Histology - Liver, Pancreas, Gallbladder

Question 1

List some of the functions of the liver

Answer 1

• oxidise triglycerides
• synthesise plasma proteins and lipoproteins
• synthesize cholesterol
• convert carbs and proteins into fatty acids and triglycerides
• regulates blood glucose (glycogenesis, glycogenolysis, gluconeogenesis)
• detox metabolic waste
• detox drugs and toxins
• store vitamins and iron
• synthesise and secrete bile

Question 2

What vessels are present in the portal triad?

Answer 2

• hepatic portal vein
• hepatic artery
• bile duct (common hepatic duct combined with cystic bile duct)

Question 3

describe the capsule that surrounds the liver

Answer 3

Mesothelium (simple squamous epithelium)
-->
Collagenous connective tissue
-->
Liver parenchyma

Question 4

Describe the lobules of the liver

Answer 4

• Roughly hexagonal in shape
• Centrilobular vein (terminal hepatic vein)
• Portal triads

Question 5

Describe the portal triads (portal tract) that surround the lobules of the liver

Answer 5

Composed of:

• bile duct
• portal vein
• hepatic artery

and:

• lymphatic vessel
• branch of the vagus nerve

They are supported by collagenous connective tissue

Question 6

Describe the flow deoxygenated blood through a liver lobule

Answer 6

hepatic portal vein (branch) and hepatic artery
-->
hepatic sinusoids
-->
centrilobular vein

Question 7

Are there distinct connective tissue septa between the liver lobules?

Answer 7

No, but the septa do exist

Question 8

Describe the lining of a bile ductule

Answer 8

Lined by cholangiocytes

simple cuboidal epithelium

Question 9

Describe hepatocytes

Answer 9

Epithelial cells

Produce primary bile

Have microvilli:

• project into the perisinusoidal space
• project into the bile canaliculi

Join to form plates of cells, leaving sinusoids between them

Question 10

Describe a hepatic sinusoid

Answer 10

the space between the plates of hepatocytes

Lined by endothelial cells (as the hepatocytes plates have an endothelial lining)

Supplied by a mix of blood from the hepatic artery and hepatic portal vein

Question 11

What is a hepatic acinus?

Answer 11

a functional subunit of the liver

an alternate functional rather than structural view (classic hepatic lobule)

Question 12

Describe the lining of the plates of hepatocytes

Answer 12

The hepatocytes plates are lined by a fenestrated endothelium

They are separated by a thin gap called the the space of Disse (perisinusoidal space)

The microvilli of the hepatocytes project into the perisinusoidal space

Question 13

Describe the perisinusoidal space (space of Disse)

Answer 13

gap between the hepatocytes and their endothelial lining

the hepatocytic microvilli project into it

Has hepatic stellate cells

Question 14

Describe the significance of the fenestrated nature of the hepatocytic endothelium

Answer 14

The liquid component of the blood can reach the hepatocytes

But the blood cells can’t as they are too large to fit through the fenestrations

Question 15

Describe hepatic stellate cells

Answer 15

Modified fibroblasts

Function:

• make connective tissue
• store vitamin A within fat droplets in their cytoplasms

found in the perisinusoidal space

(in cirrhosis they turn into myofibroblasts and produce scar tissue instead)

Question 16

Describe Kupffer cells

Answer 16

Macrophages in the hepatic sinusoids

Function:

• remove old red blood cells
• remove particulates from the blood

Question 17

Describe bile

Answer 17

Alkaline solution

Contains:

• water
• ions
• phospholipids
• bilirubin
• bile salts

Question 18

Describe bile production

Answer 18

Primary bile is produced by hepatocytes

This is then modified by cholangiocytes:
- bicarbonate ions added
- water added
-

Question 19

Describe cholangiocytes

Answer 19

Simple cuboidal epithelial cells

Lines the biliary tree

Modifies primary bile

Question 20

Describe the flow of bile through a hepatic lobule and out of the kidneys

Answer 20

Bile produced in hepatocytes
-->
Flows in bile canaliculi
-->
bile ducts (portal triad)
-->
hepatic ducts

Question 21

Describe the bile canaliculi

Answer 21

Small channels between the membranes of adjacent hepatocytes (joined by tight junctions)

They collect the bile produced by the hepatocytes

The hepatocytes have microvilli that project into the canaliculi, and release the produced bile

Question 22

Describe the layers of the gallbladder

Answer 22

lumen
-->
simple columnar epithelium with microvilli
-->
lamina propria (connective tissue, rich in vasculature)
-->
smooth muscle
-->
adventitis (collagenous)

Question 23

Describe the function of the gallbladder

Answer 23

Stores and modifies bile

Removes 80-90% of bile volume:

• pumps Na and Cl- ions from the bile
• water follows the ions
• water is removed by lymphatics

Delivers bile to duodenum:

• contracts to deliver bile
• controlled by nervous (vagal), and hormonal (cholecystokinin) influences

Question 24

Describe the epithelium of the gallbladder

Answer 24

Tall simple columnar epithelium with microvilli

Question 25

Describe cholecystitis

Answer 25

Gallbladder inflammation ``` Gallstones obstruct cystic duct --> gallbladder pressure increases --> muscular wall hypertrophy and inflammation ```

Question 26

Is the pancreas mainly exocrine or endocrine?

Answer 26

Its function in 99% exocrine

Question 27

Describe the exocrine function of the pancreas

Answer 27

produces digestive juices containing: - proteases - lipases - nucleases - amylases - etc. (^^ all in proenzyme form, are activated in the duodenum) Juice feeds into the duodenum via the pancreatic duct

Question 28

Describe the endocrine pancreas

Answer 28

diffuse islands of tissue called islets of Langerhans makes up 1-2% of the pancreas

Question 29

Describe the capsule of the pancreas

Answer 29

Thin connective tissue capsule It is continuous with the septa that divide the pancreas into its lobules

Question 30

Describe the hepatopancreatic ampulla

Answer 30

``` Main pancreatic duct joins Common bile duct forming Hepatopancreatic ampulla ``` It feeds into the duodenum

Question 31

Describe an pancreatic intercalated duct

Answer 31

The duct extends into the acinus the duct cells in the acinus are called centroacinar cells

Question 32

Describe centroacinar cells

Answer 32

the duct cells of intercalated ducts that extend into the acinus

Question 33

Describe a pancreatic aninus

Answer 33

an acinus of secretory cells surrounding an intercalated duct