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Movements of Large Intestine - Coggle Diagram
Movements of Large Intestine
Two main types of waves of contractions
Segmental Contractions (or Haustrations)
are of 2 types
Type I contractions
These are small amplitude waves which cause pressure rise upto 5 cm saline.
They occur at a frequency of 10-12/min
and are of 5 sec duration.
Function:
aid mixing of the contents of the colon.
Type II contractions
These are larger pressure waves as compared to type I contractions;
occur at a frequency of 1-2/min and
last for about 30 sec.
Functions:
aid mixing of the contents of the colon; and
facilitate absorption by exposing more of the contents to the mucosa.
Peristaltic Contractions
are also of 2 types
Type III contractions.
These are very small pressure waves of prolonged duration.
Function:
They propel the contents
towards the rectum.
Type IV contractions.
Mass Peristalsis or Mass Action Contractions.
These are simultaneous contractions of the smooth muscle occurring at
the same time over a large portion of the colon.
These contractions
occur more in the descending and sigmoid colon.
They last for 3-4minutes
with pressure rising steeply to a peak upto 100 cm saline,
and
then decline slowly.
Function:
These contractions propel contents from
the caecal region towards the rectum i.e. serve to empty the colon
rapidly.
They are the predominant contraction force during
defecation