Alguno no tenía claro esta tarde qué es lo que hace la Hipófisis:
Pituitary Gland (Hypophysis)
Neurohypophysis (Posterior Lobe of the
Pituitary Gland)
The neurohypophysis consists of a
meshwork of glia cells with numerous
capillaries. It does not itself secrete
hormones but is solely the storage
and releasing organ for hormones formed
in the hypothalamus, antidiuretic
hormone (vasopressin) and oxytocin.
These reach the posterior
pituitary through nervous pathways
(axons)—a process called neurosecretion—
and are then released into the
bloodstream. Oxytocin contracts
smooth muscles (e. g., it promotes uterine
contractions during
labor), while vasopressin promotes the
reabsorption of water in the collecting
tubules of the kidney and so raises the
blood pressure (increase in
blood volume).
Adenohypophysis (Anterior Lobe of the
Pituitary Gland)
The anterior lobe consists of an
irregular collection of glandular cells in
an extensive capillary bed. Release of
anterior pituitary hormones is promoted
(liberins) or inhibited (statins) by the
action of hypothalamic releasing
hormones, which reach the anterior lobe
through the bloodstream.
Some anterior pituitary hormones are
nonglandotropic or effector
hormones, i.e., they act directly on
their target organs, rather than on a
peripheral endocrine gland serving as a
relay. For example, growth hor-
mone,
also called somatotropin (STH), stimulates bodily
growth, while
prolactin (PRL) stimulates cell division and secretion of milk by the
mammary glands in late pregnancy and
during the breastfeeding period.
The remaining anterior pituitary hormones
stimulate subordinated
peripheral endocrine glands to grow as
well as secrete and release their
hormones. These hormones may be divided
into gonadotropins, which
act on the gonads, and nongonadotropic hormones, which
influence the
activity of the adrenal and thyroid
glands, for example.
The gonadotropins
include follicle-stimulating hormone (FSH,
follitropin)
and luteinizing hormone (LH, lutropin). Both act on the gonads of
men
as well as women. FSH stimulates the maturation
of the follicle in
the ovary and promotes spermatogenesis
(development of sperm) in
men. LH acts on the interstitial cells of
the ovary and the testes, initiating
ovulation in women and enhancing
testosterone secretion in men.
The nongonadotropic
hormones include corticotropin or adrenocorticotropic
hormone (ACTH) and thyrotropin or thyroid-stimulating hormone
(TSH,
thyrotropin). Whereas ACTH acts to stimulate the adrenal cortex,
TSH stimulates the secretion of hormones
by the thyroid gland.
