Lecture 31 Monogastric Secretions (Pancreatic, Hepatobiliary, Intestinal) Flashcards
What are functions of the liver?
Production of important compounds: e.g. cholesterol, bile
Detoxification
Storage of micronutrients
Blood sugar balance (glycogen storage)
Protein synthesis e.g albumin, acute phase proteins etc.
Immune functions
Name the three vessels found in the portal triad
bile duct
portal vein
hepatic artery
What is the name of the vessel in which blood from the portal vein and hepatic artery drains into after flowing through sinusoids in the hepatic lobule?
Central vein or Terminal Hepatic Vein
What large vessel does the central vein lead to?
Caudal vena cava (carried to this via the hepatic veins)
As blood runs towards the central vein, bile runs toward the _____ in the triad
Bile duct
What is the name for the specialized macrophages within the hepatic sinusoids>
Kupffer cells
A small space between the sinusoid endothelial layer and the hepatocytes
space of disse
A cell that lies within the space of Disse: normally inactive, but will produce fibrous scar tissue to wall off the area if any damage occur to the hepatocytes.
stellate cell
What is in bile? (5)
- Bile salts
- Cholesterol
- Bilirubin
- Electrolytes
- Water
Where is bile secreted into immediately from hepatocytes?
Bile canaliculus
What compound, which is a product of hemoglobin breakdown, gives bruises their yellowish colour?
Bilirubin
What acid do hepatocytes conjugate bilirubin with?
Glucuronic acid
What is the cause of the yellowish discolouration noted in jaundice patients?
Unconjugated bilirubin being deposited into tissues.
Conjugated bilirubin can be converted by colonic bacteria into _______ and __________ which gives the brown colour of feces
urobilinogen and stercobilin
What compound gives urine a distinct yellow colour?
Urobilinogen
Toxins or wastes generally undergo a two‐phase process before they are excreted into the bile: 1. ___________________________________________
2. the compound made much more water‐soluble and permits it to remain soluble in the bile.
- the compound undergoes change its structure sufficiently so that it is no longer a danger;
Toxins or wastes generally undergo a two‐phase process before they are excreted into the bile: Toxins or wastes generally undergo a two‐phase process before they are excreted into the bile: 1. the compound undergoes change its structure sufficiently so that it is no longer a danger;
2. ______________________________________________________________________
2, the compound made much more water‐soluble and permits it to remain soluble in the bile.
Amino acid most commonly used to form bile salts:
Taurine (it becomes taurocholic acid when bound to cholesterol)
How are bile salts formed?
By conjugating cholesterol with an amino acids
Are bile salts polar or non polar?
Highly polar and thus very water soluble
Which hormone is responsible for increasing bile production and secretion?
Cholecystokinin (CCK)
_________ part of bile salts will be on the inside of the micelle, and the _________ part will be on the outer surface of the micelle.
Lipophilic, hydrophilic
What exocrine function does the pancreas have?
To produce enzymes responsible for digesting foods: amylase, protease, lipase
What two inputs increase the production and secretion of pancreatic enzymes?
CCK and vagal stimulation
What hormone is responsible for the pancreas to increase secretion of alkaline solution?
Secretin
Why does the pancreas also secrete an alkaline solution?
Because its enzymes need an optimal pH to work (7-8) and it is important to increase the low pH chyme leaving the stomach
Describe the way the small intestine mucosa looks
There are villi (projections) and crypts (invaginations), the enterocytes are also covered in microvilli
What can change the lengths of the villi of the small intestine?
The smooth muscle of the internal muscularis mucosa which is embedded in the submucosal layer.
Unique aggregates of B and T lymphocytes, macrophages, and dendritic cells in the submocosa of the ileum
Peyers patches
Where are intestinal stem cells located?
Within the crypts
How do crypt enterocytes differ from villus ones?
The crypt enterocytes are secreting chloride, sodium, and water to facilitate absoprtion by absorptive enterocytes. Once migrated to the top of the villus the enterocytes job is to absorb.
What do goblet cells do?
Secrete mucus
Enteroendocrine cells - what are their functions?
Monitor pH, osmolarity, and composition of the ingesta in the lumen.
Secrete hormones (CCK and secretin)
Paneth cells - what are their function?
To protect crypt stem cells by producing antibacterial/fungi/viral secretions
What type of epithelium lines the crypts and villi of the small intestine?
Simple columnar with microvilli
What is an M cell or a dome cell?
An immune cell which can capture pathogens and present them to other immune cells to determine if an immune response is needed. they are sentinel cells.
How long does it take for crypt cells to reach the villous tip?
4-5 days
How is blood supplied to the small intestinal villus?
Hairpin Arrangement:
A central arteriole emerging from the submucosal artery
carries oxygenated blood upward toward the villous tip. At the tip, a capillary network ramifies outward and is collected into venules and veins, which progress downward at the periphery just beneath the epithelium.
What is CFTR?
the cystic fibrosis transmembrane conductance regulator, a cyclic AMP-dependent chloride channel. As chloride moves through this channel, fluid is drawn into the lumen of the intestine as Na+ moves to follow the Cl-
How is fluid driven into the lumen of the small intestine?
Through the help of CFTR which pumps Cl- out of the cell into the lumen. Since Na+ follows to even the electric gradient, water naturally follows.
Which part of the enterocytes does the fluid follow the NaCl secretion through?
Through areas of tight junctions
How does bacteria like chloera affect the enterocytes which leads to severe diarrhea?
Bacteria activate adenylate cyclase lead to chloride channels being stuck in the open position due to elevated levels of cAMP. this causes fluid to be drawn into the lumen in higher than normal levels since NaCl is being moved.
How does colon mucosa differ from small intestine?
There are no villi (but there are crypts)
What is a comparable structure to the Peyers patches found in the colon?
Lymphoid Follicles
Name the four layers of the GI tract starting on the side of the lumen
Mucosa
Submucosa
Muscularis mucosa (external)
Serosa
