human reproduction

Anatoma

2022

We explain what human reproduction is, intercourse, fertilization and what the male and female reproductive systems are like.

Human reproduction requires two fertile individuals, grown and developed.

What is human reproduction?

Human reproduction is called the set of complex biological and biochemical processes that allows two Humans of different sexes (male and female) conceive a new individual belonging to the species, that is, breed.

For this, human beings have a specialized reproductive system in our bodies, which matures and develops throughout puberty, and which is physically and biochemically different depending on the sex of each individual. Thus, in order to reproduce, it takes two fully developed, fertile, adult human individuals.

As the presence of two well-distinguishable sexes indicates, human reproduction is sexual type: is produced by the union of cells germ of both parents (called gametes: female eggs and male sperm), which have half of the Genetic information of each individual, assigned entirely at random.

These cells are produced in the sexual organs. Thus, when put together, the two halves create a totally new, unique and unrepeatable genetic information or genome, which will be that of the new member of the species.

From that moment on, the new human being grows inside the womb, until it has developed enough to start living independently. It is then expelled from the uterus through the birth canal, in what we commonly know as being born.

The stages of human reproduction are: intercourse, fertilization, pregnancy and childbirth. We will see them separately later.

Male reproductive system

The reproductive system matures and develops throughout puberty.

The male members of the human species have a reproductive system composed of the following organs:

  • Penis. A cylindrical and external organ, erectile in nature, that is, it can be flooded with blood and expand its size several times, until obtaining a hard consistency, ideal for entering the vagina, in what we know as penetration. Its mission will be to deposit the sex cells there, so that fertilization can take place.
  • The testicles. Two large glands located below the penis, also on the outside of the body, and connected to it by a series of tubes. In them, the sex cells, the sperm, are produced, which are very active cells and endowed with a flagellum, that is, a tail for swimming. In addition, testosterone is produced in the testicles, the male hormone that, during puberty, triggers the physical and organic changes necessary for the body of men to mature sexually. As if that were not enough, that same hormone is responsible for male sexual desire.
  • The prostate A gland the size of a walnut, located very close to the bladder in the body of men, whose function is to produce the different compounds that constitute semen, a whitish liquid, a mixture of substances biochemical, in which the sperm travel and from which they take everything necessary for their nutrition and sustenance.
  • The seminal vesicles. Also called seminal glands, they are located above the prostate, to which they are attached, and are responsible for producing about 60% of the fluid that makes up semen, called seminal fluid.
  • The seminal ducts and urethra. Which are the tubes that connect everything and allow, when the time comes, the semen full of sperm to flow out through the urethra, culminating in the tip of the penis.

Female reproductive system

The feminine and masculine apparatus are physically and biochemically distinct

For its part, the reproductive system of women is also made up of several organs, all internal unlike men. We refer to:

  • The labia majora and minora. What are the folds of skin and mucosa visible to the naked eye from the outside, covering and protecting the entrance to the vagina and the woman's body.
  • The clitoris. Whose head or glans is located between the lips in the upper part of the vulva, it is an organ whose sole function is to provide sexual pleasure to women. It has thousands of nerve endings and runs along the labia majora, the perineum, and the lower third of the vagina.
  • The vagina It is the passage that connects the exterior of the female body with the entrance of the uterus. It is a muscular region, normally narrow, whose function is to receive the penis and communicate the discharge of semen to the internal regions where fertilization occurs.
  • The cervix. It is the entry point from the vagina to the uterus, located at the end of the vagina.It is a flexible, thin region, about an inch in length or so.
  • The uterus. Also called the womb, it is the space where fertilization occurs and the zygote attaches itself to the walls, to give way to the development of an embryo, that is, of what will later be a baby. It is covered by the endometrium, its inner mucosa, which is renewed month by month, thus giving rise to menstruation. The uterus is made up mostly of muscles, is roughly pear-shaped, and its size changes as more space is required to house the fetus during pregnancy.
  • The ovaries. That there are two, located one on each side of the uterus, would come to be the female equivalent of the testicles: they generate the sex hormones that allow development (estrogen and progesterone, in particular) and also the sex cells that are found with the male inside the uterus, the ovules. An egg is released from the ovaries every month and descends into the uterus, where it may or may not be fertilized, and therefore may become a zygote or may be shed with menstruation.
  • The fallopian tubes. Also arranged in pairs, are the ducts that connect the ovaries and the uterus, through which an ovum descends each month.

Intercourse and fertilization

The encounter between a man and a woman to start the reproductive process is called intercourse or sexual intercourse. Both individuals must be in a state of sexual arousal: the penis must be erect and the vagina lubricated, for penetration to occur easily and painlessly.

There, a series of movements are produced that stimulate the abundant nerves of each sexual organ, leading to climax and orgasm, which is a set of intense sensations of pleasure. During orgasm, semen is expelled from the man's body, producing ejaculation.

In the semen, the spermatozoa travel, which, helped by the vaginal contractions of the climax, enter the uterus and are received by the ovum, expectant. Only one of the millions of them that are in a single ejaculation enters the interior of the ovum and thus fertilization occurs, which is the beginning of reproduction.

Eventually, the same egg can be fertilized by two sperm, thus producing a twin pregnancy.

Pregnancy

In pregnancy the zygote becomes an embryo and then a fetus.

Pregnancy is the stage during which the fertilized egg, now called the zygote, begins to grow. From the beginning it is subdivided vertiginously, going through different stages of complexity, such as the morula, blastula or gastrula, through continuous processes of mitosis.

Eventually the set of cells is sufficient to initiate a delicate process of specialization, until an embryo is formed, that is, a potential human being.

Embryos are made up of three layers of cells: endoderm, ectoderm and mesoderm, each of which will give rise to different parts of the human body of the new individual throughout the nine months of pregnancy.

During this entire stage, menstruation of the female body is suspended and the bulging of her belly begins, as more and more space is required for the embryo, which from a certain moment will already have a defined human shape and will be called fetus. .

Throughout this process, the embryo is kept alive by the maternal body, through the umbilical cord. This affects the metabolism mother and, as the pregnancy approaches term, prepares her body for childbirth and to initiate lactation, filling the breasts with milk with which to nourish the newborn.

Birth

Pregnancy ideally culminates with delivery: the expulsion of the newborn through the birth canal, that is, through the vagina, which is capable of widening and rearranging itself to allow passage.

This process can be more or less painful, and more or less fast, and culminates with the baby leaving and later the sac that wrapped it inside the uterus, called the placenta. Once the umbilical cord has been cut, the new human being will have taken the first step towards an independent and totally new life, outside the maternal body.

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