Gastrointestinal system 6 Flashcards
How many salivary glands are there
3 pairs
Sublingual
Submandibular
parotid
How much fluid do the salivary glands produce
1.5L per day
Basal secretion - 0.3 ml/min
Stimulated secretion - 1.5 ml/min
What is saliva made up of
Mucus
Dilute solute NaHCO3/NaCl - optimal pH
Digestive enzymes
What are the two main digestive enzymes in saliva
Lingual lipase - Fats
alpha-amylase - Starch
What does saliva aid
Talking
Chewing and swallowing
Hygiene
(Dissolves food and lubricates)
What is xerostomia
‘Dry mouth’ - due to lack of saliva
Can lead to tooth decay
How do nerves regulate salivary secretion
Though, smell and sight of food
Presence of food in mouth
How does the autonomic nervous system regulate salivary secretion
Parasympathetic - stimulates secretion (copious quantities)
Sympathetic - Small volumes of viscous fluid
What volume of gastric secretion produced per day
2-3 L per day
Superimposed on basal rate when eating
Slow between meals
What makes up daily gastric secretion
Mucous (mucous cells)
HCL acid - 150 mls per hour (parietal cells)
Intrinsic factor (parietal cells)
Pepsinogen (chief cells)
What is he function of gastric mucous
Protection from abrasions and acid
What is the function of intrinsic factor
Absorption of Vitamin B in SI
What is the function of pepsinogen
Gastric proteolytic enzyme
Converted to active form (pepsin) by acid and starts digestions of proteins
What is the function of gastric acid
Dilutes fluid Denatures proteins Activates pepsinogen Optimum pH for pepsin Protection (bacteria)
What are the thee phases of gastric secretion
Cephalic - head controls
Gastric - stomach controls
Intestinal - intestine controls
Describe the cephalic phase
Preparation for arrival of food - stimuli
Chewing action
Parasympathetic NS - via enteric stimulates parietal, chief and goblet cells - stimulates secretion of gastrin into blood
What does gastrin do
Stimulates parietal and chief cells
Describe the stimuli of the gastric phase
Sufficient secretion to handle ingested food
Stimuli in stomach stretch/distend - elevated pH
Describe hormonal and nervous regulation in the gastric phase
Local nervous reflex - ENS
External nervous system - parasympathetic
Stimulate secretion - gastrin - and motility
Describe the stimuli of the intestinal phase
Controls delivery to small intestine - stimuli - distention of duodenum - arrival of acid chyme, lipids and carbohydrates
Describe the nervous and hormonal regulation of the intestinal phase
Hormones - GIP, CCK, secretin
Nerves - Enterogastric reflex
Both inhibit secretion and motility
What volume of secretion does the pancreas produce per day
1 - 1.5 L per day
What are the two components of pancreatic secretion
Enzymes (acinar cells) - chemical digestion Alkaline fluid (duct cells) - bicarbonate - neutralise acid to optimal pH for enzymes
What are the four most important pancreatic digestive enzymes
Lipolytic - Pospho/Lipase
Amylytic - amylase
Proteolytic - Trypsin, chymotripsinm carboxypeptidase
Necleolytic - Ribonuclease, deoxyribonuclease
How is pancreatic secretion stimulated
Hormone cholecystokinin (CCK) - stimulated by the arrival of lipids and carbohydrates in duodenum
What’s the difference in secreted enzymes and when they’re in the duodenum
Enzymes secreted in inactive precursors and are activated in duodenum
What converts trypsin to active state
Enterokinase bound to duodenum wall converts trypsinogen to trypsin
What does trypsin do
Converts other enzymes to active form
Describe the production of alkaline (HCO3 rich) fluid
Produced in pancreatic duct cells
Stimulated by hormone secretion - stimulated by arrival of acid chyme in duodenum
What does alkaline fluid do
Neutralises acid chyme from stomach
Optimal pH for pancreatic and intestinal digestive enzymes (6.7-9.0)
What volume of secretion do the biliary organs secrete
0.5 L per day
What do the biliary secretions consist of
Bile salts, HCO3- rich fluid (digestion)
Bile pigments - waste products - and cholesterol (excretory products)
What is the function of bile salts
Fat digestion
What is the function of HCO3- rich fluid
Neutralizes acid
What is the function of bile pigments
Excretion
Describe hormonal control over bile delivery
CCK (cholecystokinin) - produced in response to products of digestion in duodenum
Contracts gallbladder and relaxes hepatopancreatic ampulla
What stimulates bile secretion
Hormones mild stimulus of bile in liver
Bile is its own secretion - enterohepatic circulation
What is enterohepatic circulation
Bile is transported back to the liver and reabsorbed and secreted
Why is enterohepatic circulation important
Bile is expensive to produce - 95% reabsorbed in ileum
What volume does the small intestine secrete
1.5 L per day
What composes SI secretions
Mucus Isosmotic fluid (bicarbonate) Digestive enzymes (shed cells - reabsorbed)
What does the LI secrete
Mucus
