Chapter 26 Flashcards
what are the functions of the kidneys
regulation of body fluid osmolality and volumes
regulation of electrolytes balance
regulation of acid base balance
excretion of metabolic products and foreign substances
production and secretion of hormones
what metabolic wastes are excreted
urea (metabolism of amino acids) creatinine (from muscle creatinine) uric acid (from nucleic acid) bilirubin (or other end products of hemoglobin break down) Metabolites of hormones
what hormones are secreted by the kidneys
erythropoietin
vitamin D3
Renin
what is the functional unit of the kidney
nephron
describe kidney vasculature
renal artery arcuate arteries interlobular arteries afferent arterioles glomerular capillaries efferent arteriole peritubular capillaries venous system
from the efferent arteriole, blood can travel where?
to peritubular capillaries or descending vasa recta; then to venous system
afferent areteriole does what
carries blod to the glomerulus
glomerulus is what
tuft of capillaries that filter the plasma entering into Bowman’s capsule (is part of filtration barrier)
efferent arteriole is what
carries blood from the lomerulus to peritubular capillaries
peritubular capillaries are what
capillary network surrounding the tubular components, supply renal tissue and exchange fluids/substances with tubular components (reabsorption and secretion)
vasa recta
specialized peritubular capillaries present in juxtamedullary nephrons
be able to identify on chart
x
bowmans capsule does what
collects the filtrate from the glomerulus (part of filtration barrier)
proximal tubule
mainly uncontrolled reabsorption occurs here; secretion also
loop of henle
establishes osmotic gradient in renal medulla; crucial role in ability of kidney to form concentrated or dilute urine
what are the 3 parts of loop of henle
descending limb
thin ascending limb
thick ascending limb
distal tubule and collecting duct function in
controlled reabsorption of Na and water (ADH dependent); K secretion
cortical nephron
renal copuscle located in outer region of cortex
short loop of henle
efferent arteriole forms peritubular capillaries
juxtamedullary nephron
renal corpuscle located in region of cortex next to medulle
long loop of henle which extends deeper into medulla
efferent arteriole forms peritubular capillaries and vasa recta
what are the components of a renal corpuscle
bowmans capsule
glomerular capillaries
what is the function of the renal corpuscle
ultrafiltarion
what are the components of a juxtaglomerular apparatus
macula densa cells and juxtaglomerular cells
what is the function of juxtaglomerular apparatus
feedback mechanism
what are the major processes in the nephron
- filtration
- reabsorption
- secretion
- excretion
which process of the nephron is discriminating
secretion
which part is nondiscriminating
filtration
what substance undergoes filtration only (and therefore is 100% excreted)?
creatinine
what substance is filtered and partially reabsorbed
Na and Chloride
What substance is completely filtered and completely reabsorbed
amino acids and glucose
what substances are secreted
organic acids and bases (PAH)
GFR is equal to what?
the sum of the filtration rates of all functioning nephrons
monitoring GFR provides what information
the severity or progression of renal dysfunction
what is the filtration barrier (the renal corpuscle) composed of?
- fenestrations in glomerular capillary
- basement membrane
- filtration slits created by the foot processes on the podocytes
fenestrations in glomerular capillary
freely permeable to water and small solutes but not cells or large proteins
express negatively charged glycoproteins to repel filtration of proteins
size and charge barrier
basement membrane
acellular, porous matrix of negatively charged extracellular proteins that repel the filtration of proteins
charge barrier
filtration slits created by the foot processes on the podocytes make up the ____
inner layer of bowman’s capsule
filtration slits created by the foot processes on the podocytes
podocytes are specialized epithelial cells
also have negatively charged glycoprotein to repel proteins
filtrate is essentially free of what
proteins and cellular elements (RBC)
Why are large amounts of solutes filtered, then reabsorbed?
