Concise and easy to access notes on the physiology of the renal system for first year dental students.
Covers kidney structure, renal corpuscle & tubule structure, glomerular filtration & clearance, tubular reabsorption & secretion, regulation of blood volume, the renin-angiotensin-aldosterone sy...
Kidney
Urinary System
• Urinary System = 2 kidneys + 2 ureters
+ 1 bladder + 1 urethra
• Kidneys located on each side of vertebral
column, between T12 & L3
~1.5 L urine output / day
Kidneys
• Renal Hilum: entry point in middle of
kidney for renal artery / vein / lymphatics
/ nerve
• Kidneys are surrounded by a fibrous
renal corpuscle + thick layer of fat
Kidney Structure
• Renal Cortex: dark, outer layer, containing glomerulus &
proximal / distal tubules
• Renal Medulla: lighter, inner layer with triangular lobes
Renal Pyramids (pyramids), containing loop of Henle & collecting ducts
• Renal pyramids point • Each kidney contains ~800,000 nephrons
towards centre of kidney
• Collecting ducts converge at
apex of pyramid → calyx →
renal pelvis
• The renal cortex is the fused
cortical parts of the lobes,
extending down between
adjacent medullary lobes
• Renal Papillae: 10-18
medullary lobes (pyramids),
surrounded by calyx (an
extension of the renal
pelvis)
Nephron
• Begins with Bowman’s capsule,
Collecting
which surrounds glomerular Glomerulus Duct
capillaries (collects filtrate)
• Followed by proximal tubule, loop Renal
of Henle, distal tubule & early Corpuscle
Bowman’s
collecting duct Distal
Capsule
• Cortical Nephron (~85%): Tubule
Nephron
glomeruli in outer 70% of cortex
& short LOH
• Juxtamedullary Nephron
Renal Proximal Loop of
(~15%): glomeruli close to cortex-
Tubule Tubule Henle
medulla boundary + long LOH
, Renal Corpuscle
Glomerular Basement
Membrane
• Surrounds glomerulus
Glomerulus capillary endothelium
• Loop of twisted capillaries surrounded by • Mostly type IV collagen,
Bowman’s capsule proteoglycans & laminin
• Endothelial cells – may fenestrae, which
restrict movement of RBCs
• Mesangial cells – contractile (to regulate
blood flow) & phagocytic (to remove
molecules trapped in glomerular basement
membrane)
Bowman’s Capsule
• Surrounds glomerulus
• Outer (parietal) layer = simple squamous
epithelium
• Inner (visceral) layer = podocytes
(endothelial cells)
o Pedicels: processes projecting from
podocytes
o Filtration Silts: gaps between
pedicels, bridged by a thin
diaphragm, containing pores
Ultrafiltration
• Blood enters renal corpuscle via afferent Filtration Barrier
arterioles 3 components:
• Blood is filtered at glomerulus into • Endothelial cells of glomerular capillaries
Bowman’s capsule • Glomerular basement membrane
• Blood exits renal corpuscle via efferent • Endothelial cells of Bowman’s capsule
arterioles (podocytes)
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