- - anterior divisions of (trunks of) brachial plexus [TA] portion of the superior, middle, and inferior trunks of the brachial plexus that are destined to serve the anterior or flexor compartments of the upper limb. SYN: divisiones anteriores plexus brachialis [TA].- autonomic d. of nervous system [TA] that part of the nervous system which represents the motor innervation of smooth muscle, cardiac muscle, and gland cells. It consists of two physiologically and anatomically distinct, mutually antagonistic components: the sympathetic and parasympathetic parts. In both of these parts the pathway of innervation consists of a synaptic sequence of two motor neurons, one of which lies in the spinal cord or brainstem as the presynaptic (preganglionic) neuron, the thin but myelinated axon of which (presynaptic (preganglionic) or B fiber) emerges with an outgoing spinal or cranial nerve and synapses with one or more of the postsynaptic (postganglionic or, more strictly, ganglionic) neurons composing the autonomic ganglia; the unmyelinated postsynaptic fibers in turn innervate the smooth muscle, cardiac muscle, or gland cells. The presynaptic neurons of the sympathetic part lie in the intermediolateral cell column of the thoracic and upper two lumbar segments of the spinal gray matter; those of the parasympathetic part compose the visceral motor (visceral efferent) nuclei of the brainstem as well as the lateral column of the second to fourth sacral segments of the spinal cord. The ganglia of the sympathetic part are the paravertebral ganglia of the sympathetic trunk and the lumbar and sacral prevertebral or collateral ganglia; those of the parasympathetic part lie either near the organ to be innervated or as intramural ganglia within the organ itself except in the head, where there are four discrete parasympathetic ganglia (ciliary, otic, pterygopalatine, and submandibular). Impulse transmission from presynaptic to postsynaptic neuron is mediated by acetylcholine in both the sympathetic and parasympathetic parts; transmission from the postsynaptic fiber to the visceral effector tissues is classically said to be by acetylcholine in the parasympathetic part and by noradrenalin in the sympathetic part; recent evidence suggests the existence of further noncholinergic, nonadrenergic classes of postsynaptic fibers. SYN: divisio autonomica systematis nervosi peripherici [TA], pars autonomica systematis nervosi peripherici [TA], autonomic part of peripheral nervous system, autonomic nervous system, involuntary nervous system, systema nervosum autonomicum, vegetative nervous system, visceral motor system, visceral nervous system.- cleavage d. the rapid mitotic d. of the zygote with decrease in size of individual cells or blastomeres and the formation of a morula. SEE ALSO: cleavage (1).- craniosacral d. of autonomic nervous system SYN: parasympathetic part of autonomic d. of peripheral nervous system.- left lateral d. of liver [TA] in the surgical schema for subdividing the liver, the portion that lies to the left of the approximately vertical plane of the left hepatic vein and includes the left posterior and anterior lateral segments (hepatic segments II and III); it corresponds with the left anatomic lobe of the liver, and so is demarcated externally by the falciform ligament on the diaphragmatic surface and by the fissures for the ligamentum venosum and ligamentum teres on the viscera surface. SYN: divisio lateralis sinistra hepatis [TA].- left medial d. of liver [TA] in the surgical schema for subdividing the liver, the portion that lies between the approximately vertical planes of the left and middle hepatic veins and includes the left medial segment (hepatic segment IV); on the diaphragmatic surface, it is approximately the left third of the anatomic right lobe of the liver; on the visceral surface, its inferior portion corresponds to the quadrate lobe. SYN: divisio medialis sinistra hepatis [TA].- multiplicative d. reproduction by simultaneous d. of a mother cell into a number of daughter cells. If the process occurs without fertilization of the mother cell, or encystment, the daughter cells are called merozoites; if they develop within a cyst, and usually after fertilization, they are called sporozoites.- posterior divisions of (trunks of) brachial plexus [TA] portion of the superior, middle, and inferior trunks of the brachial plexus that are destined to serve the posterior or extensor compartments of the upper limb. SYN: divisiones posteriores plexus brachialis [TA].- reduction d. reduction of chromosomes.- right lateral d. of liver [TA] in the surgical schema for subdividing the liver, the portion that lies to the right of the approximately vertical plane of the right hepatic vein and includes the right anterior and posterior lateral segments (hepatic segments VI and VII); it is approximately the right third of the right anatomic lobe of the liver. SYN: divisio lateralis dextra hepatis [TA].- right medial d. of liver [TA] in the surgical schema for subdividing the liver, the portion that lies between the approximately vertical planes of the right and middle hepatic veins and includes the right anterior and posterior medial segments (hepatic segments V and VIII); it is approximately the middle third of the anatomic right lobe of the liver. SYN: divisio medialis dextra hepatis [TA].
* * *di·vi·sion də-'vizh-ən n2) a group of organisms forming part of a larger group specif a primary category of the plant kingdomdi·vi·sion·al -'vizh-nəl, -'vizh-ən-əl adj
* * *n.1. the separation of an organ or tissue into parts by surgery.
* * *di·vi·sion (dĭ-vizhґən) [L. dividere to separate] 1. the act or process of separation or sectioning into two or more parts. 2. a section or part of a larger structure. 3. in the taxonomy of plants, a primary grouping composed of classes; the equivalent of phylum in the animal kingdom. 4. in the taxonomy of fungi, former term for phylum.
Medical dictionary. 2011.