The digestive system-4

Question 1

Site where most digestion and absorption take place

Answer 1

Small intestine

Question 2

Three segments of the small intestine:

Answer 2

Duodenum
Jejunum
Ileum

Question 3

Motility of the small intestine?

Answer 3

• Segmentation

- Migrating motility complex

Question 4

• Primary method of motility in small intestine
• Consists of ringlike contractions along length of small intestine
• Within seconds, contracted segments relax and previously relaxed areas contract
• Action mixes chyme throughout small intestine lumen

Answer 4

Segmentation

Question 5

Explain segmentation

Answer 5

1. Initiated by pacemaker cells in small intestine which produce basic electrical rhythm (BER)
2. muscle responsiveness is influenced by distension of intestine, gastrin, and extrinsic nerve activity

Functions:
> Mixing chyme with digestive juices secreted into small
intestine lumen.
> Exposing all chyme to absorptive surfaces of small intestine
mucosa
> Migrating motility complex- Sweeps intestines clean
between meals

Question 6

True or false

Juice secreted by small intestine contains digestive enzymes

Answer 6

False

Question 7

where do enzymes ( synthesized by small intestine) act?

Answer 7

within the brush-border membrane of epithelial cells

Question 8

enzymes secreted by the small intestine

Answer 8

• Enterokinase
• Disaccharidases
• Aminopeptidases

Question 9

How does digestion occur in the small intestine?

Answer 9

• Pancreatic enzymes continue carbohydrate and protein
  digestion
• Brush-border enzymes complete digestion of carbohydrates
  and protein
• Fat is digested entirely within small intestine lumen by
  pancreatic lipase

Question 10

Most occurs in duodenum and jejunum

Answer 10

Absorption

Question 11

Adaptations that increase small intestine’s surface area

Answer 11

> Inner surface has permanent circular folds
Microscopic finger-like projections called villi
Brush border (microvilli) arise from luminal surface of epithelial
cells

Question 12

How often is the lining of the small intestine replaced?

Answer 12

about every three days

Question 13

Products of fat digestion undergo ___________ that enable them to be ________________

Answer 13

transformations

passively absorbed

Question 14

Primarily a drying and storage organ

Answer 14

Large intestine

Question 15

the large intestine consists of:

Answer 15

Colon
Cecum
Appendix
Rectum

Question 16

Contents received from the small intestine consists of:

Answer 16

indigestible food residues, unabsorbed biliary components, and remaining fluid

Question 17

Extracts more water and salt from contents

Feces = _____________________

Answer 17

Colon

what remains to be eliminated

Question 18

Longitudinal bands of muscle in the large intestine

Answer 18

Taeniae coli

Question 19

Pouches or sacs ( in large intestine)

Actively change location as a result of contraction of circular smooth muscle layer

Answer 19

Haustra

Question 20

• Main motility of the large intestine

- Initiated by autonomous rhythmicity of colonic smooth muscle cells

Answer 20

Haustral contractions

Question 21

Mass movements

Answer 21

Massive contractions which moves colonic contents into distal part of large intestine

Question 22

Gastrocolic reflex

Answer 22

• Mediated from stomach to colon by gastrin and by autonomic nerves
• Most evident after first meal of the day
• Often followed by urge to defecate

Question 23

Defecation reflex

Answer 23

• Initiated when stretch receptors in rectal wall are stimulated by
  distension
• Causes internal anal sphincter to relax and rectum and sigmoid
  colon to contract more vigorously
• If external anal sphincter (skeletal muscle under voluntary
  control) is also relaxed, defecation occurs