8.2

Question 1

What are the layers of the GI tract?

Answer 1

• Mucosa
• Submucosa
• Muscularis Externa
• Serosa/adventitia

Question 2

What are the three layers of GI mucosa? Describe each of them

Answer 2

• Mucous membrane (Protective epithelial tissue with endo/exocrine
• Lamina propria (connective tissue, contains GALT)
• Muscularis mucosa (thin layer of smooth muscle, can contract to expose different areas of folding)

Question 3

What is the submucosa? What network is in it?

Answer 3

• Connective tissue containing large blood/lymph vessels + a nerve network
• The nerve network is known as the submucosal plexus (nerve bodies of ENS)

Question 4

What is the muscularis externa? What plexus does it contain?

Answer 4

• Major smooth muscle coat; both circular and longitudinal
• Contains myenteric nerve plexus between inner circular and outer longitudinal

Question 5

What is the serosa/adventitia?

Answer 5

• Outer connective tissue, anchors organs to surrounding structures

Question 6

Serosa vs adventitia

Answer 6

Serosa: intraperitoneal
Adventitia: retroperitoneal

Question 7

What is digestion?

Answer 7

The breakdown of foodstuffs into a form that can be absorbed in the gastrointestinal tract

Question 8

What is absorption?

Answer 8

Movement of digested food into the bloodstream

Question 9

What is secretion (in terms of digestion)?

Answer 9

Release of water, enzymes, hormones, acids, buffers, salts etc. to aid in the function of the digestive system

Question 10

What is defecation?

Answer 10

Expulsion of feces from the digestive tract via the anus

Question 11

What are four factors that regulate digestive functions (i.e. large systems)

Answer 11

• Intrinsic nerves
• Extrinsic nerves
• Hormones
• Autonomous smooth muscle

Question 12

Describe how interstitial cells of cajal regulate digestive function

Answer 12

• Autonomous generation of slow wave potentials, which propagate to smooth muscle via gap junctions
• Depending on mechanical, neural, and hormonal factors, threshold may or may not be reached. If it is, contraction occurs

Question 13

What do enteric neurons release to cause relaxation of smooth muscle?

Answer 13

NO

Question 14

What are the two plexuses of the intrinsic enteric nervous system?

Answer 14

• Submucosal (within submucosa)
• Myenteric (between inner circular and outer long. of muscularis externa)