W1: GI PHYSIOLOGY

Question 1

Describe the control mechanisms involved in the control of salivary secretion

Answer 1

parotid (CN IX - glossopharyngeal)
sublingual (CN VII - Facial)
submandibular (CN VII - Facial)

Question 2

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

Answer 2

PARA => ⇧secretion; motility

SYMP => inhibit via SPHLANCNIC NERVE (except salivation)

Question 3

Describe the arterial supply and venous drainage of the GI tract

Answer 3

CELIAC TRUNK=> stomach, s. int., panc. liver
SMA => s. int, caecum, ascending and transv colon
IMA => descending colon, sigmoid, rectum
(descending abdo artery)

stomach => GASTRIC VEIN
panc => SPLENIC VEIN
s. int, caecum, asc and transv colon. => SMV
descending colon, sigmoid, rectum => IMV
> HEPATIC PORTAL VEIN > HEPATIC VEIN > IVC

Question 4

Explain the concept of the portal venous system and its anastomosis with the systemic blood supply

Answer 4

Portocaval anastamoses allow blood to still reach the systemic circulation, bypassing liver, in the event of blockages

• lower esoph.
• umbillicus
• upper part of canal
• liver
• flexures
• hepatic and splenic

Question 5

Describe the anatomy of the gastrointestinal tract and assign general physiological functions to each of its components

Answer 5

esoph: non-keratinised squamous epithelium
stomach: simple columnar cells, gastric pits,

s. int: digestion and abs.
l int.: WATER ABS., bact. fermentation. faecal formation

Question 6

Describe the common features of alimentary canal wall structure

Answer 6

-LUMEN-
- MUCOSA -
• epithelium
• lamina propria: connective tissue containing glands, neurovascular structures
• musc. mucosae: think smooth muscle

• SUBMUCOSA - thick irregular
  supplies mucosa and muscularis externae
  • glands
• MUSC. EXTERNA -
  • circular muscle: constriction
  • longitudinal: shorten
• SEROSA (peritoneal) / ADVENTITIA (outside peritoneal) -
  attach to surrounding structures
  serosa: surrounds stomach, s and l int.
  adventitia: surrounds oesoph. and rectum

Question 7

What innervates the muscularis externa?

Answer 7

submucosal plexus + myentheric plexus = enteric nervous system; regulate motility (PERISTALSIS)