Chemical digestion in the small intestine cannot occur without the help of the liver and pancreas. The liver produces bile and delivers it to the common hepatic duct. Bile contains bile salts and phospholipids, which emulsify large lipid globules into tiny lipid droplets, a necessary step in lipid digestion and absorption. The gallbladder stores and concentrates bile, releasing it when it is needed by the small intestine.
The pancreas produces the enzyme- and bicarbonate-rich pancreatic juice and delivers it to the small intestine through ducts. Pancreatic juice buffers the acidic gastric juice in chyme, inactivates pepsin from the stomach, and enables the optimal functioning of digestive enzymes in the small intestine.
accessory duct
(also, duct of Santorini) duct that runs from the pancreas into the duodenum
acinus
cluster of glandular epithelial cells in the pancreas that secretes pancreatic juice in the pancreas
bile
alkaline solution produced by the liver and important for the emulsification of lipids
bile canaliculus
small duct between hepatocytes that collects bile
bilirubin
main bile pigment, which is responsible for the brown color of feces
central vein
vein that receives blood from hepatic sinusoids
common bile duct
structure formed by the union of the common hepatic duct and the gallbladder’s cystic duct
common hepatic duct
duct formed by the merger of the two hepatic ducts
cystic duct
duct through which bile drains and enters the gallbladder
enterohepatic circulation
recycling mechanism that conserves bile salts
enteropeptidase
intestinal brush-border enzyme that activates trypsinogen to trypsin
gallbladder
accessory digestive organ that stores and concentrates bile
hepatic artery
artery that supplies oxygenated blood to the liver
hepatic lobule
hexagonal-shaped structure composed of hepatocytes that radiate outward from a central vein
hepatic portal vein
vein that supplies deoxygenated nutrient-rich blood to the liver
hepatic sinusoid
blood capillaries between rows of hepatocytes that receive blood from the hepatic portal vein and the branches of the hepatic artery
hepatic vein
vein that drains into the inferior vena cava
hepatocytes
major functional cells of the liver
liver
largest gland in the body whose main digestive function is the production of bile
pancreas
accessory digestive organ that secretes pancreatic juice
pancreatic juice
secretion of the pancreas containing digestive enzymes and bicarbonate
porta hepatis
“gateway to the liver” where the hepatic artery and hepatic portal vein enter the liver
portal triad
bile duct, hepatic artery branch, and hepatic portal vein branch
reticuloendothelial cell
(also, Kupffer cell) phagocyte in hepatic sinusoids that filters out material from venous blood from the alimentary canal
Watch this video to see the structure of the liver and how this structure supports the functions of the liver, including the processing of nutrients, toxins, and wastes. At rest, about 1500 mL of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?
Answers may vary.
1. Which of these statements about bile is true?
A) About 500 mL is secreted daily.
B) Its main function is the denaturation of proteins.
C) It is synthesized in the gallbladder.
D) Bile salts are recycled.
D
2. Pancreatic juice ________.
A) deactivates bile.
B) is secreted by pancreatic islet cells.
C) buffers chyme.
D) is released into the cystic duct.
C
1. Why does the pancreas secrete some enzymes in their inactive forms, and where are these enzymes activated?
The pancreas secretes protein-digesting enzymes in their inactive forms. If secreted in their active forms, they would self-digest the pancreas. These enzymes are activated in the duodenum.
2. Describe the location of hepatocytes in the liver and how this arrangement enhances their function.
The hepatocytes are the main cell type of the liver. They process, store, and release nutrients into the blood. Radiating out from the central vein, they are tightly packed around the hepatic sinusoids, allowing the hepatocytes easy access to the blood flowing through the sinusoids.