11.4 Reproduction Gametogenisis I. Spermatogenesis- the production of

11.4 Reproduction Gametogenisis I. Spermatogenesis- the production of male gametes.

A. Structure: 1. The testes are located outside of the body in the scrotum to provide a cooler temperature for sperm production.

2. The site of spermatogenesis in the testis are the many tiny convoluted seminiferous tubules. (about 250 meters)

3. Each seminiferous tubule is bounded by a basement membrane and layer of smooth muscle that are responsible for the peristaltic

movements of the tubule. 4. In the center of the tubule is a fluid filled lumen containing immature sperm called SPERMATAZOA.

5. The walls of the tubule are made up of sperm cells at different stages of development and specialized nurse cells called SERTOLI CELLS that

provide nutrition for the developing SPERMATAZOA. 6. LEYDIG CELLS (Interstitial

Cells) are found in between the tubules and is responsible for TESTOSTERONE production. B. Process of Spermatogenesis: 1. Near the outer wall of the

seminiferous tubules are diploid (2n) germinal epithelium cells called SPERMATAGONIUM (s) that are undergoing MITOSIS Mitosis- Sperm production begins at

puberty and continues through out life. Mitosis makes an endless supply of diploid (46 chromosomes) cells for sperm production.

2. MITOSIS produces many copies of SPEMATAGONIA (pl). Some increase significantly in size and are now called PRIMARY SPERMATOCYTES that will enter MEIOSIS.

Meiosis- is a reduction division process that reduces the number of chromosomes in half by doing two sets of divisions (Meiosis I and

Meiosis II) producing 4 gametes. Meiosis Animation http://w

ww.you tube.co m/watc h?v=k2 kclHg0

ohU 3. These cells will undergo Meiosis I which will result in two daughter cells with half the number of chromosomes (haploid= 23) called SECONDARY

SPERMATOCYTES. 4. The two SECONDARY SPERMATOCYTES enter into MEIOSIS II forming 4 SPERMATIDS with half of

the number of chromosomes. Pair up the appropriate label and annotation:

5. Once MEIOSIS is completed the SPERMATIDS must differentiate into a fully functioning SPERMATAZOA. a. Head- contains the nucleus and the ACROSOMEorganelle that contains hydrolytic or digestive enzymes to penetrate the egg.

b. Midpiece- with helical mitochondria for ATP production. c. Flagella- whip- like tail made up of microtubules used for motility.

Label: 6. The developing sperm cells need nutrients during

this period of differentiation and attaches to the specialized nurse cells called

SERTOLI CELLS. 7. Each of the stages of meiosis have moved the resulting cells closer to the fluid filled lumen of the seminiferous tubule.

8. The SPERMATIDS are swept up into the EPIDIDYMIS where they will be stored. C. Hormonal Control of

1. LH (secreted by Spermatogenesispituitary) stimulates LEYDIG cells to produce testosterone. 2. FSH (secreted by

pituitary) stimulate the meiotic division of primary spermatocytes into secondary

spermatocytes. 3.TestosteroneDevelopment of secondary spermatocytes into mature sperm.

SUMMARY: Semen production Maturing sperm are passed onto a

long coiled tube, the EPIDIDYMIS (upper rear part of each testis) where they further mature, become motile, and are stored until ejaculation.

( about 20 days) (About 400 MILLION sperm produced each day.)

Exocrine glands produce secretions for the transport of sperm called SEMEN. a. SEMINAL VESSICLE- provides a

sugar (fructose) rich fluid used to nourish the sperm and provide energy and mucus for protection. b. PROSTATE GLAND - alkalineneutralizes acidic environment of female.

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