The point, line, or surface of union of two parts, mainly bones or cartilages. SYN: juncture. SYN: junctura (2) [TA], junctio.
- adhering junctions intercellular junctions, including zonulae adherentes, hemidesmosomes, and desmosomes, that primarily serve to bind cells together physically.
- amelodental j., amelodentinal j. rarely used terms for dentinoenamel j..
- anorectal j. [TA] transition from rectum to anal canal; corresponds to the perineal flexure, or the level at which the gut perforates the pelvic diaphragm; here the rectal ampulla narrows abruptly into a narrow slip. SYN: junctio anorectalis [TA].
- AV j. imprecisely defined zone surrounding and including the AV node and the adjacent atrial and ventricular myocardium.
- cardioesophageal j. SYN: esophagogastric j..
- cementodentinal j. the surface at which the cementum and dentin of the root of a tooth are joined. SYN: dentinocemental j..
- cementoenamel j. the surface at which the enamel of the crown and the cementum of the root of a tooth are joined. SEE ALSO: cervical line.
- choledochoduodenal j. that part of the duodenal wall traversed by the ductus choledochus, ductus pancreaticus, and ampulla.
- communicating j. SYN: gap j..
- corneoscleral j. SYN: corneal limbus.
- costochondral junctions SYN: costochondral joints, under joint.
- dentinocemental j. SYN: cementodentinal j..
- dentinoenamel j. the surface at which the enamel and the dentin of the crown of a tooth are joined.
- duodenojejunal j. point along the course of the gastrointestinal tract where the duodenum ends and the jejunum begins; occurs approximately at the level of the L2 vertebra, 2–3 cm to the left of the midline; usually takes the form of an acute angle, the duodenojejunal flexure, and is supported by the attachment of the suspensory muscle (ligament) of the duodenum. SEE ALSO: duodenojejunal flexure.
- electrotonic j. SYN: gap j..
- esophagogastric j. terminal end of esophagus and beginning of stomach at the cardiac orifice; site of the physiologic inferior esophageal sphincter. SYN: cardioesophageal j..
- gap j. 1. an intercellular j. formerly considered to be a tight, membrane-to-membrane j. (macula occludens) but now shown to have a 2-nm gap between apposed cell membranes; the gap is not void but contains subunits in the form of polygonal lattices; it occurs in epithelia, between certain nerve cells, and in smooth and cardiac muscle; it is believed to mediate electrotonic coupling which allows ionic currents to pass from one cell to another. SEE ALSO: synapse. 2. areas of increased electrochemical communication between myometrial cells which aid in the propagation of the contractions of labor. SYN: communicating j., electrotonic j., electrotonic synapse, macula communicans, nexus.
- Holliday j. the cross-strand structure formed when two DNA duplexes cross in a recombination event. SYN: Holliday structure.
- ileocecal j. point along the course of the gastrointestinal tract where the small intestine (ileum) ends as it opens into the cecal portion of the large intestine; occurs usually within the iliac fossa, demarcated internally as the ileocecal orifice.
- impermeable j. SYN: zonula occludens.
- intercellular junctions specializations of the cellular margins that contribute to the adhesion or allow for communication between cells; they include the macula adherens (desmosome), zonula adherens, zonula occludens, and nexus (gap j.).
- intermediate j. SYN: zonula adherens.
- j. of lips SYN: commissure of lips.
- manubriosternal j. SYN: sternal angle.
- myoneural j. the synaptic connection of the axon of the motor neuron with a muscle fiber. See motor endplate. SYN: neuromuscular j..
- neuroectodermal j. the margin of the embryonic neural plate separating it from the embryonic surface ectoderm; cells from this region form the neural crest. SYN: neurosomatic j..
- neuromuscular j. SYN: myoneural j..
- neurosomatic j. SYN: neuroectodermal j..
- rectosigmoid j. the site at which the sigmoid colon becomes the rectum; usually takes the form of an acute angle, demarcated externally by a discontinuation of appendices epiploicae, a spreading out of the teniae coli to completely encircle the rectum, and consequently, termination of the sacculations (haustrae) between the teniae.
- right splicing j. boundary between the right end of an intron and the left end of the adjacent exon. SYN: acceptor splicing site.
- sacrococcygeal j. SYN: sacrococcygeal joint.
- sclerocorneal j. SYN: corneal limbus.
- squamocolumnar j. the site of transition from stratified squamous epithelium to columnar epithelium, usually characterized by stratified coboidal epithelium.
- ST j. SYN: J point.
- sternomanubrial j. SYN: manubriosternal symphysis.
- tight j. SYN: zonula occludens.
- tympanostapedial j. SYN: tympanostapedial syndesmosis.
- ureteropelvic j. (UPJ) site of origin of the ureter from the renal pelvis, a common location for congenital or acquired obstruction.
- ureterovesical j. the site of entry of the ureter into the bladder, with an oblique angulation through the detrusor to avoid reflux. SEE ALSO: vesicoureteral reflux.
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junc·tion 'jəŋ(k)-shən n a place or point of meeting <the structure of the synaptic \junction as revealed by electron microscopy> see NEUROMUSCULAR JUNCTION
junc·tion·al -shnəl, -shən-əl adj
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n.
(in anatomy) the point at which two different tissues or structures are in contact. See also neuromuscular junction.
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junc·tion (junkґshən) [L. junctus past part. of jungere to join] the place of meeting or of coming together, as of two different organs or types of tissue. junctional adjMedical dictionary. 2011.