kidney 1 Flashcards
what does the kidney excrete
metabolic products - urea, uric acid, creatinine, bilirubin
foreign substances - pesticides, chemicals etc.
excess substance - water etc.
order of parts of the nephron
glomerulus, proximal convoluted tubule thin descending limb of loop of henle thick ascending limb of loop of henle distal convoluted tubule collecting duct
nephrons
renal corpuscle (glomerulus and bowman’s capsule) and both convoluted tubules in cortex, loop of henle extend to medulla
nephritis empty into
the collecting duct
2 types of nephrons
- cortical
- juxtamedullary
cortical nephrons
80% of nephrons
- renal corpuscle in outer portion of cortex and short loops of henle extend only into outer region of medulla
juxtamedullary nephrons
other 20%
- renal corpuscle deep in cortex and long loops of henle extending deep into the medulla
- peritubular capillaries and vasa recta
- ascending limb has defined thick and thin regions
- enable kidney to secrete very dilute or very concentrated urine
what does the glomerulus do
filters blood plasma
what does the glomerulus look like
ball like tuft of glomerular capillaries
afferent arteriole
supplies the glomerulus capillaries
efferent arteriole
drains the glomerulus
subdivides the peritubular capillaries
which later rejoin to form venues and the renal vein
glomerulus grains to the
efferent arteriole of the renal artery
2 main parts of the renal artery
afferent and efferent arteriole
driver of glomerular filtration
pressure within the glomerulus
what determines the pressure within the glomerulus
the diameter of the efferent vs. the afferent arteriole
glomerular filtration
water and most solutes in plasma filter out of glomerular capillaries into bowman’s capsule > renal tubule
tubular reabsorption
as filtered fluid moves along the tubule and through collecting duct, about 99% of water and many useful solutes is reabsorbed to the peritubular space and returned to blood
tubular secretion
material is secreted into tubular fluid (such as wastes, drugs, excess ions) - removes substances from blood
solute excretion =
glomerular filtration + secretion - reabsorption
efferent arteriole drains to
peritubular capillaries (vasa recta), peritubular venule, renal vein
net filtration pressure is a balance of 2 pressures
- pressures that promote filtration
- pressure that promote reabsorption
pressures that promote filtration
- capillary hydrostatic pressure
- interstitial fluid osmotic pressure
pressures that promote reabsorption
- plasma colloid osmotic pressure
- interstitial fluid hydrostatic pressure
net filtration pressure is equal to
pressures that promote filtration - pressures that promote reabsorption
glomerular filtration
fluids move across the glomerular capillary in response to net glomerular hydrostatic pressure
whaat can’t be filtered
cells, platelets
protein complexes
large/medium sized proteins
large things
glomerular filtration rate depends on
- permeability of the membrane
- surface area of the membrane
- filtration pressure
3 barriers to cross in filtration
- glomerular capillary wall - pores between endothelial cell
- basement membrane - collagen and glycoproteins
- podocytes - filtration slits between cellular foot processess
charge of the basement membrane
negative charges of the basement membrane repel anions so they get retained in blood while positively charged things go through
homeostasis in the kidney
requires kidneys to maintain a relatively constant GFR
too high - too quick for reabsorption
too low - excessive reabsorption, some waste products not adequately excreted - renal hypoxia
NFP =
net filtration pressure =
GBHP - CHP - BCOP
GBHP
glomerular blood hydrostatic pressure
the blood pressure of the glomerular capillaries forcing water and solutes through filtration slits
CHP
capsular hydrostatic pressure
the hydrostatic pressure exerted against the filtration membrane by fluid already in the capsular space and represents back pressure
BCOP
blood colloid osmotic pressure
due to the presence of proteins in blood plasma and also opposes filtration
controlling filtration pressure
renal arteriolar resistance
efferent arteriole constriction
- reduced renal blood flow
- increases GFR
afferent arteriole constriction
- reduces renal blood flow
- reduced GFR
three mechanisms of regulating GFR
- renal auto regulation
- neural regulation
- hormonal regulation
renal autoregulation
kidneys themselves maintain constant renal blood flow and GFR using
- myogenic mechanism
- tubuloglomerular mechanisms
myogenic mechanism
occurs when stretching triggers contraction of smooth muscle cells in afferent arterioles which reduced GFR
tubuloglomerular mechanism
macula dense provides feedback to glomerulus, inhibits release of NO causing afferent arterioles to sonctrict and decreasing GFR
what is the point of auto regulation of GFR and RBF
the kidneys are able to maintain a constant renal blood flow and GFR over a large range of arterial pressures
myogenic auto regulation occurs in response to
slight changes in blood pressure - control at the local level
- increase in mean arterial blood pressure automatically induces vasoconstriction of afferent arteriole, causing decreased flow, decreased GFR and bringing is back to normal
- decrease in mean arterial blood pressure induces afferent arteriole vasodilation, increase in flow and GFR, and bringing GFR back to normal levels
juxtaglomerular apparatus
a collection of densely packed epithelial cells at the TAL/DCT junction
juxtaposed two its own glomerulus, between afferent and efferent arterioles
- position enables it to rapidly alter glomerular resistance in response to changes in the flow rate through the distal nephron
sympathetic nerves affecting GFR
release NA
shuts down GI blood flow
vasoconstriction of afferent arteriole decreases GFR and renal blood flow
circulating hormones affecting GFR
atrial natriuretic peptide - increases afferent and decreases efferent which increases pressure and therefore increases GFR
angiotensin
- blood pressure control
- operates via positive feedback, increases MAP by vasoconstricting
intraglomerular mesanggial cells
smooth muscle
regulated intraglomerular capillary blood Flow
MC contraction is couples with contraction of the glomerular capillary endothelium basement membrane
decrease in surface area causing decrease in GFR
