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Glossary - M

Displaying glossary terms beginning with the letter M: 1 - 50 of 111 in total
macrocytic anemia
The presence of larger-than-normal red blood cells in circulation?even though there are too few of them?caused by lack of folate and vitamin B12.
macronutrients
Substances that provide energy and that the body needs for growth. The main categories are: fat, carbohydrate, and protein.
macrophage
A type of white blood cell that destroys cell debris, bacteria, and foreign agents.
macula
The area in the center of the retina that produces sharp, clear central vision and allows one to see fine detail.
macular degeneration
An eye disease that slowly destroys sharp, clear central vision.
macular edema
The build-up of fluid in the macula caused by fluid leaking from blood vessels in the eye. It can blur and damage vision.
Magenblase syndrome
Swallowing too much air during a meal, causing excessive gas and great discomfort. Also known as stomach bubble syndrome.
magnetic resonance imaging (MRI)
A scan that creates detailed pictures of internal organs. MRIs use radio waves, a strong magnetic field, and a computer to produce images of organs and internal tissues.
maintenance of wakefulness test
A test to measure sleepiness during the day. A tester measures how long it takes a person who is sitting up in a chair or bed to fall asleep after he or she has been asked to stay awake.
major depression
Depression that interferes with daily life for an extended period. Episodes of major depression during bereavement can be distinguished from normal sadness by such symptoms as persistent feelings of worthlessness, thoughts about death, feelings of guilt, persistent trouble functioning, and marked mental and physical sluggishness.
Related health topics: Bulimia
major histocompatibility complex (MHC) molecule
Molecules that help protect the body from foreign substances. These molecules display proteins on the surface of cells so that protective immune system cells can kill the protein if it is harmful to the body.
maladaptive stress response
An unhealthy physiological response to stressors, in which the stress response often does not turn off even when the stressor disappears
malaise
A general feeling of illness that can be a sign of disease.
Related health topics: End-Stage Renal Disease
malignant
Cancerous.
malignant hypertension
A dangerous type of high blood pressure marked by an unusually sudden rise in blood pressure to very high levels, often accompanied by headache, blurred vision, and seizures.
malnutrition
Failure to eat or to properly absorb the nutrients needed for good health.
mast cell
A cell involved in allergic reactions. When stimulated, it releases chemicals like histamine that signal infection and cause inflammation.
mastoid bone
The bone in the skull behind the ear.
mastopexy (breast lift)
A cosmetic surgery to reshape and lift drooping breasts.
masturbation
Sexual self-stimulation.
maximizer
A person who typically evaluates all options before making a decision, in an effort to identify the perfect choice, and who never settles for second-best.
meal plan
A detailed guide outlining the amounts and types of food a person should eat each day.
Medicaid
A government program that offers health care for low-income Americans of any age.
Medicare
A government program that offers health care for Americans ages 65 and older.
Medigap insurance
Health insurance policies that fill in the holes in Medicare coverage.
medulla
Refers to the middle of something.
megaloblastic anemia
Fewer than normal healthy red blood cells in circulation, caused by a lack of folate or vitamin B12. Red cells become large and deformed, and are unable to carry oxygen efficiently.
meglitinides
A type of medication taken to treat type 2 diabetes.
melanin
A substance that gives the skin, hair, and eyes their natural color.
melanocytes
Cells located deep in the epidermis that produce melanin, the pigment that colors skin.
melanoma
The most dangerous type of skin cancer.
Related health topics: Head and Neck Cancer
melatonin
A hormone that regulates the body's sleep-wake cycle.
membrane
A thin layer of tissue that surrounds or lines organs or cavities.
Related health topics: Endometriosis, Muscular Dystrophy
memory T cells and B cells
Immune cells that remember harmful agents that have entered the body in the past. When they spot the substance again, they spur the immune system to eliminate the invader.
Ménière's disease
An illness caused by a fluid imbalance in the inner ear.
meninges
The three membranes that cover and protect the brain and spinal cord.
meningitis
Swelling of the membranes that cover and protect the brain and spinal cord.
menopause
The point marking the end of menstruation, officially designated as one year after a woman's final period.
metabolic equivalents (METs)
Units used to estimate the oxygen consumption, or metabolic cost, of physical activity, and, hence, its intensity. One MET is the estimated energy cost of the body at rest.
metabolic syndrome
A cluster of risk factors that accelerate the progression of heart disease.
metabolism
The chemical reactions that occur in all living organisms to maintain life. An example is converting food into energy that the body needs to function.
metastasis
The spread of cancer cells from the primary site to another part of the body.
metered-dose inhaler
A device that delivers a specific dose of an inhaled asthma medication.
Related health topics: Chondrosarcoma, Metastatic Brain Tumors
Methanobrevibacter smithii
Bacteria in the gut that help with the digestion of complex sugars.
microalbuminuria
Leakage of small amounts of a protein called albumin into the urine caused by kidney disease or damage.
microaneurysm
A tiny bulge that develops in the wall of a blood vessel.
microbe
A microorganism.
microdermabrasion
A cosmetic procedure in which tiny crystals under high pressure are sprayed on the face. This buffs away the outer layer of skin, eliminates fine lines, and improves the look of the skin.
microgram (mcg)
A unit of mass, equal to one-thousandth of a milligram.
micronized
Reducing a substance to very small particles.