नमस्कार मित्रांनो इयत्ता बारावी Biology या Subject च्या Practical मध्ये PART - B: Demonstration Experiments (Spotting) हा भाग Practical Exam च्या दृष्टीने फार महत्त्वाचा आहे. या Blog Post मध्ये आपण Spotting Practical Number 6: Study of T.S. testis, T.S. ovary and V.S. of blastula, through permanent slides ह्या Practical Experiment चे Answer पाहणार आहोत. खाली दिलेल्या उत्तरांमध्ये काही अडचण असल्यास आम्हाला comment करा किंवा तुमच्या संबंधीत विषय शिक्षकांशी चर्चा करा.
B. DEMONSTRATION EXPERIMENTS (Spotting)
6. Study of T.S. testis, T.S. ovary and V.S. of blastula, through permanent slides.
1. T.S. Testis :-
• Internal structure of testis shows the presence of tunica albuginea and seminiferous tubules. Testis Any is externally covered by fibrous connective tissue called as tunica albuginea. It is internally covered by tunica vascularis formed by capillaries and externally by an incomplete covering point called as tunica vaginalis.
• Seminiferous tubules are lined by cuboidal germinal epithelial cells.
• It shows different stages of spermatogenesis like spermatogonia, primary and secondary spermatocytes, spermatids and sperms. Few large pyramidal cells present interrupting germinal epithelium are nurse cells or sertoli cells. Sperm bundles get attached to sertoli cells with their heads. Function of sertoli cells is to provide nourishment to the sperm till maturation.
Figure :-
2. T.S. of Ovary :-
• Internally the mammalian ovary shows compact structure with outer cortex and inner medulla The medulla shows connective tissue called as stroma. The cortex is lined by germinal epithelium. Cortical region shows different stages of development of ovarian follicles or Graffian follicle. Each follicle contains a large ovum surrounded by many layers of follicle cells. Different stages of developing ovarian follicles are seen in the cortex and consist of oocytes in different developmental stages. In the beginning, a single layer of follicular cells around each oocyte is seen. The entire structure is called a primordial follicle. The primary follicles are surrounded first by a layer of follicular cells. As the follicle grows, it forms a secondary and mature follicle. The follicle grows, it forms a clean glycoprotein layer, called the zona pellucida between primary oocyte and granulosa cells. The innermost layer of granulosa cells becomes firmly attached to the zona pellucida to form corona radiata. (Corona=crown; radiate=radiating)
• The outermost granulosa cells rest on a basement membrane. Encircling the basement membrane is a region called theca folliculi. Many capillaries are present in the theca folliculi.
• As a primary follicle continues to grow, the theca folliculi gets differentiated into -
i) Theca interna: - A highly vascularised internal layer of secretory cells.
ii) Theca externa: An outer layer of connective tissue cells.
• One ovum from mature follicle is released from on ovary in every menstrual cycle (alternately in right and left ovary). It may also show the presence of mass of yellow cells called corpus luteum, formed in the antrum or follicular cavity of an empty Graffian follicle after the release of its ovum (ovulation). If the ovum is fertilised, corpus luteum secrets progesterone to maintain pregnancy and relaxin towards the end of pregnancy. The ovarian cortex may also show white body or corpus albicans representing a degenerating corpus luteum if the ovum is not fertilised.
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| Fig. T.S. of ovary |
Figure :-
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| Fig. V.S. of blastula |
3. Study of V.S. blastula (blastocyst or blastodermic vesicle) from permanent slide :-
The V.S. blastula shows outermost, small, flattened cell layer called trophoblast. It encloses a cavity called blastocyst cavity or blastocoel and an inner cell mass. The blastocyst cavity is filled with a fluid which is absorbed by trophoblast cells. The inner cell mass is attached to one side to trophoblast cell layer. The trophoblast cells in contact with the inner cell mass (embryonal knob), are called the cells of Rouber. The trophoblast cell layer produces extra embryonic membranes while the inner cell mass further develops into proper embryo.
Comment on the difference between T.S. of testis and T.S. of ovary :
| T.S. of Testis | T.S. of Ovary |
|---|---|
| 1) Internal structure shows the presence of tunica albuginea & seminiferous tubules. | 1) Internally, it shows compact structure with outer cortex & inner medulla. |
| 2) Seminiferous tubules are lined by cuboidal germination epithelial cells. | 2) The cortex is lined by germinal epithelium. |
| 3) Seminiferous tubules show different stages of spermatogenesis like spermatogonia, primary & secondary spermatocytes, spermatids & sperms. | 3) Cortical region shows different stages of development of ovarian follicles like primordial, primary, secondary, mature (Graafian) follicle, etc. |
| 4) It shows spermatogenesis. | 4) It shows oogenesis. |
Sketch Figure :-
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| Fig 1. |
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| Fig 2. |
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| Fig 3. |
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| Fig 4. |
Questions
1. Give functions of :
a. Sertoli cells
Ans :- Sertoil cells provide nourishment to the developing sperms
b. Leydig's cells
Ans :- Leydig's cells secrete the male sex hormone androgen or testosterone
c. Trophoblast
Ans :- Trophoblast cells absorb nutrition for the developing embryo
2. Why are testis extra abdominal in position?
Ans :- Testies are extra abdominal in position. They lie in the scrotum because sperm production needs a temperature 1 - 2°C less than the body temperature
3. Find out more about cells of Rauber.
Ans :- The trophoblast cells in contact with the inner cell mass are called cells of Rauber.
4. Differentiate between spermatogenesis and oogenesis.
| Spermatogenesis | Oogenesis |
|---|---|
| 1) It occurs in the testes of males. | 1) It occurs in the ovaries of females. |
| 2) Produces sperm cells continuously from puberty onwards. | 2) Produces egg cells intermittently, one per menstrual cycle. |
| 3) Four haploid sperm cells are produced from one spermatogonium. | 3) One haploid egg cell and three polar bodies are produced from one oogonium. |
5. Write functions of :
a. Blastocoel
Ans :- Blastocoel permits the migration of cells during gastrulation
b. Inner cell mass
Ans :- Inner cell mass forms the entire embryo. It is the source of embryonic stem cells.
c. Trophoblast
Ans :- Trophoblast cells absorb nourishment for the developing embryo.
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