Module 8 – Nutrition and Fluid Balance
- Demonstrate understanding of good nutrition
- Demonstrate understanding of therapeutic diets
- Identify signs of dehydration
- Develop working knowledge of intake and output measurement
- Demonstrate understanding of alternative feeding methods
Nutrition and Diet
Resident Rights
A person’s diet is important to their overall wellbeing and physical health. It is also important for mental wellbeing and cognitive function. Because nutrient consumption is so important to a person’s health, NAs should try to make eating as enjoyable and fulfilling an experience for residents as possible. This means that personal, cultural, and social considerations are all at play.
NAs should do what they can to honor a person’s dietary preferences. Not only does this lead to better health outcomes, because people are more likely to want to eat if eating is enjoyable, but it is also an important dimension of person-centered, holistic care. Being able to make choices about what one eats is a moment of agency in circumstances that otherwise may feel disempowering.
Cultural and psychosocial needs
A person must have access to culturally relevant food. If a resident does not have culturally affirming food options available at the facility, discuss with nurses so the facility can acquire some. Culturally affirming food choices for many patients and residents are often not available, despite the fact that having such food as option leads to better health outcomes and is legally required [1] .
Assist the resident in getting the facility to provide culturally appropriate meal options by requesting them from the nurse. Family members can also supply the resident with snacks and drinks that they enjoy.
Religion can also be a barrier to nutrient access in healthcare facilities. Practitioners of religions such as Judaism and Islam may uphold certain dietary restrictions, in this case Kosher and Halal respectively. Many religions involve fasting, or require vegetarianism.
If a hospital or facility does not have food that aligns with a person’s cultural and religious values, they may choose not to eat it. It is the facility and facility staff’s responsibility to create conditions in which anyone can become and remain holistically well, regardless of their cultural background.
In long-term care facilities, mealtimes can be an opportunity for residents to wear clothes they like, sit with their friends (and make new ones), socialize, and share a communal experience. It helps a resident with nutrient consumption, and positively contributes to their overall quality of life, when they enjoy and look forward to meals. NAs should make conversation with the residents during meals, facilitate introductions, and include everybody at the table in conversation.
A resident’s dietary needs will be communicated when they enter the facility, and will be included in their care plan. If you don’t see any information about cultural, religious, or personal food preferences in a resident’s plan, follow up with the nurse.
Nutrition
Nutrition is the process involved in the ingestion, digestion, absorption, and use of foods and fluids by the body. “Good nutrition” is when a person gets a sufficient amount of the right kinds of sustenance from their diet; in other words, they eat a well-balanced diet, their body can absorb what it needs to from the diet, and they consume the correct number of calories. Malnutrition occurs when a person does not absorb enough nutrients, whether because of their diet or a medical condition, and their body is weakened by insufficient sustenance.
Good nutrition is necessary for the body to function. It is also needed for new tissue growth and healing. A well-balanced diet supports immune health, mood and cognitive function, healthy elimination, a healthy circulatory system, and more. Nutrition is a consideration when providing holistic care because it is holistically important.
Insufficient nutrition, overconsumption of processed sugar and cholesterol, and lack of physical activity is linked to cardiovascular disease, diabetes, obesity, and osteoporosis.
Insufficient nutrition can contribute to many different health problems. While good nutrition can bolster the immune system, insufficient nutrition can increase a person’s risk for infection and illness, and make any diseases they are already experiencing worse.
Whereas good nutrition allows a body to heal, insufficient nutrition can drag out a healing process or even inhibit it entirely. While good nutrition is important for cognition and awareness, malnutrition can negatively impact mental functions such as alertness, memory, orientation, decision-making, and mood regulation.
Nutrition in the geriatric population
The geriatric population will have a specific set of dietary needs and considerations.
As a person ages they lose some of their senses of taste and smell, and may find that they have difficulty swallowing due to slowed saliva production. They may also experience a lack of appetite from lowered physical activity levels.
Medications and illness may affect appetite, or the sensory experience of foods. Considering these factors emphasizes the importance of the NA’s role in making eating a positive and enjoyable experience so that residents can continue to meet their nutrient needs.
Nutrients
Nutrients are different substances within foods and beverages that a human body needs to absorb in order to function. There are six basic nutrients: water, fats, carbohydrates, proteins, vitamins, and minerals [2] .
Water
Water is the most important nutrient and is essential for all bodily functions; it is an important part of our blood, keeps our cells healthy, helps our body filter out toxins, and assists in digesting food and absorbing nutrients. A person cannot live without consuming water, and would die after only a few days without it. Water is key to all bodily systems and functions.
Fats
Fats are an important part of a balanced diet, and come in four varieties. There are saturated and trans fats, of which the body requires only a very small amount, and which can increase cholesterol levels and the risk of cardiovascular disease if over-consumed. Monounsaturated fats and polyunsaturated fats, by contrast, are necessary in the diet and decrease the risk of heart disease and diabetes. Some sources of essential healthy fats are avocado, nuts and seeds, olives, and fish.
Carbohydrates
Carbs are the body’s primary source of energy, and are necessary for the body to metabolize other forms of nutrients. Carbohydrates such as whole grains and certain fruits and vegetables like corn and mango also contain fiber, which is important to healthy digestion and solid waste elimination.
Protein
Proteins are important for the body’s tissue growth and repair, and are a substantial source of energy. Proteins are also important for blood health. Good sources of protein can be found in nuts, beans, seeds, peas, some grains such as quinoa, eggs, fish, and fowl.
Vitamins
Vitamins are essential substances that perform a variety of different functions, including the health of our immune system, supporting cognitive function, bone strength, the health of our mouths and teeth, and much more.
The body cannot produce most vitamins, and many vitamins can only be properly absorbed when eaten in the right amounts and in conjunction with other vitamins and nutrients. Some vitamins are fat-soluble, which means they can be stored in the body’s fat tissue and used at a later time. Water-soluble vitamins are broken down by water and then any excess water-soluble vitamins are passed when the body eliminates.
Minerals
Minerals, like vitamins, cannot be produced by the body and must be acquired from outside sources in one’s diet. Examples of minerals are zinc, sodium, and other electrolytes necessary to balance our blood. Minerals perform a variety of different functions in the human body from fluid balance and regulating blood levels to bone strength to energy levels.
USDA MyPlate
The US Department of Agriculture (USDA) developed the “MyPlate” system to help people determine what goes into a balanced diet for their age demographic. The USDA MyPlate icon is a visual representation of what a “healthy” plate looks like, in terms of the breakdown between fruits, grains, vegetables, proteins, and dairy [3] .
Some nutrition tips from myplate.gov geared towards older adult from plate are to eat a protein-rich diet to help maintain muscle mass and density, include fruits and vegetables as snacks between meals, and to eat plenty of protein and B12 fortified foods since the body’s ability to absorb this necessary vitamin lessens with age.
The USDA MyPlate system divides a “healthy” plate into five basic food groups and visually represents them so that one half of a plate is made up of fruits and vegetables, the other half is made up of grains and proteins, and dairy is represented on a small plate to the side. It is a set of recommended dietary guidelines published by the US Department of Agriculture so the public can stay up to date on changes in our scientific understanding of nutrition and health.
USDA myplate. (n.d.). Retrieved May 24, 2023, from https://www.myplate.gov/
- Fruits and vegetables are an essential food group. An abundance of leafy greens, dark green, red, and orange vegetables and fruit is especially important because of their high vitamin and mineral content. The fruit and vegetable category includes all fresh, frozen, or dehydrated fruits and vegetables, including 100 percent juice. NAs should encourage residents to eat a wide variety of fruits and vegetables every day for their beneficial nutrients and fiber.
- Grains make up a little over a quarter of the MyPlate and are foods like rice, oats, and wheat. Many foods are made using grains including pastas, cereal, bread, tortillas, and various doughs. Grains are either considered “whole” or “refined.” When a grain is refined, its outer layers are removed and only the inside of the flowering plant remains. A whole grain is one where literally the whole grain is present; its outer layers remain, which makes whole grains more nutrient dense and rich in fiber.
- Protein is slightly less than one quarter of the MyPlate. Proteins come from plant-based sources, such as legumes, soy products like tofu and tempeh, and peas. Protein is also concentrated in animal products like seafood, eggs, poultry, lean meat and red meat. If consuming animal proteins, older adults should make sure to include sea food regularly in their diet because it has fewer health detriments than red meat, and is an important source of healthy fats.
