Urinary System Overview Quiz

Urinary System Overview

• Kidneys are major excretory organs, receiving 25% of cardiac output.
• They produce urine, a fluid containing water, ions, and small soluble substances.

Urinary Tract Components

• Ureters: Receive urine from kidneys, conduct it to the bladder via gravity and peristalsis.
• Urinary Bladder: Receives and stores urine; contraction of bladder wall muscle drives urination.
• Urethra: Conducts urine from bladder to outside the body; in males, it also carries semen.

Urinary System Functions

• Regulate blood ions: Calcium, sodium, potassium, chloride, and phosphate.
• Regulate blood pH: Excrete H+ and conserve HCO3- (bicarbonate).
• Regulate blood volume: Excrete or conserve water (H2O).
• Regulate blood pressure: Secrete renin, increasing renin leads to increased blood pressure.
• Regulate blood glucose: Site of gluconeogenesis (creation of new glucose).
• Maintain blood osmolarity: Regulate water and solute loss, maintaining a concentration of 300 mOsm/L.
• Produce hormones: Calcitriol and erythropoietin (EPO).
• Excrete waste: Ammonia, urea, bilirubin, creatinine, uric acid, drugs, and environmental toxins.

Kidney Anatomy

• Location: Located retroperitoneally, between body wall muscles and parietal peritoneum, on either side of the vertebral column, with the left kidney generally slightly superior due to liver position.
• Protection: Protected by visceral organs (anteriorly), body wall musculature, and ribs (11 & 12 posteriorly/laterally).
• Connective Tissue Layers: Surrounded and supported by three layers of connective tissue:
  • Renal (fibrous) capsule: Innermost, collagen fibers.
  • Perirenal fat (adipose capsule): Middle, thick layer of adipose tissue.
  • Renal fascia: Outermost, dense fibrous layer anchoring kidney to surrounding structures.
• Hilum: Medial indentation, the entry/exit point for renal artery, nerves, renal vein, and ureter.
• Renal sinus: Internal cavity, lined by fibrous capsule; filled with fat for protection.
• Color: Reddish-brown.

Kidney Internal Anatomy

• Parenchyma: Divided into outer cortex and inner medulla.
• Renal Cortex: Outer region, lighter red, site of renal corpuscles, blood filtration, and initial urine formation.
• Renal Medulla: Inner region, darker brown, contains renal pyramids, ending in renal papillae which face the hilum.
• Renal Columns: Extensions of cortex into medulla, separating renal pyramids.
  • Nephron loop
  • Papillary ducts
  • Collecting ducts
• Renal Lobe: Pyramid, overlying cortex, & adjacent renal columns. Each kidney has 6-18.

Pathway of Tubes

• Minor calyx: Collects urine from a single kidney lobe.
• Major calyx: Formed from fusion of 4-5 minor calyces.
• Renal pelvis: Funnel-shaped structure collecting urine from major calyces, continuous with the ureter.

Nephrons

• Functional Unit: Nephrons are the functional units of the kidney, producing urine by removing waste and excess substances from the blood.
• Number: 1 million nephrons per kidney.
• Irreplaceable: Once damaged beyond repair, nephrons cannot be replaced.
• Kidney Capacity: One kidney can filter at approximately 80% the rate of two kidneys.

Blood Supply to the Kidney

• Renal Artery: Primary blood supply to the kidney.
• Branches: Leads to segmental arteries, interlobar arteries, arcuate arteries, cortical radiate arteries, and afferent arterioles that supply the glomerulus within each nephron – delivering blood to nephrons for filtration.
• Efferent Arterioles: Carry blood leaving glomerulus to peritubular capillaries and vasa recta.
• Venous System: Blood from glomerulus drains into efferent arterioles, then to peritubular capillaries or vasa recta, then to cortical radiate veins, arcuate veins, interlobar veins, and finally the renal vein. The renal veins drain into the inferior vena cava.

Blood Flow Through Nephons

• Afferent Arteriole: Supplies blood to the individual nephron.
• Glomerulus: Inside the renal corpuscle, site of filtration.
• Efferent Arteriole: Carries blood from glomerulus to peritubular capillaries.
• Peritubular Capillaries (cortical nephrons): Surround the entire renal tubule, absorbing water and solutes absorbed by nephron, secreting other substances.
• Vasa Recta (juxtamedullary nephrons): Long, straight capillaries parallel to the nephron loop, responsible for water and solute transport within the renal medulla.

Nerve Supply to the Kidney

• Sympathetic Nervous System: Innervates the kidneys, mainly to control vasodilation/vasoconstriction of renal arteries, regulating blood flow to kidneys.
• Effect on Blood Flow: Increased sympathetic activity generally leads to water retention and increased blood pressure. More sympathetic activity = more filtration and reduced blood flow.

Test your knowledge on the structure and function of the urinary system. This quiz covers key components such as the kidneys, ureters, bladder, and urethra, along with their critical roles in regulating various aspects of blood chemistry and pressure. Challenge yourself to master the essentials of this vital body system.