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Human Reproduction - Female Reproductive System

Grade 12CBSEBiology

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

🔑Concepts

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.

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

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 ampullaryisthmicampullary-isthmic junction.

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.

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.

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

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 Cycle14\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:

3214=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 100200 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).

Female Reproductive System - Revision Notes & Key Diagrams | CBSE Class 12 Biology