PAIR OF EXCRETORY ORGANS
Excrete the end products of metabolism and
Maintaining electrolyte and water balance in
the tissue fluids
Endocrine functions- erythropoietin, renin
Situated posteriorly behind the peritoneum
on each side of the vertebral column
Superiorly -upper border of the
inferiorly– center of body of L3
The right is usually slightly inferior to the left.
Left is a little longer and narrower.
Left lies nearer the median plane.
11 cm in length, 6 cm in breadth and 3 cm in
The left kidney may be 1.5 cm longer
weight -150 g in men and 135 g in women
In fetus and newborn, the kidney normally
has 12 lobules.
1. Fibrous capsule:
Closely invests the kidney and renal sinus
Can be easily stripped off
2. Perirenal fat
Adipose tissue outside the capsule
Thickest at the borders
Dense, elastic connective tissue sheath
enveloping kidney and suprarenal gland
together with perirenal fat.
Posterior fascia of zuckerkandl and the
anterior fascia of gerota, fuse laterally
forming lateral conal fascia
Lateral conal fascia continues anterolaterally
behind the colon to blend with the parietal
Single multilaminated structure which is
fused posteromedially with the muscular
fasciae of psoas major and quadratus
Extends anteromedially behind the kidney as
a bilaminated sheet
Divides into a thin anterior lamina, passing
around the front of the kidney -anterior
Thicker posterior lamina which continues
anterolaterally as the lateral conal
fascia, fusing with the parietal peritoneum.
In the midline superiorly - anterior and
posterior renal fasciae fuse and attached to
the crura of their respective
Superior aspect of the perirenal space is
open and in continuity with the bare area of
the liver on the right and the subphrenic
extraperitoneal space on the left.
The posterior fascial layer blends bilaterally
with the fascia of psoas major and
quadratus lumborum as well as the inferior
Right - anterior fascial layer blends with the
right inferior coronary ligament at the level of
the upper pole of the kidney and bare area of
Left - anterior layer fuses with the
gastrosplenic ligament at the level of the
Anterior perirenal fascia extends across the
midline in front of the great vessels
Below this level the two fasciae merge and
attached to the great vessels or iliac vessels
Laterally the anterior and posterior leaves
fuse with the iliac fascia, and medially with
the periureteric connective tissue.
Inferior apex of the cone is open anatomically
towards the iliac fossa
Two poles, superior and inferior
Sup- broad, inf- pointed.
Two surfaces- anterior and posterior.
Anterior – irregular and posterior surface –
Lateral borders- convex
Medial borders- convex adjacent to the
poles, concave between them showing a
depression, the hilum and slope
renal vein (anterior)
renal artery (intermediate)
pelvis of the kidney (posterior).
Right kidney –
Right suprarenal gland
Below this - right lobe of the liver
Narrow medial area - descending part of the
Laterally with the retroperitoneal right colic
Medially with part of the intraperitoneal small
Lateral border –
Rt lobe of liver
Hepatic flexure of the colon
Medial area of the superior pole - left
Lateral half of the anterior surface – spleen
Central quadrilateral area - retroperitoneal
pancreas and splenic vessels
Between the suprarenal and splenic areas stomach separated by a layer of peritoneum
Below the pancreatic and splenic areas, a
narrow lateral strip -retroperitoneal left colic
flexure and the beginning of the descending
extensive medial area - intraperitoneal loops
Embedded in fat and devoid of peritoneum.
Superiorly are the diaphragm and the medial
and lateral arcuate ligaments.
More inferiorly, from medial to lateral
Aponeurotic tendon of transversus
Subcostal, iliohypogastric, and ilioinguinal
The upper pole of the right kidney is level
with the 12th rib, and that of the left with the
11th and 12th ribs.
The diaphragm separates the kidney from the
pleura, which descends to form the
Internal pale medulla and external reddish
Renal medulla consists of striated, conical
renal pyramids, their bases peripheral, their
apices converging to the renal sinus which is
the space around the renal pelvis extending
to the interior.
At the renal sinus they project into minor
calyces as papillae.
Renal cortex is subcapsular.
Arching over the bases of the pyramidscortical arches or lobules and extending
between them towards the renal sinus as
Pyramid + cortical arch forms a lobe of the
The cortex close to the medulla is sometimes
termed the juxtamedullar cortex.
Hilum of the kidney leads into a central renal
sinus, lined by the renal capsule
Renal pelvis, vessels and fat.
Within the renal sinus, collecting tubules open
onto the summits of the renal papillae to drain
into minor calyces, which are funnel-shaped
expansions of the upper urinary tract
Each minor calyx surrounds either a single
papilla or rarely, groups of two or three papillae.
The minor calyces unite with their neighbours to
form two to three major calyces
Calyces drain into the infundibula
Renal pelvis is normally formed from the
junction of two infundibula, from upper and
lower pole calyces
There may be a third draining the calyces in
the mid-portion of kidney.
Funnel-shaped renal pelvis tapers as it
passes inferomedially, traversing the renal
hilum to become continuous with the ureter
About 20% of the cardiac output
Arises from abdominal aorta
Near the renal hilum, each artery divides into
an anterior and a posterior division, and
these divide into segmental arteries supplying
the renal vascular segments.
