spermatogenesis and oogenesis

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What is gametogenesis?

The process of producing gametes (sex cells).

Spermatogenesis

Formation of sperm cells.

Oogenesis

Formation of egg cells.

Where does spermatogenesis occur?

In the seminiferous tubules of the testes.

Support cells in spermatogenesis

Sertoli cells.

Function of Sertoli cells

Nourish, support and protect developing sperm cells.

First cell in spermatogenesis

Spermatogonium (2n).

What does a spermatogonium become?

A primary spermatocyte (2n).

What happens during Meiosis I in spermatogenesis?

A primary spermatocyte divides into two secondary spermatocytes (n).

What happens during Meiosis II in spermatogenesis?

Each secondary spermatocyte divides into two spermatids (n).

Product of spermatid maturation

Spermatozoa (mature sperm).

How many sperm are produced from one primary spermatocyte?

Four functional sperm cells.

How long does spermatogenesis take?

About 72 days.

Length of a sperm cell

About 0.06 mm.

What does the sperm head contain?

A haploid nucleus containing genetic material.

Function of the acrosome

Contains enzymes that help the sperm penetrate the egg.

Function of the midpiece

Contains mitochondria that provide energy.

Function of the tail (flagellum)

Enables movement.

Where does oogenesis occur?

In the ovaries.

When does oogenesis begin?

Before birth.

What are present in the ovaries at birth?

Many primary oocytes.

What surrounds a primary oocyte?

A layer of follicle cells forming a primary follicle.

First cell in oogenesis

Oogonium (2n).

What does an oogonium become?

A primary oocyte (2n).

What happens during Meiosis I in oogenesis?

The primary oocyte divides into a secondary oocyte and a first polar body.

Why is the division unequal in oogenesis?

To keep most of the cytoplasm in the egg cell.

What is produced after Meiosis I?

A large secondary oocyte and a small first polar body.

What stage is the secondary oocyte arrested at?

Metaphase II.

When is Meiosis II completed?

Only if fertilisation occurs.

What happens during Meiosis II?

The secondary oocyte forms an ovum and a second polar body.

Functional gamete produced in oogenesis

One ovum (egg cell).

What happens if fertilisation does not occur?

The secondary oocyte degenerates and dies.

What happens to polar bodies?

They eventually disintegrate.

How many functional gametes are produced from one primary oocyte?

One ovum.

How many functional gametes are produced from one primary spermatocyte?

Four sperm cells.

Spermatogenesis starts when?

At puberty.

Oogenesis starts when?

Before birth.

Site of spermatogenesis

Testes.

Site of oogenesis

Ovaries.

Cytoplasm division in spermatogenesis

Equal division.

Cytoplasm division in oogenesis

Unequal division.

Polar bodies formed in spermatogenesis?

No.

Polar bodies formed in oogenesis?

Yes.

Main purpose of polar bodies

Remove extra chromosomes while preserving cytoplasm for the egg.

Why is the ovum large?

It retains most of the cytoplasm and nutrients needed for early embryonic development.

Key difference between spermatogenesis and oogenesis

Spermatogenesis produces four functional sperm; oogenesis produces one functional ovum and polar bodies.