- 1. A term applied to a number of anatomic structures having a more or less pyramidal shape. SYN: pyramis [TA]. 2. A term denoting the petrous portion of the temporal bone. [G. pyramis (p.-), a p.]- p. of medulla oblongata an elongated, white prominence on the ventral surface of the medulla oblongata on either side along the anterior median fissure, corresponding to the position of fibers forming the corticospinal tracts. SYN: pyramis medullae oblongatae [TA], anterior column of medulla oblongata, anterior p..- olfactory p. a small area of gray matter situated between the roots of the olfactory tracts; it is continuous caudally with the anterior perforated substance.- population p. graphic representation of the age and sex composition of a population, constructed by computing the percentage distribution of the population in each age and sex class.- renal pyramids [TA] pyramidal masses seen on longitudinal section of the kidney; collectively, they constitute the renal medullae and contain part of the secreting tubules and the collecting tubules. SYN: malpighian p., medullary p., pyramides renales, pyramis renalis.- p. of vermis [TA] a subdivision of the inferior vermis of the cerebellum between the tuber and the uvula; vermis lobule VIII. SYN: cerebellar p., pyramis [TA] of cerebellum.- p. of vestibule [TA] the upper triangular extremity of the crista vestibuli. SYN: pyramis vestibuli [TA].
* * *pyr·a·mid 'pir-ə-.mid n1) a polyhedron having for its base a polygon and for faces triangles with a common vertex2) an anatomical structure resembling a pyramid: asa) RENAL PYRAMIDb) either of two large bundles of motor fibers from the cerebral cortex that reach the medulla oblongata and are continuous with the corticospinal tracts of the spinal cordc) a conical projection making up the central part of the inferior vermis of the cerebellum
* * *n.1. one of the conical masses that make up the medulla of the kidney, extending inwards from a base inside the cortex towards the pelvis of the kidney.2. one of the elongated bulging areas on the anterior surface of the medulla oblongata in the brain, extending downwards to the spinal cord.3. one of the divisions of the vermis of the cerebellum in the middle lobe.4. a protrusion of the medial wall of the vestibule of the middle ear.
* * *pyr·a·mid (pirґə-mid) [Gr. pyramis] a pointed or cone-shaped structure or part; called also pyramis [TA]. The term is often used alone to indicate the pyramid of the medulla oblongata.
Medical dictionary. 2011.