Introduction

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The Primary Organs and Structures in the Reproductive System. The primary structures in the reproductive system are as follows:

• The uterus is a pear-shaped organ located between the bladder and lower intestine. It consists of two parts, the body and the cervix.
• When a woman is not pregnant the body of the uterus is about the size of a fist, with its walls collapsed and flattened against each other. During pregnancy the walls of the uterus are pushed apart as the fetus grows.
• The cervix is the lower portion of the uterus. It has a canal opening into the vagina with an opening called the os, which allows menstrual blood to flow out of the uterus into the vagina.
• Leading off each side of the body of the uterus are two tubes known as the fallopian tubes. Near the end of each tube is an ovary.
• Ovaries are egg-producing organs that hold between 200,000 and 400,000 follicles (from folliculus, meaning "sack" in Latin). These cellular sacks contain the materials needed to produce ripened eggs, or ova.
• The inner lining of the uterus is called the endometrium.  During pregnancy it thickens and becomes enriched with blood vessels, which house and support the growing fetus. If pregnancy does not occur, the endometrium is shed as part of the menstrual flow. Menstrual flow also consists of blood and mucus from the cervix and vagina.

The uterus is a hollow muscular organ located in the female pelvis between the bladder and rectum. The ovaries produce the eggs that travel through the fallopian tubes. Once the egg has left the ovary it can be fertilized and implant itself in the lining of the uterus. The main function of the uterus is to nourish the developing fetus prior to birth.