- Dairy makes up the smallest portion on the MyPlate visualization. Dairy includes any foods made from animal milk, such as yogurt and cheese. Dairy can provide important nutrients for the body, such as vitamin D and protein. Products made from soy, nuts, and oats are healthier alternatives to dairy, especially when fortified with vitamins.
Therapeutic Diets
It is the whole care team’s responsibility to make sure that the person being cared for has their nutritional needs met. This will especially involve the nursing team, doctor, dietitian, speech-language pathologist, occupational therapist, and potentially the person’s family. Sometimes a special therapeutic diet will be necessary to meet the person’s nutritional needs, or to work with a resident’s dysphagia.
Special diets are ordered for people who require a certain nutrient profile to achieve their care goals. Only a doctor can prescribe a therapeutic diet, and the special diet is then taken into account by the facility’s dietitians.
NAs must always ID residents before serving them their food, and check the resident’s ID to make sure it corresponds with the card on the meal tray. Serving somebody the incorrect food when they are on a special diet could produce serious health consequences.
Types of therapeutic diets
Doctors prescribe a wide variety of therapeutic diets. Some of these diets are intended to meet a person’s needs around food consistency and swallowing, while other diets are designed to increase or decrease the amount of particular nutrients [4] . Here are some common therapeutic diets it is useful for NAs to know about:
- Liquid diet: Only served liquid food. On a clear liquid diet the liquids are restricted to broths and juices, while on a standard liquid diet a person can have cream-based soups and ice cream.
- Soft diet: Only served foods that are soft and easily swallowed and digested.
- Pureed diet: Only served food that has been pureed into a grainy paste.
- Bland diet: No spicy or acidic foods or other foods that can irritate the digestive system.
- Lactose-free diet: Not served anything containing lactose. Lactose is a protein found in dairy products, and people who lack the ability to process this protein are considered lactose-intolerant. Some kinds of milk will still be allowed, such as lactose-free animal milk, or milk alternatives from soy, rice, oat, and nuts.
- High-fiber diet: An abundance of foods with high fiber, such as whole grains and raw fruits and vegetables. High-fiber diets can help with some digestive disorders and constipation.
- Low-fiber diet: Fiber intake is purposefully decreased by diminishing high-fiber food sources and eliminating foods with laxative properties like coffee and milk.
- Modified calorie diet: Caloric intake is raised or lowered depending on whether they need to gain weight or lose it.
- Low-sodium: Salt intake is restricted. This is an important diet for people suffering from heart or kidney disease. Sodium causes the body to retain water and places a higher workload on the human heart.
- High-protein diet: Prescribed for people who are recovering from wounds or another physical trauma. A person’s protein intake is drastically increased.
- Fluid-restricted diet: Fluid intake is restricted. Be careful not to give a person on a fluid-restricted diet fluid-based foods such as ice cream and soup.
- High-iron diet: Iron intake is increased through foods like dark leafy vegetables, legumes, and iron-enriched whole grains.
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Diabetic diet: Insulin is an enzyme that helps the body convert sugar into energy. If a person’s body does not produce enough insulin, as is the case with people with diabetes, then sugar can clog the blood and cause problems.
- A person who has diabetes must closely monitor all of their nutritional intake, and carbohydrates, fats, and proteins must all be consumed in the proper relative amounts at the right times.
- People with diabetes must avoid high-sugar foods, especially those made with processed and refined sugars.
- NAs must always serve meals exactly on time for someone on a diabetes meal plan. NAs should carefully observe the intake of a person with diabetes to see what was eaten and what was left on the tray and report this information. NAs should also report observed changes in the person’s eating habits.
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Gluten-free diet: Some people cannot process gluten (protein found in wheat and some other grains) due to celiac disease or a gluten intolerance. Gluten is common in wheat products like bread, pasta, and crackers; it can also be found in most beers, and may be used as a filler ingredient in processed foods and beauty items.
- If gluten needs to be eliminated from a person’s diet, they can turn to non-gluten alternative flours made from rice, almonds, oats, and others. The increasing recognition of celiac disease and gluten intolerance means that alternatives to gluten products have been becoming more available.
Gluten Free by Loren Klein from Noun Project ( CCBY3.0 )
- Vegetarian or vegan diet: A person may choose to uphold a vegetarian diet, or it may be prescribed for medical reasons. Vegetarian diets always exclude meat, though a pescatarian diet excludes all meat except seafood. A lacto-ovo vegetarian diet excludes all meat but includes milk and eggs. A lacto-vegetarian allows milk but excludes eggs, while an ovo-vegetarian excludes milk but allows eggs. A vegan diet excludes all animal products. People on vegetarian or vegan diets may need to take iron and B12 supplements.
Dysphagia
People who don’t experience difficulties swallowing may take their ability to swallow easily for granted, but those with difficulties swallowing require special care from the care team. Difficulty swallowing is called dysphagia, and people with dysphagia must be evaluated by a speech-language pathologist to determine the proper course of care [5] .
Thickened liquids
People with dysphagia may be prescribed thickened liquids. This is because regular liquids, such as water and tea, can be difficult to swallow and harder to control by the mouth and throat muscles. Once a person is prescribed thickened liquids, the doctors, nurses, dietitians, and speech-language pathologist work together to determine the proper thickness to make the person’s liquids. Thickened liquids travel slowly down a person’s throat and decrease the risk of choking for people with dysphagia.
Liquids are either pre-thickened or have a thickening agent added to them. Thickened liquids will either come in a nectar consistency (a thick juice), a honey consistency (viscous like honey, pours slowly), or a pudding consistency (does not pour like a liquid – consistency of pudding). NAs must always be patient with people on thickened liquids, since getting through a thickened drink can take much more time than drinking regular water or soda.
NAs should never offer unthickened liquids, such as coffee and tea, to people prescribed thickened liquids. NAs should also remember not to leave a water pitcher in this person’s room.
Signs, symptoms, & strategies
Observe residents when they eat, and report any signs of difficulty swallowing to the nurse immediately. Dysphagia can be extremely dangerous if left unaddressed. If NAs notice any of the following problems while a person eats, they should report it immediately:
- Avoiding eating or eating slowly and with observable difficulty or anxiety
- Spitting food out, or small bites of food and/or pills remaining uneaten
- Saliva dribble
- Vomiting, or food/fluid exiting or entering the nostrils during consumption
- Coughing, choking, and difficulty breathing
- Eyes watering during food or fluid consumption
Difficulties swallowing puts somebody at risk for choking; they must be monitored closely during the eating process. Aspiration refers to the inhalation of food or fluids (including bodily fluids) into a person’s lungs; aspiration can cause serious problems, including choking and pneumonia, and can lead to death. To prevent choking and aspiration, NAs can deploy some of the following strategies:
- Make sure that person is in a 90 degree position sitting upright. A person is more likely to aspirate if they are reclined.
- NAs should be slow and methodical when feeding somebody, alternating between food and drink in small amounts.
- Both the NA and the person eating should focus on eating; distractions increase the likelihood of choking.
- Make sure that the person completely swallows their food before offering more. Check non-invasively – never stick fingers in the person’s mouth.
- Closely observe a person the whole time they are eating. Report signs of difficulty and discomfort immediately in case intervention is necessary.
NAs must always exercise patience, composure, and kindness when helping a person eat. If the person requires assistance and the NA is rushed the person’s emotional wellbeing be compromised and a negative association formed around mealtimes. A rushed NA is a safety hazard, because it increases the likelihood of residents choking and aspiration, and makes the NA less likely to closely observe the person as they eat.
Appetite & Comfort
A person’s appetite is distinct from their need for food. Appetite refers to a person’s desire for food and their drive to consume it, not just the need for nutrients. Many different factors can impact a person’s appetite. These are some factors that can negatively impact a person’s desire to eat:
- Weakness, illness, and confusion or disorientation
- Unpleasant odors, sights, or sounds. Making sure the person’s space is as comfortable as possible helps make eating a pleasant experience.
- Uncomfortable positioning. Make sure the person is physically comfortable and safely positioned when they eat.
