urorectal septum

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Related to urorectal septum: urogenital septum

ur·o·rec·tal sep·tum

in embryos, a partition dividing the cloaca into a dorsal, rectal portion and a ventral portion called the urogenital sinus; reaching the cloacal membrane at about the time of its disintegration, the urorectal septum divides the cloacal exit into an anal and a urogenital orifice.
Synonym(s): urorectal fold

urorectal septum

Etymology: Gk, ouron + L, rectus, straight, saeptum, wall
a ridge of mesoderm covered with endoderm that in the early developing embryo divides the endodermal cloaca into the urogenital sinus and the rectum. Also called cloacal septum.


pl. septa [L.] a wall or partition dividing a body space or cavity.
Some septa are membranous, some are composed of bone, and some of cartilage. The wall separating the atria of the heart, for instance, is called the interatrial septum.

atrioventricular septum
the part of the membranous portion of the interventricular septum between the left ventricle and the right atrium.
bulbar septum
a septum, formed by merging of the bulbar cushions, divides the bulbus cordis into aortic and pulmonary outflows.
cystic septum pellucidum
an embryonic malformation resulting in the formation of a fluid-filled cavity in the septum between the two lateral ventricles, instead of the normal glial raphe.
horizontal septum
in the avian body cavity there is no diaphragm but the cavity is divided into three compartments; this is one of the divider organs; thin and membranous for the most part, the septum forms the ventral boundary of paired cavities containing the lungs.
interalveolar septum
the bony partition between adjacent tooth sockets.
interatrial septum
the partition separating the right and left atria of the heart.
interlobar septum
a septum that converts an organ into lobes.
intermuscular septum
fascial septum separating muscle masses.
interorbital septum
bony partition between the large orbital cavities of birds.
interventricular septum
the partition separating the right and left ventricles of the heart. See also ventricular septum.
septum lucidum
septum pellucidum (below).
median septum
membranous partition in the ventral median fissure of the spinal cord.
oblique septum
a partition which divides the lower part of the bird's body cavity; the part of the cavity cranial to this septum contains the thoracic air sacs and the thoracic parts of the cervical and clavicular air sacs. The part of the body cavity caudal to this septum contains heart, liver, spleen, gastrointestinal, urinary and reproductive tracts and abdominal air sacs.
orbital septum
a fold which detaches from the periorbital fascia at the orbital rim, and which leads into the tarsi, the thickened margins of the eyelids.
septum pellucidum, pellucid septum
the triangular double membrane separating the anterior horns of the lateral ventricles of the brain. Called also septum lucidum, telencephalic septum.
pharyngeal septum
a transitory partition between the mouth and pharynx in the embryo.
septum primum
a septum in the embryonic heart, dividing the primitive atrium into right and left chambers.
rectovaginal septum
the membranous partition between the rectum and vagina.
rectovesical septum
a membranous partition separating the rectum from the prostate and urinary bladder.
septum secundum
develops during embryonic life to contribute to the formation of the foramen ovale between the cardiac atria.
telencephalic septum
see septum pellucidum (above).
septum transversum
a major contributor to the development of the diaphragm and the liver.
truncal septum
a partition which develops from truncal cushions within the truncus arteriosus and contributes to the separation of cardiac outflow into pulmonary and systemic circulations.
urorectal septum
a septum which divides the urinary passages from the hindgut in the embryo by horizontally partitioning the cloaca.


pertaining to or arising from the rectum and the urogenital sinus of the embryo.

urorectal fistula
congenital defect in the urorectal septum resulting in passage of urine through the rectum.
urorectal septal defects
principally urorectal fistula.
urorectal septum
divides the primitive fetal cloaca into dorsal rectum and ventral urogenital sinus.