The Digestive System …cont’d
Monday, January 18th, 2010
Today’s Targets!
• major functions of liver
• role of bile
• role of sodium bicarbonate in
pancreatic juice
• importance of pH in various
regions of the digestive tract
• the pancreas as the source
gland for insulin
• function of insulin in
maintaining blood sugar
levels
Digestion Overview
Animation:
• http://www.argosymedical.com/flash/digestio
n/landing.html
The Pancreas
• Location: just below and parallel with stomach
• Size: ~ 10-15 cm long x 1-3 cm wide (tapering)
x ~1-2 cm thick
Fig. 41.12
The Pancreas
• Connections:
connects to the small intestine through the
pancreatic and common ducts
The Pancreas
• Structure: two types of tissues:
1. produces and secretes digestive juices which
goes through pancreatic duct to SI
2. Islets of Langerhans produces and secretes
insulin (from beta cells) and glucagon into
blood (from alpha cells)
The Pancreas
Exocrine Functions:
• a) produces bicarbonate ions (HCO3-)
 neutralize stomach acids
 makes pH of intestine alkaline (7-8)
**Sm. Intestine enzymes optimum at basic pH**
• b) produces digestive enzymes
 amylases, peptidases, lipases and nucleases
**All products released through pancreatic duct to SI**
The Pancreas
Endocrine Functions:
• c) produces insulin
 controls cellular uptake of glucose and its
conversion into glycogen (insulin secreted when high
glucose level in blood)
• d) produces glucagon
 stimulates the conversion of glycogen into glucose
(glucogon secreted when low glucose levels detected
in blood)
• Glucose is a major fuel for cells
• Its metabolism, regulated by hormone action, is an
important example of homeostasis
1 When blood glucose
level rises, a gland called
the pancreas secretes insulin,
a hormone, into the blood.
2 Insulin enhances the
transport of glucose into body
cells and stimulates the liver
and muscle cells to store
glucose as glycogen. As a
result, blood glucose level
drops.
STIMULUS:
Blood glucose
level rises
after eating.
Homeostasis:
90 mg glucose/
100 mL blood
4
Glucagon promotes
the breakdown of
glycogen in the
liver and the
release of glucose
into the blood,
increasing blood
glucose level.
Figure 41.3
STIMULUS:
Blood glucose
level drops
below set point.
3 When blood glucose
level drops, the pancreas
secretes the hormone
glucagon, which opposes
the effect of insulin.
Animation
Blood Sugar Regulation in Diabetics
• http://highered.mcgrawhill.com/classware/ala.do?isbn=0072956208&
alaid=ala_996424&showSelfStudyTree=true
Release of Pancreatic Juice
Control: When acid chyme arrives in the duodenum,
the duodenal wall releases the hormones secretin
and CCK (cholecystokinin). The hormones travel
through the blood to the pancreas where they
stimulate the production of pancreatic juice.
• Secretin made in response to presence of acid
• CCK made in response to presence of proteins and
fats
Supplementary Materials
• Article: Diabetes epidemic
http://www.sciencentral.com/articles/view.php3?language=english&type
=&article_id=218392748
• Article: Is Alzheimer’s diabetes
http://www.sciencentral.com/articles/view.php3?language=english&type
=&article_id=218393025
• Song: Weird Al Pancreas
• http://www.youtube.com/watch?v=BtsQxUYHXbw&feature=related
• Animation: Diabetes Type II
www.healthscout.com/animation/68/34/main.html
The Liver
• Location: Under the ribs but below the diaphragm on
the right side of the body
• Size: it is roughly triangular, lobed, about 1.5 kg
The Liver
• Connections: all blood from
intestines arrives at the liver
via the Hepatic Portal Vein
(the only blood vessel in the
body which goes from a
capillary bed -the intestinesto another capillary bed -the
liver- without going back to
the heart)
Functions of the Liver
• Over 500 functions!
• a) Produces bile that emulsifies fats (breaks into
small droplets with a large surface area for
pancreatic lipase to work on)
 bile stored in gall bladder
 bile production up to 1.5 L/day
 bile is green because contains
pigments of hemoglobin breakdown from liver
Functions of the Liver
• b) Converts glucose to glycogen after a meal (and
back to glucose in the hours inbetween meals)
 this maintains blood sugar levels under the
control of pancreatic hormones
• c) Converts hemoglobin from old red blood cells into
bilirubin or biliverdin, pigments which give bile its
colour
Functions of the Liver
• d) Deaminates amino acids (from proteins in the diet,
from the recycling of worn-out body proteins, or
from muscle breakdown in starvation conditions)
 amino group converted to urea & excreted
through kidneys - remainder of amino acid
metabolized for energy
• e) Produces blood proteins such as albumin
(regulates osmotic balance of blood) and
fibrinogen (aids in blood clotting)
Functions of the Liver
• f) Breaks down and detoxifies substances including:
hormones circulating in the blood, alcohol, some
antibiotics, many drugs, and toxins found in some
foods
• g) Stores iron and vitamins
• h) Makes cholesterol
Article: Liver on a Chip
• http://www.sciencentral.com/articles/view.ph
p3?language=english&type=&article_id=2183
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