. There is a doorway in every shared wall between any two rooms and between any room and the exterior as shown in Figure
\(\PageIndex{5}\)
. Could you find a route through the house that passes through each doorway exactly once?
Let’s represent the puzzle with a graph in which vertices are rooms (or the exterior) and an edge indicates a door between two rooms as shown in Figure
\(\PageIndex{6}\)
.
To pass through each doorway exactly once means that we cross every edge in the graph exactly once. Since we have not been asked to start and end at the same position, but to visit each edge exactly once, we are looking for an Euler trail. Let’s check the degrees of the vertices.
Since there are more than two vertices of odd degree as shown in Figure
\(\PageIndex{7}\)
, the graph of the five rooms puzzle contains no Euler path. Now you can amaze and astonish your friends!
Bridges and Local Bridges
Now that we know which graphs have Euler trails, let’s work on a method to find them. The method we will use involves identifying
bridges
in our graphs. A bridge is an edge which, if removed, increases the number of components in a graph. Bridges are often referred to as cut-edges. In Figure
\(\PageIndex{8}\)
, there are several examples of bridges. Notice that an edge that is not part of a cycle is always a bridge, and an edge that is part of a cycle is never a bridge.
Edges
bf
,
cg
, and
dg
are “bridges”
The graph in Figure
\(\PageIndex{8}\)
is connected, which means it has exactly one component. Each time we remove one of the bridges from the graph the number of components increases by one as shown in Figure
\(\PageIndex{9}\)
. If we remove all three, the resulting graph in Figure 12.157 has four components.
In sociology, bridges are a key part of social network analysis. Sociologists study two kinds of bridges: local bridges and regular bridges. Regular bridges are defined the same in sociology as in graph theory, but they are unusual when studying a large social network because it is very unlikely a group of individuals in a large social network has only one link to the rest of the network. On the other hand, a
local bridge
occurs much more frequently.  If they lose touch, there is no single individual who can pass information between them. In graph theory, a
local bridge
is an edge between two vertices, which, when removed, increases the length of the shortest path between its vertices to more than two edges. In Figure 12.158, a local bridge between vertices
b
and
e
has been removed. As a result, the shortest path between
b
and
e
is
b
→
i
→
j
→
k
→
e
, which is four edges. On the other hand, if edge
ab
were removed, then there are still paths between
a
and
b
that cover only two edges, like
a
→
i
→
b
.
The significance of a local bridge in sociology is that it is the shortest communication route between two groups of people. If the local bridge is removed, the flow of information from one group to another becomes more difficult. Let’s say that vertex
b
is Brielle and vertex
e
is Ella. Now, Brielle is less likely to hear about things like job opportunities, that Ella many know about. This is likely to impact Brielle as well as the friends of Brielle.
Example \(\PageIndex{2}\): Identifying Bridges and Local Bridges
Use the graph of a social network in Figure
\(\PageIndex{11}\)
to answer each question.
Identify any bridges.
If all bridges were removed, how many components would there be in the resulting graph?
Identify one local bridge.
For the local bridge you identified in part 3, identify the shortest path between the vertices of the local bridge if the local bridge were removed.
Answer
The edges
ku, gh
, and
hi
are bridges.
If the bridges were all removed, there would be four components in the resulting graph, {
i
}, {
h
}, {
u
,
v
,
w
,
x
}, and {
a
,
b
,
c
,
d
,
e
,
f
,
g
,
j
,
k
,
m
,
n
,
o
,
p
,
q
,
r
,
s
,
t
} as shown in Figure 12.160.
Three local bridges are
dn, ef
, and
qt
, among others.
If
dn
were removed, the shortest path between
d
and
n
would be
d
→
e
→
f
→
j
→
o
→
m
→
n
.
Your Turn \(\PageIndex{2}\)
How many bridges and local bridges are in a complete graph with three or more vertices? Explain your reasoning.
Video
Bridges and Local Bridges in Graph Theory
Finding an Euler Trail with Fleury’s Algorithm
Now that we are familiar with bridges, we can use a technique called
Fleury’s algorithm
, which is a series of steps, or algorithm, used to find an Euler trail in any graph that has exactly two vertices of odd degree. Here are the steps involved in applying Fleury’s algorithm.
