Accessory Organ Histology

Question 1

What two major endocrine secretions do pancreatic inslet (of langerhans) cells release?

Answer 1

1) Glucagon:
- secreted by A-cells
- increases glycogenolysis and lipolysis
- elevates blood glucose levels

2) insulin:
- secretary by B-cells
- increases glucose uptake into cells
- lowers blood glucose levels

Question 2

What products do pancreatic serous acini secrete?

Answer 2

1) proteases
- get activated by trypsin and work to digest proteins

2) a-amylase
- converts starches and glycogen into monosaccharides

3) lipases:
- digest lipids into subunits of glycerol, FAs and monogylcerides

4) nucleases:
- digests DNA and RNA into nucleotides

Question 3

What are the primary function of intercalated ducts?

Answer 3

Drain pancreatic acini and also secrete bicarbonate ions

Are lined by simple squamous/low-cuboidal epithelium

Contain centroacinar cells which are the primary cells that secrete the bicarbonate fluid
- are proximal to the lumen and pale-staining

Question 4

What stimulates serous cells of the exocrine acini into releasing their products?

Answer 4

CCK

Parasympathetic activity

Question 5

What stimulates the intercalated duct cells/centroacinar cells into secreting bicarbonate?

Answer 5

Secretin

Parasympathetic activity

NOTE: centroacinar cells are activity wise the same as intercalated duct cells

Question 6

Why are centroacinar cells so important?

Answer 6

They secrete bicarbonate which helps to make sure no damage is done by stomach acid and to make sure no remnant zymogens remain in the pancreas
- (would cause self-Autophagy if left there = pancreatitis)

also prevents premature activation of proteases/zymogens and nucleases

Question 7

Why does pancreatic tumors become metastatic so often?

Answer 7

The pancreatic tissues are highly vascularized and islet cells have such a high endocrine function
- there is little resistance from metastasis and a wide number of blood vessels to enter

also most pancreatic cancers are asymptomatic until they become near grade 4, making them exceptionally dangerous

most common site is head of pancreas and in ductal cells

Question 8

What are the major functions of the liver?

Answer 8

1) first pass metabolism
- drugs and absorbed macronutrients

2) bile synthesis and secretion

3) stores the following:
- glycogen
- triglycerides
- vitamins DEAK and B12
- iron and copper

4) produces hormones and plasma proteins

Question 9

What is a hepatic lobule?

Answer 9

The functional unit of the liver

Is a hexagonal shape with 3-6 portal triads within them. Portal triads are venules/arterioles and bile ducts with lymphatic vessels

Also contains hepatocyte plates

Question 10

What are hepatocyte plates?

Answer 10

Congregates of hepatocytes within hepatic lobules
- are supported by a delicate stroma and reticulum fibers

Also contain vascular sinusoids between plates which allows venous and arterial blood to mix before reaching the central vein
- also the sinusoids have thin epithelium (called peri sinusoidal space of disse) to allow for endocrine products to empty into the blood easier

Question 11

What are bile canaliculi?

Answer 11

The formation of two apical membranes of two hepatocyte plates
- carries bile to the bile ductules found in the portal triads

Multiple canaliculi form anastomoses and ultimately form bile canals of herring
- these canals empty into bile ductules in the portal triads

Question 12

What are the functions of hepatocytes?

Answer 12

• most diverse cell type of the body and are made up of large cuboidal/polyhedral cells with microvilli*
• have a large round centrally located binuclei is with eosinophilic (pink) cytoplasm

1) endocrine secretion
- albumin
- transferrin
- fibrinogen
- apolipoproteins

2) perform Gluconeogenesis

3) deamination
- converts free excess AAs into urea to be excreted

4) detoxification and conjugation of toxins

5) stores:
- glycogen
- triglycerides
- vitamins DEAK and B12
- copper and iron

note dont often produce scar tissues, that’s fibroblasts

Question 13

How are hepatocytes split into subsections?

