orbital septum (redirected from arcus marginale)

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.

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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.

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orbital septum 

A thin membrane containing collagenous and elastic fibres which is attached to the orbital margin at a thickening called the arcus marginale. It is continuous with the tarsal plates of the upper and lower eyelids except where it is pierced by the fibres of the levator palpebrae superioris muscle in the upper lid and the expansion from the inferior rectus in the lower lid. Syn. palpebral fascia; septum orbitale. See dermatochalasis; eyelids; tarsus.