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Glossary - H

Displaying glossary terms beginning with the letter H: 1 - 50 of 98 in total
hair bulb
The root of the hair shaft.
hair cells
Cells in the ear that transmit sound messages to the brain and play a vital role in hearing.
hair shaft
The portion of hair that extends beyond the surface of the skin. It contains three layers: the cuticle, cortex, and medulla (not always present).
hallucination
A perception of something that is not really there.
hammertoe
A sometimes painful condition in which the toe curls up and under (resembling a hammer).
happiness
Feelings of contentment or joy; the overall experience of pleasure and meaning in life.
happiness set-point
An individual's baseline level of happiness, determined largely by genetics, around which moods fluctuate. After reacting to positive or negative life changes, people tend to return to their happiness set-points.
harm reduction therapy
A treatment strategy aimed at minimizing the harm associated with an object of addiction. This strategic approach helps people learn how to limit the degree to which they use their object of addiction, or limit the risks associated with their use, but they do not necessarily stop altogether.
Hashimoto's thyroiditis
A disease in which the body's immune system prevents the thyroid gland from producing enough thyroid hormone.
hay fever
A commonly used term for allergic rhinitis?seasonal or year-round allergic condition marked by sneezing, runny nose, and congestion. The most common type of allergy, it is caused by an IgE-mediated immune response to inhaled airborne allergens.
Related health topics: Eczema
HDL
Abbreviation for high-density lipoprotein, the so-called good cholesterol. This lipoprotein (a substance made up of fats and protein) is believed to remove cholesterol from the arteries.
health care proxy
A legal form allowing a person to appoint someone else to make their medical decisions. Also known as a durable power of attorney for health care.
hearing aid
An electronic device worn in or behind the ear by people with hearing problems that makes sounds louder.
heart attack
The common term for a myocardial infarction. It refers to the damage that occurs when blood flow to part of the heart is blocked or drastically restricted. The blockage usually stems from the rupture of an atherosclerotic plaque.
heart block
The difficulty or inability of the electrical signal that triggers a heart contraction to pass through the atrioventricular node.
heart failure
The inability of the heart to pump enough blood to meet the needs of the body's organs.
heart murmur
An extra or unusual sound heard during the heartbeat. A murmur may or may not be a sign of a problem in the heart.
Related health topics: Hemolytic Anemia, Marfan's Syndrome
heart rate
The number of times the heart contracts in a minute, normally 60?100 times.
Related health topics: Generalized Anxiety Disorder
heartburn
A burning pain in the chest or throat, caused when stomach acid backs up into the esophagus.
Related health topics: Esophageal Cancer
Heberden's nodes
Bony bumps found on the finger joints in some people with osteoarthritis.
hedonic
Devoted to pleasure.
hedonic treadmill
The human tendency to adapt to new circumstances and come to consider them normal, so the emotional effects (negative or positive) generated by a change fade over time.
heel spur
An abnormal growth of bone or calcium on the heel bone.
Helicobacter pylori (H. pylori)
Bacteria that damages the lining the stomach. It is to blame for most ulcers and stomach inflammation.
helper T cells
Cells that help fight disease by activating and directing other immune system cells.
hematemesis
The vomiting of bright red blood, indicating bleeding in the upper digestive tract.
hematoma
Blood that leaks out of blood vessels and collects in the body.
hematuria
Blood in the urine.
hemianopia
Poor vision or blindness in half of the visual field, affecting one or both eyes
hemiparesis
Muscle weakness on one side of the body.
hemiplegia
Paralysis on one side of the body.
hemochromatosis
A genetic condition in which the body absorbs and stores too much iron.
hemodialysis
The use of a machine to remove wastes and impurities from the blood when the kidneys are not working properly.
Related health topics: Hepatitis C
hemoglobin
The oxygen-carrying substance that gives red blood cells their color.
hemoptysis
Coughing up or spitting up blood from the lungs.
hemorrhage
Bleeding from a damaged blood vessel.
Related health topics: Head Injury In Children
hemorrhagic stroke
A type of stroke that occurs when a blood vessel leaks or bursts inside the brain, cutting off the supply of oxygen and nutrition to that part of the brain.
HEPA filter
A high-efficiency air filter.
heparin
A drug that prevents blood from clotting.
herd immunity
Protection that occurs when so many people in a community are immune to an infectious disease that the disease can't spread to others.
herniated disk
When part of a spinal disk bulges out of a tear or weak spot in the disk's tough outer shell. Also known as prolapsed disk.
herpes zoster
A painful blistering skin rash caused by the chicken pox virus; also known as shingles.
hertz
The measurement of a sound's frequency.
hiatal hernia
When part of the stomach pushes upward into the chest through an abnormal opening in the diaphragm.
high blood pressure
When blood flowing through arteries pushes on artery walls with abnormally high force over a sustained period of time. Also called hypertension.
high-density lipoprotein (HDL)
So-called good cholesterol. This lipoprotein (a substance made of fat and protein) removes cholesterol from arteries.
high-intensity focused ultrasound (HIFU)
A treatment that destroys tumors with heat generated by ultrasound energy.
hippocampus
Part of the brain that plays an important role in processing long-term memories.
Related health topics: Generalized Anxiety Disorder
hirsutism
Excessive facial or body hair in women.
histamine
A substance released by the immune system when it is exposed to an allergen. Histamines cause many allergy symptoms.