Accessory renal arteries are common (30%)
and usually arise from the aorta above or
below (most commonly below) the main renal
artery and follow it to the renal hilum
Subdivisions of the renal arteries are
described sequentially as
5. Interlobular arteries
6. Afferent and efferent glomerular arterioles
Five arterial segments have been identified
Apical segment - anteromedial region of the
Superior (anterior) segment - rest of the
superior pole and the central anterosuperior
Inferior segment -whole lower pole.
Middle (anterior) segment - between anterior
and inferior segments.
Posterior segment - whole posterior region
between the apical and inferior segments.
Branches of segmental arteries are
lobar, usually one to each renal pyramid.
Each lobar artery subdivide into two or three
interlobar arteries, extending towards the
cortex around each pyramid.
At the junction of the cortex and
medulla, interlobar arteries dichotomize into
arcuate arteries which diverge at right angles
over the base of pyramid
Divides further into interlobular arteries
which diverge radially into the cortex.
Terminations of adjacent arcuate arteries do
not anastomose but end in the cortex as
additional interlobular arteries
lateral rami of interlobular arteries
Efferent glomerular arterioles from most
glomeruli (except at juxtamedullary
and, sometimes, at intermediate cortical
levels) soon divide to form a dense
peritubular capillary plexus around the
proximal and distal convoluted tubules
Two sets of capillaries – glomerular and
vascular supply of the renal medulla is largely
from efferent arterioles of juxtamedullary
Efferent glomerular arterioles passing into the
medulla divides into 12–25 descending vasa
recta close to henle’s loop and collecting
Venous ends of capillaries converge to the
ascending vasa recta, which drain into
arcuate or interlobular veins.
Proximity of descending and ascending
vessels with each other and adjacent ducts
provides the structural basis for the
countercurrent exchange and multiplier
Venous ends of the peritubular plexuses
converge to join interlobular veins, one with
each interlobular artery.
Interlobular veins pass to the
corticomedullary junction end in arcuate
veins (which accompany arcuate arteries), and
anastomose with neighbouring veins.
Arcuate veins drain into interlobar
veins, which anastomose and form the renal
Collecting vessels from the intra-renal plexus
form four or five trunks which follow the
renal vein to end in the lateral aortic nodes
Rami from the coeliac ganglion and
plexus, aorticorenal ganglion, lowest thoracic
splanchnic nerve, first lumbar splanchnic
nerve and aortic plexus form a dense plexus
of autonomic nerves around the renal artery.
Kidney is composed of 1 to 3 million
uriniferous tubules, bounded by a delicate
connective tissue with blood
vessels, lymphatics and nerves.
Two embryologically distinct parts
Collecting duct-concentration of urine
1.Renal corpuscle - filtration from the plasma,
2.Renal tubule - selective resorption from
the filtrate to form the urine
Small rounded structures 0.2 mm in diameter
Each has a central glomerulus of vessels and
a glomerular (bowman's) capsule, from which
the renal tubule originates.
A glomerulus is a collection of convoluted
capillary blood vessels supplied by an
An efferent arteriole emerges from the same
point, the vascular pole of the corpuscle
Blind expanded end of a renal tubule
deeply invaginated by the glomerulus.
lined by a simple squamous epithelium on its
outer (parietal) wall
glomerular, juxtacapillary (visceral) wall is
composed of specialized epithelial podocytes
branch to form secondary or tertiary
processes and give rise to terminal pedicels
separated by narrow (25 nm) gaps, the
Luminal membrane and the slit diaphragm
are covered by a dense surface coat rich in
sialoglycoproteins – negative charge.
Proximal convoluted tubule is connected to
the capsule by a short neck
This straightens as it approaches the
medulla-becomes descending thick limb of
loop of henle and then ascending limb by an
Loop of henle are narrower and thin-walled in
medulla - descending and ascending thin
The tubule wall shows a focal thickening, the
macula densa, where it comes close to the
vascular pole of its parent glomerulus at the
start of the convoluted part of the distal
The nephron finally straightens once more as
the connecting tubule, which ends by joining
a collecting duct
PROXIMAL CONVOLUTED TUBULE
Lined by cuboidal or low columnar epithelium
Brush border of tall microvilli on its luminal
Cytoplasm of proximal tubular cells is
eosinophilic and nuclei are euchromatic and
Cytoplasm is rich in mitochondria
LOOP OF HENLE
Thin segment (30 μm in diameter), lined by
low cuboidal to squamous cells
Thick segment (60 μm in diameter) composed
of cuboidal cells
Cells of the DISTAL TUBULE are cuboidal and
resemble those in the proximal tubule.
They have few microvilli
Simple cuboidal or columnar epithelium
1 in 1200 individuals and results from failure
of metanephric blastema to join with a
ureteric bud on the affected side
absence of the ipsilateral vas deferens and/or
epididymis with other congenital anomalies
including imperforate anus, cardiac valvular
anomalies and oesophageal atresia
Failure of the kidney to ascend into the renal
fossa in utero
1 in 2500 live births
CROSSED RENAL ECTOPIA
normal location of the ureteric orifices within
two renal masses are on the same side
1 in 400 individuals.
A transverse bridge of renal tissue, the
isthmus, connects the two renal masses.
lies between the inferior poles anterior to the