The kidneys, which maintain the purity and constancy of our internal fluids, are perfect examples of homeostatic organs. Much like sanitation workers who keep a city's water supply drinkable and dispose of its waste, the kidneys are usually unappreciated until there is a malfunction and "internal garbage" piles up. Every day, the kidneys filter gallons of fluid from the bloodstream. They then process this filtrate, allowing wastes and excess ions to leave the body in urine while returning needed substances to the blood in just the right proportions. Although the lungs and the skin also play roles in excretion, the kidneys bear the major responsibility for eliminating nitrogenous (nitrogen-containing) wastes, toxins, and drugs from the body.
Objective Checklist
Kidneys
- Describe the location of the kidneys in the body.
- Identify the following regions of a kidney (longitudinal section): hilus, cortex, medulla, medullary pyramids, calyces, pelvis, and renal columns.
- Recognize that the nephron is the structural and functional unit of the kidney and describe its anatomy.
- Describe the process of urine formation, identifying the areas of the nephron that are responsible for filtration, reabsorption, and secretion.
- Describe the function of the kidneys in excretion of nitrogen-containing wastes.
- Define polyuria, anuria, oliguria, and diuresis.
- Describe the composition of normal urine.
- List abnormal urinary components.
Ureters, Urinary Bladder, and Urethra
- Describe the general structure and function of the ureters, bladder, and urethra.
- Compare the course and length of the male urethra to that of the female.
- Define micturition.
- Describe the difference in control of the external and internal urethral sphincters.
- Name three common urinary tract problems.
Fluid, Electrolyte, and Acid-Base Balance
- Name and localize the three main fluid compartments of the body.
- Explain the role of antidiuretic hormone (ADH) in the regulation of water balance by the kidney.
- Explain the role of aldosterone in sodium and potassium balance of the blood.
- Compare and contrast the relative speed of buffers, the respiratory system, and the kidneys in maintaining the acid-base balance of the blood.
Developmental Aspects of the Urinary System
- Describe three common congenital problems of the urinary system.
- Describe the effect of aging on urinary system functioning.
