TUMORS OF THE PITUITARY GLAND
1
THE NORMAL PITUITARY GLAND
GROSS ANATOMY
The human pituitary gland, or hypophysis, is a small bean-shaped organ that lies in the sella turcica, or hypophysial fossa, a concave struc- ture in the superior aspect of the sphenoid bone at the base of the brain (figs. 1-1-1-3). The gland is well protected by the bony sella. Lateral to the sella are the cavernous sinuses which contain the internal carotid arteries and the oculomotor, trochlear, abducens, and first division of the trigeminal nerves; inferior and anterior is the sphenoid sinus; superior is the hypothalamus; and superoanteriorly is the optic chiasm. The bilaterally symmetric gland has two distinct parts, the adenohypophysis and the neurohypo- physis. As their names suggest, these two parts
are structurally and functionally different. The adenohypophysis is a red-brown epithelial gland; the neurohypophysis is a firm, grey neural struc- ture that is composed of axons of hypothalamic neurons and their supporting stroma.
The adult human pituitary gland measures approximately 13 mm transversely, 9 mm antero- posteriorly, and 6 mm vertically (figs. 1-4, 1-5). It weighs approximately 0.6 g. The female pituitary is somewhat larger than the male gland; this can be documented on magnetic resonance imaging where a difference of up to 2 mm in height is seen (8). The pituitary of pregnant and postpartum women is larger (8,9) and heavier (6); the increased size is due to marked prolactin cell hyperplasia during pregnancy and lactation, which may in- crease the weight to 1 g or more. Postlactational
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Figure 1.1 ANATOMY AND RELATIONS OF THE PITUITARY GLAND
Sagittal section through the midline shows the pituitary gland within the sella turcica, attached to the hypothala- mus by the pituitary stalk. The gland is situated immediately posterior to the sphenoid sinus. (Plate 4 from Section I. In: Netter FH, Forsham PH, eds. The CIBA collection of medical illustrations. Vol. 4, Endocrine system and selected metabolic diseases. CIBA, New York: Colorpress, 1965.)