- The need for oral hygiene can impact a person’s appetite. If a person finds eating difficult or unpleasant due to sensations in their mouth, NAs can report this to the nurse and alternative mouthcare strategies can be implemented.
- The need to eliminate. Always offer the bathroom before mealtime.
- Pain negatively impacts appetite.
Promoting appetite
NAs can do lots of things to promote general comfort and help make mealtimes an enjoyable experience for residents.
- Always help a resident use the bathroom before and after meals.
- Provide some oral care prior to meals by making sure that the resident’s dentures are fixed in place and free of debris.
- If a person experiences incontinence, make sure they are clean and dry before their mealtime.
- Make sure the person is positioned safely and comfortably for their meal at an upright 90-degree angle at table height. Sometimes tables or wheelchairs will need to be adjusted for a resident to eat comfortably.
- Make sure the resident has any assistive devices they need, such as hand-grips for silverware.
- Give residents as much say in their meal experience as possible. This includes their choices on what and how much to eat, and where and with whom to sit.
- Try to make eating a positive experience for residents, and always conscientiously practice patience. Remain positive and conversational throughout the meal, encourage positive socializing at the table, and assist the person as discretely as they can to ensure the resident’s dignity and sense of independence.
- Assist the resident with handwashing before and after their meal.
When assisting someone with visual impairments, describe the person’s plate of food including the type of food and its location. Always describe what is on the food tray. If the NA is feeding the person, they should describe what is on each bite. If the person is able to feed themselves, describe the food on the whole tray and describe its location using the numbers on the clock. For example, “peas at 9 o’clock, and mashed potatoes at 6 o’clock.”
Dehydration
Fluid balance
Water is essential to survival. Every single part of the human body needs water to function. Human bodies use water, and then get rid of it through sweat and elimination. An adult needs at least 1500 mL (milliliters) of water per day to survive (50 oz, or about 6 glasses of water), but should ideally have between 2000 and 2500 mL of water (about 66 – 83 oz) per day, or about 8 – 10 cups.
As a person ages their awareness of their own thirst can diminish, so NAs may need to prompt residents to drink so they do not become dehydrated.
A person’s daily water requirement can change depending on variables like hot weather, activity levels, illness and fever, fluid loss, medications, and age.
A person’s fluids must be balanced in their body. Dehydration is when a person’s body does not have enough fluid in it. Water retention edema, by contrast, occurs when somebody has too much fluid in their body, a condition in which a person’s body retains too much water.
Water retention edema
Water retention edema can be uncomfortable; symptoms include bloating and increase of size in the abdominal area, swelling and puffiness of the arms and legs, shiny skin, heavy legs, and skin that holds a dimple after being pressed [6] .
If the resident experiences shortness of breath, an irregular heartbeat, or chest pain, it could indicate fluid buildup in the lungs. Edemas can be caused by a number of factors, including being sedentary, consuming too much salt, and taking certain medications. If the NA notices any signs of edema water retention, especially stretched and shiny skin and if the skin holds a dimple after being pressed, then they should report it to the nurse immediately.
Symptoms of dehydration
If fluid output exceeds fluid intake, then dehydration occurs. Remaining properly hydrated is necessary for a person’s health, especially as they age. Peoples’ hydration needs can vary a lot depending on age and activity level, though a general guideline for daily water consumption is about 64 oz [7] .
As people age they become less thirsty, but that doesn’t mean they need less water. Sometimes a doctor will prescribe “force fluids” for a resident, which just means that they should be regularly encouraged to drink. If NAs notices the resident exhibiting signs of dehydration, they should report it immediately.
A resident may be dehydrated if:
- The resident drinks little throughout the day, and doesn’t drink at meals
- The resident has difficulty drinking from cups unassisted, experiences dysphagia, or is disoriented
- The resident frequently expresses being thirsty
- Diminished urine production
- Dry mouth and cracked lips
- Constipation
- Dark and strong-smelling urine
- Feeling weak, dizzy, disoriented, and irritable
Image by OpenStax College, CC BY 3.0
NAs are responsible for making sure residents maintain proper fluid balance. NAs should encourage residents to drink by regularly offering them fluids they like and knowing how residents like to consume fluids (ie, with or without ice, in a specific cup, etc).
Always check the care plan to see whether a person needs their liquids thickened, and always follow the posted schedule for routine fluid consumption. Ice chips and ice sticks can be offered to residents who need fluids but have a difficult time consuming them in large enough quantities in liquid form.
Fluid-restriction
Many people will require encouragement to stay adequately hydrated. However, some medical conditions will require a fluid-restricted diet, or NPO, an acronym for the Latin words for “nothing by mouth.” NPO is the most restrictive kind of fluid-restricted diets.
On a fluid restricted diet, the person will consume few if any liquids by mouth. They can drink, but only up to the point permitted by the doctor’s order.
If the person is prescribed NPO, they cannot consume any liquids and will instead receive their hydration and nutrients through their IV line. A person is put on NPO for a variety of reasons, such as preparing for or recovering from surgery, or another medical test or procedure. A person on NPO is not even permitted chewing gum.
Intake and Output (I&O) Measurement
A doctor or nurse may order that Intake and Output (I&O) measurements be kept on a patient. I&O means that the facility keeps track of all of the fluids that go into a person’s body and all of the fluids that come out. I&O records are kept to help the facility evaluate fluid balance and kidney function, to help plan medical treatment, and when the person has a special fluid order [8] .
When taking intake, NAs should measure all of the fluids the person takes by mouth, as well as any fluids they take in through IV fluids and tube feedings. “Fluids” refers to all liquids, some solids like gelatin, and any food that melts at room temperature.
Output of course refers to urine, as well as vomit, diarrhea (not solid feces), and drainage from wounds. “Fluid balance” is achieved when a person’s intake and output are roughly equivalent.
Recording I&O
An I&O record is a series of tables that a facility uses to track all of a person’s fluid intake and output over 24-hour periods. All I&O measurements are taken in milliliters (mL), which is 1/1000th of a liter. One ounce is equal to thirty milliliters, or 1oz = 30 mL.
NAs must be able to perform conversations between ounces and milliliters (abbreviated as mL or cc), because some fluids may be measured in ounces. For example, if the NA serves a patient 8 ounces of water, and the patient consumed about 6 ounces, then the intake would be recorded as 180 mL (6 x 30 = 180). A helpful tip for making quick mental conversions using the multiplier 30 is to multiply the number by 3 and then add a zero to the end. In the above equation, this would look like 6 x 3 = 18, and then adding the zero so the final answer is 180.
NAs will a tool called a graduate to measure fluids. A graduate looks like a large cup with a handle and a pitcher tip, and will be marked using lines labeled with measurements in milliliters and ounces.
Calculating intake
Intake measurements are taken right after the person is served a meal, snack, or drink. Once the person is finished with their food and/or drink, take note of how much food or drink there was originally – for example, if the resident was served 4 ounces of ice cream and an 8 oz cup of tea, then 12 ounces of fluid was served.
Once the person is finished, gather whatever fluid went unconsumed, measure it, and then subtract that number from the total amount of fluid served. The total fluid minus the remaining fluid will yield the amount of fluid the person has consumed. Or, T (total) – L (leftover) = C (consumed).
1/8th cup=1 oz=30 mL
1/4th cup = 2 oz = 60 mL
½ cup = 4 oz = 120 mL
¾ cup = 6 oz = 180 mL
1 cup = 8 oz = 240 mL
1 ¼ cup = 10 oz = 300 mL
1 ½ cup = 12 oz = 360 mL
2 cup = 16 oz = 480 mL
3 cup = 24 oz = 720 mL
4 cup = 32 oz = 960 mL
So, let’s say that after 4 oz of ice cream and 8 oz of tea were served, the person has 1 oz of ice cream and 2 oz of tea leftover. First, we should put the numbers in milliliters: 1 oz x 30 = 30 mL, and 2 oz x 30 = 60 mL, and 30 + 60 = 90 mL. So 90 mL is the leftover. 12 oz x 30 = 360 mL is the total. So if T – L = the total fluids consumed, then 360 – 90 = 270 mL of fluid consumed.
