Renal Lec 3 Flashcards
three basic renal processes in order
- glomerular filtration
- tubular secretion
- tubular reabsorption
amount excreted (equation)
amount filtered + amount secreted - amount reabsorbed
processes that favour entry into lumen of tubule
- filtration
- secretion
processes that favour exit from lumen of tubule
- reabsorption
- excretion of urine
glomerular filtration
filtration from blood vessels in bowman’s space
tubular secretion
secretion from blood vessels into tubule
tubular reabsorption
reabsorption into blood vessels from tubule
filtration layers in glomerular capillary
- fenestrated endothelial layer
- basement membrane
- podocytes with filtration slits
large proteins (like albumin) are held back because (3 reasons)
- pore sizes are small
- pores + BM are - charged, repels - charged proteins
- podocytes have semi porous membranes
semi porous membranes of podocytes have (types of transmembrane proteins)
- nephrins
- podocins
what passes through glomerulus? (9 things)
- water
- electrolytes
- glucose
- a.a
- fatty acids
- vitamins
- urea
- uric acid
- creatinine
what remains in glomerulus? (6)
- blood cells
- plasma proteins
- large anions
- protein bound minerals
- protein bound hormones
- most molecules greater than 8 nm in diameter
ultrafiltrate
most of the substance in plasma in filtrate
proteinuria
increased protein in urine
net glomerular filtration pressure amount
+16
forces favouring filtration
glomerular capillary blood pressure
forces opposing filtration
fluid pressure in bowman’s space
osmotic force due to protein in plasma
osmotic forces due to protein is bowman’s space is low because
concentration of protein in bowman’s space in so low
net glomerular filtration pressure equation
glomerular capillary blood pressure - fluid pressure in bowman’s space - osmotic force due to protein in plasma
GF pressure initiates urine formation by
forcing filtrate from plasma into bowman’s space
volume that gets filtered out
20%
volume excreted out of body
<1%
volume that is reabsorbed
19%
volume that continues onto the efferent arteriole
80%
glomerular filtration rate (GFR) - (def.)
volume of fluid filtered from the glomerulus into the bowman’s space per unit time
GFR amount (mL/min, L/day), in 70 kg man
- 125 mL/min
- 180 L/day
high GFR allows plasma to be
filtered around 60 times a day
4 factors affecting GFR
- net glomerular filtration pressure
- permeability of corpuscular membrane
- surface area available for filtration
- neural and endocrine control
factors affecting GFR that are (somewhat) fixed
- permeability of corpuscular membrane
- surface area available for filtration
mesangial cell (def.)
-specialized cells in glomerulus that are not part of the filtration layers or juxtaglomerular apparatus
contraction of mesangial cell (do what?)
reduce surface area of glomerular capillaries, decreasing GFR
juxtaglomerular apparatus (JGA) two types of cells
- macula densa
- juxtaglomerular cells
macula densa (def.)
cells on the wall of the distal tubule
macula densa can sense
increased fluid flow through distal tubule through Na+/ Cl- concentration
macula densa secretes
vasoactive compounds (ex. adenosine)
macula densa paracrine effect changes
afferent arteriolar resistance by signalling to JG cells
juxtaglomerular cells (other name)
granular cells
juxtaglomerular cells are on (location)
the wall of the afferent arteriole
juxtaglomerular cells control
renin release based on sodium concentration
GFR- large changes in arterial pressure or renal blood flow
GFR remains fairly constant
autoregulation of GFR occurs by
changing renal blood vessel resistance to compensate for changes in blood pressure
myogenic (def.)
how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow constant within the blood vessel
changes in renal blood vessel resistance mechanism
tubuloglomerular feedback effect –> myogenic response of afferent arteriole
tubuloglomerular feedback effect- role of JGA
- increased tubular flow causes constriction of afferent arteriole to reduce GFR
- regulated` by paracrine actine on JGA
- paracrine control of afferent arteriole resistance
blood pressure range for autoregulation of glomerular filtration
wide (80-180 mmHg)
increased resistance in afferent arteriole
decreased GFR
increased resistance in efferent arteriole
increased GFR
decreased resistance in efferent arteriole
decreased GFR
decreased resistance in afferent arteriole
increased GFR
adenosine causes
vasoconstriction of afferent arteriole
filtered load
total amount of non-protein or non-protein bound substance filtered into bowman’s space
filtered load (equation)
filtered load = GFR x [substance in plasma]
substance excreted in urine < filtered load
reabsorption has occurred
substance excreted in urine > filtered load
secretion has occurred
