The huge intestine is the final section of the gastrointestinal system prior to the rectum. In this ar of the GI tract water is reabsorbed and also any remaining waste product is stored together faeces to it is in removed. Additional information ~ above the anatomy the the large intestine deserve to be found here.

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This article shall take into consideration the physiological process of defecation and clinical conditions that may occur throughout dysfunction.


The rectum is reponsible for temporary storage that faeces prior to defecation. As it i do not care filled the rectal wall surfaces expand and stretch receptors wake up the desire to defecate. The urge to defecate arises from convulsion of rectal muscles, relaxation of the internal anal sphincter and an initial convulsion of the external anal sphincter.

If the advice is no acted upon further water is took in and the faeces is stored till the next mass movement occurs. An ext information top top the anatomy of the rectum can be found here.


Fig 1 – Sagittal ar of the woman pelvis, reflecting the anatomical place of the rectum.


There are two key anal sphincters; one internal and also external sphincter. The inner anal sphincter is managed by parasympathetic fibres i beg your pardon relax involuntarily. The outside anal sphincter is skeleton muscle the is controlled by somatic nerve supply from the inferior anal branch that the Pudendal nerve (S2,3,4), which allows conscious manage of defecation.

When the rectum is distended the rectosphincteric reflex is initiated and also relaxes the interior sphincter. If defecation is no desired, voluntary contraction of the outside sphincter can hold-up it. If defecation is appropriate, climate a series of reflexes take location that lead to:

Relaxation the the outside sphincterContraction of abdominal wall musclesRelaxation the pelvic wall muscles

Peristaltic waves then facilitate the activity of faeces through the anal canal. Defecation can also be helped by taking a deep breath and also attempting to expel the air against a closed glottis, this is recognized as the Valsalva maneuver.

However, if a hold-up in defection is essential then voluntary convulsion of the outside sphincter is usually enough to override the reflexes that anal distension initiates.

Clinical relevance – Faecal Incontinence

Defecation deserve to either it is in voluntary or involuntary depending upon the situation. Young kids learn voluntary control of the process during restroom training and it commonly remains under voluntary manage throughout life. But in some instances loss of regulate may occur, particularly if defecation occurs as well quickly, before excess water has actually been absorbed and diarrhoea occurs.

Other reasons of faecal incontinence include:

Physical injuryNerve injurySurgeryIntense frightInflammatory bowel diseaseChildbirth

Treatments deserve to vary relying on the reason of the incontinence and how easily it can be corrected.

Clinical relevance – Laxatives

Laxatives are offered in the treatment of constipation. There are two main types of laxative: mass laxatives e.g: Isphagula husk and stimulant laxatives e.g. Senna.

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A mass laxative to add fibre to the components of the intestine increasing the mass hence stimulating the wall surfaces of the intestine to reason peristalsis, therefore increasing activity of the bowels, reducing constipation. Stimulant laxatives work on sensory receptors in the wall of the intestine to increase the amount of water and electrolytes being preserved in the gut. This in turn reasons peristalsis helping to north the bowels.