HUBS192 Lecture 32 - Renal Physiology: Glomerular Function Flashcards
what is the first part of the basic nephron processes?
filtration
what is ultrafiltration?
filtration in a very small area
how does the glomeruli select what to filtrate?
selects by size like a sieve
what does filtration at the nephron in the kidney create?
creates a plasma-like filtrate of the blood
what is the rate of filtration in the nephron in the kidney? (specific number)
takes place at a rate of 125mL/min (180L per day)
what 3 things determine renal filtration?
1) renal blood flow (how much blood goes into the kidney to be filtered)
2) filtration barrier (what are the layers of membranes/tissues that make up the filtration barrier)
3) driving forces (physics=pressure)
what controls the perfusion of the nephron?
the nephron controls its own perfusion through the distal convoluted tubule
how is the glomerulus supplied with blood for filtration?
the glomerulus has afferent and efferent arterioles supplying the glomerulus with blood for filtration
what is the percentage of cardiac output for renal blood supply to the kidney?
20-25% of cardiac output (CO)
what is the renal blood supply to the kidney per minute? (specific number)
1-1.2L per minute
what is the high renal blood flow for in the kidney?
high flow for filtration rather than metabolism
where does filtration take place?
filtration takes place in the glomerulus
what are the 4 components of the filtration barrier of the kidney?
1) fenestrated endothelium
2) basement membrane
3) podocytes with foot processes
4) filtration slits
what is the relationship between small substances and filtration?
small substances (low molecular mass) are free filtered
what is the relationship between large substances and filtration?
large substances (high molecular mass) are NOT filtered
what are the 3 driving forces of glomerular filtration?
1) forces / pressure gradients between glomerular capillary / capsular space
2) permeability of the glomerular capillary
3) surface area of glomerular capillary
what are the 4 forces (pressures) determining net filtration pressure?
1) glomerular hydrostatic pressure (GHP)
2) blood colloid osmotic pressure (BCOP)
3) capsular hydrostatic pressure (CsHP)
4) capsular colloid osmotic pressure (CsCOP)
what is the main driving force (pressure) determining the net filtration pressure?
glomerular hydrostatic pressure (GHP)
what is the glomerular hydrostatic pressure (GHP)?
blood pressure at + 50 mmHg
what is the blood colloid osmotic pressure (BCOP)?
albumin at - 25 mmHg
what is the capsular hydrostatic pressure (CsHP)?
corpuscle embedded in tissue at - 15mmHg
what is the capsular colloid osmotic pressure (CsCOP)?
no protein in the capsular space at 0mmHg
what is the net filtration pressure in terms of mmHg? (specific number)
+ 10mmHg
what is the result of filtration of the kidney?
results in an isotonic primary filtrate because it is based on NaCI
what is the equation that describes the rate at which substance S is cleared by the kidneys per unit time?
Cs = Us x V / Ps (in mL/min) Clearance = concentration of S in urine (mg/L or mol/L) x volume of urine produced per unit time (mL/min or L/hour) / concentration of S in plasma (mg/L or mol/L)
what is the relationship between the equation for clearance and substances that can be detected in plasma and urine?
the equation describes the clearance via the kidneys for ALL substances that can be detected in plasma and urine
what is the letter used to represent clearance of substance?
S
what is glomerular filtration rate (GFR)?
amount of fluid filtered per unit time in all of the nephrons present in the body
what is the normal glomerular filtration rate (GFR)?
180L per day or 125mL per minute
what are the 3 characteristics of the glomerular filtration rate (GFR)?
1) tightly regulated
2) variation from person to person
3) declines slowly from age 30
what are the 3 characteristics of the glomerular filtration rate (GFR)?
1) tightly regulated
2) variation from person to person
3) declines slowly from age 30
what are the 3 requirements for a substance to be used as a measure of GFR?
1) not be reabsorbed from the tubule
2) not be secreted into the tubule
3) not be metabolised
what are the 2 main substances that fit the requirements to be used as a measure of GFR?
1) inulin (NOT INSULIN)
2) creatinine
what is inulin?
a polysaccharide not metabolised by the body
-is not found in the body, must be injected
what is creatinine?
a waste product produced by muscles that is already in the body therefore is most commonly used clinically
what is renal plasma flow (RPF)?
625 ml of plasma per minute
what is the relationship between renal plasma flow (RPF) and glomerulus filtration rate (GFR)?
renal blood flow (RBF) is 625 ml of plasma per minute but only 125 ml of that is filtered per minute from the glomerulus (GFR)
-the rest flows through the efferent arteriole
what is the filtration fraction?
=(GFR / RPF)
= glomerulus filtration rate / renal plasma flow
what is the filtered load?
amount of a particular substance (solute) filtered per minute
what is the equation for filtered load?
filtered load = GFR x solute plasma conc.
