OXYTOCIN

1. 1
Oxytocin
Introduction:
• This is a hormone of the posterior pituitary
gland. Oxytocin is a polypeptide, having 9
amino acids.
Synthesis:
• Oxytocin is synthesized mainly in the
paraventricular nuclei of the
hypothalamus.

2. 2
Transport:
• This hormone is transported from the
paraventricular nuclei of hypothalamus to the
nerve endings in the posterior pituitary gland by
carrier proteins called neurophysins.
Storage:
• It is stored in the posterior lobe of the pituitary
gland.
Mechanism of action:
• Action through intracellular mediator.

3. 3
Functions/Actions of Oxytocin:
1.Effects on the Uterus:
• Oxytocin that causes contraction of the
pregnant uterus. The hormone Oxytocin,
in accordance with its name, power fully
stimulates the pregnant uterus, especially
so towards the end of gestation.

4. 4
Effects on milk ejection:
• Oxytocin plays an important role in the
process of lactation. In lactation it causes
milk to be expressed from the alvoli into
the ducts so that baby can obtain it by
sucking.

5. 5
Mechanism:
• The suckling stimulus on the nipple of the
breast causes signals to be transmitted
through sensory nerves to the Oxytocin
neurons in the paraventricular and
supraoptic nuclei in the hypothalamus,
which causes release of oxytocin by the
posterior pituitary gland. The oxytocin is
then carried by the blood to the breast,

6. 6
• Where it causes contraction myoepithelial
cells that lie outside of and forma
latticework surrounding the alveoli of the
mammary glands. In less than a minute
after the beginning of suckling, milk begins
to flow. This mechanism is called milk
letdown or milk ejection.

7. 7
Effects on Blood Vessels:
• In large doses oxytocin causes vasodilation and
decreases blood pressure.
Effects on Pituitary Gland:
• It causes prolactin secretion.
• It inhibits ADH secretion.
Clinical indications for use of oxytocin:
• Inducing labor.
• Treatment of uterine haemorrhage.

8. 8
• Factors which increase oxytocin secretion:
• Sucking of nipples of lactating breasts by a baby.
• Crying of a baby.
• During labor.
• Factors which decrease oxytocin
secretion:
• Emotional stress.
• Activation of sympathetic neurons with release of
epinephrine and nor epinephrine.