Medical Dictionary: C

calcifications: Small calcium deposits in breast tissue that can be seen by mammography.

calcium: A mineral that is the primary component of hydroxyapatite. It is also vital to many physical processes, including heart rate, blood pressure, muscle contractions, the transmission of nerve signals, and the regulation of internal organs.

callus: An area of hardened skin that usually forms on the bottom of the feet to protect against irritation.

calorie: The unit for measuring the amount of energy in food.

carbohydrate counting: A meal-planning method that relies on tracking grams of carbohydrate intake.

carbohydrate: The major component in fruits, milk, and starches such as bread, pasta, rice, and potatoes. Carbohydrates are one of the three primary nutrients (along with fats and proteins) and provide most of your body’s fuel.

carbon monoxide: An odorless, colorless gas that results from combustion. Produced by cars, furnaces, gas stoves, fireplaces, and other equipment and appliances commonly found in the home.

carcinoma: Cancer that arises from epithelial tissue (tissue that lines a cavity or surface); occurs often in the breast.

carminative: A digestive agent that traditionally is believed to support the digestive system, relieving gas and abdominal discomfort.

carotenoids: Plant and animal pigments that color many fruits and vegetables, including carrots and cantaloupe. Some carotenoids can be converted to vitamin A.

carotid artery: One of two major vessels, on either side of the neck, that supplies blood to the brain; each one divides into external and internal carotid arteries, which carry blood to the face and neck and the front part of the brain, respectively.

carotid bruit: An abnormal sound heard with a stethoscope in the carotid artery; people who have carotid bruits have a greater risk of having a stroke.

carotid duplex Doppler scanning: An ultrasound technique that makes images of the carotid arteries.

carotid endarterectomy: A surgical procedure that removes plaque from the carotid artery and restores blood flow to the brain.

carpal tunnel syndrome: a condition in which the median nerve is compressed as it passes through a narrow space within the wrist, called the carpal tunnel.

cartilage: a type of connective tissue that protects and cushions the ends of bones.

cartilaginous joint: A joint that contains a tough cartilage plate that permits slight movement.

cataplexy: Sudden paralysis of some or all muscles brought on by laughter, anger, or strong emotions; a hallmark of narcolepsy.

cataract: A clouded lens in the eye that distorts or blocks light before it reaches the retina, causing blurred or lost vision.

cathartic: An agent with a strong laxative effect.

catheter: A hollow, flexible tube used to add or remove fluid to or from the body, commonly inserted into the bladder through the urethra.

cauda equina: The bundle of nerve fibers that starts at the top of the small of the back and continues to the bottom of the spinal canal. This bundle of nerves is called cauda equina because it resembles a horse’s tail.

cell senescence: The end stage in the life of a cell during which replication ceases.

central nervous system: The brain, brainstem, and spinal cord.

central sleep apnea: Sleep apnea caused when respiratory control centers in the brain fail to activate breathing muscles.

cerebral angiography: An invasive imaging procedure used to make detailed x-ray pictures of the blood vessels in the brain; dye is injected into the carotid arteries to highlight the blood vessels on x-rays.

cerebral cortex: The outer layer of gray matter surrounding the cerebrum that carries out all aspects of higher brain function including thought, memory, sensation, and voluntary movement.

cerebral hemorrhage: Another term for hemorrhagic stroke.

cerebral infarction: The death of part of the brain from a lack of oxygen-carrying blood.

cervical radiculopathy: Compression of the spinal nerve roots in the neck, causing neurological symptoms such as tingling and numbness in the areas served by the nerves.

cervical spine: The portion of the spine located in the neck and consisting of the top seven vertebrae.

cervical spondyloarthropathy: A type of inflammatory arthritis involving the neck portion of the spine.

cervicogenic headache: Headache related to neck problems. Also called cervical headache.

challenge testing: A method of testing for food allergy, usually in double-blind experiments in which neither patient nor doctor knows which food is taken in a pharmaceutically prepared pill.

chemical peel: Use of mild to strong chemical solutions to wound the outer layer of the epidermis and encourage new collagen growth.

chemonucleolysis: A treatment for low back pain that involves injecting the enzyme chymopapain into a herniated disk to dissolve the nucleus pulposus.

chemoprevention: The use of drugs or chemicals to prevent cancer.

chemoprevention: Using drugs or chemicals to prevent cancer.

