The Female Reproductive System

How the Organs Function During the Menstrual Cycle

Doctor holding a uterus model

ericsphotography / Getty Images

The female reproductive system is a well-coordinated group of internal and external organs whose purpose it is to prepare for and maintain a normal pregnancy.

External Reproductive Organs

The vulva (derived from the Latin for "covering") consists of the external female sex organs, which include the mons pubis, labia majora, labia minora, clitoris, vestibular bulbs, vaginal opening, and Bartholin's glands, and Skene's vestibular glands. 

Mons Pubis

The mon pubis, also known as the pubic mound, is a mass of fatty tissue surrounding the pubic bone. It contains oil-secreting glands that release substances, called pheromones, that are involved in sexual attraction.

Labia Majora

The labia majora (translated from the Latin for "large lips") are structures that enclose and protect the other external reproductive organs. Each labial "lip" has two surfaces: an outer, pigmented surface covered with pubic hair and an inner, smooth surface populated with oil-secreting sebaceous follicles.

Labia Minora

The labia minora (Latin for "small lips") are smaller structures situated inside the labia majora. They also serve a protective function by surrounding and enclosing the vaginal orifice and urinary orifice (urethra).

Clitoris

The two labia minora "lips" meet at the clitoris, a small and sensitive profusion that is comparable to the penis in men. It is covered with a fold of skin, called the prepuce, which corresponds to the foreskin in men.

As with the penis, the clitoris can become erect with stimulated. Stimulation of the clitoris is a key component of sexual arousal in women.

Vestibular Bulbs

The vestibular bulbs rare two elongated masses of erectile tissue situated on either side of the vaginal opening. During sexual arousal, the bulbs will fill with blood, causing an erection.

The blood inside the erectile tissue is released during orgasm when it is returned to the circulatory system.

Bartholin's and Skein Glands

The Bartholin's glands are two pea-sized glands situated next to the vaginal opening whose role it is to secrete mucus to lubricant the vagina during sex. The Skene's glands serve the same function but are located to the back of the vaginal wall near the lower end of the urethra.

Internal Reproductive Organs

The female internal reproductive organs are composed of the vagina, cervix, uterus, Fallopian tubes, and ovaries.

Vagina

The vagina is an elastic yet muscular canal situated between the urethra and the rectum that is approximately 3.5 to 4 inches in length. The upper part of the vagina connects to the cervix, while the lower part opens to the outside of the body.

During sexual intercourse, the vagina will lengthen, widen, and engorge with blood as it prepares to accept penetration. The vagina also serves as a passageway for cervical mucus, menstrual fluid, and other secretions. During childbirth, the baby is pushed from the uterus through the vaginal canal.

Cervix

The cervix is the lower part of the uterus which connects the uterus to the vagina. It is a small tubular structure that protects the uterus from infection and facilitates the passage of sperm during intercourse. For most of the month, the external opening is covered with thick, sticky mucus that is inhospitable to bacteria.

Around the time of ovulation, the mucus thins and forms watery strands (called spinnbarkeit) that make it easier for sperm to enter the uterus. When pregnancy occurs, the mucus will harden and form a cervical plug that seals the cervical canal and protects the developing fetus until the time of delivery.

Uterus

The uterus, also known as the womb, is a hollow, pear-shaped organ found in women. Situated between the bladder and rectum, the lower end of the uterus opens to the cervix, which then opens to the vagina. The uterus serves many crucial functions in the reproductive process, the most important role of which is housing a developing fetus.

During a normal menstrual cycle, the lining of the uterus, called the endometrium, will thicken with blood in preparation for pregnancy. If a pregnancy does not take place, the lining will be shed during menses.

Fallopian Tubes

Fallopian tubes are the two long, thin tubes that connect to each side of the uterus. The other ends flare open to several long fringes, called fimbriae, that connect to the ovaries.

During ovulation, the fimbriae will start to pulse back and forth to guide the egg into the fallopian tube. Once inside the tube, tiny hairs, called cilia, propel the egg toward the uterus. Fertilization typically occurs in the fallopian tube when the egg encounters a sperm.

Ovaries

The ovaries are a pair of glands about the size and shape of an almond where eggs are stored and the hormone estrogen is manufactured. The ovaries are held in place by several ligaments on either side of the uterus.

In a normal menstrual cycle, the ovaries release an egg every 28 days or so, each of which has the potential for fertilization and pregnancy. The process by which the egg (ovum) is released is called ovulation.

The Menstrual Cycle

During a woman's child-bearing years, the body will typically go through a series of monthly hormonal changes that cause an egg to develop in the ovary as the uterus prepares for a potential pregnancy. 

If pregnancy does not occur, the lining and egg will be removed from the through menses. If pregnancy occurs, the reproductive system will maintain the pregnancy throughout the nine months of gestation.

The average menstrual cycle is around 28 days and occurs in phases. The cycles are directed by four major hormones:

Follicular Phase

During the follicular phase, FSH and LH are released from the brain and travel through the bloodstream to the ovaries. The hormones will stimulate around 20 eggs in the ovaries, each of which is encased in a shell called a follicle.

The release of FSH and LH will also cause estrogen levels to rise. At a certain point, the concentration of estrogen in the blood will switch off the production of FSH. Doing so limits the number of follicles that mature.

Eventually, one follicle will dominate and cause all of the other follicles to stop growing and die.

Ovulatory Phase

The ovulatory phase starts approximately 14 days after the follicular phase has begun. As the rise in estrogen causes FSH production to shut down, it also causes LH levels to increase. The surge in LH will cause the dominant follicle to finally release its egg. This is called ovulation.

As the egg is released, it will be captured by the fimbriae and begin to travel down one of the two Fallopian tubes.

Luteal Phase

The luteal phase starts when the empty follicle turns into a new structure called the corpus luteum, whose role it is to secrete progesterone. Progesterone is the hormone that prepares the uterus to receive a fertilized egg.

If fertilization occurs, the egg will implant in the wall of the uterus, resulting in pregnancy. If it doesn't, the endometrial lining will break down and be shed during menses, and a new menstrual cycle will begin.

Was this page helpful?

Article Sources