Q.(a) What is spermatogenesis?

Spermatogenesis is the process by which diploid spermatogonial cells in the seminiferous tubules of the testis undergo mitotic multiplication and then meiosis to form haploid spermatids, which mature into sperm.

Spermatogenesis = formation of haploid sperm from diploid germ cells in the testis.

Spermatogenesis occurs within the seminiferous tubules of the testis. Diploid spermatogonia lining the tubule wall multiply mitotically; some differentiate into primary spermatocytes, which undergo the first meiotic division to form secondary spermatocytes, and these complete the second meiotic division to produce haploid spermatids. Spermatids then undergo spermiogenesis — a morphological transformation involving loss of cytoplasm, formation of t …

Both the ovum and gametes are haploid; the zygote is not.

Gametes (sperm and ovum) are produced by meiosis and therefore contain only one set of chromosomes — they are haploid (n). The ovum is one such gamete, so it too is haploid. The zygote, formed by fusion of two gametes, restores the di …

The correct regulatory chain is LH stimulating the Leydig cells to secrete testosterone, which in turn drives spermatogenesis.

In the male reproductive (HPG) axis, LH released from the anterior pituitary acts specifically on the Leydig cells (interstitial cells) of the testis, stimulating them to synthesise and secrete testosterone (androgen); testosterone then acts on the seminiferous tubules to stimulate spermatogenesis. (FSH, separately, acts on Sertoli cells, stimulating secretion of factors like ABP that support spermatogenesis, and inhibin from Sertoli cells feeds back to suppress FSH.) Option (a) wrongly places Inhibin between LH and spermatogenesis and omits testosterone/Leydig cells from the correct pathway. Option (c) is wrong because TSH is thyroid-stimulating hormone, which regulates thyroid function, not spermatogenesis, and it does not act on Sertoli cells. Option (d) wrongly uses LTH (luteotropic hormone/prolactin, involved in …

Gametes are usually haploid (n).

In sexually reproducing organisms, gametes are produced by meiosis, which halves the chromosome number. Thus each gamete is haploid (n), carrying one set of chromosomes. When two gametes fuse d …

The striated membrane of the ovum is the zona radiata.

The ovum is enclosed by a thick, transparent, radially-striated glycoprotein layer; the striations (radial appearance) give it the name zona radiata (associated with the zona pellucida of the egg). It plays a role in sperm binding at fertilisation.

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The acrosome, a cap over the sperm head formed from the Golgi complex, contains hydrolytic enzymes (such as hyaluronidase and acrosin) that are released to digest the protective coverings of the ovum, enabling the spe...

The acrosome releases enzymes that dissolve a path through the egg's coverings so the sperm can fertilize it.

The acrosome is a membrane-bound, cap-like structure formed from the Golgi complex that covers the anterior two-thirds of the sperm's head. It is packed with hydrolytic (proteolytic) enzymes, most notably hyaluronidase (which breaks down the hyaluronic acid matrix of the corona radiata surrounding the egg) and acrosin (a protease that digests the zona pellucida, the glycoprotein layer immediately surrounding the ovum's plasma membrane). During fertilization, contact with the ovum's outer layers triggers the acrosome reaction, releasing these enzymes and exposing the inner acrosomal membrane, which toget …