Elements of anatomy and physiology

In order to appreciate why we use drugs during IVF treatment, it is useful to know the basics of reproductive tract anatomy and physiology, as well as the basics of reproduction. Please see below some basic facts in the form of a dictionary.

The ovaries
They are two and they have a dual function. They produce eggs and hormones. They are almond shaped, 2x2x2 cm in size, they are located in the abdomen and they come in contact with the fallopian tubes. The ovary is a pool of follicles (small cysts that contain the eggs) in various sizes and stages of development.

The follicles
Small cysts, about 8-20 mm in size, filled with fluid, that grow in the ovaries and contain the eggs. Their number is estimated to be around 2,000,000 at birth, 300-400,000 during adolescence, 25,000 at the age of 38 years and 1,000 at menopause. Out of these, only about 400 reach the stage of a mature (Graafian) follicle during the entire duration of the reproductive cycle of a woman.

Ovulation
It is the rupture of the "mature" follicle and the release of the egg. It is caused by the sudden rise (surge) in LH.

The oocytes
They are the female reproductive cells (gametes) that carry the X sex chromosome. They are located and grow inside the follicles out of which they are released with ovulation. The mature "oocyte" has a structure called the first polar body and is surrounded by the zona pellucida. The oocyte is also known as the ovum or the egg.

The Fallopian tubes
The fallopian tubes (also known as oviducts or salpinges) are organs in the shape of a long tubule that connect the uterine cavity with that of the abdomen. They are 4 parts of the fallopian tube from the uterus to the ovary: the isthmus, the ampulla (where fertilization takes place), the infundibulum and the fimbria anchored to the bell shaped end of the tube. The fallopian tubes are also responsible for the transfer of the embryo to the uterine cavity.

The uterus
The uterus (or womb) is a hollow, muscular, pear shaped organ. The uterine cavity is where the embryo develops until birth. Into its upper corners the uterine tubes open, one on either side, while below, its cavity communicates with that of the vagina through the cervical canal.

The cervix
It is the lower, narrow part of the uterus. It is cylindrical in shape, about 4 cm in length with an endocervical canal that protrudes through the upper anterior vaginal wall and connects the uterine cavity with the vagina.

Cervical mucus
Secretion of the endocervical glands with content and viscosity that varies throughout the menstrual cycle, which is during the fertile days is the pathway of the spermatozoa to the egg.

The vagina
It is a fibromuscular tubular tract about 7.5 cm in length that receives the penis during intercourse. The cervical canal protrudes in the upper part of the vagina, called the upper anterior vaginal wall, and the lower part of the vagina leads to the external female genitalia.

The endometrium
It is the normal tissue lining of the uterine cavity and is shed along with blood as the menstrual period.

The corpus luteum
It is the temporary endocrine structure that the follicle differentiates into and fills up with blood after ovulation. It mainly produces progesterone, which acts on the endometrium and prepares it for implantation and pregnancy.

The menstrual cycle
It is the time period between the first day of the menstrual period and the first day of the next period.

The testes
They are two and they have a dual function: they produce spermatozoa and hormones. They are located in the scrotum and which is a dual-chambered protuberance of skin and muscle.

The spermatozoa
They are the male reproductive cells (gametes). From a genetic point of view, they contain one of the two sex chromosomes (X or Y) and they thus determine the sex of an embryo (female or male, respectively). They are produced in the testes (or testicles) and their number is normally tens of millions per ejaculation.

Fertilisation
It is the union of the spermatozoon with the oocyte for the creation of the embryo.

The hypothalamus
Area of the brain that for the purpose of reproduction produces the Gonadotropin Releasing Hormone (GnRH) which acts on the pituitary and causes the secretion of FSH and LH (gonadotropins).

The pituitary
Gland of the brain, of strategic importance, that secretes hormones which regulate the function of the ovaries, the testes, the adrenal glands, the thyroid and other glands.