Kidney
Dr. Mahmoud Salah
KIDNEY: Overall architecture 1
Capsule
Cortex
Cortico-medullary
junction
{
Renal vein
}
URETER
Renal artery
Medulla
KIDNEY: Overall architecture 4
Blunt tip of pyramid is the
PAPILLA dripping urine into
Minor calyx to collect
urine
Pyramid
Pelvis
Ureter
Major calyces omitted
LOBULE = the
LOBULE
sector centered on
one medullary ray
- an extension of
Medullary medullary tissue into the
ray cortex, & itself centered
on a collecting duct
Pyramid
Pyramid
LOBE = a pyramid +
the overlying cortex
LOBE
Cortical labyrinth =
Medullary ray Corpuscles &
convoluted tubules
Medullary ray
Centered on
collecting tubule;
mostly straight
Medulla - straight proximals & distals
tubules & no
Collecting duct
corpuscles
Papilla with surface
columnar epithelium Papillary duct
Minor calyx lined with
transitional epithelium
Nephron
Nephron
2 major parts to the
nephron
Renal Corpuscle
Renal Tubule
Nephron
Renal corpuscle
site of plasma filtration
2 components
glomerulus
tuft of capillary loops
fed by afferent arteriole
drained by efferent
arteriole
glomerular (Bowman's) capsule
double walled cup lined by simple squamous epithelium
outer wall (parietal layer) separated from inner wall (visceral layer =
podocytes) by capsular (Bowman's) space
as blood flows through capillary tuft – filtration occurs
water and most dissolved molecules pass into capsular space
large proteins and formed elements in the blood do not cross
Nephron
DCT
Renal tubule - where
filtered fluid passes PCT
from capsule
proximal convoluted
tubule (PCT)
loop of Henle (nephron
loop)
distal convoluted tubule
(DCT) ducts
short connecting tubules
Loop
collecting ducts
merge to papillary duct
then to minor calyx
Nephron
Cortical neprhons
80-85% of nephrons
Short loops
Juxtamedullary
nephrons
15-20% of nephrons
Longer loops and H2O
increased
involvement in the
reabsorption of
water
Renal Corpuscle Histology
Endothelium of glomerulus
Single layer of capillary endothelium with fenestrations
Prevents RBC passage; WBCs use diapedesis to get out
Renal Corpuscle Histology
Basement membrane of glomerulus
Between endothelium and visceral layer of glomerular
capsule
Prevents passage of large protein molecules
Renal Corpuscle Histology
Filtration slits in podocytes
Podocytes
specialized epithelium of visceral layer
footlike extensions with filtration slits between extensions
Restricts passage of medium-sized proteins
Renal Corpuscle Histology
PCT - cuboidal cells with
Tubule Histology apical microvilli
Descending loop, and
beginning of ascending
loop
simple squamous epithelium
water permeable
Remainder of ascending
limb of the loop
cuboidal to low columnar
epithelial cells
DCT, collecting ducts
cuboidal with specialized cells
principal cells - sensitive to
ADH (antidiuretic hormone)
Renal Blood Supply
Important vessels
Renal arteries
20-25% of resting
CO
1200 ml/min
Segmental arteries
Interlobar arteries -
through columns
Arcuate arteries
Interlobular arteries
Afferent arterioles -
each renal corpuscle
receives one
Glomerular capillaries
Efferent arterioles -
drain blood from
glomerulus cortex
--------
Peritubular caps - around medulla
cortical nephrons
Vasa recta - long networks
from the efferent arteriole
around the loop of Henle
(juxtamedullary nephrons)
Vasa
recta
Renal Blood Supply
Viens
Interlobular veins
Arcuate veins
Interlobar veins
Segmental veins
Renal veins -
exits hilus
Renin-Angiotensin System
Juxtaglomerular apparatus (JGA)
Macula Densa (MD) cells
Monitor filtrate flow and osmotic
pressure in the distal tubule
If either are low, there may be
insufficient filtration and/or low blood
pressure/low blood volume
Vasodilate afferent arteriole JG
Stimulate JG cells to release renin
Both JG and MD cells work together MD
to regulate blood pressure and
blood volume
Distal
Convoluted
Tubule
Conclusion
Filtration barrier
Mesangial cells
Podocytes
JG apparatus