Difference Between Spermatogenesis and Oogenesis

The key difference between spermatogenesis and oogenesis is that spermatogenesis is the formation of sperms (male gametes) while oogenesis is the formation of eggs (female gametes).

Both spermatogenesis and oogenesis are commonly referred to as gametogenesis. Gametogenesis is the series of mitotic and meiotic divisions occurring in the gonads, to form gametes. The gamete production is very much different among males and females; thus the production of gametes in males is called spermatogenesis, whereas that of females is called oogenesis.

CONTENTS

1. Overview and Key Difference
2. What is Spermatogenesis 
3. What is Oogenesis
4. Similarities Between Spermatogenesis and Oogenesis
5. Side by Side Comparison – Spermatogenesis vs Oogenesis in Tabular Form
6. Summary

What is Spermatogenesis?

Spermatogenesis is the formation of spermatids (sperm cells) in male testis. The process starts from spermatogonium, which are genetically diploid. Spermatogonia produce primary spermatocyte (diploid) through mitosis. The resultant primary spermatocyte undergoes meiosis I to produce two identical haploid cells called secondary spermatocytes.

Each spermatocyte again divides through meiosis II to form spermatids – two haploid daughter cells. Thus, one primary spermatocyte produces four identical haploid spermatids. It takes about 6 weeks to for spermatids to differentiate into mature spermatozoa.

What is Oogenesis?

Oogenesis is the formation of eggs in females. Usually, the initial stages of oogenesis start during early embryonic stages and complete after puberty. The production of ovum has a cyclic pattern; this usually occurs once in a month.

Oogenesis starts from the diploid oogonium in the ovary. Oogonia produce primary oocytes by mitosis during the early embryonic developmental stages. After puberty, these primary oocytes start to convert to secondary oocytes, which are haploid, during meiosis I. Then during meiosis II, secondary oocyte converts to the ovum, which is also haploid. During both meiosis I and II, the cytoplasm divides unequally, producing two unequal sized cells. The larger cell becomes the ovum while the smaller one becomes the polar body. The secondary oocyte is released from the ovary at ovulation.

What are the Similarities Between Spermatogenesis and Oogenesis?

• Both spermatogenesis and oogenesis start from a diploid cell.
• They result in a haploid cell at the end.
• Both processes are extremely important in sexual reproduction.
• Meiosis occurs in both processes.
• These two processes occur in germ cells.
• Each process has three steps: multiplication, growth, and maturation.

What is the Difference Between Spermatogenesis and Oogenesis?

Spermatogenesis is the formation of sperms (male gametes). It occurs in male testes. In contrast, oogenesis is the formation of egg cells or ova (female gametes). It occurs in ovaries. Spermatogenesis starts from a primary spermatocyte and produces four functional spermatozoa whereas oogenesis starts from a primary oocyte and produces a single ovum. The size of the cells they produce is also another difference between spermatogenesis and oogenesis; sperms are smaller in size whereas ovum is a big cell. Moreover, sperms are motile while ovum is immotile.

Cytogenesis in spermatogenesis results in two equal cells while cytogenesis in oogenesis results in two highly unequal cells. Moreover, the former begins at puberty while the latter begins even before birth. Spermatogenesis involves a short growth phase and occurs continuously after the puberty while oogenesis involves a long growth phase and occurs in a cyclic pattern.

Summary – Spermatogenesis vs Oogenesis

There are two types of gametogenesis: spermatogenesis and oogenesis. Both processes start from a diploid cell and result in haploid cells at the end. The main difference between spermatogenesis and oogenesis stems from the fact that spermatogenesis forms male gametes while oogenesis forms female gametes.

Reference:

1. “Spermatogenesis.” Wikipedia, Wikimedia Foundation, 23 May 2018, Available here.
2. “Oogenesis.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 25 Aug. 2014, Available here.

Image Courtesy:

1.”Figure 28 01 04″ By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
2.”Gray5″ By Henry Vandyke Carter – Modifications: vectorization (CorelDraw). The original can be viewed here: Gray5.png. Modifications made by Mysid (Public Domain) via Commons Wikimedia