Renal anatomy and circulation discussed, with reference to Brenner, useful for nephrology residents.

1. RENAL ANATOMY &
CIRCULATION
Dr DEEP MUKHOPADHYAY

2. INTRODUCTION
Overview
Gross anatomy
Blood supply / venous drainage
Microscopy/ Histology

3. OVERVIEW
Paired Retroperitoneal Organ
Loacation : Between T12- L3
Right kidney is slightly more caudal
Left kidney is usually somewhat longer
and narrower
Weight : 125 to 170 g in adult males &
115 to 155 g in adult females
Measurements : 11 to 12 cm long, 5.0
to 7.5 cm wide, and 2.5 to 3.0 cm thick.
Less than 9cm- small kidney

4. ANTERIOR RELATIONS POSTERIOR RELATIONS

5. GROSS ANATOMY
A granular outer region - the CORTEX
1 cm in thickness
Cortex extends downward between the
individual pyramids to form the columns of
Bertin.
MEDULLARY RAYS :cortical collecting
ducts, the straight segments of the proximal
tubules, and the cortical thick ascending
limbs (TALs) of loop of Henle, aligned
together

6. A striated inner region, the MEDULLA -composed of renal pyramids -
conical tissue masses with the base of each pyramid at the
corticomedullary boundary and the apex extending toward the renal
pelvis, forming a papilla.
Each pyramid contains the descending and ascending limbs of the
renal tubules and the collecting tubules
On the tip of each papilla is the area cribrosa, where the distal ends of
collecting ducts (ducts of Bellini) open into the renal pelvis.

7. Renal pelvis - expanded portion of the
upper urinary tract
Two- three extensions of the renal pelvis,
the major calyces which further divides
into several minor calyces. These parts
receive the urine discharged at the area
cribrosa of each renal pyramid.
The ureter - originate from the distal
renal pelvis at the ureteropelvic junction.
Ureters - 28 to 34 cm long and a mean
diameter of 1.8 mm.(max 3mm.)
SMC & interstitial cells- pacemaker
function

8. RENAL
FASCIA

9. BLOOD
SUPPLY

11. RENAL CIRCULATION

12. MICROCIRCULATION

13. VENOUS
DRAINAGE

14. NEPHRON
THE NEPHRON IS THE FUNCTIONAL UNIT OF
THE KIDNEY
Nephron = Renal corpuscle ( glomerulus and
Bowman’s capsule) + associated renal tubules upto
Distal connecting tubule.
900,000 to 1 million per kidney.
origin of the nephron is the metanephric blastema.

15. NEPHRON

17. TYPE OF
NEPHRONS
CORTICAL NEPHRONS JUXTA-MEDULAARY
NEPHRONS
85% 15%
Shorter loops of Henle
that bend within the inner
stripe of the outer
medulla.
long loops of Henle that
extend into the inner
medulla
No or very short
ascending thin limbs
Long descending and
ascending
thin limb segments
Efferent Arteriole - forms
peritubular capillaries
Efferent Arteriole - forms
vasa recta
Glomerulus - Small Glomerulus - Large

19. Cortex - arcuate vessels
OMo - terminal portion of
PSTs, TALs, and
collecting ducts.
Omi - TALs, descending
thin limbs, and collecting
ducts, but no proximal
tubules
IM - descending and
ascending thin limbs and
collecting ducts, but no
TALs

20. GLOMERULUS

21. LIGHT MICROSCOPY  Glomerulus - composed of a capillary
network lined by a thin layer of
endothelial cells, a central region of
mesangial cells with surrounding matrix
material, and the visceral epithelial
cells (podocytes) overlying the
capillaries.
 “Renal Corpuscle” - glomerulus and
Bowman’s capsule.
 The average diameter of a glomerulus
is approximately 200 μm.

22. LIGHT MICROSCOPY

23. GLOMERULAR
FILTRATION
BARRIER
1. Fenestrated Capillary
Endothelium
2. Glomerular Basement
Membrane (GBM)
3. Filtration Slit
Diaphragm between
the foot processes of
The Visceral Epithelial
Cells

24. ELECTRON MICROGRAPH

25. CAPILLARY
ENDOTHELIUM
Fenestrations- 70 to 100 nm in diameter
Glomerular endothelium is covered by a glycocalyx layer,
proteoglycans (syndecan and glypican) with
glycosaminoglycans (GAGs), secreted glycoproteins
(perlecan and versican), and secreted gags (hyaluronan),
which provide a negative charge.
Endogenous albumin is largely confined to the glomerular
capillary lumen and does not pass through the
endothelium.
Injection of hyaluronidase, a hyaluronan degrading
enzyme, in mice led to disruption of the glomerular
endothelial glycocalyx and leakage of albumin across the
endothelium.

