Excretion

• Excretion is the process by which metabolic waste products and toxic substances are removed from the body.
• Excretory organs involve the Cortex, Medulla, consists of Pyramids, contains Ultrafiltration, and involves Selective reabsorption, which is regulated by ADH.
• The formation of urine involves the kidneys, which are part of the excretory system.
• Osmoregulation includes kidney dialysis, which requires excretion.
• Kidneys contain numerous Nephrons, which contain numerous Pyramids, and contain numerous Nephrons.
• Excretion is necessary for the removal of metabolic waste products and toxic substances from the body.
• Metabolic reactions produce metabolic waste products that can harm the body if they accumulate, therefore, these metabolic waste products need to be removed.
• The chemical reactions that take place in living cells can be categorised into complex substances, simple substances, enzymes, and complex substances.
• Examples of metabolic reactions include anabolism, which involves the synthesis of complex molecules, and catabolism, which involves the breakdown of complex molecules.
• Metabolism is the sum of all the chemical reactions within the body of an organism.
• A concentration gradient for nitrogenous wastes is set up between dialysis fluid and the blood during dialysis.
• Filtered blood is returned to the patient after dialysis.
• Dialysis fluid with waste products from the patient’s blood is returned to the dialysis machine.
• The dialysis fluid has the similar concentration of glucose and amino acids as blood but it lacks the nitrogenous waste during dialysis.
• Removal of metabolic waste products from the blood via diffusion occurs during dialysis.
• Blood flows in the direction opposite to the flow of the dialysis fluid to maintain a constant concentration gradient during dialysis.
• Kidney failure can lead to ultrafiltration, where there is a high hydrostatic blood pressure at the glomerulus due to the higher resistance to blood flow at the efferent arteriole end, and the partially permeable basement membrane around the glomerular capillaries acts as a filter.
• Platelets and blood cells remain in the tubing during dialysis.
• The human urinary system consists of the kidneys, ureters, bladder, and urethra.
• The dialysis machine consists of a partially permeable membrane, a protein molecule, a red blood cell, and urea and mineral salts.
• Selective reabsorption allows all glucose and amino acids to be reabsorbed via diffusion and active transport.
• A partially permeable membrane separates the dialysis fluid from the patient’s blood during dialysis.
• Urine is formed when water, small molecules such as glucose, amino acids, mineral salts, and urea are excreted, while large molecules such as plasma proteins and red/white blood cells are not filtered out.
• Excretion in humans is necessary for the removal of waste products and excess water.
• The filtered blood is returned to a vein in the patient’s arm after dialysis.
• Osmoregulation is the process of maintaining the correct balance of water and electrolytes in the body.
• Ultrafiltration occurs because of force (high hydrostatic pressure) and a filter (basement membrane around glomerular blood capillaries is partially permeable and acts as a filter).
• Small molecules such as urea and metabolic waste products diffuse out of the tubing during dialysis.
• Ultrafiltration allows useful substances to be reabsorbed, with >80% of filtrate reabsorbed at the proximal convoluted tubule.
• The two conditions required for ultrafiltration to take place are high hydrostatic blood pressure at the glomerulus due to the higher resistance to blood flow at the efferent arteriole end, and the partially permeable basement membrane around the glomerular capillaries acts as a filter.
• While most unicellular organisms excrete waste products via simple diffusion, larger organisms have excretory organs for excretion.
• Osmoregulation maintains the concentration of water and salts within an organism, it is a type of homeostasis.
• Examples of excretory organs found in mammals include the skin, lungs, liver, and kidneys.
• Blood volume is controlled by removing excess salts and water, blood pressure is also indirectly regulated by osmoregulation.
• ADH secretion by the pituitary gland depends on ‘ instructions ’ from the hypothalamus.
• If the body is dehydrated or lower water potential, more ADH is secreted → more water reabsorbed, the urine excreted is more concentrated with lesser volume.
• Water potential of plasma increases above normal.
• Kidneys help to regulate the concentration of water and salts in blood, they are called osmoregulators.
• If the blood plasma is too dilute, the RBCs would absorb water, expand and burst.
• If there is excess water or higher water potential in the blood, less ADH is secreted → less water is reabsorbed, the urine excreted is more dilute with larger volume.