330
Chapter 11
SECTION B
The Hypothalamus and Pituitary Gland
Control Systems Involving the
Hypothalamus and Pituitary
The
pituitary gland,
or hypophysis, lies in a pocket (called
the sella turcica) of the sphenoid bone at the base of the brain
(
Figure 11–13
), just below the
hypothalamus.
The pituitary is
connected to the hypothalamus by the
infundibulum,
a stalk
Hypothalamus
Infundibulum
Arterial blood
Optic chiasm
Hypothalamo-pituitary p
Anterior pituitary
Endocrine cells
To venous circulation
Sella turcica
Supraoptic
nuclei
(to posterior
Paraventricular
nuclei
(to posterior
pituitary)
Nuclei sending
axons to median
eminence
To venous circulation
Sphenoid bone
Arterial blood supply
eminence
(b)
Figure 11–13
(a) Relation of the pituitary gland to the brain and hypothalamus. (b) Neural and vascular connections between the hypothalamus and
pituitary. Hypothalamic neurons from the paraventricular and supraoptic nuclei run down the infundibulum to end in the posterior pituitary,
whereas others (shown for simplicity as a single nucleus, but in reality several nuclei, including some cells from the paraventricular nuclei) end
in the median eminence. Almost the entire blood supply to the anterior pituitary comes via the hypothalamo-pituitary portal vessels, which
originate in the median eminence. (The short portal vessels, which originate in the posterior pituitary, carry only a small fraction of the blood
leaving the posterior pituitary and supply only a small fraction of the blood received by the anterior pituitary.)
Figure 11–13
physiological
inquiry
Why does it take only minute quantities of hypophysiotropic hormones to regulate anterior pituitary gland hormone secretion?
Answer can be found at end of chapter.
containing nerve fi bers and small blood vessels. In human beings,
the pituitary gland is composed of two adjacent lobes—the
anterior pituitary
(toward the front of the head; also called the
adenohypophysis) and the
posterior pituitary
(toward the back
of the head; also called the neurohypophysis). The anterior pitu-
itary arises embryologically from an invagination of the pharynx
called Rathke’s pouch, whereas the posterior pituitary is actually
an extension of the neural components of the hypothalamus. In
many mammalian species a well-developed intermediate lobe is
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