Anatomy of the Female Reproductive System
I. The Functions of the Female Reproductive System
The female reproductive system provides us several functions that are essential for the female body or reproducing.
o Produces the female egg cells in the ovaries called ova or oocytes.
o Provides a fertilization site for the sperm.
o Produces female sex hormones that maintain the reproductive cycle.
o Produces female sex hormones called estrogen for puberty to occur.
II. The Structures of the Female Reproductive System
The female reproductive system is divided into two parts, the internal structures and the external structures.
The internal organs of the female reproductive system are all located in the lower third of the abdomen. The ovaries store and release eggs, which pass along the fallopian tubes into the uterus. The vagina connects the uterus to the outside of the body.
The visible external organs are collectively known as the vulva and consist of the sexually sensitive clitoris surrounded by folds of skin called the labia, which protect the entrances to the vagina and the urethra. Inside the entrance to the vagina lie the two Bartholin’s glands, which secrete a fluid that contributes to lubrication during intercourse.
III. The Functions of Each Part of the Female Reproductive System
The function of the external female reproductive structures (the genitals) is twofold: To enable sperm to enter the body and to protect the internal genital organs from infectious organisms.
The main external structures of the female reproductive system include:
Labia majora: The labia majora enclose and protect the other external reproductive organs. Literally translated as "large lips," the labia majora are relatively large and fleshy, and are comparable to the scrotum in males. The labia majora contain sweat and oil-secreting glands. After puberty, the labia majora are covered with hair.
Labia minora: Literally translated as "small lips," the labia minora can be very small or up to 2 inches wide. They lie just inside the labia majora, and surround the openings to the vagina (the canal that joins the lower part of the uterus to the outside of the body) and urethra (the tube that carries urine from the bladder to the outside of the body).
Bartholin's glands: These glands are located beside the vaginal opening and produce a fluid (mucus) secretion.
Clitoris: The two labia minora meet at the clitoris, a small, sensitive protrusion that is comparable to the penis in males. The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect.
While the main internal structures of the female reproductive system include:
Vagina: The vagina is a canal that joins the cervix (the lower part of uterus) to the outside of the body. It also is known as the birth canal.
Uterus (Womb): The uterus is a hollow, pear-shaped organ that is the home to a developing fetus. The uterus is divided into two parts: the cervix, which is the lower part that opens into the vagina, and the main body of the uterus, called the corpus. The corpus can easily expand to hold a developing baby. A channel through the cervix allows sperm to enter and menstrual blood to exit.
Ovaries: The ovaries are small, oval-shaped glands that are located on either side of the uterus. The ovaries produce eggs and hormones.
Fallopian tubes: These are narrow tubes that are attached to the upper part of the uterus and serve as tunnels for the ova (egg cells) to travel from the ovaries to the uterus. Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. The fertilized egg then moves to the uterus, where it implants into the lining of the uterine wall.
Physiology of the Female Reproductive System
I. The Menstrual Cycle
Females of reproductive age (beginning anywhere from 11-16 years of age) experience cycles of hormonal activity that repeat at about one-month intervals. Menstru means "monthly"; hence the term menstrual cycle. With every cycle, a woman’s body prepares for a potential pregnancy, whether or not that is the woman’s intention. The term menstruation refers to the periodic shedding of the uterine lining.
It all starts with your endocrine glands because they produce the hormones that determine when you get your period, the amount of menstrual flow and what happens to your reproductive organs. The area of the brain called the hypothalamus connects your nervous and endocrine system by way of the pituitary gland, which also is in the brain, and controls the hormones necessary for reproductive health and your period.
The menstrual cycle is a hormonal driven cycle; day 1 is the first day of your period (bleeding) while day 14 is the approximate day you ovulate and if an egg is not fertilized, hormone levels eventually drop and at about day 25; the egg begins to dissolve and the cycle begins again with the period at about day 30.
When periods (menstruations) come regularly, this is called the menstrual cycle. Having regular menstrual cycles is a sign that important parts of your body are working normally. The menstrual cycle provides important body chemicals, called hormones, to keep you healthy. It also prepares your body for pregnancy each month. A cycle is counted from the first day of one period to the first day of the next period. The average menstrual cycle is 28 days long. Cycles can range anywhere from 21 to 35 days in adults and from 21 to 45 days in young teens.
