Exam3Lec3Digestive3 Flashcards
What is the largest gland in the body?
Liver
What is the hepatic lobule made up of?
cells, CT, blood vessels, sinuses + biliary tree
What are the structures of the hepatic lobule?
- Classic Lobule
- Portal Lobule
- Liver Acinus
Classic lobule
1. Shape
2. Central vein lxn
3. Portal triad lxn
- Shape: hexagonal
- Central vein lxn: at the center
- Portal triad lxn: at each point of the hexagon
Portal lobule
1. Shape
2. Central vein lxn
3. Portal triad lxn
- Shape: triangular
- Central vein lxn: at each point of the triangle
- Portal triad lxn: at the center
Liver Acinus
1. Shape
2. Central vein lxn
3. Portal triad lxn
- Shape: oval (elliptical)
- Central vein lxn: horizontal ends
- Portal triad lxn: vertical ends
List the location and fxn of each zone of the liver acinus
1. Zone 1
2. Zone 2
3. Zone 3
- Zone 1: = closest to center (axis) -> receive nutrients + toxins first
- Zone 2: Zone 2 = middle ->receive nutrients + toxins 2nd
- Zone 3: furthest from center (axis) receive nutrients + toxins last
Toxins mainly affects which zone of the liver acinus? Oxygen depletion mainly affects which zone of the liver acinus?
toxins mainly affect zone 1; oxygen depletion mainly affects zone 3
What are the 3 types of liver cells?
Hepatocytes, Hepatic Stellate Cells (Ito cells), Kupffer cells
What are hepatocytes?
large polygonal cells w/ microvilli
What is the endocrine and exocrine fxn of hepatocytes?
What is the exocrine fxn regulated by?
What do the organelles do?
Endocrine fxn = make + secrete proteins/lipoproteins into the blood
Exocrine fxn = make + secrete bile into bile ducts and gallbladder
Exocrine fxn regulated by CCK
Organelles degrade toxins (sER) + store lipofuscin pigment (lysosomes)
Granules store glycogen + lipids stain acidophilic (pink)
Hepatic Stellate Cells = Ito Cells
1. Lxn
2. Fxn
- Lxn:Space of Disse
- Fxn: store fat + vitamin A & produce type I collagen fibers
Kupffer Cells
1. Lxn
2. Fxn
- Lxn: inside sinusoids (capillaries)
- Fxn: breakdown of damaged RBCs forms bilirubin (pigment)
Can act as macrophages (phagocytic cells) in the sinusoids
What is the space of disse?
The space b/n the hepatocytes & the endothelial cells of the sinusoid
What structures are extended/secreted into the space of disse?
- Microvilli of hepatocytes extend into this space for absorption
- Processes of Kupffer cells extend into this space + act as macrophages
- Ito cells secrete type I collagen fibers into this space
What is the CT of the liver comprised of?
- Glisson capsule (dense CT)
- Fibroblasts + type I collagen= around the portal triads
- reticular (type III collagen)= perisinusoidal space and around the central vein
What can occur if there is damage to hepatocytes? What does each liver cell do?
causes them to release cytokines to recruit cells to the area
Kupffer cells can act as macrophages to breakdown damaged cellular material
Ito cells become activated ->transform into myofibroblasts -> produce type I collagen fibers into the space of Disse
An increase in fibrosis around the portal vein ____ blood flow, which leads to ____ blood pressure. This can lead to ____
An increase in fibrosis around the portal vein decreases blood flow, which **increases **blood pressure. This can lead to portal HTN.
What is cirrhosis?
What is it caused by?
* Can hepatocytes regenerate?
* death of hepatocytes leads to what?
- Progressive hepatocyte destruction leads to the destruction of normal liver unit structure
Causes: alcohol toxicity, some forms of viral infection, and autoimmune liver disease. - Hepatocytes can regenerate…but NOT their portal system connections
- Increase in fibrocollagenous tissue (type I collagen) leads to formation of “scar tissue”
chronic liver damage
What are 3 causes of cirrhosis?
alcoholism, certain viral infections, autoimmune disease
What makes up the vascular system of the liver (5)?
- Portal vein
- Hepatic vein
- Interlobular vessels in triads
- Sinusoids
- Central vein
portal vein → hepatic vein → interlobular vessels → sinuses → central vein
What are the blood vessels of the liver unit and list the fxn for each?
