Diffusion

THE NUTRITION FUNCTION IIThe excretory system.

Removal of Waste ProductsCertain waste products would become highly toxic if they were to accumulate. This could damage tissues.

An excess of water could also lead to a number of complications.

Thus, the waste products must be removed they continually move into the bloodstream, which carries them to the excretory organs.

Raw Materials (Food and 02)Useful Materials Useless MaterialsEgested (faeces)MetabolisedMetabolic Waste Products (urea and CO2)ExcretedUseful Products

Excretory OrgansThere are four main excretory organs:LungsColon (large intestine)SkinKidneys

The liver is not an excretory organ, but produces many products which are excreted elsewhere. Toxins and drugs as well as alcohol, is broken down in the liver. Hence, an excess of smoking, medication and alcohol is extremely harmful to the liver.

The Lungs

The carbon dioxide released from cellular respiration is carried to the lungs in the blood. It then diffuses across the respiratory membrane and is exhaled.A small amount of heat and water is excreted this way.

The Colon

Bile pigments, from the break down of haemoglobin, and cholesterol are synthesised in the liver. They pass into the small intestine as bile and are finally excreted in the faeces as bile salts, from the colon.Mucus and bacteria are too excreted through the colon.

The SkinSweat, which is excreted through the skin, contains water, salts and some urea. As the water in the sweat is excreted, heat is lost and the body is cooled. Sweat is a form of excretion as it rids the body of waste, as well as a form of secretion as it maintains the body temperature.

The Urinary SystemThe main function of the urinary system is to maintain homeostasis by regulating the volume and concentration of body fluids. It filters and reabsorbs certain materials from the blood.

The urinary system is made up of the following parts:Two kidneysTwo uretersA bladderAn urethra

KidneysThe kidneys aid in: excretion as they filter waste out of the blood regulate the water and salt balance in the body.They secrete some hormones, that control blood pressure or red blood cell production, for example.One kidney the right kidney is slightly lower than the left as it is pushed down by the liver, which is larger on the right.

KidneysRenal artery: carries waste products to the kidney and supplies the kidneys with oxygen and nutrients.Renal vein: contains the purest blood in the body. It carries CO2 to the inferior vena cava.

GlomruloArteriola

BladderStores urine.Is stimulated by impulses from a motor nerve, to contract to expel the urine (micturition reflex).Has sphincter muscles at the base to control the flow of urine.

UrethraCarries urine from the bladder to outside the body. A MANS urethra is CONNECTED WITH A DUCT OF THE REPRODUCTIVE SYSTEM.A WOMANS urethras are INDEPENDENT OF HER REPRODUCTIVE SYSTEM.UretersCarry urine from the kidneys to the bladder.

No entra en este examen.

1. Glomerular filtration: Water, salts, nutrient and waste molecules move from the glomerulus to the inside of the glomerular capsule.

2. Tubular reabsortion: Nutrient and salt molecule are reabsorbed from the convoluted tubules into capilaries.

3. Tubular secretion: Certain molecules are secreted from capilaries into convoluted tubules