CHAPTER 17
Endocrine System
329
Pars
Pars
distalis
distalis
Pars
distalis
Pars
Pars
Intermedia
Intermedia
Pars
Intermedia
Pars
Pars
nervosa
nervosa
Pars
nervosa
Capsule
Capsule
Capsule
C
Hypothalamus
Hypothalamus
Hypothalamus
Optic
Optic
chiasm
chiasm
Optic
chiasm
Optic chiasm
Pituitary
Pituitary
gland
gland
Pituitary
gland
Infundibular
stalk
Pituitary
Pituitary
gland
gland
Pituitary
gland
Pineal
Pineal
gland
gland
Pineal
gland
A
Figure 17-3A.
Overview of the pituitary gland.
The
pituitary gland
is a small, bean-shaped gland,
about 1 cm in diameter, located inferior to the
hypothal-
amus
and separated from it by the
diaphragma sellae
through which the
infundibular stalk (infundibulum)
passes. The pituitary gland lies within the sella turcica.
Various important surrounding structures are visible
in the photograph and
inset
. The pituitary gland is
located inferior, and slightly caudal, to the
optic chi-
asm
; this is a particularly important anatomical rela-
tionship that is applicable to clinical medicine.
A
pituitary tumor
, as it enlarges, may impinge on
the crossing F
bers within the optic chiasm, causing
visual F
eld deF
cits. This most commonly results in
bitemporal hemianopia
, a loss of the temporal visual
F elds of both eyes. Other visual F eld deF
cits can also
result from pituitary tumors.
Mammillary
body
Pars
nervosa
Pars
intermedia
Infundibular
stalk
Arcuate
nucleus
Optic
chiasm
Median
eminence
Basophils
Acidophils
Pars
tuberalis
Pars
distalis
Supraoptic
nucleus
Anterior lobe
Posterior lobe
Paraventricular
nucleus
Hypothalamus
Infundibular
stalk
Hypothalamus
Hypothalamus
Hypothalamus
Pars
tuberalis
Pars
nervosa
Pars
distalis
Pars
tuberalis
B
Figure 17-3B.
Pituitary gland.
Mallory trichrome and H&E,
3
10
The
pituitary gland
is closely associated with the hypothalamus; it can be divided into two regions based on embryonic origins: the
adenohypophysis (anterior pituitary gland)
and the
neurohypophysis (posterior pituitary gland)
. The adenohypophysis arises from
the
ectoderm
of the
Rathke pouch
(roof of the developing oral cavity). It includes the
pars distalis
,
pars tuberalis
, and
pars intermedia
.
The neurohypophysis is differentiated from the neural ectoderm of the inferior surface of the developing diencephalon. It includes the
median eminence
,
infundibular stalk
, and
pars nervosa
and contains axons whose cell bodies are located in the hypothalamus.
Figure 17-3C.
Pituitary gland.
Mallory trichrome and H&E,
3
31
The
adenohypophysis (anterior pituitary gland)
with its connective tissue
capsule is shown on the
left
of the microphotograph. It stains red-blue
because it contains
chromophils
(acidophils and basophils) and
chromo-
phobes
. The pars nervosa of the
neurohypophysis (posterior pituitary
gland)
is nervous tissue; it is shown on the
right
. It contains
axons
,
pituicytes
, and
capillaries
. It stains much lighter than the adenohypo-
physis. The cell bodies of these axons are located in the
supraoptic
and
paraventricular nuclei
of the
hypothalamus
. These neurons have long
axons that extend from the hypothalamus into the neurohypophysis of
the pituitary gland. The axons contain neurosecretory granules consist-
ing of two types of hormones:
oxytocin
(supraoptic and paraventricular
nuclei) and
ADH
(supraoptic nucleus). Enlarged axon terminal endings
are known as
Herring bodies
(±ig. 17-6A,B).
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