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Tutorial Activity :

1. Draw a mature graafian follicle, label the parts &
state their functions
2. Draw & explain the hormonal regulation of the
phases of the menstrual cycle.
3. Explain the function of the corpus luteum.
4. Explain the process of oogenesis in detail. Include
diagrams.

1 answer

1. Mature Graafian Follicle

Diagram: While I can't draw, I can describe a mature Graafian follicle's structure for you to visualize or draw.

Parts of the Graafian Follicle:

  • Antrum: The fluid-filled cavity that expands during the formation of the follicle and contains follicular fluid which nourish the egg.
  • Granulosa Cells: These are the layers of cells surrounding the oocyte. They produce estrogen in response to follicle-stimulating hormone (FSH).
  • Theca Cells: These are cells that form a layer outside the granulosa cells and help produce androgens that are converted to estrogen.
  • Oocyte: The egg cell (often called the ovum) that is released during ovulation.
  • Zona Pellucida: The thick, glycoprotein layer surrounding the oocyte which plays a role in fertilization.
  • Cumulus Oophorus: A mass of granulosa cells that surrounds and supports the oocyte.

Functions:

  • The antrum provides a space for follicular fluid, allowing the follicle to grow.
  • Granulosa cells produce hormones like estrogen that regulate the menstrual cycle and promote the development of the oocyte.
  • Theca cells provide the necessary hormones that support the granulosa cells and oocyte.
  • The zona pellucida acts as a protective layer and aids in sperm binding during fertilization.
  • The cumulus oophorus supports the oocyte and facilitates its release during ovulation.

2. Hormonal Regulation of the Phases of the Menstrual Cycle

Phases of the Menstrual Cycle:

  1. Follicular Phase (Days 1-14)

    • Hormones: FSH stimulates the growth of ovarian follicles; these produce estrogen.
    • Function: The rising estrogen levels promote the thickening of the endometrium and prepare the uterus for potential implantation.

  2. Ovulation (Day 14)

    • Hormone Surge: A peak in estrogen leads to a surge in Luteinizing Hormone (LH), prompting ovulation.
    • Function: The mature follicle releases the oocyte.

  3. Luteal Phase (Days 15-28)

    • Hormones: The corpus luteum produces progesterone and some estrogen.
    • Function: Progesterone stabilizes the endometrium, ensuring it's ready for implantation. If fertilization does not occur, the corpus luteum degrades, leading to a drop in hormone levels and the onset of menstruation.

Diagram: A flowchart showing the interplay of FSH, LH, estrogen, and progesterone across those phases.

3. Function of the Corpus Luteum

The corpus luteum is a temporary endocrine structure that forms post-ovulation from the remnants of the mature ovarian follicle.

Functions:

  • Hormone Production: It secretes progesterone, which is crucial for:
    • Maintaining the endometrium (the uterine lining) in a thickened state.
    • Inhibiting uterine contractions, preventing menstruation during early pregnancy.
    • Stimulating the development of mammary glands.
  • If fertilization occurs, the corpus luteum is maintained by human chorionic gonadotropin (hCG) produced by the developing placenta. If no fertilization occurs, it degenerates into the corpus albicans, leading to decreased progesterone and subsequent menstruation.

4. Oogenesis

Oogenesis is the process of egg (oocyte) formation in the ovaries. It occurs in several stages:

  1. Fetal Development:

    • Oocytes are formed from primordial germ cells during fetal life, leading to the formation of primary oocytes, which are arrested in prophase I of meiosis.

  2. Puberty:

    • Each menstrual cycle, several primary oocytes resume development; however, only one typically completes meiosis.
    • Primary oocytes complete the first meiotic division just before ovulation, becoming secondary oocytes and are arrested in metaphase II.

  3. Ovulation:

    • During ovulation, the secondary oocyte is released from the ovary. If fertilization occurs, it will complete the second meiotic division, producing a mature ovum and a polar body (which typically degenerates).

  4. Post-Fertilization:

    • The haploid ovum combines with a haploid sperm to form a diploid zygote, marking the initiation of a new organism.

Diagram: Flowchart illustrating the stages of oogenesis from primordial germ cells to mature ovum, highlighting locations in the ovaries.

This outline provides you with essential details on the specified subjects, and you can create your diagrams using this information as a guide.