4th Form Bio Excretion PowerPoint PDF
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Ms. Allwood
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This PowerPoint presentation covers the topic of excretion in biology, focusing on the processes and organs involved in excretion within plants and animals. It includes the structure and function of the urinary system and the detailed process of urine formation.
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Excretion 4th Form Biology Opt. A & C Teacher: Ms. Allwood Definitions of Excretion & Egestion 1 2 Excretion is the removal of Egestion is the removal of metabolic waste from the undigested waste from body or waste that is th...
Excretion 4th Form Biology Opt. A & C Teacher: Ms. Allwood Definitions of Excretion & Egestion 1 2 Excretion is the removal of Egestion is the removal of metabolic waste from the undigested waste from body or waste that is the body. Waste that is produced from a chemical not produced from a process. The waste is chemical process. called an excretory product. Importance of Excretion + Excretory products need to be eliminated from the body for: + homeostasis (The maintenance of a constant internal environment despite changes on the outside.) + to prevent poisonous substances from accumulating in the body or organism. + Urea being a nitrogenous substance can be toxic to the body if it remains. Hence it must be eliminated. Excretory Products in Plants + Oxygen (excreted through the stomata of leaf) + Water (excreted through the stomata of the leaf and from the dorsal side of the leaf during transpiration) + Calcium Oxalate (leaves that fall off containing crystals of calcium oxalate; the leaves often change to bright colours which are due to waste pigments) + Tannins (excreted in the bark of trees that fall off). Tannins have commercial value being used in dye. Excretory Products in Plants Cont’d Some excretory products are stored in dead structures of the plant making these areas less likely to rot or be eaten. Such products include oils, tannins and dyes. Excretory Products in Animals Water Carbon Urea (excreted in dioxide (excreted in urine, sweat (excreted in urine and and exhaled exhaled air). sweat). air). Bilirubin/Bile Heat pigments (excreted in (excreted in exhaled air). faeces). Excretion in Animals Excretion in animals is carried out by the urinary system. The structure of the kidney + The kidney has three regions: + Outer region called the cortex. + Inner region called the medulla. + Expanded region of the ureter called the pelvis. + There is the ureter that projects from the pelvis. + The kidney has two blood vessels associated with it: + the renal artery + the renal vein The structure of the kidney Cont’d + The cortex comprises of the Bowman’s capsules and convoluted tubules of the nephrons in the kidney. + The medulla comprises of the loops of Henle and collecting ducts of the nephrons in the kidney. The medulla is also made up of renal pyramids that project into the pelvis. + The pelvis collects urine from the medulla and deposits it in the ureter. Functions of the parts of the kidney + Renal capsule- protects the inner parts of the kidney. + Renal cortex- carries out ultra-filtration and selective reabsorption. + Renal medulla (renal pyramids)- carries out selective reabsorption. + Renal pelvis- collects urine from the renal pyramids of the medulla. + Ureter- transports urine to the bladder. + Renal artery- transports oxygenated blood to the kidney. + Renal vein – transports deoxygenated blood from the kidney. + Nephron/kidney tubule- makes up the kidney and forms urine. Structure of the nephron + Thousands of nephron make up each kidney. + Each nephron comprises of the parts shown in the diagram. Kidney’s Function In Excretion (urine Formation) + Glomerulus & Bowman’s capsule- blood flows through the renal artery into the afferent arteriole which leads the blood into the glomerulus. A high blood pressure builds up and is maintained in the glomerulus because the afferent arteriole has a larger diameter than the efferent arteriole. + As a result of this pressure substances from the blood are forced out of the glomerulus into the Bowman’s capsule. This is called ultra-filtration. + Substances that are filtered out of the blood are small in molecular mass and collectively are described as the glomerular filtrate. Urine Formation Cont’d + Such substances are : + Glucose + Amino acids + Vitamins + Some hormones + Urea + Uric Acid + Ions + Water Urine Formation Cont’d + Remaining in the blood are some water, blood cells, platelets and plasma proteins which are too large to filter through the glomerulus. + PCT- The glomerular filtrate passes from the Bowman’s capsule into the PCT. Selective reabsorption begins here in which 80% of the filtrate is reabsorbed into the bloodstream. + This includes amino acids, glucose and ions which diffuse across the PCT and into the capillaries surrounding the PCT. Urine Formation Cont’d + Loop of Henle- The walls of the upper parts of the ascending limb are impermeable to water. + The walls of the descending limb are permeable to water, therefore as the fluid flows down the limb it is drawn out by osmosis into the capillaries that wrap around the nephron. Urine Formation Cont’d + DCT- Sodium ions are actively reabsorbed into the bloodstream from the tubule. + Potassium ions are actively transported into the tubule. This process is called secretion. + The remaining filtrate contains some water, urea and salts that were not reabsorbed throughout the selective reabsorption. This is urine and is collected in the collecting duct to enter the pelvis. + From the pelvis the urine flows into the ureter which transports it to the bladder. Then the urine flows outside. Urine Formation Cont’d Summary of Urine Formation Reasons for kidney Failure + Diabetes + Damage to the PCT which cannot reabsorb all the glucose in the filtrate. Hence some are passed out in the urine. + High Blood Pressure/ Hypertension- damages the glomerulus which causes proteins to be filtered out of the blood and into the kidney tubule. Osmoregulation is the maintenance of a constant water content in cells in the body by the process of osmosis. The process of osmosis is regulated by the kidneys. Regulation of Osmoregulation Low Water Balance in Cells High Water Balance in Cells + Cells in isotonic + Cells in isotonic solution/equilibrium solution/equilibrium + Osmoreceptors in the + Osmoreceptors in the hypothalamus. hypothalamus. + The pituitary gland that + The pituitary gland that secretes more Anti-diuretic hormone (ADH) in the secretes less Anti-diuretic bloodstream. hormone (ADH) in the + Increases the permeability bloodstream. of the walls of the distal + The walls of the distal convoluted tubules and convoluted tubules and collecting ducts in the collecting ducts become kidney. impermeable. Osmoregulation Cont’d Low Water Balance in Cells High Water Balance in Cells + This results in more + This results in less water being water being reabsorbed into the reabsorbed into the bloodstream and less bloodstream and more water excreted in the water excreted in the urine. urine. + More water in the + Less water in the bloodstream rises the bloodstream lowers water content of cells the water content of to equilibrium. cells to equilibrium. QUESTIONS