| internal axis of eye | <anatomy> That part of the optic axis from the midpoint of the posterior surface of the cornea to the anterior surface of the retina opposite the posterior pole. Synonym: axis bulbi internus. (05 Mar 2000) |
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| internal base of skull | <anatomy> The interior aspect of the skull base on which the brain rests; the floor of the cranial cavity. See: base of skull. Synonym: basis cranii interna. (05 Mar 2000) |
| internal bias | Applied to the motile behaviour of crawling cells that, in the short term, show persistence and do not behave as true random walkers. Any intrinsic regulation of the random motile behaviour of the cell could be considered as internal bias. (18 Nov 1997) |
| internal canthus | The angle formed by the union of the upper and lower eyelids medially. Synonym: angulus oculi medialis, angulus oculi nasalis, internal canthus, medial canthus. (05 Mar 2000) |
| internal capsule | <anatomy, neurology> A massive layer (8 to 10 mm thick) of white matter separating the caudate nucleus and thalamus (medial) from the more laterally situated lentiform nucleus (globus pallidus and putamen). It consists of 1) fibres ascending from the thalamus to the cerebral cortex that compose, among others, the visual, auditory, and somatic sensory radiations, and 2) fibres descending from the cerebral cortex to the thalamus, subthalamic region, midbrain, hindbrain, and spinal cord. The internal capsule is the major route by which the cerebral cortex is connected with the brainstem and spinal cord. Laterally and superiorly it is continuous with the corona radiata which forms a major part of the cerebral hemisphere's white matter; caudally and medially it continues, much reduced in size, as the crus cerebri which contains, among others, the pyramidal tract. On horizontal section it appears in the form of a V opening out laterally; the V's obtuse angle is called genu (knee). Its anterior and posterior limbs, respectively, the crus anterior and crus posterior. Synonym: capsula interna. (05 Mar 2000) |
| internal capsule syndrome | <syndrome> Hemianopsia with contralateral hemianesthesia of the face. (05 Mar 2000) |
| internal carotid artery | <anatomy, artery> Arises from the common carotid opposite upper border of thyroid cartilage (C-4 vertebral level) and terminates in the middle cranial fossa by dividing into the anterior and middle cerebral arteries; for descriptive purposes it is divided into four parts: cervical, petrous, cavernous, and cerebral. Synonym: arteria carotis interna. (05 Mar 2000) |
| internal carotid (nervous) plexus | An autonomic plexus surrounding the internal carotid artery in the carotid canal and cavernous sinus, and sending branches to the tympanic plexus, sphenopalatine ganglion, abducens and oculomotor nerves, the cerebral vessels, and the ciliary ganglion. Synonym: internal carotid venous plexus. (05 Mar 2000) |
| internal carotid venous plexus | A venous network around the internal carotid artery in the carotid canal of the temporal bone, connecting with the cavernous sinus and internal jugular vein. Synonym: plexus venosus caroticus internus, internal carotid (nervous) plexus, plexus caroticus internus. (05 Mar 2000) |
| internal cephalic version | Version performed by means of one hand within the vagina. See: cephalic version. (05 Mar 2000) |
| internal cerebral veins | Paired veins passing caudally near the midline in the tela choroidea of the third ventricle, formed by the union of the choroid vein, thalamostriate (terminal) vein, and vein of septum pellucidum, and uniting caudally so as to form the great cerebral vein. Synonym: venae cerebri internae, veins of Galen. (05 Mar 2000) |
| internal collateral ligament of the wrist | A ligament that passes from the styloid process of the ulna to the pisiform and triquetrum. Synonym: ligamentum collaterale carpi ulnare, internal collateral ligament of the wrist, medial ligament of wrist. (05 Mar 2000) |
| internal conjugate | Distance from the promontory of the sacrum to the upper posterior edge of the pubic symphysis. Synonym: anteroposterior diameter of the pelvic inlet, conjugata vera, conjugate axis, conjugate diameter of pelvic inlet, diameter mediana, internal conjugate, true conjugate. (05 Mar 2000) |
| internal conversion electron | An electron, similar to an Auger electron, released from one of the electron orbits of the atom upon activation by a gamma-ray from that atom's nucleus; the electron has kinetic energy equal to the net energy transition of the disintegration. (05 Mar 2000) |
| internal decompression | Removal of intracranial tissue, usually tumour or brain tissue. To relieve pressure. (05 Mar 2000) |