macrophages (MAK-rŏ-fāj): A type of leukocyte (usually a monocyte) that has the ability to ingest and destroy other cells or pathogens.

macule (MAK-ūl): Flat, colored spot on the skin.

magnetic resonance imaging (MRI) (MAG-nĕ-tik RĔZ-ō-năns IM-ă-jing): Radio frequency waves and a strong magnetic field provide clear and detailed pictures of internal organs and tissues.

mainstream smoke (MĀN-strēm smōk): Smoke inhaled by the smoker.

Major Histocompatibility Complex (hĭs-tō-kŏm-păt-ĭ-BĬL-ĭ-tē KOM-pleks): Major Histocompatibility Complex molecules, also called Human Leukocyte Antigen (HLA) are protein structures found on the outside of cells that help the immune system recognize non-self antigens.

malabsorption (mal-ăb-SORP-shŏn): A disorder that occurs when people are unable to absorb nutrients from their diets.

maldigestion (măl-dī-JĔS-chŭn): Poor breakdown of food.

malignant (mă-LIG-nănt): Cancerous.

mammogram (MĂM-ō-grăm): Radiographic image of the breast.

mammography (ma-MOG-ră-fē): Radiographic imaging of the breast.

mammoplasty (MAM-ă-plas-tē): Surgical repair of the breast particularly after a mastectomy.

mast cell: Cell found in the skin and the lining of body cells that contains cytoplasmic granules with vasoactive mediators such as histamine.

mastalgia (mas-TAL-jă): Pain in the breast.

mastectomy (mas-TEK-tŏ-mē): Excision of breast(s) and or breast tissue.

mastitis (mas-TĪT-ĭs): Inflammation of the breast.

mastoidectomy (măs-tŏy-d-ĔK-tō-mē): Excision of the mastoid bone.

mastoiditis (mas-toyd-ĪT-ĭs): Inflammation of the mastoid bone.

mastoidotomy (măs-toyd-ŎT-ō-mē): Incision into the mastoid bone.

mastopexy (MAS-tŏ-pek-sē): Surgical fixation of the breast.

maxillectomy (măks-ĭl-EK-tŏ-mē): Excision of the maxilla.

maxillitis (măks-ĭl-Ī-tĭs): Inflammation of the maxilla.

meatal (mē-ĀT-ăl): Pertaining to the meatus.

meatotomy (mē-ă-TOT-ŏ-mē): Incision into the meatus.

mechanoreceptors (mek-ă-nō-rĕ-SEP-tŏr): A sensory neuron that responds to mechanical pressure.

meconium (mē-KŌ-nē-ŭm): First stool of the newborn.

meconium staining (mē-KŌ-nē-ŭm STĀN-ĭng): When the fetus defecates while in utero; the first defecation is called meconium, it is black and sticky. If the infant inhales the meconium upon delivery or through the birth canal, the meconium can be aspirated into the lungs and stick to the lung tissue. The newborn will have problems breathing and go into distress. The newborn’s umbilical cord will be stained a brownish color.

medial (MĒD-ē-ăl): Describes the middle or direction toward the middle of the body.

medulla oblongata (mĕ-DŬL-ă ob-long-GOT-ă): A part of the brain stem responsible for control of heart rate and breathing. The continuation of the spinal cord within the skull, forming the lowest part of the brainstem, contains the control centers for heart and lung nerve function.

Meissner corpuscle (MĪS-nĕr KOR-pŭs-ĕl): Tactile corpuscle that responds to light and touch, touch receptor.

melanocyte (MĔL-ăn-ō-sīt): Specialized cells that produce melanin which is a dark pigment responsible for colouration of skin and hair.

melanoma (mel-ă-NŌ-mă): Cancer characterized by uncontrolled growth of melanocytes.

melena (mĕ-LĒ-nă): Black tarry stool that contains blood from the GI tract.

memory t cells (MEM-ŏ-rē t sels): Long-lived immune cell reserved for future exposure to an pathogen.

menarche (mĕn-ĂR-kē): Beginning of menstruation.

meninges (mĕ-NIN-jēz): Protective outer coverings of the CNS composed of connective tissue.

meningioma (mĕn-ĭn-jē-Ō-mă): Tumor of the meninges.

meningitis (men-ĕn-JĪT-ĭs): Inflammation of the meninges.

meningocele (mĕn-ĬN-gō-sēl): Protrusion of the meninges.

meningomyelocele (mĕ-nĭng-gō-MĪ-ĕ-lō-sēl): Protrusion of the meninges and spinal cord.

meniscectomy (mĕn-ĭ-SĔK-tō-mē): Excision of the meniscus.

meniscitis (men-ĭ-SĪT-ĭs): Inflammation of the meniscus.

menometrorrhagia (mĕn-ō-mĕt-rō-RĀ-jē-ă): Excessive bleeding from the uterus at menstruation.

menopause (MEN-ŏ-poz): Cessation of menstruation.

menorrhagia (mĕn-ō-RĀ-jē-ă): Excessive bleeding at menstruation.

