urinary

• General functions of the urinary system

  • Filtration
  • Reabsorption
  • Secretion
  • Excretion
• Major parts of the urinary system

  • Right & Left Kidneys
  • Right & Left Ureters
  • Urinary Bladder
  • Urethra
• Functions of the kidneys

  • Regulation of blood ionic composition
  • Regulation of blood pH
  • Regulation of blood volume
  • Regulation of blood pressure
  • Maintenance of blood osmolarity
  • Production of hormones
  • Regulation of blood glucose
  • Excretion of wastes and foreign substances
• Kidneys


  • 2 kidneys
  • Length: 10-12 cm (4-5")
  • Width: 5-7 cm (2-3")
  • Thickness: 3 cm (1")
  • Mass: 135-150 g (4.5-5 oz)
  • Bean-shaped organs
  • Located above the waist
  • Retroperitoneal
  • Between T12 & L3
  • Right kidney is slightly lower
• Radiographic correlation: normal location of kidneys
• External anatomy of the kidneys

  • Renal hilum
  • Renal fascia
  • Adipose capsule
  • Renal capsule
• Renal hilum


  Indentation near the center of the concave border where the ureter emerges from the kidney along with the blood vessels, lymphatic vessels, and nerves
• Renal fascia


  Superficial layer, thin layer of dense irregular connective tissue
• Adipose capsule


  Middle layer, mass of fatty tissue surrounding the renal capsule
• Renal capsule


  Deep layer, smooth, transparent sheet of irregular connective tissue continuous up to the outer coat of the ureter
• Internal macroscopic anatomy of the kidneys

  • Renal parenchyma
  • Renal cortex
  • Renal medulla
• Zones of the renal cortex

  • Cortical zone (outer zone)
  • Juxtamedullary zone (inner zone)
• Parts of the renal medulla

  • Renal pyramids
  • Renal papilla
• Parts of the renal lobe

  • Fibrous capsule
  • Renal cortex
  • Renal medulla
• Parts of the renal pelvis

  • Minor calyx
  • Major calyx
  • Renal pelvis
• Renal sinus


  Vertical space or cleft in the hilum containing part of the renal pelvis, calyces, branches of renal blood vessels, and nerves
• Parts of the nephron

  • Renal corpuscle (glomerulus, glomerular capsule)
  • Renal tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule)
• Types of nephrons and their location

  • Cortical nephron
  • Juxtamedullary nephron
• Parts of the renal corpuscle

  • Glomerulus
  • Glomerular (Bowman's) capsule
• Glomerulus


  Tuft of capillaries associated with a renal tubule
• Glomerular (Bowman's) capsule


  Cup-shaped end of the renal tubule that surrounds the glomerulus, consisting of visceral and parietal layers
• Parts of the renal tubule

  • Proximal convoluted tubule
  • Loop of Henle (thin descending limb, thin ascending limb, thick ascending limb)
  • Distal convoluted tubule
• Proximal convoluted tubule


  First renal tubule segment, lined by brush border cells that reabsorb various substances and secrete others
• Loop of Henle


  Receives filtrate from the proximal convoluted tubule and passes it to the distal convoluted tubule, with a thin descending limb, thin ascending limb, and thick ascending limb
• Parts of the collecting system

  • Collecting tubules
  • Collecting ducts
  • Papillary ducts
• Collecting tubules


  Formed by the union of many renal tubules, each with its own opening into a minor calyx, reabsorbing and secreting various substances
• Flow of fluid through a cortical nephron

  • Glomerular (Bowman's) capsule
  • Proximal convoluted tubule
  • Descending limb of the nephron loop
  • Ascending limb of the nephron loop
  • Distal convoluted tubule (drains into collecting duct)
• Blood supply of the kidneys

  • Renal arteries
  • Segmental arteries
  • Interlobar arteries
  • Arcuate arteries
  • Cortical radiate (interlobular) arteries
  • Afferent arterioles
  • Efferent arterioles
  • Peritubular capillaries
  • Vasa recta
  • Cortical radiate (interlobar) veins
  • Arcuate veins
  • Interlobar veins
• Glomerular filtration, tubular reabsorption, and tubular secretion are key processes in the kidneys
• Peritubular capillaries


  Surround tubular parts of nephron in renal cortex
• Vasa Recta


  Supply tubular portions of nephron in renal medulla
• Renal veins

  • Cortical radiate (interlobar) veins
  • Arcuate veins
  • Interlebar veins
• Glomerular filtration


  In the glomerulus, blood plasma and dissolved substances (smaller than most proteins) get filtered into the glomerular capsule
• Tubular reabsorption


  All along the renal tubule and collecting duct, water, ions, and other substances get reabsorbed from the renal tubule lumen into the peritubular capillaries and ultimately into the blood
• Tubular secretion


  All along the renal tubule and collecting duct, substances such as wastes, drugs, and excess ions get secreted from the peritubular capillaries into the renal tubule. These substances ultimately make their way into the urine
• Glomerular filtration rate


  105-125 mL/min of fluid that is isotonic to blood
• Filtered substances


  Water and all solutes present in blood (except proteins) including ions, glucose, amino acids, creatinine, uric acid
• Reabsorption in proximal convoluted tubule

  • Water (65%)
  • Na (65%)
  • K (65%)
  • Glucose (100%)
  • Amino acids (100%)
  • Cr (50%)
  • HCO2 (80-90%)
  • Urea (50%)
  • Ca, Mg (variable)
• Secretion in proximal convoluted tubule

  • H+ (variable)
  • NH4+ (variable, increases in acidosis)
  • Urea (variable)
  • Creatinine (small amount)
• Reabsorption in early distal convoluted tubule

  • Water (10-15%)
  • Na+ (5%)
  • Cl- (5%)
  • Ca2+ (variable, stimulated by parathyroid hormone)