To properly tally I&O at mealtimes, NAs will need to know the volumetric servings of facility dishware such as cups, bowls, dishes, pitchers, and glasses. For example, usually a cup of water is 8 oz, or 240 mL, while a bowl for cereal and milk will be about 5 oz, or 150 mL. Dish, bowl, and cup volume may vary depending on the facility.
The serving amounts will for the facility dishware will likely be listed on the I&O sheets; if they are not, always follow up with the nurse to make sure I&O records are performed correctly.
Measuring output
To measure output, use a graduate and whatever device the person uses for urinary elimination, such as a handheld urinal, bedpan, or commode. Plastic urinals and basins for collection will likely have mL amounts marked.
Image by Laboratoires Servier, CC BY-SA 3.0 ,
After performing the opening procedure, empty the contents of the person’s voiding device into the graduate, being careful to make sure that no fluid is lost to spillage or splashing.
After carefully remembering the accurate measurement, pour the urine down the toilet, rinse the graduate and the urinal/bedpan and store them to be cleaned, and perform the closing procedure. Finally, record the output amount and the time it was taken.
I&O measurement for each patient is totaled at the end of each shift.
Assisting with feeding [9]
Persons with weakness, paralysis, casts, confusion, and other conditions may require assistance when feeding; this information will be included in their care plan and on the diet card that accompanies their meal tray.
Passing out food
When passing out food, the NA should make sure that residents who can feed themselves safely are helped first, while those who need high levels of assistance should only be given food once the NA can devote full attention to them. If a resident who requires assistance eating attempts to eat on their own, it may put them in an undignified situation or create a choking and aspiration risk.
If a resident requires food to be pureed, NAs should still refer to that food by its actual name, i.e. “steak” or “carrots,” even if the food may look like an indiscriminate mush.
Residents have rights around meals, such as a right to choose what they eat and drink, and a right to choose whether or not to wear a clothing protector.
Food should be served as quickly as possible so that it is appetizing for the resident. Food also must be served and eaten promptly because food that is allowed to sit at room temperature becomes a safety hazard and may induce foodborne illness. Serving food promptly helps minimize the risk of pathogens entering a person’s body through their meal.
Food safety
To keep food safe, people who handle food should wash their hands often, and keep countertops and food preparation sites as clean as possible. Different foods should stay separated to avoid cross-contamination.
Food must always be cooked thoroughly and to a safe internal temperature; if re-heating a dish, it should be re-heated to at least 165 degrees Fahrenheit. Once prepared, food should be refrigerated or frozen with two hours, or within one hour if the room is warm.
Helping someone to eat
When helping a person eat, the NA should give that person their total and full attention. Not paying full attention to a person can result in missing an important sign of difficulties eating.
It is also important from a holistic health perspective; if the NA is constantly distracted or devoting their attention elsewhere, the person needing assistance may feel like a burden, or will be less likely to ask for help when they need it.
Always be patient when assisting somebody with meals. It is a resident’s right to take as much time as they want to with their meal, and not to be rushed.
Even if a person requires substantial assistance with eating, the NA should do everything they can to encourage the person to perform actions independently if possible, such as holding and using a napkin.
Always directly face a resident while the resident is eating. This is so the NA can pay close attention to the resident in case they have any issues chewing or swallowing, and so the resident knows they are attended to and taken care of. Face-to-face contact can put a person at ease, and make them know they are cared for; somebody who is being fed but who needs to communicate something will use their eyes and face, so it is important that the NA is paying close attention and looks directly at the resident.
Chippewa Valley Technical College. (2022, December). Preparing Clients for Meals and Assistance with Feeding. [Video]. YouTube. Video licensed under CC-BY-4.0 .
Nutritional support
If a person can’t eat, or can’t eat enough, then they will require nutritional support and may need IV therapy. Enteral nutrition is the term for supplying a patient with nutrients using a tube that has been inserted into their gastro-intestinal (GI) tract. Gavage is the process that occurs when a person receives a feeding through their tube.
People using feeding tubes will be given formula; the type, amount, and scheduling will be prescribed by the doctor and included in the care plan. Enteral nutrition formula is only given at room temperature; don’t heat or chill it. The nurse will provide scheduled feedings with a syringe, or a feeding bag. If continuous feeding is ordered, the person will receive a steady supply of formula over 24 hours through the use of a feeding pump.
There are different kinds of tubing available depending on how the person needs to be fed.
- Naso-gastric (NG) tube: feeding tube is inserted through the nose, down the esophagus, and into the stomach.
- Naso-enteral tube: feeding tube is inserted through the nose and extends down into the small intestine.
- Gastrostomy tube: the doctor surgically creates an opening into the person’s stomach and inserts the feeding tube directly into the person’s stomach. A gastrostomy is a surgical opening that leads into a person’s stomach.
- Jejunostomy tube: the feeding tube is inserted into a jejunostomy, or a surgical opening at the upper portion of the small intestine.
In Illinois, NAs will never insert feeding tubes, clean feeding tubes, or provide feedings through feeding tubes. They will likely assist the nurse with performing some of these actions though. Always closely follow instructions when assisting the nurse.
NAs will need to be conscious of the tubing when they provide care. Make sure that the area around the tubing is cleaned frequently, and apply lubricant to keep the area free from chapping and dryness. NAs should make sure the tubing is smooth, free of kinks and wrinkles, and securely in place. Always check in to make sure that the person is comfortable and calm.
Complications
Report to the nurse if anything seems wrong with the person or the person’s tubing, such as the tubing having come undone, respiratory difficulty, aspiration, signs of infection at the tube site, or any sources of irritation or discomfort for the person.
Report any irregularities and signs of unwanted side affects immediately. Symptoms of enteral nutrition complications include:
Avoid placing a person using feeding tubes in the left side-lying position. This positioning can lead to an increased risk of regurgitation.
- nausea
- discomfort
- vomiting
- abdominal swelling
- coughing
- complaints of indigestion or heartburn
- fever
- respiratory distress
- increased pulse
- complaints of flatulence
- diarrhea
Nasal feeding tubes can irritate and create pressure on the nose, alter the shape of a person’s nostrils, and create pressure ulcers. NAs should report any irregularities to the nurse as soon as possible.
Aspiration is a major risk when a person is being fed through a tube. Aspiration can occur during the tube insertion, if the tube is moved out of place, or if formula is regurgitated.
NAs can help prevent aspiration by placing the person in Fowler’s or semi-Fowler’s position before they are fed, and maintaining Fowler’s or semi-Fowler’s for a while post-feeding. Always follow the care plan and nurse’s directions when assisting a person who uses feeding tubes.
Parenteral nutrition
Parenteral nutrition is similar to enteral nutrition, except rather than a feeding tube that leads to the person’s GI tract, nutrients will be provided for the person through a catheter inserted directly into a vein. In this case, nutrients never pass through the person’s GI tract at all and instead the nutrient solution is given directly into the person’s bloodstream. This is also called “total parenteral nutrition” or “TPN.” TPN is used when the person cannot receive oral or enteral feedings.
NAs are never responsible for TPN care or performing any of the functions of TPN. The NA’s role with persons who need TPN is to assist with basic needs and ADLs, and to carefully observe the person for any adverse responses to their TPN.
Report any adverse responses to TPN promptly, including:
- fever and chills
- signs of infection
- chest pain
- difficulty breathing
- nausea and vomiting
- diarrhea
- thirst
- irregular heartbeat
- weakness
- sweating
- paleness
- trembling
- disorientation or behavior changes
Patients using an arterial catheter or an IV line are at increased risk for infection, so any signs and symptoms of infection must be responded to quickly.
IV Therapy
IV therapy is the administration of fluids directly into a person’s bloodstream. IV therapy may be ordered for a person when they are unable to drink regularly, for people who need to rapidly replenish vitamins and minerals, to provide sugars, or to give a person blood or drugs.
NAs are not responsible for IV therapy, and should always closely follow the nurse’s instructions when caring for somebody receiving IV therapy.
Intra-venous lines are either peripheral or central. A peripheral IV is located away from the center of the body, such as in a person’s hand or calf. A central IV is located close to the person’s heart.
A central venous line is a kind of catheter than is inserted into a persons chest or upper respiratory area to make IV lines more convenient. They are used when somebody needs IV therapy for a long period of time or frequent blood drawings. Central venous sites are used for parenteral nutrition, providing large amounts of fluid, long-term and repeated IV therapy, and to administer some drugs.
