14: The Urinary System

• Suzanne Wakim & Mandeep Grewal
• Butte College

This chapter discusses the concept of excretion and explains the excretory functions of the skin, liver, large intestine, lungs, and kidneys. It also describes the other organs of the urinary system and several urinary system disorders.

• 14.1: Case Study- Waste Management “Wow, this line for the restroom is long!” Bintou says to Maeva, anxiously bobbing from side to side to ease the pressure in her bladder. Maeva nods and says, “It’s always like this at parties. It’s the alcohol.” As you will learn in this chapter, the liver and kidneys are important organs of the excretory system, and impairment of the functioning of these organs can cause serious health consequences.
• 14.2: Introduction to the Urinary System The actual human urinary system, also known as the renal system, is shown in the drawing below. The system consists of the kidneys, ureters, bladder, and urethra, which is the only structure not visible in the sculpture above. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. Between 1 and 2 liters of urine are normally produced every day in a healthy individual.
• 14.3: Kidneys The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta and transports unfiltered blood to the kidney. The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million nephrons, which are the tiny functional units of the kidney, span the cortex and medulla.
• 14.4: Ureters, Urinary Bladder, and Urethra Ureters are tube-like structures that connect the kidneys with the urinary bladder. They are paired structures, with one ureter for each kidney. The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The urethra is a tube that connects the urinary bladder to the external urethral orifice, which is the opening of the urethra on the surface of the body.
• 14.5: Disorders of the Urinary System The kidneys play such vital roles in eliminating wastes and toxins and maintaining body-wide homeostasis that disorders of the kidneys may be life threatening. Gradual loss of normal kidney function commonly occurs with a number of disorders, including diabetes mellitus and high blood pressure. Other disorders of the kidneys are caused by faulty genes that are inherited. Loss of kidney function may eventually progress to kidney failure.
• 14.6: Case Study Conclusion- Alcohol and Chapter Summary As you learned in the beginning of the chapter, consumption of alcohol inhibits a hormone that causes our bodies to retain water. The result is that more water is released in urine, increasing the frequency of restroom trips as well as the risk of dehydration. The excretory system is essential to remove toxic wastes from the body and regulate homeostasis. Limiting alcohol consumption can help preserve the normal functioning of the excretory system so that it can protect your health.

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