The Kidney Anatomy is intricate, designed to efficiently filter blood, remove waste, maintain electrolyte balance, and regulate blood pressure.
Each kidney is a bean-shaped organ, approximately the size of a fist, located on either side of the spine, just below the rib cage.
The kidneys are part of the upper urinary tract and play a crucial role in the body's urinary system.
External Anatomy
1) Location
The kidneys are retroperitoneal organs, meaning they are located behind the peritoneum (a lining of the abdominal cavity).
They are situated on either side of the vertebral column; the right kidney is typically slightly lower than the left due to the presence of the liver.
2) Size and Shape
Each kidney is roughly 12 centimeters (about 4.5 inches) long, 6 centimeters (2.5 inches) wide, and 3 centimeters (1.2 inches) thick, resembling a large bean.
3) Renal Capsule
A tough, fibrous membrane surrounding each kidney, protecting it from trauma and infection.
4) Renal Hilum
The medial indentation where the renal artery enters, and the renal vein and ureter exit the kidney. It acts as a gateway for blood vessels and nerves.
Internal Anatomy
1) Renal Cortex
The outer layer of the kidney, granular in appearance, containing glomeruli, proximal and distal convoluted tubules, and blood vessels.
2. Renal Medulla
The inner layer, consisting of 10 to 18 renal pyramids. These cone-shaped tissues house the loops of Henle and collecting ducts. The apex of each pyramid, called the renal papilla, points towards the renal pelvis.
3) Renal Columns
Inward extensions of cortical tissue separating the renal pyramids. These columns provide a path for blood vessels to enter and exit the cortex.
4) Renal Pelvis
A funnel-shaped space in the center of the kidney that collects urine from the major calyces and channels it into the ureter.
5) Calyces
The renal pelvis is divided into major calyces, which further divide into minor calyces. These cup-shaped structures enclose the tips of the renal pyramids, collecting urine and draining it into the renal pelvis.
Blood Supply
1) Renal Arteries
Branches from the abdominal aorta, delivering oxygenated, nutrient-rich blood to each kidney.
2) Renal Veins
Carry deoxygenated, filtered blood from the kidneys back to the inferior vena cava.
The kidneys receive a significant amount of blood flow, essential for their filtration and excretion functions.
Microscopic Structure
Nephrons
The functional units of the kidney, with approximately 1 to 1.5 million nephrons per kidney.
Each nephron contains a glomerulus (a capillary bed that filters blood) and a renal tubule, where the filtrate is processed and converted into urine.