Look up septum in Wiktionary, the free dictionary.

In anatomy, a septum (Latin for something that encloses; plural septa) is a wall, dividing a cavity or structure into smaller ones.

Examples[link]

In human anatomy[link]

• Interatrial septum, the wall of tissue that is a sectional part of the left and right atria of the heart
• Interventricular septum or median septum, the wall separating the left and right ventricles of the heart
• Lingual septum, a vertical layer of fibrous tissue that separates the halves of the tongue
• Nasal septum: the cartilage wall separating the nostrils of the nose

Alveolar septa (AS)

• Alveolar septum: the thin wall which separates the alveoli from each other in the lungs
• Orbital septum, a palpabral ligament in the upper and lower eyelids
• Septum pellucidum or septum lucidum, a thin structure separating two fluid pockets in the brain
• Medial septum, a cluster of neurons in close proximity to the septum pellucidum
• Uterine septum, a malformation of the uterus
• Vaginal septum, a lateral or transverse partition inside the vagina

Histological septa are seen throughout most tissues of the body, particularly where they are needed to stiffen soft cellular tissue, and they also provide planes of ingress for small blood vessels. Because the dense collagen fibres of a septum usually extend out into the softer adjacent tissues, microscopic fibrous septa are less clearly defined than the macroscopic types of septa listed above. In rare instances, a septum is a cross-wall.

In zoology[link]

• One of the radial calcareous plates of a coral. b. One of the transverse partitions dividing the shell of a mollusk, or of a rhizopod, into several chambers. c. One of the transverse partitions dividing the body cavity of an annelid.
• Septum (marine biology): walls between each chamber, or siphuncle, in shells of nautiloids, ammonites, and belemnites; i.e. cephalopods that retain an external shell.

In mycology[link]

• A partition dividing filamentous hyphae into discrete cells in fungi

In botany[link]

• A partition that separates the locules of a fruit, anther, or sporangium.