Definitions and descriptions

Definitions and descriptions

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There are currently 108 terms in this directory beginning with the letter M.
Macrophage (MAK-roh-fahj)
A phagocytic cell derived from monocytes that contributes to both innate and adaptive immunity. Capable of phagocytosis of pathogens, dead or damaged cells, and old red blood cells; also involved in recognition of foreign antigens andactivation of lymphocytes.
Macula lutea (MAK-yoo-lah LOO-tee-ah)
A spot in the center of the retina; contains the fovea.
Magnetic resonance imaging (MRI) (mag-NET-ik REZah-nanse IM-ah-jing)
A diagnostic imaging technique that uses a magnetic field and a computer to integrate the images of internal organs.
Male sexual dysfunction
It is inability to attain and maintain an erect penis with sufficient rigidity for vaginal penetration and ability to ejaculate. Organic causes include neurogenic, vasculogenic, endocrinological as well as many systemic diseases and medications.
Malignant (muh-LIG-nunt)
Tending to spread and become worse; used especially with reference to cancer.
Malleus (MAL-ee-us)
The first of the three auditory bones in the middle ear; transmits vibrations from the eardrum to the incus.
Mallory-Weiss Syndrome (Mucosal Laceration of Gastroesophageal Junction)
Mallory-Weiss syndrome is characterized by a nonpene­trating mucosal tear at the gastroesophageal junction that is hypothesized to arise from events that suddenly raise transabdominal pressure, such as lifting, retching, or vom­iting. Alcoholism is a strong predisposing factor. Mallory- Weiss tears are responsible for approximately 5% of cases of upper gastrointestinal bleeding
Malocclusion is any variation in the arrangement of teeth leading to abnormal occlusions to the extent that may be functionally harmful or aesthetically objectionable.
Maltase (MAWL-tays)
A digestive enzyme that breaks down maltose to glucose; secreted by the small intestine.
Maltose (MAWL-tohs)
A disaccharide made of two glucose molecules.
Mammary glands (MAM-uh-ree)
The glands of the female breasts that secrete milk; secretion and release of milk are under hormonal control.
Mammography (mah-MOG-rah-fee)
A diagnostic procedure that uses radiography to detect breast cancer.
Mandible (MAN-di-buhl)
The lower jaw bone.
Manifestation index
Number of manifest cases of a disease in relation to number of infections
Manubrium (muh-NOO-bree-um)
The upper part of the stern.
Marrow canal (MA-roh ka-NAL)
The cavity within the diaphysis of a long bone; contains yellow bone marrow.
It is an infection/inflammation of the tissue of one or both of the mammary glands inside the breast. Mastitis usually affects women who are producing milk and breast-feeding.
Mastoditis with Sub-periosteal abscess
It is due to infection of the mastoid air cells in the middle ear, a complication of chronic suppurative otitis media. It presents as a fluctuant painful swelling on the post auricular area. The overlying skin is also inflamed.
Mastoid sinus (MASS-toyd)
An air cavity within the mastoid process of the temporal bone.
Matrix (MAY-triks)
1. The non-living intercellular material that is part of connective tissues. 2. The part of a hair root in which mitosis takes place.
Matter (MAT-ter)
Anything that occupies space; may be solid, liquid, or gas; may be living or non-living.
Maxilla (mak-SILL-ah)
The upper jaw bone.
Measles is an acute, highly communicable infectious disease caused by Measles virus. The mode of transmission is airborne spread through coughing or sneezing, or by direct contact with nasal or throat secretions of infected persons.
Mechanical digestion (muh-KAN-i-kuhl dye-JES-chun)
The physical breakdown of food into smaller pieces, which increases the surface area for the action of digestive enzymes.
Medial (MEE-dee-uhl)
Toward the midline, or in the middle.
Mediastinum (ME-dee-ah-STYE-num)
The area or space between the lungs; contains the heart and great vessels.
Medulla (muh-DEW-lah) (muh-DULL-ah)
1. The part of the brain superior to the spinal cord; regulates vital functions such as heart rate, respiration, and blood pressure. 2. The inner part of an organ, such as the renal medulla or the adrenal medulla.
Megakaryocyte (MEH-ga-KA-ree-oh-sight)
A cell in the red bone marrow that breaks up into small fragments called platelets, which then circulate in peripheral blood.
Megaloblastic Anemia
This is the condition whereby the bone marrow usually produces large, structurally abnormal, immature red blood cells (megaloblasts) often due to inadequate intake or malabsorption of vitamin B12 or folate.
Meiosis (my-OH-sis)
The process of cell division in which one cell with the diploid number of chromosomes divides twice to form four cells, each with the haploid number of chromosomes; forms gametes.
Meissner’s plexus (MIZE-ners PLEK-sus)
The autonomic nerve plexus in the submucosa of the organs of the alimentary tube; regulates secretions of the glands in the mucosa of these organs (Syn.—submucosal plexus).
