Good nutrition can help prevent disease and promote health. There are six categories of nutrients that the body needs to acquire from food: protein, carbohydrates, fat, fibers, vitamins and minerals, and water. Protein supplies amino acids to build and maintain healthy body tissue. There are 20 amino acids considered essential because the body must have all of them in the right amounts to function…
Rhythmic, oscillating motions of the eyes are called nystagmus. The to-and-fro motion is generally involuntary. Vertical nystagmus occurs much less frequently than horizontal nystagmus and is often, but not necessarily, a sign of serious brain damage. Nystagmus can be a normal physiological response or a result of a pathologic problem. ulation refers to a medical method of testing their connection…
Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death. Obesity traditionally has been defined as a weight at least 20% above the weight corresponding to the lowest death rate for individuals of a specific height, gender, and age (ideal weight). Twenty to forty p…
Obesity surgery is an operation that reduces or bypasses the stomach or small intestine so that severely overweight people can achieve significant and permanent weight loss. Obesity surgery, also called bariatric surgery, is performed only on severely overweight people who are more than twice their ideal weight. This level of obesity often is refered to as morbid obesity since it can result in man…
Obsessive-compulsive disorder (OCD) is a type of anxiety disorder. Anxiety disorder is the experience of prolonged, excessive worry about circumstances in one's life. OCD is characterized by distressing repetitive thoughts, impulses or images that are intense, frightening, absurd, or unusual. These thoughts are followed by ritualized actions that are usually bizarre and irrational. These ri…
Obstetrical emergencies are life-threatening medical conditions that occur in pregnancy or during or after labor and delivery. There are a number of illnesses and disorders of pregnancy that can threaten the well-being of both mother and child. Obstetrical emergencies may also occur during active labor, and after delivery (postpartum). ECTOPIC PREGNANCY. An ectopic, or tubal, pregnancy occurs when…
Occupational asthma is a form of lung disease in which the breathing passages shrink, swell, or become inflamed or congested as a result of exposure to irritants in the workplace. As many as 15% of all cases of asthma may be related to on-the-job exposure to: Hundreds of different types of jobs involve exposure to substances that could trigger occupational asthma, but only a small fraction of…
Medical dictionaries define oligomenorrhea as infrequent or very light menstruation. But physicians typically apply a narrower definition, restricting the diagnosis of oligomenorrhea to women whose periods were regularly established before they developed problems with infrequent flow. With oligomenorrhea, menstrual periods occur at intervals of greater than 35 days, with only four to nine periods …
Onychomycosis is a fungal infection of the fingernails or toenails. The actual infection is of the bed of the nail and of the plate under the surface of the nail. Onychomycosis is the most common of all diseases of the nails in adults. In North America, the incidence falls roughly between 2–13%. The incidence of onychomycosis is also greater in older adults, and up to 90% of the elderly may…
Oophorectomy is the surgical removal of one or both ovaries. It is also called ovariectomy. If one ovary is removed, a woman may continue to menstruate and have children. If both ovaries are removed, menstruation stops and a woman loses the ability to have children. Oophorectomy is performed to: In an oophorectomy one or a portion of one ovary may be removed or both ovaries may be removed. When oo…
Ophthalmoplegia is a paralysis or weakness of one or more of the muscles that control eye movement. The condition can be caused by any of several neurologic disorders. It may be myopathic, meaning that the muscles controlling eye movement are directly involved, or neurogenic, meaning that the nerve pathways controlling eye muscles are affected. Diseases associated with ophthalmoplegia are ocular m…
Oppositional defiant disorder is a recurring pattern of negative, hostile, disobedient, and defiant behavior in a child or adolescent, lasting for at least six months without serious violation of the basic rights of others. The behavior disturbances cause clinically significant problems in social, school, or work functioning. The course of oppositional defiant disorder varies among patients. In ma…
