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The rectum is the final straight portion of the large intestine in humans and some other mammals. It is a tube of skeletal muscle that extends upward to meet the puborectalis and levator ani muscles. The rectum is located at the last few inches of the large intestine and is about 12 centimetres long. It receives waste from the colon and stores it until it passes out of the body through the anus. The anus is the opening at the lower end of the rectum through which stool is passed from the body. The anal sphincter is a pair of muscles at the end of the rectum that controls the release of stool.
| Characteristics | Values |
|---|---|
| Definition | The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. |
| Length | The adult human rectum is about 12 centimetres (4.7 inches) long. Another source states it is about 15 cm (6 inches) long. |
| Function | The rectum receives waste from the colon and stores it until it passes out of the body through the anus. |
| Microanatomy | The rectum possesses a mucosa with a lining of a single layer of column-shaped cells with mucus-secreting goblet cells interspersed, resting on a lamina propria, with a layer of smooth muscle called muscularis mucosa. |
| Muscles | The rectum is associated with the internal and external anal sphincter muscles, the puborectalis muscle, and the pelvic floor muscles. |
| Medical procedures | Medical procedures involving the rectum include a rectal exam, a proctoscope, a colonoscopy, a sigmoidoscopy, and Delorme's procedure. |
| Medication administration | Some medications are administered via the rectum, including suppositories and enemas. |
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What You'll Learn
The rectum is a muscle with a mucosa lining
The rectum is a part of the large intestine in humans and some other mammals. It is the final straight portion of the intestine, which is about 12-15 cm long in adults. The rectum is connected to the sigmoid colon and ends at the level of the anorectal ring or the dentate line. The rectum's primary function is to store waste from the colon before it passes out of the body through the anus.
The rectum is indeed a muscle, with several other muscles surrounding and supporting it. These include the puborectalis muscle, which wraps around the lower rectum and creates an angle to keep stool in. The rectum also has an internal and external anal sphincter, which are a pair of muscles at the end of the rectum that control the release of stool. The internal sphincter is contracted at rest and relaxes as the rectum fills with stool, while the external sphincter can be squeezed to hold stool in.
In addition to these muscles, the rectum also has a mucosa lining. The microanatomy of the rectum wall is similar to the rest of the gastrointestinal tract, with a single layer of column-shaped cells and mucus-secreting goblet cells. This mucosa layer sits on a submucosa of connective tissue, surrounded by a muscularis propria of two bands of muscle: an inner circular band and an outer longitudinal one. The mucosa lining of the rectum changes at the point where it meets the anus, with column-shaped cells changing to multiple layers of flat cells.
The rectum's muscles and mucosa lining work together to facilitate the passage of waste from the body. During defecation, the rectal muscles contract, and the puborectalis muscle relaxes, straightening the rectum and facilitating the expulsion of stool. The anal sphincter muscles also play a crucial role in controlling the release of stool, with the internal sphincter contracting at rest and relaxing as the rectum fills, and the external sphincter being squeezed to hold stool in.
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The rectum is part of the large intestine
The rectum is indeed part of the large intestine, forming the last straight portion of the intestine in humans and some other mammals. The rectum is a short tube that connects to the sigmoid colon, the last part of the colon. The rectum is about 12-15 cm long in adults, and it is responsible for temporarily storing waste before it is expelled from the body through the anus.
The microanatomy of the rectum wall is similar to the rest of the gastrointestinal tract, with a mucosa lining consisting of a single layer of column-shaped cells interspersed with mucus-secreting goblet cells. This rests on a lamina propria, with a layer of smooth muscle called the muscularis mucosa. The submucosa, which lies beneath the mucosa, is composed of connective tissue and is surrounded by a muscularis propria consisting of two bands of muscle: an inner circular band and an outer longitudinal band.
The rectum plays a crucial role in the digestive process, receiving waste from the colon and storing it until it is ready to be eliminated from the body. As the rectum fills with stool, the internal anal sphincter relaxes, and the person feels the urge to go to the bathroom. During a bowel movement, the rectum contracts, and the stool is pushed through the anus.
Several muscles work in coordination to facilitate defecation. The pelvic floor muscles and the anal sphincter, which consists of the internal and external anal sphincters, control when stools are released. The puborectalis muscle, a loop of muscle surrounding the lower rectum, also plays a role in maintaining continence by creating an angle in the rectum when contracted. During defecation, the puborectalis muscle relaxes, straightening the rectum and facilitating the passage of stool.
The rectum is also involved in medical procedures and treatments. For example, rectal exams and medical imaging techniques such as CT scans, MRI scans, and ultrasound probes may be used to examine the rectum and nearby structures. Additionally, medications and treatments for conditions like haemorrhoids and fissures can be administered via the rectum.
