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Biology 12
9.2 Accessory Organs of Digestion
The accessory digestive organs are the pancreas, liver, and gall bladder.
The Pancreas
The pancreas is an organ that has both endocrine and exocrine functions.
• Exocrine function of the pancreas
o Pancreatic cells produce
pancreatic juice (to neutralize
stomach acid) and digestive
enzymes
• Endocrine function of the pancreas
o Pancreas secretes insulin and
glucagon, hormones that
regulate blood glucose (sugar)
levels
Structure and Function of the Pancreas
The pancreas contains pancreatic islets (islets of Langerhans), which are clusters of at least
three types of endocrine cells:
• Alpha cells: produce glucagon
• Beta cells: produce insulin
• Delta cells: produce somatostatin
Insulin
• Hormone secreted when blood glucose
level is high
• Stimulates the uptake of glucose by cells
(liver, muscle, adipose tissue) to lower
blood glucose
Glucagon
• Hormone secreted when blood glucose
level is low
• Stimulates the liver to break glycogen
down into glucose to increase blood
glucose
• Stimulates adipose tissue to break fat
down to glycerol and fatty acids (to make
glucose)
Biology 12
Somatostatin
• A growth-hormone-inhibiting hormone
• Also produced by cells in the stomach and small intestine
• Inhibits the release of growth hormone
• Suppresses the release of insulin and glucagon
• Decreases the absorption of nutrients
The Liver
The liver is the largest gland in the body.
The liver has many functions, including:
• Detoxifying blood
• Making plasma proteins
• Maintaining blood glucose levels
• Producing bile, which contains bile salts that
emulsify fat in the small intestine
• Producing urea, a nitrogenous waste product from the breakdown of amino acids
Structure and Function of the Liver
The liver contains about 100 000 lobules that serve as its structural and functional units.
Three structures are located between the lobules:
• Bile duct: takes bile away from the liver
• Hepatic artery branch: brings oxygen-rich blood to the liver
• Hepatic portal vein: transports nutrients from the intestines
• The liver contains about 100 000 lobules that serve as its structural and functional units.
• Three structures are located between the lobules:
• Bile duct: takes bile away from the liver
• Hepatic artery branch: brings oxygen-rich blood to the liver
• Hepatic portal vein: transports nutrients from the intestines
Figure 9.8: A hepatic lobule
Biology 12
Figure 9.10 Hepatic portal system. The hepatic portal vein takes the products of digestion from the
digestive system to the liver, where they are processed before entering a hepatic vein.
The Gall Bladder
The gall bladder is a muscular sac attached to the surface of the
liver.
• Excess bile from the liver is stored in the gall bladder
• Bile leaves the gall bladder and proceeds to the duodenum
via the common bile duct
o Bile emulsifies fat to prepare it for further
breakdown by digestive enzymes