Transcript Unit One: Introduction to Physiology: The Cell and General

Chapter 70: The Liver as an Organ
Guyton and Hall, Textbook of Medical Physiology, 12th edition
Basic Properties
• Physiologic Anatomy of the Liver
a. Largest organ of the body, contributes about 2% of the
total body weight
b. Functional unit is the liver lobule; liver contains
50,000-100,000 individual lobules
Basic Properties
• Physiologic Anatomy of the Liver
Fig. 70.1 Basic structure of a liver lobule
Basic Properties
• Hepatic Vascular and Lymph Systems
a. Blood flows through the liver from the portal vein
and hepatic artery
b. Liver has high blood flow and little vascular
resistance
c. Liver functions as a blood reservoir
d. Liver has high lymph flow
Basic Properties
• Regulation of Liver Mass-Regeneration
a. The liver can restore itself after significant hepatic
tissue loss
b. Control mechanisms are largely unknown but may
be regulated by hepatocyte growth factor (HGF)
c. Once the liver has returned to its normal size,
growth is inhibited, possibly by cytokines
(i.e. transformng growth factor-beta)
Basic Properties
• Hepatic Macrophage System Serves a Blood
Cleansing Function
a. Kupffer cells- large phagocytic macrophages that
line the hepatic venous sinuses
b. Removes approximately 99% of the bacteria
entering the portal blood from the intestinal
tract
Basic Properties
• Metabolic Functions of the Liver
a. Carbohydrate metabolism
1)
2)
3)
4)
5)
storage of large amounts of glycogen
conversion of galactose and fructose to glucose
gluconeogenesis
formation of many chemical compounds from
intermediate products of cbh metabolism
important for maintaining a normal blood
glucose concentration
Basic Properties
• Metabolic Functions of the Liver
b. Fat metabolism
1)
oxidation of fatty acids to supply energy
for other body functions
2)
synthesis of large quantities of cholesterol,
phopholipids, and most lipoproteins
3)
synthesis of fat from proteins and cbhs
Basic Properties
• Metabolic Functions of the Liver
c. Protein metabolism
1)
deamination of amino acids
2)
formation of urea for removal of ammonia
from the body fluids
3)
formation of plasma proteins
4)
Interconversions of the various amino acids
and synthesis of other compounds from
amino acids
Basic Properties
• Metabolic Functions of the Liver
d. Other metabolic functions
1)
storage site for vitamins
2)
stores iron as ferritin
3)
forms the blood substances used in coagulation
4)
removes or excretes drugs, hormones, and
other substances