wk 1 GI and LIver Flashcards
structures entering and exiting the liver
(a) Portal vein bringing food-rich blood from the gut.
(b) Hepatic artery bringing arterial blood.
(c) Hepatic veins taking away processed blood into the vena cava.
(d) Lymphatics taking away some lymph.
(e) Hepatic ducts removing bile to the gallbladder and gut
liver blood supply
Hepatic artery – 25%
o Fully oxygenated blood to supply blood to organ
Portal vein – 75%
o Drains directly from the gut
o Any absorbed food that’s broken down goes into this vein to the liver
nerve supply of the liver
sympathetic & parasympathetic supply of perivascular structures, but very little at sinusoidal level
- Nerves have vv little to do with the control of the sinuses
structure of a liver lobule
- cells are arranged in perforated plates (these are one cell wide)
- Between these plates are sinusoidal blood channels
- This is the way the exchange of nutrients takes place between sinusoidal vessel and perforated plates (hepatocytes)
- blood channels 9-l2 µm wide, lined by endothelial cells
- Scattered in the glandular mass are blood vessels, alone and accompanied by other vessels.
- The distribution of these vessels defines or marks out the classic hepatic lobules
3 types of liver vessel
- central / terminal hepatic venule
- sublobular/ intercalated veins
- branch of portal vein
central vein/ terminal hepatic venule
- very thin wall
- lies in the centre of a lobule
- with sinusoids converging towards and opening into it
sublobular/ intercalated veins
- thicker wall
- lies alone at the periphery of the lobule
branch of portal vein
- at the periphery of the lobule
- accompanied by one or more small hepatic artery
- one or more bile ducts lined by cuboidal epithelium and lymphatics
portal triad
- portal vein + artery + bile duct
- the area in which they lie is a portal area
hepatic vein
- all the lobules stuck together forming a big central vein
bile duct
the portal vein and hepatic artery
go from liver to small intestine
moving bile from liver where it helps to digest food
liver acinus
the smallest functional group of the liver
- rappaport’s liver acinus represent’s a functional unit comprising parts of three or so lobules
- tries to explain the diff. in exposures to the blood supply among various parts of lobules
territory of an acinus
one final branch of the portal vein as its axis
subdivided into…
- periportal
- intermediate
- perivenous (close to central vein) zones
liver sinusoids
low pressure vascular channels that receive blood from the portal triad
- lined by fenestrated epithelial cells (loosely attached)
- phagocytic KUPFFER cells (immune cells)
- these phagocytose intruders + signal other cells to come help
space of Disse
between sinusoid and hepatocytes
- contains blood plasma
- allow protein and other blood plasma components to enter hepatocytes form sinusoids
- contain STELLATE CELLS
stellate cells
- sit just outside the endothelial cells
- store vit. A
- when activated they produce collagen
- first pathophysiological event that underlies liver cirrhosis
sinusoidal wall provides…
- blood cleansing
- haemopoeisis in the embryo
- bringing plasma into intimate contact with the hepatic cell for its many metabolic functions
metabolic functions of hepatic cells
storage synthesis, reg. of plasma conc. detox. production of bile assisting defence by producing acute-phase proteins
hepatocytes
- main functional cell of liver
- space hepatocytes arrange that anastomose with one another
- cells are polygonal shape
- sites in contact with sinusoids or neighbouring hepatocytes called the lateral faces
- lateral spaces is where bile is formed
- > called BILE CANALICULI
- microvili on sinusoidal faec (inc. surface area to inc. exchange of nutrients)
- also in bile canaiculi
- hepatocyte nuclei are distinctively round
what happens when liver gets inflamed
- lots of inflammatory cells in sinusoids
- kupffer cells activated
- stellate cells activated and produce collagen
- fenestrations start to close up
- sinusoidal pressure inc.
- first step in cirrhosis and portal hypertension
AS THINGS GET WORSE MANY HEPATOCYTES DIE
areas that die are replaced with fibrous tissue
irregular pattern of liver architecture in liver damage
o the portal triads expand and bridge
o extensive collagen deposition
o nodule formation
o hepatocytes are surrounding by closed gates and collagen
o this stage is called established liver cirrhosis
bile pathway
- blood flows from portal triad to central vein
- bile flows in opp. direction…
o as bile produced in hepatocytes – they communicate and create a bile duct
o therefore, bile duct formed by several bile canaliculi together
o they end up in a bigger bile duct within the portal triad
o bile ducts get bigger and bigger
o -> common hepatic duct -> common bile duct -> ampulla (areas called sphincter of Oddi) -> Duodenal outlet
o Following this route, the bile finds its way from the liver into the gut to facilitate digestion of food
where are liver stem cells
Canal of Hering/ cholangioles
liver lymphatic system
- Drainage system of the liver
- Lymph is formed by filtration of plasma into the spaces of Disse as blood flows through the sinusoids
o What doesn’t come back through sinusoids goes into the lymph - Small lymphatics percolate through space of Disse and portal tracts
- Run along portal vessels and biliary ducts
- Eventually lymph comes out and joins systemic circulation
