Final answer:
The kidneys are retroperitoneal organs located on either side of the spine, protected by the ribs, with the right kidney being slightly lower and smaller than the left due to the liver's position.
Step-by-step explanation:
The kidneys are located in the posterior part of the abdomen, flanking the spine in a region known as the retroperitoneal space. These bean-shaped organs are situated below the diaphragm, with the left kidney typically positioned slightly higher and more medial owing to the presence of the liver which displaces the right kidney downwards.
The external anatomy of the kidneys reveals that they lie opposite the T12 to L3 vertebrae and are protected by the eleventh and twelfth ribs. Each kidney possesses a fibrous capsule, a layer of adipose tissue, and is ensconced in renal fascia, which together contribute to their protection and structural integrity. Moreover, the right kidney is not only positioned lower but is also slightly smaller when compared to the left kidney due to the liver's displacement effect. The kidneys are integral to the urinary system, filtering blood, and maintaining homeostasis by regulating fluid and electrolyte balance.