The Pituitary Gland and
Hypothalamus Control Many
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.
release hormones into the
blood supplying the anterior pituitary.
Path of releasing and
Capillaries of anterior pituitary
Hypothalamic neurosecretory cells
extend into the posterior pituitary where
they release hormones directly into the blood.
Capillaries of ‘
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?
stalk that connects
the pituitary to the
Capillaries of posterior'
------ Sphenoid bone
in hypothalamus to
capillaries in anterior
258 CHAPTER 9
The Endocrine System