URINARY SYSTEM by JESSIE MARIE ENAD

URINARY SYSTEM

main24000174 — 2025-10-14 05:52:06 UTC

The urinary system is the body’s major excretory system responsible for removing waste products from the blood and maintaining the body’s internal balance. It's function is excretion, regulates blood volume and pressure, maintains ion and pH balance, stimulates red blood cell production through erythropoietin, and activates vitamin D to help control calcium levels in the body.

KIDNEY

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Kidneys are two bean-shaped organs located on each side of the vertebral column, just below the rib cage. Each kidney is about the size of a clenched fist and is protected by a layer of connective and adipose tissue. They serve as the primary excretory organs of the urinary system and perform several vital functions. Their main role is to filter blood—removing waste products, toxins, and excess ions to form urine.

URETERS

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Ureters are narrow, muscular tubes that transport urine from the kidneys to the urinary bladder. Each ureter begins at the renal pelvis, located at the kidney’s hilum, and extends downward through the abdominal cavity to enter the bladder’s posterior surface. Urine does not simply flow by gravity; instead, the smooth muscles of the ureter walls produce peristaltic waves—rhythmic contractions that push urine toward the bladder every few seconds. As the ureters enter the bladder, they pass through its wall at an angle that prevents urine from flowing backward, ensuring a one-way movement of urine from the kidneys to the bladder

URINARY BLADDER

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urinary bladder is a hollow, muscular organ that serves as a temporary storage site for urine before it is eliminated from the body. The bladder’s wall is made up of transitional epithelium, a lamina propria, smooth muscle layers (called the detrusor muscle), and a fibrous outer layer. These structures allow it to expand and contract depending on how much urine it contains. The bladder can hold up to about 1 liter of urine, but the urge to urinate usually begins when it contains 300–400 mL. Its main function is to store urine and release it at the right time, helping maintain proper elimination and fluid balance in the body.

URETHRA

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Urethra is a tube that carries urine from the urinary bladder to the outside of the body. It exits the bladder inferiorly and anteriorly and serves as the final passageway for urine elimination. The external urinary sphincter, made of skeletal muscle, acts as a voluntary valve that controls urine flow. In males, the urethra is longer and also serves as a passage for reproductive fluids, while in females, it is shorter and opens just in front of the vaginal opening

1. FILTRATION

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Filtration is the first step in urine formation. Blood enters the glomerulus (a cluster of capillaries) under high pressure, forcing water and small solutes—such as ions, glucose, and urea—out of the blood and into the Bowman’s capsule. Large molecules like proteins and blood cells remain in the bloodstream because they’re too big to pass through the filter.

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2. REABSORPTION

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After filtration, the filtrate flows through the tubules, where the body takes back the useful substances it still needs. Water, glucose, amino acids, and ions are reabsorbed from the filtrate into the blood through surrounding capillaries. This process helps maintain proper fluid and electrolyte balance.

3. SECRETION

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In this final process, additional wastes and excess ions (like hydrogen, potassium, and drugs) are secreted from the blood into the tubule. This step helps regulate blood pH and eliminate substances not removed during filtration.

After these processes, the resulting fluid—urine—flows from the collecting ducts into the renal pelvis, then through the ureters

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And then to the urinary bladder for storage before urination

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And lastly, through the urethra where is the tube that carries urine from the bladder to the outside of the body. During urination, the bladder muscles contract, and the urethral sphincters relax to allow urine to pass out.

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Reference List

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Clinic, C. (2025, April 22). Renal services to provide high quality dialysis care at Cleveland Clinic London. Cleveland Clinic. https://newsroom.clevelandclinic.org/2020/11/16/renal-services-to-provide-high-quality-dialysis-care-at-cleveland-clinic-london

Hutchins, J., Price, T., Burr, J., Johnston, M., Silberman, P., Speth, J., West, J., & Allen, M. (n.d.). Tubular reabsorption and secretion. Integrated Human Anatomy and Physiology Part 2 (NOT UPDATED). https://uen.pressbooks.pub/anatomyphysiology2/chapter/tubular-reabsorption-secretion/

Urinary Bladder Images – Browse 119,544 stock photos, vectors, and video. (n.d.). Adobe Stock. https://stock.adobe.com/search?k=urinary+bladder

VanPutte, C. L., Regan, J. L., & Russo, A. F. (2020). Seeley’s anatomy & physiology (11th ed.). McGraw-Hill Education.

Visible Body, part of Cengage Learning. (n.d.). Urine creation. https://www.visiblebody.com/learn/urinary/urine-creation

main24000174 — 2026-01-30 07:06:45 UTC

main24000174 — 2026-01-30 07:07:13 UTC