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The rectum is surrounded by other organs
The rectum is indeed a muscle. It is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The rectum receives faecal material from the descending colon through regular muscle contractions called peristalsis.
The rectum is surrounded by a mesentery called the mesorectum. The rectum is also closely associated with the rectal venous plexus, though this structure is more related to the anal canal. The rectum receives sensory and autonomic innervation. Sympathetic nervous supply to the rectum is from the lumbar splanchnic nerves and superior and inferior hypogastric plexuses. Parasympathetic supply is from S2-4 via the pelvic splanchnic nerves and inferior hypogastric plexuses.
The rectum is located within the pelvic cavity and is surrounded by other organs including the spleen, liver, pancreas, bladder, and reproductive organs. The rectum is held in the abdomen by folds of tissue called mesenteries. In males, the reflection of peritoneum from the rectum to the posterior bladder wall forms the rectovesical pouch. In females, the peritoneum reflects to the posterior vagina and cervix, forming the rectouterine pouch (pouch of Douglas).
The rectum is followed by the anal canal, which is about 4 centimetres (1.6 inches) long, before the gastrointestinal tract terminates at the anal verge. The anal canal passes through the pelvic floor to end as the anus. The anus is the opening at the lower end of the rectum through which stool is passed from the body.
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The rectum is connected to the colon
The rectum is a straight, muscular tube that forms the final portion of the large intestine in humans and some other mammals. It is preceded by the sigmoid colon, which is the last part of the colon and connects to the rectum. The rectum is about 12-15 cm long in adults and is responsible for temporarily storing faeces before expulsion through the anus.
The colon and rectum are surrounded by other organs, including the spleen, liver, pancreas, bladder, and reproductive organs. They are held in the abdomen by folds of tissue called mesenteries. The colon is the longest part of the large intestine and receives partially digested food from the small intestine. It absorbs water and nutrients and passes waste to the rectum.
The rectum is connected to the sigmoid colon at the rectosigmoid junction, which is located at the level of the third sacral vertebra or the sacral promontory. The rectum then terminates at the level of the anorectal ring or the dentate line, followed by the anal canal before the gastrointestinal tract ends at the anal verge. The anal sphincter, a group of muscles at the end of the rectum, surrounds the anus and controls the release of stool.
The microanatomy of the rectal wall is similar to the rest of the gastrointestinal tract, with a mucosa lined by a single layer of column-shaped cells interspersed with mucus-secreting goblet cells. This rests on a lamina propria, with a layer of smooth muscle called the muscularis mucosa. The rectal wall also has an underlying submucosa of connective tissue surrounded by a muscularis propria consisting of two bands of muscle: an inner circular band and an outer longitudinal band.
The rectum and colon work together to facilitate the passage of waste out of the body. Stool moves from the colon into the rectum, causing it to stretch and trigger the feeling of needing to go to the bathroom. The rectum contracts to push the stool through the anus, with the help of coordinated contractions from the abdominal wall muscles.
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The rectum is used to store stool
The rectum is the final straight portion of the large intestine in humans and some other mammals. It is about 12 centimetres (4.7 inches) long and is located at the last few inches of the large intestine (colon). The rectum is connected to the sigmoid colon, which is the last part of the colon.
The process of defecation involves the coordination of several muscles. In a normal resting state, the internal anal sphincter is contracted, and the puborectalis muscle creates an angle in the rectum to keep the stool in. The puborectalis muscle is a loop of muscle that wraps around the lower rectum. As the rectum fills with stool, the internal sphincter relaxes, but a person can voluntarily squeeze the external sphincter to hold the stool in.
Squeezing the external sphincter also causes the puborectalis muscle to contract, making the rectum more angled, which further helps to keep the stool in. During defecation, the rectum contracts, and the stool is pushed through the anus and leaves the body. Muscles in the abdominal wall contract, increasing pressure in the rectum and helping to push the stool down.
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Frequently asked questions
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. It is about 12 centimetres long and stores faeces before they are expelled through the anus.
The rectum is not a muscle, but it does contain muscles. The rectum has a layer of smooth muscle called the muscularis mucosa, which sits on an underlying submucosa of connective tissue. The rectum also has a muscularis propria of two bands of muscle, an inner circular band and an outer longitudinal one.
The rectum contains the internal and external anal sphincter muscles, which control the release of stool. The puborectalis muscle is a loop of muscle that wraps around the lower rectum and creates an angle in the rectum to keep stool in.
The internal anal sphincter is contracted at rest to keep stool in, but relaxes as the rectum fills with stool. The external anal sphincter can be squeezed to hold stool in, which also causes the puborectalis muscle to contract and straighten the rectum.
