Urinary System Overview

Functions of the Urinary System

  • Eliminates Metabolic Waste

    • Removes CO₂, extra water, and nitrogenous wastes

  • Regulates Blood pH

    • Maintains normal pH levels in the body

  • Regulates Blood Volume and Fluid Balance

    • Ensures appropriate levels of fluid in the body

  • Regulates Blood Pressure

    • Helps maintain optimal blood pressure levels

  • Maintains Homeostasis

    • Supports stable conditions within the body

Structure of the Kidney

  • Kidney Anatomy

    • Two bean-shaped organs located in the lower back, above the pelvis
    • Convex side faces laterally, concave side faces medially
    • Renal Hilum: Indentation allows passage for renal vessels, nerves, and ureters

  • Sections of the Kidney

    • Renal Cortex: Smooth outer portion containing blood vessels and collecting ducts
    • Renal Medulla: Innermost area containing renal pyramids and tubules for urine transport
    • Renal Pelvis: Enlarged upper end of ureter with cup-like calyces for urine collection

Nephron

  • Functional Unit of the Kidney

    • Filters blood, selectively reabsorbs useful substances, and secretes wastes into urine

  • Components of Nephron

    • Tubular Component:
    • Composed of Bowman's capsule, PCT (proximal convoluted tubule), Loop of Henle, DCT (distal convoluted tubule), and collecting duct
    • Vascular Component:
    • Composed of renal artery, afferent/efferent arterioles, glomerulus, peritubular capillary bed, and renal vein

Filtering of Blood

  • Process

    • Blood enters kidney via renal artery and branches into afferent arterioles leading to the glomerulus (capillary bed)
    • Glomerular Filtration:
    • Pressure difference between afferent and efferent arterioles facilitates filtration into Bowman's capsule
    • Waste materials filtered into tubular components

  • Tubular Reabsorption and Secretion

    • Reabsorption:
    • Selective reabsorption of water, glucose, ions, and amino acids back into blood
    • Key areas: PCT (glucose and amino acids), Loop of Henle (water and salts), DCT (hormone-regulated permeability)
    • Secretion:
    • Unwanted substances and excess materials are secreted from blood into urine

Regulation of Blood Pressure

  • Juxtaglomerular Apparatus:
    • Monitors blood pressure; regulates filtration rate in response to low blood pressure or ion concentration
    • Renin-Angiotensin System:
    • Renin secretion increases blood pressure via vasoconstriction and aldosterone production

Common Disorders of the Urinary System

  • Urinary Tract Infection (UTI):

    • Infection/inflammation commonly in women; symptoms include burning on urination, frequent/urgent urination, fever

  • Cystitis:

    • Inflammation of the urinary bladder; usually results from fecal bacteria leading to painful urination and discomfort

  • Incontinence:

    • Involuntary passage of urine; types include stress incontinence (post-childbirth), overflow, and urge incontinence

  • Kidney Stones:

    • Formed from excess calcium or uric acid; may cause severe pain and requires treatment if large

  • Glomerulonephritis:

    • Inflammation of glomeruli leading to dark or bloody urine; can indicate renal failure

  • Pyelonephritis:

    • Kidney infection; symptoms include back pain, fever, chills, treatable with antibiotics

Treatment for Kidney Issues

  • Organ Compatibility:

    • Humans can live with one kidney; organ donation can involve living or deceased donors

  • Dialysis Treatment:

    • Artificially removes waste and regulates blood pressure; does not cure but supports life until transplantation or recovery
    • Types include internal (peritoneal) or external (hemodialysis) dialysis.