Anatomy & Physiology

Anatomy & Physiology Study Guide These capillaries converge into the efferent arteriole that carries blood out of the glomerulus . This mass of capillaries is covered by a membranous sac called Bowman's capsule (which empties into the renal tubule). This complete structure is known as a renal corpuscle. This area is where water, salts, glucose, urea, uric acid, creatinine, and other substances are filtered. Bowman's capsule is drained by the renal tubule. The first part of the tubule is in a coiled position and is called the proximal convoluted tubule . This portion eventually straightens and descends toward the medulla, but it curves back upward at the loop of Henle . As the tubule ascends, it once again forms a coiled segment that is called the distal convoluted tubule . The distal convoluted tubules drain into a system of wide tubes called the collecting tubules. The renal corpuscles lie in the cortex; whereas, loop of Henle and the collecting tubules lie in the medulla.

More blood flows into the kidneys than is necessary for the provision of oxygen and nutrients to the kidney. This blood supply nourishes the kidney, but also a portion of blood is filtered by the kidney for processing. When stress is placed on the body due to hemorrhage, the blood flow to the kidneys is reduced, which causes a decrease in urine production. A clearance value indicates the degree to which a substance is removed from the blood by excretion in the voided urine. Glomerular filtrate is comparable to plasma, except that it contains very little protein. While 125 mL of glomerular filtrate is produced per minute, most of it is reabsorbed by the renal tubules. Since none of the creatinine in the glomerular filtrate is reabsorbed, the plasma clearance of creatinine is 125 mL per minute.

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