EXCRETION AND THE KIDNEYS

EXCRETION

• The removal from organisms of:

- toxic materials,

- the waste products of metabolism (chemical

reactions in cells including respiration) and

- substances in excess of requirements.

Excretion Egestion

• EGESTION:

Is the passing out of food that has not been digested, as faeces, through the anus.

Excretory organs

• Lungs

• Kidneys

• Liver

• Skin

LUNGS: carbon dioxide and watervapour (incidental)

KIDNEYS: urea, water, salts, toxins, hormones, drugs.

LIVER: bile pigments.

SKIN: water, salts, urea (incidental losses)

EXCRETORY PRODUCTS AND INCIDENTAL LOSSES

Exretory products Incidental losses

LUNGS Carbon dioxide water

KIDNEYS Urea, water, salts, toxins, hormones, drugs

LIVER Bile pigments

SKIN Water, salt, urea

LIVERFunctions

• Regulation of blood sugars.• Production of bile.• Deamination• Storage of iron.• Manufacture of plasma proteins.• Detoxication: breaking down of alcohol, drugs• Breaking down of hormones.• Storage of vitamins

Alcohol and the liver

• The liver receives all the useful and harmfulmolecules that the gut absorbs from food.

• Drugs or poison are harmful molecules.

• Alcohol is a drug. It affects the normal working of thebody.

• It is absorbed from the stomach and liver.

• The cell of the liver convert alcohol in anothersubstance which does not pass through the rest of the body´s circulation.

Alcohol

• In working to protect other tissues the liver is likelyto harm itself.

• The substance produced from alcohol can bedangerous to the liver cells in high concentration.

• It can cause a serious disease called cirrhosis.

• If the liver is damaged by excessive alcohol consumption, then the hole body is affected.

• E.g: Blood glucose concentration cannot becontrolled efficiently.

KIDNEYS:

Structure: - Fairly solid,oval, red-brown and attached to the

abdominal cavity.

- Renal artery: ?

- Renal veins: ?

- Longitudinal section: 3 main parts:

- cortex, medulla and pelvis.

- Leading from the pelvis is a tube, called ureter, whichcarries urine that the kidney has made to the bladder.

NEPHRON

• Is a single glomerulus (tangle of bloodcapillaries), with its renal capsule, renal tube and blood capillaries.

• Kidneys are made of thousands of nephrons.

• Each nephron begins in the cortex, loops down in the medulla, back into the cortex, and then goesdown again through the medulla to the pelvis.

• In the pelvis the nephrons join up with the ureter.

Kidneys and nephron

KIDNEY: FUNCTION

• 1) FILTRATION:

- Blood is brought to the renal capsule in a branch of the renal artery.

- Only small molecules can go through. Theyare squeezed out of the blood into the renal capsule.

- Water, salt, glucose and urea.

- Most proteins are too big, so they stay

in the blood along with blood cells.

KIDNEY:FUNCTION

• 2) REABSORPTION:- Some of the substances in the fluid in the renal

capsule are needed by the body.- All of the glucose, some of the water and some of

the salts need to be kept in the blood. - Usefule substances in the kidney tubule are

reabsorbed and pass back into the blood in the bloodcapillaries wrapped around each kidney tubule.

- The remaining fluid continues on its way along thetubule

- In the collecting duct it is mostly water, with urea and salts dissolved in it. It is called URINE.

THE BLADDER STORES URINE

• The urine from all the nephrons flows into theureters which take it to the bladder.

• The bladder stores urine.

• When it is fulled, the sphincter muscle opens and the urine flows along the urethra and outof the body.

DIALYSIS

• Maintenance of glucose and protein concentration in blood and diffusion of urea from blood to dialysis fluid, which has water, glucose, salts that should be present in the blood. Inside the machine the blood is separated from the dialysis fluid by a partially permeable membrane.

• Dialysis does the work of damaged kidneys.

• Patients need to be treated two or three times a weekand the treatment lasts for several hours (disadvantage

• Application of dialysis in kidneymachines:

The best treatment is a KIDNEYTRANSPLANT but:

THE IMMUNE SYSTEM CAN REJECT TRANSPLANTS:• The person receiving the transplant is the recipient.• The person from whose organ the body was taken is the donor.• The recipient´s immune system recognises the donor organ as being

“foreign”, and attaks it. This is called REJECTION.• The recipient is given drugs called immunosuppresants. The trouble

is that they stop the immune system from doing its normal job, so the person is more likely to suffer from all sorts of infectiousdiseases.

• The chances of rejection are reduced if the donor is a close relativeof the recipient, because they are more likely to have antigens ontheir cells which are simmilar to each other, so the recipient´simmune system is less likely to react to the donated organ as itwere ¨foreign¨.

Successful kidney transplantshaveadvantages over dyalisis treatment

• In the long term, a transplant is much cheaper.

• The patient´s life is less disrupted once theyhave recovered from the operation.