Optic atrophy can be defined as damage to the optic nerve resulting in a degeneration or destruction of the optic nerve. Optic atrophy may also be referred to as optic nerve head pallor because of the pale appearance of the optic nerve head as seen at the back of the eye. Possible causes of optic atrophy include: optic neuritis, Leber's hereditary optic atrophy, toxic or nutritional optic n…
Optic neuritis is a vision disorder characterized by inflammation of the optic nerve. Optic neuritis occurs when the optic nerve, the pathway that transmits visual information to the brain, becomes inflamed and the myelin sheath that surrounds the nerve is destroyed (a process known as demyelination). It typically occurs in one eye at a time (70%), and the resulting vision loss is rapid and progre…
Oral contraceptives are medicines taken by mouth to help prevent pregnancy. They are also known as the Pill, OCs, or birth control pills. Oral contraceptives, also known as birth control pills, contain artificially made forms of two hormones produced naturally in the body. These hormones, estrogen and progestin, regulate a woman's menstrual cycle. When taken in the proper amounts, following…
Oral hygiene is the practice of keeping the mouth clean and healthy by brushing and flossing to prevent tooth decay and gum disease. The purpose of oral hygiene is to prevent the buildup of plaque, the sticky film of bacteria and food that forms on the teeth. Plaque adheres to the crevices and fissures of the teeth and generates acids that, when not removed on a regular basis, slowly eat away, or …
Periorbital cellulitis is an inflammation and infection of the eyelid and the skin surrounding the eye. Orbital cellulitis affects the eye socket (orbit) as well as the skin closest to it. Inside the eyelid is a septum. The septum divides the eyelid into outer and inner areas. This orbital septum helps prevent the spread of infection to the eye socket. Periorbital and orbital cellulitis are more c…
Orchitis is an inflammation of one or both testis, accompanied by swelling, pain, fever, and a sensation of heaviness in the affected area. Viral mumps is the most common cause of orchitis. Bacterial infections associated with the disorder are tuberculosis, syphilis, gonorrhea, and chlamydia. A mechanical injury to the groin area may also cause orchitis. Fifteen to twenty-five percent of males pas…
Orthopedic (sometimes spelled orthopaedic) surgery is surgery performed by a medical specialist, such as an orthopedist or orthopedic surgeon, trained to deal with problems that develop in the bones, joints, and ligaments of the human body. Orthopedic surgery corrects problems that arise in the skeleton and its attachments, the ligaments and tendons. It may also deal with some problems of the nerv…
Orthostatic hypotension is an abnormal decrease in blood pressure when a person stands up. This may lead to fainting. When a person stands upright, a certain amount of blood normally pools in the veins of the ankles and legs. This pooling means that there is slightly less blood for the heart to pump and causes a drop in blood pressure. Usually, the body responds to this drop so quickly, a person i…
Osteoarthritis (OA), which is also known as osteoarthrosis or degenerative joint disease (DJD), is a progressive disorder of the joints caused by gradual loss of cartilage and resulting in the development of bony spurs and cysts at the margins of the joints. The name osteoarthritis comes from three Greek words meaning bone, joint, and inflammation. OA is one of the most common causes of disability…
Osteochondroses is a group of diseases of children and adolescents in which localized tissue death (necrosis) occurs, usually followed by full regeneration of healthy bone tissue. The singular term is osteochondrosis. During the years of rapid bone growth, blood supply to the growing ends of bones (epiphyses) may become insufficient resulting in necrotic bone, usually near joints. The term avascul…
Osteogenesis imperfecta (OI) is a group of genetic diseases of collagen in which the bones are formed improperly, making them fragile and prone to breaking. Collagen is a fibrous protein material. It serves as the structural foundation of skin, bone, cartilage, and ligaments. In osteogenesis imperfecta, the collagen produced is abnormal and disorganized. This results in a number of abnormalities t…
Osteomyelitis refers to a bone infection, almost always caused by a bacteria. Over time, the result can be destruction of the bone itself. Bone infections may occur at any age. Certain conditions increase the risk of developing such an infection, including sickle cell anemia, injury, the presence of a foreign body (such as a bullet or a screw placed to hold together a broken bone), intravenous dru…
