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ENDOCRINE PHYSIOLOGY

Posterior Pituilary: Oxytocin

Oxyto<in pickcd up by capillaries of posterior lobe

Oxytocin migrates along /' nerve li fiberS J

^ Psychogenic stimuli

Paraventricular nucleus of hypothalamus (sitc of

Afferent impulses

Prolactin stimulates milk produclion in endocrinologicall>’ prepared breast

Oxytocin causes milk expulsion

Oxytocin ca u sos uterine contraction

Afferent impulses from cervical dilation or vaginal stimulation

Figurę 8.5 Posterior Pituitary Function (Oxytocin)

Oxytocin is released from thc posterior pituitary in rosponse to vagi-nal stimulation and suckling. In resf>onse to vaginal stimulation, as occurs during sexual intercourse. óxytocin is released and causes uterine contraction. Tbis may facilitate sperm transport through the uterus and uterine tubes. Oxytodn also łacilitates childbirth by inereasing uterine contractions during labor. During nursing. stimulalion of the nipplc by the suckling infant causes oxytocin release. which then acls on the myoepithelial cdls surrounding the mammarv gland alveoli and ducts causing expression of milk. Neural pathways activated during suckiing also stimulate the secretion of prolactin.

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