mental (men-TAL): Pertaining to the brain.

metastasize (mĕ-TĂS-tă-sīz): Production of cells that can mobilize and establish tumors in other organs of the body.

metrorrhagia (mē-trō-RĀ-jă): Excessive bleeding from the uterus.

microcephalus (mī-krō-SĔF-ă-lŭs): Small head.

microglia (mī-KROG-lē-ă): Glial cell type in the CNS that serves as the resident component of the immune system.

micturate (MĬK-tū-rāt): To pass urine.

midbrain (MID-brān): A portion of the brainstem, positioned above the pons, also called mesencephalon, assist in motor reflexes associated with visual and auditory stimuli.

midwife (MĬD-wīf): Individual who practices midwifery.

midwifery (mĭd-WĪF-ĕr-ē): Practice of assisting in childbirth.

mitochondria (mīt-ō-KŎN-drē-ŏn): An organelle found in large numbers in most cells.

mitral valve (MĪ-trăl valv): Also known as the bicuspid valve.

modern-day language term: Terms from the English language.

molecule (MOL-ĕ-kūl): Chemical building block of all body structures.

monocyte (MON-ŏ-sīt): Precursor to macrophages and dendritic cells seen in the blood.

mononeuropathy (mon-ō-noo-ROP-ă-thē): Disease affecting a single nerve.

monoparesis (mon-ō-pă-RĒ-sĭs): Slight paralysis of one (limb).

monoplegia (mŏn-ō-PLĒ-jē-ă): Paralysis of one (limb).

morcellation (mor-sĕ-LĀ-shŏn): Cutting or grinding solid tissue into smaller pieces for removal.

motor nerves: Peripheral, efferent, myelinated nerve tissue that stimulates muscle contraction.

MRI ultrasound fusion biopsy (FŪ-zhŏn BĪ-op-sē): Combination of magnetic resonance imaging with transrectal ultrasound (TRUS) to obtain a tissue from a prostate lesion. The combined MRI-TRUS image is used to direct the biopsy needle into the area of the prostate that looked suspicious on MRI.

mucoid (MŪ-koyd): Resembling mucus.

mucosa-associated lymphoid tissue (malt) (mū-KŌ-să ă-sō-s(h)ē-ĀTE LIM-foyd TISH-oo): Lymphoid nodule associated with the mucosa.

mucosal (mū-KŌ-săl): Mucous membranes line body cavities that open to the outside world, including the respiratory tract, gastrointestinal tract, urinary tract and reproductive tracts.

mucous (MŪ-kŭs): Pertaining to mucus.

mucous membrane (MŪ-kŭs MEM-brān): Composite of connective and epithelial tissues which lines the body cavities and hollow passageways that open to the external environment.

mucus (MŪ-kŭs): Slimy liquid secreted by mucous membranes.

multigravida (mŭl-tĭ-GRĂV-ĭ-dă): Many pregnancies A woman who has been pregnant two or more times regardless of outcome.

multipara (mŭl-TĬP-ă-ră): Many births.

multiple myeloma (MŬL-tĭ-pl mī-ĕ-LŌ-mă): Tumors of the bone marrow.

multipolar (mŭl-tĭ-PŌL-ăr): Shape of a neuron that has multiple processes—the axon and two or more dendrites.

myalgia (mī-AL-j(ē-)ă): Muscle pain.

myasthenia (mī-ăs-THĒ-nē-ă): Weakness of muscles, muscle weakness.

myasthenia gravis (mī-ăs-THĒ-nē-ă grăv-ĭs): Grave or serious muscle weakness.

myelin (MĪ-ĕ-lĭn): Lipid-rich insulating substance surrounding the axons of many neurons, allowing for faster transmission of electrical signals.

myelin sheath (MĪ-ĕ-lĭn shēth): Lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates the transmission of electrical signals.

myeloma (mī-ĕ-LŌ-mă): Tumor in the spinal cord.

myelomalacia (mī-ĕ-lō-mă-LĀ-shē-ă): Softening of the spinal cord.

myelopoiesis (mī-ĕ-lō-poy-Ē-sĭs): Formation of bone marrow.

myocardial infarction (MI) (mī-ŏ-kar′dē-ăl in-FARK-shŏn): heart attack, caused by lack of blood flow and oxygen to the heart.

myocarditis (mī-ŏ-kar-DĪT-ĭs): Inflammation of the muscle of the heart.

myometritis (mī-ō-mē-TRĪ-tĭs): Inflammation of the uterine muscle.

myopia (mī-Ō-pē-ă): Nearsightedness; near objects are clear and seen but far objects are not.

myorrhaphy (mī-OR-ă-fē): Suturing of a muscle.

myringitis (mĭr-ĭn-JĪ-tĭs): Inflammation of the tympanic membrane.

myringoplasty (mĭr-ĬN-gō-plăst-ē): Surgical repair of the tympanic membrane.

myringotomy (mĭr-ĭn-GŎT-ō-mē): Incision into the tympanic membrane.