Osteopathy is a system and philosophy of health care that separated from traditional (allopathic) medical practice about a century ago. It places emphasis on the musculoskeletal system, hence the name—osteo refers to bone and path refers to disease. Osteopaths also believe strongly in the healing power of the body and do their best to facilitate that strength. During this century, the disci…
Osteopetrosis (plural osteopetroses) is a rare hereditary disorder that makes bones increase in both density and fragility. A potentially fatal condition that can deform bone structure and distort the appearance, osteopetrosis is also called chalk bones, ivory bones, or marble bones. Osteopetrosis occurs when bones are spongy or porous, or new bone is repeatedly added to calcified cartilage (harde…
The word osteoporosis literally means "porous bones." It occurs when bones lose an excessive amount of their protein and mineral content, particularly calcium. Over time, bone mass, and therefore bone strength, is decreased. As a result, bones become fragile and break easily. Even a sneeze or a sudden movement may be enough to break a bone in someone with severe osteoporosis. Osteopo…
A surgical procedure creating an opening in the body for the discharge of body wastes. Certain diseases of the bowel or urinary tract involve removing all or part of the intestine or bladder. This creates a need for an alternate way for feces or urine to leave the body. An opening is surgically created in the abdomen for body wastes to pass through. The surgical procedure is called an ostomy. The …
Otitis externa refers to an infection of the ear canal, the tube leading from the outside opening of the ear in towards the ear drum. The external ear canal is a tube approximately 1 in (2.5 cm) in length. It runs from the outside opening of the ear to the start of the middle ear, designated by the ear drum or tympanic membrane. The canal is partly cartilage and partly bone. In early childhood, th…
Otitis media is an infection of the middle ear space, behind the eardrum (tympanic membrane). A little knowledge of the basic anatomy of the middle ear will be helpful for understanding the development of otitis media. The external ear canal is that tube which leads from the outside opening of the ear to the structure called the tympanic membrane. Behind the tympanic membrane is the space called t…
Otosclerosis is an excessive growth in the bones of the middle ear which interferes with the transmission of sound. The middle ear consists of the eardrum and a chamber which contains three bones called the hammer, the anvil, and the stirrup (or stapes). Sound waves passing through the ear cause the ear drum to vibrate. This vibration is transmitted to the inner ear by the three bones. In the inne…
Ototoxicity is damage to the hearing or balance functions of the ear by drugs or chemicals. Ototoxicity is drug or chemical damage to the inner ear. This section of the ear contains both the hearing mechanism and the vestibulocochlear nerve, the nerve that sends hearing and balance information to the brain. Because of this, ototoxic drugs may cause lack of hearing, and loss of sense of balance. Th…
Ovarian cancer is cancer of the ovaries, the eggreleasing and hormone-producing organs of the female reproductive tract. Cancerous, or malignant, cells divide and multiply in an abnormal fashion. The ovaries are small, almond-shaped organs, located in the pelvic region, one on either side of the uterus. When a woman is in her childbearing years, the ovaries alternate to produce and release an egg …
Ovarian cysts are sacs containing fluid or semisolid material that develop in or on the surface of an ovary. An ovarian cyst is being surgically removed from a 25-year-old female patient. (Photograph by Art Siegel, Custom Medical Stock Photo. Reproduced by permission.) Ovarian cysts are common and the vast majority are harmless. Because they cause symptoms that may be the same as ovarian tu…
Ovarian torsion is the twisting of the ovary due to the influence of another condition or disease. This results in extreme lower abdominal pain. Ovarian torsion occurs infrequently only in females. In can occur in women of all ages, but most women that experience this are younger. Approximately 70-75% of cases occur in women under 30 years old. About 20% of all reported cases are in pregnant women…
Overhydration, also called water excess or water intoxication, is a condition in which the body contains too much water. Overhydration occurs when the body takes in more water than it excretes and its normal sodium level is diluted. This can result in digestive problems, behavioral changes, brain damage, seizures, or coma. An adult whose heart, kidneys, and pituitary gland are functioning properly…
