During this laboratory exercise will identify by the graph given which is isotonic, hypotonic, or hypertonic. The kidneys are a pair of fist-sized organs located outside the peritoneal cavity on each side of the spine. The kidney is a highly specialized organ that maintains the internal environment of the body by selectively excreting or retaining various substances according to specific body needs. The process of urine formation and adjustment of blood composition involves three processes: glomerular filtration, tubular reabsorption, and tubular secretion. The first part of the process of urine formation occurs in the glomeruli which act as filters, allowing water, glucose, salt and waste materials to pass through to the Bowman’s capsule but preventing and red blood cells and plasma proteins to pass through. Reabsorption occurs in the proximal tubules of the nephron. Water, glucose, amino acids, sodium and other nutrients are reabsorbed into the bloodstream in the capillaries surrounding the tubules. Water moves via the process of osmosis: movement of water from an area of higher concentration to one of lower concentration. Tubular secretion is the final step in the process of urine formation which transfers materials from peritubular capillaries to renal tubular lumen and occurs mainly by active transport. ADH is secreted by the posterior pituitary (neurohypophysis) when there is a decrease in water concentration (increase in osmolarity) which will cause an increase in water reabsorption (decrease in osmolarity). ADH most important function is to conserve the fluid volume of your body by reducing the amount of water passed out in the urine. When there is a decrease in serum sodium levels (decrease in osmolarity) the ACTH causes the adrenal cortex to release aldosterone, thereby increasing sodium reabsorption in the distal convoluted tubules of the kidney (increasing osmolarity). Aldosterone also acts on the kidney to reabsorb sodium and water…
