Gastroenterology V Flashcards
(20 cards)
What are the 2 most important digestive glands?
Where is their embryological origin?
- liver and biliary tract
- pancreas
- origin
- endoderm
- outgrowth of the foregut (duodenum)
- during the 4th week
Describe the parts and components of the pancrease
- parts
- head
- body
- tail
- stroma (connective tissue)
- capsule
- septa
- exocrine
- secretory acini (digestive enzymes)
- ducts (into the duodenum)
- endocrine
- islets of langerhans
- no ductal system b/c secrete into the blood stream/extracellular space
What are the parts of the exocrine pancreas? Explain each of their functions.
- serous acini
- pancreatic acinar cells
- protein-secreting cells
- pyramidial in shape (euchromatic nucleus)
- zymogen granules
- trypsinogen, chymotrypsin
- lipases
- amylases
- pancreatic acinar cells
- ductal system - begins from within the acinus
- intralobular ducts
- centroacinar cells
- within the acinus
- intercalated ducts
- low cuboidal
- secrete HClO3- and water (decrease acidity of chyme)
- intralobular collecting
- cuboidal - low columnar
- centroacinar cells
- interlobular ducts
- simple columnar
- main duct
- interlobular ducts
- intralobular ducts
Describe the components and function of the endocrine pancreas. It makes up about what portion of the organ?
- islets of langerhans
- more in tail
- 1-2% of the organ
- impact
- carbohydrate metabolism
Describe the Islet tissue. What are the different types of Islet cells? Percent copmosition? Horomone production?
- irregular cords
- rich in capillaries
- fenestrated endothelium
- islet cells
- A cells (alpha-cells) (20%) – big & on periphery
- glucagon
- B cells (beta-cells) (70%) – distrubted through out & smaller than A
- insulin
- D cells (delta-cells) (5-10%)
- somatostatin
- other enteroendocrine cells
*
- A cells (alpha-cells) (20%) – big & on periphery
How does the liver act as an exocrine gland? endocrine gland?
What are its other functions?
- Exocrine
- bile
- Endocrine
- plasma proteins
- modification of hormones
- Function
- Lipid metabolism (VLDLs) – transport triglycerides
- Glucose metabolism
- can store glycogen
- storage & conversion
- vitamens ADEK (fat soluble)
- does not store D, but does convert it to active form
- iron
- liver produces transferin and ferroportin
- vitamens ADEK (fat soluble)
- Detoxification of drugs (esp steroid) and environmental toxins
- smooth ER & peroxisomes
What are the two parts of the liver & their respective components?
- Stroma
- Gliffon’s capsule
- Network of reticular fibers (not v. thick)
- if see collagen bundles, something is wrong
- Gliffon’s capsule
- Parenchyma
- plates of hepatocytes: lobules (Hexagonal structure)
- organized around blood vessel
Describe the blood supply to the liver
- Hepatic artery (25%)
- oxygenated blood
- Portal vein (75%)
- nutrients, toxins, hormones
- hemoglobin breakdown products
- Hepatic vein
- drain into inferior vena cava
Describe the structure of vasculature for blood entering the liver
From periphery toward center
- Conducting branches
- hepatic artery
- portal vein
- Interlobular branches
- parts of portal triads
- interlobular spaces
- Terminal branches
- deliver blood to hepatic sinusoids
- last branches before the capillary bed
- 2nd time this blood is running througha capillary system b/c it went through a capillary system in teh GI
Describe the structure of vasculature for blood leaving the liver
- Hepatic sinusoids
- discontinous capillaries
- Separate
- plates of hepatocytes
- drains into central vein
- Central veins
- center of the lobule
- thin wall
- sublobular veins
- under the lobule
- more connective tissue
- larger than central vein with thicker walls
- collecting rributaries
What are the cell types present in the liver? Describe their unique characteristics
- hepatocytes
- principal cells (60%)
- protein, lipid, and carbohydrate metabolism
- may have 2 nuclei, lots of mitochondria
- secrete bile
- principal cells (60%)
- Kupffer cell
- macrophages – designed to remove senescent red blood cells
- dark, irrecular nuclei (derived from bone marrow, mesoderm)
- within hepatic sinusoids
- macrophages – designed to remove senescent red blood cells
- Hepatic stellate cells
- (=Ito cells)
- storage of vitamin A
- lipid metabolism
- derived from fibroblasts
- if inflamed start laying down rough type I fibers
- (=Ito cells)
What is the cause of cirrhosis?
What are the negative implications of cirrhosis?
What are the two types?
- caused by proliferation of connective tissue by Ito cells
- leads to fibrosis
- problems
- obstruction of blood flow
- obstruction of bile flow (starts intoxicating the liver)
- Types
- Macronodular
- hepatitis
- micronodular
- alcoholism
- Macronodular
Describe the structure of a hepatic lobule
- Shape
- hexagonal prism
- central vein
- hepatic sinusoids
- blood flow
- from periphery to center
- blood flow
- plates of hepatocytes
- one cell-thick, so gets washed by blood on 2 of its surfaces
- anastomosing
- bile canaliculi (counter current system)
- tiny canal inside the plate
- drain into bile ductule
- flow from center to periphery
What structure is formed within the portal canals?
How many portal canals surround each classic lobule?
- portal triad
- portal vein (interlobula branch)
- hepatic artery (interlobular branch)
- interlobular bile duct
- 6 portal canals surrounding each classic lobule at each corner of the hexagonal prism
How could you identify the portal vein, hepatic artery and bile duct in a cross section?
portal vein and hepatic artery have simple squamous endothelium
portal vein is much bigger than hepatic artery
bile duct will be lined with simple cuboidal epithelium
What is the name between the hepatic sinusoids and the hepatocytes?
Space of Disse (perisinusoidal space)
- Gap
- between hepatocytes and endothelial cells
- exchange materials between hepatocytes and blood
- hepatocytes
- have microvilli that project into the space
- locaiton of ito cells
When talking about portal lobules, what function is being highlighted?
Describe its components
- Emphasizing the production of bile & is centered around the portal triad
- Liver
When talking about liver acinus, what function is being highlighted?
Describe its components
- centered on terminal branches of portal veins; cenral veins & portal canals demarcate the boundary, which is roughly rhomboid
- emphasizes the different oxygen and nutrient content of blood present in the lobule
- Zone 1
- closest to intralobular blood vessels bringing blood to the acinus
- most O2, nutrient
- get intoxicated first (or bile stasis)
- last to die, regenerated first
- Zone 2
- middle
- Zone 3
- least oxygen
- less toxins
- die first from ischemia
Describe the components of the biliary tree
- Bili canaliculi
- does not have own lining – within plates
- lining
- hepatocytes
- Bile ductules (true duct b/c habr lining)
- lining
- ductal cells
- lining
- Interlobular bile ducts
- simple cuboidal lining
- ductal cells
- simple cuboidal lining
What are the layers of the gallbladder & tissue type?
- mucosa
- simple columnar epitlelium
- lamina propria
- no muscularis mucosae (poorly defined boundary between mucosa & submucosa)
- submucosa
- conective tissue
- muscularis externa
- adventitia/serosa
- connective tissue