Oxygen/ozone therapy is a term that describes a number of different practices in which oxygen, ozone, or hydrogen peroxide are administered via gas or water to kill disease microorganisms, improve cellular function, and promote the healing of damaged tissues. The rationale behind bio-oxidative therapies, as they are sometimes known, is the notion that as long as the body's needs for antioxi…
A pacemaker is a surgically-implanted electronic device that regulates a slow or erratic heartbeat. Pacemakers are implanted to regulate irregular contractions of the heart (arrhythmia). They are most frequently prescribed to speed the heartbeat of patients who have a heart rate well under 60 beats per minute (severe symptomatic bradycardia). They are also used in some cases to slow a fast heart r…
Paget's disease of bone (osteitis deformans) is the abnormal formation of bone tissue that results in weakened and deformed bones. Named for Sir James Paget (1814–1899), this disease affects 1–3% of people over 50 years of age, but affects over 10% of people over 80 years of age. Paget's disease can affect one or more bones in the body. Most often, the pelvis, bones in …
Paget's disease of the breast is a rare form of breast cancer which makes up approximately 1 to 4 percent of all breast tumors. While sharing its name with Paget's disease of bone, these are two medically unrelated conditions. They are simply named after the same doctor who first described them. Paget's disease of the breast is generally associated with an underlying breast ca…
Pain is an unpleasant feeling that is conveyed to the brain by sensory neurons. The discomfort signals actual or potential injury to the body. However, pain is more than a sensation, or the physical awareness of pain; it also includes perception, the subjective interpretation of the discomfort. Perception gives information on the pain's location, intensity, and something about its nature. T…
Pain management encompasses pharmacological, nonpharmacological, and other approaches to prevent, reduce, or stop pain sensations. Pain serves as an alert to potential or actual damage to the body. The definition for damage is quite broad; pain can arise from injury as well as disease. After the message is received and interpreted, further pain can be counter-productive. Pain can have a negative i…
A sensation in which a person is aware of an irregular, hard, or rapid heartbeat. Palpitations mean that the heart is not behaving normally. It can appear to skip beats, beat rapidly, beat irregularly, or thump in the chest. Although palpitations are very common and often harmless, they can be frightening to the person, who is usually unaware of his or her heartbeat. Palpitations can also be a sig…
Pancreas transplantation is a surgical procedure in which a diseased pancreas is replaced with a healthy pancreas that has been obtained immediately after death from an immunologically compatible donor. A surgeon harvests the islets of Langerhans from a donor pancreas. (Photograph by Daniel Portnoy. AP/Wide World Photo. Reproduced by permission.) The pancreas secretes insulin to regulate gl…
Pancreatectomy is the surgical removal of the pancreas. Pancreatectomy may be total, in which case the whole organ is removed, or partial, referring to the removal of part of the pancreas. Pancreatectomy is the most effective treatment for cancer of the pancreas, an abdominal organ that secretes digestive enzymes, insulin, and other hormones. The thickest part of the pancreas near the duodenum (sm…
Endocrine pancreatic cancer is a disease in which cancerous cells originate within the tissues of the pancreas that produce hormones. The pancreas is a 6–8 in (15–20 cm) long, slippershaped gland located in the abdomen. It lies behind the stomach, within a loop formed by the small intestine. Other nearby organs include the gallbladder, spleen, and liver. The pancreas has a wide end (…
Exocrine pancreatic cancer is a disease in which cancerous cells originate within the tissues of the pancreas that produce digestive juices. The pancreas is a 6–8 in (15–20 cm) long, slippershaped gland located in the abdomen. It lies behind the stomach, within a loop formed by the small intestine. Other nearby organs include the gallbladder, spleen, and liver. The pancreas has a wid…
Pancreatitis is an inflammation of the pancreas, an organ that is important in digestion. Pancreatitis can be acute (beginning suddenly, usually with the patient recovering fully) or chronic (progressing slowly with continued, permanent injury to the pancreas). The pancreas is located in the midline of the back of the abdomen, closely associated with the liver, stomach, and duodenum (the first par…
