What is excretion? - Excretion is the removal of metabolic waste products and substances in excess from the body., What is metabolic waste? - Metabolic waste refers to any substance produced as a result of cellular processes that the body does not require., What is the basic unit of the kidney? - The nephron, What are the two processes involved in the formation of urine? - Ultrafiltration and selective reabsorption, What is reabsorbed at the proximal convoluted tubule? - All glucose, all amino acids, most of the water and most of the mineral salts, What is reabsorbed at the loop of Henle? - Some water., What is reabsorbed at the distal convoluted tubule? - Some water and some mineral salts., What is reabsorbed at the collecting duct? - Some water; the amount can be controlled by the secretion of anti-diuretic hormone., What is osmoregulation? - Osmoregulation is the control of blood water potential and solute concentration within a narrow limit., What are the two possible interventions when the kidneys fail? - Kidney transplant or dialysis., How does ultrafiltration occur? - The afferent arteriole is wider than the efferent arteriole. This generates high hydrostatic blood pressure that forces all small substances like glucose, amino acids, urea and water from the glomerulus into the Bowman's capsule. Larger substances like proteins and blood cells are too big to pass through the basement membrane., Why do cells lining the proximal convoluted tubule have many mitochondria? - Having more mitochondria increases the amount of energy released via aerobic respiration for the active transport of useful substances like glucose and amino acids from the lumen of the proximal convoluted tubule., What is the effect of ADH? - ADH increases the permeability of the collecting duct to water., How does the body respond when blood water potential decreases (e.g., long periods without drinking)? - The hypothalamus detects the decrease in blood water potential and produces more ADH. The hypothalamus also stimulates the pituitary gland to release more ADH into the blood. ADH travels in the blood to the collecting duct of the kidneys, causing the collecting ducts to be more permeable to water. This causes more water to be reabsorbed at the collecting duct into the blood, reducing the volume of water excreted. This helps raise blood water potential., How does the body respond when blood water potential increases (e.g., sudden intake of large volumes of water)? - The hypothalamus detects the increase in blood water potential and produces less ADH. The hypothalamus also stimulates the pituitary gland to release less ADH into the blood. This causes the collecting ducts to be less permeable to water. This causes less water to be reabsorbed at the collecting duct into the blood, thereby causing more water to be excreted as urine. This helps lower blood water potential., How is the dialysis machine designed for efficient dialysis? - 1. Dialysis tubing is narrow and highly coiled to increase the SA:V ratio; 2. Dialysis fluid flows in the opposite direction as blood in the tubing to maintain a steep concentration gradient; 3. Dialysis tubing contains the normal concentration of useful substances like glucose and amino acids, helping to replenish the patient's blood; 4. Dialysis fluid contains no excretory waste, generating a steep concentration gradient to extract as much waste from the patient's blood as possible.,

Excretion in Humans - Flash cards

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