The liver

Liver, gallbladder, and pancreas are accessory organs associated

with small intestine

Liver-

digestive function is production of bile

Bile -

fat emulsifier

Gallbladder-

chief function is storage of bile

Pancreas -

supplies most of enzymes needed to digest chyme, as well as bicarbonate to neutralize stomach acid

The liver is the largest gland in the body, weighing -

~3 lbs

Consists of four primary lobes:

right, left, caudate, and quadrate

Falciform ligament -

• Separates larger right and smaller left lobes 

• Suspends liver from diaphragm and anterior abdominal wall

Round ligament (ligamentum teres) -

Remnant of fetal umbilical vein along free edge of falciform ligament

Lesser omentum anchors liver to

stomach

Hepatic artery and vein enter liver at

porta hepatis

Bile ducts

• Common hepatic duct leaves liver

• Cystic duct connects to gallbladder

• Bile duct formed by union of common hepatic and cystic ducts

Liver lobules -

• Hexagonal structural and functional units

  • Composed of plates of hepatocytes (liver cells) that filter and process nutrient-rich blood 

Liver lobules -

Central vein

located in longitudinal axis

Liver lobules -

• Portal triad

in each corner of lobule contains:

• Branch of hepatic artery, which supplies oxygen

• Branch of hepatic portal vein, which brings nutrient-rich blood from intestine

Liver lobules -

• Bile duct

, which receives bile from bile canaliculi

• Liver sinusoids:

leaky capillaries located between hepatic plates

• Blood from both hepatic portal vein and hepatic artery proper percolates from triad regions through sinusoids and empties into central vein

Stellate macrophages (hepatic macrophages) -

in liver sinusoids remove debris and old RBCs

Hepatocytes

• have increased rough and smooth ER, Golgi apparatus, peroxisomes, and mitochondria

Hepatocyte functions

• Produce ~900 ml bile per day

• Process bloodborne nutrients

  • Example: store glucose as glycogen and make plasma proteins

• Store fat-soluble vitamins

• Perform detoxification

  • Example: converting ammonia to urea

Bile -

• Yellow-green, alkaline solution containing bile salts and bilirubin

Bile salts -

cholesterol derivatives that function in fat emulsification and absorption

Bilirubin -

• pigment formed from heme

  • Bacteria break down in intestine to stercobilin that gives brown color of feces 

• Cholesterol, triglycerides, phospholipids, and electrolytes

Bile: Enterohepatic circulation

Recycling mechanism that conserves bile salts

Bile salts are -

• Reabsorbed into blood by ileum (the last part of small intestine)

• Returned to liver via hepatic portal blood

• Resecreted in newly formed bile

• About 95% of secreted bile salts are recycled, so only 5% is newly synthesized each time