Layers of the gut and the peritoneal cavity

Question 1

Why is the gut an external surface?

Answer 1

• It’s continuous with the skin
• Its contents are therefore external until they are absorbed across the epithelia.

Question 2

What are the 4 layers of the gut?

Answer 2

1. Mucosa (innermost)
2. Submucosa
3. External muscle layers
4. Serosa (outermost)

Question 3

What are the layers of the mucosa?

Answer 3

1. Epithelium (innermost)
2. Lamina propria
3. Muscularis mucosa (outermost)

Question 4

What is the function of the epithelial layer of the mucosa?

Answer 4

• Selectively permeable barrier
• Facilitate transport and digestion of food.
• Promotes absorption
• Produce hormones
• Produce mucus

Question 5

What is the function of the lamina propria layer of the mucosa of the gut?

Answer 5

• Contains lots of lymphoid nodules and macrophages.
• Produces lots of antibodies - mainly IgA which is protease-resistant.
• Protects against bacterial/viral invasion

Question 6

What is the function of the muscularis mucosa of the mucosa of the gut?

Answer 6

• Layers of smooth muscle orientated in different directions
• Keeps epithelium in contact with gut contents to improve absorption.
• Helps keep crypt contents dynamic

Question 7

What structures are found within the submucosa of the gut?

Answer 7

• Dense connective tissue
• Blood vessels
• Glands
• Lymphoid tissue
• Meissner’s plexus

Question 8

What are the layers that make up the external muscles of the gut?

Answer 8

• Inner circular muscle (contains Auerbach’s plexus)
• Outer longitudinal muscle

Question 9

What structures are found within the serosa of the gut?

Answer 9

• Blood and lymph vessels and adipose tissue
• Continuous with mesenteries

Question 10

Which structures pass through the diaphragm to enter the abdominal cavity?

Answer 10

• Oesophagus
• Vena cava
• Aorta

Question 11

What is the peritoneum made up of?

Answer 11

• Layers of mesothelium (simple squamous epithelia)
• It is serous

Question 12

Describe how the peritoneal cavity interfaces with the abdominal cavity

Answer 12

• Liver, stomach and small intestine are enveloped by the peritoneum.
• These are intraperitoneal viscera
• The peritoneal cavity overlies the anterior surfaces of the other organs.
• These are retroperitoneal organs

Question 13

What are mesenteries?

Answer 13

• Double folds of peritoneum that form channels through which blood vessels and lymphatics can pass.

Question 14

What is found within the peritoneal cavity?

Answer 14

• Only a small amount of fluid - it is otherwise empty.

Question 15

What is a ligament in the peritoneal cavity?

Answer 15

• A double fold of peritoneum connecting viscera