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Meckel's diverticulum
A sac that may form in the small intestine, present at birth.
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meconium
The greenish fecal matter in a fetus, forming the first bowel movement of a newborn infant.
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median nerve
The nerve that stimulates some of the muscles of the hand and wrist.
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mediastinum
The tissues and organs located directly behind the sternum between the lungs. Contains the heart and its large vessels, the…
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medulla
The inner part of an organ. The adrenal medulla is the center of the adrenal gland where epinephrine (adrenaline) is…
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medulla oblongata
The part of the brain just above the spinal cord that includes the control centers for breathing, circulation and…
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meibomian gland
A type of gland of the eyelid’s inner surface. Inflammation of a meibomian gland can produce a swelling called a…
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melancholia
A mental state characterized by extreme sadness. A severe form of depression.
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melanin
A brownish-black pigment normally found in skin, hair and parts of the eye.
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melanoma
A dark-colored tumor, especially malignant melanoma, that is a form of skin cancer that can spread from one part of…
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melasma
Dark coloring of the skin often seen during pregnancy and at menopause. Also occurs in Addison’s disease.
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melena
Black-colored feces caused by the presence of blood.
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membrane
A thin layer of tissue covering an organ.
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menarche
A woman’s first menstrual period.
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Meniere's syndrome
A disorder of the inner ear characterized by dizziness, ringing in the ears and progressive hearing loss.
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meninges
The three membranes covering the brain and spinal cord.
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meningioma
Tumor of the meninges, usually benign and slow-growing.
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meningitis
Inflammation of the meninges as the result of infection by bacteria or viruses. Symptoms include high fever, headache, stiff neck…
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meniscus
The cartilage in the knee joint.
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menopause
The time at which the menstrual cycle gradually stops. Sometimes referred to as the “change of life.”
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menorrhagia
Heavy bleeding during menstruation.