Answer 13

Ones that do extensive protein synthesis = lots of RER granules

Ones that store glycogen = lots of glycogen granules

Ones that have no granules = lots of detoxification

Question 14

What is a classic lobule?

Answer 14

Structure of hepatic lobule that has a central vein with 3-6 portal triads draining into it
- hexagonal shaped lobule

Primary function = drains blood and emphasizes endocrine functions

Question 15

What is a Portal lobule

Answer 15

Contains 3 central veins with 1 portal triad in between.
- triangle shaped lobule

Emphasizes exocrine function and the flow of bile

Question 16

What is a hepatic acini?

Answer 16

Contains two portal triads and a lot of hepatocytes
- rhomboid shaped lobule

Emphasizes oxygen and nutrient distribution to hepatocytes

Contains 3 zones based on how close that are to the triads.
- zone 1 = closest to the portal triads and has the highest level of oxygen and nutrients (highest levels of function as well)

• zone 2 = 2nd closest to the portal triads and has highest level of oxygen and nutrients
• zone 3 = furthest from the portal triads and has lowest level of oxygen and nutrients
  (Lowest levels of function as well)

Question 17

Cirrhosis of the liver

Answer 17

Development of dense CT beyond the hilum of the liver causes proliferation of fibroblasts and hepatic stellate cells

Disrupts arrangement of lobules and functions of hepatocytes and sinusoids
- can cause secondary blood disorders/clotting disorders and hypoalbuminemia

almost always irreversible

Question 18

Fatty liver disease

Answer 18

Accumulation of large lipid droplets within hepatocytes (steatosis). Produces progressive inflammation of the liver and hepatitis

Most common causes are alcohol and obesity

usually reversible

Question 19

Jaundice

Answer 19

Occurs when too much bilirubin is present in the system
- liver cant produce bilirubin gluconuronide which is nontoxic

Causes yellowing of skin and eyes

Question 20

Difference between cholesterol and pigment gallstones

Answer 20

Cholesterol = yellow-white color

Pigment = brown-black color

Question 21

Stellate macrophages (Kupffer cells)

Answer 21

Located in the sinusoids of the hepatic lobules

Function is to remove effete erythrocytes and freeing heme and iron for either reuse or storage as ferritin complexes
- also act as APC’s and remove bacteria/pathogens from the portal system blood

Question 22

Hepatic stellate cells (ito cells)

Answer 22

Found in the perisinusoidal space

Function to store vitamin DEAK (but especially vitamin A and retinol)
- plays essential role in retinol homeostasis and liver regeneration

are the cells that become fibroblasts and lead to fibrosis of the liver as needed

Question 23

different vessels in the liver and their fucntions

Answer 23

Central vein

• located dead center in lobules
• collects processed/filtered blood from hepatocytes and empty’s it into the inferior vena cava

Portal venule

• found portal triads
• carries O2-poor/ unprocessed nutrient rich blood from GI tract into liver

Portal arteriole

• found in portal triad
• carries O2 rich/ processed nutrient rich blood from GI tract into liver

Bile ductule

• found in portal triad
• carries bile from gallbladder out into circulatory system

Question 24

Bile flow pathway

Answer 24

Gallbladder -> bile canaliculi -> bile canals of hering-> bile ductules in hepatic triads -> hepatic ducts -> common bile duct -> main pancreatic duct at hepatopancreatic ampulla -> duodenum via major duodenal papilla

Question 25

General facts about pancreatic cancer

Answer 25

Usually carcinoma of the duct cells

Usually arise in the head of the pancreas

Have a very high mortality rate since it is often asymptomatic until it has metastasized and has ample supply of blood vessels to use as hematogenous spread.

Question 26

What is the most common protein deficency in liver cirrhosis?

Answer 26

Hypoalbuminemia

Question 27

Neonatal hyperbilirubinemia

Answer 27

Is caused by improper maturity of hepatocyte SER function
- bilirubin isn’t metabolized into blirubin glucuronide which is non toxic and easily excreted into bile

Treatment = exposure to blue light (transforms unconjugated bilirubin into a photo-isomer that can be excreted to kidneys)