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Gametes, known as reproductive cells are also commonly referred to as sex cells. These gametes help in the process of sexual reproduction in human beings and are responsible for the formation of a new cell known as a zygote. The male gametes present in the reproductive system are called sperm and female gametes found in the reproductive system is called eggs or ova. These reproductive cells are commonly an outcome of a process known as meiosis. The differences of their aspects can be examined in the transverse section (T.S.) of these organs. Given below is the elaborated information on the stages of the gamete development.
| Table of Content |
Key Terms: Gametes, Gamete Formation, Mammalian, Ovary, Testis, Procedure, Observation, Eggs, Sperm, Transverse Section
Aim of the Experiment
To study the stages of gametogenesis in mammalian testis and ovary
Tools Required for the Experiment
- Permanent slides of T.S. of mammalian ovary and testis.
- Compound microscope.
- Lens-cleaning paper.
- Cleaning fluid.
Procedure
- Firstly, wash your hands properly and then dry them thoroughly.
- Secondly, pour some cleaning fluid on the lens-cleaning papers; wipe slides, the microscope’s eye and objective lenses.
- Thirdly, place both slides one by one on the microscope’s platform. Observe the slides under lower magnification and then the higher one.
- Fourthly, remember the stages of the development of gametes.
- Fifthly, write down your observations in biology practical copy, label and draw diagrams of both T.S. of mammalian ovary and testis.
T.S. of Mammalian Ovary
The mammalian ovaries are the reproductive organ in females inside which sex cells like eggs or ova are produced. In addition to the sex cells, the ovaries come in pairs and produce Oestrogen and Progesterone hormones that trigger reproduction in females. While ovaries are the primary reproductive organs in females, males have testis as their primary reproductive organ.
Each ovary consists of an outer cortex containing follicles, interstitial cells and oocytes. You will also find an inner medulla that contains fibrous tissues, blood vessels and nerves.
The T.S. of the ovary can be studied and identified through experimental slides.
T.S. of Human Ovary
Observation Under Microscope
- First, there is a Germinal Epithelium that covers a group of tissues, with a cell called ovum inside it. Additionally, one or more layers of follicular cell guard the ovum, the number of which increases as the ovum matures.
- In the second stage, a cavity called an antrum appears.
- Thirdly, as the cavity enlarges, the follicle grows as well. In this stage, the process during which the Graafian follicle readies to release the ovum is called ovulation.
- In the final stage, the Corpus luteum that forms from ruptured follicles containing lutein cells and are surrounded by blood clots and Corpus Albicans may be noticeable, which differs in features from each other and also from Graafian follicle.
- Atretic follicle shows that the follicle cells are disorganized and carries a sign of nuclear necrosis. It also shows the reduction in the size of the oocyte.
T.S. Of Mammalian Testis
The male reproductive organs have two primary structures, viz, a pair of testes and some accessory reproductive structures. Adult mammalian testes perform two essential functions—spermatogenesis (the process of gametogenic development) and male sex hormone production which is produced in the testis known as testosterone. It influences sex drive, fertility and also increases bone mass and muscle power.
There are a few diseases that are linked with the testes such as testicular cancer, infertility issues, hypogonadism, testicular trauma, swelling, etc. These diseases cause bruising, clotting and severe pain.
T.S. of Human Testis
Observation Under Microscope
- Many seminiferous tubules are somewhat round or oval.
- The transverse section of the mammalian testis under the microscope shows a few cells like primary and secondary spermatocytes, germinal epithelium, spermatozoa and spermatids.
- The permanent testis slide shows that there are blood vessels and a special type of cell named Leydig’s cells found between tubules.
- There is also Sertoli cells holding the sperms.
- The mature sperms continue to reside inside the lumen of the seminiferous tubule. In this final stage, the sperm grows a head and tail but the middle section is still yet to mature.
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Difference Between Testis And Ovary
| Parameters | Testis | Ovary |
|---|---|---|
| Gender | It is the male gonad | It is the female gonad |
| Produces | It produces Spermatozoa | It produces Ova |
| Hormone Production | Testosterone | Oestrogen and Progesterone |
| Location | Outside the body | Inside the body |
Difference Between Testis And Ovary
Things To Remember
- The size of the ovaries changes with the maturity of a female body.
- Ovaries are greyish-pink in colour and are capable of holding around a million eggs at a time.
- During the reproductive stage, the eggs fertilize inside the ovary and expand in size.
- Once a female hits menopause, the uterus is capable of holding only about 400-500 which are unsuitable for fertilization.
Sample Questions
Ques. What type of Mammals has Ovaries? (3 Marks)
Ans. The ovary is the primary reproductive organ in females that is vital for the production of reproductive hormones. Almost all female vertebrates have ovaries. Platypuses and birds, however, do not have a mature right ovary and only their left ovary is functional.
Ques. What would happen if meiosis fails to occur in gametocytes? (5 Marks)
Ans. If meiosis fails to occur in gametocytes properly, a fusion of gametes would ultimately result in the doubling of chromosomes in each successive reproduced generation.
For instance: For a successful reproduction, the result is an egg or sperm with only 23 chromosomes. If meiosis does not occur properly, there would either be too many or not enough chromosomes and upon fertilization, the baby could end up receiving extra chromosomes.
However, if meiosis fails to occur entirely, gametes will not be formed. Fertilization (fusion of gametes) which helps to form the zygote, fails to form as a result of which there is no development of a new organism and hence, failure in a complete lifecycle.
Ques. What is the difference between testis and ovary? (3 Marks)
Ans. The testis is the primary male reproductive organ that produces spermatozoa and hormones called testosterone while the ovary is the main female reproductive organ that produces eggs or ova and hormones called oestrogen and progesterone.
Ques. What are the different diseases linked with the female ovary? (5 Marks)
Ans. The main disease associated with the ovary i cysts. The polycystic ovary syndrome commonly referred to as PCOS is a hormonal disorder that causes the enlarging of the ovary and small cysts on the outer edge. The underlying cause though unknown, however, genetic factors and some environmental factors may contribute to this disease.
The symptoms of the disease are irregularity in the menstrual cycle, spotting, untimely heavy or light bleeding, dark patches on the head, loss of hair, oily skin and acne. Some patients are known to have experienced obesity and excess growth of body hair.
Ques. What is Corpus Luteum? (3 Marks)
Ans. Corpus Luteum is a group of cells that forms inside an ovary. During the early stages of pregnancy, it releases progesterone hormones.
Ques. Spermatogenesis is a continuous process. Justify the statement. (3 Marks)
Ans. The process in which sperms in human males are formed by the germinal cells called spermatogonia is called spermatogenesis. These cells evolve to form primary spermatocyte, secondary spermatocyte, and spermatid, then spermatozoa to sperms throughout the lifecycle of human males. This is the reason why spermatogenesis is a continuous process.
Ques. What are the consequences of failure of ovulation? (3 Marks)
Ans. The first and foremost consequence of the failure of ovulation is:
- Absence of pregnancy;
- increase or leading to infertility;
- it may lead to polycystic ovarian syndrome PCOS (cyst in the ovary);
- lead to osteopenia (decrease in bone density).
Ques. What is the function of an ovary in the human body? (5 Marks)
Ans. The ovary releases an ovum which travels down the fallopian tube and into the uterus where it gets fertilized by a sperm. Secretion of oestrogen and progesterone hormones is also done by the ovary. These hormones are useful for the development of the human body and various female characteristics.
The process during which the ovaries releases eggs is known as Ovulation. Stress and other factors often lead to irregular menstrual cycles that may delay the process of ovulation.
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