NAs must maintain rigorous safety standards when caring for people receiving IV therapy. NAs should never change the position of the IV clamps or adjust any controls on the IV pumps. If they accidentally bump the machine or nudge the IV out of place, they should record the incident and tell the nurse immediately.
- Tell the RN immediately if no fluid is dripping from a person’s IV line, or if the rate of fluid is too fast or too slow. There will be a “time tape” on the IV bag to display how much fluid should be given over a period of time. If the fluid does not match the time tape, tell the nurse at once.
- NAs will never be responsible for starting or maintaining IV therapy, regulating the IV flow rate, changing the IV bag, or giving blood or drugs through an IV line. Your responsibility will be to clean the area around the IV site and to make the person as comfortable as possible.
- Always ask for help or clarification if you are unsure about how to perform a delegated task, or whether the task falls within your scope of practice.
Key Takeaways
- Good nutrition is key to holistic health. Malnutrition negatively impacts every system in the body, including mental and psycho-social wellbeing. Good nutrition involves absorbing adequate amounts of essential nutrients like water, proteins, fats, vitamins, and minerals.
- Therapeutic diets may be necessary for residents with specific dietary needs or preferences, dysphagia, diabetes, or other conditions. Always check the care plan to see whether a special diet is ordered; when a resident needs a special diet, be especially careful that they only receive food that accords with their diet.
- Our bodies need water to function; dehydration can be an extremely dangerous condition. As a person ages their sense of thirst diminishes, but their need for water does not, which leaves them prone to dehydration. If residents display signs of dehydration, report it to the nurse immediately.
- NAs will need to keep track of fluid intake and output (I&O) for some residents. I&O measurement involves tracking all of the fluids that somebody consumes orally or by IV and tube feeding, and all of the fluids that they release through urinating, vomiting, and diarrhea.
- Residents may require the use of alternative feeding methods when they cannot consume any or enough nutrients using conventional means. Some often used alternative feeding methods include enteral and parenteral nutrition. Enteral nutrition is supplying someone with nutrients through tubing that leads into their gastrointestinal tract. Parenteral nutrition involves supplying someone with nutrients through a direct line into their bloodstream, bypassing the GI tract entirely.
Comprehension Questions
1) If a facility does not have food that meets someone’s culturally relevant preferences or religious diet, the facility should …
a. Ask the resident’s family to supply their meals
b. Suggest that the resident alters their diet so they can remain nourished in their new circumstances
c. Adhere to the resident’s right by procuring culturally or religiously appropriate food
d. Do nothing
2) Malnutrition refers to … (Select the best answer)
a. Consistently eating fewer calories than recommended
b. Absorbing less nutrients is than necessary to remain healthy
c. Drinking too little water and eating too few vitamins and minerals
d. Eating too many unhealthy foods
3) Respond to the following sentences with T (true) or F (false).
____ The six basic nutrients are water, fats, carbohydrates, protein, vitamins, and minerals.
____ A healthy, balanced diet contains more protein than carbohydrates.
____ Fruits, vegetables, and whole grains are good sources of fiber.
____ A human body’s ability to absorb nutrients increases with age.
____ Fortified dairy alternatives from soy, oats, and nuts are healthy alternatives to dairy.
4) What are some signs and symptoms of dysphagia? Select all that apply.
a. Excessive hunger and eagerness to eat
b. Coughing or choking during food or fluid consumption
c. Saliva dribble
d. Pausing in between bits of food
e. Anxiety around or during meal times
5) When providing nutrition assistance to someone with visual impairments, NAs should … ?
a. Vividly describe the color of the food
b. Say “here comes some good food” when feeding the resident an especially delicious bite
c. Describe the location of the food on the plate using the face of a clock, and describe the food in an appetizing way
d. Check the resident’s ID at least three times
6) If a resident receives 12 oz of fluid from an IV bag, drinks a 10 oz milkshake, and drinks 2 cups of green tea, what is their total fluid intake in mL?
a. 1,130
b. 1,170
c. 1,140
d. 1,200
7) If a resident drinks one cup of water, eats a grilled cheese sandwich with one cup of liquidy tomato soup, and finishes it off with ½ cup of ice cream, what is their meal’s total fluid intake in cc’s?
a. 1,000
b. 930
c. 960
d. 900
8) If a resident receives 900 mL of fluid from an IV bag, leaves two ounces of juice in a regular sized cup after drinking the rest, and then drinks a 10 oz mug of hot cocoa, what was their total fluid intake in mL for the afternoon?
a. 1,400
b. 1,380
c. 1,320
d. 1,290
9) If a resident eats a 4 oz cup of jello and one cup of ice chips, leaves 3 oz in a cup of coffee, receives 10 oz of fluid from an IV, and voids 200 mL of urine, what is their fluid intake in mL?
a. 610
b. 600
c. 810
d. 840
10) Respond to the following sentences with T (true) or F (false).
____ NAs may be responsible for inserting cleaning feeding tubes if the task is properly delegated.
____ Residents only have a limited time window where the NA will be able to assist them with their meal, so they should eat quickly to accommodate the staff’s schedule.
____ Residents receiving naso-gastric enteral nutrition will require especially attentive skin care around their nose.
____ “TPN” stands for Total Parenteral Nosh.
____ NAs will never be responsible for beginning or adjusting IV therapy.
11) Nutrition and fluid balance deals closely with the Big Three, especially concerning matters of Resident Rights and Safety. What is at least one example of an important Resident Rights consideration when facilitating a resident’s nutrition? What is at least one example of a safety consideration when facilitating a resident’s nutrition and fluid balance? As a nursing assistant, how would you handle each consideration listed?
12) You are assisting a resident with their meal in a common area. The resident likes to eat in their geri-chair; today they are experiencing a lot of back pain, and ask if they could please recline to a 60-degree angle to eat their meal. How would you respond to the resident and why?
References
- Raj, M. (2021, October 7). What's on the menu matters in healthcare for diverse patients. The Conversation. https://theconversation.com/whats-on-the-menu-matters-in-health-care-for-diverse-patients-166931 ↵
- Dugan, D. (2020). Nursing assisting: A foundation in caregiving (5th ed.), Chapter 14. Hartman. ↵
- The USDA also published a set of recommendations specifically geared towards older adults: https://www.myplate.gov/life-stages/older-adults ↵
- Sorrentino, S. A., & Remmert, L. N. (2019). Mosby's essentials for nursing assistants (6th ed.), Chapter 23. Elsevier. ↵
- Speyer, R., Cordier, R., Farneti, D., Nascimento, W., Pilz, W., Verin, E., Walshe, M., & Woisard, V. (2022). White Paper by the European Society for Swallowing Disorders: Screening and Non-instrumental Assessment for Dysphagia in Adults. Dysphagia, 37(2), 333–349. https://doi.org/10.1007/s00455-021-10283-7 ↵
- Staff, M. C. (2023, January 4). Edema. Mayo Clinic. www.mayoclinic.org/diseases-conditions/edema/symptoms-causes/syc-20366493 ↵
- Paulis, S. J. C., Everink, I. H. J., Halfens, R. J. G., Lohrmann, C., & Schols, J. M. G. A. (2022). Dehydration in the nursing home: Recognition and interventions taken by Dutch nursing staff. Journal of advanced nursing, 78(4), 1044–1054. doi.org/10.1111/jan.15032 ↵
- Sorrentino, S. A., & Remmert, L. N. (2019). Mosby's essentials for nursing assistants (6th ed.). Elsevier. ↵
- Nursing Assistant by Chippewa Valley Technical College, Chapters 5 and 6 is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted. ↵


21.5: The Adaptive Immune Response - B Lymphocytes and Antibodies
By the end of this section, you will be able to:
- Explain how B cells mature and how B cell tolerance develops
- Discuss how B cells are activated and differentiate into plasma cells
- Describe the structure of the antibody classes and their functions
Antibodies were the first component of the adaptive immune response to be characterized by scientists working on the immune system. It was already known that individuals who survived a bacterial infection were immune to re-infection with the same pathogen. Early microbiologists took serum from an immune patient and mixed it with a fresh culture of the same type of bacteria, then observed the bacteria under a microscope. The bacteria became clumped in a process called agglutination. When a different bacterial species was used, the agglutination did not happen. Thus, there was something in the serum of immune individuals that could specifically bind to and agglutinate bacteria.
