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Macewen’s triangle

1. The area in the temporal bone in between the posterior wall of the external acoustic meatus and the posterior root of the zygomatic process through which an instrument may be pushed into the mastoid antrum. ( 2. Macewen’s triangle is the most important surgical landmark for the mastoid antrum or the largest mastoid air cell. The boundaries include: Superiorly: Suprameatal crest Anterior-inferiorly: Posterior margin of external auditory canal Posteriorly: A tangential line from the posterior canal wall cutting the suprameatal crest ( Syn: suprameatal triangle, suprameatal pit, mastoid fossa, foveola...

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/məˈlignənt/ Adjective 1. Harmful, malevolent, injurious. ( 2. Dangerous to health; characterized by progressive and uncontrolled growth (especially of a tumor). ( (Oncology) 1. Harmfully cancerous; as a malignant tumor. ( Word origin: From Middle French malignant and directly from Late Latin malignantem (nominative malignans) “acting from malice,” present participle of malignare “injure...

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Malpighian corpuscle

Noun, pl. Malpighian corpuscles Refers to either of two anatomical structures: Renal corpuscles the initial filtering component of nephrons in the kidneys. ( the capsule that contains Bowman’s capsule and a glomerulus at the expanded end of a nephron.  ( Splenic lymphoid nodules, or White nodules follicles in the white pulp of the spleen, containing many lymphocytes. ( a mass of lymphoid tissue surrounding an arteriole of the spleen. ( any of the small masses of adenoid tissue formed around the branches of the splenic artery in the spleen. ( Word origin: These structures are named after Marcello Malpighi (1628-1694), an Italian physician and biologist regarded as the father of microscopical anatomy and histology....

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/ˈmaməl/ Noun, pl. mammals 1. An animal of the class Mammalia, characterized by being warm-blooded, having hair and feeding milk to its young. ( 2. Any warm-blooded vertebrate having the skin more or less covered with hair; young are born alive except for the small subclass of monotremes and nourished with milk. ( 3. (Paleontology) A vertebrate with three bones in the inner ear and one in the jaw. ( 4. Any of the endothermic vertebrates belonging to class Mammalia, which are identifiable by the following characteristics: a neocortex, three middle ear bones, a lower jaw made of a single bone, a hairy body covering, a thoracic diaphragm, a four-chambered heart, and females that are mostly viviparous. ( 5. Warm-blooded vertebrate animals belonging to the class mammalia, including all that possess hair and suckle their young. It includes three major groups: placentals and marsupials, which are vivparous, and monotremes, which are oviparous. ( 6. Warm-blooded vertebrate animals belonging to the class Mammalia, including all that possess hair and suckle their young. ( Word origin: Anglicized form of Modern Latin Mammalia (1773), coined 1758 by Linnaeus for the class of mammals, from neuter plural of Late mammalis “of the breast,” from Latin mamma...

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Noun 1. Class Mammalia, a taxonomic class within the subphylum Vertebrata — the mammals. ( 2. The highest class of the subphylum Vertebrata comprising humans and all other animals that nourish their young with milk secreted by mammary glands, that have the skin usually more or less covered with hair, a mandible articulating directly with the squamosal, a chain of small ear bones, a brain with four optic lobes, a muscular diaphragm separating the heart and lungs from the abdominal cavity, only a left arch of the aorta, warm blood containing red blood cells without nuclei except in the fetus, and embryos developing both an amnion and an allantois, and that except in the monotremes reproduce viviparously. ( 3. Clade of warm-blooded amniotes. Among the features that distinguish them from the other amniotes, the reptiles and the birds, are hair, three middle ear bones, mammary glands in females, and a neocortex (a region of the brain). ( See mammal. Word origin: From Modern Latin (Linnaeus), from neuter plural of Late Latin mammalis, from...

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