The 4 types of sex cells

A description of the types of cells whose function is to enable sexual reproduction.

Humans, like most other animals, are multicellular organisms that perpetuate our species by means of the type of reproduction known as sexual. This type of reproduction, which results in the emergence of individuals with genetic characteristics from two individuals, gives the species a much greater variability than that offered by asexual reproduction.

In order for sexual reproduction to produce a new being, a certain type of cells must fuse together: the sex cells or gametes. It is about these that we are going to talk in this article.

The gametes or sexual cells

The name gametes or sex cells is given to a certain type of cell whose main function is to generate a new being. whose main function is to generate a new being, perpetuating the species and the genes of the progenitors.perpetuating the species and the genes of the progenitors.

The sexual cells present different forms, specifically there are two types whose union will be the one that generates the zygote from which a new individual will develop. The specific name of these cells depends on the type of living being we are talking about, with one being male and the other female.

This type of cell have half the number of chromosomes of those of the species in question.When the new being appears as a result of the union or fusion of two cells from two different individuals, the offspring organism ends up having the same number of chromosomes as its progenitors, although with genetic information different from that of either of the previous ones. After their union, a genetic recombination of the genetic information from both cells takes place, generating a unique genetic code through this recombination.

In the case of the human being, we have a total of 46 chromosomes divided into 23 pairs. Of these, 22 of the pairs correspond to somatic chromosomes and are the same regardless of sex. However, the 23rd pair differs between males and females. the 23rd pair differs between males and femalesThese are the sex chromosomes that mark our genetic sex. Specifically, the male has one X and one Y chromosome, while the female has two X chromosomes.

Sex cells in animals

When we talk about sex or sex cells, the first thing we think of is the type of reproduction and cells that we humans have and that all other animal species also have: sperm and eggs.

Spermatozoa

Spermatozoa are the sex cells of the male gender, which possess half of the genetic information of the male. which possess half of the genetic information needed to form a new living being. necessary to form a new living being. They are a type of cell of very small size, smaller than the female gametes, and are formed in great quantity in the testicles of the males of each species.

For fertilization to occur, it is necessary for the sperm to travel to the egg, of which only one (usually, although there are exceptions) will manage to enter the egg and combine its genetic material with it. That is why the spermatozoon has morphological adaptations that allow such displacement.

Its basic morphology is as follows:

First of all we can observe the existence of a large head (the largest part of the spermatozoon). inside of which we can find the nucleusIn the acrosome, in which the genetic information in question can be found, and the acrosome or layer formed by various enzymes that allow the sperm to enter into the female gametes. In addition to this we can find different substances that allow the sperm to nourish and allow the movement of the sperm.

The other main part is the tail or flagellum, thanks to which the sperm can move inside the female body until it reaches the egg. Inside it we can first find a small neck through which it joins the head, then an intermediate piece in which we can find different mitochondria. different mitochondriaThese allow the production of sufficient energy (through the substances present in the sperm itself as well as in the rest of the semen) and finally the flagellum or final part, which moves to allow movement.

Egg cells

Egg cells are the female sex cells, which carry half of the genetic information necessary for the genesis of a new being. They are a type of large, sphere-shaped cell that is produced by the ovaries of a woman's ovaries. produced by the ovaries of the ovaries of females of different species..

Eggs have the characteristic that they are not always available for fertilization, there is a whole cycle through which an egg is produced, matures, remains available for possible reproduction and is released if it is not fertilized, this being the menstrual cycle. Approximately one is generated every month (in reality, it is usually 28 days).

Also, unlike spermatozoa, which are present in large quantities throughout life, there are only a certain number of them in each female. During the reproduction itself, the egg cell remains immobile until the sperm reaches it and finally penetrates it (if it succeeds).

The structure of this cell is as follows, from the inside out:

First and foremost and in its interior, the nucleus stands out in which the genetic information that would allow the formation of a new being to join a spermatozoon is found. We can also find in its interior the vitellumThe vitellum, a series of substances as an energy reservoir that would allow the survival of the zygote until the formation of a placenta. All this would be surrounded by a plasma membrane that limits the cell and through which chemical elements can enter and leave, allowing its interior to be chemically balanced.

Around the membrane a protective gelatinous layer, called the pellucid layer, can be found.The corona radiata, which acts as protection while allowing the entry of a first spermatozoon and eventually hardens to prevent more than one sperm from entering. A final layer, the outermost, is the corona radiata. This will have special relevance in regulating sex hormones and generating the placenta if fertilization occurs.

Sex cells in plants

Sperm and ova are not the only types of sex cells that exist, being only those of animals. Plants and other plants also have sexual reproduction in many cases.their sex cells being the oosphere and pollen.

The oosphere

The oosphere is the name given to the type of female sex cell of plants that have the capacity to reproduce sexually. This type of cell can be found inside the so-called seminal rudiments, located in the embryonic located in the embryonic sacs of plants, located in the flowers.

Like animal ova, it has half as many chromosomes as the rest of the cells of the progenitor individuals. The pollen or male gamete at the plant level comes into contact with it through the stigma of the flowers.

Pollen

Pollen is the plant equivalent of spermatozoa: the male sex cell of plants. It consists of small particles in the form of grains that are formed in the stamens of plants. It binds to the oosphere in the process known as pollination (for which they need the wind or the help of animals).

These grains, which contain half of the genetic information necessary to produce a new being, enter the stigma and join the oosphere. For this, once in the stigma, the pollen generates a small extension called pollen tube in order to transport its genetic material to the oosphere.