10.1 Introduction to Urinary System
Learning Objectives
After studying this chapter, you will be able to:
- Describe the composition of urine
- Label structures of the urinary system
- Characterize the roles of each of the parts of the urinary system
- Illustrate the macroscopic and microscopic structures of the kidney
- Trace the flow of blood through the kidney
- Outline how blood is filtered in the kidney nephron
- Provide symptoms of kidney failure
- List some of the solutes filtered, secreted, and reabsorbed in different parts of the nephron
- Describe the role of a portal system in the kidney
- Explain how urine osmolarity is hormonally regulated
- Describe the regulation of major ions by the kidney
- Summarize the role of the kidneys in maintaining acid–base balance
Introduction
The urinary system is best known for two essential tasks: cleansing the blood and removing wastes from the body. While these are critical functions, the system plays several other equally vital roles in maintaining homeostasis.
For instance, the urinary system helps regulate the body’s pH—working alongside the lungs and blood buffers to maintain acid-base balance. It also plays a key role in controlling blood pressure, in coordination with the heart and blood vessels. Beyond that, the kidneys regulate the concentration of solutes in the blood, maintaining the proper chemical environment for cellular function.
Did you know your kidneys help control red blood cell production? In fact, about 85 percent of the body’s erythropoietin (EPO)—a hormone that stimulates red blood cell formation—is produced in the kidneys. They also complete the final step in the synthesis of vitamin D, converting calcidiol into calcitriol, its active form, which is crucial for calcium absorption and bone health.
When the kidneys begin to fail, these functions deteriorate, leading to serious consequences. A person may develop symptoms such as fatigue, weakness, anemia, fluid retention (edema), shortness of breath, elevated blood acidity (metabolic acidosis), and dangerous shifts in potassium levels that can cause heart arrhythmias. Each of these issues reflects the loss of a vital kidney function and the disruption of the body’s internal balance.
In addition to filtering and regulating, the urinary system—under the direction of the nervous system—stores urine until an appropriate time for release. It then transports this fluid waste out of the body. If either the nervous system or urinary tract structures are compromised, the result can be a loss of voluntary bladder control, a condition known as incontinence.
In this chapter, you will explore the structure and function of the urinary system, discovering how each component plays a crucial role in maintaining your body’s internal balance. As you study, keep this essential question in mind: What happens if this part doesn’t function properly? This perspective will help you make meaningful connections between anatomy and physiology and deepen your understanding of how the urinary system supports not only your overall health, but also the proper functioning of every other system in the body.
Interactive Link
Watch this video from the Howard Hughes Medical Institute for an introduction to the urinary system.
Louisiana Lagniappe
Did you know that living in Louisiana could affect your kidneys? Along the Mississippi River, an area known as “Cancer Alley” is home to a high number of chemical plants and oil refineries. People who work in or live near these industries may be exposed to harmful substances like benzene and heavy metals, which can damage the kidneys over time. Even common farm chemicals can enter water sources and contribute to long-term kidney issues if people are exposed regularly.
Louisiana’s hot and humid climate can also strain the urinary system. Outdoor workers in construction, agriculture, and oil fields often face long hours in the heat, which increases the risk of dehydration. Without enough water, the kidneys can’t properly flush out waste, leading to kidney stones or even permanent damage. Staying hydrated isn’t just about comfort—it’s essential for protecting kidney function, especially in this environment.
Chronic health conditions common in Louisiana also play a major role. The state has some of the highest rates of diabetes and high blood pressure in the country—two major causes of chronic kidney disease. These problems are more common in underserved communities, where access to health care is limited. So, while the urinary system may not get much attention day-to-day, its health is deeply connected to the environment, lifestyle, and community resources that shape life in Louisiana.