Here are the steps involved in applying Fleury’s algorithm.
Step 1:
Begin at either of the two vertices of odd degree.
Step 2:
Remove an edge between the vertex and any adjacent vertex that is NOT a bridge, unless there is no other choice, making a note of the edge you removed. Repeat this step until all edges are removed.
Step 3:
Write out the Euler trail using the sequence of vertices and edges that you found. For example, if you removed
ab, bc, cd, de
, and
ef
, in that order, then the Euler trail is
a
→
b
→
c
→
d
→
e
→
f
.
Figure
\(\PageIndex{13}\)
shows the steps to find an Euler trail in a graph using Fleury’s algorithm.
The Euler trail that was found in Figure
\(\PageIndex{13}\)
is
t
→
v
→
w
→
u
→
t
→
w
→
y
→
x
→
v
.
Example \(\PageIndex{3}\): Finding an Euler Trail with Fleury’s Algorithm
Use Fleury’s Algorithm to find an Euler trail for Graph
J
in Figure
\(\PageIndex{14}\)
TIP! To avoid errors, count the number of edges in your graph and make sure thatyour Euler trail represents that number of edges.
Your Turn \(\PageIndex{3}\)
Use Graph
L
to fill in the blanks to complete the steps in Fleury’s algorithm.
Figure
\(\PageIndex{18}\)
: Graph
L
The two vertices that can be used as the starting vertex are ____ and
s
.
If
sq
is the first edge removed, the three options for the second edge to be removed are
qr
, ___, and ___; however, ___ cannot be chosen because it is a ________________.
If
qr
is the second edge removed, the next four edges to be removed must be ___, ___, ___, and ___, in that order.
After
qn
is removed, the three options for the next edge to be removed are
no
, ___, and ___, however, ___ cannot be chosen because it is a _____________
If
no
is the next edge removed, the last four edges removed will be ___, ___, ___, and ___, in that order.
The final Euler trail using the answers to parts 1 through 5 is _________________________.
In the previous section, we found Euler circuits using an algorithm that involved joining circuits together into one large circuit. You can also use Fleury’s algorithm to find Euler circuits in any graph with vertices of all even degree. In that case, you can start at any vertex that you would like to use.
Step 1:
Begin at any vertex.
Step 2:
Remove an edge between the vertex and any adjacent vertex that is NOT a bridge, unless there is no other choice, making a note of the edge you removed. Repeat this step until all edges are removed.
Step 3:
Write out the Euler circuit using the sequence of vertices and edges that you found. For example, if you removed
ab, bc, cd, de
, and
ea
, in that order, then the Euler circuit is
a
→
b
→
c
→
d
→
e
→
a
.
Video
Fluery's Algorithm to Find an Euler Circuit
Checkpoint
IMPORTANT! Since a circuit is a closed trail, every Euler circuit is also an Euler trail, but when we say Euler trail in this chapter, we are referring to an open Euler trail that begins and ends at different vertices.
Example \(\PageIndex{4}\): Finding an Euler Circuit or Euler Trail Using Fleury’s Algorithm
Use Fleury’s algorithm to find either an Euler circuit or Euler trail in Graph
G
in Figure
\(\PageIndex{19}\)
.
Figure
\(\PageIndex{19}\)
: Graph
G
Answer
Graph
G
has all vertices of even degree so it has an Euler circuit.
Step 1:
Choose any vertex. We will choose vertex
j
.
Step 2:
Remove one of the four edges that meet at vertex
j
. Since
jn
is a bridge, we must remove either
jh, ji
, or
jk.
We remove
ji
as shown in Figure
\(\PageIndex{20}\)
.
Figure
\(\PageIndex{20}\)
Graph
G
with 1 Edge Removed
Repeat Step 2:
Since
id
is a bridge, we can remove either
ih
or
ik
next. We remove
ih
, and then the only option is to remove
hj
as shown in Figure
\(\PageIndex{21}\)
.
