Session 3 - Anatomy Of The Gastrointestinal System

Question 1

What are the four layers of the gut wall?

Answer 1

Mucosa (innermost)
Submucosa
External muscle layers
Serosa (outermost)

Question 2

What layers make up the mucosa of the gut wall?

Answer 2

Epithelial layer
Lamina propria
Muscularis mucosae

Question 3

What does the lamina propria contain?

Answer 3

Lots of lymphoid nodules and macrophages. Produce antibodies to protect against bacterial/viral invasion.

Question 4

What does the submucosa of the gut wall contain?

Answer 4

Dense connective tissue, blood vessels, glands, lymphoid tissue, submucosal plexus (Meissner’s)

Question 5

What is a enterocyte?

Answer 5

A simple columnar cell that absorbs. Predominant cell of small and large intestines. Has microvilli.

Question 6

What do goblet cells secrete?

Answer 6

Mucus

Question 7

Is there a greater number of goblet cells in the duodenum or colon?

Answer 7

Colon. Increasing number as you move from the duodenum to the colon.

Question 8

What does mucus protect epithelium from?

Answer 8

Friction (mucus acts as a lubricant)
Chemical damage (acidic environment)
Bacterial inflammation (forms physical barrier)

Question 9

What do gastric surface mucous cells (foveolar cells) secrete?

Answer 9

Mucus/HCO3 that forms barrier to stomach acid

Question 10

What is the difference between plicae circulares and rugae?

Answer 10

Plicae circulares are permanent folds found in the small intestine. Rugae are temporary folds found in the stomach (allow stomach to expand easily).

Question 11

What specialised cells are found in the crypts of lieberkuhn and what are their functions?

Answer 11

Stem cells -constantly divide to replace epithelia
Paneth cells - secrete antibacterial proteins to protect stem cells
Enteroendocrine cells - secrete hormones that control the function of the gut

Question 12

Where are crypts of lieberkuhn found?

Answer 12

Small and large intestine

Question 13

Where are Brunners glands found?

Answer 13

Duodenum

Question 14

Give examples of exocrine tissues in the gut.

Answer 14

Salivary glands
Pancreas
Brunners glands

Question 15

What causes ulceration of the GI tract?

Answer 15

Erosion through the muscularis mucosae due to failure of protective mechanisms. E.g. loss of mucus production

Question 16

What is coeliac disease?

Answer 16

An abnormal immune response to gliadin (protein found in gluten). Mucosa of intestine becomes inflamed and damaged, villi can’t absorb. Results in malabsorption and diarrhoea.

Question 17

The term inflammatory bowel disease is mainly used to describe what two conditions?

Answer 17

Ulcerative colitis

Crohn’s disease

Question 18

What are the layers of the abdominal wall?

Answer 18

Skin
Fascia (+ fat)
 - superficial 
 - deep
4 muscles (3 anterolateral muscles)
 - external oblique
 - internal oblique
 - transverse abdominis
 - rectus abdominis
Transversalis fascia
Peritoneum

Question 19

Which abdominal muscles have an aponeurosis?

Answer 19

External oblique
Internal oblique
Transverse abdominins

These lateral muscles have aponeuroses that envelope the midline rectus abdominus muscles.

Question 20

What is the rectus sheath?

Answer 20

The aponeurosis of the lateral abdominal muscles surrounding the rectus abdominins

Question 21

What is the arcuate line?

Answer 21

Horizontal line that marks the lower limit of the posterior layer of the rectus sheath. It is also where the inferior epigastric vessels perforate the rectus abdominis.
Found roughly half way between the umbilicus and pubic crest.

Question 22

What is a mesentery?

Answer 22

A double fold of peritoneum that attaches certain viscera to the posterior abdominal wall.

Question 23

Which viscera are attached to the posterior abdominal wall by mesenteries?

Answer 23

Jejunum
Ileum
Appendix
Transverse colon
Sigmoid colon
Rectum

Question 24

What do mesenteries contain?

Answer 24

Blood vessels
Lymph vessels
Nerves
Fat

Question 25

What is a peritoneal ligament? Give examples.

Answer 25

A double fold of peritoneum that connects two viscera together. E.g. Gastrocolic ligament - stomach to transverse colon Gastrosplenic ligament - stomach to spleen OR A double fold of peritoneum that connects a viscera to the abdominal wall. E.g. Falciform ligament - liver to anterior abdominal wall Triangular ligaments - liver to diaphragm

Question 26

What is the falciform ligament?

Answer 26

Double fold of peritoneum connecting the liver to the anterior abdominal wall.

Question 27

What are the greater and lesser omenta?

Answer 27

Double folds of peritoneum: Greater omentum - hangs down off the greater curve of the stomach Lesser omentum - connects lesser curve of the stomach to the liver

Question 28

What is the purpose of sphincters in the GI tract?

Answer 28

Divide gut into sections Control movement along the gut Prevent reflux of material

Question 29

Name all the sphincters of the GI tract in order.

Answer 29

``` Upper oesophageal Lower oesophageal Pyloric Sphincter of Oddi Ileo-caecal valve Internal anal External anal ```

Question 30

Is the external anal sphincter under somatic or autonomic control?

Answer 30

Somatic (voluntary)

Question 31

Which branches of the aorta supply the foregut, midgut and hindgut respectively?

Answer 31

Coeliac trunk - supplies foregut Superior mesenteric artery - supplies midgut Inferior mesenteric artery - supplies hindgut

Question 32

Which viscera make up the foregut?

Answer 32

``` Lower oesophagus Stomach Spleen Liver Gallbladder Pancreas Proximal duodenum ```

Question 33

Which viscera make up the midgut?

Answer 33

``` Distal duodenum Jejunum Ileum Appendix Ascending colon Caecum Proximal 2/3 of transverse colon ```

Question 34

Which viscera make up the hindgut?

Answer 34

``` Distal 1/3 of the transverse colon Descending colon Sigmoid colon Rectum Upper anal canal ```

Question 35

All venous drainage from the intestines and stomach will drain to what organ via what vein?

Answer 35

Liver via the hepatic portal vein

Question 36

What is pyloric stenosis?

Answer 36

Hypertrophy of the pyloric sphincter. Causes gastric obstruction which can lead to projectile vomiting.

Question 37

What is a volvulus?

Answer 37

A volvulus is when a loop of intestine twists around itself and the mesentery that supports it, resulting in a bowel obstruction. Symptoms include abdominal pain, abdominal bloating, vomiting, constipation, and bloody stool.

Question 38

Why is a section of bowel involved in a volovulus at risk of ischaemia?

Answer 38

Mesentery contains blood vessels supplying the viscera, twisting of the mesentery can cut off these blood vessels leading to ischaemia.

Question 39

Explain why liver cirrhosis leads to ascites.

Answer 39

Liver cirrhosis leads to narrowing of blood vessels in the liver, this increases hydrostatic pressure in the hepatic portal vein. Increased hydrostatic pressure means that more fluid moves out of blood vessels into the interstitium and peritoneal cavity. Also, reduced liver function means less albumin is produced so there is a lower oncotic pressure in blood so more fluid moves out of the blood.

Question 40

What is ascites?

Answer 40

The accumulation of fluid in the abdomen/peritoneal cavity. Most commonly caused by portal hypertension due to liver cirrhosis.