OTHER HORMONES OF ANTERIOR PITUITARY
Thyroid-stimulating
Hormone (TSH)
TSH is necessary for the
growth and secretory activity of the thyroid gland. It has many actions on the
thyroid gland.
Adrenocorticotropic
Hormone (ACTH)
ACTH is necessary for the
structural integrity and the secretory activity of adrenal
cortex. It has other functions also.
Follicle-stimulating
Hormone (FSH)
Follicle-stimulating hormone
is a glycoprotein made up of one α-subunit and a
β-subunit. The α-subunit has 92 amino acids and
β-subunit has 118 amino acids. The half-life of FSH is about 3 to 4
hours.
Actions
of FSH
In males, FSH acts along
with testosterone and accelerates the process of spermeogenesis.
In females FSH:
1. Causes the development
of graafian follicle from primordial follicle
2.
Stimulates the theca cells of graafian follicle and causes
secretion of estrogen.
3. Promotes the aromatase
activity in granulosa cells, resulting in conversion of androgens into
estrogen.
Luteinizing Hormone
(LH)
LH is a
glycoprotein made up of one α-subunit and one β-subunit. The α-subunit has 92
amino acids and
β-subunit
has 141 amino acids. The half-life of LH is about 60 minutes.
Actions
of LH
In males, LH is known as interstitial
cell-stimulating hormone (ICSH) because it stimulates the interstitial
cells of Leydig in testes.
In females, LH:
1. Causes
maturation of vesicular follicle into graafian follicle along with
follicle-stimulating hormone
2. Induces synthesis of
androgens from theca cells of growing follicle
3. Is responsible for ovulation
4. Is necessary for the
formation of corpus luteum
5. Activates the secretory
functions of corpus luteum.
Prolactin
Prolactin is a single
chain polypeptide with 199 amino acids. Its half-life is about 20 minutes.
Prolactin is
necessary
for the final preparation of mammary glands for the production and secretion
of milk.
Prolactin acts directly on
the epithelial cells of mammary glands and causes localized alveolar hyperplasia.
β-lipotropin
β-lipotropin
is a polypeptide hormone with 31 amino acids. It mobilizes fat from
adipose tissue and promotes lipolysis.
It also forms the precursor of endorphins. This hormone
acts through the adenyl cyclase
POSTERIOR PITUITARY OR NEUROHYPOPHYSIS
PARTS
Posterior pituitary
consists of three parts:
1. Pars nervosa or infundibular
process
2. Neural stalk or
infundibular stem
3. Median eminence.
Pars tuberalis of anterior
pituitary and the neural stalk of posterior pituitary together form the hypophyseal
stalk.
HISTOLOGY
Posterior pituitary is made
up of neural type of cells called pituicytes and
unmyelinated nerve fibers.
Pituicytes
Pituicytes are the
fusiform cells derived from glial cells. These cells have several processes and
brown pigment granules. Pituicytes act as supporting cells and do not secrete
any hormone.
Unmyelinated Nerve
Fibers
Unmyelinated
nerve fibers come from supraoptic and paraventricular nuclei of the
hypothalamus through the pituitary stalk.
Other Structures
Posterior pituitary also
has numerous blood vessels, hyaline bodies, neuroglial cells and mast cells.
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