Dictionary

Body systems

Anatomy and the conditions of each body system, from the heart and lungs to the skin.

abdomenThe part of the trunk between the chest and the pelvis, holding the stomach, intestines, liver and other organs.

abdominalHaving to do with the abdomen, the part of the body between the chest and the pelvis; the belly.

abdominal aortic aneurysmA weak, bulging section of the aorta where it passes through the belly.

abductionMoving a limb or part away from the midline of the body, such as raising an arm out to the side.

abrasionA scrape: a wound where the top layer of skin has been rubbed or worn away.

abruptio placentaeEarly separation of a normally placed placenta from the wall of the uterus, before the baby is born.

abscessA closed pocket of pus in tissue, walled off by the body.

absorptionThe taking in of a substance, such as a drug or a nutrient, into the bloodstream.

accommodationThe eye's ability to change its focus from distant objects to near ones.

acetylcholineA chemical messenger that nerves release to signal muscles, glands and other nerves.

Achilles tendonThe thick tendon at the back of the ankle that joins the calf muscles to the heel bone.

acid-base balanceThe body's control of how acidic or alkaline the blood is, keeping its pH in a narrow normal range.

acidosisA state in which the blood is more acidic than normal, with a pH below 7.35.

acneA skin condition in which hair follicles become clogged with skin oil and dead skin cells.

acromegalyA rare hormone disorder in adults in which the body makes too much growth hormone.

acromionThe bony tip of the shoulder blade that forms the top of the shoulder.

actinA protein that forms thin threads inside muscle cells and works with myosin to make a muscle contract.

acuteStarting suddenly and lasting a short time; also used for something severe or sharp.

acute coronary syndromeA group of conditions in which blood flow to the heart muscle is suddenly reduced or blocked.

acute glomerulonephritisSudden inflammation of the glomeruli, the tiny filters in the kidneys.

acute kidney injuryA sudden loss of kidney function over hours to days.

acute lymphoblastic leukemiaA fast-growing cancer of the blood and bone marrow in which too many immature lymphocytes are made.

acute pancreatitisSudden inflammation of the pancreas, in which its own digestive enzymes start to damage it.

acute respiratory distress syndromeA sudden, severe lung injury in which fluid leaks into the air sacs, so the lungs cannot get enough oxygen into the blood.

adaptationA change that helps a person or the body adjust to new conditions or stress.

addictionA long-term condition in which a person keeps using a substance or doing a behavior despite the harm it causes.

Addison diseaseA condition in which the adrenal glands do not make enough cortisol and often not enough aldosterone.

adductionMoving a limb or part toward the midline of the body, such as bringing an arm back down to the side.

adenomaA tumor of gland tissue that is not cancer.

adhesionA band of scar tissue that joins two surfaces inside the body that are normally separate.

adipose tissueBody fat: connective tissue made mostly of fat cells that store energy.

adolescentA young person in the stage between childhood and adulthood, roughly ages 12 to 18.

ADPAdenosine diphosphate: the molecule left when ATP gives up one phosphate to release energy in a cell.

adrenalHaving to do with the adrenal glands, the two small glands that sit on top of the kidneys.

adrenal cortexThe outer layer of each adrenal gland, which makes the steroid hormones cortisol and aldosterone.

adrenal glandOne of two small glands that sit on top of the kidneys and make hormones such as cortisol, aldosterone and epinephrine.

adrenal medullaThe inner part of each adrenal gland, which releases epinephrine and norepinephrine.

adrenocorticotropic hormoneA hormone from the pituitary gland that tells the adrenal glands to make cortisol.

affectIn mental health, the outward expression of a person's emotions, as seen in the face, voice and body language.

affectiveRelating to feelings, emotions or mood.

afferentCarrying something toward a center or organ, such as nerve signals toward the brain.

afterloadThe resistance the heart's ventricles must push against to send blood out into the arteries.

afterpainCramping pain in the lower abdomen after childbirth as the uterus contracts and shrinks.

agranulocytosisA severe drop in granulocytes, the white blood cells that fight bacterial infection, mainly neutrophils.

AIDSAcquired immunodeficiency syndrome: the most advanced stage of HIV infection, when the immune system is badly damaged.

airwayThe passages that carry air into and out of the lungs, from the nose and mouth to the smallest air tubes.

Alcoholics AnonymousA worldwide, free self-help group in which people with drinking problems support each other to stop drinking.

aldosteroneA hormone from the adrenal glands that makes the kidneys keep sodium and water and get rid of potassium.

alkalosisA state in which the blood is less acidic than normal, with a blood pH above 7.45.

allergenA substance that triggers an allergic reaction in a person whose immune system is sensitive to it.