Large intestine

Question 1

Describe the anatomical components of the large intestine and state a function for each.

Answer 1

1. cecum- pouch at junction with small intestine
2. appendix- lymphoid tissue with immune cells
3. colon- majority of large intestine. consists of:
   - ascending
   - transverse
   - descending
   - sigmoid
4. rectum- stores fecal matter

primary role large = absorb remaining water in feces, store undigested material

Question 2

Motility: Differentiate between haustral contractions and mass movements and state the function and control mechanism(s) for each.

Answer 2

haustral: similar to segmentation, but less frequent. expose colonic contents to epithelial surface for water absorption

mass movements: peristaltic contractions 3-4 times/day.

• ascending and transverse colon forceful contract, pushes content down
• can move fecal matter 3/4 length of colon in few sec
• triggered by foot entry via gastrocolic reflex mediated by gastrin and ANS

Question 3

Motility: Describe the defecation reflex and factors that control defecation.

Answer 3

mass movement fills rectum, distention rectal wall triggers ENS to:

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

also initiates conscious urge to poo
poo only happens upon voluntary relaxation of external anal sphincter

Question 4

Motility: Define constipation and discuss its potential causes and complications

Answer 4

delayed motility for prolonged periods
- discomfort, headache, loss appetite, nausea, depression

can arise from:

• ignoring urge to poo
• decreased motility from aging, emotion, low fiber
• obstruction (tumor/spasm)
• injury to nerves

appendicitis- fecal material lodged in appendix, impair circulation = infection
- if inflamed, ruptures, infectious content introduced to sterile abdominal cavity. lethal