Biology Class 12

Identification of stages of gamete development, i.e., T.S. of testis and T.S. of ovary through permanent slides (from grasshopper/mice)

Identification of stages of gamete development, i.e., T.S. of testis and T.S. of ovary through permanent slides (from grasshopper/mice)

Aim: Identification of stages of gamete development, i.e., T.S. of testis and T.S. of ovary through permanent slides (from grasshopper/mice)

Theory:

1. Gametes are the sex cells involved in the process of sexual reproduction.

2. The gametes differ from all other cells (somatic cells) of our body in that their nuclei contain only half the number of chromosomes found in hr nuclei of somatic cells.

3. Gametogenesis for the formation of sperm is termed as spermatogenesis, while that of ova is called oogenesis.

4. Spermatogenesis occurs in the seminiferous tubules of the testes, whereas oogenesis occurs in ovaries.

Material/Apparatus Required:

• Permanents slides of TS of testes and ovary
• Microscope

Procedure:

Fix the permanent slide under the microscope. First observe it under the low power and then under high power

Observation:

T.S of testis

1. The testis of a mouse (mammal) is covered by thick fibrous tissue called tunica albuginea.
2. The testis consists of numerous seminiferous tubules embedded in the interstitial tissue.
3. Various types of germinal cells are present from outside toward lumen in the following sequence. Spermatogonia → spermatocytes → spermatids → spermatozoa → sperms.
4. Between the germinal cells, pyramids shaped cells called Sertoli cells are present.
5. A large number of spermatozoa with their hands embedded in Sertoli cells are present in te lumen of seminiferous tubule.
6. The interstitial tissue also contains leydigs cells, which produces male sex hormones testosterone.

T.S of ovary

1. A mouse is a solid structure bounded by germinal epithelium followed by a thick layer of fibrous tissue, the tunica albuginia.
2. The ovary consists of outer cortex and inner medulla.
3. The medulla contains many round or oval bodies called ovarian or Graafian follicles at various stages of development.
4. The medulla also contains blood vessels, nerves fibers and some smooth muscles.
5. Each follicle contains a large ovum surrounded by many layers of follicle cells.
6. The cortex contains young and mature follicles.
7. The cortex may also contain a large mass of yellow cells termed corpus leutem, formed in an empty graafian follicle after the release of its ovum.

Precautions:

1. First observe the slide under low power and then under high power of the microscope.
2. Use fine adjustment of the microscope for focusing the slide under high power.

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