Anatomy of the Kidney  

The kidneys excrete excess water, salts and waste products of metabolism2. As such, they have a major role in controlling the water and electrolyte balance within the body and regulating the acid-base balance of blood1. The kidney is also an endocrine organ that produces and secretes hormones such as renin (to activate the rennin-angiotensin-aldosterone system), calcitriol (a metabolite of vitamin D3) and erythropoietin (to stimulate the formation of red blood cells by the bone marrow)3. The waste products leave the kidneys as urine, and are conveyed through the ureter to the urinary bladder in the pelvis2. The urine leaves the body via the urethra1. The kidneys, which are retroperitoneal and lie on the posterior abdominal wall, could be seen after we removed the parietal peritoneum of the posterior abdominal wall of the cadaver. The kidneys are reddish-brown in colour and ovoid-shaped2. They are approximately 10cm in length, 5cm in width, 2.5cm in thickness2 and weight between 115 to 170g in the adult human3. They lie on either side of the vertebral column at the level of T12 through L32. The right kidney is slightly inferior to the left kidney due to the large size of the right lobe of the liver2. Each kidney moves approximately 3cm downwards on inspiration and upwards on expiration2.

1. Inferior vena cava 4. Left gastric artery
2. Inferior vena cava 5. Superior mesenteric artery
3. Abdominal aorta 6. Inferior mesenteric artery

The relations of the right kidney:
1. Anteriorly1 — suprarenal gland, liver, second part of duodenum, right colic flexure
2. Posteriorly1 — diaphragm, 12th rib, costodiaphragmatic recess of the pleura, psoas muscle, quadratus lumborum muscle, transversus abdominis muscle
The relations of the left kidney:
1. Anteriorly1 — suprarenal gland, spleen, stomach, pancreas, left colic flexure, coils of jejunum
2. Posteriorly1 — diaphragm, costodiaphragmatic recess of the pleura, 11th and 12th rib, psoas muscle, quadratus lumborum muscle, transversus abdominis muscle

7. Right suprarenal gland 10. Left kidney
8. Right kidney 11. Left ovarian vein
9. Right ureter  

After we removed the left kidney from the cadaver, we sliced it into half to reveal the its internal structure. The kidney is subdivided into 5 segments (superior, anterosuperior, anteroinferior, inferior and posterior) according to its arterial supply1

1. Superior segment of left kidney 9. Left renal vein
2. Posterior segment of left kidney 10. Left renal hilum
3. Inferior segment of left kidney 11. Left ureter
4. Left ureter 12. Superior segment of left kidney
5. Left renal vein 13. Anterosuperior segment of left kidney
6. Left renal artery 14. Anteroinferior segment of left kidney
7. Renal pelvis 15. Inferior segment of left kidney
8. Renal hilum  

The segmental arteries divide into two or three interlobar arteries before entering the renal substance2. The interlobar artery that runs radially toward the cortex divides into arcuate arteries at the corticomedullary junction2,4. The arcuate artery that runs circumferentially along the corticomedullary junction divides into several interlobular arteries that ascend the cortex4. The afferent glomerular arterioles arise as branches of the interlobular arteries2. Afferent glomerular arterioles arise from the interlobular arteries to supply the glomerular capillary bed, which drains into the efferent glomerular arterioles. These arterioles drain into a peritubular capillary network within the renal cortex and into increasingly large and more proximal branches of renal veins. Several smaller renal veins that drain the kidney unite in different ways to form a larger renal vein2. The renal veins are anterior to the renal arteries2. The left renal vein is longer, and it passes anterior to the aorta.

1. Renal vein 4. Renal medulla (Renal pyramid)
2. Renal artery 5. Renal column
3. Renal cortex 6. Minor calyx

The division of the renal artery could not be clearly seen on the photographs and the fat surrounding the renal capsule had been removed. Nevertheless, some other major structures of the kidneys could be discerned. The diagram provided shows a much clearer picture on the kidney’s internal structure.