BIOL1019 Chap.13 Reproductive Systems, Pregnancy and Development
Reproductive Systems, Pregnancy and Development
The reproductive chapter links endocrine control to the making of gametes and the course of a pregnancy. It compares spermatogenesis, which runs continuously from stem cells to four haploid spermatids, with oogenesis, which pauses in prophase I until puberty and in metaphase II until fertilisation.
It sets the ovarian and uterine cycles on one 28-day calendar, with the day 10 switch toward LH, the day 14 LH surge and ovulation, and the progesterone-driven luteal and secretory phases. The second half covers the fertilisation window, implantation, the hormones of pregnancy, maternal adaptations such as a rise in GFR, labour as positive feedback, and development from pre-embryo to foetus.
Reproduction is the final topic of Test 2 and closes the semester. The lecture concept checks ask for the steps of spermatogenesis and oogenesis, hypothalamic and pituitary control of the cycle, three pregnancy hormones and their functions, and a description of labour as positive feedback.
What this chapter covers
- 01
Male reproductive tract and accessory glands
- 02
Spermatogenesis, nurse cells and Leydig cells
- 03
Oogenesis and follicle development
- 04
Ovarian and uterine cycles
- 05
Fertilisation, implantation and the placenta
- 06
Hormones and maternal changes in pregnancy
- 07
Labour, birth and lactation
- 08
Foetal shunts and the first breath
Worked example · free
What the LH surge does on day 14
- +1From about day 7 the developing follicle secretes estrogen, which drives the proliferative phase of the endometrium.
- +1Around day 10 rising estrogen switches the pituitary toward LH, and a sudden estrogen rise gives brief positive feedback.
- +1The day 14 LH surge completes meiosis I and triggers ovulation of the secondary oocyte.
- +1LH then converts the ruptured follicle into the corpus luteum, whose progesterone dominates days 15 to 28.
Key terms
- Leydig cell
- A testicular interstitial cell that makes testosterone in response to LH.
- Graafian follicle
- The mature ovarian follicle that releases a secondary oocyte at ovulation.
- Human chorionic gonadotropin
- A trophoblast hormone that keeps the corpus luteum secreting and prevents menstruation.
- Gastrulation
- The formation of ectoderm, mesoderm and endoderm, at about day 12 of development.
- Ductus arteriosus
- A foetal vessel that carries blood from the pulmonary trunk to the aorta and closes at birth.
- Inhibin
- A hormone from testicular nurse cells and ovarian follicles that lowers FSH secretion by negative feedback.
Reproductive Systems, Pregnancy and Development FAQ
How long are gametes viable around ovulation?
The course gives the oocyte 12 to 48 hours and sperm 24 to 72 hours of viability. Fertilisation is therefore likely only when intercourse falls within roughly 3 days before ovulation or 24 hours after it. If fertilisation occurs, implantation follows 6 to 7 days after ovulation.
What changes in the mother during pregnancy?
Maternal blood volume rises by 25 to 40% and cardiac output increases while peripheral resistance and blood pressure fall. Ventilation increases. The kidneys enlarge, renal blood flow rises and GFR increases by about 50%, with an upregulated renin-angiotensin system retaining sodium. Nutritional needs rise by 10 to 30%.
Why is labour an example of positive feedback?
Near term estrogen peaks and makes the myometrium more irritable. Oxytocin and prostaglandins cause contractions, and the stress of contraction activates the hypothalamus to release more oxytocin, so each contraction strengthens the next. The loop amplifies rather than reverses the change and stops only with delivery, which is the defining feature of positive feedback.
What do Leydig cells and nurse cells do in the testis?
Leydig cells, between the seminiferous tubules, make testosterone from cholesterol in response to LH. Nurse cells inside the tubules maintain the blood-testis barrier, support mitosis, meiosis and spermiogenesis under FSH and testosterone, and secrete inhibin, which lowers FSH by negative feedback, along with androgen-binding protein.
Exam move
Draw the 28-day calendar with the ovarian band above the uterine band and mark the day 10 switch, the day 14 surge and the progesterone phase. Make a side-by-side table of spermatogenesis and oogenesis with divisions, pauses and controlling hormones. Then learn the pregnancy hormones with two functions each, and practise describing labour as a feedback loop in four sentences.
Finish by placing the development milestones on a timeline, fertilisation, morula, blastocyst, implantation, gastrulation and week 8, with the day or week the course gives for each.
Working through Reproductive Systems, Pregnancy and Development in BIOL1019? Sia is AskSia’s AI Anatomy & Physiology tutor — ask any BIOL1019 Reproductive Systems, Pregnancy and Development question and get a clear, step-by-step explanation grounded in how BIOL1019 is taught and assessed. Read this chapter free, then take your hardest questions to Sia.