Fertilization and Pregnancy

Fertilization is the first step in pregnancy. The ovaries are a pair of oval or almond-shaped glands that lie on either side of the uterus and just below the opening to the fallopian tubes. These contain the eggs, also known as ova (singular: ovum). The fallopian tubes lie in the pelvic portion of the abdominal cavity and each tube reaches from an ovary to become the upper part of the uterus. This funnel-shaped tube is about three inches in length; it carries eggs and sperm, and is where...

Anatomy Explorer

Full Fertilization and Pregnancy Description

[Continued from above] . . . fertilization of the egg takes place. The larger end of the funnel is divided into feathery, finger-like projections, which lie close to the ovary. These beating projections, along with muscle contractions, force the ovum down the funnel's small end, which opens into the uterus. After sexual intercourse, sperm swim up this funnel from the uterus. The lining of the tube and its secretions sustain both the egg and the sperm, encouraging fertilization and nourishing the egg until it reaches the uterus.

Fertilization refers to the union of a female ovum (or egg) with the spermatozoa of a male and will initiate the process of sexual division of meiosis.

Conception is the first stage of fetal development; this is when the egg is fertilized and embeds in the uterine wall. Hormonal changes prepare the uterus to nourish the fetus. This stage lasts for about four weeks. During the embryonic stage of development, there are very few noticeable changes in the pregnant woman. The most noticeable change is the cessation of the menstrual cycle. Meanwhile, the embryo begins to develop its major organ systems, including the heart and central nervous system. Near the end of embryonic development, hands and feet begin to form. This stage lasts from about the fourth to the eighth weeks of the pregnancy.

The fetal stage of development begins at the end of the eighth week of development and lasts until birth. During this period, the existing body structure continues to grow and mature in the fetus, in turn, changing the physical and physiological appearance of the mother.

As the fetus grows in size, development and weight, the uterine cavity grows as well to accommodate the changes in size. Although the abdominal and pelvic contents are somewhat compressed during fetal development, very few physiologic changes will occur to the mother's body other than to the uterus and breasts. The pubis symphysis will not stretch until actual delivery and the bladder may not have the volume it had been capable of before fetal development. The rectum and perineum will continue to be relatively unchanged, although the mother may experience increased constipation. Due to the increased weight, a pregnant woman may experience back pain; this is the result of increased curvature of the spine and lack of support of the abdomen. Pregnancy ends with the onset of labor and the successful delivery of the newborn.