Figure
\(\PageIndex{21}\)
Graph
G
with 3 Edges Removed
Repeat Step 2:
Since
jn
is a bridge, the next edge removed must be
jk
, and then the only option is to remove
ki
followed by
id
as shown in Figure
\(\PageIndex{21}\)
. Even though
id
is a bridge, it can be removed because it is the only option at this point. Figure
\(\PageIndex{22}\)
shows Graph
G
with these additional edges removed.
Figure
\(\PageIndex{22}\)
Graph
G
with 6 Edges Removed
Repeat Step 2:
Choose any one of the edges
db, dc
, or
de
. We remove
dc
as shown in Figure
\(\PageIndex{23}\)
.
Figure
\(\PageIndex{23}\)
Graph
G
with 7 Edges Removed
Repeat Step 2:
Since
co
is a bridge, choose
cb
next. We remove
cb
, then
bd
, and then
de
as shown in Figure
\(\PageIndex{24}\)
.
Figure
\(\PageIndex{24}\)
Graph
G
with 10 Edges Removed
Repeat Step 2:
Next, remove
ec
and
co
. Then choose any of
op, pn
, or
om
. We remove on as shown in Figure
\(\PageIndex{25}\)
.
Figure
\(\PageIndex{26}\)
Graph
G
with 13 Edges Removed
Repeat Step 2:
Next, remove either
nm
,
np
, or
nj
, but
nj
is a So, we remove
nm
as shown in Figure
\(\PageIndex{27}\)
.
Figure
\(\PageIndex{27}\)
Graph
G
with 14 Edges Removed
Repeat Step 2:
Next, remove
mo, op, pn
, and
nj
. And we are done!
Step 3:
Notice that the algorithm brought us back to the vertex where we started, forming an Euler circuit. Write out the Euler circuit:
j
→
i
→
h
→
j
→
k
→
i
→
d
→
c
→
b
→
d
→
e
→
c
→
o
→
n
→
m
→
o
→
p
→
n
→
j
Your Turn \(\PageIndex{4}\)
Find an Euler circuit or trail through the graph using Fleury’s algorithm.
Figure
\(\PageIndex{28}\)
: Graph
T
WORK IT OUT
We have discussed a lot of subtle concepts in this section. Let’s make sure we are all on the same page. Work with a partner to explain why each of the following facts about bridges are true. Support your explanations with definitions and graphs.
When a bridge is removed from a graph, the number of components increases.
A bridge is never part of a circuit.
An edge that is part of a triangle is never a local bridge.
Check Your Understanding
Fill in the blank to make the statement true.
1. An Euler trail is a trail that visits each ___________ exactly once.
2. __________ algorithm is a procedure for finding an Euler trail or circuit.
3. An Euler _____ always begins and ends at the same vertex, but an Euler _____ does not.
4. When a bridge is removed from a graph, the number of ________ is increased by one.
5. When a __________ is removed from a graph, the shortest path between its vertices will be greater than two.
6. When using Fleury’s algorithm to find an Euler trail, never remove a _________ unless it is the only option.


26.10: Protein Structure
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- Steven Farmer, Dietmar Kennepohl, Tim Soderberg, William Reusch, & Ed Vitz
- University of Illinois Springfield
Objectives
After completing this section, you should be able to
- discuss, with reference to a suitable example (either given or of your own choice), the structure of proteins, paying particular attention to distinguishing between the primary, secondary, tertiary and quaternary structure.
- describe the α ‑helical secondary structure displayed by many proteins.
- describe the β ‑pleated‑sheet structure displayed by many proteins.
Key Terms
Make certain that you can define, and use in context, the key terms below.
- α helix
- β pleated sheet
- primary structure
- quaternary structure
- secondary structure
- tertiary structure
Study Notes
Note that in a diagram of the α ‑helical structure of a protein, the C‑terminal of the protein is at the bottom of the diagram and the N‑terminal is at the top. In an α helix, such as the one shown in Figure 26.9.1, the bulky R groups are all found on the outside of the helix, where they have the most room.