Scientists now know the cause of the agglutination is an antibody molecule, also called an immunoglobulin . What is an antibody? An antibody protein is essentially a secreted form of a B cell receptor. (In fact, surface immunoglobulin is another name for the B cell receptor.) Not surprisingly, the same genes encode both the secreted antibodies and the surface immunoglobulins. One minor difference in the way these proteins are synthesized distinguishes a naïve B cell with antibody on its surface from an antibody-secreting plasma cell with no antibodies on its surface. The antibodies of the plasma cell have the exact same antigen-binding site and specificity as their B cell precursors.
There are five different classes of antibody found in humans: IgM, IgD, IgG, IgA, and IgE. Each of these has specific functions in the immune response, so by learning about them, researchers can learn about the great variety of antibody functions critical to many adaptive immune responses.
B cells do not recognize antigen in the complex fashion of T cells. B cells can recognize native, unprocessed antigen and do not require the participation of MHC molecules and antigen-presenting cells.
B Cell Differentiation and Activation
B cells differentiate in the bone marrow. During the process of maturation, up to 100 trillion different clones of B cells are generated, which is similar to the diversity of antigen receptors seen in T cells.
B cell differentiation and the development of tolerance are not quite as well understood as it is in T cells. Central tolerance is the destruction or inactivation of B cells that recognize self-antigens in the bone marrow, and its role is critical and well established. In the process of clonal deletion , immature B cells that bind strongly to self-antigens expressed on tissues are signaled to induce their own destruction by apoptosis, removing them from the population. In the process of clonal anergy , however, B cells exposed to soluble antigen in the bone marrow are not physically deleted, but become unable to function.
Another mechanism called peripheral tolerance is a direct result of T cell tolerance. In peripheral tolerance , functional, mature B cells leave the bone marrow but have yet to be exposed to self-antigen. Most protein antigens require signals from helper T cells (Th2) to proceed to make antibody. When a B cell binds to a self-antigen but receives no signals from a nearby Th2 cell to produce antibody, the cell is signaled to undergo apoptosis and is destroyed. This is yet another example of the control that T cells have over the adaptive immune response.
After B cells are activated by their binding to antigen, they differentiate into plasma cells. Plasma cells often leave the secondary lymphoid organs, where the response is generated, and migrate back to the bone marrow, where the whole differentiation process started. After secreting antibodies for a specific period, they die, as most of their energy is devoted to making antibodies and not to maintaining themselves. Thus, plasma cells are said to be terminally differentiated.
The final B cell of interest is the memory B cell, which results from the clonal expansion of an activated B cell. Memory B cells function in a way similar to memory T cells. They lead to a stronger and faster secondary response when compared to the primary response, as illustrated below.
Antibody Structure
Antibodies are glycoproteins consisting of two types of polypeptide chains with attached carbohydrates. The heavy chain and the light chain are the two polypeptides that form the antibody. The main differences between the classes of antibodies are in the differences between their heavy chains, but as you shall see, the light chains have an important role, forming part of the antigen-binding site on the antibody molecules.
Four-chain Models of Antibody Structures
All antibody molecules have two identical heavy chains and two identical light chains. (Some antibodies contain multiple units of this four-chain structure.) The Fc region of the antibody is formed by the two heavy chains coming together, usually linked by disulfide bonds (Figure \(\PageIndex{1}\)). The Fc portion of the antibody is important in that many effector cells of the immune system have Fc receptors. Cells having these receptors can then bind to antibody-coated pathogens, greatly increasing the specificity of the effector cells. At the other end of the molecule are two identical antigen-binding sites.
Five Classes of Antibodies and their Functions
In general, antibodies have two basic functions. They can act as the B cell antigen receptor or they can be secreted, circulate, and bind to a pathogen, often labeling it for identification by other forms of the immune response. Of the five antibody classes, notice that only two can function as the antigen receptor for naïve B cells: IgM and IgD (Figure \(\PageIndex{2}\)). Mature B cells that leave the bone marrow express both IgM and IgD, but both antibodies have the same antigen specificity. Only IgM is secreted, however, and no other nonreceptor function for IgD has been discovered.
IgM consists of five four-chain structures (20 total chains with 10 identical antigen-binding sites) and is thus the largest of the antibody molecules. IgM is usually the first antibody made during a primary response. Its 10 antigen-binding sites and large shape allow it to bind well to many bacterial surfaces. It is excellent at binding complement proteins and activating the complement cascade, consistent with its role in promoting chemotaxis, opsonization, and cell lysis. Thus, it is a very effective antibody against bacteria at early stages of a primary antibody response. As the primary response proceeds, the antibody produced in a B cell can change to IgG, IgA, or IgE by the process known as class switching. Class switching is the change of one antibody class to another. While the class of antibody changes, the specificity and the antigen-binding sites do not. Thus, the antibodies made are still specific to the pathogen that stimulated the initial IgM response.
IgG is a major antibody of late primary responses and the main antibody of secondary responses in the blood. This is because class switching occurs during primary responses. IgG is a monomeric antibody that clears pathogens from the blood and can activate complement proteins (although not as well as IgM), taking advantage of its antibacterial activities. Furthermore, this class of antibody is the one that crosses the placenta to protect the developing fetus from disease exits the blood to the interstitial fluid to fight extracellular pathogens.
IgA exists in two forms, a four-chain monomer in the blood and an eight-chain structure, or dimer, in exocrine gland secretions of the mucous membranes, including mucus, saliva, and tears. Thus, dimeric IgA is the only antibody to leave the interior of the body to protect body surfaces. IgA is also of importance to newborns, because this antibody is present in mother’s breast milk (colostrum), which serves to protect the infant from disease.
IgE is usually associated with allergies and anaphylaxis. It is present in the lowest concentration in the blood, because its Fc region binds strongly to an IgE-specific Fc receptor on the surfaces of mast cells. IgE makes mast cell degranulation very specific, such that if a person is allergic to peanuts, there will be peanut-specific IgE bound to their mast cells. In this person, eating peanuts will cause the mast cells to degranulate, sometimes causing severe allergic reactions, including anaphylaxis, a severe, systemic allergic response that can cause death.
Clonal Selection of B Cells
Clonal selection and expansion work much the same way in B cells as in T cells. Only B cells with appropriate antigen specificity are selected for and expanded (Figure \(\PageIndex{3}\)). Eventually, the plasma cells secrete antibodies with antigenic specificity identical to those that were on the surfaces of the selected B cells. Notice in the figure that both plasma cells and memory B cells are generated simultaneously.
Primary versus Secondary B Cell Responses
Primary and secondary responses as they relate to T cells were discussed earlier. This section will look at these responses with B cells and antibody production. Because antibodies are easily obtained from blood samples, they are easy to follow and graph (Figure \(\PageIndex{4}\)). As you will see from the figure, the primary response to an antigen (representing a pathogen) is delayed by several days. This is the time it takes for the B cell clones to expand and differentiate into plasma cells. The level of antibody produced is low, but it is sufficient for immune protection. The second time a person encounters the same antigen, there is no time delay, and the amount of antibody made is much higher. Thus, the secondary antibody response overwhelms the pathogens quickly and, in most situations, no symptoms are felt. When a different antigen is used, another primary response is made with its low antibody levels and time delay.
Active versus Passive Immunity
Immunity to pathogens, and the ability to control pathogen growth so that damage to the tissues of the body is limited, can be acquired by (1) the active development of an immune response in the infected individual or (2) the passive transfer of immune components from an immune individual to a nonimmune one. Both active and passive immunity have examples in the natural world and as part of medicine.
