chapter 19 - homeostasis (part 2)
TRANSCRIPT
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HOMEOSTASIS
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19.3 Human Homeostatic Organs: liver and kidney
19.3.1 Structure and functions of
liver
TOPICS
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PREVIOUS LESSON
H OM EOSTATI C
CONTR OL
SYSTEM
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OBJECTIVES
At the end of this lesson, students should be able to:
1. Describe the structure of liver.
2. Explain its homeostatic function in terms of
carbohydrate metabolism, detoxification &
transamination & deamination of amino acids.
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19.3.1 Structure and
Function of liver
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19.3.1 Structure and
Function of liver
Largestinternalorgan
Composed of
numerous lobules Cylindrical in shape
1 mm in diameter
Hepatic vein
Hepatic portal vein
Bile duct
Hepatic artery
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19.3.1 Structure and
Function of liver
Each lobule is filled with
many vertical plates ofliver cells
Hepatocytes
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19.3.1 Structure and
Function of liver
Hepatocytes
Contains nuclei, Golgi
apparatus, many
mitochondria &lysosomes
Rich in glycogen granules
Tightly packed together
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19.3.1 Structure and
Function of liver
Running alongsideeach lobule arebranches of:
Hepatic artery Carries oxygenated
blood to the liver
Hepatic portal vein
Carries nutrient-richblood from theintestine to the liver
Interlobular
blood vessels
Located between
adjacent lobules
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19.3.1 Structure and
Function of liver
In the center of each
lobule is a branch of
the hepatic vein
Known as intralobularvein or central vein
Bring deoxygenated
blood out of the liver
Empties into the inferiorvena cava
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Bile duct
Bile is produced in the
hepatocyte and stored
in the gall bladder. The bile duct is a
small vessel
connecting the gall
bladder with the smallintestine
19.3.1 Structure and
Function of liver
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19.3.1 Structure and
Function of liver
Bile canaliculi
Take up bile produced in
hepatocytes to the bile
duct
Unites forming bile ducts
Flow parallel to the
sinusoids
Opposite direction that
blood flows
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19.3.1 Structure and
Function of liver
Production of bile:
Composed of:bilirubin
bile salts
Bilirubin
Formed from the breakdown
of haem in red blood cells
Bile salts Made from cholesterol
Function : emulsify fats
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Sinusoid
Is a type of interlobular
vessels are connected with
the central vein by a system
of blood channel
serves as a location for the
flow of oxygen-rich blood
from the hepatic artery and
the nutrient-rich blood from
the hepatic portal vein
to the central vein
Sinusoid lined with
endothelial cells
19.3.1 Structure and
Function of liver
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19.3.1 Structure and
Function of liver
Kupffer cells
Large phagocytic
macrophage
Attached to the walls ofsinusoids
Destroy old
erythrocytes
Ingestion of pathogenicorganisms
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19.3.1 Structure and
Function of liver
ASSOCIATED STRUCTURES WITH LIVER
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19.3.1 Structure and
Function of liver
Acinus
functional unit of a
liver
consist of: 3 row of hepatocytes
A sinusoid
Bile canalliculus
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Branch ofhepatic portal vein
Branch of
hepatic artery
Hepatocytes
Sinusoid
contains blood
Branch of bile duct Bile canaliculus
contains bile
Branch of hepatic vein
Kupffer cell
An acinus
19.3.1 Structure and
Function of liver
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19.3.1 Structure and
Function of liver
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19.3.1 Homeostatic
Functions of liver
1. Carbohydrate
Metabolism
2. Detoxification
3. Transamination &
Deamination of
Amino Acids
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19.3.1 Homeostatic
Functions of liver
1. Carbohydrate Metabolism
Role ofinsulinin high blood sugar level:
Hexose sugars (glucose) are converted to glycogen
by the insulin release in liver
Stored as insoluble polysaccharide glycogen in
liver
Process called GLYCOGENESIS
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19.3.1 Homeostatic
Functions of liver
1. Carbohydrate Metabolism
Role ofglucagon inlow blood sugar level :
Glycogen (storage molecule in liver) is converted
to glucose (hexose sugar) by glucagon
Glucose is substrate for cellular respiration
Process called GLYCOGENOLYSIS
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19.3.1 Homeostatic
Functions of liver
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19.3.1 Homeostatic
Functions of liver
GLUCONEOGENESIS
is metabolic pathway results in the generation of glucose from
non-carbohydrate carbon substrates such as lactate, glycerol,
and amino acids.
main mechanisms humans and many other animals use to keep
blood glucose levels from dropping too low (hypoglycemia).
other process than maintaining blood glucose levels besides
glycogenolysis
This process occurs during periods of fasting, starvation, low-
carbohydrate diets, or intense exercise and is highly endergonic
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19.3.1 Homeostatic
Functions of liver
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3
When blood glucose
level rises, a gland called
the pancreas secretes
insulin,
a hormone, into the
blood.
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.
2
Glucagon promotes
the breakdown of
glycogen in theliver and the
release of glucose
into the blood,
increasing blood
glucose level. When blood glucose
level drops, the pancreas
secretes the hormone
glucagon, which opposes
the effect of insulin.
STIMULUS:
Blood glucose
level risesafter eating.
Homeostasis:
90 mg glucose/
100 mL blood
STIMULUS:
Blood glucose
level drops
below set point.
3
4
1
19.3.1 Homeostatic
Functions of liver
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2. Detoxification
Removal of toxins or harmful substances
by absorbing and changing them chemically
Eg: Bacteria, alcohol, nicotine and other drugs
Hepatocytes produce enzymes
to breakdown the toxins into harmless substances
excreted by the kidney
19.3.1 Homeostatic
Functions of liver
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If alcohol is taken in excessover a period of time,
Liver breakdown
Cirrhosis
Pain killer like paracetamol, if
taken in excess,
Changed into substances
which affects enzyme
systems
Cause liver and other tissue
damage
19.3.1 Homeostatic
Functions of liver
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19.3.1 Homeostatic
Functions of liver
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3. Transamination & Deamination of Amino Acids
Transamination
The process of synthesizing non-essential amino acids
Amino group of an amino acid is transferred to anotherorganic acid
General principle:
Exchange of chemical groups
Examples: Alanine, glutamate, serine
19.3.1 Homeostatic
Functions of liver
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19.3.1 Homeostatic
Functions of liver
H t ti
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19.3.1 Homeostatic
Functions of liver
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Deamination
Proteins are not stored in the
body
Excess amino acids are brokendown in the liver
The amino group (NH2) is
removed forming an acid keto
The acid keto can enter theKrebs cycle
The amino group is converted
to ammonia (NH3)
19.3.1 Homeostatic
Functions of liver
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19.3.1 Homeostatic
Functions of liver
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CONCLUSION
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NEXT LECTURE
19.3 HUMAN HOMEOSTATIC ORGAN: LIVER AND KIDNEY
19.3.2 Structure and functions of kidney