Pancreas and Liver Flashcards
What are glands?
Glands are specialised organs that secrete chemical substances.
what are the two main classifications of glands?
endocrine and exocrine
What do endocrine glands do?
these are glands that secrete chemical substances into the bloodstream or tissues of the body.
what do the endocrine glands in the pancreas do?
They secrete hormones into the bloodstream to regulate blood borne energy substrate availability (ie glucose, fatty acids, ketone bodies, aas). eg after a meal insulin will be released to stimulate muscle and liver cells to store glucose as glycogen.
What do exocrine glands do?
Glands that secrete chemical substances into ducts
What sort of secretions do the exocrine glands in the pancreas secrete?
digestive enzymes to digest CHO, protein and lipid and HCO3- to neutralise acidic material in duodenum
do the main pancreatic duct and bile duct come together before the sphincter of Oddi?
yes
Where is the pancreatic blood supply from?
Mainly via the splenic artery (from coeliac trunk), as well as pancreatic-duodenal arteries( from superior mesenteric artery)
Describe what the acinar cells are and their positioning
main secretory cels of the pancreas, secreting ions (na+, Cl-,HCO3- and enzymes). Positioned in clusters which are connected by ducts.
What occurs in the pancreas (exocrine glands) during the cephalic phase of digestion?
Vagus nerve stimulates pancreatic secretions by releasing Each and VIP
What controls the pancreatic exocrine output during the gastric phase of digestion?
vasovagal reflexes
What controls the exocrine pancreas secretions during the intestinal phase of digestion?
The hormone secretin (in response to H+) and CCK (in response to was, fatty acids, monoacylglycerols)
what do zymogen granules do?
They house inactive digestive enzymes which they then activate and secrete them (in response to CCK) by exocytosis from acinar cells into luminal space
how is the exocytosis of enzymes from zymogen granules regulated?
Both hormonally and neurally. First CCK is released into interstitial space, which then enters the bloodstream + travels to pancreatic acinar cells and binds with CCK receptors. Also, CCK binds to receptors on vagal afferents, giving afferent stimulation of pancreatic acinar cells via VIP.
Explain the ion secreting mechanism in the acinar cells
CCK and ACh bind to the basolateral membrane. this stimulates Cl- movement across the apical membrane. Once the Cl- move out, Na+ and water will also move into the lumen paracellularly (regulation of charges and water balance)
what is paracellular movement?
movement through the spaces between the cells
Explain the ion secreting mechanism in intercalated ductal cells
Secretin and Act bind to ductal cell membranes. this activates cyclic fibrosis transmembrane conductance regulators, Cl- channels, Cl-HCO3- co-transporters.
Transporters recycle CL- and HCO3-
How does the flow rate of the pancreatic exocrinal secretions alter the ionic concentration of the secretions
An increased flow rate cause the HCO3- conc to increase and the Cl- conc to decrease. BUT Na+ and K= concs are not affected by flow rate
what are the concs of Na+ and K+ in plasma compared to plasma?
Na+ similar to plasma, K+ slightly higher than plasma
what is the largest organ in the body?
liver
is the liver superior to the diaphragm?
no
What serous membrane covers the liver except for the bare area?
peritoneum
Describe the Glisson’s capsule
a thin connective tissue layer with extensions into the liver between the tubules
Which artery supplies the hepatocytes with oxygen?
hepatic artery
what is hepatocyte?
liver cell
what does the hepatic portal vein do?
bring absorbed nutrients from the gut to the liver
how is bile secreted?
though canaliculi that lie between hepatocytes which then connect to bile ductules and then bile ducts which finally form the common hepatic duct.
what carries oxygen-depleated blood away from the liver?
hepatic veins that enter the inferior vena cava
List the 5 functions of the liver
- Synthesis and secretion of bile
- storage of glucose, proteins , vitamins + fats
- Detoxification of metabolic waste (removal of ammonia, ethanol and drug biotransformations)
- synthesis of blood clotting factors + anticoagulant factors (fibrinogen and prothrombin)
- Immune system function- remove intestinal bacteria from portal blood so there is none in systemic circulation
what separates the left lobe from the right lobe of the liver?
falciform ligament
the constituents of bile
bile pigments (mainly bilirubin), cholesterol, phospholipids, fatty acids, water and electrolytes
what are bile pigments derived from?
the breakdown of haemoglobin
Cells involved in formation of bile pigments
kupffer cells
what is the role of bile salts?
emulsify fats to increase the absorption of fats in the small intestine
where can the bile go from the common bile duct? and what controls its path?
- into duodenum or 2. into gallbladder
The sphincter of Oddi- when contracted, bile moves mainly into the gallbladder. When relaxed, bile moves mainly to duodenum
what regulates the relaxation/contraction of the sphincter of oddi?
CCK (cholecystokinin)
what do bile acids do?
emulsify fats
why is the gallbladder bile more concentrated?
Na+ and Cl- are reabsorbed causing osmotic water reabsorption.
Purpose of gallbladder
store ad distribute bile
what causes gallbladder to expel bile and how does it do it?
under stimulation of CCk and efferent stimulation from the vagus the gallbladder contracts to release bile
which two substances inhibit bile acid secretion?
somatostatin and noradrenaline
