urinary

Overview of the Urinary System

The urinary or excretory system serves a fundamental role in maintaining the body's acid-base balance. It plays a crucial part in the body's ability to stay healthy, working alongside other systems such as the digestive and integumentary systems to combat disease. When the load of toxins and waste exceeds the capacity of these systems, health complications may arise. For further understanding of disease mechanisms, students are encouraged to explore additional resources, such as CTE Skills' introduction to the cell.

Purpose of the Urinary System

The urinary system is responsible for:

  • Maintaining acid-base balance in the body.
  • Purifying the blood through the elimination of excess substances, thus promoting homeostasis.

Anatomical Structures of the Urinary System

The urinary system is composed of several essential anatomical parts:

  1. Two kidneys
  2. Two ureters
  3. One bladder
  4. One urethra
  5. Urethral meatus

Kidneys

  • Shape and Location: The kidneys are bean-shaped organs located on either side of the vertebral column, positioned behind the upper part of the abdominal cavity.
  • Protection: They are safeguarded by the ribs and cushioned by adipose tissue, known as the adipose capsule.
  • Suspension: The kidneys are suspended in the body, not attached to any major organ, leading to regulations such as the prohibition of kidney punching in boxing.
Internal Structure of the Kidneys

The kidneys comprise two main sections:

  1. Cortex

    • Definition: The outer section of the kidney.

    • Function: Houses the majority of nephrons, the microscopic filtering units essential for urine production.

    • Components of Nephrons:

      • Glomerulus
      • Bowman's capsule
      • Proximal convoluted tubule
      • Distal convoluted tubule
      • Collecting duct

    • Functionality: These structures work together to remove excess water, salts, sugars, and metabolic products, ensuring the maintenance of the body's pH levels and overall homeostasis.

  2. Medulla

    • Definition: The inner area of the kidney.
    • Function: Contains most of the collecting tubules which transport urine from the nephrons to the ureters.

Ureters

  • Description: The ureters are two muscular tubes, measuring approximately 10 to 12 inches in length.
  • Function: They extend from the renal pelvis of each kidney to the bladder, facilitating the transportation of urine.

Bladder

  • Description: The bladder is a hollow sac, similar to the stomach, lined with folds called ruga.
  • Function of Ruga: The ruga allow the bladder to expand as it collects urine.
  • Capacity: It typically accommodates up to one cup of urine, but can hold more until the urge to void arises.

Urethra

  • Description: The urethra is a tube that transports urine from the bladder to the exterior of the body.
  • Sex Differences:
    • In females, the urethra is approximately 1.5 inches long and operates separately from the reproductive system.
    • In males, the urethra is about 8 inches long. Before exiting the body, it passes through the prostate gland. The male urethra serves two systems: the urinary and reproductive systems. Only urine flows through the urethra at the urinary stage, while only semen is conveyed during reproductive use. Both substances will never pass through simultaneously.

Composition of Urine

  • Definition: Urine is the waste product expelled by the urinary system.
  • Constituents: 95% of urine is water, with the remainder (5%) comprising:
    • Urea
    • Uric acid
    • Creatinine
    • Mineral salts
    • Various pigments
    • Sugar
Clinical Significance of Urine Composition
  • The presence of excess sugar in urine can indicate conditions such as diabetes.

Kidney Functionality

  • Filtration Capacity: Each kidney can filter approximately 150 quarts of liquid daily, which results in the production of 1.5 to 2 quarts of urine, assuming adequate water intake is maintained.

Adrenal Glands

  • Each kidney is capped with adrenal glands, which perform vital functions that are discussed further in the context of the endocrine system.

Summary

To summarize, the main purpose of the urinary system is blood purification. It filters out toxins, excess sugars, and salts, along with other unnecessary substances. The principal anatomical components include two kidneys, two ureters, one bladder, one urethra, and the urethral meatus. The kidneys are subdivided into the cortex and medulla, with thousands of microscopic nephrons located in the cortex. Adequate water consumption is essential for optimal kidney and urinary system function.