Question

Describe the body structures that a sperm cell and a secondary oocyte will encounter prior to their encounter and merging to form a zygote. Your response should include a thorough review of the structures connecting the epididymis to the external urethral orifice, and how the structures (and secretions from those structures, to be discussed in detail) support and assist the sperm cell in its trip out of the body. Also, the response should thoroughly describe the structures and obstacles that the sperm cell will encounter within the female body, from the v@gina to the oviduct. For the secondary oocyte, describe the structures it encounters and passes through before meeting up with the sperm cell in the oviduct.

Answer 1

Seminiferous tubules unite at the upper end of testis to form a structure called “epididymis.” Seminiferous tubules are the site of production of sperm cells.

Interstitial cells or the Leydig cells are the endocrine cells present in the connective tissue surrounding the seminiferous tubules. These cells secrete testosterone.

The seminiferous vesicles release sperm into the “tubuli recti,” which are a set of short, straight tubules. The tubuli recti empty into the tubular network known as “rete testis.”

Efferent ductules connect the rete testis with the epididymis. The efferent ductules have a ciliated pseudostratified columnar epithelium. From the epididymis, the sperm move through various accessory glands and then released out through the urethra during ejaculation.

The pathway of sperm is given below:

After ejaculation, sperm can reach the uterine tube in about 30 minutes or less, but it takes 10 hours for it to fertilize an ovum. The semen contains inhibitory factors, which prevent the immediate fertilization of the ovum.

Before fertilization the sperm must undergo capacitation, which makes the penetration of egg possible. This occurs as the inhibitory factors in the semen are diluted by the female reproductive tract fluids.

The “acrosome” of sperm cell contain several enzymes, which help the sperm to penetrate through the corona radiata (a layer present around the oocyte), and zona pellucida (a glycoprotein layer present in between the plasma membrane of the oocyte and corona radiata). During this process, several sperms move ahead of the sperm that actually fertilize the egg and help in digesting the path towards the egg.

Secondary oocyte:

These secondary oocytes undergo “meiosis II,” cytoplasmic division of the secondary oocyte results in the formation of an egg or ovum and three polar body, both are haploid (having “n” numbers of chromosomes). The polar body degrades itself, and is not capable of being fertilized.

At the mid of the ovarian cycle, ovaries release the secondary oocyte (ovum) into the peritoneal cavity. This ovum enters into the fallopian tubes of the uterus through the fimbriae. The oocyte enter the fallopain tubes and the fertilization occurs in the fallopian tubes.