Gamete

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A gamete is another word for a reproductive cell. A gamete can either be a Sperm cell in males, or an Ovum , also known as an Egg cell, in females. Gametes are Haploid cells, meaning they only contain 23 chromosomes, compared to Somatic cells , which contain a full set of 46 chromosomes. When a Sperm cell and Ovum join during Fertilisation , they form a Zygote . The zygote is a combination of the two haploid cells, making it a Diploid cell, therefore providing it with a full set of 46 chromosomes[1]. Following the days after fertilisation, the zygote rapidly divides. Approximately 2 weeks of constant cell division after fertilisation, the zygote is then classed as an Embryo[2].

Structure and Function of a Sperm

The male gamete's main function is to move towards the ovum, by rotation of the Flagella , and fuse with the ovum via the Acrosome Reaction.

The Spermatozoa consists of a head, middle boy, and tail. The head of the spermatozoa contains the haploid nucleus with 23 chromosomes, which is contained by a cytoplasmic layer containing a range of Polysaccharides. The head is key in the Acrosome Reaction as it contains 2 key enzymes; the hyaluronidase and zona acrosin, which are crucial for allowing the sperm to penetrate the ovum[3]. The middle body of the sperm consists of the mitochondrial sheath, which is critical for providing the sperm cell with ATP, used for energy to rotate the flagella for motility[4]. The tail of the sperm is vital for rotating and propelling the sperm, enabling it to travel towards the ovum. The tail is made out of microtubules, which are in a 9+2 arrangement[5].

Screen Shot 2018-10-17 at 18.59.21.png

Figure 1 - Structure of a Sperm[6].

Function of an Ovum

The female ovum, which is significantly larger than the male spermatozoa, also has the same purpose as the spermatozoa; fertilisation. The ovum cannot move like the spermatozoa, since it has no flagella attached. Instead, the ovum contains essential nutrients needed for zygote development into an embryo[7].

References

  1. Wright DB. Human Physiology and Health. Oxford: Heinemann Educational Publishers. 2000:152
  2. Cherry K. The Zygote Phase in Reproduction. 2018 [cited 17/10/18]; Available from: https://www.verywellfamily.com/what-is-a-zygote-2796031
  3. Chavarría ME, Reyes A, Rosado A. The male factor. II. Spermatozoa. Structure and function. 1997 [cited on 17/10/18]; Available at https://www.ncbi.nlm.nih.gov/pubmed/9432472
  4. Sutovsky P, Tengowski MW, Navara CS, Zoran SS, Schatten G. Mitochondrial sheath movement and detachment in mammalian, but not nonmammalian, sperm induced by disulfide bond reduction. 1997 [cited 17/10/18]; Available at https://www.ncbi.nlm.nih.gov/pubmed/9110318
  5. Jain K. Structure, Functions and Types of Mature Sperms in Animals. 2018 [cited 17/10/18]; Available at http://www.biologydiscussion.com/notes/structure-functions-and-types-of-mature-sperm-in-animals-biology/768
  6. Villarreal MR. Sperm. 2006 [cited 17/10/18]; Available at https://en.wikipedia.org/wiki/Sperm
  7. Soffar H. The structure and function of the ovum in the female reproductive system. 2015, [cited on 17/10/18]; Available at https://www.online-sciences.com/the-living-organisms/the-structure-and-function-of-the-ovum-in-the-female-reproductive-system/
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