1 Purpose of the Gut

Question 1

Name the 3 major parts of the small intestine.

Answer 1

Duodenum, Jejunum, Ilium

(DJ Iona)

Question 2

What is the cecum?

Answer 2

First region of large intestine, just after end of small intestine

Question 3

Name the parts of the GI tract in order.

Answer 3

Mouth, Oesophagus, Stomach, Duodenum, Jejunum, Ileum, Cecum, Large intestine, Anus

Question 4

What are the functions of the mouth? (3)

Answer 4

1. Physical breakdown of food
2. Initial digestive enzymes released
3. Infection control

Question 5

What is the function of the oesophagus and the 2 sphincters within it?

Answer 5

Rapid transport- bolus- through thorax to stomach

Upper oesophageal sphincter: Prevent air entering GI tract

Lower oesophageal sphincter: Help prevent reflux into oesophagus

Question 6

How many muscle layers does the stomach have?

Answer 6

3

Question 7

What are the functions of the stomach?

Answer 7

• Storage
• Produce chyme
• Physical, chemical breakdown
• Infection control (HCL)
• Absorb Vitamin B12- secrete intrinsic factor
• Intrinsic factor released in stomach- binds to b12 Absorbed in Ileum

Question 8

Fill in the missing labels:

Answer 8

Question 9

What is chyme?

Answer 9

Fluid- passes out of stomach

Consists of gastric secretions and partially digested food

Question 10

What are the functions of the duodenum? (in relation to chyme)

Answer 10

Neutralisation/osmotic stabilisation of chyme (eg addition of bile)

Question 11

Which organs connect to the duodenum to deliver bile and digestive secretions into the gut tube?

Answer 11

Liver and pancreas

Question 12

What are the functions of the Jejunum/Ileum?

Answer 12

• Final digestion
• Nutrient absorption (J)
• Water absorption (I)
• Bile recirculation
• B12 absorption

Question 13

What are the functions of the large bowel?

Answer 13

Final water absorption (but small intestine still absorbs more water overall)

Temporary storage

Final electrolyte absorption

Question 14

How does the parasympathetic nervous system control the gut?

Answer 14

ON button (rest and digest)

Via:

• Vagus nerve (oesophagus- transverse colon)
• Pelvic splanchnic nerves (S2-4) (transverse colon- anal canal)

Long preganglionic fibres extend to viscera- post ganglionics= v short, in vicera wall

Question 15

What might parasympathetic postganglionc fibres release into the gastrointestinal system?

Answer 15

• Acetylcholine
• Gastrin releasing peptide
• Vaso-inhibitory peptide

Question 16

Where do parasympathetic fibres synapse and what do they innervate? with relation to GI tract

Answer 16

Synapse in walls of viscera

Innervate:

• Smooth muscle cells
• Secretory cells

Question 17

How does the sympathetic nervous system control the gut?

Answer 17

OFF button

Mainly: constrict blood vessels

Orginates on T5-L2 innervation

Pass through para vertebral sympathetic trunk

Connect to form splanchnic nerves

Splanchnic nerves –> synapse with prevertebral ganglia (Coeliac, renal, superior mesenteric etc) –> post ganglionic fibres extend to viscera–> myenteric and submucosal plexuses

Question 18

How does the enteric nervous system work?

Answer 18

Can operate independently of CNS but connects with ANS

Millions of neurones

Extends from Oesophagus–> Anus

Question 19

What are the 2 main plexuses in the Enteric nervous system and what do they control?

Answer 19

• Submucosal (Meissner’s)
  
  • Secretions
  • Blood flow
• Myenteric (Auerbach’s)
  
  • Motility
    
    • In between circular and longutudinal muscle

Question 20

How does the enteric nervous system communicate with the PNS and the SNS?

Answer 20

• PNS: vagus and pelvic nerves
• SNS: prevertebral ganglia

Question 21

What are the 4 layers of the gut wall?

Answer 21