An outer renal cortex and an inner renal medulla comprise the structure of the kidney. The inner renal medulla houses the renal pyramids. Urine, which is the body’s form of liquid waste product, is created as a the blood is filtered at the nephrons and then collects at the calyces as well as the renal pelvis before exiting the body from the kidney down through the ureter. The kidneys are the color of a reddish brown bean and are situated along the abdominal cavity’s posterior wall. Positionally speaking, the kidneys are located even with the third lumbar and twelfth thoracic vertebrates.


The liver’s appearance on the right side of the body creates an uneven positioning of the kidneys. The right kidney is generally about 1.5 to 2.0 centimeters lower than the left kidney. When an organ is retroperitoneal, this means it is located behind the parietal peritoneum. This applies to the kidneys.

Kidneys resemble the shape of a lima bean, with a convex lateral border and a highly concave medial edge. In an average human adult, the kidneys measures approximately 4 inches in length and between 2 and 3 inches in width with about a 1 inch thickness.

Running along the medial edge of the kidney, there lays a depression known as the hilum. The hilum is the entrance provided for the renal artery. It also provides and exit for the renal vein and the ureters. The hilum also provides a specific site for lymph drainage and the nerves to enter and innervate the kidney.


Image: Kidney

An adrenal gland is found along the superior border of each individual kidney. The individual kidneys are then entrenched in a pouch with a fatty fibrous consistency and three discernable layers. The innermost layer is the renal capsule, also determined as the fibrous capsule. It is a particularly strong and transparent fibrous protective attachment that can be found on the surface of the kidney. Its main function is to prevent illness, disease, and various traumas from affecting the kidney.

The following middle layer is a thicker and firmer layer of a fatty tissue mass that in known as the renal adipose capsule. The renal fascia is the outer supportive layer created from irregular connective tissue which is the dense layer of the entire encasement. Its primary responsibility is to adjoin firmly the kidney to the wall of the abdomen as well as the peritoneum.


Adequately demonstrating the highly distinctive regions of the kidney, a coronal section of the kidney reveals two identifiable regions as well as the major cavity. The numerous capillaries within the outer renal cortex create a reddish-brown hue. The capillaries also add to the granular appearance of the renal cortex. The renal medulla is deeper and darker, with a striped look that comes from the microscopic tubules and blood vessels. Anywhere from 8 to 15 conical renal pyramids contribute to creation of the renal medulla. The renal columns are then created by the sections of the renal cortex which protrude down between the renal pyramids. The renal pyramids are equipped with apexes which are known as the renal papillae, which resemble nipples and protrude downward to the inner cavity of the kidney.

The cavity of the kidney is designed for the collection and transportation of the liquid body wastes. The cavity fills with fluid and then transports the fluid via the ureters. The cavity itself is segregated into various sections. A little depression within the cavity accepts the projections of the papillae of the renal pyramids. This depression is known as the minor calyx. The major calyx is formed by the unification of numerous minor calyx depressions. There are several major calyxes, and they each form the funnel that creates the renal pelvis by joining together.

The creation of urine is derived from a functional unit within the kidney known as the nephron. Nephrons are encompassed by tiny blood vessels, and within each individual kidney, there are literally over a million nephrons. The capillary filtration process creates the fluid that enters the nephron, and the natural transportation process creates a modification in the fluid’s structure. This process creates the natural fluid known commonly as urine.
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