Second year – Group B
A presentation by:
Mrs. Shukrya Karim
Mrs. Daroon Osman
▶ Source of Secretion:
▶ Secreted mainly by paraventricular nucleus and partly
ransported from hypothalamusto posterior pituitary
through the nerve fibers of hypothalamo-hypophyseal
▶ In the posterior pituitary, the oxytocin is stored in the
nerve endings of hypothalamo-hypophyseal tract.
▶ When suitable stimuli reach the posterior pituitary from
hypothalamus, oxytocin is released into the blood.
▶ Oxytocin is secreted in both males and females.
▶ Causes ejection of milk from the mammary glands.
▶ Oxytocin causes contraction of the myoepithelial
cellsand flow of milk from alveoli of mammary
glands to the exterior through duct system and
▶ The process by which the milk is ejected from alveoli
of mammary glands iscalled milk ejection reflex or
▶ It isone of the neuro-endocrine reflexes.
⦁ On pregnant uterus:
▶ Throughout the period of pregnancy, oxytocin
secretion isinhibited by estrogen and progesterone.
▶ At the end of pregnancy, the secretion of these two
hormones decreases suddenly and the secretion of
▶ Oxytocin causes contraction of uterus and helps in the
expulsion of fetus.
▶ Itis also an example of neuro-endocrine reflex and
positive feedback mechanism
▶Action of oxytocin on non-pregnant uterus is to
facilitate the transport of sperms through female
genital tract up to the fallopian tube, by producing
the uterine contraction during sexual intercourse.
⯈Human prolactin is a single- chain polypeptide of
199 amino acids. It has a molecular weight of 23
⯈ Prolactinis synthetizedin and secretedfrom
specializedcellsof the anterior pituitary gland, the
⯈ Thepituitary gland(also calledasthe master
gland)is an endocrinegland about the size of apea
(weighing0.5 g)and locatedat the baseof the
brain(just belowthe hypothalamus).