Transverse folds of rectum

Transverse folds of rectum
Coronal section of rectum and anal canal.
Anatomy of the anus and rectum
Details
Identifiers
Latin	Plicae transversae recti
Dorlands /Elsevier	p_24/12649311
TA	A05.7.04.007
FMA	75657
Anatomical terminology []

The transverse folds of rectum (or Houston's valves) are semi-lunar transverse folds of the rectal wall that protrude into the rectum, not the anal canal as that lies below the rectum. Their use seems to be to support the weight of fecal matter, and prevent its urging toward the anus, which would produce a strong urge to defecate. Although the term rectum means straight, these transverse folds overlap each other during the empty state of the intestine to such an extent that, as Houston remarked, they require considerable maneuvering to conduct an instrument along the canal, as often occurs in sigmoidoscopy and colonoscopy.

These folds are about 12 mm. in width and are composed of the circular muscle coat of the rectum. They are usually three in number; sometimes a fourth is found, and occasionally only two are present.

Transverse folds were first described by Irish–British anatomist John Houston, curator of the Royal College of Surgeons in Ireland Museum, in 1830. They appear to be peculiar to human physiology: Baur (1863) looked for Houston's valves in a number of mammals, including wolf, bear, rhinoceros, and several Old World primates, but found no evidence. They are formed very early during human development, and may be visible in embryos of as little as 55 mm in length (10 weeks of gestational age.)

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)