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Human Reproduction - Female Reproductive System

Grade 12CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The female reproductive system consists of a pair of ovaries, a pair of oviducts, uterus, cervix, vagina, and external genitalia located in the pelvic region.

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Ovaries are the primary female sex organs that produce the female gamete (ovum) and several steroid hormones like EstrogenEstrogen and ProgesteroneProgesterone.

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The female accessory ducts include the Fallopian tubes (oviducts), uterus, and vagina. The fallopian tube is divided into the infundibulum (with fimbriae), ampulla, and isthmus. Fertilization occurs at the ampullary−isthmicampullary-isthmic junction.

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The wall of the uterus has three layers: the external thin perimetriumperimetrium, middle thick layer of smooth muscle myometriummyometrium, and inner glandular layer endometriumendometrium which undergoes cyclic changes during the menstrual cycle.

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Oogenesis is the process of formation of a mature female gamete. Unlike spermatogenesis, it is initiated during the embryonic development stage where a couple of million gamete mother cells (oogoniaoogonia) are formed within each fetal ovary.

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The menstrual cycle consists of the menstrual phase, follicular phase (proliferative phase), ovulatory phase (at day 1414), and luteal phase (secretory phase).

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The 'LH surge' refers to the rapid secretion of LHLH leading to its maximum level during the mid-cycle, which induces the rupture of the Graafian follicle and thereby the release of the ovum (ovulationovulation).

📐Formulae

1 Primary Oocyte (2n)→Meiosis I1 Secondary Oocyte (n)+1 First Polar Body (n)1 \text{ Primary Oocyte } (2n) \xrightarrow{\text{Meiosis I}} 1 \text{ Secondary Oocyte } (n) + 1 \text{ First Polar Body } (n)

1 Secondary Oocyte (n)→Meiosis II1 Ootid/Ovum (n)+1 Second Polar Body (n)1 \text{ Secondary Oocyte } (n) \xrightarrow{\text{Meiosis II}} 1 \text{ Ootid/Ovum } (n) + 1 \text{ Second Polar Body } (n)

Day of Ovulation=Total Days of Cycle−14\text{Day of Ovulation} = \text{Total Days of Cycle} - 14

Diploid Number (2n)=46, Haploid Number (n)=23\text{Diploid Number (2n)} = 46, \text{ Haploid Number (n)} = 23

💡Examples

Problem 1:

If a female has a regular menstrual cycle of 3232 days, on which day is ovulation most likely to occur?

Solution:

32−14=1832 - 14 = 18

Explanation:

In a human menstrual cycle, the luteal phase (post-ovulatory phase) is generally constant at 1414 days. Therefore, ovulation occurs approximately 1414 days before the next expected menstruation.

Problem 2:

How many ova and polar bodies will be formed from 100100 primary oocytes?

Solution:

100 Ova and 100−200 Polar Bodies100 \text{ Ova and } 100-200 \text{ Polar Bodies}

Explanation:

Each primary oocyte undergoes unequal meiotic division to produce one functional haploid ovum (nn) and one or more polar bodies. Thus, 100100 primary oocytes result in 100100 ova.

Problem 3:

Identify the ploidy of the following cells: Oogonia, Primary Oocyte, Secondary Oocyte, and Ovum.

Solution:

Oogonia: 2n, Primary Oocyte: 2n, Secondary Oocyte: n, Ovum: n\text{Oogonia: } 2n, \text{ Primary Oocyte: } 2n, \text{ Secondary Oocyte: } n, \text{ Ovum: } n

Explanation:

Oogonia and Primary oocytes are formed by mitosis or are in the early stages of Meiosis I (not completed), keeping them diploid (2n2n). The completion of Meiosis I reduces the chromosome number by half, making the Secondary Oocyte and the Ovum haploid (nn).