Epithelia and Layers Of The Gut

Question 1

What type of epithelia are in the Oesophagus and Anus?

What about in between?

Answer 1

Stratified squamous (Resist physical and chemical abrasion)

Everything else is simple columnar

Question 2

What do you call the permanent folds in epithelium of the small intestine

Answer 2

Plica Circulares or Valvulae Conniventes

Question 3

The stomach’s simple columnar cells are mainly surface mucus cells.

What do they make?

Answer 3

Mucin

Question 4

In the stomach, what do the surface mucus cells drop down to form?

What are the base of these connected to in the Lamina Propria

Answer 4

Gastric pits

Gastric glands

Question 5

What smaller, irregular cells do you find in the base of the gastric pits

Answer 5

Neck mucous cells (Smaller vacuole of mucin than surface mucus cells)

Question 6

Compare Villi and Crypt (these cells are found In small and large intestine)

Answer 6

Villi: Projection into gut
Crypt: Invagination into gut

Question 7

What cells are predominant in the small and large intestine?

What cells are scattered between?

Answer 7

Enterocytes

Goblet cells (Narrow base, larger apical size hence the name)

Question 8

How do Goblet cell number change from Duodenum to Colon

Answer 8

Increase in number

Question 9

What are 3 specialised cells contained in the Crypts

Answer 9

Stem cells
Paneth cells
Enteroendocrine cells

Question 10

How often do Stem cells in crypt divide to replace epithelia

Answer 10

Every 2-4 days

Question 11

Where are Paneth cells found?

What do they do? Why?

Answer 11

At base of crypt

Secret antibacterial proteins, to protect STEM cells

Question 12

Where are Bruner’s Glands found?

What do they do?

Answer 12

In the Proximal Duodenum, extending from Mucosa into Submucosa (through Muscularis Mucosa)

Make an alkaline mucoid material and put it into sides/bases of crypts (to neutralise chyme from stomach)

Question 13

Name the 4 layers of the gut from inside to outside

Answer 13

• Mucosa (Epithelium, Lamina Propria, Muscularis mucosa)
• Submucosa
• External Muscle layers (Inner circle, outer longitudinal mostly)
• Serosa

Question 14

The Epithelial layer of the Mucosa is a selectively permeable layer.

List 4 of its functions

Answer 14

• Facilitate transport and digestion of food
• Promote absorption
• Produce hormones
• Produce mucus

Question 15

Immediately deep to the epithelium is the Lamina Propria.

What does it have lots of?

What is produced here? Which one mainly?

Answer 15

Has lots of lymphoid nodules and macrophages

Antibodies, mainly IgA (Protease resistant)

Question 16

Deep to the LP is the Muscularis Mucosa.

What does it consist of?

What are 2 functions?

Answer 16

Layers of smooth muscle oriented in different directions

• Keeps epithelium in contact with gut contents
• Helps keep crypt contents dynamic

Question 17

List 5 contents of the Submucosa

Answer 17

• Dense CT
• Blood vessels
• Glands
• Lymphoid tissue
• Submucosal plexus (Meissner’s)

Question 18

The Muscularis Externa contains 2 layers of muscle.

Compare what happens when each layer contracts

In combination, what do these movements allow to happen?

Answer 18

Inner Circular- Reduced width/ diameter of gut lumen
Outer Longitudinal- Changes length of gut

In combination allows peristalsis to move gut contents

Question 19

What is found between the Inner Circular and Outer Longitudinal muscular layers

Answer 19

Myenteric/ Auerbach’s Plexus

Question 20

What does the Serosa of the gut contain (List 3 things)

What is it continuous with?

Answer 20

• Blood vessels
• Lymph vessels
• Adipose tissue

Continuous with the Mesentery of the GI tract