Urinary Outline

Urinary Outline - Chapter 26: The Urinary System An...

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Chapter 26: The Urinary System An Overview of the Urinary System, p. 952 The urinary system has three major functions: o (1) excretion , the removal of organic waste products from body fluids, o (2) elimination , the discharge of these waste products into the environment, and o (3) homeostatic regulation of the volume and solute concentration of blood plasma. The excretory functions of the urinary system are performed by the two kidneys—organs that produce urine, a fluid containing water, ions, and small soluble compounds. Urine leaving the kidneys flows along the urinary tract, which consists of paired tubes called ureters , to the urinary bladder , a muscular sac for temporary storage of urine. On leaving the urinary bladder, urine passes through the urethra , which conducts the urine to the exterior. The urinary bladder and the urethra are responsible for the elimination of urine, a process called urination or micturition . In this process, contraction of the muscular urinary bladder forces urine through the urethra and out of the body. In addition to removing waste products generated by cells throughout the body, the urinary system has several other essential homeostatic functions that are often overlooked, including the following: o Regulating blood volume and blood pressure , by adjusting the volume of water lost in urine, releasing erythropoietin , and releasing renin . o Regulating plasma concentrations of sodium, potassium, chloride, and other ions , by controlling the quantities lost in urine and controlling calcium ion levels through the synthesis of calcitriol . o Helping to stabilize blood pH , by controlling the loss of hydrogen ions and bicarbonate ions in urine. o Conserving valuable nutrients , by preventing their excretion in urine while excreting organic waste products— especially nitrogenous wastes such as urea and uric acid . o Assisting the liver in detoxifying poisons and, during starvation, deaminating amino acids so that other tissues can break them down. These activities are carefully regulated to keep the composition of blood within acceptable limits. The Kidneys, p. 952 The kidneys are located on either side of the vertebral column, between vertebrae T12 and L3. The left kidney lies slightly superior to the right kidney. The superior surface of each kidney is capped by an adrenal gland. The kidneys and adrenal glands lie between the muscles of the dorsal body wall and the parietal peritoneum, in a retroperitoneal position. The position of the kidneys in the abdominal cavity is maintained by (1) the overlying peritoneum, (2) contact with adjacent visceral organs, and (3) supporting connective tissues. Each kidney is protected and stabilized by three concentric layers of connective tissue: o The renal capsule , a layer of collagen fibers that covers the outer surface of the entire organ. o
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Urinary Outline - Chapter 26: The Urinary System An...

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