URINARY

• Kidney


  • Paired, reddish brown, retroperitoneal
  • Coverings: Renal capsule, perirenal fat, renal fascia, pararenal fat
  • Continuous with transversalis fascia

  
• Renal cortex


  Outer part of the kidney
• Renal medulla


  Inner part of the kidney

  
• Renal pelvis


  Union of major calyces

  
• Major calyx


  Union of minor calyces
• Nephron


  Structural and functional unit of the kidney, 1 million per kidney

  
• Parts of a nephron

  • Glomerulus
  • Bowman's capsule
  • Proximal convoluted tubule
  • Loop of Henle
  • Distal convoluted tubule

  
• Bowman's capsule


  • Inner visceral layer composed of podocytes, Parietal layer composed of simple squamous epithelium

  
• Renal (Malpighian) corpuscle


  Glomerulus plus Bowman's capsule

  
• Components of the juxtaglomerular apparatus

  • JG cells
  • Macula densa
  • Mesangial cells
• Mechanism of urine formation

  1. Glomerular filtration

  2. Tubular reabsorption

  3. Tubular secretion

  
• Glomerular filtration


  • Acts as a filter, 1/5 of blood flowing through the kidneys is filtered from the glomeruli, Through filtration membrane

  
• Pressures acting on the glomerulus

  • Glomerular hydrostatic pressure
  • Glomerular osmotic pressure
  • Capsular hydrostatic pressure
• Net Filtration Pressure


  Force responsible for filtrate formation, Calculated as glomerular hydrostatic pressure - (glomerular oncotic pressure + capsular hydrostatic pressure)
• Glomerular Filtration Rate


  Amount of filtrate formed per minute, Equal to 125ml/min, Directly proportional to the net filtration pressure
• Tubular reabsorption


  The process of returning needed substances from the filtrate to the capillary blood, Can be active or passive

  
• PCT is the most active, 80% of filtrate, nutrients, water and Na, the bulk actively transported ions are reabsorbed here
• Reabsorption in DCT tubule and collecting duct is controlled by Aldosterone and antidiuretic hormone

  
• Tubular secretion


  Adding substance to the filtrate from blood or tubular cells, Can be active or passive, Important in eliminating urea, excess ions, drugs, and maintaining acid-base balance

  
• Urine osmolarity ranges from 50-1200mosm
• Hyperosmolarity of the medullary fluid ensures that the urine reaching the DCT is hypo-osmolar

  
• In the absence of ADH, urine becomes diluted

  
• When Blood ADH increases, the permeability of DCT and collecting duct to water increases

  
• Renal Clearance


  The rate at which the kidneys clear the plasma for a particular solute

  
• Ureter


  • 10 inches long muscular tube, 3 anatomical constrictions: at the uretero-pelvic junction, where iliac vessels cross the ureter, where it joins the urinary bladder

  
• Urinary bladder


  • Hollow muscular organ, Wall consists of detrusor muscle, Inner trigone occupied by ureteral orifices and urethral orifice

  
• Parts of the male urethra

  • Prostatic
  • Membranous
  • Penile
• Female urethra


  4 cm, opens into vestibule
• The kidneys are located on either side of the vertebral column, just below the diaphragm.