Category: M

The presence of dark colouring in the urine. A condition in which the urine turns black after being allowed to stand, e.g. in cases of malignant melanoma. The presence of dark pigment in the urine. This may be caused by the presence of melanin or its precursors in some cases of melanoma; it may alternatively…

A large amount of melanin in the skin. Discoloration of patches of the skin. Abnormal darkening of the skin caused by increased melanin deposits. Any of several malignant neoplasms, primarily of the skin, consisting of melanocytes. Most melanomas develop from a pigmented nevus (mole); any change in color or shape of such a mark suggests…

The unexpected depositing of dark pigment. The staining of all body tissue with melanin in a form of carcinoma. An unusually pronounced darkening of body tissues caused by excessive production of the pigment melanin. For example, melanism may affect the hair, the skin (after sunburn, during pregnancy, or in Addison’s disease), or the eyes. The…

Black faeces where the colour is caused by bleeding in the intestine. Blood in the faeces in which dark, tarry masses are passed from the bowel. It is due to bleeding from the stomach or from the higher part of the bowel, the blood undergoing chemical changes under the action of the secretions, and being…

A network of nerve fibres in the wall of the alimentary canal [Described 1853. After Georg Meissner (1829-1905), German anatomist and physiologist.] Bundle of autonomic nerves located in the submucosa of the small intestine. A fine network of parasympathetic nerve fibers in the wall of the alimentary canal, supplying the muscles and mucous membrane. An…

A receptor cell in the skin which is thought to be sensitive to touch. A sensory end-organ in which the bare tips of 1-4 sensory axons spiral inside a sphere of ordered epithelial cells. The corpuscle is covered with a capsule that is continuous with the sheaths of the innervating axons. Meissner’s corpuscles are found…

A condition in which liquid collects in the chest and abdominal cavities. It is associated with pelvic tumours. A rare, benign tumor of the ovary that occurs in combination with excess abdominal fluid and pleural effusion, or excess fluid in the pleural cavity. The occurrence of the solid tumor and its related symptom of a…

A condition in which the meibomian glands become swollen. Inflammation of an oil-secreting gland in the eyelid. The meibomian gland is located between the eyelid’s inner lining and the curved plate of connective tissue that forms its basic structure. Inflammation of the meibomian glands, which are oil-producing glands located in the eyelids, arises due to overly…

The swelling of a sebaceous gland in the eyelid. A meibomian cyst results from the blockage of a meibomian gland. These glands, similar to skin’s sebaceous glands, are located on the inner side of the eyelids and have openings at the eyelid edges. When inflamed and enlarged, they resemble styes. However, while a stye appears…

A condition in which a part of the ureter becomes very wide, above the site of a blockage. Gross dilation of the ureter. This occurs above the site of a longstanding obstruction in the ureter, which blocks the free flow of urine from the kidney. A common cause of megaureter is reflux of urine from…