Question

In human adult females, oxytocin
A. Stimulation pituitary to secrete vasopressin
B. Causes strong uterine contractions during parturition
C. Is secreted by anterior pituitary
D. Stimulation growth of pituitary gland

Answer 1

Oxytocin is a hormone secreted from the posterior lobe of the pituitary gland. It is known as a birth hormone and also milk ejaculatory hormone. This hormone is secreted in both sexes but its function is documented only in females.

Complete answer:
Pituitary gland (master gland) is divided into two anterior and posterior lobes. The hormones secreted from anterior lobe are - Growth hormone, prolactin, thyroid stimulating hormone, gonadotropin hormone, ACTH and MSH whereas hormones like Vasopressin (ADH) and oxytocin is secreted from the posterior lobe of the pituitary gland.

oxytocin or oxytocin hormone has a molecular weight of 1025 and made up of 8 amino acids. It is known as a birth hormone because it stimulates uterine contractions during childbirth. And also milk ejaculatory hormone because it stimulates ejection of milk through contraction of myoepithelial cells found in the alveolar secretory epithelium. The normal function of oxytocin is vasodilation and hence reduction in blood pressure.

Oxytocin has the following effects-
Oxytocin causes contraction of the pregnant uterus towards the end of gestation period.
Oxytocin initiates labour pains leading to parturition. As a feedback mechanism, the uterine cervix in a pregnant woman elicits nervous signals which, in turn, stimulate increased secretion of oxytocin. It also promotes milk-ejection from the mammary glands during the period of active lactation after childbirth. It is also responsible for the uterine contraction that occurs during the female orgasm.

So, oxytocin is secreted from the posterior lobe of the pituitary gland that plays major in uterine contractions during partition ( childbirth), it doesn't stimulates pituitary for Vasopressin secretion neither stimulus growth of the pituitary gland.

Hence, the correct answer is option (B).

Note: Oxytocin plays a very important role during the period of childbirth and after birth, even though sight, cry or sound of the baby can bring about secretion of this hormone in lactating mothers. It is stimulated by the pituitary gland that helps in the contraction of uterine muscles during birth also called parturition.