Kidney

LOCATION:
  • Located high in the abdominal cavity, one on each side of the spine, and lie in a retroperitoneal position at a slightly oblique angle.
  • The asymmetry within the abdominal cavity, caused by the position of the liver, typically results in the right kidney being slightly lower and smaller than the left, and being placed slightly more to the middle than the left kidney.
  • The left kidney is approximately at the vertebral level T12 to L3, and right is slightly lower.
  • Renal angle lies between 12th rib and lateral border of sacrospinalis
  • The right kidney sits just below the diaphragm and posterior to the liver.
  • The left sits below the diaphragm and posterior to the spleen.
  • On top of each kidney is an adrenal gland.
  • The upper parts of the kidneys are partially protected by the 11th and 12th ribs.
  • Each kidney, with its adrenal gland is surrounded by two layers of fat: the perinephric fat present between renal fascia and renal capsule and paranephric fat superior to the renal fascia.
STRUCTURE:
  • Bean-shaped structure with a convex and a concave border.
  • Recessed area on the concave border is the renal hilum, where the renal artery enters the kidney and the renal vein and ureter leave.
  • Surrounded by tough fibrous tissue, the renal capsule, which is itself surrounded by perirenal fat (adipose capsule), renal fascia, and pararenal fat (paranephric body). The anterior (front) surface of these tissues is the peritoneum, while the posterior (rear) surface is the transversalis fascia.
  • The superior pole of the right kidney is adjacent to the liver.
  • For the left kidney, it is next to the spleen. Both, therefore, move down upon inhalation.
  • Parenchyma of the kidney is divided into two major structures:
  1. Outer renal cortex and
  2. Inner renal medulla.
  • Shape of eight to 18 cone-shaped renal lobes, each containing renal cortex surrounding a portion of medulla called a renal pyramid (of Malpighi).
  • Between the renal pyramids are projections of cortex called renal columns (or Bertin columns).
  • Nephrons, the urine-producing functional structures of the kidney, span the cortex and medulla.
  • The initial filtering portion of a nephron is the renal corpuscle which is located in the cortex.
  • This is followed by a renal tubule that passes from the cortex deep into the medullary pyramids.
  • Part of the renal cortex, a medullary ray is a collection of renal tubules that drain into a single collecting duct.
  • The tip, or papilla, of each pyramid empties urine into a minor calyx; minor calyces empty into major calyces, and major calyces empty into the renal pelvis.This becomes the ureter. At the hilum, the ureter and renal vein exit the kidney and the renal artery enters.
  • Hilar fat and lymphatic tissue with lymph nodes surrounds these structures.
  • The hilar fat is contiguous with a fat-filled cavity called the renal sinus. The renal sinus collectively contains the renal pelvis and calyces and separates these structures from the renal medullary tissue.
RELATIONS:
Anterior Relations:

Left Kidney Right Kidney
Supra - renal gland
Small Intestine (jejunum) & Stomach
Spleen & Its vessels, Splenic flexure
Descending colon, Pancreas
Supra - renal gland
Jejunum
Second part of duodenum
Hepatic flexure of colon & Liver
Posterior Relations (of both kidneys)

Muscles(4) Nerves(3) Ligaments(2) Vessel & Rib(eachl}
Diaphragm
Psoas major
Quadratus lumborum
Transversus abdominis
Subcostal
NIliohypogastric
NIlioinguinal. N
Medial arcuate
Lateral arcuate
Subcostal
Vessels12th rib- upper pole of right kidney
Left kidney is also related to 11th rib
DEVELOPMENT:
  • The mammalian kidney develops from intermediate mesoderm in Sacral region
  • Ureteric bud (mesonephros) arise from mesonephric duct and gives rise to collecting system of kidney (renal pelvis, major and minor calyces, collecting tubule) and ureter. Metanephric mesoderm (blastema or metanephors) arise from nephrogenic cord which in turn is derived from intermediate mesoderm. It gives rise to excretory unit (nephron), i.e. glomeruli, PCT, Loop of henle and DCT.
  • Kidney development, also called nephrogenesis, proceeds through a series of three successive developmental phases: the pronephros, mesonephros, and metanephros.
  • The neonatal kidney achieves concentrating ability equivalent to adult's kidney by 1year
Exam Question
  • Right kidney is lower & distal than the left kidney
  • Right kidney is related to duodenum
  • The neonatal kidney achieves concentrating ability equivalent to adult's kidney by 1year
  • Development of human kidney begins in Sacral region
  • Between the renal pyramids are projections of cortex called renal columns (or Bertin columns).
  • Extent of kidney is from T12-L3
  • Kidney is supported by perirenal fat, renal fascia, and pararenal fat
  • Renal angle lies between 12th rib and lateral border of sacrospinalis
  • Excretory system of kidney is derived from Metanephros
  • Kidney develops from Metanephros, Mesonephric duct(Mesonephros), Blastema.
  • Collecting part of kidney develops from mesonephros or Ureteric bud
Don't Forget to Solve all the previous Year Question asked on Kidney