In the process of sexual reproduction in living beings, sex cells play a crucial role. These cells, also known as gametes, are responsible for the transmission of genetic information from one generation to the next. In higher organisms, there are four types of sex cells that play specific roles in reproduction. Understanding the nature and function of these gametes is essential to understand reproductive processes and genetic variability in species.
1. Sperm (Spermatozoa)
Spermatozoa are the male sexual cells responsible for fertilization in sexual reproduction. These cells are produced in the testicles through a process known as spermatogenesis. Sperm are highly specialized cells, with an elongated shape and a tail that allows them to move towards the egg to fertilize it.
Each sperm contains half of the genetic information of an individual, since during reproduction it is It will unite with an egg to form a zygote with the full genetic complement. Sperm are released in large quantities during ejaculation and compete with each other to reach and fertilize the egg in the fertilization process.
Sperm structure:
- Head: Contains the nucleus with genetic information.
- Acrosome: Layer that covers the head and contains enzymes to penetrate the egg.
- Neck and middle piece: Connection between the head and tail.
- Tail: Flagellum that provides movement to move towards the ovule.
2. Egg (Oocyte)
The ovum, also known as the oocyte, is the female sexual cell responsible for reproduction. Unlike sperm, eggs are relatively large cells and are specialized in containing nutrients for the development of the embryo if they are fertilized.
During oogenesis, the formation and maturation of the eggs occurs in the ovaries of the female. Eggs contain half of an individual's genetic information and remain inactive until the fertilization process. After union with a sperm, the egg completes its cell division and an embryo is formed with the complete genetic makeup.
Structure of the egg:
- Plasma membrane : External envelope that protects and regulates the entry of substances.
- Cytoplasm: Contains organelles and nutrients for embryonic development.
- Nucleus (haploid nucleus): Stores the genetic material of the egg.
- Nutrient reserve: Accumulation of substances to support the first stages of embryonic development. li>
3. Primordial Germ Cells
Before the formation of mature gametes (sperm and eggs), there is a type of fundamental precursor sex cell known as a primordial germ cell. These cells are found in the germ line and are responsible for the generation of gametes during embryonic development.
Primordial germ cells are the precursors of both sperm in males and eggs in females. . During embryogenesis, these cells undergo cell divisions and migrations to colonize gonadotrophs, where they will give rise to mature gametes at puberty.
Characteristics of primordial germ cells:
- Pluripotency: Ability to differentiate into multiple specialized cell types.
- Migration: Movement towards the gonads for the formation of gametes.
- Cell division: Proliferation and differentiation to generate sperm and eggs.
- Inactivity in childhood: Primordial germ cells remain inactive until stage of sexual development.
4. Somatic Cells
In contrast to sexual cells, somatic cells are those that make up the tissues and organs of the body, and do not participate directly in reproduction. These cells are not gametes and do not contribute to the formation of new individuals, but they are essential for the functioning and structure of multicellular organisms.
Somatic cells divide by mitosis, duplicating their genetic information and producing new ones. cells for the growth, maintenance and repair of tissues. Unlike gametes, somatic cells possess the complete genetic makeup of an individual and are not involved in the transmission of genetic information to offspring.
Functions of somatic cells:
- Growth: Cell division for the development and growth of organisms.
- Tissue repair: Cell regeneration to heal and maintain tissue functioning.
- Organ maintenance: Support and function of body systems and structures.
- Aging: Accumulation of genetic and degenerative damage over time.