Active immunity is the resistance to pathogens acquired during an adaptive immune response within an individual (Table \(\PageIndex{1}\)). Naturally acquired active immunity, the response to a pathogen, is the focus of this chapter. Artificially acquired active immunity involves the use of vaccines. A vaccine is a killed or weakened pathogen or its components that, when administered to a healthy individual, leads to the development of immunological memory (a weakened primary immune response) without causing much in the way of symptoms. Thus, with the use of vaccines, one can avoid the damage from disease that results from the first exposure to the pathogen, yet reap the benefits of protection from immunological memory. The advent of vaccines was one of the major medical advances of the twentieth century and led to the eradication of smallpox and the control of many infectious diseases, including polio, measles, and whooping cough.
| Natural | Artificial | |
|---|---|---|
| Active | Adaptive immune response | Vaccine response |
| Passive | Trans-placental antibodies/breastfeeding | Immune globulin injections |
Passive immunity arises from the transfer of antibodies to an individual without requiring them to mount their own active immune response. Naturally acquired passive immunity is seen during fetal development. IgG is transferred from the maternal circulation to the fetus via the placenta, protecting the fetus from infection and protecting the newborn for the first few months of its life. As already stated, a newborn benefits from the IgA antibodies it obtains from milk during breastfeeding. The fetus and newborn thus benefit from the immunological memory based on the pathogens to which the pregnant person has been exposed. In medicine, artificially acquired passive immunity usually involves injections of immunoglobulins, taken from animals previously exposed to a specific pathogen. This treatment is a fast-acting method of temporarily protecting an individual who was possibly exposed to a pathogen. The downside to both types of passive immunity is the lack of the development of immunological memory. Once the antibodies are transferred, they are effective for only a limited time before they degrade.
Interactive Link
Immunity can be acquired in an active or passive way, and it can be natural or artificial. Watch this video to see an animated discussion of passive and active immunity. What is an example of natural immunity acquired passively?
T cell-dependent versus T cell-independent Antigens
As discussed previously, Th2 cells secrete cytokines that drive the production of antibodies in a B cell, responding to complex antigens such as those made by proteins. On the other hand, some antigens are T cell independent. A T cell-independent antigen usually is in the form of repeated carbohydrate moieties found on the cell walls of bacteria. Each antibody on the B cell surface has two binding sites, and the repeated nature of T cell-independent antigen leads to crosslinking of the surface antibodies on the B cell. The crosslinking is enough to activate it in the absence of T cell cytokines.
A T cell-dependent antigen , on the other hand, usually is not repeated to the same degree on the pathogen and thus does not crosslink surface antibody with the same efficiency. To elicit a response to such antigens, the B and T cells must come close together (Figure \(\PageIndex{5}\)). The B cell must receive two signals to become activated. Its surface immunoglobulin must recognize native antigen. Some of this antigen is internalized, processed, and presented to the Th2 cells on a class II MHC molecule. The T cell then binds using its antigen receptor and is activated to secrete cytokines that diffuse to the B cell, finally activating it completely. Thus, the B cell receives signals from both its surface antibody and the T cell via its cytokines, and acts as a professional antigen-presenting cell in the process.


 Both methods have advantages and disadvantages. Asexual reproduction produces offspring that are genetically identical to the parent because the offspring are all clones of the original parent. A single individual can produce offspring asexually and large numbers of offspring can be produced quickly. In a stable or predictable environment, asexual reproduction is an effective means of reproduction because all the offspring will be adapted to that environment. In an unstable or unpredictable environment asexually-reproducing species may be at a disadvantage because all the offspring are genetically identical and may not have the genetic variation to survive in new or different conditions. On the other hand, the rapid rates of asexual reproduction may allow for a speedy response to environmental changes if individuals have mutations. An additional advantage of asexual reproduction is that colonization of new habitats may be easier when an individual does not need to find a mate to reproduce.
During sexual reproduction the genetic material of two individuals is combined to produce genetically diverse offspring that differ from their parents. The genetic diversity of sexually produced offspring is thought to give species a better chance of surviving in an unpredictable or changing environment. Species that reproduce sexually must maintain two different types of individuals, males and females, which can limit the ability to colonize new habitats as both sexes must be present.
Asexual Reproduction
Asexual reproduction occurs in prokaryotic microorganisms (bacteria) and in some eukaryotic single-celled and multi-celled organisms. There are a number of ways that animals reproduce asexually.
Fission
Fission , also called binary fission, occurs in prokaryotic microorganisms and in some invertebrate, multi-celled organisms. After a period of growth, an organism splits into two separate organisms. Some unicellular eukaryotic organisms undergo binary fission by mitosis. In other organisms, part of the individual separates and forms a second individual. This process occurs, for example, in many asteroid echinoderms through splitting of the central disk. Some sea anemones and some coral polyps (Figure \(\PageIndex{1}\)) also reproduce through fission.
Budding
Budding is a form of asexual reproduction that results from the outgrowth of a part of a cell or body region leading to a separation from the original organism into two individuals. Budding occurs commonly in some invertebrate animals such as corals and hydras. In hydras, a bud forms that develops into an adult and breaks away from the main body, as illustrated in Figure \(\PageIndex{2}\), whereas in coral budding, the bud does not detach and multiplies as part of a new colony.
Link to Learning
Watch a video of a hydra budding.
Fragmentation
Fragmentation is the breaking of the body into two parts with subsequent regeneration. If the animal is capable of fragmentation, and the part is big enough, a separate individual will regrow.
For example, in many sea stars, asexual reproduction is accomplished by fragmentation. Figure \(\PageIndex{3}\) illustrates a sea star for which an arm of the individual is broken off and regenerates a new sea star. Fisheries workers have been known to try to kill the sea stars eating their clam or oyster beds by cutting them in half and throwing them back into the ocean. Unfortunately for the workers, the two parts can each regenerate a new half, resulting in twice as many sea stars to prey upon the oysters and clams. Fragmentation also occurs in annelid worms, turbellarians, and poriferans.
Note that in fragmentation, there is generally a noticeable difference in the size of the individuals, whereas in fission, two individuals of approximate size are formed.
Parthenogenesis
Parthenogenesis is a form of asexual reproduction where an egg develops into a complete individual without being fertilized. The resulting offspring can be either haploid or diploid, depending on the process and the species. Parthenogenesis occurs in invertebrates such as water flees, rotifers, aphids, stick insects, some ants, wasps, and bees. Bees use parthenogenesis to produce haploid males (drones) and diploid females (workers). If an egg is fertilized, a queen is produced. The queen bee controls the reproduction of the hive bees to regulate the type of bee produced.
Some vertebrate animals—such as certain reptiles, amphibians, and fish—also reproduce through parthenogenesis. Although more common in plants, parthenogenesis has been observed in animal species that were segregated by sex in terrestrial or marine zoos. Two female Komodo dragons, a hammerhead shark, and a blacktop shark have produced parthenogenic young when the females have been isolated from males.
Sexual Reproduction
Sexual reproduction is the combination of (usually haploid) reproductive cells from two individuals to form a third (usually diploid) unique offspring. Sexual reproduction produces offspring with novel combinations of genes. This can be an adaptive advantage in unstable or unpredictable environments. As humans, we are used to thinking of animals as having two separate sexes—male and female—determined at conception. However, in the animal kingdom, there are many variations on this theme.
Hermaphroditism
Hermaphroditism occurs in animals where one individual has both male and female reproductive parts. Invertebrates such as earthworms, slugs, tapeworms and snails, shown in Figure \(\PageIndex{4}\), are often hermaphroditic. Hermaphrodites may self-fertilize or may mate with another of their species, fertilizing each other and both producing offspring. Self fertilization is common in animals that have limited mobility or are not motile, such as barnacles and clams.
 Individuals homozygous for X (XX) are female and heterozygous individuals (XY) are male. The presence of a Y chromosome causes the development of male characteristics and its absence results in female characteristics. The XY system is also found in some insects and plants.
Avian sex determination is dependent on the presence of Z and W chromosomes. Homozygous for Z (ZZ) results in a male and heterozygous (ZW) results in a female. The W appears to be essential in determining the sex of the individual, similar to the Y chromosome in mammals. Some fish, crustaceans, insects (such as butterflies and moths), and reptiles use this system.
The sex of some species is not determined by genetics but by some aspect of the environment. Sex determination in some crocodiles and turtles, for example, is often dependent on the temperature during critical periods of egg development. This is referred to as environmental sex determination, or more specifically as temperature-dependent sex determination. In many turtles, cooler temperatures during egg incubation produce males and warm temperatures produce females. In some crocodiles, moderate temperatures produce males and both warm and cool temperatures produce females. In some species, sex is both genetic- and temperature-dependent.
 If the individual is female first, it is termed protogyny or “first female,” if it is male first, its termed protandry or “first male.”
