Health A-Z


Clinical Definition The original definition of a calorie was the quantity of heat needed to raise the temperature of 1 kilogram of water from 0 to 1 degree Celsius. Now, it is commonly used as a unit for measuring the amount of energy contained in food. In Our Own Words A calorie is the unit


Clinical Definition Cancer is not a single disease, but the general name that applies to more than 100 diseases. Each cancer has in common abnormal cells that grow in an uninhibited way and in the process, possibly forming tumors (i.e., abnormal growth of tissue). Cells become cancerous due to deoxyribonucleic acid (DNA) damage. In every

Canker Sore

Clinical Definition Canker sores, also known as aphthous ulcers, are painful oral sores that are typically red in color but sometimes with a white, yellow or gray center. Traditionally less than a millimeter in diameter, they appear on the inside of the lips, inside the cheeks, under the tongue or at the base of the


Clinical Definition This macronutrient is an organic compound that is made up of carbon, hydrogen and oxygen molecules. The structure of the molecules dictates whether it is a monosaccharide (glucose, galactose and fructose), disaccharide (sucrose, lactose and maltose) or polysaccharide (starch and glycogen). In Our Own Words Carbohydrates are nutrients the body needs in relatively


Clinical Definition A carcinogen is an agent or substance that may damage cellular DNA or alter cell metabolism, and, in so doing, potentially lead to the development of cancer. Carcinogens are classified according to their carcinogenicity. In Our Own Words A carcinogen is something believed to contribute to the development of cancer. Usually, a carcinogen

Caregiver Stress

Clinical Definition Caregiver’s stress is a state of exhaustion – physical, mental and emotional – that occurs when those who attend to others with chronic medical conditions do not get the help they need, or stretch themselves too thin physically or financially. When anxiety progresses to a feeling of recurring burnout, research shows that caregivers’

Carpal Tunnel Syndrome

Clinical Definition Carpal tunnel syndrome is a compression neuropathy that occurs when increased pressure of the median nerve in the proximal forearm develops. The median nerve, which extends from the forearm to the hand, provides motor and sensory function to the thumb and three of the fingers. When compression occurs, hand function can be compromised.


Clinical Definition Cataplexy is an acute, transient attack characterized by hypertonia and weakness. Weakness can be generalized or limited to certain muscle groups. Precipitating factors associated with cataplexy are intense emotional stimuli, such as anger and fear. A decrease in hypocretin, which is a neurotransmitter, is believed to be a contributing factor to cataplexy. Cataplexy


Clinical Definition Normally, the lens in the eyes are clear or transparent. However, a cataract is an abnormal clouding or opacity of the eye’s crystalline lens. The opacity can lead to a decrease in vision and possibly blindness. Cataracts are thought to develop as a result of age-related degenerative alterations to the proteins in the


Clinical Definition A cavity is the progressive demineralization of the structure of the tooth, causing a hollow space. Acid from dental plaque damages the tooth and leads to destruction of the tissue. A cavity starts by invading the enamel, but can progress into deeper structures including the dentin and cementum. In Our Own Words A cavity

Celiac Disease

Clinical Definition Celiac disease is a digestive, autoimmune disorder characterized by intolerance to gluten, a protein found in wheat products and other foods. When gluten is ingested, the immune system forms antibodies that bind to parts of the villi of the small intestine, resulting in inflammation, damage to the intestine and malnutrition. In Our Own

Cervical Cancer

Clinical Definition Cervical cancer originates in the uterine cervix, and is primarily either squamous cell carcinoma or adenocarcinoma. The majority are squamous cell carcinomas, although some have characteristics of both types and are known as mixed carcinoma. Early symptoms are atypical. Risk factors include lack of screening with a Pap smear, infection with human papillomavirus

Chagas Disease

Clinical Definition Chagas disease is an infection transmitted by insects, caused by the parasite Trypanosoma cruzi and common in South and Central America. In acute phases, symptoms may be non-existent or mild, such as fever and malaise. In the chronic phase, which may take 20 years to develop, arrhythmias, tachycardia and enlarged lymph nodes may occur. In

Chemo Brain

Clinical Definition Chemo brain is the mild cognitive impairment experienced by some cancer patients pre-treatment, during and post-treatment. Characteristics include memory lapses, concentration difficulties and difficulty multi-tasking.  Some researchers have found alterations in brain activity patterns on electroencephalograms (EEGs) in those on chemotherapy. Coping focuses on organizational techniques, sleep hygiene and exercise, as well as


Clinical Definition Chemotherapy refers to chemicals used to treat cancer, and commonly involves use of antineoplastic drugs used to treat neoplastic disease. The drugs have a cytotoxic effect on cancer cells. Chemotherapy is often used as a systematic treatment for various forms of malignant neoplasms. In Our Own Words Chemotherapy is a form of cancer


Clinical Definition Cholesterol is a fat-like substance produced by the liver; it is also an animal sterol found in all foods from animal products. While it is an essential cellular component, cholesterol can cause atherosclerosis (i.e., arterial plaque buildup) when too much exists in the blood stream, leading to heart disease and stroke. In Our

