Download The Liver

The Liver
WALT
• The structure of the liver
• The many functions of the liver
• The blood supply to and from the liver
Hepatocytes- liver cells
• Hepatocytes are metabolic superachievers
in the body.
• They play critical roles in synthesizing
molecules that are utilized elsewhere to
support homeostasis, in converting
molecules of one type to another, and in
regulating energy balances.
The liver plays a key role in glucose homeostasis:
i) glycogenolysis: breakdown of glycogen
ii)gluconeogenesis:converting proteins into glucose
iii)glycogenesis: converting glucose into glycogen
The Liver – is an organ for digestion and
homeostasis
Blood system associated with the liver
Blood Supply to the liver
Blood is drained into the liver by 2 vessels:
the hepatic artery and
the hepatic portal vein
Blood is drained away from the liver by
the hepatic vein
Functions of The Liver
The liver has about 500 individual functions.
They are grouped as below:
1.Carbohydrate metabolism
- action of insulin & glucagon
2.Lipid metabolism
- lipids are broken down or transported to storage
areas
- excess carbohydrates  lipid
- regulate cholesterol level; atherosclerosis & gall
stones
3. Protein metabolism
deamination and transamination to synthesize
non-essential amino acids
4. Synthesis of plasma proteins,
e.g. clotting factors: prothrombin & fibrinogen
5.Production of bile:
bilirubin + bile salts + NaCl + HCO36.Storage of vitamins,
especially fat soluble vitamins A, D, E, K
7.Storage of minerals
e.g. Fe, K, Cu & Zn
8. Formation & breakdown of RBCs
foetal liver produces RBCs
adult liver breaks down aged RBCs
9. Storage of blood
about 1500 cm3 of blood can be stored
10.Hormone breakdown
e.g. testosterone, insulin etc
11.Detoxification
Kupffer cells ingest foreign materials
Hepatocytes convert toxic chemicals into
harmless forms
12. Production of heat
when body temperature falls triggered by the
hypothalamus
Making Bile
• Bilirubin is a useless and toxic breakdown
product of hemoglobin, which also means
that it is generated in large quantities.
Jaundice
• If excessive quantities of bilirubin
accumulate in extracellular fluid, a yellow
discoloration of the skin, sclera and
mucous membranes is observed - this
condition is called icterus or jaundice.
Protein Metabolism
• The human body cannot store proteins
• Amino acids like many other digested
foods reach the liver via the hepatic portal
vein
Protein Metabolism
• The most critical aspects of protein
metabolism that occur in the liver are:
• Deamination and transamination of amino
acids, followed by conversion of the nonnitrogenous part of those molecules to
glucose or lipids.
Protein Metabolism 2
• Removal of ammonia from the body by
synthesis of urea.
• Ammonia is very toxic and if not rapidly
and efficiently removed from the
circulation, will result in central nervous
system disease.