Grand Tour of the Alimentary Canal

Question 1

Describe the control mechanisms involved in the control of salivary secretion.

Answer 1

Parasympathetic (inhibits saliva secretion, excites ?gastric secretion and motility);

• Facial (VII)
• Glossopharyngeal (IX)

Sympathetic stimulates.

Question 2

Describe the effects of the parasympathetic nervous system on secretion and motility.

Answer 2

Vagus nerve (X) –> stimulates secretion and motility.

Question 3

Describe the effects of the sympathetic nervous systems on secretion and motility.

Answer 3

Splanchnic nerve –> inhibits secretion and motility.

Question 4

Describe the common features of alimentary canal wall structure.

Answer 4

• Continuous hollow tube (varying diameter, ~8m long)
• Tube wall has same structural organisation throughout

Four distinctive layers (tunics);

• Mucosa (epithelium, lamina propria, muscularis mucosae) - Submucosa
• Muscularis externa
• Serosa/adventitia

Question 5

Describe the organisation of the enteric nervous system.

Answer 5

Submucosal + myenteric (sits between the two muscles layers) plexuses = ENS (independent control of gut function).

Question 6

Describe the serosa tunica.

Answer 6

• Connective tissue outer layer

- Peritoneum

Question 7

Describe the muscularis externa tunica and its function.

Answer 7

Two concentric thick layers of smooth muscle.
Inner layer: circular, constricts lumen
Outer layer: longitudinal, shortens tube
Both layers produce motility –> peristalsis, segmentation.
Myenteric (Auerbach’s) plexus found between inner and outer layers.

Question 8

What components of the alimentary system have stratified squamous epithelium?

Answer 8

Mouth, oesophagus and anal canal.

Question 9

What components of the alimentary system have simple columnar epithelium?

Answer 9

Stomach, small and large intestine.

Question 10

What are the functions of the epithelium of the GIT?

Answer 10

• Synthesis and secretion of digestive enzymes, hormones and mucus
• Absorption of the products of digestion.

Question 11

Describe the lamina propria (in the mucosa of the epithelium) in the GIT.

Answer 11

Loose connective tissue (glands, blood/lymph vessels).

Question 12

Describe the muscularis mucosae (in the mucosa of the epithelium) in the GIT.

Answer 12

Thin smooth muscle layer.

Question 13

Describe the submucosa (of the epithelium) in the GIT.

Answer 13

• Thick, irregular connective tissue
• Contains neurones, blood vessels (supplies mucosa, muscularis externa, serosa) lymph vessels
• Neurones form extensive network –> submucosal (Meissner’s) plexus (parasympathetic)
• Submucosal glands in oesophagus and duodenum

Question 14

Describe the difference between the serosa/adventitia inside the peritoneal cavity vs. outside.

Answer 14

Outside: adventitia attaches to oesophagus and rectum to surrounding structures.
Inside: serosa surrounds stomach, small and large intestine.

Question 15

What arterial branches arise from the descending (abdominal) aorta?

Answer 15

Celiac trunk, superior and inferior mesenteric artery.

Question 16

What organs does the celiac trunk supply?

Answer 16

Stomach, small intestine, pancreas and liver.

Question 17

What organs does the superior mesenteric artery supply?

Answer 17

Small intestine, caecum, ascending and transverse colon.

Question 18

What organs does the inferior mesenteric artery supply?

Answer 18

Descending and sigmoid colon, and rectum.

Question 19

Describe the venous drainage of the stomach.

Answer 19

Stomach –> gastric vein –> hepatic portal vein –> hepatic vein –> inferior vena cava

Question 20

Describe the venous drainage of the pancreas.

Answer 20

Stomach –> splenic vein –> hepatic portal vein –> hepatic vein –> inferior vena cava

Question 21

Describe the venous drainage of the small intestine, caecum, ascending and transverse colon.

Answer 21

Superior mesenteric vein –> hepatic portal vein –> hepatic vein –> inferior vena cava

Question 22

Describe the venous drainage of the descending and sigmoid colon, and rectum.

Answer 22

Inferior mesenteric vein –> hepatic portal vein –> hepatic vein –> inferior vena cava