Lecture 1 - Intro to the Gut + Peritoneal Cavity

Question 1

Outline the components of the GI tract from mouth to anus

Answer 1

Mouth –> Oesophagus –> Stomach –> Duodenum –> Jejunum –> Ileum –> Caecum –> Ascending colon –> Transverse colon –> Descending colon –> Sigmoid colon –> Anus

Question 2

What are the broad functions of the mouth and oesophagus?

Answer 2

Mouth:
- Physical breakdown of food, initial release of digestive enzymes and infection control (via enzymes)

Oesophagus:

• Rapid transport of bolus to stomach through thorax via peristalsis
• Upper oesophageal sphincter prevents air entering GIT, LOS prevents reflux into oesophagus.

Question 3

What are the broad functions of the stomach and what product is produced once food enters here?

Answer 3

• Storage facility + further physical and chemical breakdown (via proteases & acidic environment)
• Chyme, a fluid consisting of gastric secretions (acidic) and partially digested food

Question 4

What are the broad functions of the duodenum, jejunum and ileum (SI)

Answer 4

Duodenum:

• Neutralisation of acidic chyme via HCO3- rich solutions
• Receive pancreatic secretions containing bile salts to emulsify fats

Jejunum:
- Majority of final digestion and nutrient absorption, large SA allows this due to lots of folds

Ileum:
- Bile, B12 + water/electrolyte reabsorption occurs in the terminal ileum.

Question 5

What are the broad functions of the large bowel + rectum/anus?

Answer 5

Large bowel:

• Final water absorption, but not as much as ileum
• Final electrolyte absorption

Rectum/anus:
- Defection

Question 6

What is the peritoneal cavity + what is it made from?

Answer 6

• Peritoneal cavity is the potential space between the parietal (covering abdominal wall) and visceral (enveloping internal organs) peritoneum.
• Layers of mesothelium (simple squamous epithelium)

Question 7

Define intra-peritoneal and retroperitoneal structures?

Answer 7

Intra-peritoneal = viscera that the peritoneum envelops e.g.: liver, stomach + SI

Retro-peritoneal = structures that sit outside or behind the peritoneum e.g.: pancreas + kidneys

Question 8

What are mesenteries and what do they allow for?

What is the double fold connecting the liver and the stomach called?

Answer 8

• Mesenteries are double folds of peritoneum, they allow for passage of blood vessels, lymphatics and other things from retropeitnoeal to intraperitoneal areas without breaching the peritoneum + hold structures e.g.: the small intestine within the PC in place.
• Intraperitoneal ligament

Question 9

What is within the peritoneal cavity?

Answer 9

• Basically empty, some fluid (peritoneal fluid) within there secreted by mesothelial cells lining peritoneum