Nephron Anatomy Flashcards
nephron
basic functional unit of the kidney
balances what enters the body with what leaves the body
afferent arterioles
carries unfiltered blood to the glomerulus
glomerulus
site of plasma filtration
OVERprocesses the blood
Bowman’s capsule
cup-like sac surrounding the glomerulus to collect filtrate
layers of Bowman’s capsule
- parietal
- visceral
parietal layer
outer cell layer
simple squamous epithelium with tight junctions
visceral layer
inner cell layer
leaky epithelial cells (podocytes)
renal tubules
site of reabsorption and secretion
proximal convoluted
distal convoluted
collecting tubules
mesangial cells
supportive cells that surround the capillaries
maintain shape and filtration flow
efferent artioles
carries blood out of glomerulus to peritubular capillaries/vasa recta for further exchange (reabsorption/secretion) with renal tubules
peritubular capillaries
site of gas exchange in the CORTEX
- surrounds PCT and DCT
- HIGH blood flow for reabsorption
vasa recta
site of gas exchange in the MEDULLA
- surrounds loop of Henle and collecting tubules
- SLOW blood flow to maintain ion gradients and retain water
cortical nephrons
located near peripheral edge of cortex
- has SHORT loops of Henle
- LESS concentrated urine due to less water reabsorption
MAJORITY OF NEPHRONS
juxtamedullary nephrons
located near corticomedullary border
- has LONG loops of Henle
- MORE concentrated urine due to GREATER water reabsorption
More common in desert/low water availability habitats
steps of urine formation in the nephron
- glomerular filtration
- tubular reabsorption
- tubular secretion
glomerular filtration
- plasma from afferent arterioles enters capillary bed at the glomerulus
- water and small solutes/ions exit bloodstream through fenestrated capillary walls and enter Bowman’s space
tubular reabsorption
filtrate travels through proximal convoluted tubule as water, glucose, amino acids, and some ions get reabsorbed into the peritubular capillaries
tubular secretion
filtrate travels through the PCT, loop of Henle, DCT, and collecting ducts as some ions/solutes exit peritubular capillaries and enter into the filtrate for excretion
glomerulus
site of filtration
- fenestrated capillaries: allow small ions/solutes and water to filter out of plasma to form filtrate
filtration barriers
- endothelium - fenestrated capillaries
- basement membrane - negatively charged
- podocytes - regulate flow through filtration slits
proximal convoluted tubule
site of reabsorption
- simple cuboidal epithelium w/ BRUSH BORDER
- mitotically active
- reabsorbs majority of filtrate (all glucose and AA get reabsorbed)
loop of Henle
regulates water and electrolyte balance
descending: water reabsorption
- simple cuboidal ep.
ascending: sodium reabsorption
- simple squamous ep.
- thin limb: inner medulla
- thick limb: outer medulla; simple cuboidal
distal convoluted tubule
fine-tunes ion and water reabsorption, pH regulation
- contains JGA, macula densa cells, juxtaglomerular cells, extraglomerular cells
juxtaglomerular apparatus
regulates blood pressure by sensing BP and NaCl levels
located at vascular pole on top of afferent arteriole to sense incoming flow
macula densa cells
sense NaCl levels
signals for renin secretion in response to low NaCl or high BP
juxtaglomerular cells
sense BP and secrete renin into afferent arterioles
innervated by sympathetic fibers
collecting tubules/ducts
regulates ion and water excretion
- receive filtrate from MULTIPLE nephrons
- fine-tunes urine concentration
simple cuboidal or columnar epithelium
tubules: smaller, cortical
ducts: larger, cortical and medullary
papillary ducts (ducts of bellini)
transport urine into the renal pelvis
collecting ducts join to form papillary ducts –> calyces/crest –> renal pelvis`
does renal function depend on innervation
NO - only juxtaglomerular cells that rely on sympathetic innervation for BP control
what component of ANS innervates kidney
sympathetic
