what are kidneys controlled by?
both neural and endocrine inputs
primary function of kidneys
maintain…
- ECF volume
- electrolyte composition
- osmolarity
what do kidneys do in presence of excess water or particular electrolyte (solute)
increase elimination
all functions of kidneys
- maintain water balance of body
- maintain body fluid osmolarity
- maintain proper plasma volume
- help maintain acid-base balance
- regulate ECF solutes (Na, K, Cl, Ca, phosphate, etc)
- excrete wastes of metabolism
- excrete forgein compounds ingested
- produce erythropoietin
- produce renin
- activate vit. D
kidney structure
- bean shaped
- ~10cm long
- outside of kidney is renal cortex
- inner part of kidney is renal medulla
- inner core of kidney has renal pelvis (where urine empties and is channeled to ureter)
what is associated with each kidney
an adrenal gland (on top of kidney)
what’s the functional unit of the kidney?
the nephron
- >1 million in a healthy adult kidney
what happens within nephron?
blood is filtered to produce urine and reabsorption of necessary fluids and molecules
2 components of nephron
- vascular component (supply blood)
- tubular component (carries filtrate through nephron)
vascular component of nephron
- major part is the glomerulus
- blood will enter renal artery, which subdivides into small afferent arterioles (each supply a nephron)
- efferent arterioles leave the nephron (transport unfiltered blood out of glomerulus)
glomerulus
ball like capillary where water and solutes are filtered from plasma
how are capillaries of nephron different?
arteriole blood will enter and leave with no O2 extracted
- instead efferent arteries subdivide into peritubular capillaries
peritubular capillaries
deliver O2 to renal tissue
tubular component of nephron
- filtered blood enters hollow tube formed of a single layer of epithelial cells
- transport urine to renal pelvis
- a long tube thats divided by differences in structure and function
- begins in bowmans capsule
- then fluid is passed to proximal tubule within renal cortex (which is highly coiled)
- next is loop of henle
- tube then coils again and is called distal tubule (also within cortex)
- collecting duct
- then drains into renal pelvis
bowmans capsule
encircles glomerulus to collect fluid filtered from the glomerular capillaries
loop of henle
- forms hairpin loop that dips into renal medulla
- descending limb travels from cortex to medulla
- ascending limb travels from medulla back to cortex
what does ascending limb of loop of henle run into
fork of afferent and efferent arteries in a region called juxtaglomerular apparatus
distal tubule
empties into collecting duct which travels deep into medulla
2 types of nephrons
cortical and juxtamedullary
cortical nephrons
- the glomeruli lie in outer layer of cortex
- 80% of all nephrons have cortical nephrons
- primarily serve secretory and regulatory functions
- the loop of henle only slightly dips into renal medulla
- the peritubular capillaries wrap around short loops of henle
juxtamedullary nephrons
- found on inner layer of cortex
- responsible for conc. and dilution of urine
- the peritubular capillaries from these nephrons from hairpin loops of vasculature (AKA vasa recta) that are in close proximity to long loops of henle
flow of blood flow through nephron
renal artery-> glomerulus -> afferent arteriole -> peritubular capillaries -> efferent arteriole -> renal vein
flow of solutes through nephron
proximal tubule-> bowmans capsule-> loop of henle-> distal tubule -> collecting duct -> renal pelvis
basic renal processes
- glomerular filtration (GF)
- tubular reabsorption (TR)
- tubular secretions (TS)
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