Urinary System Anatomy and Nephron Structure

Urinary System Anatomy

• Diagram 1: Anatomy of the Urinary System

  • Aorta
  • Renal vein: drains into the inferior vena cava.
  • Ureters: coming from the hilum.
  • Urinary bladder: ureters drain urine into the bladder.
  • Urethra: from the bladder to the outside of the body.

• Diagram 2: Kidney Structure

  • Renal capsule: surrounds the kidney.
  • Renal cortex: outer region of the kidney.
  • Renal medulla: inner region of the kidney, composed of renal pyramids (triangles).
  • Renal pyramids.
  • Renal columns: extensions of the cortex between the renal pyramids.
  • Renal papillae: outer region of the renal pyramids, where urine is collected.
  • Urine flow:
    • Renal papillae collect urine.
    • Minor calyx.
    • Major calyx.
    • Renal pelvis.
    • Ureter.

• Left kidney is slightly superior to the right kidney due to the liver.

Renal Blood Vessels

• Renal artery: enters each kidney through the hilum and branches into smaller branches.
  • Interlobular artery.
  • Arcuate artery.
  • Cortical radiate artery.
  • Afferent arteriole: blood supply that goes inside of the nephron.
    • Nephron: functional unit of the kidney where blood is filtered.
  • Glomerulus: strainer that filters the blood inside the nephron.
  • Efferent arteriole: carries the filtered blood away from the glomerulus.
  • Peritubular capillaries.

Nephron Blood Vessels

• Renal artery branches to form the afferent arteriole, which supplies blood to the nephron.
• Afferent arteriole is the blood vessel that supplies blood inside the nephron.
• Mnemonic: A (afferent) is the first letter of the alphabet, E (efferent) for end.
• Glomerulus filters the blood.
• Efferent arteriole carries the blood away after filtration.
• Peritubular capillaries are located near the renal tubule.

Renal Corpuscle and Glomerulus

• Nephron parts:

  • Renal corpuscle.
  • Renal tubule.

• Afferent arteriole supplies blood to the glomerulus inside the renal corpuscle.

• Glomerulus: strainer that filters the blood.

• Urine is formed and moves into the renal tubule.

• Remaining filtered blood goes back via the efferent arteriole.

• Efferent arteriole carries blood after filtration.

Peritubular Capillaries

• Afferent arteriole supplies blood to the glomerulus for filtration.
• Glomerulus is the site of blood filtration (strainer).
• Efferent arteriole carries the remaining blood.
• Peritubular capillaries surround the renal tubule, providing blood supply for reabsorption and secretion processes.

Nephron Structure

• Millions of nephrons are in each kidney.

• Nephron structure:

  • Renal corpuscle.
  • Renal tubule.

• Renal corpuscle:

  • Glomerulus: coiled structure for filtration; first step in urine formation.
  • Glomerular capsule (Bowman's capsule): receives the filtrate (urine).

• Renal tubule: divided into three parts:

  • Proximal convoluted tubule (proximal tubule): nearest to the renal corpuscle.
  • Loop of Henle: ascending and descending portions.
  • Distal tubule: farthest from the renal corpuscle.

• Proximal vs. Distal: Proximal is near, distal is away from the corpuscle.

Urine Formation and Flow

• Renal corpuscle:
  • Glomerulus: site of blood filtration; urine formation begins here.
  • Glomerular capsule: surrounds the glomerulus.
• Renal tubule:
  • Proximal tubule.
  • Loop of Henle (nephron loop): descending and ascending limbs.
  • Distal tubule.
• Collecting ducts: several distal tubules drain into the collecting ducts, which collect urine.
• Urine flow:
  • Collecting ducts drain into the:
  • Renal papilla (at the end of the pyramids).
  • Minor calyx.
  • Major calyx.
  • Renal pelvis.
  • Ureter.
  • Urinary bladder.
  • Urethra.

Microscopic Kidney Structure

• Renal cortex: contains many renal corpuscles (appears dotted when stained).
• Renal medulla: contains renal tubules (appears as lines/tubes when stained).

Urine Formation Steps

• Glomerulus: first step; blood is filtered.
• Glomerular capsule: filtrate moves here from the glomerulus.
• Renal tubule:
  • Proximal tubule.
  • Loop of Henle (descending and ascending limbs).
  • Distal tubule.
• Collecting ducts: distal tubules drain into collecting ducts.
• Urine flow:
  • Collecting ducts to renal papilla.
  • Minor calyx.
  • Major calyx.
  • Renal pelvis.
  • Ureter.
  • Bladder.
  • Urethra (to the outside of the body).

Review of Renal Flow and Formation

• Urine formation starts in the glomerulus (blood filtration).
• Urine moves from the glomerulus to the glomerular capsule.
• From the glomerular capsule to the proximal tubule.
• Loop of Henle (descending and ascending).
• Distal tubule.
• Collecting duct (distal tubules merge).
  • Renal papilla.
  • Minor calyx.
  • Major calyx.
  • Renal pelvis.
  • Ureter.
  • Bladder.
  • Urethra.