Houston valve
Encyclopedia
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.
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
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
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
, 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
Sigmoidoscopy
Sigmoidoscopy From Greek Sigma - eidos - scopy, to look inside an s-like object, is the minimally invasive medical examination of the large intestine from the rectum through the last part of the colon. There are two types of sigmoidoscopy, flexible sigmoidoscopy, which uses a flexible endoscope,...
and colonoscopy
Colonoscopy
Colonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis and grants the opportunity for biopsy or removal of suspected...
.
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.
- One is situated near the commencement of the rectum, on the right side.
- A second extends inward from the left side of the tube, opposite the middle of the sacrumSacrumIn vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
. - A third, the largest and most constant, projects backward from the forepart of the rectum, opposite the fundus of the urinary bladderUrinary bladderThe urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
. - When a fourth is present, it is situated nearly 2.5 cm above the anus on the left and posterior wall of the tube.