vary from brief and nearly undetectable periods to long periods of vigorous shaking. these episodes can result in physical injuries, including occasionally broken bones. in epilepsy, seizures have a tendency to recur and, as a rule, have no immediate underlying cause. isolated seizures that are provoked by a specific cause such as poisoning are not deemed to represent epilepsy. erectile dysfunction – (ed), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. it is the most common sexual problem in men. through its connection to self-image and to problems in sexual relationships, erectile dysfunction can cause psychological harm. erector spinae muscles – the erector spinae or spinal erectors is a set of muscles that straighten and rotate the back. esophagus – the esophagus, (american english) or oesophagus (british english; see spelling differences) (/ɪˈsɒfəɡəs/), informally known as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the stomach. the esophagus is a fibromuscular tube, about 25 cm (10 in) long in adults, which travels behind the trachea and heart, passes through the diaphragm and empties into the uppermost region of the stomach. during swallowing, the epiglottis tilts backwards to prevent food from going down the larynx and lungs. extensor pollicis brevis muscle – in human anatomy, the extensor pollicis brevis is a skeletal muscle on the dorsal side of the forearm. it lies on the medial side of, and is closely connected with, the abductor pollicis longus. extensor pollicis et indicis communis muscle – in human anatomy, the extensor pollicis et indicis communis is an aberrant muscle in the posterior compartment of forearm. it was first described in 1863. the muscle has a prevalence from 0.5% to 4%. extensor pollicis longus muscle – in human anatomy, the extensor pollicis longus muscle (epl) is a skeletal muscle located dorsally on the forearm. it is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with this muscle. external carotid artery – is a major artery of the head and neck. it arises from the common carotid artery when it splits into the external and internal carotid artery. external carotid artery supplies blood to the face and neck. external iliac artery – the external iliac arteries are two major arteries which bifurcate off the common iliac arteries anterior to the sacroiliac joint of the pelvis. external iliac vein – the external iliac veins are large veins that connect the femoral veins to the common iliac veins. their origin is at the inferior margin of the inguinal ligaments and they terminate when they join the internal iliac veins (to form the common iliac veins). both external iliac veins are accompanied along their course by external iliac arteries. external jugular vein – receives the greater part of the blood from the exterior of the cranium and the deep parts of the face, being formed by the junction of the posterior division of the retromandibular vein with the posterior auricular vein. eye – the human eye is a sense organ that reacts to light and allows vision. rod and cone cells in the retina are photoreceptive cells which are able to detect visible light and convey this information to the brain. eyes signal information which is used by the brain to elicit the perception of color, shape, depth, movement, and other features. the eye is part of the sensory nervous system. similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin, and entrainment of the circadian rhythm. eye surgery – f face – is the front of an animal's head that features three of the head's sense organs, the eyes, nose, and mouth, and through which animals express many of their emotions. the face is crucial for human identity, and damage such as scarring or developmental deformities affects the psyche adversely. fallopian tube – the fallopian tubes, also known as uterine tubes or salpinges (singular salpinx), are tubes that stretch from the uterus to the ovaries, and are part of the female reproductive system. the fertilized egg passes through the fallopian tubes from the ovaries of female mammals to the uterus. the fallopian tubes is simple columnar epithelium with hair-like extensions called cilia which carry the fertilized egg. in other animals, the equivalent of a fallopian tube is an oviduct. fellowship (medicine) – is the period of medical training, in the united states and canada, that a physician, dentist, or veterinarian may undertake after completing a specialty training program (residency). during this time (usually more than one year), the physician is known as a fellow. fellows are capable of acting as an attending physician or a consultant physician in the specialist field in which they were trained, such as internal medicine or pediatrics. after completing a fellowship in the relevant sub-specialty, the physician is permitted to practice without direct supervision by other physicians in that sub-specialty, such as cardiology or oncology. female reproductive system – is made up of the internal and external sex organs that function in reproduction of new offspring. in humans, the female reproductive system is immature at birth and develops to maturity at puberty to be able to produce gametes, and to carry a foetus to full term. the internal sex organs are the uterus, fallopian tubes, and ovaries. the uterus or womb accommodates the embryo which develops into the foetus. the uterus also produces vaginal and uterine secretions which help the transit of sperm to the fallopian tubes. the ovaries produce the ova (egg cells). the external sex organs are also known as the genitals and these are the organs of the vulva including the labia, clitoris, and vaginal opening. the vagina is connected to the uterus at the cervix. femoral artery – is a large artery in the thigh and the main arterial supply to the thigh and