Q.(a) Explain the role of oxytocin and relaxin in parturition and lactation. OR

(a) Oxytocin triggers labour contractions and milk ejection; relaxin softens the birth canal. (b) Infertility has diverse structural, hormonal, infectious and lifestyle causes affecting either partner.

(a) As labour begins, stretching of the cervix and uterus sends signals to the hypothalamus, which triggers the posterior pituitary to release oxytocin; oxytocin acts on the myometrium (uterine muscle) to produce strong, rhythmic contractions that push the foetus through the birth canal, and because the contractions further stretch the cervix, more oxytocin is released -- a self-reinforcing positive-feedback loop that continues until delivery. After birth, oxytocin also plays a key role in the milk-ejection ('let-down') reflex during breastfeeding. Relaxin, secreted by the corpus luteum during pregnancy and later by the placenta, acts to relax and soften the ligaments of the pelvis and to soften and dilate the cervix as term approaches, widening the birth canal and easing the baby's passage; it works alongside oxytocin as one of the key hormonal preparations for parturition. (b) Infertility is diagnosed when a couple fails to achieve pregnancy after about one year of regular, unprotected intercourse. Causes can lie with either partner: in females, blocked or damaged fallopian tubes, uterine abnormalities (such as fibroids), hormonal disorders disrupting ovulation (e.g., polycystic ovarian syndrome), and endometriosis are common causes; in males, low sperm count, poor sperm motility, or abnormal sperm morphology can prevent successful fertilisation. Additional contributing factors for either partner include past …