Medical Definitions - M
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Magnetic resonance imaging - A special radiology technique designed to image internal structures of the body using magnetism, radio waves, and a computer to produce the images of body structures.
Malrotation - failure of normal rotation of an organ, as of the gut, during embryonic development.
Meckel's diverticulum - a small bulge in the small intestine present at birth.
Marfan syndrome - an autosomal dominant genetic disorder of the connective tissue characterized by disproportionately long limbs, long thin fingers, a typically tall stature, and a predisposition to cardiovascular abnormalities, specifically those affecting the heart valves and aorta. The disorder may also affect numerous other structures and organs - including the lungs, eyes, dural sac surrounding the spinal cord, and hard palate.
Mediastinal shift - a shifting or moving of the tissues and organs that comprise the mediastinum to one side of the chest cavity.
Mediastinum - the region in mammals between the pleural sacs, containing the heart and all of the thoracic viscera (great vessels, trachea and esophagus) except the lungs.
Medulla - the innermost part.
Meninges - the three membranes covering the brain and spinal cord: dura mater, arachnoid, and pia mater.
Metabolic balance - an equilibrium between the intake of nutrients and their eventual loss through absorption or excretion. In a positive balance the intake of a nutrient exceeds its loss; in a negative balance a nutrient is used or excreted faster than it is consumed in the diet.
Microcephaly - a neurological disorder in which the circumference of the head is significantly smaller than average for the person's age and sex.
Microphthalmia - abnormal smallness of the eye.
Mitral valve - also known as bicuspid valve or left atrioventricular valve; a valve of the heart, composed of two triangular flaps, that is located between the left atrium and left ventricle and regulates blood flow between these chambers.
Mitral valve regurgitation - also known as chronic mitral valve regurgitation or mitral valve insufficiency; a long-term disorder in which the heart's mitral valve does not close properly, causing blood to flow backward (leak) into the upper heart chamber when the left lower heart chamber contracts. The condition is progressive, which means it gradually gets worse.
Misoprostol - see also Cytotec; a drug that some medical professionals still use to induce labor although it is contraindicated for use in pregnancy.
Mongolism - see Down Syndrome or Trisomy 21.
Monosomy x - see Turner syndrome.
Morgagni hernia - diaphragmatic hernia occurring near the front of the body, near the breastbone.
Mosaic - denotes the presence of two populations of cells with different genotypes in one individual, who has developed from a single fertilized egg.
Myelin - the lipid substance forming a sheath around the axons of certain nerve fibers.
Myocardial ischaemia - also known as Ischaemic (or ischemic) heart disease; a disease characterized by reduced blood supply to the heart. It is the most common cause of death in most western countries.