Chapter 24

6 – The Pancreas, Liver & Gallbladder

The Pancreas

• The pancreas is a soft, oblong organ connected by ducts to the duodenum; it is both an exocrine gland (secreting pancreatic juice) and an endocrine gland (secreting insulin & glucagon.

The Pancreas

• The pancreas is made up of two types of glandular epithelial cells:

1. Acini cells

2. Pancreatic islets

The Pancreas

1. Acini cells make up 99% of the pancreatic cells; they are exocrine cells that secrete a mixture of fluid called pancreatic juice.

The Pancreas

– The acini cells of the pancreas secrete pancreatic juices into ducts that empty into the small intestine.

The Pancreas

• Pancreatic juice is a clear colorless liquid consisting of mostly water, some salts, sodium bicarbonate and several enzymes.

The Pancreas

• **The sodium bicarbonate gives pancreatic juice a slightly alkaline ph (7.1 – 8.2) that buffers acidic gastric juice in chyme, stops the action of pepsin from the stomach, and creates the proper pH for the action of digestive enzymes in the small intestine.

The Pancreas

• **The enzymes in pancreatic juice include: the starch digesting enzyme (pancreatic amylase), several protein digesting enzymes including (trypsin), the principal triglyceride digesting enzyme (pancreatic lipase), and nucleic acid digesting enzymes.

The Pancreas

2. Pancreatic islets (islets of Langerhans) make up the remaining 1% of pancreatic cells; they are endocrine cells that secrete the hormones insulin and glucagon.

The Pancreas

• The two primary types of pancreatic islets are:

I. Alpha cells

II. Beta cells

The Pancreas

I. Alpha cells are pancreatic islets that secrete the hormone glucagon – increases blood glucose level when it falls below normal.

The Pancreas

II. Beta cells are pancreatic islets that secrete the hormone insulin – decreases blood glucose level when it is too high.

The Liver

• The liver is the large organ located under the diaphragm that performs many vital functions; the principle digestive functions of the liver are to produce & secrete bile.

The Liver

– The liver is divided into two lobes that are made of functional units called lobules (a six sided structure) that consists of hepatocytes.

The Liver

• Heapatocytes are liver cells that produce bile.

The Liver

• Bile is a yellowish, brownish or olive-green secretion of the liver that emulsifies lipids prior to their digestion.

The Liver

• Emulsification is the dispersion of large lipid globules into smaller, uniformly distributed particles in the presence of bile.

The Liver

– The small lipid globules produced by emulsification present a very large surface area that allows pancreatic lipase to more rapidly accomplish digestion of triglycerides.

The Liver

• In addition to synthesizing and secreting bile, the liver performs the following functions:

– Carbohydrate metabolism

– Lipid metabolism

– Protein metabolism

– Processing drugs

The Liver

• Liver functions cont’:

– Excretion of bilirubin

– Storage

– Phagocytosis

– Activation of vitamin D

The Gallbladder

• The gallbladder is a small pouch, located inferior to the liver, that stores bile and empties by means of the cystic duct.

Homework

• Finish handout:

– “The pancreas, Liver & Gallbladder”

• Study for mini-quiz