Download Document

UNIT B: Human Body Systems
Chapter 8: Human Organization
Chapter 9: Digestive System: Section 9.2
Chapter 10: Circulatory System and
Lymphatic System
Chapter 11: Respiratory System
Chapter 12: Nervous System
Chapter 13: Urinary System
Chapter 14: Reproductive System
UNIT B Chapter 9: Digestive System
Chapter 9: Digestive System
In this chapter, you will learn
about the structure and function
of the digestive system.
What is our current understanding
of the structure and function of the
digestive system, including the
stomach?
Alexis St. Martin was an unexpected live test subject
for Dr. William Beaumont’s research on how the
digestive system works.
TO PREVIOUS
SLIDE
Which substances produced by the
stomach and other organs help with
the chemical breakdown of foods?
UNIT B Chapter 9: Digestive System
Section 9.2
9.2 Accessory Organs of Digestion
The accessory digestive organs are the pancreas, liver, and
gall bladder.
Figure 9.8 Liver, gall
bladder, and pancreas. a.
The liver makes bile, which
is stored in the gall bladder
and sent (black arrow) to
the small intestine by way
of the common bile duct.
The pancreas produces
digestive enzymes that are
sent (black arrows) to the
small intestine by way of
the pancreatic duct.
TO PREVIOUS
SLIDE
UNIT B Chapter 9: Digestive System
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
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
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
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
Section 9.2
Structure and Function of the Pancreas
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)
TO PREVIOUS
SLIDE
UNIT B Chapter 9: Digestive System
Structure and Function of the Pancreas
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
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
Figure 9.9 Regulation of
blood glucose level. Top:
When the blood glucose
level is high, the pancreas
secretes insulin. Insulin
promotes the storage of
glucose as glycogen and
the synthesis of proteins
and fats (as opposed to
their use as energy
sources). Therefore,
insulin lowers the blood
glucose level to normal.
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
Bottom: When the blood
glucose level is low, the
pancreas secretes
glucagon. Glucagon acts
opposite to insulin.
Therefore, glucagon raises
the blood glucose level to
normal.
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
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
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
Section 9.2
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
TO PREVIOUS
SLIDE
UNIT B Chapter 9: Digestive System
Section 9.2
Figure 9.8 b. A hepatic lobule. The liver contains over 100 000 lobules, each lobule
composed of many cells that perform the various functions of the liver. They remove and
add materials to the blood and deposit bile in a duct.
TO PREVIOUS
SLIDE
UNIT B Chapter 9: Digestive System
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.
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
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
TO PREVIOUS
SLIDE
Section 9.2
UNIT B Chapter 9: Digestive System
Section 9.2
Check Your Progress
1. Describe how pancreatic hormones regulate blood
glucose levels.
2. Explain why the liver is necessary for life, whereas the
gall bladder can be removed with few consequences.
TO PREVIOUS
SLIDE
UNIT B Chapter 9: Digestive System
TO PREVIOUS
SLIDE
Section 9.2