In the first half of the cycle, levels of estrogen (the "female hormone") start to rise. Estrogen plays an important role in keeping you healthy, especially by helping you to build strong bones and to help keep them strong as you get older. Estrogen also makes the lining of the uterus (womb) grow and thicken. This lining of the womb is a place that will nourish the embryo if a pregnancy occurs. At the same time the lining of the womb is growing, an egg, or ovum, in one of the ovaries starts to mature. At about day 14 of an average 28-day cycle, the egg leaves the ovary. This is called ovulation.
After the egg has left the ovary, it travels through the Fallopian tube to the uterus. Hormone levels rise and help prepare the uterine lining for pregnancy. A woman is most likely to get pregnant during the 3 days before or on the day of ovulation. Keep in mind, women with cycles that are shorter or longer than average may ovulate before or after day 14. A woman becomes pregnant if the egg is fertilized by a man's sperm cell and attaches to the uterine wall. If the egg is not fertilized, it will break apart. Then, hormone levels drop, and the thickened lining of the uterus is shed during the menstrual period.
Menstrual Cycle: Day by Day
o Day 1 starts with the first day of your period. This occurs after hormone levels drop at the end of the previous cycle, signalling blood and tissues lining the uterus (womb) to break down and shed from the body. Bleeding lasts about 5 days.
o Usually by Day 7, bleeding has stopped. Leading up to this time, hormones cause fluid-filled pockets called follicles to develop on the ovaries. Each follicle contains an egg.
o Between Day 7 and 14, one follicle will continue to develop and reach maturity. The lining of the uterus starts to thicken, waiting for a fertilized egg to implant there. The lining is rich in blood and nutrients.
o Around Day 14 (in a 28-day cycle), hormones cause the mature follicle to burst and release an egg from the ovary, a process called ovulation.
o Over the next few days, the egg travels down the fallopian tube towards the uterus. If a sperm unites with the egg here, the fertilized egg will continue down the fallopian tube and attach to the lining of the uterus.
o If the egg is not fertilized, hormone levels will drop around Day 25. This signals the next menstrual cycle to begin. The egg will break apart and be shed with the next period.
II. Hormones
The female reproductive system includes five hormones that are responsible for the development and function of the female reproductive system.
Estrogen
o Estrogen plays a role in the development of secondary sex characteristics. These characteristics appear during puberty. Estrogen helps regulate the menstrual cycle. It promotes rapid growth of cell in the lining of the uterus for preparation for pregnancy.
o There are three types of estrogens: Estradiol, Estriol and Estrone. Estradiol is almost always present in the female reproductive body, responsible for breast development and fat distribution to breasts, hips and legs. Estriol is abundant during pregnancy. Estrone is the least abundant estrogen among the three.
o Estrogen also has non-reproductive functions such as abnormal blood clotting prevention and helps retain calcium in bones to keep them strong.
Progesterone
o Progesterone keeps the uterine lining healthy during pregnancy. It also encourages the growth of milk-producing glands.
Gonadotropin Releasing Hormone (GRH)
o The GRH initiates the monthly hormonal changes and development of a mature egg. It also stimulates the production of FSH and LH.
Follicle Stimulating Hormone (FSH)
o The FSH controls the first half of the menstrual cycle. It is responsible for the stimulation of estrogen and progesterone production during the menstrual cycle.
Luteinizing Hormone (LH)
o The luteinizing hormone controls the second half of the menstrual cycle. It also controls the production of eggs and the menstrual cycle although, it’s difference with the FSH is that the FSH has control over the development of primary sex organs while the LH has no role in the development of primary sex organs.
III. Phases of Menstruation-Follicular, Luteal, and Ovulatory Phase
The day count for menstrual cycle begins on the first day of menstruation when blood starts to come out of the vagina. In this section, the length of menstrual cycle has been assumed to be 28 days (which is the average among women). The entire duration of a menstrual cycle can be divided into four main phases:
1. Menstrual Phase (Day 1 – 5)
The menstrual phase begins on the first day of menstruation and lasts till the fifth day of the menstrual cycle. The following events occur during this phase:
o Two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH) are released from the brain and travel in the blood to the ovaries.
o The hormones stimulate the growth of about 15-20 eggs in the ovaries, each in its own "shell," called a follicle.
o These hormones (FSH and LH) also trigger an increase in the production of the female hormone estrogen.
