Test: Gametogenesis & Menstrual Cycle

As male attain puberty. Leydig cells surrounding seminiferous tubules start to secret testosterone hormone which initiate Spermatogenesis in Seminiferous tubules.It is the process by which stem cells develop into mature spermatozoa. There are three phases:
(1) Spermatocytogenesis (Mitosis)
(2) Meiosis
(3) Spermiogenesis.

• The process of formation of a mature female gamete is called oogenesis.
• Unlike sperm formation that starts at puberty, egg formation begins before birth.
• Primordial germ cells complete the proliferative stage or oogenesis in the early embryonic stage when million of gamete mother cells (oogonia) are formed within each fetal ovary, no more oogonia are formed and added after birth. 

The ovum is enclosed by the inner thin, transparent, non-cellular coat zona pellucida and outer thick coat corona radiata, During fertilization sperm first comes in contact with the corona radiata and zona pellucida to reach the plasma membrane of the egg(ovum).

The age at which a woman starts having menstrual periods is also not related to the age of menopause onset. Most women reach menopause between the ages of 45 and 55, but menopause may occur as earlier as ages 30s or 40s, or may not occur until a woman reaches her 60s.

• Spermatogonia are the cells on the inside wall of seminiferous tubules and consist of 46 chromosomes.
• Oogonia are also diploid and are formed in the fetal ovary.
• Zygote is also diploid and fertilised ovum formed by fusion of male and female gametes.
• Secondary oocyte has 23 chromosomes and is formed by meiosis-I of primary oocyte.