Melanin (MEL-uh-nin)
A protein pigment produced by melanocytes. Absorbs ultraviolet light; gives color to the skin, hair, iris, and choroid layer of the eye.
Melanocyte (muh-LAN-o-sight)
A cell in the lower epidermis that synthesizes the pigment melanin.
Melanoma (MEL-ah-NOH-mah)
Malignant pigmented mole or nevus.
Melatonin (mel-ah-TOH-nin)
A hormone produced by the pineal gland; influences sleep cycles.
Membrane (MEM-brayn)
A sheet of tissue; may be made of epithelial tissue or connective tissue.
Membrane toxins.
These toxins disrupt biological membranes, either by attaching to them and assembling to form pores, or in the form of phospholipases that destroy membrane structure enzymatically
Meninges (me-NIN-jeez)
The connective tissue membranes that line the dorsal cavity and cover the brain and spinal cord.
Meningitis (MEN-in-JIGH-tis)
Inflammation of the meninges, most often the result of bacterial infection
Menopause (MEN-ah-paws)
The period during life in which menstrual activity ceases; usually occurs between the ages of 45 and 55 year.
Menstrual cycle (MEN-stroo-uhl SIGH-kuhl)
The periodic series of changes that occur in the female reproductive tract; the average cycle is 28 days.
Menstruation (MEN-stroo-AY-shun)
The periodic discharge of a bloody fluid from the uterus that occurs at regular intervals from puberty to menopause.
Mesentery (MEZ-en-TER-ee)
The visceral peritoneum (serous) that covers the abdominal organs; a large fold attaches the small intestine to the posterior abdominal wall
Mesoderm (MEZ-oh-derm)
The middle primary germ layer of cells of an embryo; gives rise to muscles, bones, and connective tissues.
Metabolic acidosis (MET-uh-BAH-lik ass-i-DOH-sis)
A condition in which the blood pH is lower than normal, caused by any disorder that increases the number of acidic molecules in the body or increases the loss of alkaline molecules.
Metabolic alkalosis (MET-uh-BAH-lik al-kah-LOH-sis)
A condition in which the blood pH is higher than normal, caused by any disorder that decreases the number of acidic molecules in the body or increases the number of alkaline molecules
Metabolism (muh-TAB-uh-lizm)
All of the physical changes and chemical reactions that take place within the body; includes anabolism and catabolism
Metacarpals (MET-uh-KAR-puhls)
The five long bones in the palm of the hand
Metaphase (MET-ah-fayz)
The second stage of mitosis, in which the pairs of chromatids line up on the equator of the cell
Metastasis (muh-TASS-tuh-sis)
The spread of disease from one part of the body to another
Metatarsals (MET-uh-TAR-suhls)
The five long bones in the arch of the foot.
Microglia (my-kroh-GLEE-ah)
A type of neuroglia capable of movement and phagocytosis of pathogens
Micrometer (MY-kroh-mee-ter)
A unit of linear measure equal to one thousandth of a millimeter (0.001 mm)
Micron (MY-kron)
Old name for a micrometer
Microvilli (MY-kro-VILL-eye)
Folds of the cell membrane on the free surface of an epithelial cell; increase the surface area for absorption
Micturition (MIK-tyoo-RISH-un)
Urination; the voiding or elimination of urine from the urinary bladder
Midbrain (MID-brayn)
The part of the brain between the pons and hypothalamus; regulates visual, auditory, and righting reflexes
Mild pre-eclampsia
This is diagnosed when 90mmHg≤ diastolic BP <110 mmHg; Proteinuria 1+ or 2+
Mineral (MIN-er-al)
An inorganic element or compound; many are needed by the body for normal metabolism and growth
Mineralocorticoids (MIN-er-al-oh-KOR-ti-koidz)
The hormones secreted by the adrenal cortex that affect fluid–electrolyte balance; aldosterone is the major hormone in this group
Minimum infective dose
Smallest number of pathogens sufficient to cause an infection
Minute respiratory volume (MIN-uht RES-pi-rah-TORee VAHL-yoom)
The volume of air inhaled and exhaled in 1 minute; calculated by multiplying tidal volume by number of respirations per minute
Mitochondria (MY-toh-KAHN-dree-ah)
The cell organelles in which aerobic cell respiration takes place and energy (ATP) is produced; found in the cytoplasm of a cell
Mitosis (my-TOH-sis)
The process of cell division in which one cell with the diploid number of chromosomes divides once to form two identical cells, each with the diploid number of chromosomes
Mitral valve (MY-truhl VALV)
The left AV valve (bicuspid valve), which prevents backflow of blood from the left ventricle to the left atrium when the ventricle contracts
Mixed nerve (MIKSD NERV)
A nerve that contains both sensory and motor neurons
Mode of infection
Method or pathway used by pathogen to invade host
Molar pregnancy/Abortion
It happens when tissues that normally becomes a fetus instead became an abnormal growth in the uterus. Once diagnosed it should be treated right away.
Molecule (MAHL-e-kuhl)
A chemical combination of two or more atoms
Monocyte (MAH-no-sight)
