Page 695 - Atlas of Histology with Functional Correlations

CHAPTER 18 Urinary System

KIDNEY

The urinary system consists of two kidneys, two ureters that lead to a single
urinary bladder, and a single urethra that extends from the bladder through the
penis to the exterior. The kidneys are large, bean-shaped organs located
retroperitoneally adjacent to the posterior body wall. Superior to each kidney is
the adrenal gland embedded in renal fat and connective tissue. The concave,

medial border of the kidney is the hilum, which contains three structures: the
renal artery, renal vein, and the funnel-shaped renal pelvis that narrows to
become the ureter. Surrounding these structures is loose connective tissue and a

fat-filled space called the renal sinus.

Each kidney is covered by a dense connective tissue capsule. A sagittal
section through the kidney shows a darker outer cortex and a lighter inner
medulla, which consists of cone-shaped renal pyramids (Fig. 18.1). The base of
each pyramid faces the cortex and forms the corticomedullary boundary. The

round apex of each pyramid extends downward to the renal pelvis to form the
domelike renal papilla. A portion of the cortex also extends on each side of the
renal pyramids to form the renal columns.

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