Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Urogenital System
Urinary (Excretory) System
Mechanisms of Urine Formation and Excretion - Physical and Chemical Properties of Urine

Urine is a pale yellow liquid consisting of 95% Water and 5% solid solutes. These include urea (2%), uric acid (0.05%), creatinine (0.075%), and other substances such as potassium and sodium salts. Over the course of a day, the body excretes 25–30 g of urea and up to 25 g of inorganic substances through urine. In Kidney disease or during short-term physical exertion, protein—which should normally be absent—may appear in the urine. The pH reaction of urine depends on diet: a predominantly meat-based diet makes urine acidic, whereas a plant-based diet makes it alkaline or neutral. The presence of Blood in the urine (giving it a red or pink color) may result from mucosal damage or hemorrhaging within the Urinary System Organs. Consuming fresh carrots or beets can also cause the urine to turn pink.

Review and Self-Assessment Questions:

1. Name the phases of Urine Formation in the Kidneys and characterize each of them.

2. List the substances filtered from the blood into the urine within the renal corpuscles.

3. What is Primary and secondary urine? How do they differ?

4. Describe the roles of the Ureters and the Urinary Bladder in The excretion of urine from the body.

5. Explain the nervous and humoral regulation of Urine Formation and Excretion.



Last update: 10/08/2026

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