Anus Definition, Parts and Function

Playing an important role in the excretion of digestive wastes, the anal opening constitutes the posterior most part of the gastrointestinal system. Lined by two round muscular structures, the opening and closing of the hole is under the voluntary control of an individual. It is not completely functional in the human babies; however, as the child advances towards maturity, it is brought under deliberate command. On the attainment of puberty in an individual, pubis hair starts to grow around the anal opening. Did you ever imagine, “How would your social life be if you were unable to hold and prolong feces before you reach toilet for defecation”? However, if defecation is prolonged for an extended duration, the excretory matter is expelled backwards into colon for the further absorption of fluids, salts and any other useful substances.

Parts of Anus

The ring-shaped structure is bound by two layers of muscles, thus forming internal anal sphincter and external anal sphincter. However, both of these cannot be brought under your deliberate command, i.e. the interior one is involuntary while the external sphincter can by controlled by voluntary actions. They vary in their length while running along the anal canal where internal muscle extend up to 4 centimeter and the external one reaches the maximum size of 10 centimeter or more. The outer muscular layer retracts during the process of defecation and is further composed of two strata, viz. deeper and the superficial one (the main portion).

Functions of Anus

The major function of anal canal is the accomplishment of excretory process, but it is also closely associated with sexuality. The sexual feature is owed to its proximity with the sensitive parts of male and female genitals and anal sex leads to intense sexual arousal. For excretion, the internal involuntary sphincter operates under the command of autonomous nervous system while the external one can be deliberately opened or forcefully contracted with your own will. It is a very important function of the posterior aperture, or else you won’t be able to hold the bowels for some time in order to reach the place of defecation. Moreover, the capacity of rectal storage and sensation caused by the arrival of waste products in the region inspire the need for their removal. As the waste, semi-solid substances fill the rectum and anal canal, the surrounding walls are stretched. The nerve endings present at the region deliver the stimulus to the brain which is processed there and appropriate response is generated. When the responding signal reaches the target place, it induces the desire for defecation in the individual who then takes appropriate action accordingly.

Diseases of Anus

There have been reported a number of conditions associated with the anal aperture which not only disturb the excretory function of your digestive system, but are also the cause of great embarrassment for the victim. Some of the disorders are infectious while the other may be viral, cancerous, and those which are owed to mechanical reasons. Some of the most frequently occurring ailments of excretory orifice include anal abscesses, anal fistula, hemorrhoids, anal fissures, and so on. The diagnostic symptoms of such acute and chronic conditions may be accompanied by pain, intense sensation of burning, bleeding, cramps, inflammation, bowel obstruction, release of pus, chills, fever, and so on. The suggestion and application of treatment strategy depends upon the type and severity of the condition and may involve medication, diet supplementation, surgical removal of the infected part, and so on. However, if you take preventive measures in advance and, in case of attack of the disease, consult your health care provider immediately, you can save your life from all such hassles.