Maturation of Sperm Begins at Puberty

Spermatogenesis, which begins at puberty, includes all of the events by which spermatogonia are transformed into spermatozoa. At birth, germ cells in the male can be recognized in the sex cords of the testis as large, pale cells surrounded by supporting cells (Fig. 1.21 A). Supporting cells, which are derived from the surface epithelium of the gland in the same manner as follicular cells, become sustentacular cells, or Sertoli cells (Fig. 1.21 C).

Shortly before puberty, the sex cords acquire a lumen and become the seminiferous tubules. At about the same time, primordial germ cells give rise to spermatogonial stem cells. At regular intervals, cells emerge from this stem cell population to form type A spermatogonia, and their production marks the initiation of spermatogenesis. Type A cells undergo a limited number of mitotic divisions to form a clone of cells. The last cell division produces type B spermatogonia, which then divide to form primary spermatocytes (Figs. 1.21 and 1.22). Primary spermatocytes then enter a prolonged

Spermatagonia Germ Cell
Figure 1.21 A. Cross section through primitive sex cords of a newborn boy showing primordial germ cells and supporting cells. B and C. Two segments of a seminiferous tubule in transverse section. Note the different stages of spermatogenesis.
Spermatocytes

Spermatids

Type A dark spermatogonia

Type A pale spermatogonia

Type A pale spermatogonia

Type A pale spermatogonia

Type A pale spermatogonia

Type B

spermatogonia

Primary spermatocytes

Secondary spermatocytes

Spermatids

Figure 1.22 Type A spermatogonia, derived from the spermatogonia! stem cell population, represent the first cells in the process of spermatogenesis. Clones of cells are established and cytoplasmic bridges join cells in each succeeding division until individual sperm are separated from residual bodies. In fact, the number of individual interconnected cells is considerably greater than depicted in this figure.

Figure 1.22 Type A spermatogonia, derived from the spermatogonia! stem cell population, represent the first cells in the process of spermatogenesis. Clones of cells are established and cytoplasmic bridges join cells in each succeeding division until individual sperm are separated from residual bodies. In fact, the number of individual interconnected cells is considerably greater than depicted in this figure.

Type B spermatogonium

Resting primary spermatocyte

Secondary spermatocyte

Hair Loss Prevention

Hair Loss Prevention

The best start to preventing hair loss is understanding the basics of hair what it is, how it grows, what system malfunctions can cause it to stop growing. And this ebook will cover the bases for you. Note that the contents here are not presented from a medical practitioner, and that any and all dietary and medical planning should be made under the guidance of your own medical and health practitioners. This content only presents overviews of hair loss prevention research for educational purposes and does not replace medical advice from a professional physician.

Get My Free Ebook


Post a comment