Large Intestine

Question 1

What are the 4 parts of the large intestine?

Answer 1

• cecum
• appendix
• colon
• rectum

Question 2

What is the cecum?

Answer 2

pouch situated at junction with small intestine

Question 3

What is the appendix?

Answer 3

lymphoid tissue housing immune cells

Question 4

What is the function of the colon?

Answer 4

(majority of large intestine) primary role is to absorb remaining water in feces, and store undigested material before defecation

Question 5

What are the 4 parts of the colon?

Answer 5

ascending colon
transverse colon
descending colon
sigmoid colon

Question 6

What does the rectum do?

Answer 6

stores fecal matter and empties through anus

Question 7

What are the two types of motility?

Answer 7

• haustral contractions

- mass movements

Question 8

What are haustral contractions?

Answer 8

exposes colonic contents to epithelial surface for water absorption

similar to segmentation, but occur less frequently (1 / 30 min)

Question 9

What are mass movements?

Answer 9

• peristaltic contractions 3-4 times daily
• ascending and transverse colon forcefully contract – pushes colonic contents into descending colon and rectum
• can move fecal material ¾ of length of colon in a few seconds

Question 10

What are mass movements triggered by?

Answer 10

entry of food into stomach via gastrocolic reflex – mediated by gastrin and ANS

Question 11

Defecation Reflex

What is the defecation reflex intitiated by?

Answer 11

when a mass movement fills rectum with fecal material

Question 12

Defecation Reflex

What does distension of the rectum wall trigger?

Answer 12

triggers ENS to:

• relax internal anal sphincter (smooth muscle)
• increase contraction force in sigmoid colon and rectum

initiates a conscious urge to defecate

Question 13

Defecation Reflex

When does defecation occur?

Answer 13

only occurs (normally) upon voluntary relaxation of external anal sphincter

Question 14

Defecation Reflex

What muscle is subject to fatigue?

Answer 14

skeletal muscle

Question 15

When does constipation occur?

Answer 15

when motility frequency is delayed for prolonged periods

Question 16

What can constipation present as?

Answer 16

discomfort 
headache 
loss of appetite 
nausea 
mild depression (via irritation due to distension)

Question 17

What might constipation arise from? (4)

Answer 17

• ignoring urge to defecate
• decreased intestinal motility associated with aging, emotion or low fibre diet
• obstruction associated with tumour or muscle spasm
• injury to nerves involved in defecation reflex

Question 18

What is appendicitis?

Answer 18

• fecal material lodged in appendix may impair circulation resulting in infection
• if inflamed appendicitis ruptures, infectious contents of appendix is introduced into sterile abdominal cavity
• potentially lethal