328
UNIT 3
Organ Systems
Pituitary Gland
Kidney
Water absorption
(collecting tubules)
Uterus
Contraction
(smooth muscle of
myometrium)
Mammary gland
Milk secretion
(secretory cells)
Muscle
Growth
(skeletal muscle)
Adipose tissue
Utilization for energy
(adipose cells)
Mammary gland
Contraction
(myoepithelial cells)
Adrenal cortex
Corticosteroids
secretion
(salt, sugar, sex)
Thyroid
T and T secretion
(metabolic activity)
34
Ovary
Progesterone
secretion
(ovulation)
Liver
Secretion of IGF-1
(somatomedins)
(hepatocytes)
Ovary
Estrogen
secretion
(follicle growth)
Testis
Secretion of testosterone
by Leydig cells
(sex characteristics)
Testis
Secretion by Sertoli cells
(spermatogenesis)
ACTH (+)
(corticotrophs)
TSH (+)
(thyrotrophs)
Oxytocin (+)
(from supraoptic and
paraventricular nuclei)
Prolactin (+)
(mammotrophs)
Growth hormone/
somatotrophin (+)
(somatotrophs)
ADH/vasopressin (+)
(from supraoptic nucleus)
LH (+)
(gonadotrophs)
FSH (+)
(gonadotrophs)
Bone
Growth
(epiphyseal plate)
Hypothalamus
(–)
(–)
Releasing hormones
Figure 17-2.
Overview of hormone regulation by the pituitary gland.
The hormones released by the
basophils
in the
adenohypophysis
of the
pituitary gland
include
ACTH
,
TSH
,
FSH
, and
LH
.
ACTH
is syn-
thesized by
corticotrophs
, which are stimulated by CRH from the hypothalamus. ACTH is synthesized by
thyrotrophs
, which stimulates
the adrenal cortex to produce corticosteroids (glucocorticoids, androgens) and indirectly infl uences aldosterone.
TSH
is also synthesized
by
thyrotrophs
; it stimulates production of T
3
and T
4
by the thyroid.
FSH
and
LH
are secreted by
gonadotrophs
; these hormones promote
secondary sex characteristics and stimulate the development of ovarian follicles (ovary) and spermatogonia (testis). The hormones released
by
acidophils
include prolactin and growth hormone. Prolactin is secreted by
mammotrophs (lactotrophs)
and stimulates the mammary
glands to produce milk. The growth hormone (somatotropin) is secreted by
somatotrophs
; it stimulates the liver to produce
IGF-1
, also
known as
somatomedins
, which promotes protein deposition, cell reproduction, and cartilage and bone growth and enhances fat utiliza-
tion for energy by increasing fatty acids in the bloodstream. The hormones released by the neurohypophysis include
ADH
(or
vasopressin
)
and
oxytocin
, which are produced by neurons whose cell bodies lie in the hypothalamus.
ADH
promotes water absorption by collecting
tubules and ducts.
Oxytocin
stimulates contraction of smooth muscle F bers in the myometrium of the uterus.
Pituitary Gland
I.
Adenohypophysis (anterior pituitary gland)
A. Pars distalis
1. Chromophobes
2. Chromophils
a.
Acidophils
: Somatotrophs (secrete growth hormone),
mammotrophs/lactotrophs (secrete prolactin)
b.
Basophils
: Corticotrophs (secrete ACTH), thyrotrophs
(secrete TSH), gonadotrophs (secrete ±SH and LH)
B.
Pars
/
tuberalis
: Gonadotrophs (secrete ±SH and LH)
C. Pars intermedia
1. Rathke cysts (colloid-containing cysts)
2. Basophilic cells/melanotrophs (secrete MSH)
II.
Neurohypophysis (posterior pituitary gland)
A. Neural (infundibular) stalk
B. Median eminence
C. Par
s
nervosa
1. Herring bodies (contain neurosecretory granules)
2.
Neurohypophyseal hormones: ADH (secreted by neu-
rons whose cell bodies are in the supraoptic nucleus),
oxytocin
(secreted by neurons whose cell bodies are in
both supraoptic and paraventricular nuclei)
Abbreviations
ACTH: Adrenocorticotropic hormone
TSH: Thyroid-stimulating hormone
±SH: ±ollicle-stimulating hormone
LH: Luteinizing hormone
MSH: Melanocyte-stimulating hormone
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