GFR allows kidneys to rapidly remove wastes;
allows all body fluids to be filtered multiple times a day
blood flow to the kidneys is ____ of cardiac output
about 25%
what is the filtration fraction?
the proportion of the plasma that enters the glomerulus and is subsequently filtered is ~20%; the remainder continues on through the glomerular capillaries to the efferent arteriole and peritubular capillaries
filtration fraction is equal to
GFR/RBF
What forces favor filtration
glomerular hydrostatic pressure
colloid oncotic pressure of bowmans capsule would if it existed
what forces oppose filtration
glomerular colloid osmotic pressure
bowmans capsule hydrostatic pressure
What is the Kf
the product of hydraulic conductivity and surface area of glomerular capillaries
increase in Kf causes
increase in GFR
increase in bowmans capsule hydrostatic P causes
decrease in GFR (urinary tract obstruction)
increase in glomerular capillary coloid osmotic pressure causes
decrease in GFR (decrease in RBF, increase in plasma proteins)
increase in glomerular capillary hydrostatic P causes
increase in GFR (decrease in arterial P, decrease in sympathetic activity, decrease angiotensin II)
decrease Kf causes
decrease GFR (renal dz, diabetes mellitis, hypertension)
what happens to colloid osmotic pressure in glomerular capillaries when there is an increase in the filtration fraction (GFR or RBF)
there is an increase in the rate at which plasma colloid osmotic pressure rises along the glomerular capillary (decrease in filtration fraction has opposite effect)
glomerular hydrostatic pressure is determined by
arterial pressure
afferent arteriolar resistance
efferent arteriolar resistance
an increase in resistance of afferent arteriole does what
reduces glomerular hydrostatic pressure and decreases GFR
dilation of afferent arteriole does what
increases GFR
Constriction of efferent arterioles does what
increases glomerular hydrostatic pressure and as long as the increase in efferent resistance does not reduce renal blood flow too much, GFR increases
what would happen if efferent arteriole resistance increased too much
a rise in colloid osmotic pressure exceeds increase in glomerular capillary hydrostatic pressure and GFR decreased
renal blood flow indirectly determines ____
GFR
Kidneys regulate blood flow by adjusting what
vascular resistance
what are the major resistance vessels in the kidney
afferent and efferent arteriole and interlobular artery
what are the hormones that control renal blood flow
norepinephrine epinephrine endothelin angiotensin II endothelial-derived nitric oxide prostaglandins
norepinephrine and epinephrine have what effect on gfr
decreases gfr
endothelin does what to gfr
decreases gfr
angiotensin II does what to GFR
prevents decrease of gfr
endothelial derived nitric oxide does what to GFR
increases gfr
what does prostaglandin do to GFR
increases GFR
How does angiotensin II prevent decrease in GFR
it increases glomerular hydrostatic pressure while reducing renal blood flow; by constricting efferent arterioles, angiotensin II helps prevent decreases in GFR
what arterioles are more susceptible to vasoconstriction
efferent arterioles are more susceptibel than afferent arterioles
what is the function of prostaglandins
to dampen vasoconstrictor effects of sympathetic nerves and angiotensin II;
what is the net effect of prostaglandins
to increase RBF without a change in GFR; prevents severe and potenitally harmful vasoconstriction and renal ischemia
prostaglandin synthesis can be stimulated by
dehydration
stress
sympathetic nerve outflow
angiotensin II
why do you need to be careful when administering NSAIDs
NSAIDs block prostaglandin formation and thus block the protective effects they have
what are the 2 mechanisms of autoregulation
myogenic mechanism
tubuloglomerular feed back mechanism
what is the myogenic mechanism
ability of blood vessels to resist stretching during increased arterial pressure (by raising vascular resistance because vessels arent stretching, prevents excessive increases in renal blood flow and GFR)
tubuloclomerular feed back mechanism
macula densa cells sense changes in volume delivery
what are the steps in tubuloglomerular feedback
decreae in arterial pressure causes decrease in glomerular hydrostatic pressure, causes decrease in GFR, causes decrese in macula densa Na Cl, causes increase in renin, causes increase in angiotensin II, causes increase in efferent arteriolar resistance, decrease afferent areteriolar resistence
despite autoregulation, RBF and GFR can be changed by
hormones and sympathetic nerve activity
RBF is a determinant of ___ so both are regulated by same mechanisms
GFR
What is filtered load
total amount filtered into bowmans capsule (mass/time)
filtered load is equal to
GFR x Plasma concentration
