Human Reproduction: Organs and Functions
The Key to Life: Reproduction
Reproduction is a biological process that enables the creation of new organisms, a common feature of all known forms of life. This kind of reproduction occurs between two individuals of different sexes (male and female). Human reproduction uses internal fertilization, and its success depends on the coordinated action of hormones, the nervous system, and the reproductive system. The gonads are the sex organs that produce gametes (oocytes and sperm).
The Male Gamete: Spermatozoon
The spermatozoon is a haploid cell that is the male gamete of animals. Its function is to form a totipotent zygote by fusing its nucleus with that of the female gamete, a phenomenon that will lead subsequently to the embryo and fetus. It consists of a tail, intermediate zone, neck, and head.
The Female Gamete: Ovum (Egg)
Ova are the female sex cells. These cells are large, spherical, and motionless. From puberty, every 28 days or so, an egg ripens in one of the ovaries and passes to one of the fallopian tubes. They are the most voluminous cells of the human body, formed by meiosis in the ovaries, in a process called oogenesis, which is manifested through the regular process of ovulation. The first of two meiotic divisions, which reduces the number of chromosomes, is initiated during embryonic development and is interrupted during prophase. It consists of a nucleus, cytoplasm, and cell membrane.
External Genital Organs of Women
- Vulva: Includes all the external female genital organs and part of the female reproductive tract.
- Labia Majora: Two structures consisting of elongated projections that extend to both sides of the vulva, from the Mount of Venus, then around the lower end of the vagina and fuse together.
- Labia Minora: Also called nymphae, are inside the labia majora, extending from the hood of the clitoris, forming a foreskin, and extend to surround the opening of the urethra, the vagina, and end at the perineal frenulum, a few inches from the anus.
- Urinary Meatus: An opening or channel in the human body. The meatus is the end of the urinary excretory duct, the urethra. Fluids such as urine circulate through this small canal.
- Opening of the Vagina: An almond-shaped area drilled with six holes: the meatus of the urethra, the vaginal opening, the Bartholin’s glands, and the Skene’s paraurethral glands.
Internal Genital Organs of Women
- Vagina: The channel that communicates with the outside; the duct through which sperm enter. Its function is to receive the penis during coitus and provide the output for the baby during delivery.
- Ovaries: Organs producing female gametes or oocytes of varying size depending on the cavity and age. In contrast to the testes, they are located in the abdominal cavity. The process of formation of ova, or female gametes, is called oogenesis and takes place in cavities or follicles whose walls are covered with cells that protect and nourish the egg.
- Uterus: A hollow, muscular organ where a fetus grows. The inner wall of the uterus is the endometrium, which presents monthly cyclical changes related to the effect of hormones produced in the ovary (estrogen).
- Fallopian Tubes: Tubes of 10 to 13 cm that connect the ovaries to the uterus and have the function of carrying the egg until fertilization occurs.
External Genitalia of the Man
- Penis: The male copulatory organ, which is also involved in urinary excretion.
- Scrotum: A set of wrappers that cover and contain the testicles. This sac-shaped area of skin is covered with genital-type hair and has specific characteristics that differentiate it from the skin covering the rest of the body.
- Foreskin: The skin overlying the glans penis. It is also the smaller seed coat that covers the clitoris in women.
- Glans: The end of the penis, specifically the corpus spongiosum, which is its widest point, usually cone-shaped or arrowhead-shaped, sometimes semi-spherical.
- Testes: The male gonads, co-producing sperm and sex hormones (testosterone). These glandular organs are the most important part of the male reproductive system.
Internal Genital Organs of Man
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