Pancreas and Liver Physiology Flashcards
GI Physiology
What does a pancreatic islet contain?
Alpha cells
Beta cells and Exocrine acinus
What are the two endocrine functions of the pancreas?
Produces hormones e.g. insulin and glucagon
Hormones secreted directly into bloostream
What are the three exocrine functions of the pancreas?
Pancreatic juice
Site of action is the small intestine
Duct mediated secretion similar to salivary secretion
What is the microscopic structure of the pancreas similar to?
salivary glands - secretory
what do the pancreatic secretions move through, into what?
they move through intercalated ducts into one large duct - and then secretes into duodenum
in most species, where does the pancreatic duct secrete directly into?
directly into the duodenum
In goats and sheep, where does the pancreatic duct join the common bile duct?
joins BEFORE the entrance into the duodenum
what enters the duodenum from the pancreas?
A mixture of bile and pancreatic juice enters the duodenum
what does a lower concentration of HCO3- and Cl- determine about the secretion rate?
the lower the conc = the faster the secretion rate
what enzymes are found in the pancreatic juice?
lipase, amylase and proteases
what does lipase do?
it breaks down fat, glycerol and fatty acids
what does amylase do?
it breaks down starch, glucose and maltose
what do proteases do?
they break down peptides and amino acids
what form are all enzymes secreted in?
all secreted in their inactive form
what are inactive precursors?
the inactive forms of enzymes
what does trypsin do?
it activates all enzymes
what enzyme is an autocatalyst?
trypsin
what is autocatalysis?
the process where the reaction product is also the catalyst for the reaction
what does trypsin inhibitor do?
it can limit innapropriately activated trypsins
what is trypsin secreted as?
secreted as trypsinogen
where is trypsin formed and what forms it?
it is formed in the duodenum and it is formed by enteropeptidase
which cells secrete trypsin inhibitor?
gland cells
what is produced in large volumes?
pancreatic juice
describe the pH of pancreatic juice?
alkaline
why is pancreatic juice alkaline?
due to the HCO3- ions
Point of the pancreatic juice being alkaline?
it neutralises ingesta/chyme that is entering the duodenum from the stomach
Why is it good that the pancreatic juice is alkaline?
it prevents injury to mucosa
it provides the optimal pH for enzymatic activity
how many phases of juice secretion are there?
3 phrases
what are the three phases of pancreatic juice secretion?
cephalic phase
gastric phase
intestinal phase
what occurs during the cephalic phase of pancreatic juice secretion?
changes that occur before food enters the stomach - prehension, mastication and deglutition
what occurs during the gastric phase of pancreatic juice secretion?
changes in digestive tract motility initiated in the stomach - peristalsis and churning of food as a trigger
what does feeding result in for most species? what’s different for pigs and horses?
increases enzyme production in most species - increase in secretion of pancreatic juice HOWEVER pigs and horses there are also increases in water and ion secretion
what occurs during the intestinal phase of pancreatic juice secretion?
chyme entering the duodenum causes increases in pancreatic secretion - this is regulated by CCK and secretin
What feedback system is secretin involved in?
it is involved in the negative feedback system
when and where is secretin released from?
it is released from duodenum upon increased acidity
what is secretin?
it is a neuroendocrine peptide hormone
what does secretin have action on?
many organ systems
where is secretin secreted from?
secrteed by the S cells of the duodenum
what does the release of secretin stimulate?
stimulates HCO3- secretion - neutralisation function
when does secretin production reduce?
once acid in the duodenum decreases
what does CCK stand for?
Cholecystokinin
what is CCK?
it is a peptide hormone secreted by the duodenum
when is CCK released?
when FAs and peptides/amino acids increase in duodenum
what does CCK stimulate?
it stimulates the pancreas to increase enzyme secretior and increases bile secretion
what effect does CCK have on enzymes?
it results in increased enzymes = increased ingesta degradation
overall, CCK results in?
increased products of digestion
what feedback system is CCK involved in?
positive feedback system
rate of secretion of pancreatic juice comparison between ruminants, horses and cats&dogs?
ruminants - constant rate of secretion and chyme transport
horses - increase in rate of rate of secretion within a few minutes of feeding starting –> low levels of enzymes due to microbial degradation
Cats&Dogs - great increase in amount of juice produced after feeding
little production when small intestine is empty
How many roles of the liver are there?
9