Urinary System 2 Flashcards
Filtration membrane:
Prevents blood cells and large proteins from passing
Fenestrated endothelium
Filtration membrane: Blocks large, negatively charged ions
Basement membrane
Filtration membrane: allow water, glucose, ions and small molecules to pass
Filtration slits
Determines the direction and amount of filtrate produced
Net Filtration Pressure
Normal NFP amount
10mmHg
Formula for NFP
NFP = GBHP - (CHP + BCOP)
normal:
10 = 55 - (15 +30)
Percentage of renal plasma flow that becomes filtrate
Filtration fraction - typically 16-20%
The amount of filtrate formed per minute in all renal corpuscles, normally 105-120 mL/min.
Glomerular Filtration Rate (GFR)
Importance of Maintaining GFR: Too high or too low
Too high: Needed substances may not be reabsorbed and are lost in urine.
Too low: Wastes are not adequately removed from blood.
3 Modes for Regulation of GFR
- Renal autoregulation
- Neural regulation
- Hormonal regulation
Adjusts blood flow locally via the myogenic mechanism and tubuloglomerular feedback.
Renal autoregulation
Sympathetic nervous system adjusts GFR, especially in emergencies.
Neural regulation
Involves Angiotensin II and Atrial Natriuretic Peptide (ANP).
Hormonal regulation
Movement of solutes and water from renal tubules back into the blood (peritubular capillaries or vasa recta).
Reabsorption
Transfer of substances (wastes, toxins, excess ions) from blood into the tubules for excretion
Secretion
Reabsorption dominates:
100% of glucose and amino acids.
65% of water, sodium, potassium.
85-90% of bicarbonate (HCO₃⁻).
Proximal Convoluted Tubule (PCT):
Reabsorbs 15% of water (permeable to water, but not solutes).
Nephron Loop Descending limb
Reabsorbs Na⁺, K⁺, Cl⁻ through active transport.
Nephron Loop Ascending limb
Reabsorbs Ca²⁺ (regulated by PTH).
Reabsorbs small amounts of water, Na⁺, and Cl⁻.
Early DCT
Final adjustments depend on body needs:
Principal cells: Reabsorb Na⁺ and water (regulated by aldosterone and ADH).
Intercalated cells: Regulate pH by secreting H⁺ or reabsorbing bicarbonate (HCO₃⁻).
Secrete urea and K⁺.
Late DCT and Collecting Duct
Increases water reabsorption by stimulating aquaporins in collecting ducts.
Antidiuretic Hormone (ADH)
Increases Na⁺ reabsorption and K⁺ secretion.
Aldosterone
Increases Ca²⁺ reabsorption in the early DCT.
Parathyroid Hormone (PTH):
Inhibits Na⁺ reabsorption, leading to more water and Na⁺ excretion.
Atrial Natriuretic Peptide (ANP)