Physiology 2 Flashcards
the 10 functions of the kidneys
- water balance
- salt balance
- Maintenance of plasma volume
- Maintenance of plasma osmolarity
- Acid-base balance
- Excretion of metabolic waste products
- Excretion of exogenous foreign compounds
- secretion of renting to maintain arterial blood pressure
- secretion fo erythropoietin which is required to produce red blood cells
- Conversion fo 25- hydroxyvitamin D3 (cholecalciferol) to 1,25-hydroxyvitamin D3 (CALCITRIOL)
primary function of the kidney
is to regulate the volume, composition and osmolarity of body fluids
concept of homeostasis for any substance
input has to equal output which can be applied to Na+, K+, Ca2+, Cl- and PO42- so the kidney controls the excretion of these substances in order to maintain homeostasis
blood enters the kidney
via the renal artery
blood drains from the kidney
via the renal vein
what is the functional unit of the kidney
the nephron
the first part of the nephron is
the glomerulus
the glomerulus receives
branches of the renal artery called the afferent arteriole and exiting the glomerulus is the efferent arteriole
the glomerulus function is
filtration of the blood, blood flows through the glomerulus and small molecules bass into bowmans space where it is known as the filtrate
how does the filtrate get from the afferent arteriole into bowmans space
- the afferent arteriole is lined with endothelial cells which contains fenestrations which allows small molecules to pass through but prevents larger proteins passing through
- underneath the endothelial cells is the basement membrane which is negatively charge and repels larger proteins such as albumin inhibiting them from passing through
- on the inner layer of bowmans capsule there is a type of epithelial cell called podocytes which extend there foot processes onto the endothelial cells which ensures they tightly adhere to one another
increasing the diameter of the afferent arteriole
more blood can pass through the glomerulus and the glomerular filtration rate increases
reducing the diameter of the afferent arteriole
less blood can pass through the glomerulus and the glomerular filtration rate falls
after blood has been filtrated in the glomerulus
it flows through the proximal convoluted tubule
the proximal convoluted tubule is very important for
the re-abdsorption of ions like sodium, chloride, amino acids and glucose and it also re-abdorbs water
after the proximal convoluted tubule the filtrate passes into
the descending loop of henle and then into the ascending loop of henle
descending limb of the loop of henle is
impermeable to ions and ONLY re-absorbs water
ascending limb of the loop of henle is
impermeable to water and ONLY re-absorbs ions
the process occurring in the loop of henle is known as
counter-currant multipiclation
why is it called counter-currant
because the loop of henley are travelling in opposite directions
why is it called multipiclation
because the process of re-absorption of ions in the ascending loop of henle is active and by making the renal medially more acidic, it allows the passive movement of water from the descending limb into the intersitium which is a completely passive process
fluid then flows from
the ascending loop of henle into the distal convoluted tubule
the distal convoluted tubule re-absorbs
sodium and chloride
where the distal convoluted tubule passes the glomerulus
this is called the jucto-glomerual apparatus
the junta-glomerular apparatus
is the part of the kidney which controls blood pressure
from the distal convoluted tubule the filtrate then flows into the
collecting ducts
the collecting ducts collects filtrate from
many distal convoluted tubules
what is urea
one of the main waste components in the urine, but the kidney does reliant some in a process called urea recycling in order to increase the osmolarity of the renal medially which increases water re-absorption in the descending loop of henle
the efferent arteriole gives of
many branches called peri-tubular capillaries which cross all over the nephron and pick up everything that has been re-absorbed from the lumen of the nephron into the interstitial to return it back to the renal vein
how much os the plasma entering the glomeruli gets filtered
only 20% the remaining 80% leaves via the efferent arteriole
cells facing the inside of the lumen are on the
apical side
cells on the opposite side of the lumen are on the
base-lateral side
attached to the base-lateral side is the
peri-tubular capillaries
how does re-absorption take place in the proximal convoluted tubules
on the apical surface there are co-transporters so because sodium is actively transported via the sodium potassium ATP ASE pump, eventually there will be less sodium in the cell than in the lyme so sodium will wanto to move down its concentration gradient out of the lumen so this energy gets use to transport glucose out of the lumen down its concentration gradient to be re-absorbed into the blood
how does re-absorption take place in the ascending loop of henle
there is the same sodium potassium pump so as sodium is transported out of the lumen there is a NA+/K+/Cl- co-transporter which is a form of secondary active transport so sodium, potassium and chlorine get re-absorbed
how does re-absorption take place in the distal convoluted tubules
sodium potassium pump causes movement of sodium out of the lumen into the blood, apical membrane contains calcium pores so calcium concentration in the cell is equal to that of the calcium in the lumen, but there is an ante-porter so sodium gets pumped back into the tubule and calcium is pumped into the urine
what actually is urine
modified filtrate of blood
the 3 main functions of a nephron
- filtration
- re-absorption
- secretion
for any substance filtration and tubular secretion is equal to
tubular reabsorption and excretion
rate of excretion is equal to
the rate of filtration+ rate of secretion- rate of re-absorption
movement of substances within the kidney are described in terms of
concentration x flow
rate of filtration of a substance X is
mass of substance X filtered into bowmans capsule per unit time
for a freely filterable substance X the rate of filtration of X is equal to
the concentration of X in the plasma multiplied by the glomerular filtration rate
rate of excretion of substance x is
the mass of substance X excreted per unit time
rate of excretion of substance X is equal to
the consternation of X in the urine multiplied by the urine flow rate
rate of reabsorption of a substance
if the rate of filtration is greater than the rate of excretion then net reabsorption has occurred
rate of re-absorption of substance X
rate of filtration of substance X- rate of excretion of substance X
rate of secretion of a substance
if the rate of filtration of a substance is less than the rate of excretion then net secretion of the substance has occurred
rate of secretion
rate of excretion- rate of filtration
rate of filtration and excretion are
relatively easy to measure
rate of reabsorption and secretion reflect
tubular modification of the filtrate obtained as the different between the rate of filtration and the rate of excretion
