Lesson 9 of 9 · 13 min

Chapter review

Watch a class

The whole chapter on YouTube

Whole chapter revision with diagrams
NCERT Wallah · Hinglish · Whole chapter · Open on YouTube

Full chapter review in English
Dr. Anand Mani · English · Whole chapter · Open on YouTube

Must-know facts

20 facts

1Scrotal temperature is about 2–2.5 °C below internal body temperature; this is needed for spermatogenesis.
2Each testis has about 250 testicular lobules, each with 1–3 seminiferous tubules.
3Sertoli cells nourish germ cells and respond to FSH; Leydig cells make androgens and respond to LH.
4Seminal plasma is rich in calcium, fructose and certain enzymes.
5Oviduct length is about 10–12 cm; its parts from ovary to uterus are infundibulum (with fimbriae), ampulla, isthmus.
6Uterine wall layers from outside: perimetrium, myometrium (contracts at delivery), endometrium (changes with the cycle).
7One primary spermatocyte → 2 secondary spermatocytes → 4 spermatids → 4 sperms; spermatogonia and primary spermatocytes are diploid (46), later stages haploid (23).
8Spermiogenesis = spermatid to sperm; spermiation = release of sperms from the seminiferous tubules.
9A 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.

Common traps

Where marks are lost

Pairing FSH with Leydig cells and LH with Sertoli cells.

LH → Leydig → androgens; FSH → Sertoli → factors for spermiogenesis. Remember 'L with L': LH acts on Leydig.

Saying the ovary releases a mature ovum that has finished meiosis.

It releases a secondary oocyte arrested in meiosis II. Meiosis II completes only after a sperm enters, giving the ootid and the second polar body.

Thinking oogonia keep forming throughout reproductive life, like spermatogonia.

All oogonia form during foetal life and none are added after birth; spermatogenesis, by contrast, begins at puberty and continues.

Confusing spermiogenesis with spermiation.

Spermiogenesis is the transformation of spermatid into sperm; spermiation is the later release of sperms from the seminiferous tubules.

Placing fertilisation in the uterus or in the isthmus.

Fertilisation happens in the ampullary region of the oviduct; the zygote then cleaves as it travels through the isthmus to the uterus.

Believing hCG is secreted by the pituitary, or that relaxin comes from the placenta.

hCG and hPL come from the placenta; relaxin comes from the ovary in the later phase of pregnancy. All three appear only in pregnancy.

Calling the endometrium's regrowth after menstruation the secretory phase.

Regrowth under rising estrogen is the follicular (proliferative) phase; the progesterone-dominated phase after ovulation is the luteal (secretory) phase.

Assuming the mother's ovum decides the baby's sex.

All ova carry X; the sperm carries X or Y, so the father's sperm determines the sex of the child.

Mixing up which layer of the blastocyst forms the embryo.

The inner cell mass forms the embryo; the trophoblast attaches to the endometrium and later forms chorionic villi of the placenta.

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.

Test yourself: 10 questionsExam-style questions on Human Reproduction, with full solutions.Start