Human Reproduction

Humans are sexually reproducing and viviparous, and reproduction involves the formation of gametes, insemination, fertilisation, the development of the blastocyst, implantation, gestation and parturition. In this chapter you will study the structure of the male reproductive system, including the testes held in the scrotum at a temperature 2 to 2.5 degrees C below body temperature, the seminiferous tubules with Sertoli cells, the androgen-secreting Leydig cells, the duct system and the accessory glands. You will also study the female reproductive system: ovaries, oviducts with infundibulum, ampulla and isthmus, the three-layered uterus, and the mammary glands. The chapter explains spermatogenesis and oogenesis with their hormonal control by GnRH, LH and FSH, the structure of a sperm, and the phases of the 28-day menstrual cycle with ovulation around day 14. You will learn how fertilisation occurs at the ampullary-isthmic junction, how the zygote develops into a morula and then a blastocyst that implants in the endometrium, the role of the placenta and its hormones, embryonic development month by month, and the hormonal control of parturition and lactation.

Detailed Worksheet: Human Reproduction Section A - Definitions (10 marks) 1. List the primary sex organs and the accessory glands of the human male reproductive system. (2 marks) 2. Define spermiogenesis and spermiation. (2 marks) 3. What is the Graafian follicle? What happens to it after ovulation? (2 marks) 4. Define implantation. Name the part of the blastocyst that gives rise to the embryo. (2 marks) 5. What is colostrum? Why is it important for a newborn baby? (2 marks) Section B - Calculations and Applications (15 marks) 6. Calculate the number of sperms formed from 50 primary spermatocytes and the number of ova formed from 50 primary oocytes. Also state the number of chromosomes in a spermatogonium, primary spermatocyte, secondary spermatocyte and spermatid in humans. (3 marks) 7. A human male ejaculates about 250 million sperms during coitus. For normal fertility, at least 60% must have normal shape and size, and at least 40% must show vigorous motility. Calculate the minimum number of sperms with normal shape and with vigorous motility. (3 marks) 8. A woman has a regular 28-day menstrual cycle, and her last menstruation began on 1 March. Calculate the expected day of ovulation and the date on which her next menstruation should begin if fertilisation does not occur. Name the hormone whose surge triggers ovulation. (3 marks) 9. At birth a female has about 2 million primary follicles in each ovary, and at puberty about 60,000 to 80,000 remain in each ovary. Calculate the minimum percentage of follicles lost from each ovary between birth and puberty. What is this degeneration called? (3 marks) 10. Arrange the following events in the correct sequence and state where each occurs: implantation, ovulation, cleavage, fertilisation, morula formation, blastocyst formation. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of a sectional view of a seminiferous tubule showing spermatogonia, primary and secondary spermatocytes, spermatids, sperms, Sertoli cells and interstitial (Leydig) cells. (4 marks) 12. Draw a labelled diagram of a human sperm showing the head, acrosome, nucleus, neck, middle piece with mitochondria and tail. (3 marks) 13. Draw a labelled diagram of a sectional view of the human ovary showing primary follicle, secondary follicle, tertiary follicle, Graafian follicle, ovum, corpus luteum and corpus albicans. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Draw graphs or describe the changes in the levels of LH, FSH, estrogen and progesterone during the menstrual cycle. Explain how these hormones control the follicular phase, ovulation and the luteal phase, and analyse what happens to the corpus luteum if fertilisation does occur. (5 marks) 15. Compare spermatogenesis and oogenesis on five bases: time of onset, site, number of functional gametes, the stage at which meiosis is completed and the role of hormones. Explain why oogenesis yields one ovum and polar bodies. (5 marks) 16. The placenta acts as an endocrine tissue. Name the hormones produced by the placenta and the ovary during pregnancy and explain their roles. Analyse the role of the foetal ejection reflex and oxytocin in parturition. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw all diagrams neatly in pencil and label every part.