Lecture 11 - Liver Structure and Function Flashcards
What is the largest organ in the body?
The liver at about 1.4Kg
Where is the liver located?
In the upper right quadrant of abdomen (tucked against inferior surface of diaphragm)
What are the lobes of the liver?
2 major lobes - right (largest) and left
2 minor lobes - caudate and quadrate lobes
What ligaments are present in the liver?
The falciform ligament separates the right and left lobes and attaches the liver to the anterior abdominal wall (remnant of ventral mesentery)
The round ligament of the liver (ligamentum teres) originates from the free edge of the falciform ligament (remnant of foetal umbilical vein)
The coronary ligament attaches the bare area of the liver to the inferior surface of the liver
What can be found in the centre of the liver?
The porta hepatis - an area where the portal triad can be found, i.e. the hepatic artery, portal vein and common hepatic duct enter and leave the liver
What other structures enter and leave the liver via the porta hepatis?
Blood vessels, lymphatic vessels, the hepatic nerve plexus
Describe where bile travels after it is produced in the liver
It travels from the hepatocytes (where its make) in the bile canaliculi into the right and left hepatic ducts which feed into the common hepatic duct
The common hepatic duct joins with the cystic duct of the gallbladder to form the common bile duct
The common bile duct then merges with the pancreatic duct, and enters through the major duodenal papilla into the duodenal lumen (release of bile into duodenum controlled by the sphincter of Oddi
What happens to the bile if the smooth muscle around the Sphincter of Oddi contracts?
Causes the sphincter of Oddi to close, bile backs up the common bile duct and enters the cystic duct to travel to the gallbladder
Bile is stored and concentrated in the gallbladder
What covers the liver?
Liver is covered by a connective tissue capsule (holds liver together) and visceral peritoneum (expect for bare area, which is surrounded by coronary ligament)
What surrounds the porta hepatis?
Connective tissue capsule
Describe what the liver looks like histologically
Branching network of septa into body of the liver, branching partitions (septa) give the liver structure and support Vessels, ducts and nerves follow septa throughout liver The septa divide the liver into hexagonal lobules (each corner of each hexagon has a portal triad) - central vein in the middle of each lobule Hepatic cords (composed of hepatocytes) radiate out from the central veins Bile canaliculus (cleft-like lumen) lie between cells within each cord - bile etc. secreted into here
What are the spaces in between the hepatic chords known as?
Hepatic sinusoids (blood channels) - discontinuous capillaries which allow movement of blood cells
What happens to the central veins of each hexagonal lobule?
They come together to form hepatic veins and eventually drain into the IVC
What are the brown cells that can be seen in the liver histology?
Hepatocytes which radiate out from the central vein
What are bile canaliculi?
Open channels that run from the middle of the hexagon that allow flow of secretions into the bile canaliculi which then come together to form the right and left hepatic ducts
Does the blood from the hepatic portal vein or the hepatic artery run towards the central vein or away from it?
Blood from the hepatic portal vein and the hepatic artery run towards the central vein
Why is it important that the sinusoids are discontinuous?
Blood coming from the gut is high in nutrients and we want to absorb these and filter any toxins etc.
Blood coming from the artery is high in oxygen, and the hepatic cells are aerobic and obviously need this
What is are the functions of hepatocytes?
Bile secretion - PRIMARY ROLE
Nutrient storage (glycogen, fat, vit (B12, A, D, E, K), Cu, Fe)
Nutrient interconversion
Detoxification
What are the six components of bile?
Bile acids Lecithin (emulsification agent) Cholesterol Bile pigments (bilirubin) Toxic metals are detoxified in the liver Bicarbonate (neutralisation of acid chyme) - stimulated by secretin
Bile acids, lecithin and cholesterol are synthesised in the liver by hepatocytes and solublise fat
Bile acids, lecithin, cholesterol, bile pigments and toxic metals are secreted by hepatocytes
Bicarbonate is secreted by duct cells
What forms bile pigments? What is the predominant bile pigment and where is it excreted?
Breakdown of Hb from old/damaged RBCs
Bilirubin (predominant bile pigment) - extracted from blood by hepatocytes s it passes through hepatic sinusoids and secreted in bile (produces yellow bile)
How does bilirubin affect the colour of our faeces and urine?
Bilirubin modified by bacterial enzymes to produce brown pigments (= brown stools_
Reabsorbed bilirubin excreted in urine (=yellow urine)
How much bile do we make a day? And how do we maintain a general bile salt pool?
General bile salt pool of about 5g - very efficiently recycled, only loose about 5g a day