Chronic Cough

Clinical Definition Chronic cough, or persistent cough, is a cough that persists more than eight weeks. Not a disease itself, it originates from other health conditions, typically related to asthma, smoking, gastroesophageal reflux disease (GERD), sinusitis and other problems. Treatment depends on the etiology. In Our Own Words Chronic cough is one that lasts a

Chronic Obstructive Pulmonary Disease

Clinical Definition COPD, or chronic obstructive pulmonary disease, is a term used to refer to a group of diseases, including emphysema and chronic bronchitis. All these diseases involve airflow obstruction and breathing-related problems. The typical course of COPD is gradual progression, with airflow lung function worsening. Because COPD adds to the work of the heart,


Clinical Definition Claustrophobia is a persistent, irrational fear of enclosed spaces. The phobia, a type of anxiety disorder, triggers reactions and anxiety symptoms such as dizziness, nausea and tachycardia, which results in avoidance of situations or objects that trigger it. Desensitization, medication and cognitive therapy can help. In Our Own Words Claustrophobia is fear of

Cluster Headache

Clinical Definition Cluster headaches appear to be associated with activity in the hypothalamus, the brain region that houses the circadian clock and the trigeminal nerve. Though not nearly as common as tension headaches or migraines, cluster headache pain can last anywhere from 15 minutes to three hours or so. The trigeminal nerve triggers the ocular


Clinical Definition Colitis is a medical condition that exhibits inflammation of the colon, whether caused by an inflammatory bowel disease, infection, or some other process. In Our Own Words Colitis is characterized by inflammation of the colon. There are many different kinds of colitis, including infectious colitis, ulcerative colitis, diverticular colitis, and radiation colitis. In

Common Cold

Clinical Definition The common cold is a viral infection of the upper respiratory tract, usually involving a sore throat, runny nose, sneezing and coughing. Symptoms often last for up to two weeks. In Our Own Words More than 200 different viruses are known to cause the common cold, but most often, it’s a rhinovirus. When


Clinical Definition A concussion is a type of traumatic brain injury or TBI that can alter the usual and normal functioning of the brain. Concussions are caused by a jolt, blow or bump to the head, often during sports, and this can trigger headaches, dizziness and neck pain. Concussions are considered mild brain injuries, but


Clinical Definition Congestion is an excessive accumulation of bodily fluids, such as mucus or blood, in an organ, vessel or body part. It may develop in a part of the body due to obstruction in normal fluid movement or an increased influx of fluid. The term most commonly refers to nasal congestion, but can also

Congestive Heart Failure

Clinical Definition Congestive heart failure refers to a decrease in the heart’s ability to pump blood, which in turn is associated with congestion and edema in the tissues, potentially including the lungs. Heart failure may be associated with symptoms such as shortness of breath, edema, vein distension in the neck’s (jugular) veins or an enlarged


Clinical Definition Contamination is the presence of an unwanted or harmful agent, such as bacteria. Contamination may involve the body or inanimate objects (e.g., surgical instruments, bandages or dressings). Food and liquids can also become contaminated. In some instances, contamination may lead to an infection or illness. In Our Own Words Contamination is the introduction


Clinical Definition Coronavirus is a genus in the family Coronaviridae. It is a causative agent of upper respiratory tract infections, which may range from the common cold to severe acute respiratory syndrome (SARS). Less commonly, coronavirus may also cause gastroenteritis, pancreatitis and infectious peritonitis. It may be transmitted through inhalation of respiratory droplets from an


Clinical Definition Corticosteroids are synthetic compounds that produce physiological effects similar to the chemicals produced by the human adrenal cortex. Corticosteroids decrease the inflammatory process and the immune system response, which may have a therapeutic effect on a variety of diseases. In Our Own Words Corticosteroids are a type of medication made to induce some

CPAP Machine

Clinical Definition A CPAP machine is a medical device that delivers continuous positive airway pressure to the airways. It prevents alveoli collapse during exhalation and increases functional residual capacity in the lungs. In Our Own Words CPAP stands for continuous positive airway pressure, and a CPAP machine can treat certain types of breathing disorders. It

Creutzfeldt-Jakob Disease

Clinical Definition Creutzfeldt-Jakob disease is a rare neurodegenerative disease that occurs due to prion proteins, which are even smaller than viruses. The disease is classified as a spongiform encephalopathy due to the formation of vacuoles in the gray matter of the brain. The condition causes rapid deterioration of brain function and is fatal. There are

Crohn’s Disease

Clinical Definition Crohn’s disease is a chronic, inflammatory disease of the gastrointestinal tract most often in the ileum and large intestine. Inflammation can lead to abscesses and ulcers, and chronic symptoms may result in fibrosis, stenosis and bowel obstruction. In Our Own Words Crohn’s disease is an inflammatory gastrointestinal disease of unknown cause that affects

View Terms Beginning with "D"