Gastrointestinal Review

Question 1

What is unique about the GI tract?

Answer 1

It is the only organ system that is “outside” the body. (aka has two openings to the outer environment)

Question 2

Oral Cavity (mouth)?

Answer 2

Ingestion, mechanical processing with accessory organs (teeth and tongue), moistening, mixing with salivary secretions

Question 3

Pharynx?

Answer 3

Muscular propulsion of materials into the esophagus.

Question 4

Esophagus?

Answer 4

Transport of materials into the stomach

Question 5

Stomach?

Answer 5

Chemical breakdown of materials by acid and enzymes; mechanical processing through muscular contractions

Question 6

Small Intestine?

Answer 6

Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions.

Question 7

Large Intestine?

Answer 7

Dehydration and compaction of indigestible materials in preparation for elimination.

Question 8

Teeth?

Answer 8

Mechanical processing by mastication

Question 9

Tongue?

Answer 9

Assists with mechanical processing with teeth, sensory analysis.

Question 10

Salivary glands?

Answer 10

Secretion of lubricating fluid containing enzymes that break down carbohydrates

Question 11

Liver?

Answer 11

Secretion of bile (important for lipid digestion), storage of nutrients, many other vital organs.

Question 12

Gallbladder?

Answer 12

Storage and concentration of bile

Question 13

Pancreas?

Answer 13

Exocrine cells secrete buffers and and digestive enzymes; endocrine cells secrete hormones.

Question 14

What are the 4 major layers of the GI tract?

Answer 14

1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa

Question 15

Mucosa?

Answer 15

Inner lining (mucous membrane), epithelium moistened by glandular secretions.

Question 16

Which tissues does the mucosa contain?

Answer 16

• stratified squamous in oral cavity, pharynx, esophagus
• simple columnar with mucous cells in stomach, small intestine, large intestine
• lamina propria of areolar tissue (with blood vessels, sensory nerve endings, lymphatic vessels [fight infection])
• Muscularis mucosae (aka Plicae circulares)

Question 17

Submucosa?

Answer 17

Dense irregular connective tissue that binds the mucosa to the muscularis externa

Question 18

What does the submucosa contain?

Answer 18

Blood vessels, lymphatic vessels, nerve fibers, neurons

Question 19

Muscularis externa?

Answer 19

Smooth muscle

Question 20

Serosa?

Answer 20

Serous membrane

Question 21

What is the histology of the oral cavity?

Answer 21

stratified squamous epithelium

Question 22

What is the histology of the large intestine?

Answer 22

simple columnar epithelium with mucous cells

Question 23

What is the histology of the esophagus?

Answer 23

stratified squamous epithelium

Question 24

What is the histology of the pharynx?

Answer 24

stratified squamous epithelium

Question 25

What is the histology of the small intestine?

Answer 25

simple columnar epithelium with mucous cells

Question 26

What is the histology of the stomach?

Answer 26

simple columnar epithelium with mucous cells

Question 27

Plicae circulares?

Answer 27

transverse folds that increase the SA for absorption

Question 28

What does the muscularis externa consist of?

Answer 28

Inner circular layer of muscle and an outer longitudinal layer

Question 29

What does the muscularis externa assist with?

Answer 29

Assists in mechanical digestion

Question 30

What does the serosa consist of?

Answer 30

areolar covered with simple squamous

Question 31

Which layer does the serosa not cover?

Answer 31

No serosa covering the muscularis external of the oral cavity, pharynx, esophagus and rectum, but rather a dense network of collagen fibres attaches the tract to adjacent structures (this is called the adventitia)