Session 2

Question 1

1. What controls the gut (3)
2. Draw the basic structure of the ANS

Answer 1

1. • ANS
   • Enteric nervous system
   • Hormones & paracrine substances
2. Image

Question 2

Draw a diagram showing the para & sympathetic innervation to the GI tract

What are splanchic nerves?

Answer 2

Paired visceral nerves (nerves that contribute to the innervation of the internal organs), carrying fibers of the autonomic nervous system (visceral efferent fibers) as well as sensory fibers from the organs (visceral afferent fibers). All carry sympathetic fibers except for the pelvic splanchnic nerves, which carry parasympathetic fibers.

Question 3

1. Draw a diagram showing the parasympathetic innervation to the GI tract
2. Function
3. Where is the left and right vagus nerves located on the stomach and why

Answer 3

1. Image
2. SM contraction

Glandular secretions

3. Left vagus nerve is anterior
   Right vagus nerve is posterior
   The stomach rotates

Question 4

How does the paasympathetic nerve cause HCL to be released

Answer 4

Question 5

Enteric nervous system

1. Submucosal (Meissner’s) function?
2. Myenteric (Auerbach’s) function?

Answer 5

Question 6

1. Explain what happens to the hormones released by enteroendocrine cells.
2. What is neurocrine release? Example of a GI hormone. Function of the hormone.

Answer 6

1. Pass into the hepatic portal vein
2. Hormone released after action potential from neurone
   E.g. Gastrin releasing peptide (GRP)
   Increases release of Gastrin from G cells

Question 7

State how the gastrointestinal hormones are categorised, what cells/where they are produced & their function

Answer 7

Question 8

Causes of appendicitis?

Answer 8

The appendix continues to produce mucus however due to the obstruction results in an increase in intraluminal pressure.

Bacteria can thrive in this environment.

Question 9

How do patients present with appendicitis

Answer 9

N + V

Question 10

Two common types of movements are present in the gut, peristalsis which propels gut contents & segmentation which mixes gut contents LO

1. All muscle in the GI tract is smooth muscle except:
2. What muscles are present in motility? 3 types of motility?
3. Phasic contractions occur in the GI tract which can either be?
4. State where tonic contractions occur in the GI tract

Answer 10

1. • Pharynx

• Upper 1/3 of oesophagus
• External anal sphincter

2. Circular muscle & Longitudinal muscle:

Peristalsis, Segmentation, Mass movement

image

3. • Periodic (propulsion and mixing)

• Tonic (constant level of contraction)

4. – Upper stomach
   – Ileocaecal valve
   – Internal anal sphincter

Question 11

State some motility problems

Answer 11

Paralytic ileus - loss of GI contractility

Achalasia- failure of LOS to relax (dysphagia)

Hirschsprung’s disease - lack of myenteric and submucosal plexuses, functional obstruction

Question 12

State what is secreted in different parts of th GI tract & the volume?

Answer 12

Question 13

How is water absorped?

Answer 13

Passive – follows electrolytes/nutrients
– After meal (water uptake driven by nutrients coupled with Na+, sodium co-transporters

– In between meals (Na+ & CL- are absorbed (sodium/hydrogen & chloride/bicarbonate exchangers))

In colon
– Additional mechanism so that stool can be desiccated

Epithelial Na+ channel (ENaC- identical to distal tubule of kidney)

Question 14

How is the vitillene duct formed?

Answer 14

Craniocaudal folding

Question 15

Where does the primitive tube originate & end at?

Answer 15

stomatodeum (future mouth) rostrally

proctodeum (future anus) caudally

opening at the umbilicus

Question 16

1. What is the gut tube internal/external lining is derived from?

It is suspended in?

2. State derivatives of the foregut, midgut & hindgut

Answer 16

Internal: endoderm (future epithelial linings)

External: splanchnic mesoderm (Future musculature, visceral peritoneum)

It is suspended in intraembryonic coelom by a double layer of splanchnic mesoderm

Question 17

1. Those structures that develop close to the junction between foregut and midgut will have ? blood supply. E.g. state the blood supply for the examples.

