22.5

Question 1

The large intestine has four components:

Answer 1

the cecum, colon, rectum, and anal canal.

Cecum –> Colon (ascending colon –> transverse colon –> descending colon –> sigmoid colon) –> rectum –> anal canal

Question 2

At the splenic flexure, the colon becomes the:

ascending colon.

transverse colon.

descending colon.

sigmoid colon.

Answer 2

At the splenic flexure, the colon becomes the:

ascending colon.

transverse colon.

descending colon.

sigmoid colon.

Question 3

The internal anal sphincter is controlled involuntarily while the external anal sphincter is controlled voluntarily.

True

False

Answer 3

The internal anal sphincter is controlled involuntarily while the external anal sphincter is controlled voluntarily.

True

False

Question 4

proximal large intestine (ascending and transverse colon);

Function:

• primary site of water and electrolyte absorption and bacterial activity;
• exhibits two main types of motility

distal large intestine (descending and sigmoid colon, rectum, anal canal);

Function:

• small amount of absorption, primarily of water,
• but its main role is to store fecal material until it is ready to be expelled during defecation

Question 5

Colon:

Answer 5

ascending colon, transverse colon, descending colon, sigmoid colon

Question 6

Histology of the Large Intestine [S151-152 (2)]

Mucosa of large intestine lacks villi and its cells lack microvilli

Structural adaptations reflect that nutrient absorption is not large intestine’s primary fxn

Mucosa is rich with goblet cells that secrete protective and lubricating mucus

Muscularis externa of large intestine is unique; the layer is gathered into three bands or ribbons of muscle (taeniae coli) (Figure 22.17a). Their constant tension bunches colon into pockets (haustra)

Serosa (visceral peritoneum) of large intestine contains fat-filled pouches (epiploic appendage)

Question 7

Large intestine houses many bacteria; make up as much as 60% of dry mass of feces

Useful functions: (1) produce vitamins, (2) metabolize undigested materials (soluble fibers) (3) deter the growth of pathogenic microorganisms (4) stimulate the immune system

Question 8

The proximal large intestine undergoes propulsive mass movements.

When mass movements propel fecal material into the distal colon and rectum, the defecation reflex is initiated, which is mediated by the parasympathetic nervous system and the cerebral cortex.

Question 9

Peristaltic contractions that propel the contents of the colon toward the distal large intestine are:

mass movements.

defecation.

segmentation.

haustral contractions.

Answer 9

Peristaltic contractions that propel the contents of the colon toward the distal large intestine are:

mass movements.

defecation.

segmentation.

haustral contractions.