26. GLOMERULAR
BASEMENT
MEMBRANE
3 layers
a central dense layer - the lamina densa
two thinner, more electron-lucent layers, the lamina
rara externa and the lamina rara interna
Thickness - in men -373 nm and in women - 326 nm
Primarily of type IV collagen, laminin, nidogen
(entactin), and heparan sulfate proteoglycans
The α3α4α5(IV)-α3α4α5(IV) network predominates n
the GBM, whereas the α1α2α1(IV)-α5α6α5(IV)
network is in Bowman’s capsule.
Both a size-selective and a charge-selective barrier

27. PODOCYTES
Podocytes (visceral epithelial cells) - the largest cells in the glomerulus. They
do not replicate
The cell bodies give rise to long cytoplasmic primary processes that branch
into secondary and tertiary processes, surround the capillaries, and finally
divide into foot processes.
The gap between adjacent foot processes is bridged by a thin structure called
the “filtration slit diaphragm”.
In glomerular diseases associated with proteinuria, the podocyte cytoskeleton
is disrupted, slit diaphragms are lost, and the interdigitating foot processes are
replaced by broad regions of podocyte processes covering the GBM. This is
called “foot process effacement”

28. SLIT DIAPHARGM
Bridges the 30–40 nm space - called the “filtration slit” between adjacent foot processes
Rodewald and Karnovsky proposed a porous zipper-like model for the SD.
Enhanced SEM revealed variable-shape pores in the center of the SD and no central filament. This
finding is more consistent with the SD as a heteroporous structure rather than the zipper-like model
role of the SD - as a size-selective element in the filtration barrier.

29. GLOMERULAR
FILTRATION
BARRIER

30. MESANGIUM
Mesangial Cells With Surrounding Matrix Provide
Scaffold For The Surrounding Glomerular Capillaries.
Possess An Extensive Array Of Microfilaments
Containing Actin, Myosin, And Α-actinin - Functional
Properties Of Smooth Muscle Cells
Mesangial Cell Has Contractile Properties And Is
Thought To Play A Role In The Regulation Of
Glomerular Filtration
Local Generation Of Autacoids, Such As
Prostaglandin E2, By The Mesangial Cell
Exhibit Phagocytic Properties
Generation And Metabolism Of The Extracellular
Mesangial Matrix

31. JUXTA-
GLOMERULAR
APPARATUS

32. Represents a major structural component of the renin–angiotensin system and
contributes to the regulation of glomerular arteriolar resistance and glomerular
filtration.
Vascular components - terminal portion of the afferent arteriole, the initial portion
of the efferent arteriole, and the extraglomerular mesangium.
Tubular component - the macula densa, located in the terminal portion of the TAL
that lies between the afferent and efferent arterioles
Extraglomerular mesangium, also called the polar cushion- polkissen or the lacis
Specialized cell types of the JGA include
1- juxtaglomerular granular cells
2-the agranular extraglomerular mesangial cells
3- the epithelial cells that make up the macula densa.

33. PROXIMAL
TUBULE
1- Proximal Convoluted Tubule (PCT - Pars
Convoluta), which originates at the glomerular
urinary pole , located in cortex
2- Proximal Straight Tubule (PST - Pars Recta)-
distal to the PCT and located in the medullary ray in
the cortex
Length- 14 mm
S1- initial 2/3 of PCT
S2 – reminder 1/3 of PCT and initial of PST
S3 – reminder of PST
Major function – reabsorption

34. S1 SEGMENT OF PROXIMAL
TUBULE
 A tall brush border
A prominent endocytic–lysosomal
apparatus
Extensive invaginations of the
basolateral plasma membrane
Numerous long mitochondria
aligned among the basolateral
plasma membrane infoldings.

35. S2 SEGMENT OF A
PROXIMAL TUBULE
The brush border is shorter than in
the S1 segment.
Mitochondria are numerous and
generally aligned with the
basolateral plasma membrane
infoldings.
Numerous small lateral processes at
the base of the cell

36. S3 SEGMENT OF A
PROXIMAL TUBULE
The brush border is tall
The endocytic–lysosomal apparatus
is less prominent than in the S1 and
S2
Mitochondria are scattered randomly
throughout the cytoplasm

37. THIN LIMBS OF HENLE
Type I Epithelium – descending thin limb of short-looped
nephrons, smooth
Type II Epithelium- long-looped nephrons contains in the outer
medulla, extensive lateral and basal interdigitations, a “leaky”
epithelium, mitochondria, are more prominent
Type III Epithelium- inner medulla, thinner and simpler in
structure
Type IV Epithelium- generally low and flat, relatively few
organelles
Thin descending limb- water channel, aquaporin-1 present-
highly permeable to water

38. TYPE II EPITHELIUM
OF THE THIN LIMB
OF LOOP OF HENLE
taller and has more
organelles, prominent
apical plasma membrane
microprojections, and
complex basolateral
plasma membrane
infoldings.

