Lecture 11 Flashcards
6 functions of the kidneys
1) excretion of waste : creatinine, urea, uric acid, toxins -> in urine
2) ECF regulation and blood pressure ; if ECF low = blood pressure low
3) regulation of osmolarity (290 mOsM) : adjust urine volume, filtration / reabsorption of salts
4) maintenance of ion balance : Na+, K+, Ca2+
5) regulation of pH : H+ and HCO3- (not as fast as lungs)
6) production of hormones : erythroprotein, renin
4 components of urinary system
kindey, ureters, urine bladder, urethra
what is critical to renal function ?
high rate of blood flow through kidneys (20% of CO)
2 layers of the kidney, where the urine is stored, functional unit of kidney ? 2 types
outer cortex and inner medulla.
Urine stored in renal pelvis.
Unit is the nephron : cortical nephron and juxtamedullary nephron
name the different regions of a nephron (5) and their main function
1) glomerulus : connection with arterioles, filtration of blood
2) proximal tube : reabsorption (mostly water and glucose) and secretion of molecules from blood
3) loop of henle : reabsorption, mainly osmolarity compounds
4) distal tube : reabsorption and secretion
5) collecting duct : branches from different nephrons join
distribution of the two types of nephrons. To what capacity can a kidney go ?
80% cortical : glomerulus, proximal and distal tubes
20% juxtamedullary : loops of henle and collecting ducts
kidney can go up to 130% of its capacity
main function of the 2 nephron types, one difference between the two (blood related)
cortical : filtration of about 20% of plasma, waste clearance
juxtamedullary : urine concentration.
Diff : cortical have a peritubular capillary network around their tubes (for secretion). Juxta only have that around the part located in the cortex.
what does the urinary excretion depend on (formula) ? how many liters per day do we filter in the glomerulus ?
amount secreted = filtered + secreted - reabsorbed
-> about 0.5 to 2 liters a day
glomerulus : around 180L filtered per day
renal corpuscule : three layers of the filtration barrier, what are mesangial cells ?
barrier : capillary endothelium - basal lamina (negatively charged) - bowman’s capsule epithelium (podoctyes).
-> Slits between the feet of podocytes. Small enough that blood cells can’t cross.
Mesangial cells between capillaries can contract to alter blood flow. They are also immunocompetent
two types of capillaries ? where would you find them ?
Continuous : leaky junctions but not very permeable. -> in brain
Fenestrated : large pores -> in kidney
three pressures that are involved in the filtration process
driving force : hydrostatic blood pressure
resistance : colloid osmotic pressure (plasma proteins attract water) and fluid pressure from fluid in bowman’s capsule
net pressure is about 10 mmHg
what is the glomerular filtration rate ? influenced by what ? how can it be regulated ?
Volume of fluid that filters into bowman’s capsule per unit of time : average GFR = 125 mL/min or 180L/day.
Influenced by blood flow, surface area and permeability.
- increase resistance in efferent arteriole -> GFR increases
- increase resistance in afferent arteriole -> decreased GFR
definition of renal clearance, what is one assumption ?, formula for clearance
volume of blood plasma which is cleared from a specific compound in mL/min
assumption that substance X is completely transferred in urine (nothing in venous output)
c = UxV/P
difference between inulin and glucose clearance ?
inulin clearance = GFR because nothing is reabsorbed or secreted.
In healthy patients, glucose is 100% reabsorbed -> clearance is zero
clearance of inulin, creatinine, glucose
inulin and creatinine : 120 ~ GFR
glucose = 0
what are the two sphincters made of ?
internal -> smooth muscle
external -> skeletal muscle
what is micturition ?
spinal reflex (conscious and unconscious control from higher brain cenetrs) :
- bladder fills and walls expand -> stretch receptors send signals
- full bladder -> parasympathetic neurons -> smooth muscle contracts. At the same time, somatic motor neurons to external sphincter are inhibited.
how do the kidneys react when blood pressure increases or decreases ?
increases -> excrete salts and water in urine
decreases -> conserve water to minimize volume loss
what is the response to salt ingestion ?
osmolarity increases (not volume) -> increased renal water reabsorption -> later on the kidneys excrete salt and water
In other words, salt is first diluted with more water and then both are excreted
how is ANG II produced ? when is the pathway activated ?
liver produces angiotensinogen. Renin transforms it to ANG I in plasma. ACE enzyme transforms it to ANG II.
Activated when decrease of blood pressure
