Gastrointestinal Anatomy: Basic Structure of GI Structure

Question 1

What are the 4 main functions of the GI system?

Answer 1

Motility (transport food and water through the body + waste management)

Absorption (bringing nutrients/water from lumen into the internal environment)

Secretion (synthesisse and reelase enzymes, mucus, and serous fluid into the lumen)

Digestion (break nutrients into smaller pieces)

Question 2

These are structures that close off ends and separate sections of tube.

Answer 2

Sphincters

Question 3

What is the type of epithelia found in the mouth/oral cavity and the esophagus? Why?

Answer 3

Stratified squamous epithelium, to protect from abrasion

Question 4

What is the type of epithelia found in the stomach, small intestine and large intestine? Why?

Answer 4

Simple columnar, because columnar epithelia is much better in secretion and absorption

• has a larger surface area to absorb and secrete material

Question 5

What is the type of epithelia found in the anus?

Answer 5

Stratified squamous epithelium (to protect from abrasion of the POOP)

Question 6

Unicellular glands usually contain lots of these cells.

Answer 6

Goblet cells

Question 7

These cells are columnar, they have apical mucus granules and a basal nucleus

Answer 7

Goblet cells

Question 8

What are the 2 types of glands?

Answer 8

Simple and compound

Question 9

What’s the difference between a simple gland and a compound gland?

Answer 9

A simple gland has a single duct (like the stomach and small intestine)

A compound gland has 2 or more ducts (like the salivary glands) - it also has an increased SA to perform more secretions

Question 10

What are the 4 layers of the gut tube?

Answer 10

Mucosa, submucosa, muscularis (externa/proper), adventitia

Question 11

This consists of the epithelium, basement membrane and a lamina propria. May contain glands, and has a layer of smooth muscle (muscularis mucosae) that moves mucus and produces tiny localised movements.

Answer 11

Mucosa

Question 12

This consists of predominantly FCT, glands and blood vessels. It can perform many secretions, of which is regulated by the submucosal nerve plexus.

Answer 12

Submucosa

Question 13

This layer consists of smooth muscle. It contains the myenteric plexus which is located between layers and regulates motility (transport of food and water and other things in the gut)

Answer 13

Muscularis

Question 14

What are the 2 layers of the muscularis?

Answer 14

Circular muscle layer (inner) and longitudinal muscle layer (outer)

Question 15

This is the outermost layer of the gut tube and consists of FCT; this provides support to organ and may also help it to anchor to neighbouring cells.

Answer 15

Adventitia

Question 16

Why are there two layers of smooth muscle with different orientations? (in the muscularis)

Answer 16

Because there are different motility patterns in the gut tube. Different orientations of muscle will result in different contractions of the gut tube.

Question 17

Digestion begins where?

Answer 17

In the mouth (oral cavity)

Question 18

What are the 3 salivary glands? What do they each secrete?

Answer 18

Parotid (serous fluid with amylase)

Sublingual glands (mucus only)

Submandibular glands (mixed serous and mucus)

Question 19

Which salivary glands are activated in anticipation for food?

Answer 19

Submandibular glands

Question 20

These are compound secretory glands that secrete serous fluid, mucus, and enzymes like amylase.

Answer 20

Salivary glands

Question 21

These cells in the salivary glands are responsible for secreting bicarbonate.

Answer 21

Duct cells

Question 22

These cells in the salivary glands can secrete serous fluid, enzymes and mucus.

Answer 22

Acinar cells

Question 23

This is the terminology for cells in clusters.

Answer 23

Acinus

Question 24

What is the function of duct cells?

Answer 24

To secrete bicarbonate for pH buffering in the gut. (especially when you eat acidic food)

Also serous and mucus secretions ultimately pass through the ducts.

Question 25

This is a long tube (~25cm) located posterior to the trachea that extends from the pharynx to the stomach.

Answer 25

Esophagus

Question 26

This ensures the food enters the esophagus and not the trachea.

Answer 26

Epiglottis

Question 27

What are the layers of the muscularis externa of the esophagus? Why is it laid out this way?

Answer 27

First 1/3: skeletal muscle (because swallowing and chewing is voluntary movement)

Middle 1/3: mixture of smooth and skeletal muscle

Last 1/3: smooth muscle (because involuntary movement)

Question 28

Why is the mucosa and submucosa in the esophagus highly folded?

Answer 28

To have the capacity to expand for passage of bolus and for the glands as well

Question 29

The esophagus has goblet cells, true or false?

Answer 29

False. Esophagus has glands with ducts to surface epithelium.

Question 30

Where is mucus made in the esophagus?

Answer 30

In the mucus secreting glands (in mucosa and submucosa), it gets to surface epithelium through the ducts

Question 31

What is responsible for regulating motility in the muscularis externa?

Answer 31

Myenteric plexus

Question 32

Secretion in the submucosa is regulated by the?

Answer 32

Submucosal nerve plexus