KIDNEYS
Gross Appearance
Bilateral bean shaped retroperitoneal
organ
lie along lat. borders of psoas
muscles and are therefore obliquely placed (lower pole lat.).
liver → RK lower than LK.
Size: 12 X 6 X 3 cm
weight = 150 g.
Renal Hilum is shallow depression at cenre of
medial border, transmits:
- renal vein: ant.
- Renal artery: middle
- Renal pelvis: posterior (post. segmental pass behind upper part of pelvis)
- & lymphatics & pelvis pass.
Renal sinus is space interior to hilum, contain
major vessels, pelvis, majr calyces, minor calyces & sinus fat.
Coverings
1-
Renal capsule
(fibrous & adherent to parenchyma)
2-
Perinephric fat:
inside Gerota’s f.
3-
Perirenal (Gerota’s) fascia:
· surround
kidney, perinephric fat & adrenal
· 2
laminae:
Ø anterior lamina ®
fascia of Toldt (thin)
Ø posterior lamina ® fascia of
Zuckerkandl (thicker)
· encloses
the kidney on all sides except inferiorly (remains an open potential
space)
· Medially:
fuse with the contralateral side across the midline.
4-
Paranephric fat:
outside Gerota’s f.
Supported
Kidney is supported by:
1- coverings (as
above)
2- renal vascular
pedicle,
3- abdominal muscle
tone,
4- bulk of the
abdominal viscera.
Supporting Tissue
The renal stroma is composed of loose
connective tissue and contains blood vessels, capillaries, nerves, and
lymphatics.
average descent on inspiration or upright
position = 4-5 cm.
Lack of mobility = abnormal fixation
(eg, perinephritis),
extreme mobility = not necessarily
pathologic.
Longitudinal section: composed of:
Renal capsule: thick & penetrated
by capsular vessels
Renal parenchyma
1- cortex (outer), homogeneous appearance. columns
of Bertin are parts of cortex projecting between the papillae and fornices toward
renal sinus.
2- medulla (central), formed of pyramids (converging
collecting renal tubules), their tips called papillae → drain into the minor calices (at tip of
papillae or into pelvis itself).
3- Pelvicalyceal system: internal calices and
pelvis.
Relations:
Posterior (both kidneys)
Above: diaphragm
Below: psoas ms, quadratus lumburum
& transversus abdominis (from med. To lat.)
Anterior (different bet. Rt & LT)
Rt kidney
|
Lt kidney
|
Above: suprarenal, Liver (Rt lobe)
Hilum: duodenum 2nd part
Below: Rt colic flex., jejunum
|
Above: suprarenal, stomach, spleen
Middle: pancreas
Below: Lt colic flexure, jejunum
|
Microscopic anatomy
Cortex is composed mainly of nephrons
Medulla is composed mainly of
collecting ducts
Nephron
The functioning unit of the kidney
composed of a tubule that has both
secretory and excretory functions
1- secretory part of nephron: in the
cortex and consists of:
a) renal corpuscle is composed of the
vascular glomerulus + Bowman's capsule.
b) secretory part of the renal tubule:
PCT, LH & DCT
2- excretory part of nephron: in the
medulla = collecting tubule (CD),
continuous with DCT. It empties its contents through the tip (papilla) of a
pyramid into a minor calyx.
Nephrons are 2 types:
Cortical nephrons: all parts in cortex
Juxtamedullary nephrons: glomerulus
close to cortico-medullary junction & other parts in medulla.
Renal corpuscle:
1-
glomerulus (capillary tuft) projects into Bowman’s
capsule, supplied by afferent a. (from interlobular a.) & drained by
efferent a. (to peritubular capillaries)
2-
Bowman's capsule: concave
consists of 2 layers:
Visceral (inner): endothelium &
epithelial cells (podocytes)→ foot processes(pedicles) that cover endothelial
pores
Parietal
(outer): simple squamous epith.
Bowman
space: space bet. both layers, continuous with epithelium of PCT.
PCT: (longest part): cuboidal epith. covered
by microvilli
LH: 2 limbs
thin descending limb: descend to
medulla
thick ascending limb: cuboidal &
columnar epith.