- Portal vein: brings deoxygenated blood from the intestines, pancreas + spleen to the liver = 75% of blood
- Hepatic artery: brings oxygenated blood from the heart to the liver = 25% of blood
- Interlobular vessels: branch off from the hepatic artery and deliver blood to the sinusoids
- Sinusoids: (=discontinuous capillaries) deliver blood to the central vein
- Central vein: travels alone in the center of the liver unit (i.e., lobule)
Central vein: In the center of the lobule = not in triad
Portal triad = ____ + ____ + ____
portal triad = portal vein +hepatic artery + bile duct
What is the order of the biliary tree?
Bile Canaliculi ->Bile Ductule (interlobular ducts = in portal triad) -> Common Bile Duct
What is the canaliculi of the biliary tree?
hepatocytes w/ tight junctions
What is the common bile duct of the biliary tree?
Common bile duct = hepatic duct (from liver) + cystic duct (from gallbladder)
What type of epithelium lines the ductule and duct of the biliary tree?
Ductule = simple cuboidal epithelium
Duct = simple columnar epithelium + microvilli
Where and when is bile eventually secreted?
Bile is eventually secreted into the duodenum of the small intestine
After hormonal cholecystokinin – CCK stimulation (from enteroendocrine cells in small intestine) in response to the presence of fat in the duodenum
What type of epithelium lines the gallbladder?
simple columnar w/ microvilli
What does the mucosa of the gallbladder form and lack?
Forms folds + lateral plicae for increased surface area
Lacks muscularis mucosa
mucosa = epithelium + lamina propria (loose CT) + muscularis mucosae
What is the fxn of the gallbladder?
stores + concentrates bile from the liver
Also absorbs water + electrolytes
What is bile secretion regulated by?
CCK (cholecystokinin)
How is bile secretion regulated by CCK (cholecystokini)?
- Fat in the duodenum stimulates enteroendocrine cells
- Enteroendocrine cells secrete CCK into the blood
- Activation of bile secretion from gallbladder -> into duodenum
What do gallstones in the cystic duct and gallstones in the bile duct lead to?
- Gallstones in the cystic duct: this blockage leads to cholecystitis
- Gallstones in the bile duct : this blockage leads to obstructive jaundice
What is the exocrine fxn of the pancreas?
Exocrine (serous) glands secrete digestive enzymes into duodenum
What is the exocrine fxn of the pancreas regulated by?
Regulated by Secretin + CCK via enteroendocrine cells:
* Secretin stimulates HCO3- secretion
* Cholecystokinin (CCK) stimulates zymogen secretion
Secretes HCO3- & Na+ & H2O into the duodenum
Secretes digestive zymogens into the duodenum
What is the organization of the exocrine gland of the pancreas?
- Acinus
- Intercalated duct
- Intralobular duct
- Interlobular duct
- Main duct
NOTE: there are NO striated ducts in the pancreas, only the salivary glands
What is the fxn of the acinus in the exocrine gland of the pancreas?
secrete fluid + zymogens (lipase, trypsin, chymotrypsin, amylase)
The pancreatic lobules consist largely of what?
exocrine acini and their intralobular duct system
Duodenum:
* What is the absorptive cell?
* What does it contain?
* What does entrokinase activate?
- Absorptive cell: Enterocyte with microvilli
Contains:enterokinase within the cell membrane of microvilli. - Entokinase activates pancreatic proenzymes (zymogens)
enterokinase from microvilli activates what?
pancreatic proenzymes (zymogens)
What is the fxn of the intercalated duct and note the type of epithelium it contains
simple squam. centroacinar cells secrete HCO3- & Na+
What type of epithelium makes up the intralobular duct and the interlobular duct?
- Intralobular duct = simple cuboidal/columnar (NO striations)
- Interlobular duct = simple columnar
What does exocrine liver and endocrine liver secrete into?
Exo: into the bile canaliculi
Endo: into the sinusoids
What is the fxn of the main duct of the pancreatic exocrine gland?
- secretes fluid + digestive enzymes into the duodenum
- Joins the common bile duct before entering duodenum
What is cystic fibrosis?
What does it effect?
Decreased Cl- secretion + Na+ absorption -> thick mucous in pancreatic ducts
effects exocrine glands of pancreas: The total loss of pancreatic exocrine secretion impairs protein and fat absorption (exocrine pancreatic insufficiency)
effects exocrine glands of pancreas
What is the fxn of the endocrine gland of the pancreas?
Regulates blood glucose (sugar) levels
What is the fxn of islets of Langerhans cells?
secrete hormones into the blood
What hormones are secreted by Islets of Langerhans
- B cells: secrete insulin & decreases blood glucose
- A cells: secrete glucagon & increases blood glucose
- D cells: secrete somatostatin & inhibit A cells
- F cells: secrete pancreatic polypeptide
