| lactiferous sinus | A circumscribed spindle-shaped dilation of the lactiferous duct just before it enters the nipple. In nursing mothers this dilatation stores a droplet of milk which is expressed by compression as the infant begins to suckle; this is thought to encourage continual suckling while the let-down reflex ensues. Synonym: sinus lactiferi, ampulla lactifera, ampulla of milk duct, lactiferous ampulla. (05 Mar 2000) |
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| laryngeal sinus | The recess in each lateral wall of the larynx between the vestibular and vocal folds and into which the layrngeal sacculus opens. Synonym: ventriculus laryngis, laryngeal sinus, Morgagni's sinus, Morgagni's ventricle, sinus laryngeus. (05 Mar 2000) |
| lateral sinus | A paired dural venous sinus that drains the confluence of sinuses, running along the occipital attachment of the tentorium cerebelli and terminating in the sigmoid sinus. Synonym: sinus transversus, lateral sinus. Transverse pericardial sinus, a passage in the pericardial sac between the origins of the great vessels, i.e., posterior to the intrapericardial portions of the pulmonary trunk and ascending aorta and anterior to the superior vena cava and superior to the atria; it is formed as a result of the flexure of the heart tube, partially approximating the great venous and arterial vessels. Synonym: sinus transversus pericardii, Theile's canal, transverse sinus of pericardium. (05 Mar 2000) |
| frontal sinus | One of the paired, but seldom symmetrical, air spaces located between the inner and outer compact layers of the frontal bone. (12 Dec 1998) |
| frontal sinus aperture | One of a pair of openings in the floor of the frontal sinuses in the nasal part of the frontal bone, through which the frontal sinuses communicate with the ethmoidal infundibulum via the frontonasal duct. Synonym: apertura sinus frontalis. (05 Mar 2000) |
| longitudinal sinus | See: inferior sagittal sinus, superior sagittal sinus. Longitudinal vertebral venous sinus, large, plexiform veins forming portions of the anterior internal vertebral venous plexus lying on the posterior surfaces of the vertebral bodies on either side of the posterior longitudinal ligament. Synonym: sinus vertebrales longitudinales. Luschka's sinus, venous sinus in the petrosquamous suture. (05 Mar 2000) |
| lymphatic sinus | The channels in a lymph node crossed by a reticulum of cells and fibres and bounded by littoral cells; there are subcapsular, trabecular, and medullary sinus's. Synonym: lymph sinus. Maier's sinus, an infundibuliform depression on the internal surface of the lacrimal sac which receives the lacrimal canaliculi. Marginal sinuses of placenta, discontinuous venous lakes at the margin of the placenta. (05 Mar 2000) |
| lymph sinus | The channels in a lymph node crossed by a reticulum of cells and fibres and bounded by littoral cells; there are subcapsular, trabecular, and medullary sinus's. Synonym: lymph sinus. Maier's sinus, an infundibuliform depression on the internal surface of the lacrimal sac which receives the lacrimal canaliculi. Marginal sinuses of placenta, discontinuous venous lakes at the margin of the placenta. (05 Mar 2000) |