Talk:2010 BGD Practical 3 - Gametogenesis

Original page - http://embryology.med.unsw.edu.au/Medicine/BGDlabfertilization2.htm

Spermatazoa Components

Acroplaxome - forms the acrosome plate with intermediate filament bundles of the marginal ring at the leading edge of the acrosome. (More? review acrosome-acroplaxome-manchette complex)

Acrosome - derived from the Golgi apparatus in conjunction with transient specialized bundles of microtubules (manchette).

Axoneme - the stable mature microtubule-containing tail of the sperm.

Centriole - sperm contains a centriole which in most mammalian species is contributed to reconstitute the zygotic centrosome. In rodents, only a maternal centrosomal inheritance occurs.

Manchette - transient microtubule structure formed in spermatids involved in the process of: assembly of the mammalian sperm tail, mechanical shaping and condensation of the sperm nucleus. These microtubules are aslo ivloved with specific transport, intramanchette transport, which has been likened to intraflagellar transport.

Mitochondria - contained in the initial segment provide the energy for motility and may also enter the egg on fertilization, but are eliminated by a ubiquitin-dependent mechanism.

Perinuclear Theca - located in the sperm head perinuclear region and contains a cytoskeletal element to maintain the shape of the sperm head and functional molecules leading to oocyte activation during fertilization.

Spermatazoa Statistics

The following data is based normal human male values for reproductive ages between 20 to 50 years:

• 45 to 207 million spermatozoa produced per day within the two testes
• 2,000 spermatozoa approx per second each day
• Compare this to adult human red blood cell production of about 250,000 million RBCs per day
• 182 million spermatozoa stored (epididymal reserves) up to per epididymis
• 440 million spermatozoa extragonadal stored
• 225 million extragonadal spermatozoa in the ductuli deferentia and caudae epididymides per ejaculation
• 23 million spermatozoa approx (all animals) per gram testicular parenchyma per day

(Data: Amann RP, Howards SS., 1980 and Gordon-Smith EC., 2007)

Female Oogenesis

Meiosis initiated once in a finite population of cells

1 gamete produced / meiosis

Completion of meiosis delayed for months or years

Meiosis arrested at 1st meiotic prophase and reinitiated in a smaller population of cells

Differentiation of gamete occurs while diploid (in first meiotic prophase)

All chromosomes exhibit equivalent transcription and recombination during meiotic prophase

Male Spermatogenesis

Meiosis initiated continuously in a mitotically dividing stem cell population

4 gametes produced / meiosis

Meiosis completed in days or weeks

Meiosis and differentiation proceed continuously without cell cycle arrest

Differentiation of gamete occurs while haploid (after meiosis ends)

Sex chromosomes excluded from recombination and transcription during first meiotic prophase

References

NCBI Bookshelf - Endocrinology: An Integrated Approach. Nussey, S.S. and Whitehead, S.A. Oxford, UK: BIOS Scientific Publishers, Ltd; 2001. The ovary - folliculogenesis and oogenesis | Spermatogenesis

Mitosis and Meiosis: MBoC Fig 20-6

Oogenesis: MBoC ch20f16.gif

Spermatogenesis: Dev Biol Ch19f18.jpg

Seminiferous Tubule: Dev Biol ch19f17.jpg