Lecture 20: The Basic Structure of the GI System

Question 1

what is the primary function of the GI system?

Answer 1

bring nutrients into internal environment so they can be used

Question 2

what functions is the GI system specialised for?

Answer 2

• motility
• secretion
• digestion
• absorption

Question 3

what is the overall structure of the GI system?

Answer 3

• long tube with outgrowths
• closed off at both ends (sphincters)
• lined by epithelium

Question 4

what are the major organs of the digestive tract?

Answer 4

• oral cavity
• pharynx
• esophagus
• stomach
• small intestine
• large intestine

Question 5

what are the accessory organs of the GI system?

Answer 5

• teeth
• tongue
• salivary glands
• gallbladder
• pancreas

Question 6

where is stratified squamous epithelium found? why?

Answer 6

• mouth/oral cavity
• esophagus
• anus

for protection against abrasion

Question 7

where is simple columnar epithelium found?

Answer 7

• stomach
• small intestine
• large intestine

Question 8

what is an example of unicellular glands? what are the features of it?

Answer 8

goblet cells
- columnar
- goblet shape
- has apical mucous granules
- has basal nucleus

Question 9

what are the multicellular glands?

Answer 9

simple
- gland with single duct (e.g. stomach and small intestine)

compound
- gland with 2 or more ducts (e.g. salivary glands)

Question 10

what are the 4 layers of the gut tube?

Answer 10

1. mucosa
2. submucosa
3. muscularis externa
4. adventitia

Question 11

what does the mucosa consist of?

Answer 11

• epithelium
• lamina propria (FCT with lymphatics and blood vessels)
• muscularis mucosae
• sometimes glands

Question 12

what does the submucosa consist of?

Answer 12

• glands
• blood vessels

Question 13

how is secretion regulated in the submucosa?

Answer 13

secretion is regulated by the submucosal nerve plexus (part of the ENS)

Question 14

what does the muscularis externa consist of?

Answer 14

Smooth muscle:
2 main layers
- inner circular
- outer longitudinal

Myenteric plexus:
- part of ENS
- found in between muscle layers
- regulates motility

Question 15

What is the adventitia?

Answer 15

• outermost layer of the gut tube
• made of FCT

Question 16

what happens to the layers when organs are in the peritoneal cavity?

Answer 16

there is an additional outer covering called the serosa (not one of the 4 layers)

Question 17

Answer 17

Question 18

what is the peritoneum? what are the layers of it?

Answer 18

a serous membrane

parietal layer - lines the body wall
visceral layer - lines the organs

there is a fluid filled space between this layer

Question 19

what is a mesentery?

Answer 19

double layer of visceral peritoneum that connects organ to body wall

Question 20

what is an omentum?

Answer 20

double layer of visceral peritoneum that connects an organ to another organ

Question 21

what are the omentas

Answer 21

lesser omentum
- connects liver to stomach

greater omentum
- connects stomach to transverse colon

Question 22

what are the features of the mouth and oral cavity?

Answer 22

it is where food is ingested and digestion begins

• needs stratified squamous epithelium for protection
• needs enzymes for digestion
• food travels through fauces, into oropharynx then into esophagus

Question 23

what are the salivary glands and their secretions?

Answer 23

3 pairs connected to oral cavity via ducts

• parotid (secretes serous fluid with amylase)
• sublingual (secretes mucus only)
• submandibular (mixed)

Question 24

what is the structure of salivary glands?

Answer 24

• compound salivary glands
• have acinar cells that secrete enzymes (amylase)
• have duct cells that secrete bicarbonate (buffering)

Question 25

what is the esophagus? where is it? how is the epiglottis involved?

Answer 25

• a long tube located posterior from the trachea and extends from pharynx to the stomach
• the epiglottis ensures food enters the esophagus and not the trachea

Question 26

what is the structure of the esophagus?

Answer 26

• higher folded submucosa and mucosa (stratified squamous) with the capacity to expand
• the muscularis externa moves bolus by peristalsis
• the first third is skeletal muscle, the second third is a mixture, and last third is smooth muscle

Question 27

how does mucous work in the esophagus?

Answer 27

the esophagus needs mucus for lubrication and protection, but it doesn’t have goblet cells

• instead it has mucous secreting glands in the submucosa with ducts to the surface

Question 27

how does mucous work in the esophagus?

Answer 27

the esophagus needs mucus for lubrication and protection, but it doesn’t have goblet cells

• instead it has mucous secreting glands in the submucosa with ducts to the surface