- 1. A pouch or bursa. SYN: saccus [TA]. SEE ALSO: sacculus. 2. An encysted abscess at the root of a tooth. 3. The capsule of a tumor, or envelope of a cyst. [L. saccus, a bag]- air s. SYN: alveolar s..- allantoic s. the dilated distal portion of the allantois; it forms part of the placenta in many mammals.- alveolar s. 1. terminal dilation of the alveolar ducts that give rise to alveoli in the lung; a small air chamber in the pulmonary tissue from which the pulmonary alveoli project like bays and into which an alveolar duct opens; SYN: sacculus alveolaris [TA]. 2. in birds, air-containing extensions of bronchi that connect with bone cavities. SYN: air s..- aortic s. in mammalian embryos, the endothelially lined dilation just distal to the truncus arteriosus; it is the primordial vascular channel from which the aortic arch/arteries arise and is homologous to the ventral aorta of gill-bearing vertebrates.- conjunctival s. [TA] the space bound by the conjunctival membrane between the palpebral and bulbar conjunctiva, into which the lacrimal fluid is secreted; it is a closed space when eye is closed; when eye is open, the s. is open anteriorly via the palpebral fissure (between the eyelids). SYN: saccus conjunctivalis [TA].- dental s. the outer investment of mesenchymal tissue surrounding a developing tooth; involved in formation of the root and periodental ligament. SEE ALSO: dental follicle.- endolymphatic s. [TA] the dilated blind extremity of the endolymphatic duct, which lies external to the dura on the posterior aspect of the petrous part of the temporal bone. SYN: saccus endolymphaticus [TA], Böttcher space, Cotunnius space, sacculus endolymphaticus.- gestational s. cystic structure of early pregnancy that represents the amnionic s., fluid, and placenta.- lacrimal s. [TA] the dilated upper portion of the nasolacrimal duct into which the two lacrimal canaliculi empty. SYN: saccus lacrimalis [TA], dacryocyst, sacculus lacrimalis, tear s..- pudendal s. a pear-shaped encapsulated collection of connective tissue and fat in each labium majus. SYN: Broca pouch.- yolk s. 1. in vertebrates with telolecithal eggs; the highly vascular layer of splanchnopleure surrounding the yolk of an embryo; 2. in humans and other mammals, the s. of extraembryonic membrane that is located ventral to the embryonic disk and, after formation of the gut tube, is connected to the midgut; by the second month of development, this connection has become the narrow yolk stalk; the yolk s. is the first hematopoietic organ of the embryo, and its vitelline circulation plays an important role in the early embryonic circulation; the s. is also the site of origin of the primordial germ cells. SYN: umbilical vesicle, vesicula umbilicalis, vitelline s..* * *saccharin; sacrum; screening and acute care; seasonal acute conjunctivitis; Self-Assessment of Communication [scale]; serum aminoglycoside concentration; short-arm cast; sideline assessment of concussion; small accessory chromosome; social activity [scale]; splinting for acute closure; stable access cannula; stretch- activated channel [heart contraction]; subarea advisory council; substance abuse counselor; symptomatic anomaly complex
* * *sac 'sak n a soft-walled anatomical cavity usu. having a narrow opening or none at all and often containing a special fluid <a synovial \sac> see AIR SAC, amniotic sac, DENTAL SAC, LACRIMAL SAC
* * *n.a pouch or baglike structure. Sacs can enclose natural cavities in the body, e.g. in the lungs (see alveolus) or in the lacrimal apparatus of the eye, or they can be pathological, as in a hernia.
* * *(sak) [L. saccus; Gr. sakkos] a pouch or bag.
Medical dictionary. 2011.