histology of the liver

Question 1

what are the parenchyma (of the liver) and the pancreas composed of?

Answer 1

glandular epithelial cells

Question 2

functions of the liver - 10

Answer 2

> oxidise triglycerides to produce energy
synthesise plasma lipoproteins
synthesise cholesterol
convert carbohydrates and proteins into fatty acids and triglycerides
regulate blood glucose concentrations by glycogenesis, glycogenolysis and gluconeogenesis
synthesise plasma proteins ie albumin
detoxification of metabolic waste products
detoxification of toxins and drugs
storage of glycogen, some vitamins and iron
synthesis and secretion of bile

Question 3

what is the liver capsule

Answer 3

it is a collagenous connective tissue capsule, which is in turn covered by a layer of mesothelial cells derived from the peritoneum

Question 4

what makes up the structure of the liver

Answer 4

is made up of segments called lobules - each one is sort of hexagon and has a branch of hepatic vein called the centrolobular vein - or the central vein at its centre and portal triads at each corner

*what does it look like?

Question 5

portal triads

Answer 5

branches of the vessels which enter at the porta hepatic ie the hepatic portal vein and the hepatic artery
>also have a tube that leaves the liver at the aorta hepatis ie the bile duct

Question 6

portal tracts include branches of…

Answer 6

hepatic portal vein
hepatic artery
bile ductule (lined by cholangiocytes)
– they also typically include lymphatic vessels

Question 7

hepatocytes

Answer 7

> epithelial cells
main cells of the liver
they are plates or sheets of cells with spaces in-between for blood to flow through - these blood flow channels are called sinusoids

Question 8

sinusoids

Answer 8

they are lined with endothelial cells and there is a narrow space inbetween these lining cells and the hepatocytes
>the space of Disse ie the perisinusoidal space … and the microvilli of the hepatocytes project into the space
>the endothelium is fenestrated so the liquid component of the blood has free access to the hepatocytes but blood cells do not

Question 9

connective tissue of the liver

Answer 9

Beside the liver capsule, the portal tracts are accompanied by collagenous connective tissue. The parenchyma of the liver is supported by reticular fibres (Type III collagen), along with some Type I collagen, that is found in the space of Disse

Question 10

hepatic stellate cells in the space of Disse

Answer 10

They are modified fibroblasts and make connective tissue. They also store vitamin A within fat droplets in their cytoplasm. In some pathological conditions (e.g. cirrhosis) they transform into myofibroblasts and produce scar tissue in the liver.

Question 11

macrophages of sinusoids : kupffer cells

Answer 11

macrophages = kupffer cells

>these cells remove particulate matter from the blood and help remove worn out RBCs

Question 12

what is bile

Answer 12

an alkaline solution containing water, ions, phospholipids, bilirubin and bile salts

Question 13

what is bilirubin

Answer 13

is a red/orange compound which results in the breakdown of haemoglobin in the spleen and is excreted in bile

Question 14

why are bile salts necessary

Answer 14

for: the emulsification of fats in the digestive tract

Question 15

primary bile modifications

Answer 15

is modified in several ways by cholangiocytes that line the biliary tree

Question 16

bile production

Answer 16

> all hepatocytes produce bile

>bile flows via bile canaliculi toward the bile ducts in the portal tracts and thence to the hepatic ducts

Question 17

what are the bile canaliculi?

Answer 17

they are small channels formed by tight junctions in the cell membranes of adjacent hepatocytes