Anatomy and function of the large intestine

1. Large Intestine …
★anatomy
★function

2. The large intestine comes after the small
intestine in the digestive tract and measures
approximately 1.5 meters in length in adult
humans.

4. ANATOMY

5. ➢cecum
➔ is the proximal end of the large intestine and is where
the large and small intestines meet at the ileocecel
junction.
➔ it is located in the right lower quadrantof the abdomen
near the iliac fossa.
➔ is a sac that extends inferiorly about 6cm past the
ileocecal junction.
➔ Appendix is attached to the cecum is a tube about 9 cm
long.

7. ➢colon
➔ is the last part of the digestive system in most
vertebrates. It extracts water and salt from solid wastes
before they are eliminated from the body and is the site
in which flora-aided (large bacterial) fermentation of
unabsorbed material occurs. Unlike the small intestine,
the colon does not play a major role in absorption of
foods and nutrients. However, the colon does absorb
water, sodium and some fat soluble vitamins.

9. The colon consists of four sections:
● Ascending colon - extends
superiorly from the right colic
flexure near the liver, where it
turns to the left.
- is a small caliber than
cecum
❖ to remove the water and other key
nutrients from waste material and recycle
it back into the body.
● Transverse colon- extends from
the right colic flexure to the left
colic flexure near the spleen,
where the colon turns inferiorly.
- longest and most movable
colon
❖ serve as a reservoir for liquid that comes
from the small intestine and also the
● Descending colon- extends from
the left colic flexure to the pelvic.
❖ is to store faeces that will be emptied into
the rectum.
● Sigmoid colon- forms an S-
shaped tube that extends
medially and then inferiorly into
the pelvic cavity and ends at the
rectum.
- forms a loop which average is
about 40 cm in length, and normally
lies within the pelvis.
❖ is to store fecal matter until the body is
ready to expel it.

12. ➔ Crypts - mucosal lining of the colon contains numerous straight tubular
glands
- contain many mucus- producing goblet cells
➔ Tenia coli - the longitudinal smooth muscle layer of the colon does not
completely envelope the intestinal wall but forms three bands

13. - is a straight , muscular tube that begins at the termination of the
sigmoid colon and ends at the anal canal. The muscular tunic is smooth muscle
and it is relatively thick in the rectum compared with the rest of the digestive
tract.
- is continuous above with the sigmoid colon, while below it ends in
anal canal. From its origin at the level of the third sacral vertebral its passes
downward, lying in the sacrococcygeal curve and extends for about 2.5 cm in
front of and a little below, the tip of the coccyx as far as the apex of the
prostate.
➢Rectum

15. Anal Canal
- the last 2-3 cm of the digestive tract. It can begins at the inferior end
of the rectum and ends at the anus.
- the smooth muscle of the anal canal is even thicker than that of the
rectum and forms the internal anal sphincter at the superior end of the anal
canal. The external anal sphincter at the inferior end of the anal canal is formed
by skeletal muscle.

17. FUNCTION
★ Absorbing water
★ Absorption of vitamins
★ Reducing acidity and protecting from infections
★ Producing antibodies

18. The large intestine takes about 16 hours to finish the digestion of the food.
It removes water and any remaining absorbable nutrients from the food before
sending the indigestible matter to the rectum. The colon absorbs vitamins
which are created by the colonic bacteria - such as vitamin K (especially
important as the daily ingestion of vitamin K is not normally enough to
maintain adequate blood coagulation), vitamin B12, thiamine and riboflavin. It
also compacts feces, and stores fecal matter in the rectum until it can be
discharged via the anus in defecation. The large intestine also secretes K+ and
Cl-. Chloride secretion increases in cystic fibrosis. Recycling of various
nutrients takes place in colon. Examples include fermentation of
carbohydrates, short chain fatty acids, and urea cycling.

19. Defecation is the final act of digestion by which organisms eliminate solid,
semisolid or liquid waste material (feces) from the digestive tractvia the anus.
Waves of muscular contraction known as peristalsis in the walls of the colon
move fecal matter through the digestive tract towards the rectum. Undigested
food may also be expelled this way; this process is called egestion.

20. Normal Functioning Defecation Reflex
A normal functioning defecation reflex produces a muscular
contraction that serves as a signal to the body that it is time to move
the bowels and eliminate stools. Prompt response to the defecation
reflex by going to the bathroom when it is activated, prevents stool
from drying out and becoming difficult to pass. The defecation reflex
may be triggered about 45 minutes to an hour upon rising from
sleep, after drinking a hot beverage, or after eating a meal. The
defecation reflex will disengage after about 15 minutes of being
ignored. Like any other muscle that is not used, it will breakdown
and fail to function if continuously ignored. When the defecation
reflex is ignored, constipation will result as the stool that is retained
in the colon becomes dried out, hard and difficult to pass. Retained
waste can stretch out the rectal sack. A stretched out rectal sack
requires more and more stool to fill the rectal sack before the reflex
will be activated. This causes even more stool to dry out as it collects
behind the previously retained stool.