The Digestive System

Question 1

4 main functions of the digestive system

Answer 1

1. Take in food
2. Break it down into nutrient molecules
3. Absorb nutrient molecules into the bloodstream
4. Rid the body of any indigestible remains

Question 2

Gastrointestinal (GI) tract is

Answer 2

A continuous muscular tube that digests & absorbs
Includes: the mouth, pharynx, esophagus,
stomach, small & large intestines

Question 3

Accessory digestive organs

Answer 3

facilitate mechanical breakdown of food & produce specialized secretions to aid digestion
Includes:
◦ Teeth, tongue, & salivary glands
◦ Gallbladder, liver, & pancreas,

Question 4

First 3 out of 6 activities of processing food are

Answer 4

1. Ingestion takes food into GI via the mouth
2. Secretion of digestive enzymes
3. Motility (movement of food)
   ◦ Propulsion & peristalsis
   ◦ Mechanical breakdown (high surface area and digestive enzyme secretion)

Question 5

Final 3 out of 6 activities for processing food are

Answer 5

4. Digestion: enzymes catabolize (break down) food to its chemical components enzymes
5. Absorption: movement of digested end products from lumen of GI tract into blood or lymph
6. Defecation – elimination of indigestible substances via anus

Question 6

The Visceral peritoneum

Answer 6

covers external surfaces of most of the digestive organs

Question 7

The Parietal peritoneum

Answer 7

lines body wall of abdominopelvic cavity

Question 8

The Peritoneal cavity

Answer 8

Is the space between visceral & parietal peritoneum filled with serous fluid

Question 9

Mesentery is

Answer 9

A double layer of peritoneum that extends to the digestive organs from the body wall
◦ Allows blood vessels, lymphatics, & nerves to reach digestive organs
◦ Holds the organs in place & stores fat

Question 10

The Two folds of visceral peritoneum that connect to the stomach are

Answer 10

1. The Greater omentum: hangs from the greater curve of the stomach in front of intestines
2. The Lesser omentum: hangs from the liver to the lesser curve of the stomach

Question 11

The mucosa of the GI tract is

Answer 11

• the innermost layer
• composed of simple or stratified epithelium
• provides secretions, absorbs digestive end products, & protects against infectious disease

Question 12

Submucosa of the GI tract is

Answer 12

• the 2nd innermost layer
• composed of connective tissue with blood & lymphatic vessels, & nerves

Question 13

Muscularis externa is

Answer 13

• the middle muscle layer
• Inner circular & outer longitudinal smooth muscle layers for peristalsis & segmentation

Question 14

Serosa/Adventitia of the GI tract are

Answer 14

• the outermost layers
• serosa is composed of visceral peritoneum
• adventitia is a dense network of collagen fibres attaching the GI tract to adjacent structures

Question 15

The “In-house” nerve supply for the GI tract is

Answer 15

The Enteric Nervous System (ENS)
- GI tract has its own separate nervous system

Question 16

Sensory receptors of the ENS are

Answer 16

• found within the mucosal epithelium
  ◦ Chemoreceptors – sense osmolarity, pH,
  substrates & end products of digestion
  ◦ Mechanoreceptors – sense stretch by
  food (trigger for digestive system)

Question 17

Submucosal plexus of the ENS

Answer 17

controls digestive secretions

Question 18

Myenteric plexus of the ENS

Answer 18

mostly controls motility (strength & rate of contraction)
- runs between laters of smooth muscle

Question 19

Reflex mediated entirely by enteric neurons

Answer 19

Short reflexes (intrinsic)

Question 20

Reflex that also involves CNS integration centres & extrinsic autonomic nerves (rate can be manipulated by the ANS)

Answer 20

Long reflexes (extrinsic)

Question 21

Parasympathetic NS activity results in

Answer 21

↑ ENS activity leading to↑motility & digestive canal secretion

Question 22

Sympathetic NS activity results in

Answer 22

↓ ENS activity leading to↓motility & digestive canal secretion

Question 23

Hormones of the GI tract are produced by

Answer 23

• enteroendocrine cells of stomach & small intestine - control secretion or contraction