"Septa" is the plural of "septum":
http://en.wikipedia.org/wiki/Septum
A septum, in Latin meaning "something that encloses", is a partition separating two cavities or two spaces containing a less dense material.
In anatomy:
· Septum nasi, or simply septum, is the cartilage wall separating the two nostrils
· Septum pellucidum, or septum lucidum, is a thin structure separating two fluid pockets in the brain
(...)
In other fields of biology:
· Septa (biology), in marine biology, the thin membrane separating each siphuncle, or chamber, in the shells of nautiloids, ammonites, and belemnites—all cephalopods that retained their external shell.
· Histological septa are seen throughout most tissues of the body, particularly where they are needed to stiffen a soft cellular tissue, and they also provide planes of ingress for small blood vessels...
Septum may also refer to:
· Man-made dividers, such as those used to close vials of injectable fluid. These may be designed to be pierced by a hypodermic needle.
· Septum magneta and Electrostatic septum are two types of septa that can deflect an ejected beam while not affecting the orbiting beam. These devices are used with a circular particle beam accelerator to inject or eject a beam of particles to or from an accelerator.

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Note added at 3 hrs (2006-10-02 03:27:19 GMT)
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SEPT:
http://www.rjhrm.ro/dump_articol.php?id_numar=8&id_articol=5...
When dissecting the lateral brachial intermuscular septum, its vessels and bone insertion are spared, so the septum - bone relationships are preserved in their integrity. The vascular branches are cauterized far from the septum. Usually the flap vessels can be observed through the septum and when the harvesting operation is done without tourniquet their pulsation can be seen. A protective coating of 3-5 mm of muscle is left on both sides of the septum in order to protect the vessels. When the bone is reached, the muscles are taken off all along the septum length on its both sizes, thus denuding the bone anteriorly and posteriorly to the septum...
http://www.rjhrm.ro/dump_articol.php?id_numar=8&id_articol=5...
Ajungînd cu disecţia la septul intermuscular lateral al braţului, ultimul se menajează împreună cu vasele şi locul de inserţie pe os, astfel încît relaţiile sept-os rămân integre. Ramurile musculare se cauterizează la distanţăde sept. De obicei prin sept se văd vasele lamboului. În cazul cînd operaţia se face fără garou pulsaţia lor poate fi sesizatăcu ochiul liber. Pentru o protecţie mai sigură a vaselor lăsăm să adere de sept pe ambele părţi un strat muscular de 3–5 mm. Ajunşi la os, pe toată lungimea septului decolăm cu răzuşul muşchii rămaşi în afara septului de ambele părţi, dezgolind astfel osul anterior şi posterior de sept.

"Septa" is a Latin term usually used in medicine but not necessary and means "wall" or some kind of barrier, smth limiting or enclosing. This form is plural to "septum" which means "Septa" in Ro language. So SEPTA=SEPTE, Baroere.