chemotherapy: Treatment of cancer with drugs that destroy cancer cells.

cholagogue: An agent that is traditionally believed to contract the gallbladder, leading to bile secretion.

choleretic: An agent that promotes bile production.

cholesterol: A fatlike substance that is produced by the liver and found in all food from animal sources; an essential component of body cells and a precursor of bile acids and certain hormones.

chondrocalcinosis: Arthritis caused by calcium crystals.

chondromalacia: Softening or wearing away of the articular cartilage, common in the knee joint on the underside of the patella.

chronic fatigue syndrome (CFS): A disorder characterized by at least six months of fatigue, together with impaired concentration or memory and other symptoms.

chronic kidney disease: An umbrella term for any type of kidney disease that lasts longer than three months and impairs kidney function; in some cases will progress to kidney failure.

chronic pain: Pain that persists after an injury has healed or a disease is over.

chylomicron: A large, extremely low-density lipoprotein that transports triglyceride from the intestine to fat tissue in the body.

chyme: A nearly liquid mass of partly digested food and secretions in the stomach and intestine.

circadian rhythm: The innate biological clock that regulates sleep and waking and controls the daily ups and downs of physiologic processes, including body temperature, blood pressure, and the release of hormones.

Circle of Willis: A group of arteries at the base of the brain that supplies blood to all parts of the brain and provides collateral routes for blood flow if a major vessel becomes blocked.

clinical trial: A study that tests a therapy in humans, rather than in laboratories or on animals.

clonal expansion: The rapid and repeated duplication of B and T cells upon recognition of their specific antigens; this process generates the voluminous fighting forces of adaptive immunity.

cluster headache: A severe headache on one side of the head, occurring as part of a series of similar attacks and lasting for an hour or two.

cochlea: A snail-shaped structure in the inner ear where sound is changed into nerve impulses that the brain can interpret as a particular sound.

cochlear implant: An electronic device that is implanted in the inner ear to restore some hearing to a deaf person.

cognitive behavioral therapy: A form of therapy that aims to correct ingrained patterns of negative thoughts and behaviors.

cognitive function: All of the brain mechanisms involved with thinking, reasoning, learning, and remembering.

cognitive impairment: Problems in mental function, including intelligence, judgment, learning, memory, speech, and thinking. Cognitive impairment that affects judgment, visual-spatial coordination, and the ability to process new information quickly can increase the risk of various accidents.

collagen: A fibrous protein that’s the main component of connective tissue.

Colles fracture: a fracture across the end of the main bone of the forearm, the radius.

colon: The large intestine, a muscular tube 5–6 feet long that compacts and moves solid waste.

colonoscopy: A method of viewing the entire colon by way of a long, flexible probe with a tiny scope at the end. Used to look for polyps as well as to remove them.

colostomy: Surgery that routes the colon to an opening in the abdomen for elimination of stool.

combined hormone therapy: Estrogen combined with progestogen.

combined hyperlipidemia: A condition in which LDL and triglyceride levels are very high.

combined hyperlipidemia: A condition in which LDL and triglyceride levels are very high.

compact bone: Very dense bone tissue that forms the outer shell of bones and composes a large part of the long bones of the arms, legs, and ribs. Also called cortical bone or lamellar bone.

complement system: A family of proteins that flag viruses, bacteria, and other microbes for destruction by the phagocytes (the “gobblers”). These proteins can also kill microbes directly.

compression fracture: The collapse of a bone, most often a vertebra.

computed tomography (CT) scan: An imaging procedure in which a computer combines a series of x-rays to produce extremely detailed, cross-sectional views of the body and brain.

conductive hearing loss: Hearing loss caused by a blockage in the middle ear that prevents sound waves from passing through to the inner ear.

condyle: One of the bony knobs of the knee joint located at the lower end of the femur.

cones: Specialized cells in the retina that are sensitive to color and light; they are more active in light than in the dark, provide sharp vision, and are abundant in the macular area of the retina.

congestive heart failure: A condition that results from decreased blood flow to muscle tissues and organs throughout the body. Ineffective pumping of the heart also causes blood to back up into the veins that return blood to the heart. Blood backs up into the lungs, which become congested with fluid. Hyperthyroidism can precipitate it and hypothyroidism can contribute to it. May also lead to the accumulation of fluid in the lower legs or abdomen, resulting in shortness of breath, weakness, fatigue, or swelling.

