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11.1.3. The female reproductive system

The female reproductive system

The function of the female reproductive system is to create the ovum, the female gamete, the sex cell with 23 chromosomes that will contain the maternal DNA that will contribute to the new individual. In addition, it secretes hormones that regulate female sexual characteristics and the development of the embryo and childbirth.

Parts of the female reproductive system

The parts of the female reproductive system are:

Aparato reproductor femenino

By KES47 (File:Scheme female reproductive system-en.svg) [Public domain], via Wikimedia Commons

Aparato reproductor femenino

By Bibi Saint-Pol [CC BY-SA 3.0], via Wikimedia Commons

  • The ovaries. They are the female gonads, about the size of an almond, and are housed in the abdomen. Inside are circular structures, the ovarian follicles, which contain the ovules (female gametes). The eggs are released one by one every 28 days or so.

The ovaries also secrete the female sex hormones responsible for the secondary sexual characteristics of women and the regulation of the ovarian cycle.

  • The fallopian tubes or oviducts. They are two tubes that connect the ovaries  to the uterusThey are responsible for carrying the egg to the uterus. This is where fertilization occurs, that is, the union of an egg with a sperm.
  • The uterus or womb. It is the muscular cavity into which the fallopian tubes flow, it houses the zygote or fertilized ovum and is the place where the embryo develops during pregnancy.

The internal part of the uterus is covered by a mucosa, the endometrium, formed by highly vascularized tissue whose function is to nourish the embryo. If fertilization does not occur, the endometrium is expelled, leading to menstruation.

In the lower part, the cervix or cervix, the uterus narrows and communicates with the vagina.

  • The vagina. It is the elastic duct, with muscular walls lined by a mucosa, which communicates the uterus with the outside, welcomes the male penis and where the semen is deposited. It is the copulatory organ and the conduit through which the fetus exits during childbirth.

It has glands that secrete lubricating substances to facilitate the introduction of the penis. At the entrance to the vagina there is a small incomplete membrane called the hymen that usually breaks during the first sexual intercourse.

  • The vulva. It is the external genital organ, formed by two folds of skin called the labia majora and minora that cover the vaginal opening and the urinary meatus.

At the top, where the labia minora meet, is the clitoris, a small, very sensitive erectile organ with many nerve endings.

The Bartholin's glands, located on both sides of the vaginal opening, produce fluids that lubricate the vagina to facilitate copulation.

  • The mammary glands. They are responsible for producing milk that will serve as food when the baby is born .

vulva

By OpenStax College;CFCF, Turdas, and myself (Figure_28_02_02.jpg) [CC BY-SA 3.0], via Wikimedia Commons

Physiology of the female reproductive system

Unlike male gametes, future female gametes are present from the fetus. Before birth, a woman already has about 400,000 oocytes (enveloped by their corresponding follicles) of which only about 450 will mature after puberty. The fertile life of women begins with the first menstruation or menarche and ends when the eggs stop maturing, around the age of 50, with menopause.

The gametogenesis is the process of formation and maturation of gametes, which in the case of the female gamete, called oogenesis. It begins in the embryonic stage, stops, and until puberty does not begin to mature the eggs , which will stop maturing at the end of fertile life.

The following scheme represents oogenesis.

En la ovogénesis, de una ovogonia de 46 cromosomas se obtiene un óvulo de 23 cromosomas
Henry Vandyke Carter [Public domain], via Wikimedia Commons

The 46-chromosome oogonia divide by meiosis to form ovules with 23 chromosomes. Thus, when fertilized by sperm, the zygote will have 46 chromosomes, the same chromosomal endowment as the rest of the body's cells.

The oogenesis differs from spermatogenesis in several respects:

  • It does not occur constantly, but discontinuously.
  • The ovules mature from puberty, with menarche, until menopause. Sperm begin to mature at puberty and throughout life.
  • Four spermatozoa are obtained from each spermatogonia, while only one ovum is produced from each oogonia.

When ovulation occurs, the egg leaves the ovary into the fallopian tubes and the uterus prepares to host the fertilized egg. If fertilization has not occurred , the egg and uterine lining that had been prepared will be destroyed and shed, in a process known as the menstrual cycle.

The endocrine system is responsible for regulating this process. The ovaries, in turn, also function as endocrine glands and secrete hormones.

Activity: Physiology of the female reproductive system.