chapter 19 - homeostasis (part 2)

7/30/2019 Chapter 19 - Homeostasis (Part 2)

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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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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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Function of liver

Each lobule is filled with

many vertical plates ofliver cells

Hepatocytes


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Function of liver

Hepatocytes

Contains nuclei, Golgi

apparatus, many

mitochondria &lysosomes

Rich in glycogen granules

Tightly packed together


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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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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


Function of liver


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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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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


Function of liver


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Function of liver

Kupffer cells

Large phagocytic

macrophage

Attached to the walls ofsinusoids

Destroy old

erythrocytes

Ingestion of pathogenicorganisms


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Function of liver

ASSOCIATED STRUCTURES WITH LIVER


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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


Function of liver


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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

chapter 19 - homeostasis (part 2)

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