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Motility in the colon

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Motility in the colon
Haustra

The colon absorbs water and electrolytes (most of it in the ascending colon) and colonic movements are slow to allow for this most important function to be accomplished.

Stores faecal matter and eliminates waste.

Nervous input is from the Sympathetic nervous system which decreases motility to enhance absorption of water.

Parasympathetic input from the vagus nerve above transverse colon and from the pelvic nerve below the transverse colon, which increases segmental movements and produces sustained contractions.

External anal sphincter is innervated by somatic fibres- under voluntary and reflex control.

Simultaneous contractions of the circular muscle and longitudinal muscle in segments of the colon result in outward bulging of the muscular colon wall. These sausage like bulges are called Haustra.

Haustra are segments that occur during segmental contractions of the smooth muscle in the colon. These Haustra allow for segmental mixing, kneading and churning so that the contents are exposed repeatedly to a large surface area for efficient absorption of water and electrolytes. The mixing also promotes incorporation of Bacteria, Mucus, insoluble fibre and Dead cells into the contents to form a stool of the consistency which can be easily evacuated.

Segmental contractions in the left colon provide resistance to movement of the contents towards the rectum to allow sufficient time for mixing and exposure of the contents to the colon lining for absorption of water and electrolytes .These contractions are increased and prolonged in people with constipation (holding on to faeces) and decreased in those suffering from diarrhoea (release of faecal content).

Mass movements

One to three times a day a small section (20cm) of the coon, particularly the Transverse Colon, contracts spontaneously and loses the segments that make up the Haustra. This mass wave of contraction propels a large mass of content down the descending colon and towards the Sigmoid colon and Rectum. This movement can be triggered by reflex from the stomach (Gastrocolic reflex) or duodenum (duodenal colic reflex)

 

 

 

Gastrocolic reflex

The presence content in the stomach causes distention which is sensed by mechanoreceptors in the muscular wall and initiates muscle contractions that lead to the creation of the Urge to defecate.


Orthocolic reflex

A generalized increase in colonic motility and mass movement of faecal material is initiated by the Orthocolic reflex. This reflex is activated by standing upright after reclining overnight. Getting out of bed , standing up and stretching activates this reflex. This explains why some people get the urge to open the bowel on rising and stretching from bed in the morning.

Duodenal colic reflex

Distention of the muscular wall of the duodenum occurs when food enters the duodenum after a meal. This distention provokes a mass movement by reflex contraction of the rectum and creates the urge to defecate that some people experience after a large meal.

 

 

Defecation reflex

The rectum is normally empty. Mass movement of the left side of the colon propels faeces from the sigmoid colon into the rectum. When the rectum is distended with faecal matter, the defecation urge is experienced. This urge to go is associated with reflex relaxation of the internal anal sphincter and reflex contraction of the external anal sphincter. This urge can be voluntarily suppressed, in which case both of the anal sphincters are contracted. Contraction of the rectum propels the faeces back into the sigmoid colon or the rectum may accommodate the faeces. If the urge to go is responded to, the defecation reflex is activated. Intra-abdominal pressure is increased by contractions of the abdominal muscle and diaphragm. The external and internal anal sphincters remain relaxed and faeces are evacuated through the anal opening.

Faeces propelled from the sigmoid colon to the rectum

>> >> Resulting distention at rectal wall stimulates stretch receptors or mechanoreceptors that initiate the defecation reflex that empties the rectum.

>>>> Stretch receptors send nerve impulses to the sacral spinal cord. These receptors can discriminate between solid, liquid and gas content and act accordingly.

>>>> Motor impulses from the spinal cord travel along parasympathetic nerves back to the descending colon, sigmoid colon, rectum and anus

>>>> Longitudinal muscles of the rectum contract, shortening the rectum and increasing the pressure within it

>>>> These pressures, along with voluntary contractions of diaphragm and abdominal muscles, plus parasympathetic stimulation, open the internal anal sphincter

>>>> The external anal sphincter is under voluntary control, and if opened, allows faeces to be expelled through the anus.

 

How to heal and prevent Bowel disorders

Diet is not about what you should NOT eat, it’s about what you should include in the diet that matters.
As long as your diet includes the correct balance of plant foods containing soluble fibre, insoluble fibre and resistant starch your colon will produce the perfectly formed stool. The important next step is to evacuate this stool without straining so that the body does not suffer from the pressures created each time the bowel is emptied.

In order to heal and prevent bowel disorders you need to make lifestyle changes that last the rest of your life time.

1. Include more fluids and plant food containing soluble fibre, insoluble fibre and resistant starch in the diet so that the perfectly formed stool will be made in the colon and beneficial bacteria will flourish and eliminate disease causing bacteria and fungi.

2. Evacuate the perfectly formed stool by adopting the squat posture to eliminate the need to strain during bowel movements.

It is not possible or safe to squat on the modern raised toilet seat installed in all western homes and it is impossible to squat for any length of time if you have not done this from childhood onwards. This makes the use of any raised platforms impossible to adapt to.

The SquattLooStool is designed to allow you to adopt the squat posture while seated comfortably on your raised toilet seat. The single best and easiest lifestyle change you will ever make, leading to a healthier body.