Module 3S1 Reproductive Systems

2.3.3S1 page 2

Explore

 

This section is divided into two parts: spermatogenesis—formation of sperm and the structures that support sperm production; and oogenesis—the formation of the ovum and the structures that support its development.

 

Spermatogenesis

 

While women are born with all the eggs they will ever have, men produce sperm on a continual basis. A man’s sperm or gamete development can therefore be affected by what he does daily. Choices a man makes regarding smoking, stress management, nutrition, exercise, and drug and alcohol use contribute to the production and quality of his sperm. Regardless of the choices he makes, the quality of a man’s sperm begins to slowly decline at approximately age 25.

 

In the early stages germ cells or gametes are supported, nurtured, and protected by specialized supporting somatic cells. Mature gametes are produced in a process called gametogenesis and developed in a process called spermatogenesis. Throughout spermatogenesis mature male gametes commonly called sperm are scientifically referred to as spermatozoa. During the stages of development the sperm cells are in close contact with Sertoli cells and interstitial cells.

 

Sertoli cells are found in the testes, within the seminiferous tubules, and are sometimes referred to as nurse cells. They nurture the developing sperm cells by providing secretory and structural support. The Sertoli cells give structural support by acting as a barrier to protect the sperm during their development. Since spermatozoa start development at puberty, the body considers sperm cells to be foreign to the body. If not protected by the Sertoli cells, the body’s immune system would destroy them. By producing the hormone inhibin, Sertoli cells perform a secretory function. Inhibin targets the anterior pituitary and hypothalamus to inhibit the production of follicle stimulating hormone (FSH).

 

Interstitial cells are found in the testes but are not found in the seminiferous tubules. While they are therefore only indirectly linked to sperm production, they do secrete testosterone which targets the entire male body and stimulates the development of the male reproductive system, the secondary male sex characteristics, and spermatogenesis.

 

Read

 

Reread section ”The Testes” on pages 479 and 480 of the textbook. Focus on information about the supporting structures of the gametes.

 

To gain further information, do an Internet search using the search terms “Sertoli cells” and “interstitial cells.”

 

Watch and Listen

 

Watch the section on spermatogenesis in the video to further your understanding of how the structural support tissue helps develop the male gametes. Take notes on the information you learn in this video and save them in your course folder.

 

 

Oogenesis

 

In females, the germ cells or gametes are the egg cells. The process of developing mature egg cells is called oogenesis. Follicle cells are the structural supporting cells that surround and develop the egg.

 

Egg cells begin as oogonia and then develop into primary oocytes. About 700 primary oocytes are formed in the ovaries during fetal development. The primary oocytes stay dormant in the female body until the beginning of puberty. At the onset of puberty some of the primary oocytes will further develop into functioning egg cells, generally at a rate of about one per month. While in the ovary, each primary oocyte is surrounded by follicle cells. Together the primary oocyte and the follicle cells surrounding it are referred to as the primary follicle.

 

Like Sertoli cells, the follicle cells perform a secretory and structural support function for the developing gamete. The follicle cells give structural support by fully surrounding the egg, thereby helping to nourish and protect the primary oocyte. The follicle cells give secretory support by releasing estrogen and some progesterone.

 

When chemically stimulated to do so, the primary follicle helps develop the primary oocyte into a secondary oocyte and then into a fully functioning mature egg or ovum. Ovulation takes place when the fully matured egg is expelled from the ovary.

 

The support of the follicle cells and Sertoli cells help ensure properly formed gametes, which can then combine during fertilization to form an embryo, thus continuing the species.

 

Read

 

Reread section “The Ovaries” on page 482 of the textbook to review the process of oogenesis. This section of the textbook does not present much information on the role of the follicle cells. To gain further information, do an Internet search using the search term “follicle cell.”

 

Watch and Listen

 

Watch the section on oogenesis in the video clip to further your understanding of oogenesis and the role of the follicle cells. Take notes on the information you learn in this video and save them in your course folder.