Summary
Reproduction may be asexual when one individual produces genetically identical offspring, or sexual when the genetic material from two individuals is combined to produce genetically diverse offspring. Asexual reproduction occurs through fission, budding, and fragmentation. Sexual reproduction may mean the joining of sperm and eggs within animals’ bodies or it may mean the release of sperm and eggs into the environment. An individual may be one sex, or both; it may start out as one sex and switch during its life, or it may stay male or female.
Glossary
- asexual reproduction
- form of reproduction that produces offspring that are genetically identical to the parent
- budding
- form of asexual reproduction that results from the outgrowth of a part of a cell leading to a separation from the original animal into two individuals
- fission
- (also, binary fission) method by which multicellular organisms increase in size or asexual reproduction in which a unicellular organism splits into two separate organisms by mitosis
- fragmentation
- cutting or fragmenting of the original animal into parts and the growth of a separate animal from each part
- hermaphroditism
- state of having both male and female reproductive parts within the same individual
- parthenogenesis
- form of asexual reproduction where an egg develops into a complete individual without being fertilized
- sexual reproduction
- mixing of genetic material from two individuals to produce genetically unique offspring


1.1.4: Lipids
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What you’ll learn to do: Illustrate different types of lipids and relate their structure to their role in biological systems
Fats and oils are probably the type of lipid that you’re most familiar with in your everyday life. The word fat typically brings up a negative picture in our minds. In diets, we’re advised to stay away from fatty foods. However, our bodies require some fat in order to survive. There are also other lipids essential to human life, including phospholipids, steroids, and waxes.
While an excess of any substance can be a problem, all of these lipids play essential roles in living things.
In this outcome, we will discuss lipids and the role they plan in our bodies.
Learning Objectives
- Distinguish between the different kinds of lipids
- Identify several major functions of lipids
Lipids include a diverse group of compounds that are largely nonpolar in nature. This is because they are hydrocarbons that include mostly nonpolar carbon–carbon or carbon–hydrogen bonds. Non-polar molecules are hydrophobic (“water fearing”), or insoluble in water. Lipids perform many different functions in a cell. Cells store energy for long-term use in the form of fats. Lipids also provide insulation from the environment for plants and animals (Figure 1). For example, they help keep aquatic birds and mammals dry when forming a protective layer over fur or feathers because of their water-repellant hydrophobic nature. Lipids are also the building blocks of many hormones and are an important constituent of all cellular membranes. Lipids include fats, oils, waxes, phospholipids, and steroids.
Fats and Oils
A fat molecule, such as a triglyceride, consists of two main components—glycerol and fatty acids. Glycerol is an organic compound with three carbon atoms, five hydrogen atoms, and three hydroxyl (–OH) groups. Fatty acids have a long chain of hydrocarbons to which an acidic carboxyl group is attached, hence the name “fatty acid.” The number of carbons in the fatty acid may range from 4 to 36; most common are those containing 12–18 carbons. In a fat molecule, a fatty acid is attached to each of the three oxygen atoms in the –OH groups of the glycerol molecule with a covalent bond (Figure 2).
During this covalent bond formation, three water molecules are released. The three fatty acids in the fat may be similar or dissimilar. These fats are also called triglycerides because they have three fatty acids. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogaea , the scientific name for peanuts.
Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized.
When the hydrocarbon chain contains a double bond, the fatty acid is an unsaturated fatty acid.
Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil).
Saturated fats tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid contained in meat, and the fat with butyric acid contained in butter, are examples of saturated fats. Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell. In plants, fat or oil is stored in seeds and is used as a source of energy during embryonic development.
Unsaturated fats or oils are usually of plant origin and contain unsaturated fatty acids. The double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly, keeping them liquid at room temperature. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to improve blood cholesterol levels, whereas saturated fats contribute to plaque formation in the arteries, which increases the risk of a heart attack.
Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans -fats. Recent studies have shown that an increase in trans -fats in the human diet may lead to an increase in levels of low-density lipoprotein (LDL), or “bad” cholesterol, which, in turn, may lead to plaque deposition in the arteries, resulting in heart disease. Many fast food restaurants have recently eliminated the use of trans -fats, and U.S. food labels are now required to list their trans -fat content.In the food industry, oils are artificially hydrogenated to make them semi-solid, leading to less spoilage and increased shelf life. Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis -conformation in the hydrocarbon chain may be converted to double bonds in the trans -conformation. This forms a trans -fat from a cis -fat. The orientation of the double bonds affects the chemical properties of the fat (Figure 3).
Essential fatty acids are fatty acids that are required but not synthesized by the human body. Consequently, they must be supplemented through the diet. Omega-3 fatty acids fall into this category and are one of only two known essential fatty acids for humans (the other being omega-6 fatty acids). They are a type of polyunsaturated fat and are called omega-3 fatty acids because the third carbon from the end of the fatty acid participates in a double bond.
Salmon, trout, and tuna are good sources of omega-3 fatty acids. Omega-3 fatty acids are important in brain function and normal growth and development. They may also prevent heart disease and reduce the risk of cancer.
Like carbohydrates, fats have received a lot of bad publicity. It is true that eating an excess of fried foods and other “fatty” foods leads to weight gain. However, fats do have important functions. Fats serve as long-term energy storage. They also provide insulation for the body. Therefore, “healthy” unsaturated fats in moderate amounts should be consumed on a regular basis.
Phospholipids
Phospholipids are the major constituent of the plasma membrane. Like fats, they are composed of fatty acid chains attached to a glycerol or similar backbone. Instead of three fatty acids attached, however, there are two fatty acids and the third carbon of the glycerol backbone is bound to a phosphate group. The phosphate group is modified by the addition of an alcohol.
A phospholipid has both hydrophobic and hydrophilic regions. The fatty acid chains are hydrophobic and exclude themselves from water, whereas the phosphate is hydrophilic and interacts with water.
Cells are surrounded by a membrane, which has a bilayer of phospholipids. The fatty acids of phospholipids face inside, away from water, whereas the phosphate group can face either the outside environment or the inside of the cell, which are both aqueous.
Steroids and Waxes
Unlike the phospholipids and fats discussed earlier, steroids have a ring structure. Although they do not resemble other lipids, they are grouped with them because they are also hydrophobic. All steroids have four, linked carbon rings and several of them, like cholesterol, have a short tail.
Cholesterol is a steroid. Cholesterol is mainly synthesized in the liver and is the precursor of many steroid hormones, such as testosterone and estradiol. It is also the precursor of vitamins E and K. Cholesterol is the precursor of bile salts, which help in the breakdown of fats and their subsequent absorption by cells. Although cholesterol is often spoken of in negative terms, it is necessary for the proper functioning of the body. It is a key component of the plasma membranes of animal cells.
Waxes are made up of a hydrocarbon chain with an alcohol (–OH) group and a fatty acid. Examples of animal waxes include beeswax and lanolin. Plants also have waxes, such as the coating on their leaves, that helps prevent them from drying out.
For an additional perspective on lipids, explore this interactive animation .Learning Objectives
Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Major types include fats and oils, waxes, phospholipids, and steroids. Fats are a stored form of energy and are also known as triacylglycerols or triglycerides. Fats are made up of fatty acids and either glycerol or sphingosine. Fatty acids may be unsaturated or saturated, depending on the presence or absence of double bonds in the hydrocarbon chain. If only single bonds are present, they are known as saturated fatty acids. Unsaturated fatty acids may have one or more double bonds in the hydrocarbon chain. Phospholipids make up the matrix of membranes. They have a glycerol or sphingosine backbone to which two fatty acid chains and a phosphate-containing group are attached. Steroids are another class of lipids. Their basic structure has four fused carbon rings. Cholesterol is a type of steroid and is an important constituent of the plasma membrane, where it helps to maintain the fluid nature of the membrane. It is also the precursor of steroid hormones such as testosterone.
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Contributors and Attributions
- Introduction to Lipids. Authored by : Shelli Carter and Lumen Learning. Provided by : Lumen Learning. License : CC BY: Attribution
- Biology. Provided by : OpenStax CNX. Located at<EMAIL_ADDRESS>. License : CC BY: Attribution . License Terms : Download for free at http://cnx.org/contents/185cbf87-c72...f21b5eabd@10.8