Excretion in Humans

Name: __________________ Topic: Excretion in humans Concepts Summary Notes Nan Hua High School Biology 1 LO: Define excretion and explain the importance of removing nitrogenous and other compounds from the body Definition: Excretion is the process by which metabolic waste products are removed from the body of an organism. Importance: Metabolic (anabolism + catabolism = metabolism) reactions (chemical reactions) produce metabolic waste products. Metabolic waste products are toxic and poisonous if they accumulate in excess in the body. LO: Outline the function of the nephron with reference to ultra -filtration and selective reabsorption in the production of urine

Name: __________________ Topic: Excretion in humans Concepts Summary Notes Nan Hua High School Biology 2 Function of nephron: Removal of metabolic waste products from blood through the processes of ultra-filtration and selective reabsorption, to form urine.

Name: __________________ Topic: Excretion in humans Concepts Summary Notes Nan Hua High School Biology 3 Ultra-filtration: 1. Most of the blood plasma is forced out of the glomerular blood capillaries into the Bowman’s capsule. 2. This is due to the high hydrostatic pressure in the glomerulus. The high blood pressure is present because the afferent arteriole bringing blood into the glomerulus is wider than the efferent arteriole, which carries blood away. 3. A partially permeable membrane called the basement membrane wraps around the glomerular blood capillaries. The membrane allows only small molecules such as glucose, amino acids, urea, water, mineral salts, etc through. 4. Large molecules like proteins, red blood cells, platelets cannot pass through.

Name: __________________ Topic: Excretion in humans Concepts Summary Notes Nan Hua High School Biology 4 Selective reabsorption: 1. As the glomerular filtrate from ultrafiltration passes through the nephron, useful materials such as glucose, amino acids, mineral salts are taken back into the bloodstream by selective reabsorption at the proximal convoluted tubule. 2. All glucose and amino acids molecules will be selectively reabsorbed into the blood capillaries by diffusion and active transport in a healthy individual. 3. Most of the water molecules are reabsorbe