Lecture 3: Digestive III Flashcards
What is the largest gland in the body?
Liver
What makes up the CT in the liver (3)?
- Glisson capsule (dense CT)
- Reticular fibers (type III collagen fibers) = perisinusoidal space and around the central vein
- Fibroblasts and Type I collagen = around the portal triads
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 is the function of the portal vein? What percentage of blood does it bring?
- Brings deoxygenated blood from the intestines, pancreas, and spleen to the liver
- 75% of blood
Large lumen with thin wall
What is the function of the hepatic artery? What percentage of blood does it bring?
- Brings oxygenated blood from the heart to the liver
- 25% of blood
Small lumen with thick wall
What is the function of sinusoids (discontinuous capillaries)?
Deliver blood to the central vein
Lined with endothelial cells
What is the function of the central vein?
Travels alone and receives blood from the sinusoids
In the center of the lobule = not in triad
What are hepatocytes?
large polygonal cells with microvilli
What is the endocrine function (1) and exocrine function (1) of hepatocytes?
- Endocrine = make and secrete proteins/lipoproteins in the blood
- Exocrine = make and secrete bile into bile ducts
What do the granules in hepatocytes do? What do the organelles do?
- Granules = store gylcogen and lipids → stain acidophilic (pink)
- Organelles = degradge toxins (sER) and store lipofuscin pigment (lysosomes)
What cell is important for making bile?
Hepatocytes
What are hepatic stellate cells also called?
Ito cells
Where are hepatic stellate cells (Ito cells) located? What is their function (3)?
- Located in Space of Disse
- Store fat + Vitamin A & produce type I collagen fibers
Where are Kupffer cells located? What is their function (2)?
- Located inside sinusoids (capillaries)
- Breakdowns damaged RBCs = forms bilirubin (pigment formed)
- Can act as macrophages (phagocytic cells) in the sinusoids
What is the Space of Disse? What does it contain (3)?
- The space b/n the hepatocytes & the endothelial cells of the sinusoid
- 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
How does portal hypertension occur?
- Collagen type I deposits into the Space of Disse = results in fibrosis and alteration of the portal venous blood flow
- ↓ flow in portal vein → ↑venous pressure = portal hypertension
What makes up the portal triad (3)?
hepatic artery + portal vein + bile duct
List order in which bile flows from hepatocytes (4)
Hepatocytes secrete bile into bile canaliculi → bile ductule (in portal triad) → interlobular bile duct (in portal triad) → common bile duct (hepatic bile duct + cystic duct)
What causes cirrhosis (4)? What is the result of it?
- Causes = alcohol, toxicity, some forms of viral infection, and autoimmune liver disease
- Result = progressive hepatocyte destruction → leads to destruction of normal liver unit structure = loses hexagon shape
Hepatocytes can regenerate, but their connection with the portal system and biliary drainage are destroyed
What causes scar tissue to form in cirrhosis?
Increase in fibro-collagenous (aka type I collagen)
Explain the mechanism of the cells in the liver that cause Cirrhosis
- Hepatocytes + Kupffer cells + Lymphocytes secrete cytokines →Activate Ito cells
- Ito cells (satellite cells) differentiate into myofibrils→make collagen
- This leads to an ↑in collagen (type 1)
What are the 3 structures of the liver?
- Classic lobule
- Portal lobule
- Liver acinus
What is the shape of a classic lobule? Where are its central vein and portal triads located?
- Hexagon shape
- Central vein (1) is at the center
- Portal triads are at each point of the hexagon
How is the portal lobule shaped? Where are its central veins and portal triad located?
- Triangle shaped
- Central veins (3) are at each point of the triangle
- Portal triad (interlobular bile duct) is at the center
How is the liver acinus shaped? Where is its central vein and portal triad located?
- oval (elliptical)
- Central veins (2) (distributing vessels) are at horizontal ends
- Portal triads (2) are at vertical ends
What are the 3 zones of the liver acinus?What are their functions?
- Zone 1 = closest to center (axis) → receive nutrients + toxins first
- Zone 2 = middle → receive nutrients + toxins 2nd
- Zone 3 = furthest from center (axis) → receive nutrients + toxins last
Toxins mainly affect zone 1; oxygen depletion mainly affects zone 3
Explain how Congestive Heart Faliure (CHF) and Liver Necrosis can occur in Zone 3 of the liver acinus
- CHF causes a decrease in O2
- ↓ O2 causes liver (ischemic) necrosis d/t insufficent oygenation
What type of epithelium does the gallbladder have?
simple columnar with microvilli
What are the functions of the gallbladder (2)?
- concentrates and stores bile from the liver
- Absorbs water and electrolytes
How is bile secretion in the gallbladder regulated by CCK (cholecystokinin) (3)?