Answer 17

Mixed

Duodenum
• Proximal to entry of bile duct
– gastroduodenal a & superior pancreaticoduodenal a (CT)
• Distal to entry of bile duct
– inferior pancreaticoduodenal a (SMA)

Pancreas
• Head
– superior pancreaticoduodenal a (CT)
AND
– inferior pancreaticoduodenal a (SMA)

Question 18

1. The mesoderm surrounding the gut splits into layers:
2. The space created by the split is the ? Which will form the? The primitive gut is therefore surrounded by the?
3. What layers cover the gut in omphalacele?
4. What layers cover gastroschisis

Answer 18

1. o Somatic Mesoderm
   -> Develops into the muscles and fasciae of the abdominal wall
   o Splanchnic Mesoderm
   -> Develops into the smooth muscles of the gut wall
2. Coelomic Cavity, pleural cavity and the peritoneal cavity, Coelomic Cavity
3. Amnion as it covers the umbilical cord and both layers of peritoneum
4. Only covered by Visceral peritoneum
   Not parietal peritoneum due to lack of formation of the abdominal wall

Question 19

1. What mesentary attaches to the foregut, midgut & hindgut?

Answer 19

1. Dorsal mesentary covers the foregut, midgut & hindgut

ventral mesentary covers forgut

Question 20

By the foregut having a ventral & dorsal mesentery what does that result in?

Answer 20

Foregut divides the cavity into left and right sacs

Left sac = Greater Peritoneal Sac

Right sac = Lesser Peritoneal Sac

Question 21

1. How does the stomach differ to the rest of the foregut
2. The stomach initially was symmetrical, why is it not symmetrical at the time of birth?
3. As a result of stomach rotation: (6)

Answer 21

1. widest part of the foregut
2. • It enlarges & it expands unevenly, mainly towards the left
     - The faster growth of the dorsal border creates the greater curvature. The primitive stomach also rotates in two directions, around the longitudinal axis and around the anteroposterior axis.
3. o The original Left side becomes Anterior
   o The original Right side becomes Posterior
   o Vagus nerves lie anterior and posterior instead of left and right
   o Shifts cardia and pylorus from the midline, pushing greater curve inferiorly
   o Moves the lesser sac behind the stomach
   o Creates the greater omentum

Question 22

Understand why some abdominal organs possess mesenteries and some are retroperitoneal LO

1. Peritoneal structures?
2. Retroperitoneal structure?
3. Secondarily Retroperitoneal?
4. The duodenum and its mesentery is pushed against the posterior abdominal wall during
   development due to?

2. The peritoneum of posterior abdominal wall is squished together with the duodenum and its mesentery, growing over it. This is ?

3. Since fusion fascia is ? you can remove it to ?

Answer 22

1. jejunum and ileum
2. S - suprarenal glands, A- aorta, D- duodenum 3/4, P - pancreas, U-ureters C- colon (ascending & descending), K- kidneys, E-eosophagus R - rectum
3. ascending and descending colon, duodenum, Rectum, pancreas
4. the rotation of the stomach and the large size of the liver

2. fusion fascia

3. avascular, make the duodenum mobile again without causing any damage

Question 23

Foregut

1. Extends from ?
2. What happens in the 4th week to the ventral wall of the foregut?

Answer 23

1. the lung bud to the liver bud
2. • 4th week
     - respiratory diverticulum forms in the ventral wall of the foregut at the junction with the
     pharyngeal gut.
     - respiratory primordium ventrally & the oesophagus dorsally, divided by the tracheoesophageal septum

Question 24

State what the foregut-derived glands are derived from

Answer 24

• Liver and biliary system -> Ventral mesentery
• Pancreas –> Components develop in both
• Uncinate process and inferior head = ventral
• Superior head, neck, body & tail = dorsal

Question 25

Answer 25

Question 26

Meaning of Secondarily retroperitoneal???

Answer 26

* A structure that developed intraperitoneally whose mesentery was lost to fusion with posterior abdominal wall parietal peritoneum due to massive expansion of GI tract during development * Fusion fascia

Question 27

What is this image showing?

Answer 27

Fusion fascia is the blue