Accessory Organs
Pancreas, Liver and Gallbladder
Pancreas
• Secretes pancreatic juice
into pancreatic duct then to
the duodenum
• Function: contains 4
classes of enzymes to break
down substances.
• Location: posterior to
stomach; left side
Pancreatic Juice
• Pancreatic amylase
– splits starch and glycogen into disaccharides
• Pancreatic lipase
– splits triglycerides into fatty acids and
monoglycerides
• Proteinases (Trypsin, chymotrypsin,
carboxypeptidase)
– Breaks up peptide bonds
• Nucleases
– split nucleic acid molecules
Pancreatic Juice
• Bicarbonate ions make pancreatic juice
alkaline to neutralize acidic chyme
Pancreatic Secretion Regulation
• During cephalic and gastric digestive phases
parasympathetic impulses stimulate pancreatic
secretion.
• Secretin: hormone
– causes release of pancreatic juice into duodenum
– stimulates a bicarbonate-rich fluid.
– Activated by the duodenum filling up with chyme
Figure 17.25
Pancreatitis
• Inflammation of pancreas
• Caused by activation of enzymes in the
pancreas gland
– Trypsinogen------trypson
Liver
• Largest internal organ
• 2 lobed structure
– Large right and small
left
• Each lobe is made up
of Hepatic lobules:
function unit of the
liver
Figure 17.28
Liver
• Lobes are divided into
hepatic lobules
– hepatic cells around a
central vein
– hepatic sinusoids lead to
the hepatic portal vein
– Kupffer cells remove
bacteria by phagocytosis
– bile canals lead to
hepatic ducts which
merge at the common Figure
bile duct
17.29
Liver Functions
1. Metabolism:
• Carbohydrate metabolism
– stores glycogen, regulates blood glucose levels
• Lipid metabolism
– synthesizes lipoproteins, regulates lipid
metabolism
• **Protein metabolism
– deamination of amino acids, forming urea
– transamination of amino acids
– synthesis of plasma proteins
• (clotting proteins)
Liver Functions
2. Stores minerals and vitamins
– iron is stored as ferritin, Vit A, B 12 and glycogen
3. Detoxification of substances, including alcohol
4. Destruction of damaged red blood cells
5. Phagocytosis of foreign antigens
– Contain Kupffer’s cells
• Remove and destroy microbes, foreign matter and worm
platelets and erythrocytes
6. Serves as a bile reservoir and Secretion of bile
7. Blood reservoir
Bile Composition
Yellowish-green fluid secreted by hepatic cells
• Contains water (90%), cholesterol, and
electrolytes
• Contains bile salts*
– Emulsify (break down) fats
– Makes cholesterol
• Contains bile pigments
– bilirubin, biliverdin
– breakdown products of hemoglobin
Figure 17.30
Jaundice
• Abnormal Skin pigmentation
• Excess bilirubin in the blood.
(Bilirubin is produced by the
normal breakdown of red blood
cells. Normally bilirubin passes
through the liver and is excreted
as bile through the intestines)i
• Jaundice occurs when bilirubin
builds up faster than the liver
can break it down and pass it
from the body.
Liver Diseases
• Cirrhosis
• Jaundice
Gallbladder
• Bile is produced
by the liver and
concentrated in
the gall bladder.
• Stores bile
between meals
Figure 17.32
Gallbladder
CCK
• Cholecystokinin:
released in response to
proteins and fats in the
small intestine,
stimulates gall bladder
contraction.
• Bile leaves through the
cystic duct to the
common bile duct and is
squirted into the
duodenum of the small
intestine.
Function of Bile Salts
• Bile salts enhance absorption of fatty acids and
fat-soluble vitamins.
• Bile salts reduce surface tension and break fat into
small droplets (emulsification).
• Emulsification increases surface area so lipases
can more easily digest fats.
• The intestinal mucosa reabsorbs nearly all of the
bile salts.
Blocked cystict duct
cholecystitis
Small Intestine
• Extends from the pyloric
sphincter to the large
intestine
• Three portions: duodenum,
jejunum, ileum
• Receives secretions from
the pancreas and the liver
• Complete digestion of
nutrients in chyme, absorbs
products of digestion,
Figure 17.33
transports residue to the
large intestine
Figure 17.33
Small Intestine
• Double-layered folds of peritoneum
– mesentery: supports intestinal nerves, blood and
lymphatic vessels
– greater omentum: drapes over the intestine
• Inner intestinal wall has many tiny
projections, the intestinal villi. Each
contains blood vessels, nerves and a lacteal
• Intestinal glands extend into the mucosa
• Circular folds of the mucosa, plicae
circulares, increase surface area
Figure 17.35
Figure 17.36
Figure 17.37
Small Intestine Secretions
• Mucus is secreted by goblet cells and glands
in the submucosa
• Intestinal mucosa have digestive enzymes
on their luminal surfaces
– peptidases: split peptides into amino acids
– sucrase, maltase, lactase: split disaccharides
into monosaccharides
– intestinal lipase: splits fats into fatty acids and
glycerol