What traumatic event does Zitkala-Sa describe at the school?

The forcible cutting of her long hair

Why was the cutting of her hair so humiliating to Zitkala-Sa?

Among her people, shingled hair was worn by cowards and mourners

Where does spermatogenesis occur and what hormone initiates it?

Spermatogenesis occurs in the seminiferous tubules of the testes and is initiated at puberty by gonadotropin-releasing hormone stimulating FSH and LH secretion.

What is the function of Sertoli cells?

Sertoli cells (sustentacular cells) nourish and support the developing germ cells in the seminiferous tubules.

What is the role of Leydig cells?

Leydig cells (interstitial cells) lie outside the seminiferous tubules and synthesise and secrete testicular hormones called androgens (mainly testosterone).

When is the secondary oocyte released during the menstrual cycle?

The secondary oocyte is released at ovulation, around the middle of the cycle (about day 14), triggered by an LH surge.

What event marks the beginning of the menstrual cycle?

The cycle begins with menstruation (the menstrual phase), the breakdown and shedding of the uterine endometrium.

Where does fertilisation normally occur in humans?

Fertilisation normally occurs in the ampullary region (ampulla) of the fallopian tube.

What are the three primary germ layers and when do they form?

The ectoderm, mesoderm and endoderm form during gastrulation; they give rise to all tissues and organs of the body.

What is the significance of colostrum?

Colostrum is the yellowish first milk rich in antibodies (especially IgA) that provides immunity to the newborn.

Name the hormones secreted by the placenta.

The placenta secretes hormones such as human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens and progestogens.

What triggers parturition?

A foetal ejection reflex triggers the release of oxytocin from the maternal pituitary, causing strong uterine contractions; the signals originate from the fully developed foetus and placenta.

Human Reproduction

Class 12 Biology · Biology · Chapter 2

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CBSE Class 12 · Biology

Genetics + Evolution: Unit VII, 20 marks

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CBSE Class 12 · Biology

Genetics + Evolution: Unit VII, 20 marks

Marks booster + cheatsheet: key concepts in 2 lines each, common traps
16 marks: Reproduction, Unit VI
12 marks each: Units VIII and IX
10 marks: Ecology, Unit X
13 chapters, with page numbers
Common traps, corrected

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Summary

This chapter describes the structure and functioning of the human reproductive system and the events of reproduction. The male system includes the testes, where spermatogenesis produces sperm in the seminiferous tubules under the influence of FSH, LH and testosterone, along with accessory ducts and glands that contribute to semen. The female system includes the ovaries, where oogenesis and folliculogenesis occur, fallopian tubes, uterus, vagina and accessory structures. Gametogenesis converts germ cells into haploid gametes; a mature sperm has a head, middle piece and tail, while the secondary oocyte is released at ovulation. The menstrual cycle, controlled by the hypothalamus-pituitary-ovary axis (GnRH, FSH, LH, estrogen, progesterone), involves the follicular, ovulatory and luteal phases, with menstruation occurring if fertilisation fails. Fertilisation in the ampulla forms a zygote, which undergoes cleavage to form a blastocyst that implants in the uterine wall. Embryonic development establishes the three germ layers and the placenta, the structural and functional link supplying nutrients and removing wastes, also acting as an endocrine organ. Gestation culminates in parturition, triggered by the foetal-placental signals and oxytocin, followed by lactation, with colostrum providing antibodies to the newborn.

Male reproductive systemFemale reproductive systemGametogenesis: spermatogenesis and oogenesisMenstrual cycleFertilisation and implantationPregnancy, parturition and lactation

Key terms

Spermatogenesis

The process of formation of haploid sperm from diploid spermatogonia in the seminiferous tubules of the testes.

Oogenesis

The process of formation of a mature ovum (egg) from oogonia in the ovary, beginning before birth.

Menstrual cycle

The cyclic changes in the reproductive system of female primates governed by ovarian and pituitary hormones, repeating about every 28 days.

Blastocyst

The early stage of the embryo, formed after cleavage, that implants into the uterine wall.

Placenta

The structural and functional connection between the developing foetus and the mother's uterus, enabling exchange and hormone secretion.

Parturition

The process of delivery of the foetus (childbirth) induced by a neuroendocrine mechanism involving oxytocin.

Extra questions & answers

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Spermatogenesis takes place in the:

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