Digestion 2 Flashcards
Where do the short reflexes originate and how are they intergrated?
Originate in the Enteric nervous system and are integrated w/o CNS
Where do the long reflexes originate and how are they intergrated?
Originate in the Enteric nervous system and are integrated w/ CNS
Where do cephalic reflexes originate?
CNS
Name 3 places secretions can be released
Released into the blood
Released into the lumen
Secretion to neighbouring cells
What do serous acini secret?
amylase
lipase
What do mucous acini secrete?
mucous
What do ducts cells secrete?
Water and HCO3
What is secreted alongside mucous and why?
Bicarbonate to buffer gastric acid to prevent damage to epithelium
What stimulates secretion of HCl and intrinsic factors?
Acetylcholine
Gastrin
Histamine
What cells secrete HCl and what is HCls function?
Parietal cells
HCl activates pepsin and kills bacteria
What cells secret intrisic factors and what is IFs function?
Parietal cells
IF form complexes w/ Vitamin B-12 to permit absorption
What cells secrete Histamine and what is Histamines function?
Enterochromaffin like cell
Stimulates gastric acid secretion
What does Acetylcholine stimulate the release of in the stomach?
Hcl Intrinsic Factor Histamine Pepsin gastric lipase gastrin
What cells secrete Pepsin and what is Pepsins function?
Chief cells
Digests proteins
What cells secrete gastric lipase and what is Gastric lipases function?
Chief cells
Digests fats
What cells secrete Somatostatin and what is Somatostatins function?
D cells
Inhibits gastric secretion
What cells secrete Gastrin and what is Gastrins function?
G cells
Stimulates gastric acid secretion
What controls the long reflexes?
What makes up the ENS ‘little brain’
Autonomic control
Sensory receptors and neurons- inter-neurons- enteric neurons
Describe bicarb secretion
Cells often have high con of what?
What enters and leaves the cell?
High con of carbonic anhydrase.
Cl- enter cells by AT and leave through CFTR channel, it reenters in exchange for HCO3-
Na+ and H2O leave the cell as well
G cells/ Gastrin
What is the stimulate for release?
What is the primary target and effect?
Stimulus= peptides, aa, neural reflexes
target= ECL cells, parietal cells to stimulate gastric acid secretion and mucosal growth
Cholecystokinin / CCK
What is the stimulate for release?
What is the primary target and effect?
Stimulus- FA, some aa
target- gallbladder, pancreas, stomach
Effect- stimulates HCO3- secretion
Inhibits gastric emptying and acid secretion
Motilin
What is the stimulate for release?
What is the primary target and effect?
Stimulus- Fasting released every 1.5-2 hours
Target- gastric and intestinal smooth muscle.
Gastric inhibitory Peptide / GIP
What is the stimulate for release?
What is the primary target and effect?
Stimulus- glucose, FA, aa in small intestine
Targte- Beta cells of pancreas
Effect- stimulate insulin release, in hibtis gastic emptying and acid secretion
Glucagon-like peptide-1 / GLP-1
What is the stimulate for release?
What is the primary target and effect?
Stimulus- mixed meal in the lumen
Target- endocrine pancreas
Effect- insulin release
inhibits glucagon release and gastric function
What 2 things promote satiety?
GLP-1
CCK
What is amylase broken down into?
Maltose
Describe the enzyme and product for the breakdown of Maltose
Maltase breaks maltose into 2 glucose molecules
Describe the enzyme and product for the breakdown of sucrose
Sucrase breaks sucrose into 1 glucose and one fructose
Describe the enzyme and product for the breakdown of lactose
Lactase breaks lactose into one glucose and one galactose
What do carbs require to cross from the lumen into the blood?
Transporters
Glucose/galactose enter the intestinal mucosa w/ Na+ via SGLT and exits on GLUT2
Fructose enters on GLUT5 and exits on GLUT2
Name the 2 types of peptidases
Endopeptidases
Exopeptidases
Name examples of endopeptidases
Pepsin
Trypsin
Which bonds to endopeptidases break?
Internal peptide bonds
What bonds do exopeptidases break?
Terminal peptide bonds to release amino acids
Match the peptide size to the mode of protein absorption.
Amino acid
Di-tripeptide
Small peptides
H+ cotransport
Endo/exocytosis
Na+ cotransport
Amino acid= Na+ co trasnport
Di-tripeptide= H+ co transport
Small peptides - endo/exocytosis
Describe how lipids are digested
Fat droplets are emulsified by bile salts to produce micelles
Micelles split into glyceol and FA to cross the lumen wall.
Cholestrol+TG+protein= chylomicron which moves to golgi then leaves via exocytosis
Describe iron absorption
Fe2+ comes from food and breakdown of heme ( already in the membrane)
Fe2+ enters via H+ co transport and enters via ferroportin
Describe calcium absorption
paracellualr is not regulated
Ca2+ moves into membrane vai Ca channel then exits w/ ATP of as 3Na+ goes in
Name the 3 ways NA enters the cell
Na channels
Cotrasnport w/Cl
Via proton pumps
