2. • Largest internal organ.
• Comprised of hexagonally shaped functional units called hepatic
lobules separated to each other by a septum.
THE LIVER OVERVIEW
• Liver cells comprising these lobules are called hepatocytes.
• Although the digestive function of the liver is only to produce
bile, it is also involved in many metabolic and regulatory roles.
3. THE LIVER STRUCTURE
HEPATIC LOBULE
• Hepatocyte form hepatic plates that
radiate outward from a central vein
running in the longitudinal axis of the
lobule.
• Sinusoids form the space in between
hepatic plates
• Bile canaliculi collects the bile
produced by hepatocytes and drains into
the bile duct.
Portal triad:
• Branch of Hepatic Artery
• Supply oxygen-rich arterial blood
to the liver
• Branch of Hepatic Portal Vein
• Carry blood laden with nutrients
from the digestive viscera (3/4
deoxygenated)
• Bile Duct
5. Actions
Digestive
Synthesis of bile salts
Conjugation and excretion of bile pigment(bilirubin).
Metabolic
and Synthetic
Glucose Metabolism (regulation of blood sugar)
- Conversion of blood glucose to glycogen and fat.
- Production of glucose from glycogen and other molecules by gluconeogenesis
- Secretion of glucose into blood
Fat Metabolism
- Synthesis of triglycerides and cholesterol, excretion of cholesterol in bile, and
production of ketone bodies from fatty acids.
Protein Metabolism
- Production of albumin, plasma transport proteins, clotting factors (fibrinogen,
prothrombin, and others)
Detoxification
Phagocytosis by Kupffer cells
Chemical alteration of biologically active molecules (hormones and drugs)
Production of urea, uric acid and other compounds that are less toxic than the parent
compound.
THE LIVER FUNCTIONS
6. THE LIVER
DIGESTIVE
FUNCTION
- Production of bile
- Yellow-green alkaline solution containing bile salts, bile pigment,
cholesterol, triglycerides, phospholipids, and a variety of electrolytes.
- Bile salts (cholic and chenodeoxycholic acid) emulsify fats.
- Break them down into smaller pieces and distribute them throughout
the intestine to facilitate fat digestion and absorption.
- Only bile salts are recycled (through the enterohepatic circulation.)
(1) reabsorbed into the blood by the ileum,
(2) returned to the liver via the hepatic portal blood,
and then
(3) resecreted in newly formed bile.
7. THE LIVER
DIGESTIVE
FUNCTION
- Production of bile
- Bilirubin is the chief pigment in bile.
- Waste product of the heme of the hemoglobin formed during the
breakdown of worn-out erythrocytes.(by Kupffer cells)
(hemoglobin = heme + globin + iron)
*Over production,
impaired transportation,
blocked excretion, and
over re-absorption of
bilirubin in the intestine
may result in Jaundice.
8. THE LIVER
• Contents of blood coming from the portal veins are
monitored by the hepatocytes in the liver and
potentially toxic substances are removed from it.
– Organic substances such as alcohol and drugs are
metabolized into their inactive form.
– Hormones are metabolized and removed to keep within
homeostatic level.
– Converts ammonia to urea as part of urea cycle.
– Excreted through bile.
DETOXIFICATION
9. THE LIVER
GLUCOSE, LIPID,
PROTEIN METABOLISM
• Carbohydrate metabolism
– Glucose converted to glycogen/fat
(glycogenesis/lipogenesis)
– Glucose produced from glycogen(gluconeogenesis)
• Lipid metabolism
– Synthesis and release of lipid
– Decomposition of fatty acid
– Synthesis and transport of cholesterol
• Protein
– Albumin and most of the plasma globulins (except
immunoglobulins) are produced by the liver.
10. GALL
BLADDER
FUNCTION
• Thin-walled green muscular
sac about 10 cm long, about
the size of a kiwi fruit.
• Stores bile that is not
immediately needed for
digestion.
• When gall bladder fills with bile, it
expands.
– Contraction of muscularis layer
ejects bile into the common
bile duct.
• When small intestine is empty,
sphincter of Oddi closes.
*Gallstones are cholesterol that have
crystallized within the gall bladder.
11. PANCREAS STRUCTURE
• Soft, tadpole-shaped gland
that extends along the
abdomen and encircled by the
C-shaped duodenum.
• Has endocrine and exocrine
component:
– Exocrine
• Acini cells are raspberry
like clusters surrounding
tiny ducts responsible for
secreting digestive enzymes
– Endocrine
• Pacreatic islets responsible
for glucose metabolism.
12. PANCREAS PANCREATIC JUICE
- Contains H20, HC03
- and digestive
enzymes.
- HC03
- neutralizes the acidic chyme
entering the duodenum and provides an
optimal environment for pancreatic
enzymes.
- Most pancreatic enzymes are produced
as zymogens, which are inactivated
form of the digestive enzymes.
13. PANCREAS PANCREATIC JUICE
• Trypsin, chymotrypsin, elastase, carboxypeptidase and phopholipase
are released in their zymogenic form when released in the duodenum.
14. PANCREAS PANCREATIC JUICE
• Trypsinogen when activated by the enterokinase in the lining of the
duodenum is converted to Trypsin.
• Trypsin triggers the activation of other pancreatic enzymes
(chymotrypsin, elastase, carboxypeptidase and phopholipase)
Notes de l'éditeur
At the center of a lobule is a central vein where all blood is drained out from the liver.
Basically the flow of blood is from the edges toward the center.
We have 4 main vessels and ducts that are connected to the liver
The figure illustrates the flow of bile salts.
Over production, impaired transportation, blocked excretion, and over re-absorption in the intestine may result in jaundice.
This is a major reason why not all pharmaceutical agents can achieve therapeutic concentrations in the bloodstream if administered orally*
Bile is the major vehicle for excreting cholesterol from the body,
and bile salts keep the cholesterol dissolved within bile. Too much
cholesterol or too few bile salts allows the cholesterol to crystallize,
forming gallstones or biliary calculi