The four levels of protein structure
Protein structure can be discussed at four distinct levels. A protein’s primary structure is two-dimensional - simply the sequence of amino acids in the peptide chain. Below is a Lewis structure of a short segment of a protein with the sequence CHEM (cysteine - histidine - glutamate - methionine)
Secondary structure is three-dimensional, but is a local phenomenon, confined to a relatively short stretch of amino acids. For the most part, there are three important elements of secondary structure: helices, beta-sheets, and loops. In a helix, the main chain of the protein adopts the shape of a clockwise spiral staircase, and the side chains point out laterally.
In a beta-sheet (or beta-strand) structure, two sections of protein chain are aligned side-by-side in an extended conformation. The figure below shows two different views of the same beta-sheet: in the left-side view, the two regions of protein chain are differentiated by color.
Loops are relatively disordered segments of protein chain, but often assume a very ordered structure when in contact with a second protein or a smaller organic compound.
Both helix and the beta-sheet structures are held together by very specific hydrogen-bonding interactions between the amide nitrogen on one amino acid and the carbonyl oxygen on another. The hydrogen bonding pattern in a section of a beta-strand is shown below.
Secondary structure refers to the shape of a folding protein due exclusively to hydrogen bonding between its backbone amide and carbonyl groups. Secondary structure does not include bonding between the R-groups of amino acids, hydrophobic interactions, or other interactions associated with tertiary structure. The two most commonly encountered secondary structures of a polypeptide chain are α-helices and beta-pleated sheets. These structures are the first major steps in the folding of a polypeptide chain, and they establish important topological motifs that dictate subsequent tertiary structure and the ultimate function of the protein.
α-Helices
An α-helix is a right-handed coil of amino-acid residues on a polypeptide chain, typically ranging between 4 and 40 residues. This coil is held together by hydrogen bonds between the oxygen of C=O on top coil and the hydrogen of N-H on the bottom coil. Such a hydrogen bond is formed exactly every 4 amino acid residues, and every complete turn of the helix is only 3.6 amino acid residues. This regular pattern gives the α-helix very definite features with regards to the thickness of the coil and the length of each complete turn along the helix axis.
The structural integrity of an α-helix is in part dependent on correct steric configuration.  Proline also destabilizes α-helices because of its irregular geometry; its R-group bonds back to the nitrogen of the amide group, which causes steric hindrance. In addition, the lack of a hydrogen on Proline's nitrogen prevents it from participating in hydrogen bonding.
Another factor affecting α-helix stability is the total dipole moment of the entire helix due to individual dipoles of the C=O groups involved in hydrogen bonding. Stable α-helices typically end with a charged amino acid to neutralize the dipole moment.
BETA-PLEATED SHEETS
This structure occurs when two (or more, e.g. ψ-loop) segments of a polypeptide chain overlap one another and form a row of hydrogen bonds with each other. This can happen in a parallel arrangement:
Or in anti-parallel arrangement:
Parallel and anti-parallel arrangement is the direct consequence of the directionality of the polypeptide chain. In anti-parallel arrangement, the C-terminus end of one segment is on the same side as the N-terminus end of the other segment. In parallel arrangement, the C-terminus end and the N-terminus end are on the same sides for both segments. The "pleat" occurs because of the alternating planes of the peptide bonds between amino acids; the aligned amino and carbonyl group of each opposite segment alternate their orientation from facing towards each other to facing opposite directions.
The parallel arrangement is less stable because the geometry of the individual amino acid molecules forces the hydrogen bonds to occur at an angle, making them longer and thus weaker. Contrarily, in the anti-parallel arrangement the hydrogen bonds are aligned directly opposite each other, making for stronger and more stable bonds.
Commonly, an anti-parallel beta-pleated sheet forms when a polypeptide chain sharply reverses direction. This can occur in the presence of two consecutive proline residues, which create an angled kink in the polypeptide chain and bend it back upon itself. This is not necessary for distant segments of a polypeptide chain to form beta-pleated sheets, but for proximal segments it is a definite requirement. For short distances, the two segments of a beta-pleated sheet are separated by 4+2n amino acid residues, with 4 being the minimum number of residues.
