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.
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.
Kidney is supported by:
1- coverings (as above)
2- renal vascular pedicle,
3- abdominal muscle tone,
4- bulk of the abdominal viscera.
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
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.
Posterior (both kidneys)
Below: psoas ms, quadratus lumburum & transversus abdominis (from med. To lat.)
Anterior (different bet. Rt & LT)
Above: suprarenal, Liver (Rt lobe)
Hilum: duodenum 2nd part
Below: Rt colic flex., jejunum
Above: suprarenal, stomach, spleen
Below: Lt colic flexure, jejunum
Cortex is composed mainly of nephrons
Medulla is composed mainly of collecting ducts
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.
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.
Very important bec. main function of kidney is regulation of volume & composition of blood
& for nephrectomy & nephrolithotomy.
Renal arteries carry 20% of COP
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 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:
· 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).
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
3 lymphatic plexuses (parenchymal, subcapsular & perinephric) → Lumbar(Retroperitoneal) L.N.s (Rt → interaortocaval, precaval & Lt → paraaortic),
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.
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
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.
from renal arteries
The veins are paired with the arteries.
renal calices, pelvis, and upper ureters → lumbar lymph nodes.