Gastrointestinal Tract I

Question 1

Name the four layers that make up the wall of the GI tract. What are their functions?

Answer 1

1. Mucosa:
 Lining epithelium
 Lamina propria
 Muscularis mucosae
 Functions are protection, absorption, and secretion.

2. Submucosa:
    Dense irregular CT with vessels
    Glands in esophagus and duodenum
    Submucosal (Meissner’s) plexus
3. Muscularis externa:
    Inner circular and outer longitudinal SM
    Myenteric (Auerbach’s) plexus
4. Serosa or adventitia:

Question 2

Recognize the esophagus in histological sections including knowing how its morphology changes along its length.

Answer 2

Esophagus has adventitia above diaphragm and serosa below

Upper esophageal sphincter of circular skeletal muscle under voluntary and reflexive control

Lower esophageal sphincter is a physiological sphincter of thickened circular smooth muscle

Question 3

Determine the region of the stomach in sections and identify and know the function of surface mucous cells, parietal cells, and chief cells.

Answer 3

surface mucous cells: Secrete an alkaline, viscous mucus with a high bicarcobonate content that protects the stomach’s surface

parietal cells: Secrete HCl and intrinsic factor. Acetylcholine, gastrin, and histamine receptors stimulate acid secretion. Zantac and Tagamet are histamine H2 receptor antagonists that suppress both HCl and intrinsic factor secretion (long term use can cause vitamin B12 deficiency and pernicious anemia).

chief cells: Synthesize and secrete pepsinogens
and lipases.

Question 4

What four types of papillae are found on the tongue?

Answer 4

1. filiform
2. foliate
3. fungiform
4. circumvallate

Question 5

Esophageal glands proper are found in which layer of the esophagus?

Answer 5

Submucosa

Question 6

Distinguish between the three major types of gastric glands.

Answer 6

The cardiac gastric glands are located at the very beginning of the stomach; the intermediate, or true, gastric glands in the central stomach areas; and the pyloric glands in the terminal stomach portion.

Both the cardiac and pyloric glands secrete mucus, which coats the stomach and protects it from self-digestion by helping to dilute acids and enzymes.

Question 7

Describe the structure and function of enteroendocrine cells.

Answer 7

Produce gastrin, somatostatin, and ghrelin.