Urinalysis - The Carter Center

1.1 Anatomy of the Kidney
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The kidneys are two bean shaped organs located under the lowermost
part of the ribs in the posterior abdominal cavity. Each human kidney
weighs 150 gms and measures 1x2x3 inches (thickness, width, and
length). A coronal section of the kidney shows an outer reddish granular
layer called renal medulla. In the renal medulla the triangular and wedge
shaped structure is called renal pyramids. The tips of the pyramids
found on the renal papillae at which urine is drained into cavities is called
Renal Calyces. Renal Calyces drain urine into renal pelvis, then to
ureter, which in turn drain to bladder and then through the urethra is
voided out.
The gross anatomy of the kidney is shown in Figure 1.2.
The functional unit of the kidney is the nephron (Figure 1. 3). There are
approximately one million nephrons in each kidney. Each nephron
consists of a glomerulus, which is essentially filtering system, and a
tubule through which the filtered liquid passes. Each glomerulus consists
of a network of capillaries surrounded by a membrane called
Bowman's ( Glomerular ) Capsule, which continues on to form Bowman's
Space and the beginning of the renal tubule. The afferent arteriole,
which carries blood from the renal artery into the glomerulus divides to
form a capillary network. These capillaries re-unite to form the efferent
arteriole, through which blood leaves the glomerulus. The blood
vessels thus follow the course of the tubule, forming a surrounding
capillary network. The tubular portion of each nephron has several
distinct structural and functional segments. The uppermost portion,
which continuous with the glomerulus, is the proximal convoluted tubule,
followed by the thin walled segment and the distal convoluted tubule
respectively. The descending limb of the proximal tubule (the thin-walled
segment) and the distal tubule form a loop known as the Loop of Henle.
The distal convoluted tubules from several nephrons drain into a