The Pituitary Gland and
Hypothalamus Control Many
Endocrine Glands
The pituitary gland, which is about the size of a grape, is lo-
cated just beneath the brain (Figure 9.4). It consists of two
parts, the larger anterior pituitary lobe and the smaller
posterior pituitary lobe; the lobes of the pituitary are of-
ten referred to merely as the anterior pituitary and the pos-
terior pituitary. A third region of the pituitary gland, called
the pars intermedia (intermediate lobe), atrophies during
human fetal development and ceases to exist as a separate
lobe in adults; however, some of its cells migrate into adja-
cent parts of the anterior pituitary, where they persist.
The stru c tu re and b lo o d su pp ly o f th e p itu itary glan d • Figure 9.4
The hypothalamus controls the secretions of the pituitary gland into the blood. Some hypothalamic
neurosecretory cells make up the posterior pituitary, while others influence the anterior pituitary by
secreting releasing and inhibiting hormones into a common blood supply.
Hypothalamus
gland
Hypothalamus
Anterior
Hypothalamic neurosecretory
cells
release hormones into the
blood supplying the anterior pituitary.
Hypothalamic
neurosecretory
cell
Hypophyseal
portal veins
Path of releasing and
inhibiting hormones
Artery
Capillaries of anterior pituitary
Hypothalamic neurosecretory cells
extend into the posterior pituitary where
they release hormones directly into the blood.
Capillaries
of posterior
pituitary
Capillaries of ‘
hypothalamus
1. Which lobe of the pituitary gland does
not synthesize the hormones it releases?
2. Where are its hormones produced?
3. What is the role of the infundibulum?
Hypophyseal
fossa
Infundibulum
stalk that connects
the pituitary to the
hypothalamus.
Veins
Posterior
pituitary
Capillaries of posterior'
pituitary
Posterior
Artery
Anterior
pituitary
------ Sphenoid bone
Hypophyseal portal
veins
connect capillaries
in hypothalamus to
capillaries in anterior
pituitary.
Veins
258 CHAPTER 9
The Endocrine System
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