The main function of the anal sphincter is to control the release of intestinal contents. It consists of the external and internal parts.
External anal sphincter
External sphincter portion is an annular structure consisting of striated muscles surrounding the anal canal. External sphincter can be controlled by the human mind.
At length, he is 8-10 cm. And its thickness - 2, 5 cm. Striated sphincter muscles go pubic-proctal muscle.
External sphincter muscle portion is divided into three layers:
- Subcutaneous muscle is an annular muscle;
- Superficial muscles - elliptical muscle attached to the coccyx;
- Deep muscle is closely linked to the pubic-rectal muscle.
The muscles of the outer part of the anus grasping the lower part of the internal sphincter. Despite the fact that the sphincters close contact between them there is a clear boundary.
The external anal sphincter muscles are stretch receptors. A healthy adult can easily control the passage of stool through the sphincter and their consistency. Rektoanalny reflex is to compress the external anal sphincter muscle. Defecation reaction occurs as a result of a sharp increase in intra-abdominal pressure, which arises as a result of intrarectal pressure and internal anal sphincter relaxes.
The internal anal sphincter
The inner part is a smooth muscle sphincter annular structure surrounding the anal canal. It starts from the inner circular muscle layer of the rectum, and at the bottom is connected to the skin of the anus. At the bottom of the internal sphincter external sphincter muscles clasped.
Internal sphincter portion has a thickness of about 5 mm, and the length - 25-30 mm. The lower limit of the sphincter located at a distance of about 5-6 mm from the anus. His muscle fibers are inclined axially intestine and the center line of the rectum.
In contrast, external, internal anal sphincter is not controlled by the human mind. His relaxation and contractions occur involuntarily. Normally, the internal sphincter reduced. His reflex relaxation is the result of irritation of the rectum stool. Colon peristalsis does not affect the state of the sphincter.
The main function of the internal sphincter is a valve, that is, it does not happen to the passage of liquids and gases feces.
The valve function of the internal sphincter carried out thanks to a three-tier system:
- Intramural level;
- Spinal level;
- Suprasegmental level, located in different parts of the brain.
Spinal and intramural levels made parasympathetic and sympathetic nervous system. Sympathetic fibers to keep the sphincter is constantly contracted state and slows down the motor activity of the colon. Parasympathetic fibers, on the contrary, the sphincter relaxes and stimulates motility of the colon.
The defects of the anal sphincter
The most common defects are the anal sphincter:
- Insufficiency of anal sphincter;
- Anal fissure.
Failure of the anal sphincter is called total or partial breach of any retention of feces.
Normally, the sphincter is capable of holding gaseous, liquid and solid contents of the colon not only in different positions of the body, but when you sneeze, cough strong, physical activity, etc.
The most common cause of failure is injuries, mostly, postoperative. Also, failure can occur due to changes in muscle structure or neuro-reflex disorders. The most common causes of these disorders are diseases of the anus or rectum, such as hemorrhoids, rectal prolapse, or a variety of inflammatory diseases. Less common cause of failure are malformation of the anal canal and rectum.
There are three degrees of failure of the anal sphincter:
- The first degree when the patient is not capable of retaining gases;
- The second degree, when the patient can not hold the liquid feces and gas;
- Third degree - total incontinence.
Anal fissure - injury of the mucous membrane of the anus.
An anal fissure is very common among the diseases of the colon is the third largest (after colitis and hemorrhoids).
There is anal
crack due to various causes. The most common cause - injury of the mucous membrane while passing hard stools. Contributing factors for its occurrence is the presence of colitis, hemorrhoids, enterocolitis, proctosigmoiditis. Almost 70% of patients crack combined with chronic diseases of the upper gastrointestinal tract (stomach ulcers, gastritis, cholecystitis). The same number of patients with anal fissure combined presence of hemorrhoids.
For anal fissure is characterized by three symptoms:
- Slightly bleeding during a bowel movement;
- Spasm of the anal sphincter;
- Pain in the anus during or immediately after a bowel movement.
Pain in the anus characteristic of acute and chronic fissures. As a result, pain patients seek as little as possible to carry out the act of defecation, leading to constipation. Further, the pain may cause anal sphincter spasm, which, in turn, only enhances pain. Spasm of the anal sphincter is observed in approximately 60% of patients with anal fissures.
Bleeding from the anus relatively small and appear as a result of injury to crack. More abundant amount of bleeding indicate the presence of hemorrhoids or tumors.