| prefloration | <botany> Aestivation. Origin: Pref. Pre- + L. Flos, floris, flower. Source: Websters Dictionary (01 Mar 1998) |
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| prefoliation | <botany> Vernation. Origin: Pref. Pre- + L. Folium leaf. Source: Websters Dictionary (01 Mar 1998) |
| preformation | <biology> An old theory of the preexistence of germs. Cf. Embo<icir/tement. Source: Websters Dictionary (01 Mar 1998) |
| preformation theory | Archaic theory that the embryo was fully formed in miniature within a gamete at the time of conception. See: homunculus. Synonym: emboitement, incasement theory. (05 Mar 2000) |
| prefrontal | <anatomy> Situated in front of the frontal bone, or the frontal region of the skull; ectethmoid, as a certain bone in the nasal capsule of many animals, and certain scales of reptiles and fishes. A prefrontal bone or scale. Source: Websters Dictionary (01 Mar 1998) |
| prefrontal area | Cortex of the frontal lobe of the cerebral hemisphere, originally, the entire cortical expanse anterior to the central sulcus, including the agranular motor and premotor cortex (Brodmann's areas 4 and 6), the dysgranular cortex (area 8), and the granular frontal (prefrontal) cortex anterior to the latter, now more often refers to the granular frontal (prefrontal) cortex. Synonym: frontal area. (05 Mar 2000) |
| prefrontal cortex | The rostral part of the frontal lobe, bounded by the inferior precentral fissure in humans, which receives projection fibres from the mediodorsal nucleus of the thalamus. The prefrontal cortex receives afferent fibres from numerous structures of the diencephalon, mesencephalon, and limbic system as well as cortical afferents of visual, auditory, and somatic origin. (12 Dec 1998) |
| prefrontal leukotomy | Division of one or more nerve tracts in the prefrontal area of the brain for surgical treatment of pain and emotional disorder. Synonym: prefrontal leukotomy. (05 Mar 2000) |
| prefrontal lobotomy | Division of one or more nerve tracts in the prefrontal area of the brain for surgical treatment of pain and emotional disorder. Synonym: prefrontal leukotomy. (05 Mar 2000) |
| prefrontal veins | The superficial veins draining the prefrontal cerebral cortex and emptying into the superior sagittal sinus. Synonym: prefrontal veins. (05 Mar 2000) |
| preganglionic | Situated proximal to or preceding a ganglion; referring specifically to the preganglionic motor neurons of the autonomic nervous system (located in the spinal cord and brainstem) and the preganglionic, myelinated nerve fibres by which they are connected to the autonomic ganglia. (05 Mar 2000) |
| preganglionic fibres | A fibre whose cell body is located in an autonomic nucleus in the spinal cord or brain stem and whose axon terminates in an autonomic (motor) ganglion; found in nerves conveying sympathetic or parasympathetic fibres. (05 Mar 2000) |
| preganglionic motor neuron | See: motor neuron. (05 Mar 2000) |
| pregenital organization | In psychoanalysis, the organization or arrangement of the libido in the stages prior to that of genital primacy. (05 Mar 2000) |
| pregenital phase | In psychoanalysis, the collective psychosexual development phase's preceding the genital phase. (05 Mar 2000) |