leg. it enters the thigh from behind the inguinal ligament as the continuation of the external iliac artery. femoral nerve – is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee. femoral vein – in the human body, the femoral vein is a blood vessel that accompanies the femoral artery in the femoral sheath. it begins at the adductor hiatus (an opening in the adductor magnus muscle) and is a continuation of the popliteal vein. it ends at the inferior margin of the inguinal ligament, where it becomes the external iliac vein. the femoral vein bears valves which are mostly bicuspid and whose number is variable between individuals and often between left and right leg. femur – the femur, or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrate, the largest bone of the human body. the head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with the tibia and kneecap, forming the knee joint. fibromyalgia – fibrous joint – fibula – finger – first aid – flat bone – foot – forearm – forehead – frontal bone – frontal nerve – is the largest branch of the ophthalmic nerve (v1), itself a branch of the trigeminal nerve (cn v). the frontal nerve branches from the ophthalmic nerve immediately before entering the superior orbital fissure. in then travels superolateral to the annulus of zinn between the lacrimal nerve and inferior ophthalmic vein. after entering the orbit it travels anteriorly between the roof periosteum and the levator palpebrae superioris. midway between the apex and base of the orbit it divides into two branches, the supratrochlear nerve and supraorbital nerve. the two branches of the frontal nerve provide sensory innervation to the skin of the forehead, mucosa of the frontal sinus, and the skin of the upper eyelid. frontalis muscle – g gallbladder – in vertebrates, the gallbladder is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. in humans, the pear-shaped gallbladder lies beneath the liver, although the structure and position of the gallbladder can vary significantly among animal species. it receives and stores bile, produced by the liver, via the common hepatic duct and releases it via the common bile duct into the duodenum, where the bile helps in the digestion of fats. gamete – is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. gametes are an organism's reproductive cells, also referred to as sex cells. ganglion – is a group of neuron cell bodies in the peripheral nervous system. in the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. in the autonomic nervous system there are both sympathetic and parasympathetic ganglia which contain the cell bodies of postganglionic sympathetic and parasympathetic neurons respectively. gastrocnemius muscle – (plural gastrocnemii) is a superficial two-headed muscle that is in the back part of the lower leg of humans. it runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar joints). the muscle is named via latin, from greek γαστήρ (gaster) 'belly' or 'stomach' and κνήμη (knḗmē) 'leg', meaning 'stomach of leg' (referring to the bulging shape of the calf). gastroenterology – gastroenterology is the branch of medicine focused on the digestive system and its disorders. diseases affecting the gastrointestinal tract, which include the organs from mouth into anus, along the alimentary canal, are the focus of this speciality. gastrointestinal tract – the gastrointestinal tract, (gi tract, git, digestive tract, digestion tract, alimentary canal) is the tract from the mouth to the anus which includes all the organs of the digestive system in humans and other animals. food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled as feces. the mouth, esophagus, stomach and intestines are all part of the gastrointestinal tract. gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines. a tract is a collection of related anatomic structures or a series of connected body organs. gene therapy – (also called human gene transfer) is a medical field which focuses on the utilization of the therapeutic delivery of nucleic acids into a patient's cells as a drug to treat disease. general surgery – is a surgical specialty that focuses on abdominal contents including esophagus, stomach, small intestine, large intestine, liver, pancreas, gallbladder, appendix and bile ducts, and often the thyroid gland (depending on local referral patterns). they also deal with diseases involving the skin, breast, soft tissue, trauma, peripheral artery disease and hernias and perform endoscopic procedures such as gastroscopy and colonoscopy. genetics – is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. genitourinary system – the genitourinary system, or urogenital system, are the organs of the reproductive system and the urinary system. these are grouped together because of their proximity to each other, their common embryological origin and the use of common pathways, like the male urethra. also, because of their proximity, the systems are sometimes imaged together. geriatrics – or geriatric medicine, is a specialty that focuses on health care of elderly people. it aims to promote health by preventing and treating diseases and disabilities in older adults. there is no set age at which patients may be under the care of a geriatrician, or geriatric physician, a physician who specializes in the care of elderly people. rather, this decision is determined by the individual patient's needs, and the availability of a specialist. it is important to note the difference between geriatrics, the care of aged people, and gerontology, which is the study of the aging process itself. the term geriatrics comes from the greek γέρων geron meaning "old man", and ιατρός iatros meaning "healer". however, geriatrics is sometimes called medical gerontology. gonad – a gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and