Question 14 Marks
Read the following text carefully and answer the questions that follow:
After implantation, finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood. The chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between the developing embryo (foetus) and the maternal body.
i. Name the hormone crucial in parturition. Does the parturition signal originate from the mother or the fetus?(1)
ii. When and where do chorionic villi appear in humans? (1)
iii. Woman has conceived and implantation has occurred. Discuss the impact of progesterone and estrogen. (2)
OR
Fetal ejection reflex leads to parturition. Justify (2)
After implantation, finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood. The chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between the developing embryo (foetus) and the maternal body.
i. Name the hormone crucial in parturition. Does the parturition signal originate from the mother or the fetus?(1)
ii. When and where do chorionic villi appear in humans? (1)
iii. Woman has conceived and implantation has occurred. Discuss the impact of progesterone and estrogen. (2)
OR
Fetal ejection reflex leads to parturition. Justify (2)
Answer
View full question & answer→i. The hormone is Oxytocin. The signal originates from the placenta and fully developed fetus which initiate the foetal ejection reflex triggering the release of the hormone, oxytocin.
ii. After implantation, finger-like projections appear on the trophoblast called chorionic villi. They are surrounded by uterine tissue and maternal blood.
iii. Under the impact of progesterone and estrogen the size of the uterus and birth canal increases. Relaxation of pelvic ligament takes place. The placenta is developed between chorionic and uterine tissues.
OR
Fully developed foetus pushes down the birth canal, causing stretching of the cervix. This generates nerve impulse which stimulates the hypothalamus. It in turn causes the posterior pituitary to release oxytocin (birth hormone). Oxytocin causes the uterine muscles to contract more vigorously which leads to parturition.
ii. After implantation, finger-like projections appear on the trophoblast called chorionic villi. They are surrounded by uterine tissue and maternal blood.
iii. Under the impact of progesterone and estrogen the size of the uterus and birth canal increases. Relaxation of pelvic ligament takes place. The placenta is developed between chorionic and uterine tissues.
OR
Fully developed foetus pushes down the birth canal, causing stretching of the cervix. This generates nerve impulse which stimulates the hypothalamus. It in turn causes the posterior pituitary to release oxytocin (birth hormone). Oxytocin causes the uterine muscles to contract more vigorously which leads to parturition.