renal physio

• Components of the urinary system

  • 2 Kidneys
  • 2 Ureters
  • 1 Urinary Bladder
  • 1 Urethra
  • Total: 6 Structures
• Characteristics of the urinary system

  • Color
  • Shape
  • Weight
  • Size
  • Length
  • Width
  • Thickness
  • Anatomical position
  • Bony Landmark
  • Peritoneal Cavity
• Functions of the kidneys

  • Production of hormones: Calcitriol, Erythropoietin, Renin
  • Excretion of waste products, by-products of amino acids, by-product of RBC recycling, by-product of skeletal muscles, by-product of purines
  • Regulation of blood pH
  • Regulation of blood glucose
  • Regulation of blood volume
  • Regulation of blood ionic composition
  • Regulation of blood pressure
• Renin-Angiotensin-Aldosterone System


  1. Detected by Baroreceptors/chemoreceptors

  2. Release Renin

  3. Conversion of Angiotensinogen to Angiotensin I

  4. Angiotensin I travels to the Lungs

  5. ACE in the lungs convert AI to AII

  6. Angiotensin II causes Vasoconstriction, Increased BP, Activation of production of Aldosterone

  7. Aldosterone causes reabsorption of Na and Water
• External anatomy of the kidneys

  • Hilum/Hilus - area where ureter, blood vessels, nerves and lymphatics of kidney enter
  • Renal capsule
  • Renal Fat pad/Adipose Capsule
  • Renal fascia
• Internal anatomy of the kidneys

  • Renal Cortex
  • Juxtamedullary
• Drainage of the kidneys

  1. Collecting Duct

  2. Renal Papilla

  3. Minor Calyx

  4. Major Calyx

  5. Renal Pelvis

  6. Ureters

  7. Urinary Bladder

  8. Urethra
• Blood flow in the kidneys

  1. Renal Artery

  2. Segmental Artery

  3. Interlobar Artery

  4. Arcuate Artery

  5. Interlobular Artery/Cortical Radiate Artery

  6. Afferent Arteriole

  7. Glomerolus

  8. Efferent Arteriole

  9. Peritibular Artery
• Ureters


  • Passageway of urine from kidneys to urinary bladder for storage
• Urinary Bladder


  • Pear shaped, located at the back of pubic symphysis
  • Normal Capacity: 700-800 mL
  • Micturition via micturition reflex, triggered when 450-500 mL
  • Micturition Centers: S2-S3, both parasympathetic and sympathetic
• Micturition Reflex Mechanism


  1. Stretch receptors on bladder

  2. S2-S3 => Brain

  3. Parasympathetic response

  4. Sympathetic response
• Urethra


  • Passageway of urine from bladder to the external environment
  • Size: F= M=
• Nephron


  • Functional unit
  • Urine formation
  • Filters blood
  • Reabsorbs important substances
  • Excretes waste products
• Nephron types


  • Cortical Nephrons (80-85%)
  • Juxtamedullary Nephrons (15-20%)
• When nephrons die, new cells will not regenerate
• Parts of a nephron

  • Renal Corpuscle
  • Glomerulus
  • Glomerular Capsule
  • Proximal Convoluted Tubule
  • Descending Loop of Henle
  • Ascending Loop of Henle
  • Distal Convoluted Tubule
  • Collecting Duct
• Proximal Convoluted Tubule


  • Simple cuboidal epithelium
  • Microvilli for reabsorption
  • Not selective
• Descending Loop of Henle

  • Simple squamous epithelium
  • Selective to H2O
  • One-way ticket
• Ascending Loop of Henle

  • Simple columnar epithelium
  • Juxtraglomerular apparatus
  • Macula Densa compact epithelium where glomerular cells are located
  • JG cells secrete renin
• Distal Convoluted Tubule


  • Principal cells with receptors for ADH/vasopressin and Aldosterone
  • Intercalated cells make Na-K pump viable
  • Responsible for dilution of DCT
• Glomerular Filtration


  • Daily Volume of Filtrate: 150-180 L/day
  • 99% reabsorbed, 1% urine
  • Total Urine per day: 1-2L
• Factors governing glomerular filtration

  • Glomerular Blood Hydrostatic Pressure (55mmHg)
  • Capsular Hydrostatic Pressure (15mmHg)
  • Blood Colloid Osmotic Pressure (30mmHg)
• Net Filtration Pressure


  • Formula: GBHP-(CHP+BCOP)
  • 55-(15+30) = 10mmHg
• Glomerular Filtration Rate (GFR)


  • Normal Values: M: 125mL, F: 105mL
  • Kidney Failure: NFP decreased, GBHP<CHP+BCOP
• Urine Formation


  1. PCT - 65% of H2O reabsorbed, 100% glucose reabsorbed, 50% urea reabsorbed, 80-85% bicarbonates reabsorbed

  2. DLOH - H2O reabsorbed

  3. ALOH - Solutes reabsorbed
• Urine Concentration with and without ADH


  • Most concentrated: Collecting Duct, End of Thin Descending Loop of Henle
  • Most diluted: Distal Convoluted Tubule, Thick Ascending Loop of Henle
• Characteristics of normal urine


  • Volume
  • Color
  • pH: 4.2-8.0
  • Composition
• Blood testing for kidney evaluation

  • BUN: normal 7-20mg/dl
  • Plasma Creatinine: normal 130mmol
  • Plasma Clearance: (n)= 0% glucose
• Urinary tract conditions


  • UTI (2nd most common bacterial infection)
  • Incontinence: Stress, Urge, Overflow, Functional
  • Chronic Kidney Disease (CKD), Dialysis: Hemodialysis, Peritoneal Dialysis
• UTI


  • Incidence: F>M
  • Manifestations: fever, chills, malaise, dysuria, enuresis, frequent urination, urinary urgency, nocturia, dyspareunia
  • Types: Upper UTI (kidneys and ureters), Lower UTI (bladder and urethra)