39. TYPE III
EPITHELIUM
• prominent apical plasma
membrane
microprojections. It is a
very low, flat epithelium
with relatively few
basolateral plasma
membrane infoldings
compared with type II
epithelium

40. DISTAL
TUBULE
Standard nomenculture- Distal Tubule- TAL of loop of henle (Pars
Recta) + the Distal Convoluted Tubule -DCT (Pars Convoluta)
In Micropuncture Studies- the “early” or “Bright” distal tubule - DCT
plus a short segment of TAL
“Late” or “granular” distal tubule - Connecting Tubule and the initial
portion of the collecting duct in the cortical labyrinth, the ICT.
Whole DCT - NCC present
DCT- Na+–Ca2+ exchanger (NCX1) and vitamin D–dependent
Calcium-Binding protein, Calbindin-D28k.
Late DCT - ENAC and TRPV5 present
DCT - highest Na+-K+-ATPase activity

41. CORTICAL THICK ASCENDING
LIMB (TAL)
Numerous Short Apical
Microprojections
Deep, Complex Invaginations Of The
Basal Plasma Membrane Extend Into
The Apical Region Of The Cell And
Enclose Elongated Mitochondrial
Profiles
Few Organelles And Little Cytoplasm

42. DISTAL CONVOLUTED TUBULE
(DCT)
DCT Cells Is Similar To Thick
Ascending Limb (TAL) Cells
DCT Cells Are Considerably Taller,
With
Numerous Basal Plasma Membrane
Infoldings And Mitochondria Interposed
Between The Nucleus And The
Basement Membrane.

43. CONNECTING
SEGEMNT
1- CNT Cell- Which Occurs Only In This
Segment, Is Tall With An Apically Located
Nucleus, More Cytoplasm And Organelles.
2-Intercalated Cells- Which Account For
Approximately 40% Of The Cells.
3 Subtypes Of Intercalated Cells
1- Type A
2 - Type B
3- Non-a Non-b

44. CNTs Of Superficial
Nephrons Continue
Directly Into ICTs,
Whereas CNTs From
Midcortical And
Juxtamedullary
Nephrons Join To Form
Arcades That Ascend In
The Cortex And Continue
Into ICTs.

45. COLLECTING
DUCT
1- ICT - initial collecting tubule
2- CCD - cortical collecting duct
3- OMCD - outer medullary collecting duct-
OMCDo & OMCDi
4- IMCD - inner medullary collecting duct- IMCDt
& IMCDi
In the ICT, CCD, OMCD, and IMCD, there are
two major cell types:
1- Principal Cells
2- Intercalated Cells

46. INTERSTITIUM
Compartments - the peritubular interstitium and the periarterial connective tissue
Peritubular interstitium - interstitial cells, extracellular matrix and interstitial fluid interposed
between the basement membranes of the renal tubules and peritubular capillaries
Periarterial interstitium - a layer of connective tissue and interstitial cells surrounding the
arteries in the renal cortex [can produce renin]
Fibroblasts, also known as “stellate” or “sustentacular cells,” are the most abundant in the
peritubular interstitium.
In inflammation-myofibroblast. In medulla-numerous lipid inclusions[COX2+, PGE2 synthesis]
Pericytes are contractile cells intimately associated with the capillaries in both the renal
cortex(5NT+) and medulla
Cells of the immune system - the most common are dendritic cells (MHC 2 +)

47. LYMPHATICS
capsular, subcapsular and
intrarenal components
Right kidney lymphatics drain into
the Paracaval, Precaval,
Interaortocaval, and Retrocaval
nodes,
Left kidney lymphatics drain into the
Preaortic, Paraaortic, and
Retroaortic nodes.

48. INNERVATION
• Sympathetic- T6 to L2
• The renal nerves enter the kidney at the hilum and
run with the renal arteries into the kidney in
interlobar, arcuate, and interlobular arteries and in
afferent and efferent arterioles.
• Renin secretion is modulated by renal sympathetic
nerve activity.