Excretion [Autosaved].pptx .............................

notes on excretion

1. Excretion: Removing Body Waste Discover how your body gets rid of waste!

2. learning outcomes Identify the organs involved in excretion and the waste products they remove. Explain the role of the lungs, kidneys, and liver in excretion. Describe assimilation and deamination of amino acids in the liver. Explain the importance of excretion in preventing toxicity. Identify the organs involved in excretion and the substances each organ eliminates. correctly label medulla and cortex on kidney diagram. Explain the role of the liver in dealing with excess amino acids. Explain why urea must be excreted. Success criteria

3. What is Excretion? Removal of waste products of metabolism and substances in excess of requirements. Diagram of human excretory system: kidneys, ureters, bladder.

4. Lungs: CO2 Excretion • CO2 comes from cellular respiration . Lungs remove carbon dioxide from the blood . Function of kidney Removal of urea and excess water and the reabsorption of glucose and some salts. Urea is formed in the liver from excess amino acids by deamination process. Why is excretion important? Removes toxic waste (CO₂, urea). Prevents harmful build-up in the blood.

5. The Urinary System Blood is transported to the kidneys via the aorta and renal artery. Blood is then filtered in the kidneys to remove urea, excess water and excess ions. The resulting liquid produced by the filtration of blood is called urine. (a solution of urea, excess water and ions) Urine can be dilute or concentrated depending on the amount of water reabsorbed from the blood. It all depends on the body’s state of hydration. Filtered blood returns to the vena cava (main vein) via a renal vein. The urine formed in the kidney passes down a ureter into the bladder, where it is stored. A sphincter muscle controls the release of urine through the urethra. This system removes waste from your blood. It includes kidneys, ureters, bladder, and urethra, working together to form and eliminate urine.

6. Explain the role of the liver in dealing with excess amino acids . Transport to the liver Excess amino acids in the bloodstream cannot be stored in the body. They are carried to the liver via the hepatic portal vein. Assimilation of amino acids Some amino acids are assimilated in the liver, meaning they are converted into proteins. Examples include plasma proteins, such as fibrinogen in the blood. Urea is returned to the bloodstream (into the hepatic vein) and filtered out when it reaches the kidneys . Deamination of amino acids The excess amino acids are broken down into urea. The breakdown of amino acids by removing the nitrogen-containing part of the molecule and converting it into urea in the liver is called deamination .

7. Activity 1: Let’s recall What is meant by excretion? Which organ removes carbon dioxide from the body? Which organ removes urea from the blood? What waste product is formed in the liver from excess amino acids? Why is excretion important for the body?

8. Activity 2 Using the clay provided, make a cross-sectional image of a kidney and label the diagram. Instructions Everyone must join the activity. Keep tables and books clean. Use the items given to make your model. Return markers after use

9. Learning intention We are learning to describe how the nephron and its blood vessels help filter the blood, reabsorb useful substances, and form. Success criteria Label all parts of a nephron and associated blood vessels correctly. Explain the functions of glomerulus, tubule, and collecting duct. Describe how urine is formed and what it contains

10. The nephron Each kidney contains around a million tiny structures called nephrons, also known as kidney tubules or renal tubules The nephrons start in the cortex of the kidney, loop down into the medulla, and back up to the cortex.

11. 1) Ultra filtration Blood from the renal artery enters the glomerulus at high pressure. Water, urea, salts and glucose are filtered out of the blood into the Bowman’s capsule. Blood cells and large proteins cannot pass through, as those are too large to be filtered out hence it remains in the blood.

12. The substances forced out of the capillaries are: glucose, water, urea, and salts. Some of these are useful and will be reabsorbed back into the blood further down the nephron. 2) Selective Reabsorption

13. 2) Selective Reabsorption In the nephron, some of the ions and all the glucose get reabsorbed into the blood capillaries by active transport while some water gets reabsorbed into the blood capillaries by osmosis. Urea is not reabsorbed and all urea is transferred to the collecting duct and excreted from the body in the urine.

14. Formation of Urine The remaining fluid (urea, excess water, excess ions) forms urine It passes down the collecting duct of the tubule, through the pelvis of the kidney into the ureter, then down into the bladder for removal through the urethra. https://www.youtube.com/watch?v=pv5-GwJ90ZM

15. Summary Blood enters kidneys via renal arteries from the aorta. In the cortex, arteries branch into capillaries forming glomeruli. High pressure in glomeruli forces small molecules (glucose, urea, ions, water) into tubules; large proteins remain in the blood. In tubules: Water → reabsorbed by osmosis (moves back into blood due to higher solute concentration). Glucose → reabsorbed by active transport (using energy to ensure all glucose returns to the blood in a healthy person). Mineral ions → reabsorbed by diffusion and active transport. As water is reabsorbed, urea concentration increases. Urine passes through collecting ducts → pelvis → ureter → bladder → urethra .