A type of white blood cell (agranular); differentiates into a macrophage, which is capable of phagocytosis of pathogens and dead or damaged cells
Monosaccharide (MAH-noh-SAK-ah-ride)
A carbohydrate molecule that is a single sugar; includes the hexose and pentose sugars
Number of cases of a disease within a given population (e.g., per 1000, 10 000 or 100 000 inhabitants)
Number of deaths due to a disease within a given population
Morula (MOR-yoo-lah)
An early stage of embryonic development, a solid sphere of cells
Motility (moh-TILL-e-tee)
The ability to move
Motion sickness (MOH-shun)
Queasiness that accompanies repetitive or unexpected motion
Motor area (MOH-ter)
Part of the cerebral cortex of the frontal lobe; generates the impulses necessary for voluntary movement
Motor neuron (MOH-ter NYOOR-on)
A nerve cell that carries impulses from the central nervous system to an effector (Syn.—efferent neuron)
Mucosa (mew-KOH-suh)
A mucous membrane, the epithelial lining of a body cavity that opens to the environment
Mucous membrane (MEW-kuss MEM-brayn)
The epithelial tissue lining of a body tract that opens to the environment
Mucus (MEW-kuss)
The thick fluid secreted by mucous membranes or mucous glands
Multicellular (MULL-tee-SELL-yoo-lar)
Consisting of more than one cell; made of many cells
Multiple sclerosis (MULL-ti-puhl skle-ROH-sis)
A progressive nervous system disorder, an autoimmune disease, characterized by the degeneration of the myelin sheaths of CNS neurons
Muscle fatigue (MUSS-uhl fah-TEEG)
The state in which muscle fibers cannot contract efficiently, due to a lack of oxygen and the accumulation of lactic acid
Muscle fiber (MUSS-uhl FYE-ber)
A muscle cell
Muscle sense (MUSS-uhl SENSE)
The conscious or unconscious awareness of where the muscles are, and their degree of contraction, without having to look at them
Muscle tissue (MUSS-uhl TISH-yoo)
The tissue specialized for contraction and movement of parts of the body
Muscle tone (MUSS-uhl TONE)
The state of slight contraction present in healthy muscles
Muscular dystrophy (MUSS-kyoo-ler DIS-truh-fee)
A genetic disease characterized by the replacement of muscle tissue by fibrous connective tissue or adipose tissue, with progressive loss of muscle functioning; the most common form is Duchenne’s muscular dystrophy
Muscular system (MUSS-kew-ler)
The organ system that consists of the skeletal muscles and tendons; its functions are to move the skeleton and produce body heat
Mutation (mew-TAY-shun)
A change in DNA; a genetic change that may be passed to offspring
Myalgia (my-AL-jee-ah)
Pain or tenderness in a muscle
Myasthenia gravis (MY-ass-THEE-nee-yuh GRAH-viss)
An autoimmune disease characterized by extreme muscle weakness and fatigue following minimal exertion
Mycetoma (Madura foot)
Is a chronic infection of skin and subcutaneous tissue. It can be caused by fungi or bacteria. Once test have established the etiology, the term Actinomycetoma is used for bacterial form, while Eumycetoma is used for the fungal form. Clinical presentation depends on the affected site and the disease can last for months or years.
Mycoplasmas are bacteria without rigid cell walls. They are found in a wide variety of forms, the most common being the coccoid cell (0.3–0.8 μm). Threadlike forms also occur in various lengths.
Mycosis (my-KOH-sis)
(Pl.—mycoses) An infection caused by a pathogenic fungus
Myelin (MY-uh-lin)
A phospholipid produced by Schwann cells and oligodendrocytes that forms the myelin sheath of axons and dendrites
Myelin sheath (MY-uh-lin SHEETH)
The white, segmented, phospholipid sheath of most axons and dendrites; provides electrical insulation and increases the speed of impulse transmission
Myocardial infarction (MI) (MY-oh-KAR-dee-yuhl in-FARK-shun)
Death of part of the heart muscle due to lack of oxygen; often the result of an obstruction in a coronary artery (Syn.—heart attack)
Myocardium (MY-oh-KAR-dee-um)
The cardiac muscle tissue that forms the walls of the chambers of the heart
Myofibril (MY-oh-FYE-bril)
A linear arrangement of sarcomeres within a muscle fiber
Myoglobin (MY-oh-GLOW-bin)
The protein in muscle fibers that contains iron and stores oxygen in muscle fibers
Myometrium (MY-oh-MEE-tree-uhm)
The smooth muscle layer of the uterus; contracts for labor and delivery of an infant
Myopathy (my-AH-puh-thee)
A disease or abnormal condition of skeletal muscles
Myopia (my-OH-pee-ah)
Nearsightedness; an error of refraction in which only near objects are seen clearly
Myopia (short sightedness)
This is a condition whereby patient has difficulty seeing far objects.

  • It is common in young age between 5-25 years

  • The condition persists throughout life

  • If not treated early, it may progress rapidly and lead to retinal complications

Myosin (MY-oh-sin)
A contractile protein in the sarcomeres of muscle fibers; pulls actin filaments
Myxedema (MIK-suh-DEE-mah)
Hyposecretion of thyroxine in an adult; decreased metabolic rate results in physical and mental lethargy
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