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प्रश्न
Describe the process of oogenesis in human female.
Explain the process of oogenesis in humans.
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उत्तर
Oogenesis is a process of formation of the haploid female gamete i.e. egg or ovum from the diploid germinal epithelium. Oogenesis takes place in the ovaries and is initiated prior to birth of the female baby. It involves the process of mitosis and meiosis. This process can be divided into three stages:
- Multiplication phase: In this stage, the primary germinal cells - PGCs (2n) of ovary undergo repeated mitotic division to form millions of gamete mother cells or oogonial cells (2n). This process is completed in the embryonic stage of human females.
- Growth phase: Some of the oogonia stop division and begin to increase in size and form the primary oocytes (2n). Cellular organelles like ER, Golgi apparatus and mitochondria increase in number.
- Maturation phase:
- The primary oocytes (2n) enter the maturation phase, which includes meiotic division (Meiosis I and Meiosis II). The diploid primary oocytes undergo meiosis I (reduction division) to form two haploid daughter cells having 23 chromosomes. However, due to unequal division of cytoplasm, of the two daughter cells, one is a large cell, called secondary oocyte (n) and another is a small cell, called 1st polar body (n). Generally, the 1st polar body does not enter meiosis II.
- The secondary oocyte (n) proceeds only upto metaphase II of meiosis II and its division is further stopped or arrested at this stage. The secondary oocyte is shed from the Graafian follicle and ovary during ovulation. Meiosis II is completed only if fertilization occurs. This last phase is usually completed in the ampulla of the fallopian tube at the time of fertilization. In this division also, the two unequal daughter cells are formed i.e. the large cell is ovum (n) and the small cell is 2nd polar body (n). The ovum (n) so formed functions as the female gamete and is ready for fertilization. If the secondary oocyte is not fertilized by a sperm/spermatozoa, it is shed off along with menstruum.
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संबंधित प्रश्न
The following is the illustration of the sequence of ovarian events (a − i) in a human female
(i) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents.
(ii) Name the ovarian hormone and the pituitary hormone that have caused the above mentioned event.
(iii) Explain the changes that occur in the uterus simultaneously in anticipation.
(iv) Write the difference between ‘c’ and ‘h’.
(v) Draw a labeled sketch of the structure of a human ovum prior to fertilization.
What is oogenesis?
Which precautions will you follow to maintain the reproductive health?
Multiple choice question.
The given figure shows human sperm. Various parts of it are labelled as A, B, C, and D. Which labelled part represents acrosome?
At the time of birth, there are _______________ oocytes in the ovary of a female foetus.
The Androgen Binding Protein (ABP) is produced by ____________.
Answer the following type of question Assertion (A) and Reason (R).
(A) - In human males, testes are extra-abdominal and lie in scrotal sacs.
(R) - Scrotum acts as a thermoregulator and keeps the temperature lower by 2°C for normal sperm production.
Describe the structure of the human ovum with a neat labelled diagram.
The immature male germ cells differentiates into ______ at the end of meiosis I.
The human male gamete is usually about ______ in length.
In human beings, the largest cell formed during Oogenesis is ______
Sertoli cells are found in ______.
Connective tissue around seminiferous tubules possess endocrine cells called ______.
Cells of corona radiata remain grouped together by ______.
The nutritive cells found in seminiferous tubules are ______.
1st polar body is formed at which stage of oogenesis?
Layers of an ovum from outside to inside is ______.
Which of the following cells during gametogenesis is normally diploid?
Draw a neat and labelled diagram of spermatogenesis.
Meiotic division of the secondary oocyte completed ______.