A panic attack is a sudden, intense experience of fear coupled with an overwhelming feeling of danger, accompanied by physical symptoms of anxiety, such as a pounding heart, sweating, and rapid breathing. A person with panic disorder may have repeated panic attacks (at least several a month) and feel severe anxiety about having another attack. Each year, panic disorder affects one out of 63 Americ…
The Pap test is a procedure in which a physician scrapes cells from the cervix or vagina to check for cervical cancer, vaginal cancer, or abnormal changes that could lead to cancer. The Pap test is used to detect abnormal growth of cervical cells at an early stage so that treatment can be started when the condition is easiest to treat. This microscopic analysis of cells can detect cervical cancer,…
Papilledema is a swelling of the optic nerve, at the point where this nerve joins the eye, that is caused by an increase in fluid pressure within the skull (intracranial pressure). Swelling of the optic nerve due to other causes such as infection or inflammatory disease is not called papilledema. The optic nerve is the nerve that transmits signals from the eye to the brain. Papilledema is a swelli…
Paracentesis is a procedure during which fluid from the abdomen is removed through a needle. There are two reasons to take fluid out of the abdomen. One is to analyze it. The other is to relieve pressure. Liquid that accumulates in the abdomen is called ascites. Ascites seeps out of organs for several reasons related either to disease in the organ or fluid pressures that are changing. All the bloo…
Paralysis is defined as complete loss of strength in an affected limb or muscle group. The chain of nerve cells that runs from the brain through the spinal cord out to the muscle is called the motor pathway. Normal muscle function requires intact connections all along this motor pathway. Damage at any point reduces the brain's ability to control the muscle's movements. This reduced e…
Paranoia is an unfounded or exaggerated distrust of others, sometimes reaching delusional proportions. Paranoid individuals constantly suspect the motives of those around them, and believe that certain individuals, or people in general, are "out to get them." Paranoid perceptions and behavior may appear as features of a number of mental illnesses, including depression and dementia, b…
The parathyroid hormone (PTH) test is a blood test performed to determine the serum levels of a hormone secreted by the parathyroid gland in response to low blood calcium levels. PTH works together with vitamin D to maintain healthy bones. The parathyroid glands are small paired glands located near the thyroid gland at the base of the neck. The PTH level is measured to evaluate the level of blood …
A parathyroid scan is sometimes called a parathyroid localization scan or parathyroid scintigraphy. This scan uses radioactive pharmaceuticals that are readily taken up by cells in the parathyroid glands to obtain an image of the glands and any abnormally active areas within them. The parathyroid glands, embedded in the thyroid gland in the neck, but separate from the thyroid in function, control …
Parathyroidectomy is the removal of one or more of the parathyroid glands. The parathyroid glands are usually four in number, although the exact number may vary from three to seven. They are located in the neck in front of the Adam's apple and are closely linked to the thyroid gland. The parathyroid glands regulate the balance of calcium in the body. Parathyroidectomy is usually done to tre…
Paratyphoid fever, which is sometimes called Salmonella paratyphi infection, is a serious contagious disease caused by a gram-negative bacterium. It is also grouped together with typhoid fever under the name enteric fever. Enteric fever is increasingly rare in the United States. Of the 500 cases reported in an average year, about 60% are infections acquired during travel in Mexico, India, or South…
Parkinson's disease (PD) is a progressive movement disorder marked by tremors, rigidity, slow movements (bradykinesia), and posture instability. It occurs when cells in one of the movement-control centers of the brain begin to die for unknown reasons. PD was first noted by British physician James Parkinson in the early 1800s. Usually beginning in a person's late fifties or early sixt…
Parotidectomy is the removal of the parotid gland, a salivary gland near the ear. The main purpose of parotidectomy is to remove cancerous tumors in the parotid gland. A number of tumors can develop in the parotid gland. Many of these are tumors that have spread from other areas of the body, entering the parotid gland by way of the lymphatic system. Among the tumors seen in the parotid gland are l…
