digestion pt 2pg 3-4

Villi greatly increase the surface area,

making the small intestine the most absorbing organ

Absorptive enzymes are secreted by

the intestinal mucosa and pancreas

Carbohydrate digestion begins

in the mouth with the activity of salivary amylase and is completed in the small intestine

Protein digestion

begins in the stomach as a result of pepsin activity and is completed in the small intestine

Movements of the Small Intestine

Small intestine carries on mixing movements and peristalsis

Segmentation

is the major mixing motion

Rhythmic,

small ring-like contractions cut the chyme into segments and move it

Rhythmic also

Also slows the movement of chyme through the small intestine

Parasympathetic impulses

enhance the mixing and peristaltic movements; sympathetic impulses inhibit them

Ileocecal sphincter

joins the small intestine’s ileum to the large intestine’s cecum

Ileocecal sphincter also

Prevents the contents of the small intestine from entering the large intestine, as well as prevents backflow

Large Intestine

Cecum

Hangs slightly inferior to the ileocecal opening Appendix projects downward from it

ascending Colon

Ascending colon begins at the cecum and extends upward against the posterior abdominal wall

transverse colon

At the level of the liver, it makes a sharp turn to the left, becoming the transverse colon

descending colon

as the transverse colon approaches the spleen, it turns downward and becomes the

sigmoid colon

At the brim of the pelvis, the colon makes an S-shaped curve, called the sigmoid colon, and then becomes the rectum

Rectum

lies next to the sacrum and ends about 5cm inferior to the tip of the coccyx, where it becomes the anal canal

Anal canal

At the distal end, the canal opens to the outside as the anus

how many sphincter guard the ans

Two sphincter muscles guard the anus

internal anal sphincter muscle –

composed of smooth muscle under involuntary control

External anal sphincter muscle –

composed of skeletal muscle under voluntary contro

the large intestine absorbs

water and electrolytes remaining in the alimentary canal

it also

forms and stores feces

in the large intestine mucus is

the large intestine’s only significant secretion

Intestinal flora –

bacteria that normally inhabit the large intestine

in the large intestine Mixing movements

break down the fecal matter into segments and turn it so that all portions are exposed to the intestinal mucosa

how many time does peristaltic waves happen a day

2-3 a day, producing mass movements that force intestinal contents toward the rectum

Feces are composed of

materials not digested or absorbed, along with water, electrolytes, mucus, and bacteria