Session 1: Setting the Scene

Question 1

4 layers of the GI tube

Answer 1

Mucosa Submucosa Muscularis externae Serosa

Question 2

3 parts of the mucosa

Answer 2

Epithelial layer Lamina propria Muscularis mucosae

Question 3

Broad functions of the epithelial layer of the mucosa.

Answer 3

Selective permeability barrier (osmosis) Facilitation transport and digestion of food Promotion of absorption Production of hormones Production of mucus

Question 4

Broad functions of the lamina propria +layout.

Answer 4

Immune system Lots of lymphoid nodules and macrophages for production of antibodies (IgA which is resistant to proteases) to protect against bacterial and viral invasion.

Question 5

Broad functions of the muscularis mucosae.

Answer 5

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

Question 6

Layout and broad functions of the submucosa.

Answer 6

Dense connective tissue Blood vessels Glands Lymphoid tissue Contains the Meissner’s plexus for the enteric nervous system.

Question 7

Layout and broad functions of the muscularis externae.

Answer 7

An inner circular muscle layer with the Auerbach’s plexus An outer longitudinal muscle layer. Motility.

Question 8

Epithelia of the gut (type)

Answer 8

Stratified squamous in oesophagus and distal anus (where you can touch) Simple columnar in the rest

Question 9

Predominant cell of the small intestine and colon.

Answer 9

The enterocyte.

Question 10

Broad functions and layout of enterocytes.

Answer 10

One cell layer thick. Needed to transport nutrients through the apical membrane and the basolateral membrane where the blood vessels and lymphatics lie juxtaposed below the enterocyte. Has microvilli to increase surface area.

Question 11

Functions of the goblet cells.

Answer 11

Secretion of mucus to protect the epithelia of the gut from friction (lubricant), protection from chemical damage (acidic environment) and protection from bacterial inflammation by forming a physical barrier.

Question 12

Components of the serosa.

Answer 12

Blood and lymph vessels and adipose tissue and continuous with the mesenteric.

Question 13

Where can goblet cells mainly be found in the gut (which parts)?

Answer 13

Duodenum to colon in increasing number.

Question 14

What are foveolar cells?

Answer 14

Gastric surface mucous cells which line the gastric mucosa/gastric pits which secrete mucus/HCO3 that forms barrier to stomach acid in order to avoid chemical damage and irritation/inflammation.

Question 15

What increases the surface area of the gut?

Answer 15

Permanent folds Villi Microvilli

Question 16

Why are permanent folds, villi and microvilli important?

Answer 16

Because a larger surface area favours absorption.

Question 17

Different types of permanent folds and where to find them.

Answer 17

Rugae in stomach Plica circulares in small intestine Haustra sacculations in large intestine

Question 18

Where can you find villi?

Answer 18

In small intestines but not in colon

Question 19

Where can you find crypts?

Answer 19

In small and large intestines Aka crypts of Lieberkuhn/intestinal glands.

Question 20

What specialised cells do the crypts contain?

Answer 20

Stem cells Paneth cells Enteroendocrine cells

Question 21

How quickly can stem cells replace epithelia in the gut?

Answer 21

Every 2-4 days

Question 22

Location and function of the paneth cells.

Answer 22

Located at the base of crypts (Where you can find stem cells as well) Secrete antibacterial proteins to protect stem cells of the same crypts. Histologically the secretory vesicles are bright red (protein).

Question 23

Location and function of the enteroendocrine cells.

Answer 23

Located deeper in crypts and gastric glands. Secrete hormones that control the function of the gut like gastrin (stomach acid), cholecystokinin (bile) and secretin (neutralising acid).

Question 24

Examples of exocrine glands in the gut.

Answer 24

Salivary glands Pancreas Brunners glands (found in the duodenum which neutralise acid)

Question 25

Layers of the abdominal wall

Answer 25

Skin Fascia and fat (superficial and deep) Anterolateral muscles which are: External oblique (hands in pocket fibre direction) Internal oblique (perpendicular fibre direction) Transverse abdominis (more or less horizontal direction) Rectus abdominis (vertical direction) Transversalis fascia Peritoneum

Question 26

Aponeurosis of the abdominal wall.

Answer 26

Thin sheet like tendon which is associated with external oblique, internal oblique and transverse abdominis.

Question 27

What is the rectus sheath?

Answer 27

The aponeurosis of the lateral muscles surrounding the rectus abdominis.

Question 28

When can you find the arcuate line?

Answer 28

At the lower limit of the posterior layer of the rectus sheath. Roughly half way between the umbilicus and the pubic crest.

Question 29

What is the peritoneal cavity lined with?

Answer 29

Mesothelium Flattened simple squamous epithelia with a basement membrane and dense irregular connective tissue.

Question 30

Functions of the mesothelium lining.

Answer 30

Production of lubricating fluid Enveloping certain viscera (got both a visceral peritoneum (intraperitoneal) and a parietal peritoneum (lining the cavity wall) Also a retroperitoneal viscera which are not enveloped and lie posterior to peritoneal cavity.

Question 31

How do the aponeuroses differ above and below the arcuate line?

Answer 31

Above the arcuate line the aponeurosis of the external oblique goes in front of the rectus abdominis. The aponeurosis of the internal oblique goes around the rectus abdominis. The aponeurosis of the transverse abdominis goes posterior to the rectus abdominis. However below the arcuate line all aponeuroses go anterior to rectus abdominis.

Question 32

Purpose of the lubricating fluid of the peritoneal cavity.

Answer 32

To create a frictionless environment.

Question 33

What is the mesentery?

Answer 33

A double fold of peritoneum of contiguous tissue that attaches certain viscera to the posterior abdominal wall. Fixes the viscera in place.

Question 34

Viscera attached to the mesentery.

Answer 34

Jejunum Ileum Appendix Transverse colon Sigmoid colon Rectum

Question 35

What does the mesentery contain?

Answer 35

Blood vessels Lymph vessels Nerves Fat

Question 36

Purpose of the mesentery.

Answer 36

Fix viscera to posterior abdominal wall. Supply intraperitoneal viscera with blood, lymph, nerves etc…

Question 37

Pain reception difference between the parietal peritoneum and the visceral peritoneum.

Answer 37

Parietal peritoneum has somatic nervous reception so it can feel pain much clearer than the visceral peritoneum. Localised and accurate pain will be expressed by parietal peritoneum, this is not possible with the visceral peritoneum (pain not originate where one might feel it).