Lesson 9 of 9 · 13 min
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Must-know facts
20 facts
- 01Scrotal temperature is about 2–2.5 °C below internal body temperature; this is needed for spermatogenesis.
- 02Each testis has about 250 testicular lobules, each with 1–3 seminiferous tubules.
- 03Sertoli cells nourish germ cells and respond to FSH; Leydig cells make androgens and respond to LH.
- 04Seminal plasma is rich in calcium, fructose and certain enzymes.
- 05Oviduct length is about 10–12 cm; its parts from ovary to uterus are infundibulum (with fimbriae), ampulla, isthmus.
- 06Uterine wall layers from outside: perimetrium, myometrium (contracts at delivery), endometrium (changes with the cycle).
- 07One primary spermatocyte → 2 secondary spermatocytes → 4 spermatids → 4 sperms; spermatogonia and primary spermatocytes are diploid (46), later stages haploid (23).
- 08Spermiogenesis = spermatid to sperm; spermiation = release of sperms from the seminiferous tubules.
- 09A normal ejaculate has 200–300 million sperms; for fertility, at least 40% must show vigorous motility and at least 60% must be of normal shape and size.
- 10Oogonia form only in foetal life; at puberty each ovary retains about 60,000–80,000 primary follicles.
- 11Primary oocytes stay arrested in prophase I; meiosis I is completed inside the tertiary follicle, giving the secondary oocyte and the first polar body.
- 12The fluid-filled antrum is the hallmark of the tertiary follicle; the secondary follicle is marked by extra granulosa layers and a new theca.
- 13The ovulated cell is a secondary oocyte; meiosis II is completed only after sperm entry, releasing the second polar body.
- 14The LH surge around day 14 triggers ovulation; the corpus luteum's progesterone maintains the endometrium.
- 15Fertilisation occurs in the ampullary region of the fallopian tube.
- 16Morula = 8–16 blastomeres; the blastocyst has an outer trophoblast and an inner cell mass; the trophoblast attaches to the endometrium.
- 17Only during pregnancy do women produce hCG, hPL and relaxin; late in pregnancy, relaxin is secreted by the ovary.
- 18Heart forms by end of month 1; most organ systems by end of week 12; first movements and head hair in month 5; eyelids separate by about week 24.
- 19The foetal ejection reflex triggers oxytocin release, and oxytocin and uterine contractions boost each other by positive feedback.
- 20Colostrum carries several antibodies that give the newborn resistance.
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Key terms
19 terms
- Seminiferous tubule
- Coiled tubule inside a testicular lobule where sperms are produced.
- Sertoli cell
- Supporting cell lining the seminiferous tubule that feeds developing germ cells.
- Leydig cell
- Interstitial cell of the testis that synthesises and secretes androgens.
- Spermiogenesis
- Remodelling of a round spermatid into a motile sperm without cell division.
- Spermiation
- Release of finished sperms from the seminiferous tubule.
- Acrosome
- Enzyme-filled cap on the sperm head that helps it penetrate the ovum.
- Primary follicle
- A primary oocyte surrounded by a single layer of granulosa cells.
- Graafian follicle
- The mature follicle that ruptures at ovulation to release the secondary oocyte.
- Zona pellucida
- Covering around the secondary oocyte; sperm contact with it blocks entry of further sperms.
- Corpus luteum
- Structure formed from the ruptured follicle that secretes progesterone in the luteal phase.
- Menarche
- The first menstruation, at puberty.
- Menopause
- Permanent end of menstrual cycles, around 50 years of age.
- Ootid
- The haploid ovum formed when the secondary oocyte completes meiosis II after sperm entry.
- Morula
- Early embryo of 8–16 blastomeres.
- Blastocyst
- Embryo stage with an outer trophoblast and an inner cell mass, which implants in the endometrium.
- Implantation
- Embedding of the blastocyst in the endometrium, which starts pregnancy.
- Chorionic villi
- Finger-like outgrowths of the trophoblast that interlock with uterine tissue to form the placenta.
- Foetal ejection reflex
- Mild uterine contractions set off by signals from the mature foetus and placenta that start oxytocin release.
- Colostrum
- Milk of the first few days after birth, rich in antibodies.