Understanding natural conception

The knowledge of the anatomy and the function of the female reproductive system, and the understanding of the process of conception can help us comprehend the causes of subfertility better.

The following information is useful in understanding the process of IVF, the reasons for the use of drugs and the importance of hormone tests and ultrasounds during the treatment cycle.

Terminology of anatomy and physiology



Ovaries


They are the female reproductive glands. There are two ovaries (right and left ovary) and they have a dual function: production of eggs and hormones. They have an almond shape, a size of 30x20x20 mm and are located inside the pelvic cavity, in direct contact with the fallopian tubes. The ovary is a store of follicles (small cysts containing the eggs) of various sizes and developmental stages.

Follicles


Small cysts filled with fluid and sized approximately 8-20 mm, which develop within the ovary and contain the eggs. Each follicle contains a single egg. Their number is estimated to be around 2.000.000 at the time of birth, 300-400.000 at puberty, 25.000 at the age of 38 and 1000 at menopause. Of all the follicles, only about 400 reach the stage of a mature fully grown follicle (Graafian) in the entire duration of a woman?s reproductive life.

Ovulation


The rupture of the mature follicle and the release of the egg. It is triggered by a sudden rise (surge) of the hormone LH.

Oocytes (eggs)


They are the female germ cells (gametes) that always carry the sex chromosome X. They grow and mature within the ovarian follicles, from which they are released at ovulation.

Fallopian tubes


Organs in a shape of slender ducts that connect the uterine cavity with the abdomen. They consist of 4 segments: interstitial, isthmus, ampulla and infundibulum with fimbria. Their inner cavity is the site of fertilization and embryo transport to the uterus.

Uterus


A hollow muscular organ in a shape of a pear, located in the pelvic cavity in which the embryo implants and develops. Also called womb. The two higher ends (horns) contain the uterine openings of the fallopian tubes. The lower end communicates with the cervix.

Cervix


It is the outer end of the uterus, has a cylindrical shape and length of about 4 cm, containing a canal (endocervix). It connects the uterine cavity with the vagina.

Cervical mucus


Secretions of the glands of the endocervix, with varying composition and thickness. It offers a friendly environment for the passage of spermatozoa during the fertile days of the cycle.

Vagina


A fibrous muscular canal with a length of approximately 7.5 cm, which receives the penis during sexual intercourse. The inner end of the vagina, called tholus, communicates with the cervix, while the outer end leads to the opening of the vulva.

Endometrium


It is the tissue (mucosa) lining the inner cavity of the uterus and is discharged along with blood during menstruation (period).

Corpus luteum (yellow body)


A mass of cells that forms from a Graafian follicle after the release of a mature egg at ovulation. It produces mainly progesterone which acts on the endometrium making it receptive to the embryo.

Menstrual cycle


It is the time between the first day of the period (menstruation) and the first day of the next period.

Hypothalamus


The part of the brain that regulates reproductive function by secreting gonadotrophin releasing hormone (GnRH), which acts on the pituitary and triggers the production of gonadotrophins (FSH and LH).

Pituitary (hypophysis)


A small endocrine gland of central importance as it secretes hormones regulating the function of the ovaries, testes, adrenal gland (epinephros), thyroid etc.

Testes


The male reproductive glands. There are two testes (right and left testis) residing in the scrotum, a sac made of skin underneath the penis. The testes have a dual role: production of spermatozoa and hormones.

Semen


Biological fluid of complex composition discharged at ejaculation and containing spermatozoa (comprising 7% of the total volume) and secretions of the prostate, seminal vesicle and other glands.

Spermatozoa


The male germ cells (gametes) that carry either one of the two sex chromosomes (X or Y) and decide the gender of the embryo (female and male respectively). They are produced by the testes and their number normally reaches tens of millions at each ejaculation.

Fertilization


It is the fusion of a spermatozoon with an egg to create an embryo. Fertilization marks the creation of a new organism and decides the gender, depending on the chromosome composition of the gametes: if an egg (X) is fertilised by a ?female? spermatozoon (X) it will give rise to a girl (XX), while if fertilised by a ?male? sperm will result in a boy (XY).