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CHAPTER 22: THE REPRODUCTIVE SYSTEMS

IV.ORGANS OF THE MALE REPRODUCTIVE SYSTEM

A.Testes (continued):

4. Spermatogenesis:

See Fig 22.5b, page 885.

a.Males produce sperm from puberty and then throughout life:

b.The sperm is produced in the germinal epithelium of the seminiferous tubules;

c.Sperm cells are produced from spermatogonia cells which contain 23 pairs (or 46) of chromosomes;

d.Meiosis reduces this number by one-half, so that the number of chromosomes in mature sperm cells is 23 chromosomes;

e.Overall sequence:   See Fig 22.5, page 885.

One spermatogonium (23 pairs of chromosomes) duplicates its DNA.  This gives rise to

One primary spermatocyte (23 duplicated pairs of chromosomes) which undergoes meiosis I.  This gives rise to

Two secondary spermatocytes (each with 23 duplicated chromosomes), which undergo meiosis II.  This gives rise to

Four spermatids (each with 23 chromosomes). These cells mature into

Four sperm cells (each with 23 chromosomes).  The sperm cells collect in the lumen of the seminiferous tubule.

f.The sperm travel to, mature, and are stored in the epididymis.

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