Spermatogenesis vs Oogenesis
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. Even though there are meiosis and mitosis, both are present during gametogenesis; the actual formation of gametes begins with the meiosis.
Formation of spermatids (sperm cells) in male testes is referred to as spermatogenesis. The process starts from spermatogonium, which are genetically diploid. Spermatogonia produce primary spermatocyte (diploid) through mitosis. The resulting primary spermatocyte undergoes meiosis I to produce two identical haploid cells called secondary spermatocytes. Each spermatocyte again divides through meiosis II, to form two haploid daughter cells called spermatids. Thus, one primary spermatocyte produces four identical haploid spermatids. It takes about 6 weeks to differentiate spermatid into mature spermatozoa. (Read more on Difference Between Meiosis I and Meiosis II)
Oogenesis is the formation of eggs in females. Usually, the initial stages of oogenesis start during early embryonic stages and completes after puberty. The production of ovum has a cyclic pattern and, usually occurs once in a month. Oogenesis starts from the diploid oogonium in the ovary. Primary oocytes are produced from oogonia by mitosis during the early embryonic developmental stages. After the puberty, these primary oocytes start to convert to secondary oocytes, which are haploid, during the meiosis I. Then during the meiosis II, secondary oocyte converts to 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 polar body. The secondary oocyte is released from the ovary at ovulation.
What is the difference between Spermatogenesis and Oogenesis?
• Spermatogenesis is the production of sperm cells in males, whereas oogenesis is the production of ovum in females.
• In vertebrates, Spermatogenesis occurs in male testes, whereas oogenesis occurs in female ovary.
• Spermatogenesis starts from a primary spermatocyte while oogenesis starts from a primary oocyte.
• Spermatogenesis results four functional spermatozoa from a primary spermatocyte. In contrast, oogenesis results a single ovum and three polar bodies from a primary oocyte.
• In spermatogenesis, cytokinesis results in two equal sized cells while, in oogenesis, it results in two highly unequal cells.
• Sperm cell does not contain any food, unlike the ovum (egg).
• Sperm cells are much smaller than egg.
• Sperm cells are motile, whereas ovum is immotile.
• Spermatogenesis is completed while it’s inside the testis. In contrast, secondary maturation division in oogenesis occurs outside the ovary (it occurs in the oviduct).
• Spermatogenesis begins at puberty, whereas oogenesis begins even before the birth, during the embryonic developmental stages.
• Spermatogenesis results billions of sperm cells at one, whereas oogenesis result only one ovum per month.
• Spermatogenesis involves a short growth phase while oogenesis involves a long one.
• Unlike the spermatogenesis, the process of oogenesis depends on the amount of York stored in the ova in different groups of vertebrates.
• Spermatogenesis occurs continuously after the puberty, whereas oogenesis occurs in a cyclic pattern.
You may also be interested in reading:
Images of Spermatogenesis and Oogenesis: OpenStax College. Human Reproductive Anatomy and Gametogenesis. Connexions. 10 Apr. 2013 <http://cnx.org/content/m44839/1.3/>