Spermatogenesis & Oogenesis

Spermatogenesis & Oogenesis

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(​And their overlaps)

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Multiple Choice

What is the name of the process of sperm formation?

• SPERMATOGENESIS

• OOGENESIS

• SPERMATOGONIA

• SPERMATID

Multiple Choice

What is the name of the "MOTHER SPERM"?

• SPERMATOGENESIS

• OOGENESIS

• SPERMATOGONIA

• SPERMATID

Multiple Choice

What is the sequence of cellular division in spermatogenesis?

• MEIOSIS I  $$\rightarrow$$  MITOSIS  $$\rightarrow$$  MEIOSIS II

• MEIOSIS I  $$\rightarrow$$  MEIOSIS II  $$\rightarrow$$  MITOSIS

• MITOSIS  $$\rightarrow$$  MEIOSIS I  $$\rightarrow$$  MEIOSIS II

• Germ cell called spermatogonium (diploid) undergoes mitosis

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• ​Forms two daughter cells (diploid); one recycled as a spermatogonium (not depicted) and the other is a primary spermatocyte

• The primary spermatocyte undergoes meiosis I to form two secondary spermatocytes (diploid)

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• ​Each of the two secondary spermatocytes undergo meiosis II to form a total of four spermatids (haploid)

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• ​Spermatids develop into sperm cells (haploid)

• ​Occurs in the ovaries of a female animal

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• Germ cell called oogonium (diploid) undergoes mitosis to form two daughter cells (diploid)

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• ​One of the cells is recycled as an oogonium; the other becomes a primary oocyte

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• This occurs within the first three months of female life

​(~2 million primary oocytes)

• ​The primary oocyte undergoes meiosis I... kind of

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• ​As prophase I occurs, the process is arrested until menstruation begins (~12 years)

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• ​Beginning at the onset of puberty, a single primary oocyte will undergo meiosis

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• ​This recurs monthly

• ​The result of meiosis I is the formation of two daughter cells

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• ​During the first meiotic division of a primary oocyte, a phenomenon called asymmetric cytokinesis occurs

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• ​Asymmetric cytokinesis is when there is an uneven division of cellular components leaving a large cell and a small cell

Small

Big

• ​The large cell is the secondary oocyte; the small cell is referred to as the primary polar body

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• Polar bodies have no known function... they usually disintegrate but may continue in undergoing meiosis II to form two secondary polar bodies

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• ​The secondary oocyte will undergo meiosis II and, once again, the cytokinesis is asymmetric

• The large cell that results from the division of the secondary oocyte will develop into the ovum (aka the egg)

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• ​The secondary polar bodies will all degenerate

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• ​One egg cell is produced from oogenesis... however the egg is nutritionally rich

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• ​Monthly process.. until menopause (~45-55 y/o)

Many diagrams will show the polar bodies

(​~0.05 mm long)

(​~0.1 mm diam.)

Symmetric cytokinesis

Asymmetric cytokinesis

Four sperm produced

One egg produced