Figure 203

Development of the pituitary gland. This diagram shows sequential stages (a to c) in the development of the pituitary gland.

Blood Supply

Knowledge of the unusual blood supply of the pituitary gland is important to understanding its functions. The pituitary blood supply is derived from two sets of vessels (Fig. 20.4):

• Superior hypophyseal arteries supply the pars tuberalis, median eminence, and infundibular stem.

These vessels arise from the internal carotid arteries and posterior communicating artery of the circle of Willis.

• Inferior hypophyseal arteries primarily supply the pars nervosa. These vessels arise solely from the internal carotid arteries. An important functional observation is that most of the anterior lobe of the pituitary gland has no direct arterial supply.

capillaries of the median eminence and infundibulum hypophyseal veins capillaries of the median eminence and infundibulum hypophyseal veins

artery capillaries of the hypophyseal portal system in the pars distalis

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