The primary sex organs: the testis in the males and the ovaries in the female produce gametes, i.e., sperms and ovum, respectively, by the process called gametogenesis. Gametogenesis for the formation of sperms is termed spermatogenesis, while that of ova is called oogenesis. Both spermatogenesis and oogenesis are accomplished in three phases: multiplication phase, growth phase and maturation phase.
- Multiplication phase: Here multiplication of the germ cells occurs through mitosis so as to increase their number.
- Growth phase: The germ cells increase in size
- Maturation phase: Germ cells undergo meiosis to produce haploid gametes.
Spermatogenesis: It is the process of formation of haploid spermatozoa (sperms) from diploid spermatogonia inside the testes of the male. It occurs in the seminiferous tubules of the testes.
Oogenesis: It is the process of formation of functional haploid ova from the diploid germinal cells in the ovary.
Spermatogenesis vs Oogenesis
1. It occurs inside testis
2. All stages are completed inside testis.
3. It is a continuous process.
4. Spermatogonia develop from germinal epithelium lining the seminiferous tubules.
5. Some cells of the germinal epithelium function as support , also called sertoli cells.
6. All the spermatogonia divide to form spermatocytes.
7. Growth phase is short.
8. Primary spermatocyte divides by meiosis I to form two secondary spermatocytes.
9. Secondary spermatocyte divides by meiosis II to produce two spermatids.
10. A spermatocyte forms four spermatozoa.
11. Sperms are smaller than spermatocytes.
12. Nucleus undergoes condensation in the sperm.
13. Reserve food is little in the sperms.
14.It produces motile male gametes.
1. It occurs inside ovary.
2. Major part of oogenesis occurs inside ovary but last stages occur inside oviduct.
3. It is discontinuous process with early stages taking place in foetus and the rest later in life.
4. Oogonia develop from germinal epithelium overlying the ovary.
5. There is no such differentiation.
6. Only some oogoinia give rise to oocytes.
7. Growth phase is prolonged.
8. Primary oocyte undergoes meiosis I to form one secondary oocyte and one polar body
9. Secondary oocyte divides by meiosis II to form one ovum and one polar body.
10. A oocyte forms only one egg or ovum.
11. Eggs are larger than oocytes.
12. Nucleus remains uncondensed in the ovum.
13. Ovum collects a lot of reserve food and other biochemicals.
14. It forms non motile female gametes.