Human Reproduction: From Puberty to Parenthood

Posted on Dec 8, 2024 in Biology

The Reproduction of Human Beings

Humans reproduce sexually. Women produce ovules, and men produce sperm. These two cells unite to form a zygote. Fertilization is internal, so we are viviparous. Reproduction includes:

  • Production of gametes (in specialized organs)
  • Fertilization (the union of gametes within the female reproductive system)
  • Development of the zygote (within the female reproductive system. The zygote becomes an embryo and then a fetus)
  • Labor and birth (of a fully formed baby)
  • Child Development (Maturation of their sexual organs and transformation of the child into an adult capable of producing gametes and reproducing)

Children

A baby has already formed his reproductive system: the penis and scrotum in children and the vulva in girls. These are the primary sexual characteristics.

Puberty

Puberty occurs between 10 and 14 years of age. In girls, menarche occurs, and in children, sperm production begins. At maturity, the reproductive organs begin to produce hormones, which cause the appearance of secondary sexual characteristics. In girls, breasts grow, hips widen, and pubic and armpit hair appears. In boys, bone and muscle mass increases, the voice becomes deeper, and a beard appears, as well as pubic and armpit hair.

Adolescence

The process takes between two and five years. During this time, individuals feel the need for independence.

Adulthood

After adolescence, individuals reach adulthood at around 20 to 25 years of age. In rural societies, it is not unusual for women to have children before they are adults. In our society, it does not happen often. Teenagers do not usually have children and spend more years acquiring an education.

Female Gametes: The Ovules

When a girl is born, her ovaries contain about 400,000 cells that will eventually begin to mature into eggs. The egg is the female gamete or reproductive cell. It matures in the ovary within the Graafian follicle. The follicle opens and releases the egg into the fallopian tube, where it forms a protective coating. The expelled egg remains fertile for 24 hours.

Male Gametes

Sperm are produced in the seminiferous tubules. From there, they move to the epididymis. Sperm are much more numerous and smaller than ovules. Their release occurs through ejaculation, expelling semen, a liquid formed by sperm, lubricating fluid, seminal fluid, and prostatic fluid. Once deposited inside the vagina, they remain alive for between 3 and 5 days, during which fertilization can occur.

Female Reproductive Cycle

The female sex hormones are estrogens and progesterone. Estrogens are produced in the ovaries and are responsible for their development. Estrogen production follows a cycle of about 28 days. After releasing the egg, the Graafian follicle produces progesterone, which induces the growth and maturation of the endometrium. When the progesterone level is highest, it signals the endometrium to stop developing. If fertilization does not occur, the egg dies.

Fertilization

Ovulation occurs 14 days before the arrival of the menstrual period. The egg can only be fertilized for 24 hours after ovulation. Intercourse is the introduction of the penis into the vagina. If the egg and sperm meet, the sperm surround the egg, but only one penetrates the protective layer and inserts its head, after which it sheds its tail. The genetic material of the sperm and egg fuse, completing fertilization. The resulting cell is the zygote.

Beginning of Pregnancy

The embryo develops three major structures:

  • The placenta (an organ that develops in the endometrium and serves as a connection between the mother and the embryo)
  • The umbilical cord (connects the embryo to the placenta and consists of a tube through which three blood vessels run)
  • The amniotic sac (a sac filled with amniotic fluid, within which the embryo remains)

Development of Pregnancy

Gestation, or pregnancy, is the process that begins with fertilization and ends with delivery. It involves changes. What began as a single cell, the zygote, becomes an embryo, then a fetus, and finally a human being. The process takes about nine months, starting from the beginning of the last menstrual period. The mother undergoes significant changes during pregnancy.

The Birth

The baby is expelled, already formed, through the vagina. Labor has three stages:

  • Dilation: The cervix begins to dilate, increasing in diameter. The muscles of the vagina relax and expand. The muscles of the uterus begin to contract rhythmically. The amniotic sac breaks, and the amniotic fluid, which is 3 to 5 liters of clear liquid, is released (breaking waters).
  • Expulsion: The fetus is pushed out by the contractions of the uterus and the force exerted by the mother pushing with the diaphragm. It exits through the cervix and vagina, which are maximally dilated. The baby’s umbilical cord is cut, and the scar forms the navel.
  • Delivery: 5 to 15 minutes after expulsion, the placenta is expelled, along with the remains of the endometrium.

Infertility

Infertility is the inability to bear children. Its cause may be in the man, the woman, or both.

In Men

  • Production of an insufficient number of spermatozoa.
  • Production of immature sperm with low mobility, or malformed sperm that cannot fertilize the egg.
  • Disorders that prevent the passage of sperm, such as inflammation of the vas deferens.

In Women

  • Blockages in the fallopian tubes.
  • Lack of ovulation due to hormonal imbalances, malnutrition, or other health problems.
  • Difficulty of zygote implantation in the endometrium, which means that even if fertilization occurs, the embryo does not develop.

Assisted Reproductive Techniques

  • Artificial Insemination: It is used when infertility is due to the inability of sperm to fertilize the egg. Semen is artificially introduced into the uterus of a woman when she is ovulating.
  • In Vitro Fertilization (IVF): Used primarily when women have problems with ovulation or implantation of the embryo. The woman is subjected to a hormone treatment to produce several eggs, which are extracted and fertilized with sperm in the laboratory. When the zygote begins to divide, several are implanted in the mother’s uterus.

Contraceptive Methods

  • Natural: Ogino, basal temperature, and observation of cervical mucus (These are different ways to detect the day of ovulation, to abstain from sex from 5 days before until five days later. They are unsafe methods because the date of ovulation may vary)
  • Mechanical:
    • Male condom (elastic and thin rubber cover that is placed over the penis, collecting the semen)
    • Female Condom (elastic, thin rubber sheath that is inserted into the vagina)
    • Diaphragm (rubber ring that is placed in the cervix, blocking the way to sperm)
    • Intrauterine device (IUD) (piece of plastic or metal that the gynecologist places in the uterus, preventing nidation of the zygote)
  • Chemical:
    • Spermicides (creams, gels, or suppositories that are placed in the vagina and kill sperm)
    • Birth control pills (hormone pills that prevent ovulation)
  • Surgical:
    • Tubal ligation (fallopian tubes are divided and sewn, preventing the passage of the egg and the arrival of sperm)
    • Vasectomy (vas deferens are sectioned and sewn, preventing the release of sperm)

Sexuality and Gender

Sexuality is the set of anatomical, physiological, and psychological conditions that characterize each sex and represents a series of emotional and behavioral phenomena related to sex, which mark human beings throughout their development and their role in society. Sex is a biological condition that distinguishes between male and female individuals. A sexual relationship is sexual contact between people, driven by attraction or sexual impulse.

Healthy Habits Concerning Sexuality

  • Wash frequently.
  • Use a condom.
  • Avoid promiscuity.
  • Avoid derogatory attitudes towards your partner.
  • Find a trusted adult partner to whom you can ask your questions.
  • Go to the doctor regularly or if you notice any unusual symptoms that worry you.
  • Ignore the advice of uninformed individuals.