Spermatogenesis is promoted by:
As male attain puberty. Leydig cells surrounding seminiferous tubules start to secret testosterone harmone which initiate Spermatogenesis in Seminiferous tubules.
Identify the wrong statement from the following.
The process of formation of a mature female gamete is called oogenesis. Unlike sperm formation that starts at pubarty egg formation begins before birth. Primordial germ cells complete the proilferative stage or oogenesis in the early embryonal stage when million of gamete mother cells (oogonia) are formed within each faetal ovary, no more oogonia are formed and added after birth.
The membranous cover of the ovum at ovulation is:
The ovum is enclosed by the inner thin, transparent, non-cellular coat zonapellucidaand outer thick coat corona radiata, During fertilization sperm first comes in contact with the corona radiata and zonapellucida to reach the plasma membrane of the egg(ovum).
A human female reaches menopause around the age of:
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.
Which among the following has 23 chromosomes?
.Zygote: In humans, the male gamete is called sperm, and the female gamete is called an egg. When the gametes join they form a cell called a zygote. Human sperm and eggs contain 23 chromosomes. Human zygotes contain 46 chromosomes.
Spermatogonia: (46 chromosomes, 92 chromatids)
- Has a pair of each chromosome, and each individual chromosome has two chromatids.
- Undergoes mitosis (normal cell division) to produce a primary speratocyte.
Secondary oocyte: The secondary oocyte is the cell that is formed by meiosis I in oogenesis. Thus, it has only one of each pair of homologous chromosomes. In other words, it is haploid. However, each chromosome still has two chromatids, making a total of 46 chromatids (1N but 2C). The secondary oocyte continues the second stage of meiosis (meiosis II), and the daughter cells are one ootid and one polar body.
Secondary oocytes are the immature ovum shortly after ovulation, to fertilization, where it turns into an ootid. Thus, the time as a secondary oocyte is measured in days.
The secondary oocyte is the largest cell in the body, and in humans is just visible to the naked eye.
Oogonia: An oogonium (plural oogonia) is a small diploid cell which upon maturation forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. Oogonia are the cells that turn into primary oocytes in oogenesis. They are diploid, i.e. containing pairs of homologous chromosomes. There are 23 chromosome pairs. Thus, there are 46 chromosomes