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The renal cortex is the outer portion of the kidney between the renal capsule and the renal medulla. [1] In the adult, it forms a continuous smooth outer zone with a number of projections ( cortical columns ) that extend down between the pyramids .
The functional substance, or parenchyma, of the human kidney is divided into two major structures: the outer renal cortex and the inner renal medulla. Grossly, these structures take the shape of eight to 18 cone-shaped renal lobes , each containing renal cortex surrounding a portion of medulla called a renal pyramid . [ 18 ]
The human urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites , and regulate blood pH .
The cortex itself is heavily permeated with arteries, while there are no arteries in the medulla. [17] The venous flow of blood runs back parallel to the arteries. [109] In some species, there are veins isolated from the arteries under the capsule in the cortex, which in humans are called stellate veins. These veins flow into the interlobular ...
Turtles and some lizards have urinary bladder [50] that opens into the cloaca [54] but snakes and crocodiles do not have it. [50] Compared with the metanephros of birds and mammals, the metanephros of reptiles is simpler in structure. [21] Unlike mammals, the kidneys of reptiles do not have a clear distinction between cortex and medulla. [43]
The renal papilla is the location where the renal pyramids in the medulla empty urine into the minor calyx in the kidney. Histologically it is marked by medullary collecting ducts converging to form a papillary duct to channel the fluid.
The collecting duct system begins in the renal cortex and extends deep into the medulla. As the urine travels down the collecting duct system, it passes by the medullary interstitium which has a high sodium concentration as a result of the loop of Henle's countercurrent multiplier system. [1]: 67
The renal lobe is a portion of a kidney consisting of a renal pyramid and the renal cortex above it. [1] In humans, on average there are 7 to 18 renal lobes. [medical citation needed] It is visible without a microscope, though it is easier to see in humans than in other animals.