The Digestive System (II) - The Alimentary Canal (Esophagus through Large Intestine)

Question 1

What are the four basic layers of the gut wall? What major regions define each layer?

Answer 1

• Serosa/adventitia (outermost)
• Muscularis externa (two or three layers of smooth muscle)
• Submucosa (above muscularis mucosa)
• Mucosa (innermost - epithelium and lamina propria and muscularis mucosa)

Question 2

What three layers make up the mucosa?

Answer 2

epithelium, lamina propria, muscularis mucosae

Question 3

What two layers make up the muscularis externa?

Answer 3

inner circular layer and outer longitudinal layer

Question 4

What two layers make up the serosa?

Answer 4

areolar tissue and mesothelium

Question 5

List the order of the layers of the alimentary canal.

Answer 5

Mucosa - Epithelium
Mucosa - Lamina Propria
Mucosa - Muscularis Mucosae
Submucosa
Muscularis externa - Inner Circular Layer
Muscularis externa - Outer Longitudinal Layer
Adventitia
Serosa - Areolar Tissue
Serosa - Mesothelium

Question 6

What is the primary function and composition of the mesentaries?

Answer 6

these translucent serous membranes loosely bind organs to the abdominal wall preventing the small intestine from entanglement

in close association with the serosa and peritoneum (serous membrane lining the abdominal cavity)

Question 7

What two plexuses compose the enteric nervous system?

Answer 7

submucosal plexus and the myenteric plexus

Question 8

What is the submucosal plexus responsible for?

Answer 8

regulaton of mucosal tension and folding, and secretion of mucosal glands

Question 9

What is the myenteric plexus responsible for?

Answer 9

regulation of peristalsis and of the submucosal plexus

Question 10

What is the name and function of the two sphincters of the esophagus? What is the name of the opening into the stomach?

Answer 10

Upper Esophageal Sphincter - keeps air out of the digestive tract by holding the upper end closed when there is no active swallowing

Lower Esophageal Sphincter - constriction that keeps the churning stomach from pushing contents back upwards into the esophagus

*Cardiac Orifice - the opening where the esophagus empties into the stomach (named for its proximity to the heart on the other side of the diaphragm)

Question 11

What two glands are present in the walls of the esophagus?

Answer 11

submucosal glands

esophageal (cardiac or mucosal) glands

Question 12

What three gland types are present in the stomach?

Answer 12

Cardiac Glands, Pyloric Glands, Gastric Glands

Question 13

What cell types are present in the gastric glands of the stomach? (5)

Answer 13

• Stem Cells
• Mucous Neck Cells
• Parietal (Oxyntic) Cells – egg-like appearance
• Chief (Zymogenic) Cells – between parietal cells, not as distinct in borders
• Enteroendocrine Cells (>8 kinds)

Question 14

What are the various types of secretions the cells of the stomach are responsible for? (6 Secretions)

Answer 14

Hydrochloric Acid - Parietal Cells
Intrinsic Factor - Parietal Cells
Pepsinogen - Chief Cells
Gastric Lipase & Chymosin - Chief Cells
Hormones and Paracrines - Enteroendocrine Cells
Mucus - Mucous Neck Cells

Question 15

What is the purpose of Hydrochloric Acid?

Answer 15

• activates pepsin and lingual lipase
• breaks up connective tissue and plant fiber (collagen and cellulose)
• converting Fe 3+ to Fe 2+ (absorbable form)
• Nonspecific disease (antibacterial, antiparasitic) resistance

Question 16

What is a stomach ulcer?

Answer 16

A wound within the stomach where epithelial cells are corroded and the underlying tissue is damaged by stomach acid - can result in gastric bleeding

Question 17

Which of the following cells does not have a digestive function?

Parietal Cells
Oxyntic Cells
Chief Cells
Mucus Neck Cells

Answer 17

Mucus Neck Cells - secrete mucous only

Question 18

What are the divisions of the small intestine?

Answer 18

Starts at the pyloric sphincter
Duodenum, Jejunum, Ileum
Ends at ileocecal valve

Question 19

Where can you find the submucosal plexus?

Answer 19

within the submucosa, with connective tissue and blood vessels

Question 20

Where can you find the myenteric plexus?

Answer 20

Within the muscularis externa

Question 21

Which of the following cells do not have a digestive function?

Parietal Cells
Chief Cells
Mucus Neck Cells
Oxyntic Cells

Answer 21

Mucus Neck Cells - secrete mucous only

Question 22

What four things contribute to surface area of the inestines?

Answer 22

Length, Circular Folds, Villi and Microvilli (forming brush border)

Question 23

How much of the small intestine is portioned to each of the three segments?

Answer 23

Duodenum - first 25 cm
Jejunum - first 40% postduodenum
Ileum - last 60% postduodenum

Question 24

What is the name of the lower spaces between villi? What is a specific cell characteristic of this region?

Answer 24

Intestinal Crypts

Paneth Cells - secrete antibacterial lysozyme

Question 25

What are the elaborations of the microvilli and what are they made up of?

Answer 25

Glycocalyx - composed of carbohydrates

Question 26

What are some characteristics of the Duodenum?

Answer 26

circular folds are absent of small, duodenal glands called “Brunner’s” Glands lie directly beneath the villi

Question 27

What are some characteristics of the Jejunum?

Answer 27

lacking duodenal glands or Peyer patches - not lacking circular folds but rather having abundant folding

Question 28

What are some characteristics of the Ileum?

Answer 28

circular folds present, shorter villi, greater number of lymphocytes - having Peyer patches with ~10-200 lymphoid nodules each = GALT system on the anti-mesenteric side of the ileum

Question 29

Describe the differences between the cardiac, fundic, and pyloric stomach(s).