KidneyStructure

AndFunction

Kidney

HOMEOSTASIS IN HUMAN

• Homeostasis is the maintenance of a relatively constant internal environment.

• Physical factor such as body temperature and blood pressure while chemical factor are sugar level and osmotic pressure such as partial of carbon dioxide and oxygen

The excretory system• Plays an important role in homeostasis• The primary organs of the excretory system are

the kidneys.

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Function of the kidneys1. Helps to regulates the water and salt balance in the

body by excreting more or less salt, and increasing the in take or loss of water.

2. Regulate the osmotic pressure and ionic levels in the blood

3. Excrete waste products.4. Regulate the blood pH• Waste products excreted by the kidneys are substances

that are not useful to the body such as waste products from the metabolic reaction (urea, creatinine and uric acid) and foreign substances in the diet (drugs or toxins)

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The human kidney• The kidneys filter the blood and form the

urine which is exits the body through the ureters, urinary bladder and urethra.

• Urine consists of water, urea and other dissolved waste, and some excess nutrients.

• Human kidney has two distinct region:a) Renal cortexb) Renal medulla

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The nephron• The functional unit of the kidney is the nephron.• The human kidney consists of about 1 million

nephrons.• A nephron consists of three major parts:a) Glomerulusb) Bowman’s capsulec) Renal tubule• Renal tubule is made up of the:a) Proximal convoluted tubuleb) Loop of Henlec) Distal convoluted tubule

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The Formation of UrineIn Kidney

• Nephron perform three basic process:1. Ultrafiltration2. Reabsorption3. Secretion

Ultrafiltration• When the blood enters the glomerulus, ultrafiltration take

place when the high pressure forces fluid through the filtration membrane into the capsular space

• The fluid that enters into the capsular space is called the glomerular filtrate

• glomerular filtrate contain water, glucose, amino acid, urea, mineral salt and other small molecule. Some composition as blood plasma but not contain red blood cells and plasma protein 12

Ultrafiltration in bowman’s capsule

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Reabsorption• Reabsorption take place when the substance moves

across the renal tubule into the capillary network.• In the proximal convoluted tubule, there are

abundance of mitochondria to generate ATP for the process of active transport that used to reabsorb glucose and amino acid.

• Solute concentration in the capillary network is increase, so that water moves into the blood capillary by osmosis

• In the loop of Henle, water, sodium and chloride ions are reabsorbed.

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• At the distal convoluted tubule, more water, sodium and chloride ions are reabsorbed.

• B the time, the filtrate reaches the collecting duct, very little salt left and 99% of water has been reabsorbed into the bloodstream.

• Only 1% of water in the filtrate actually leaves the body as urine.

• Some urea diffuses out into the surrounding fluid and blood because of its small molecular size.

• Finally, about 45% of the original urea remain in the collecting duct to be excrete in the urine.

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Effect of Impaired Kidney

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Notes about Kidney Dialysis:

The main stages that blood passes through during the dialysis process include:

•Blood enters machine from body (under pressure from radial artery). •Pump (some diagrams show a roller pump) controls pressure and flow rate. •Anticoagulant added to prevent clotting. •Blood passes through dialysis membrane (equivalent to kidney nephrons). •Bubble Trap removes any gas bubbles from blood. •Blood is filtered then returned to the patient's radial vein.

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BLOOD GLUCOSE LEVEL IN THE BODY

After meal

Rise in blood glucose level

Secretion of more insulin or less

glucagon by pancreas

Liver cells absorb glucose

from blood to form

glycogen

Increase in glucose

uptake by body cells for

respiration

Liver cell break down

glycogen into

glucose

Decrease in glucose

uptake by body cells for respiration

Drop in blood glucose level

Secretion of less insulin or more

glucagon by pancreas

During fasting or after exercise

Blood glucose level returns to normal

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Practising a healthy lifestyle• Drugs can alter brain functions and the

rates at which neurones release neurotransmitters• There are some types of drug and their

effects on the body:

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Stimulants• Increase the activity of the central nervous

system• Cocaine, nicotine, amphetamines & caffeine

increase the heart rate and alertness• Hallucinations, LSD perceive things that do not

exist

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Kirsten (ThinkTankCentre)

Depressants• Slow down the activity of the central nervous

system• Alcohol, barbiturates & heroin slow down the

breathing rate &lower blood pressure

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