- Fat in the duodenum stimulates enteroendocrine cells
- Enteroendocrine cells secrete CCK into the blood
- Activation of bile secretion from the gallbladder → into the duodenum
Where can gallstones form (2)? What is the result of gallstones affecting these areas (2)?
- gallbladder - cholecystitis (obstruction in the cystic duct)
- biliary tree - obstructive jaundice (obstruction of a bile duct)
What is the exocrine function of the pancreas?
- Exocrine (serous) glands secrete digestive enzymes into the duodenum
What two hormones regulate the pancreas exocrine glands? What do they stimulate?
- Secretin and CCK regulate via enteroendocrine cells
- Secretin stimulates bicarbonate ion (HCO3-) secretion
- CCK (cholecystokinin) stimulates enzyme (zymogen) secretion
zymogen = inactive → activated by enterokinase via microvilli of enterocytes
What are the 5 exocrine glands of the pancreas?
- Serous acinus gland
- Intercalated ducts
- Intralobular collecting ducts
- Interlobular ducts
- Main pancreatic duct
What does the serous acinus gland secrete?
secrete fluid + zymogens (lipase, trypsin, chymotrypsin, amylase)
What cells are located in the intercalated ducts? What is their function?
simple squam. centroacinar cells secrete water rich in sodium (Na+) and bicarbonate (HCO3-)
What type of epithelium do the intralobular collecting ducts have?
simple cuboidal/columnar (NO striations)
What type of epithelium do the inTERlobular ducts have? What is the function of the interlobular ducts?
- simple columnar
- transport secretory products
What is the function of the main pancreatic duct?
secretes fluid + digestive enzymes into the duodenum
Joins the bile duct (liver) before entering the duodenum
What is cystic fibrosis? What disease does it cause in children and young adults?
- genetic disorder
- Causes obstructive pulmonary disease in children and young adults
What causes cystic fibrosis? What does it result in?
Defective Cl- channel protein → decreased chlorine secretion + increased Na+ absorption = results in thick, viscous mucous which is difficult to clear out of lungs and pancreatic ducts
Defective Cl- channel and exocrine pancreatic insufficiency
What is the endocrine function of the pancreas? What cells are responsible for this?
Islets of Langerhans = secrete hormones that regulate blood glucose level
What are the principal cells (4) of the endocrine gland in the pancreas?
- B cells
- A cells
- D cells
- F cells
What hormone do B cells secrete? What is the function of this hormone?
secrete insulin = decreases blood glucose
What hormone do A cells secrete? What is the function of this hormone?
secrete glucagon = increases blood glucose
What hormone do D cells secrete? What is the function of this hormone?
secrete somatostatin = inhibit glucagon release by A cells
What hormone do F cells secrete?
pancreatic polypeptide
What are the black arrows pointing to?
Reticular fibers
What is 1, 2, 3, 4, and 5?
What is A, B, C?
What organ is shown in this image?
Gallbladder
What is A? B?
What is A, B, C, and D?
- A → Connective tissue
- B → Interlobular duct
- C → Acini
- D → Intralobular duct
What is C? D?
- C→ Acini
- D → Intralobular duct
What organ is this?
Pancreas
What is A, B, C, and D?
- A → Portal vein
- B → Hepatic artery
- C → Bile duct
- D → Sinusoids
What is C? D?
- C → Endocrine islet of Langerhans
- D → Acini of exocrine pancreas
What is A, B, C, and D?
- A & B → Portal vein
- C → Hepatic arteries
- D → Bile duct
What is A? B?
These cells can phagocytize damaged red blood cells. What are they called?
- Progressive hepatocyte destruction is marked by a loss of normal cellular architecture within the hepatic lobule. As a result, there is an overproduction of collagen, often seen in the space of disse. Which cell type is responsible for the production of collagen fibers in the liver?
a. Hepatocyte
b. Kupffer cell
c. Ito cell
d. Macrophage
c. Ito cell
- An exocrine function of the pancreas is to secrete a large volume of pancreatic fluid, rich in bicarbonate and sodium, that gets delivered to the duodenum during the process of digestion. Which of the following is important for this function?
a. Acinar cells
b. Interlobular duct
c. Intralobular duct
d. Centroacinar cells
d. Centroacinar cells
- Identify the indicated cell:
a. Kupffer cell
b. Hepatic stellate cell
c. Hepatocyte
d. Endothelial cell
a. Kupffer cell
- Which cell population in the liver is responsible for the production of bile?
a. Ito cells
b. Hepatocytes
c. Bile duct epithelial cells
d. Kupffer cells
b. Hepatocytes (exocrine fx)
- Identify the indicated structure:
a. Hepatic artery
b. Sinusoid
c. Bile duct
d. Central vein
c. Bile duct
