10/27/2010 1 Objectives Objectives To begin unit on excretory system. I.D. elements of the gross anatomy. - Kidney - Bladder - Sphincters Introduce the nephron and its general function. Learn some interesting facts about the excretory system. Functions of the Functions of the Excretory System Excretory System The kidneys excrete nitrogenous wastes, such as urea, uric acid, creatinine and ammonium. The kidneys maintain blood volume by regulating water excreted. Monitor blood composition and blood pH by regulating electrolyte excretion. Kidneys secrete the enzyme renin, which helps maintain blood pressure. The kidneys secrete erythropoietin, which stimulates RBC production. Gluconeogenesis during prolonged fasting. Figure 25.1 Esophagus (cut) Inferior vena cava Adrenal gland Hepatic veins (cut) Renal artery Renal hilum Renal vein Iliac crest Kidney Ureter Urinary bladder Urethra Aorta Rectum (cut) Uterus (part of female reproductive system) Amazing Facts Amazing Facts About 1100-1200 liters of blood pass through the capillaries in our kidneys every day. The kidneys filter nearly 200 liters of fluid from the bloodstream every day! Our kidneys extract about 180 L (45 gallons) of fluid/filtrate. The kidneys refine the filtrate, and in a typical day we excrete only about 1.5 L of urine. Figure 25.2a Body wall • Perirenal fat capsule Renal artery Renal vein Inferior vena cava Aorta • Fibrous capsule • Renal fascia anterior posterior Supportive tissue layers Body of vertebra L 2 Peritoneum Peritoneal cavity (organs removed) Anterior Posterior (a) Position said to be Retroperitoneal Figure 25.3 Renal cortex Renal medulla Major calyx Renal pelvis Ureter Minor calyx Renal column Renal pyramid in renal medulla Fibrous capsule Renal hilum (a) Photograph of right kidney, frontal section (b) Diagrammatic view