o As estrogen levels rise, like a switch, it turns off the production of follicle stimulating hormone. This careful balance of hormones allows the body to limit the number of follicles that will prepare eggs to be released.
o As the follicular phase progresses, one follicle in one ovary becomes dominant and continues to mature. This dominant follicle suppresses all of the other follicles in the group. As a result, they stop growing and die. The dominant follicle continues to produce estrogen.
o The uterus sheds its inner lining of soft tissue and blood vessels which then exits the body from the vagina in the form of menstrual fluid. o Blood loss of 10 ml to 80 ml is considered normal.
o Abdominal cramps, which are caused by the contraction of the uterine and the abdominal muscles to expel the menstrual fluid, also occur.
2. Follicular Phase (Day 1 – 13)
This phase also begins on the first day of menstruation, but it lasts till the thirteenth day of the menstrual cycle. The following events occur during this phase:
o Two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH) are released from the brain and travel in the blood to the ovaries.
o The hormones stimulate the growth of about 15-20 eggs in the ovaries, each in its own "shell," called a follicle.
o These hormones (FSH and LH) also trigger an increase in the production of the female hormone estrogen.
o While the egg cell matures, its follicles secretes a hormone that stimulates the uterus to develop a lining of blood vessels and soft tissue called endometrium.
o As estrogen levels rise, like a switch, it turns off the production of follicle-stimulating hormone. This careful balance of hormones allows the body to limit the number of follicles that will prepare eggs to be released.
o As the follicular phase progresses, one follicle in one ovary becomes dominant and continues to mature. This dominant follicle suppresses all of the other follicles in the group. As a result, they stop growing and die. The dominant follicle continues to produce estrogen.
3. Ovulation Phase (Day 14)
The ovulatory phase, or ovulation, starts about 14 days after the follicular phase started. The ovulatory phase is the midpoint of the menstrual cycle, with the next menstrual period starting about 2 weeks later. During this phase, the following events occur:
o The rise in estrogen from the dominant follicle triggers a surge in the amount of luteinizing hormone that is produced by the brain.
o This causes the dominant follicle to release its egg from the ovary. o As the egg is released (a process called ovulation) it is captured by finger-like projections on the end of the fallopian tubes (fimbriae). The fimbriae sweep the egg into the tube.
o Also during this phase, there is an increase in the amount and thickness of mucus produced by the cervix (lower part of the uterus.) If a woman were to have intercourse during this time, the thick mucus captures the man's sperm, nourishes it, and helps it to move towards the egg for fertilization.
4. Luteal Phase (Day 15 – 28)
This phase begins on the fifteenth day and lasts till the end of the cycle. The following events occur during this phase:
o Once it releases its egg, the empty ovarian follicle develops into a new structure called the corpus luteum.
o The corpus luteum secretes the hormones estrogen and progesterone. Progesterone prepares the uterus for a fertilized egg to implant.
o If intercourse has taken place and a man's sperm has fertilized the egg (a process called conception), the fertilized egg (embryo) will travel through the fallopian tube to implant in the uterus. The woman is now considered pregnant.
o If the egg is not fertilized, it disintegrates. The hormone that causes the uterus to retain its endometrium gets used up by the end of the menstrual cycle. This then causes the menstrual phase of the next cycle to begin.
Extra Info about the Female Reproductive System
I. Female Breast Anatomy
The breast is the tissue overlying the chest (pectoral) muscles. Women's breasts are made of specialized tissue that produces milk (glandular tissue) as well as fatty tissue. The amount of fat determines the size of the breast.
The milk-producing part of the breast is organized into 15 to 20 sections, called lobes. Within each lobe are smaller structures, called lobules, where milk is produced. The milk travels through a network of tiny tubes called ducts. The ducts connect and come together into larger ducts, which eventually exit the skin in the nipple. The dark area of skin surrounding the nipple is called the areola.
Connective tissue and ligaments provide support to the breast and give it its shape. Nerves provide sensation to the breast. The breast also contains blood vessels, lymph vessels, and lymph nodes.
II. Breast Development (Tanner Scale)
A breast development of a woman happens in different stages of her life. A human female's breasts develop long before they start to nurse it to their child since this is a vital part of reproduction for humans. Girls follow a defined path to maturity and that path covers a wide range of physical maturity. A wide range of physical maturity could be resulted from genetics, nutrition and other environmental factors, activity levels, stress, additives and other foods.
