Topic 7: Glomerular Filtration and Renal Bllod Flow Flashcards
Three renal processes
- Glomerular filtration (From glomerular capillaries to Bowman’s capsule) 2. Tubular reabsorption (From renal tubules to peritubular capillaries) 3. Tubular secretion (From peritubular capillaries to renal tubules)
Excretion equation?
Excretion = Filtration–Reabsorption + Secretion
Excretion Rate: Filtration Rate
Excretion = Filtration Waste products (creatinine)
Excretion Rate: Filtration, partial reabsorption
Excretion = Filtration–Reabsorption Electrolytes (sodium, chloride)
Excretion Rate: Filtration, complete reabsorption
Nothing excreted Nutritional substances (amino acids, glucose)
Excretion Rate: Filtration secretion
Excretion = Filtration + Secretion (no reabsorption) Organic acids & bases
Increased sodium; increased filtration; decreased reabsorption all equal what?
increased excretion
Small changes in filtration and/or reabsorption will produced significant changes in what?
excretion rate
High Filtration Rate allows what? (3)
-Allows rapid removal of waste products -Allows multiple passes of the blood volume through the kidneys each day -Allows rapid and precise control of body fluid volume and composition
GFR average amount
180 L/day (125 mls/minute) versus 3 to 4 liters of plasma volume
How many times is the plasma volume completely filtered on average each day?
plasma volume 6 times each day
Renal Blood Flow average mls/min
1100 mls/minute RBF
Filtration Fraction = equation?
GFR / Renal Plasma Flow
Filtration Fraction average %
20%
Normal reabsorption ≈
178.5 Liters/day (123 mls/minute)
Normal urine output ≈
180–178.5 ≈ 1.5 Liters/day
Normal urine output ≈
125-123 ≈ 2 mls/minute
Glomerular Capillary Membrane layers?
Endothelial cell layer Basement membrane layer Epithelial cell layer
Epithelial Cell Layer consists of what?
Foot like processes - Podocytes: surround outer surface of basement membrane, that have slit pore-gaps, which glomerular filtrate moves through
Endothelial cell layer has what?
perforated by thousands of fenestrations (small holes) Protein passage prevented by negative charge on surface of endothelial cells
Basement membrane layer allows what? and prevents what?
allows movement of water and small solutes Protein passage prevented by proteoglycan mesh and negative charge
Epithelial lay is not continuous bc of what?
-Slit pores present between adjacent podocytes–allow free movement of water and small solutes -Negative charge of surrounding epithelial cells hinders protein filtration
Overall pore size is approximately what?
Overall pore size approximately 8 nanometers (80 angstroms)
Filterability of 0.75 means what?
filtered 75% as quickly as water Filtrate concentration <plasma></plasma>
Albumin size compared to pore size?
Albumin smaller than pore size (6 nm vs. 8 nm) but negative charge prevents passage
Dextrans
Polysaccharides that can be made with specific charges - can be neg or positive to test things
Renal diseases where the negative charge of basement membrane is lost before any histological changes are seen has an early indicator of what?
Proteinuria or Albuminuria appearance of albumin in urine is an early indicator
Graph
Positivly charged ions are much easier to be passed through bc kidney layers have so many negative charges
Negatively charged large molecules are filtered less easily than positive charged molecules or equal Molecular Weight
