Dictionary

Body systems

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

hair follicleA small tube-shaped pocket in the skin from which a hair grows.

hallucinationHearing, seeing, feeling, smelling or tasting something that is not really there.

hard palateThe bony front part of the roof of the mouth.

Hashimoto thyroiditisAn autoimmune disease in which the immune system attacks the thyroid gland, slowly reducing its hormone output.

head and neck cancerCancer that starts in the mouth, throat, voice box, nose, sinuses or salivary glands.

heart diseaseA general term for any condition that affects the structure or function of the heart.

heart failureA long-term condition in which the heart cannot pump enough blood to meet the body's needs.

heart murmurA whooshing or swishing sound heard with a stethoscope, made by blood flowing unevenly through the heart.

heart rateHow many times the heart beats per minute.

heartburnA burning feeling behind the breastbone or in the upper belly, often rising toward the throat.

heavy metalA dense metal, such as lead, mercury or arsenic, that can poison the body even in small amounts.

HELLP syndromeA severe complication of pregnancy whose name stands for hemolysis, elevated liver enzymes and low platelets.

hematemesisVomiting blood, either bright red or dark and grainy like coffee grounds.

hematomaA collection of blood, often clotted, that has leaked out of the blood vessels into the tissue.

hematuriaBlood in the urine, either seen by eye or found only by a test.

hemiplegiaParalysis of one side of the body.

hemodynamicsThe study and measurement of blood flow and the pressures that move blood through the heart and vessels.

hemoglobinThe iron-containing protein in red blood cells that carries oxygen, and the blood test that measures it.

hemolysisThe breaking apart of red blood cells, which releases hemoglobin into the blood.

hemophiliaAn inherited disorder in which the blood lacks a clotting factor, so it does not clot normally.

hemoptysisCoughing up blood or blood-streaked mucus from the lungs or airways.

hemorrhageA large loss of blood from a blood vessel, inside the body or out of it.

hemorrhoidA swollen vein in or around the anus or lower rectum.

hemostasisThe stopping of bleeding, either by the body's own clotting process or by medical or surgical methods.

hepaticRelating to the liver.

hepatitisInflammation of the liver, most often caused by a virus.

hepatitis BA liver infection caused by the hepatitis B virus.

hepatitis B virusThe virus that causes hepatitis B, an infection of the liver.

hepatitis CAn infection of the liver caused by the hepatitis C virus.

hepatomegalyAn enlarged liver.

herniaA bulge of an organ or tissue through a weak spot in the muscle or tissue wall that normally holds it in.

herniationThe bulging or pushing of an organ or tissue through an opening or weak spot into a place where it does not belong.

herpes simplex virusA common virus that infects the skin and lining of the mouth or genitals and stays in the body for life.

HHSHyperosmolar hyperglycemic state: very high blood glucose with severe dehydration and little or no ketone buildup.

high blood pressureThe everyday name for hypertension: blood pressure that stays higher than normal.

hip fractureA break in the upper part of the thigh bone, near the hip joint.

Hirschsprung diseaseA condition present at birth in which a section of the large intestine has no nerve cells to move stool along.

hirsutismThick, dark hair growing in a male-type pattern, such as on the face, chest or back, in a woman.

histamineA chemical released by certain immune cells that widens blood vessels, makes them leaky and tightens airway muscles.

histologyThe study of body tissues under a microscope.

HITHeparin-induced thrombocytopenia: an immune reaction to heparin that lowers the platelet count.

HIVHuman immunodeficiency virus: a virus that infects and destroys immune cells called CD4 T cells.

HIV/AIDSHuman immunodeficiency virus infection and acquired immunodeficiency syndrome, its most advanced stage, written together.

hoarsenessA rough, strained or breathy voice that is harder to make or sounds different from normal.

Hodgkin lymphomaA cancer of the lymphatic system that starts in white blood cells called lymphocytes and has large abnormal cells called Reed-Sternberg cells.

homeostasisThe body's way of keeping its inside conditions, such as temperature, fluids and blood sugar, steady.

hopelessnessA feeling that things will not get better and that nothing a person does can change that.

hormoneA chemical messenger made by a gland or organ and carried in the blood to act on cells elsewhere in the body.

hormone replacement therapyTreatment with hormones, usually estrogen with or without a progestin, to replace hormones the body no longer makes enough of.

human papillomavirusA common group of viruses spread by close skin-to-skin contact, most often during sex.