conjugate vaccine: A type of hybrid subunit vaccine important for the immunization of children under age 5.

conjugated equine estrogens: Estrogen compounds produced from the urine of pregnant mares. Brand name is Premarin.

conjunctiva: The transparent membrane that lines the eyelid and covers the front portion of the sclera.

conjunctivitis: Inflammation of the conjunctiva of the eye. Conjunctivitis is the most common eye allergy.

connective tissue: The material that holds various body structures together; cartilage, tendons, ligaments, and blood vessels are composed entirely of connective tissue.

consolidation: The second step in memory formation, in which the brain transforms newly acquired information into long-term memories.

contact dermatitis: A reaction that occurs when the skin comes in direct contact with an allergen or an irritant.

continuous combined hormone therapy: A dose of estrogen and a dose of progestogen taken daily.

continuous positive airway pressure (CPAP): A treatment for sleep apnea in which a continuous stream of air is delivered through a mask worn over the nose to keep the sleeper’s airway open.

controllers: Asthma medications taken on a daily basis to prevent or control asthma symptoms.

core needle biopsy: Use of a hollow needle to extract a sample of a lump or other suspicious tissue for examination.

corn: An area of hardened skin that might have a dense knot in the center. Corns usually form on the toes because of irritation.

cornea: The curved, transparent dome of tissue at the front of the eye, through which light first passes on its way into the eye.

coronary arteries: The small blood vessels that carry oxygen-rich blood to the heart muscle.

coronary arteriography: An x-ray procedure that shows blood moving through the blood vessels and heart. It involves the injection into the bloodstream of a fluid (contrast agent) that can be seen on the x-ray. Also known as coronary angiography; the resulting image is called an angiogram.

coronary artery bypass surgery: Surgery that bypasses a blocked coronary artery by grafting a blood vessel taken from another part of the body to restore blood flow to the heart muscle.

coronary artery disease: A condition in which one or more of the arteries feeding the heart become narrow enough in spots to reduce or entirely interrupt blood flow. Often called “heart disease.” The condition can cause angina and heart attack.

corpora cavernosa: Two columns running the length of the penis that can fill with blood and become rigid, producing an erection.

corrugator muscle: One of the muscles that forms frown lines on the mid-forehead.

corticosteroids: A family of medications designed to reduce inflammation commonly used to treat a range of allergies. These anti-inflammatory drugs are often referred to as “steroids,” but are different from the muscle-building steroids used illegally by some competitive athletes.

corticotropin-releasing factor (CRF): A hormone secreted by the hypothalamus that helps rouse the body to defend against a physical or emotional threat.

corticotropin-releasing hormone (CRH): A hormone secreted by the hypothalamus that helps rouse the body when a physical or emotional threat appears.

cortisol: A glucocorticoid, or steroid hormone, released by the adrenal glands and necessary to many basic body functions. This stress hormone is also involved in triggering the “fight or flight” response and similar responses.

COX-2 inhibitors: A class of anti-inflammatory drugs that focuses on the form of cyclooxygenase enzyme known as COX-2, which is believed to be at the root of inflammation and pain.

C-reactive protein (CRP): A by-product of inflammation.

creatine kinase: An enzyme produced by skeletal tissue and heart muscle. One form, creatine kinase-MB, is produced only by the heart; it’s usually elevated only when there has been damage to heart tissue — for example, because of a heart attack. A blood test for this enzyme can aid in the diagnosis of heart attack.

creatinine test: A urine test for creatinine that is more sensitive than routine urinalysis at detecting kidney problems.

creatinine: A waste product of muscle metabolism and meat digestion.

crepitus: Grinding sensation or sound when a joint (especially the kneecap) is moved.

crystalline lens: A flexible, transparent structure directly behind the iris that focuses rays of light onto the retina.

CT angiography (CTA): High-speed CT scanning, which enables doctors to determine the type of stroke and its pathology.

cubital tunnel syndrome: a condition in which the ulnar nerve is compressed at the elbow.

cyclic guanosine monophosphate: One of several chemicals that helps cause an erection by widening blood vessels in the penis to let blood in.

cyclic hormone therapy: Continuous treatment with estrogen combined with a progestogen for 10–14 days of the month.

cyst: A lump or swelling filled with fluid or semifluid material.

cytokines: Proteins, hormones, and other molecules produced by many cells of the body that act as messengers in the immune system.