Tanner Scale of Breast Development
The Tanner scale is a scale of physical development that states the different physical measurements in adolescents based on secondary sex characteristics; such as: size of the breasts, genitalia, development of pubic and axillary hair and etc.
1. Prepubertal (Approx. 8 – 11 years old)
- Breast development starts in the prepubertal stage. Here, the hypothalamus notifies the pituitary to begin balancing the puberty process. This is also when ovaries start to enlarge internally and girls start to have their period.
10
2. Breast bud stage with elevation of breast and papilla; enlargement of Aureoles (Approx. 8 – 14 years old)
- This stage makes the first sign of puberty be physically visible through the further development of the breast. Height and weight also grows same as with the pubic hair.
3. Further enlargement of breast and Aureoles; no separation of their contour (Approx. 9 – 15 years old)
- This stage focuses more on the continuation of the height and weight growth from puberty. Although visible signs are not very much present, hormonal changes internally are being made.
4. Aureoles and papilla form a secondary mound above level of breast (Approx. 10 – 16 years old)
- Stage 4 is when the girl’s menstrual cycle begins along with ovulation. Ovulation does not work the same way to those in the early stages of puberty. Aureoles start to darken and separate into a second mound above the rest of the breast and pubic hairs extend to a more adult triangular pattern.
5. Mature stage: projection of papilla only, related to recession of Aureoles (Approx 12 – 19 years old)
- Stage 5 is when full height is reached, young women are ovulating already, pubic hair is filled and when breasts are fully developed.
III. Benefits of Breast Feeding
Breast milk is milk from a woman’s breast. It is made of nutrients in the mother’s bloodstream and bodily stores. It has an optimal balance of fat sugar, water, and protein that is needed for a baby’s growth and development. Aside from that, it also has longchain polyunsaturated fatty acids which help with normal retinal and neural development.
The act of feeding a baby using breast milk is called breastfeeding, also known as nursing. Breastfeeding begins within the first hour of a baby’s life and continues as often as much as the baby wants. This usually lasts 10 – 15 minutes for each breast.
Many health organizations, including the American Academy of Paediatrics, the World Health Organization, and the American College of Obstetricians and Gynecologists, highly recommend breastfeeding since it has a lot of health benefits, which infant formula lacks, not only to the baby but also to the mother. With that said, the following are some of the benefits of breastfeeding.
Benefits of Breastfeeding to the Mother
1. Better healing post-delivery o Breastfeeding releases the hormone oxytocin, which helps the uterus return to its pre-pregnancy size and may reduce uterine bleeding after birth.
2. Helps in weight loss o Nursing burns extra calories, therefore helping the mother lose pregnancy weight much faster. 3. Delayed return of menstruation and fertility o Breastfeeding causes the release of prolactin, which keeps estrogen and progesterone at bay so ovulation isn’t triggered.
4. Prevention of postpartum depression o Nursing aids maternal physical and emotional heath. Mothers who breastfeed are less likely to obtain postpartum depression.
5. Mothers who breastfeed have lower risks of breast and ovarian cancer, cardiovascular diseases, diabetes, osteoporosis, and rheumatoid arthritis o Breastfeeding can lower the risk premenopausal breast and ovarian cancer. Also, nursing lowers the risk of osteoporosis because a woman’s body absorbs calcium much more efficiently when she is lactating.
Benefits of Breastfeeding to the Baby
1. Babies who are breastfed are more likely to gain the right amount of weight as they grow. o The average breastfed baby doubles its birth weight in 5 to 6 months. Breastfed babies tend to be leaner than formula-fed babies, which improves the former’s long run health.
2. Breastfeeding is linked to higher IQ scores in later childhood. o Studies conclude that breastfeeding is associated to increased cognitive development in childhood.
3. Less hospital trips o Breast milk contains antibodies that would help the baby fight off viruses and bacteria.
4. Breastfed babies have lower risks of allergies, asthma, childhood leukemia, childhood obesity, diarrhea and vomiting, ear infections, eczema (atopic dermatitis), Iliac disease, necrotizing enterocolitis, sudden infant death syndrome (SID), type 1 and type 2 diabetes o Breastfeeding triggers biochemical reactions which allows for the enzymes, hormones, growth factors, and immunologic substances to effectively defend against infectious diseases for the infant.
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