Digestive System

Question 1

Name the layers of the Digestive canal.

Answer 1

Mucosa (and Muscularis mucosa), Submucosa, Muscularis externa and Serosa or Adventitia.

Question 2

What makes up the Mucosa?

Answer 2

Epithelium lines the Lumen. Then the lamina propria, a loose connective tissue covers that. This CT has glands, rich vascularization, lymph vessels and lymph nodes. The muscularis mucosae covers this with an inner circular and an outer longitudinal layer of smooth muscle.

Question 3

What makes up the Submucosa?

Answer 3

Surrounds the mucosa with dense irregular fibroelastic CT. It has no glands except in esophagus and duodenum. Houses blood and lymph vessels, plus Meissner’s submucosal plexus.

Question 4

Location and function of Meissner’s submucosal plexus?

Answer 4

Found in the Submucosa. Postganglionic parasympathetic nerve cell bodies that control motility and secretion. Part of the Enteric NS.

Question 5

What makes up the Muscularis externa?

Answer 5

Covers the Submucosa layer. Has an inner circular and an outer longitudinal smooth muscle layers. These perform peristaltic activity. Also holds the Auerbach’s myenteric plexus.

Question 6

Location and function of Auerbach’s myenteric plexus?

Answer 6

Found in between the two muscle layers of Muscularis externa. Regulates the activity of muscularis externa. Part of the Enteric NS.

Question 7

What makes up the Serosa/ Adventitia?

Answer 7

CT that covers the Muscularis externa. If the tube is intraperitoneal, its covered by serosa. If the tube is retroperitoneal, it is adventitia.

Question 8

What are the effects of the Parasympathetic control on Digestive sys?

Answer 8

Stimulates peristalsis, inhibits sphincter muscles and triggers secretion. “Works” with vagus and sacral outflow.

Question 9

What are the effects of the Sympathetic control on Digestive sys?

Answer 9

Inhibits peristalsis and activated sphincters. “Works” with splanchnic nerves.

Question 10

Describe the layers of the Esophagus.

Answer 10

Epithelium - Thick stratified squamous nonkertinized epithelium
Lamina propria - esophageal cardias glands which produce a mucoid secretion.
Muscularis mucosa - single layer of longitudinally oriented smooth muscle
Submucosa - dense CT, has esophageal glands proper (tubuloacinar glands) that produce a mucous secretion. Also Meissner’s submucosal plexus.
Muscularis externa - outer layer top 1/3 is skeletal muscle, middle 1/3 is skeletal and smooth and the bottom 1/3 is smooth muscle. Also has Auerbach’s plexus.
Adventitia before diaphragm, serosa after.

Question 11

Describe the Mucosal lining of the stomach.

Answer 11

Lining is simple columnar epithelium with tubular gastric glands. Glands open into the mucosa through “gastric pits.” The lamina propria has A LOT of gastric glands, called Fundic glands. The muscularis mucosa has the normal layering of muscles, plus an extra outermost circular layer (not always seen).

Question 12

What are Fundic glands?

Answer 12

Gastric glands that extend from the muscularis mucosae to the base of the gastric pit. 6 cells types: surface lining cells, parietal (oxyntic), regenerative (stem) cells, mucous neck cells, chief (zygomatic) cells and diffuse neuroendocrine system (DNES) cells.

Question 13

Location and function of Mucus neck cells.

Answer 13

Stomach, gastric glands - lamina propria fundus. Secrete mucus and HCO3 mixed with chyme and reducing friction, secrete lysosome bacteria into the pylorus. Have short microvilli.

Question 14

Location and function of Regenerative (stem) cells.

Answer 14

Stomach, gastric glands - lamina propria. Replace all specialized cells in the gastric pit (5-7 days.

Question 15

Location and function of Parietal cells.

Answer 15

Stomach, gastric glands - lamina propria. Manufacture HCl and gastric intrinsic factor (impt in absorption of vit B12) with get released into stomach lumen. Have microvilli. Eosinophilic. Redish bc acidic.

