urinary system chapter 27

• Urinary System

  General structure and functions
• Functions of the Urinary System


  • Storage of urine
  • Excretion of urine
  • Regulation of blood volume
  • Regulation of ion levels
  • Regulation of erythrocyte production
  • Regulation of acid-base balance
• Kidneys


  Location: retroperitoneal, superior pole at T12, inferior pole at L3
• Kidneys


  • Each kidney has a hilum (concave medial border where vessels, nerves, and the ureter connect)
  • Continuous with an internal space called the renal sinus
• Tissue layers surrounding each kidney


  • Fibrous capsule
  • Perinephric fat
  • Renal fascia
  • Paranephric fat
• Renal Cortex and Medulla

  Kidney is divided into an outer renal cortex and an inner renal medulla
• Renal Columns


  Extensions of renal cortex that project into medulla and subdivide it into renal pyramids (8-15)
• Renal Papilla


  Apex (tip) of a renal pyramid that projects into a minor calyx
• Urine Collection


  1. Minor calyces fuse to form major calyces

  2. Major calyces fuse to form the renal pelvis

  3. Renal pelvis collects urine and transports it into the ureter
• Kidney Lobes


  • A kidney has 8 to 15 renal lobes
  • Each lobe consists of a renal pyramid and cortical tissue immediately surrounding the pyramid
• Blood Supply to the Kidney


  1. Renal arteries branch into segmental arteries

  2. Segmental arteries branch into interlobar arteries

  3. Interlobar arteries branch into arcuate arteries

  4. Arcuate arteries give off interlobular arteries

  5. Interlobular arteries extend afferent arterioles that enter renal corpuscles
• Glomerulus


  A tuft of capillaries within the renal corpuscle where plasma is filtered
• Blood Drainage from the Kidney

  1. Efferent arterioles branch into peritubular capillaries and vasa recta

  2. Peritubular capillaries and vasa recta drain into interlobular veins

  3. Interlobular veins merge to form arcuate veins

  4. Arcuate veins merge to form interlobar veins

  5. Interlobar veins merge to form the renal vein
• Renal Plexus


  Mass of sensory and autonomic fibers that innervate the kidney
• Nephron


  The functional filtration unit of the kidney, consisting of a renal corpuscle and a renal tubule
• Types of Nephrons


  • Cortical nephrons (85% of total)
  • Juxtamedullary nephrons (15% of total)
• Urine Formation


  1. Filtration

  2. Tubular reabsorption

  3. Tubular secretion
• Renal Corpuscle


  Bulbous part of the nephron composed of a glomerulus and a glomerular capsule
• Proximal Convoluted Tubule


  Begins at the tubular pole of the renal corpuscle, with walls composed of simple cuboidal epithelium with tall microvilli
• Nephron Loop


  Extends from the cortex into the medulla, containing a descending limb and an ascending limb
• Distal Convoluted Tubule


  Sits in the renal cortex, secretes K+ and H+ and responds to ADH and aldosterone
• Juxtaglomerular Apparatus


  Collection of structures associated with the nephron that help regulate blood pressure
• Components of the Urinary Tract


  • Ureters
  • Urinary bladder
  • Urethra
• Ureters


  Fibromuscular tubes that conduct urine from the kidneys to the urinary bladder
• Urinary Bladder


  Main function is storage of urine, located posterior to the pubic symphysis
• Tunics of the Urinary Bladder


  • Mucosa
  • Submucosa
  • Muscularis
  • Adventitia
• Micturition


  The expulsion of urine from the bladder, controlled by the micturition reflex
• Urethra


  Fibromuscular tube that conducts urine from the bladder to the exterior of the body
• Segments of the Male Urethra


  • Prostatic urethra
  • Membranous urethra
  • Spongy urethra
• Urinary tract infections are more common in females due to a shorter urethra
• Kidney infections can spread from urinary tract infections
• Renal calculi (kidney stones) are crystallizations of calcium, magnesium or uric acid salts, usually less than 5 mm in diameter