7: Physiology 2 Flashcards
What are the homeostatic functions of the kidneys?
Water balance
Salt balance
Acid-base balance
Maintenance of plasma volume and osmolarity
What do the kidneys excrete?
Toxic metabolites
Drugs and their metabolites
What hormones do the kidneys secrete?
Renin
Erythropoietin
What are the functions of
a) renin
b) erythropoeitin?
a) Maintenance of BP by RAAS
b) Protects RBC from damage and increases RBC production - used in doping
What vitamin do the kidneys activate?
What is its active form called?
Vitamin D
Calcitriol
What is the name and function of activated Vitamin D?
Calcitriol
Enables calcium absorption in GI tract
At what levels are the
a) left kidney
b) right kidney
found?
a) T12 - L2 (not pushed inferiorly)
b) L1 - L3 (pushed inferiorly by liver)
What process propels urine from the kidneys to the bladders through the ureters?
Peristalsis
What appearances do the renal cortex and medulla have?
Cortex - granulated
Medulla - striated
The renal medulla is arranged into ___ of nephrons.
pyramids
How long is an adult kidney?
12 cm
How much of the cardiac output do the kidneys account for?
25%
loads, understandable given they filter the blood
What are the functional units of the kidneys?
Nephrons
arranged into pyramids in renal medulla
Which four processes occur in nephrons?
FILTRATION of urine from blood
REABSORPTION of water, ions, glucose, AAs from tubules into capillaries
SECRETION of “” from capillaries to tubules
EXCRETION into ureters
What blood vessels supply the nephrons?
Renal artery - splits into afferent and efferent arterioles
Stuff then reabsorbed into peritubular capillaries draining into Renal vein
What structure is the glomerulus found inside?
Bowman’s capsule
Where does filtration of blood occur?
Glomerulus
Blood is filtered into Bowman’s capsule
Where does urine travel from the glomerulus to reach the collecting duct?
Proximal tubules
Loop of Henle
Distal tubules
What part of the distal tubule passes by the glomerulus and alters renal function?
Juxtaglomerular apparatus
Which structures does the juxtaglomerular apparatus pass between?
Afferent and efferent arterioles
Nephrons are split between the renal ___ and ___.
renal cortex and medulla
What are the two types of nephron found in the kidney?
Cortical
Juxtamedullary
Which type of nephron is more common?
Cortical (80%)
What is the difference between cortical and juxtamedullary nephrons?
Juxtamedullary nephrons have:
- Longer Loops of Henle
- One single peritubular capillary called the vasa recta which follows the Loop of Henle
What type of capillaries do
a) cortical
b) juxtamedullary nephrons have?
a) Loads of peritubular capillaries
b) One vasa recta
Juxtamedullary nephrons produce more ___ urine.
concentrated / hypertonic
Which arteriole has the wider diameter?
Afferent arteriole
What are podocytes?
Epithelial cells of Bowman’s capsule, have big processes called filtration slits
What is found between the endothelium of glomerular capillaries and the podocytes of Bowman’s capulse?
Basement membrane (no cells)
Which layers make up the glomerular membrane?
Endothelium of glomerular capillary
Basement membrane
Podocytes of Bowman’s capsule
The glomerular membrane acts as a big ___.
sieve
for filtrate
Glomerular capillaries are more ___ than other capillaries.
permeable
allows them to filter stuff
Which cells of the JGA secrete renin?
GRANULAR or JUXTAGLOMERULAR CELLS
Which cells of the JGA are sensitive to salt concentrations of the (blood / tubular fluid)?
Macula densa
salt concentration of tubules
What is urine?
Modified filtrate of the blood
How much of the blood which enters a glomerulus is actually filtered?
20%
Rest of it is filtered in the peritubular capillaries
What processes occur to filtrate as it passes through the renal tubules?
Reabsorption back into capillaries
Secretion from capillaries into tubules
What is the rate of filtration?
Mass of substance filtered into Bowman’s capsule per unit time
Filtration rate = [substance]plasma x glomerular filtration rate (GFR)
GFR is usually 120 in healthy people
What is the rate of excretion?
Mass of substance excreted per unit time
Rate of excretion = [substance]urine x urine excretion rate
If a substance’s rate of filtration > rate of excretion, what has occurred?
Reabsorption
If a substance’s rate of filtration < rate of excretion, what has occurred?
Secretion into tubules from capillaries
How do you calculate the rate of secretion?
Rate of secretion = rate of excretion - rate of filtration