Question 16

Location and function of Chif (Zygomatic) cells.

Answer 16

Stomach, gastric glands - lamina propria. Produce and secrete enzymes - renin, pepsinogen and lipase. HCl turns pepsinogen into pepsin. Purpleish bc they secrete enzymes.

Question 17

Location and function of DNES cells.

Answer 17

Stomach, gastric glands - lamina propria, small intestine. Produce endocrine, paracrine and neurocrine hormones. Cells can be open or closed.

Question 18

Location and function of A cells.

Answer 18

Stomach/ small intestine. Part of the DNES cells. Secretes glucagon, which stimulates glycogenolysis.

Question 19

Location and function of D cells.

Answer 19

Stomach/ Small intestine. Part of the DNES cells. Secretes somatostatin which inhibits hormone release from other DNES cells.

Question 20

Location and function of ECL cells.

Answer 20

Stomach/ Small intestine. Part of the DNES cells. Secret histamine which stimulates HCl secretion.

Question 21

Location and function of G cells.

Answer 21

Stomach/ Small intestine. Part of the DNES cells. Secretes gastrin, which stimulates HCl secretion, and gastric motility.

Question 22

What are the modifications that increase the luminal surface area of the small intestine?

Answer 22

Plicae circularesm, villi and microvilli.

Question 23

Location and structure of Crypts of Lieberkuhn.

Answer 23

Small and large intestines. Composed of DNES, surface absorptive, goblet, regenerative and Paneth (not in LI) cells .

Question 24

What are the regional differences between the D, J and I?

Answer 24

D - Brunner’s glands
I - lymphoid nodules, Peyer’s patches
J - neither Brunner’s or Peyer’s

Question 25

What are the cells of the Duodenum?

Answer 25

Surface absorptive cells (tall columnar, final destination for digestion & absorption of water and nutrients), Goblet cells, DNES, M Cell (transport antigens from intestine lumen to basolateral side, working with phagocytes), Regenerative cells, and Paneth cells, Brunner's gland.

Question 26

Location and function of Brunner's glands.

Answer 26

Duodenum - Submucosa. Provides alkaline mucus to neutralize the acid from the stomach.

Question 27

Location and function of Lacteals.

Answer 27

Small intestine - inside the villi. Lymphatic channels that provide passage for absorbed fat into lymphatic drainage.

Question 28

Location and function of Payer's patches.

Answer 28

Small intestine - Ileum. Immune surveillance and generation of immune response within lamina propria (mucosa).

Question 29

What is unusual about the Muscularis externa and serosa of the large intestine?

Answer 29

They outer longitudinal layer is not continuous, but forms narrow "ribbons" called Taeniae coli. The Serosa has fat filled pouches called appendices epiploicae.

Question 30

Describe the Appendix.

Answer 30

Found in between the end of the ileum and the beginning of large intestine. Note that it has a lot of lymphatic tissue.

Question 31

Describe what makes up a Classic lobule.

Answer 31

A hexagon shape with a central vein inside.

Question 32

Describe what makes up a Portal area.

Answer 32

A triangular region where 3 classic lobules join together, has hepatic artery, portal vein and interlobular bile duct in between. The bile then goes to the bile duct. This is the EXOCRINE path.

Question 33

Describe what makes up a Hepatic acinus.

Answer 33

A diamond shape, with two opposing portal regions and opposite central veins. The functional aspect is that there is a movement of oxygenated blood from hepatic arteries.

Question 34

What are Hepatic sinusoids and the space of Disse?

Answer 34

Sinusoids are an area of blood flow, and the space between the hepatic cell and the sinusoid is the space of Disse.

Question 35

Location and function of Kupffer cells.

Answer 35

Located in the Hepatic sinusoids, are derived from monocytes. They adhere to endothelial cells and phagocytise foreign material.