Kidneys and Urinary System - LO 2

2. Describe and identify the internal gross anatomy of the kidneys. 

The kidney is one of several organs in the body whose parenchyma is organized into a cortex surrounding a medulla.

The renal medulla is divided into discrete structures called renal (medullary) pyramids, conical masses of tissue that primarily contain the collecting ducts and nephron loops (of Henle). The apex of the renal pyramids, or renal papilla, points toward the center of the kidney. At the renal papilla, the collecting ducts conduct urine into minor calices, which coalesce to form major calices, and finally converge into a renal pelvis. The renal pelvis is the proximal, dilated portion of the ureter.  

The renal cortex is organized in two parts: arches and columns. The cortex is surrounded by a fibrous renal capsule. Between the renal capsule and the bases of the renal pyramids are the cortical arches. Surrounding and interleaving between sides of renal pyramids are the cortical columns.  

Renal Segments, Lobes, and Lobules

Each kidney consists of five surgically resectable renal segments, each supplied with blood from a separate segmental artery.  

The five renal segments are:

Another functional way of subdividing a kidney is by renal lobes. Renal lobes consist of a single renal pyramid, the cortical arch associated with that pyramid, and portions of the cortical columns (containing the nephrons) associated with that pyramid. Renal lobes may be subdivided into renal lobules. A renal lobule is a collection of cortex containing all the nephrons associated with a single medullary ray and a single collecting duct.