DCT: cuboidal epith.has straight part
(contain macula densa cells adjacent to glomerulus) & convoluted part, ends
in CD
DCT lie adjacent to afferent arteriole
→ modify cells of both forming JGA (juxtaglomerular apparatus) formed by:
macula densa cells (in DCT) + juxtaglomerular cells (in afferent arteriole) +
CD: straight, in renal pyramid (medulla)
→open into papillae in terminal duct of Bellini
Tubule is name of parts covered by cuboidal
epith.
Blood Supply
Very important bec. main function of
kidney is regulation of volume & composition of blood
& for nephrectomy &
nephrolithotomy.
Renal arteries carry 20% of COP
A. Arterial
renal artery is a branch of the aorta at T2 (just
below sup.mes.a.)
→ branch before it reaches renal hilum
→ 2 branches (post. segmental (1st)
& ant. segmental) →
branches lie in hilum between renal vein (anterior) & pelvis (posterior).
·
Posterior segmental branch (no branches)→ mid segment of the posterior surface
(first
it lies bet. RV & pelvis →then→ pass post to upper part of pelvis).
·
Anterior segmental branch → upper and lower poles + entire anterior surface via 3-4
branches:
Ø
apical,
Ø
upper,
Ø
middle,
Ø
lower (basal)
→ Inside parenchyma, main branches
further divides into → interlobar
arteries, which ascend in the columns of Bertin (between the pyramids) → arcuate arteries (arch along the base
of the pyramids) → interlobular
arteries→ afferent arterioles
→ glomeruli → efferent arterioles → peritubular capillaries → supply blood
to rest of nephron → Vasa recta are long vessels parallel to LH.
·
kidney has 4 vascular segments:
Ø
anterior
Ø
posterior
Ø
apical
Ø
basal
·
The renal arteries are all end arteries, If ligated →
infarction
·
Brodel avascular white line: longitudinal true avascular plane
between the posterior and anterior segmental & lies just posterior to the
lateral aspect of the kidney (on post. surface of kidney). (Variable position)
·
In duplication: each segment have its own arterial supply
(2 branches from aorta).
B. Venous
paired with the arteries, but intercommunicating
(any of them will drain the entire kidney if the others are ligated).
Peritubular capillaries → interlobular
veins → arcuate vs → interlobar vs → segmental vs (3-5)→ main renal vein
Rt renal vein: no tributaries outside kidney (+/-)
Lt renal vein: tributaries, Lt adrenal (above) &
Lumbar veins (behind) & Lt gonadal (below)
accessory renal vessels are common
& may compress ureter → UPJO.
Nerve Supply (autonomic)
from the renal plexus. (over aorta
just above renal a.) which receives:
Ø
Sympathetic from T11- L2
Ø
Parasympathetic from vagus
enter through hilum & accompany
the renal a. in renal parenchyma.
Kidney share autonomic innervation
with other organs → GIT S/S with GUT ds
Lymphatics
3 lymphatic plexuses (parenchymal,
subcapsular & perinephric) → Lumbar(Retroperitoneal) L.N.s (Rt → interaortocaval,
precaval & Lt → paraaortic),
CALYCES, RENAL PELVIS
Gross Appearance
1. Calices: tips of the minor calices
(8-12) indented (cupped) by pyramids→ unite
to form 2 or 3 major calices, → unite to form
renal pelvis (calyx may enclose >1 papillae)
- Calyx neck = infundibulum.
2. Renal pelvis: may be entirely
intrarenal or partly intrarenal and partly extrarenal. Inferomedially, it
tapers to form the ureter.
Relations
1. Calices: are intrarenal and
intimately related to renal parenchyma.
2. Renal pelvis: If partly extrarenal,
it lies along lateral border of psoas muscle and on quadratus lumborum muscle;
the renal vascular pedicle is placed just anterior to it.
left pelvis lies at the level of L1 or
L2
right pelvis is a little lower (L2).
Calyceal anatomy on IVU (LAMP)
Lateral calyces → Anterior
Medial calyces → Posterior
End-on calyces → posterior
Histology
Mucosa: transitional epith. over lamina
propria (loose connective and elastic tissue).
Musculosa: helical and longitudinal smooth muscle
fibers. not arranged in definite layers.
Adventitia: fibrous connective tissue.
Blood Supply
A. Arterial
from renal arteries
B. Venous
The veins are paired with the
arteries.
Lymphatics
renal calices, pelvis, and upper
ureters → lumbar lymph nodes.