α-PLEATED SHEETS
A similar structure to the beta-pleated sheet is the α-pleated sheet. This structure is energetically less favorable than the beta-pleated sheet, and is fairly uncommon in proteins. An α-pleated sheet is characterized by the alignment of its carbonyl and amino groups; the carbonyl groups are all aligned in one direction, while all the N-H groups are aligned in the opposite direction. The polarization of the amino and carbonyl groups results in a net dipole moment on the α-pleated sheet. The carbonyl side acquires a net negative charge, and the amino side acquires a net positive charge.
A protein’s tertiary structure is the shape in which the entire protein chain folds together in three-dimensional space, and it is this level of structure that provides protein scientists with the most information about a protein’s specific function.
While a protein's secondary and tertiary structure is defined by how the protein chain folds together, quaternary structure is defined by how two or more folded protein chains come together to form a 'superstructure'. Many proteins consist of only one protein chain, or subunit , and thus have no quaternary structure. Many other proteins consist of two identical subunits (these are called homodimers) or two non-identical subunits (these are called heterodimers).
Quaternary structures can be quite elaborate: below we see a protein whose quaternary structure is defined by ten identical subunits arranged in two five-membered rings, forming what can be visualized as a 'double donut' shape (this is fructose 1,6-bisphosphate aldolase):
The molecular forces that hold proteins together
The question of exactly how a protein ‘finds’ its specific folded structure out of the vast number of possible folding patterns is still an active area of research. What is known, however, is that the forces that cause a protein to fold properly and to remain folded are the same basic noncovalent forces that we talked about in chapter 2: ion-ion, ion-dipole, dipole-dipole, hydrogen bonding, and hydrophobic (van der Waals) interactions. One interesting type of hydrophobic interaction is called ‘aromatic stacking’, and occurs when two or more planar aromatic rings on the side chains of phenylalanine, tryptophan, or tyrosine stack together like plates, thus maximizing surface area contact.
Hydrogen bonding networks are extensive within proteins, with both side chain and main chain atoms participating. Ionic interactions often play a role in protein structure, especially on the protein surface, as negatively charged residues such as aspartate interact with positively-charged groups on lysine or arginine.
One of the most important ideas to understand regarding tertiary structure is that a protein, when properly folded, is polar on the surface and nonpolar in the interior . It is the protein's surface that is in contact with water, and therefore the surface must be hydrophilic in order for the whole structure to be soluble. If you examine a three dimensional protein structure you will see many charged side chains (e.g. lysine, arginine, aspartate, glutamate) and hydrogen-bonding side chains (e.g. serine, threonine, glutamine, asparagine) exposed on the surface, in direct contact with water. Inside the protein, out of contact with the surrounding water, there tend to be many more hydrophobic residues such as alanine, valine, phenylalanine, etc. If a protein chain is caused to come unfolded (through exposure to heat, for example, or extremes of pH), it will usually lose its solubility and form solid precipitates, as the hydrophobic residues from the interior come into contact with water. You can see this phenomenon for yourself if you pour a little bit of vinegar (acetic acid) into milk. The solid clumps that form in the milk are proteins that have come unfolded due to the sudden acidification, and precipitated out of solution.
In recent years, scientists have become increasing interested in the proteins of so-called ‘thermophilic’ (heat-loving) microorganisms that thrive in hot water environments such as geothermal hot springs. While the proteins in most organisms (including humans) will rapidly unfold and precipitate out of solution when put in hot water, the proteins of thermophilic microbes remain completely stable, sometimes even in water that is just below the boiling point. In fact, these proteins typically only gain full biological activity when in appropriately hot water - at room-temperature they act is if they are ‘frozen’. Is the chemical structure of these thermostable proteins somehow unique and exotic? As it turns out, the answer to this question is ‘no’: the overall three-dimensional structures of thermostable proteins look very much like those of ‘normal’ proteins. The critical difference seems to be simply that thermostable proteins have more extensive networks of noncovalent interactions, particularly ion-ion interactions on their surface, that provides them with a greater stability to heat. Interestingly, the proteins of ‘psychrophilic’ (cold-loving) microbes isolated from pockets of water in arctic ice show the opposite characteristic: they have far fewer ion-ion interactions, which gives them greater flexibility in cold temperatures but leads to their rapid unfolding in room temperature water.