Physiology

Question 1

What are the 3 general roles of the large intestine?

Answer 1

Ion and water absorption, storage of feces, and digestion by microbial enzymes

Question 2

T/F: There are villi in the colon.

Answer 2

F

Question 3

What are surface epithelial cells of the colon responsible for?

Answer 3

Electrolyte absorption

Question 4

What are colonic gland cells responsible for?

Answer 4

Mediate ion secretion

Question 5

What does the ileocecal sphincter prevent?

Answer 5

Retrograde movement of colon contents into the ileum

Question 6

When does the ileocecal sphincter relax to allow movement of material into the colon?
A. During periods of peristaltic activity in the ileum
B. When colonic pressure increases
C. When there is chemical irritation in cecum
D. None of the above

Answer 6

A, during periods of peristaltic activity in the ileum

Question 7

What is the function of retropulsion or antiperistalsis and what areas initiate these contractions?

Answer 7

Moves food orally to allow for more mixing, ion, and water absorption; Pacemaker areas initiate contraction

Question 8

The stimulation of what reflex during and after meals causes mass movements of material?

Answer 8

Gastrocolic reflex

Question 9

The retrosphincteric reflex is a sympathetic/parasympathetic response that causes the terminal portion of the colon to contract, while the internal anal sphincter muscle contracts/relaxes.

Answer 9

Parasympathetic, relaxes

Question 10

When an animal receives a conscious need to empty the rectum due to the stimulation of the rectosphincteric reflex, some species are able to voluntarily close the internal/external anal sphincter.

Answer 10

External anal sphincter

Question 11

What stimulates the rectosphincteric reflex?

Answer 11

Movements of large intestine force content into the rectum stimulate sensitive sensory cells in the walls of the rectum

Question 12

What type of muscle is the internal anal sphincter?

Answer 12

Smooth muscle

Question 13

What type of muscle is the external anal sphincter?

Answer 13

Skeletal muscle

Question 14

How are ions (sodium and chloride) absorbed in the large intestine?

Answer 14

Sodium moves via Na-K ATPase pump; chloride follows sodium

Question 15

How is water absorbed in the large intestine?

Answer 15

Osmosis - follows sodium

Question 16

What is the primary mechanism of potassium absorption?

Answer 16

Passive diffusion

Question 17

What is potassium absorption dependent on?

Answer 17

Water absorption

Question 18

Why is absorption of potassium impaired with diarrhea?

Answer 18

Because water absorption is also impaired, so K+ in the gut lumen is diluted and can’t be absorbed

Question 19

Once digesta passes through the lumen and into the large intestine, does enzymatic digestion occur?

Answer 19

No

Question 20

T/F: Lignin increases with age and temperature, so young, cool weather plants are considered more digestible.

Answer 20

T

Question 21

Describe the route that ingesta goes when it enters the colon in horses.

Answer 21

Enters the right ventral colon -> sternal flexure -> left ventral colon -> pelvic flexure -> left dorsal colon -> diaphragmatic flexure -> right dorsal colon -> transverse colon -> descending colon -> rectum

Question 22

What is cecal flush in the horse?

Answer 22

Strong contraction of cecal muscles in a mass movement in which the body and apex of cecum shorten and constrict, lifting ingesta into the base -> constriction of base forces material through the cecocolic orifice and into the RVC

Question 23

Do horses have retrograde flow of material from colon back into the cecum like other species?

Answer 23

No