Which of the following hormones is responsible for both the milk ejection reflex and the foetal ejection reflex ?

Oxytocin is the hormone that plays a crucial role in both the milk ejection refl ex and the foetal ejection refl ex.

Oxytocin is responsible for triggering the milk ejection reflex. When a baby suckles at the breast, sensory nerve endings in the nipple are stimulated, sending signals to the hypothalamus in the brain. The hypothalamus, in response, secretes oxytocin, which is released from the posterior pituitary gland into the bloodstream.
Oxytocin acts on the myoepithelial cells surrounding the milk-producing alveoli in the breast, causing them to contract. This contraction helps push the milk through the ducts, facilitating its release and allowing the baby to feed.

During childbirth, oxytocin plays a vital role in the foetal ejection refl ex. As labor progresses, oxytocin is released in increasing amounts from the hypothalamus and it stimulates uterine muscles to contract rhythmically. These contractions help to push the baby downward through the birth canal and facilitate the expulsion of the foetus during delivery.

(1) Oestrogen promotes development and maintenance of female secondary sex characteristics.
Though oestrogen is not directly responsible for foetal ejection refl ex, it aids in parturition by promoting the
synthesis of prostaglandins (which intensify contractions of uterine smooth muscles), increasing sensitivity
of uterine muscles to oxytocin and contributing to the softening and dilation of uterine cervix. Oestrogen is not directly responsible for the milk ejection refl ex. 

(2) Prolactin stimulates milk production (lactation) in the mammary glands. It is not directly responsible for the milk ejection refl ex or the foetal ejection reflex.

(4) Relaxin is primarily produced by the ovaries and placenta during pregnancy. It helps to relax the ligaments and prepares the body for childbirth by allowing the pelvic bones to widen. Relaxin is not directly involved in the
milk ejection reflex or the foetal ejection reflex.