Anatomy & Physiology

• Kidney blood supply


  1. Single renal artery arises from aorta

  2. Divides into 5 segmental arteries

  3. Segmental arteries branch into lobular arteries

  4. Lobular arteries branch into interlobular arteries

  5. Interlobular arteries branch into afferent arterioles
• Blood flow through nephron


  1. Blood flows into glomerulus through afferent arteriole

  2. Blood flows out of glomerulus through efferent arteriole

  3. Efferent arteriole forms peritubular capillary network

  4. Peritubular capillaries rejoin to form venous channels
• Afferent and efferent arterioles


  Regulate glomerular capillary pressure by selectively dilating or constricting
• Urine formation


  1. Filtration of blood by glomerulus

  2. Tubular reabsorption of electrolytes and nutrients

  3. Tubular secretion of waste materials
• Glomerular filtrate


  Ultrafiltrate of blood that moves into tubular segments of nephron
• Urine production


  1. Filtration

  2. Tubular reabsorption

  3. Tubular secretion

  4. Concentration in collecting tubules

  5. Elimination via renal pelvis, ureter, bladder, urethra
• Kidney function


  Filtering blood and selectively reabsorbing needed materials while excreting waste
• Nephron


  Functional unit of kidney, composed of glomerulus and tubular component
• There are 1.25 million nephrons per kidney
• If stretched out, all nephrons would be 85 miles in length
• Cortex and medulla of kidney


  • Cortex is outer ring, medulla is inner region
• Urea production


  1. Amino acids broken down in liver

  2. Ammonia converted to urea

  3. Urea transported in blood to kidneys
• Urine is concentrated urea, the nitrogenous waste product
• Hydrogen ions are also excreted in urine
• Filtration in Bowman's capsule

  Blood components smaller than gaps in podocytes are filtered into tubule
• Reabsorption in proximal convoluted tubule

  Water, nutrients, ions reabsorbed back into blood
• Reabsorption in loop of Henle

  1. Water, sodium, chloride reabsorbed

  2. Hydrogen ions, urea continue
• Reabsorption and secretion in distal convoluted tubule and collecting duct


  1. Water reabsorption regulated by hormones

  2. Hydrogen ions secreted
• Parathyroid hormone regulates calcium reabsorption
• Loop of Henle


  1. Water continues on

  2. More water reabsorbed back into blood

  3. Sodium ions continue on

  4. Chloride ions continue on

  5. Hydrogen ions continue on

  6. Urea continues on
• Only water is being reabsorbed in the descending limb of the loop of Henle
• Ascending limb of loop of Henle


  1. Water continues on

  2. Many sodium ions reabsorbed into blood

  3. Chloride ions reabsorbed

  4. Hydrogen ions stay in

  5. Urea stays in
• Proximal convoluted tubule and collecting duct


  1. Water continues on

  2. Controlled by hormones

  3. Water reabsorption based on blood pressure

  4. Antidiuretic hormone controls water reabsorption

  5. Aldosterone controls sodium reabsorption and potassium secretion
• Hydrogen ions and urea continue towards renal pelvis and bladder
• Antidiuretic hormone present


  More water reabsorbed into blood
• Aldosterone present


  Sodium reabsorbed, potassium secreted
• Decrease in renal perfusion


  Kidney releases renin
• Renin-angiotensin-aldosterone system


  1. Renin converts angiotensinogen to angiotensin 1

  2. Angiotensin 1 converted to angiotensin 2 in lungs

  3. Angiotensin 2 increases sympathetic activity, sodium/chloride reabsorption, potassium excretion

  4. Angiotensin 2 stimulates pituitary to release antidiuretic hormone
• Blood pressure medications often target the renin-angiotensin-aldosterone system
• Urine analysis can be used to monitor endocrine hormones and drug metabolites
• Kidneys


  • Shaped organs located close to the back
  • Receive blood flow from renal artery branching off abdominal aorta
  • Blood passes into vena cava via renal vein
  • Ureter allows flow of urine to bladder
  • Functional mass divided into cortex and medulla
• Nephron


  1. Renal corpuscle with Bowman's capsule and glomerulus

  2. Proximal tubule

  3. Descending limb of Henle's loop

  4. Ascending limb of Henle's loop

  5. Distal convoluted tubule

  6. Collecting duct
• Filtrate


  Filtered blood that passes into the tubule
• Proximal tubule


  1. 65% of filtrate reabsorbed back into blood

  2. Sodium reabsorption mediated by sodium-coupled exchanges

  3. Water reabsorption through aquaporin 1 & 7 channels
• Descending limb of Henle's loop

  High water permeability, low sodium permeability
• Ascending limb of Henle's loop


  Sodium, potassium and chloride transported into cell via co-transporter
• Distal convoluted tubule


  1. 5-10% of sodium reabsorption

  2. Low water permeability
• Collecting duct


  1. Fine tuning of sodium reabsorption

  2. Water and sodium movement regulated by vasopressin and aldosterone