Female Reproductive System (Awkward subject, don't read unless prepared for details)

1. Collection of organs and other structures located in pelvic region
2. Functions:
• producing eggs, which are female gametes
• secreting female sex hormones
• receiving sperm during sexual intercourse
• supporting the development of a fetus
• delivering a baby after birth
• breastfeeding a baby after birth
3. Development before birth
• reproductive organs develop into female organs, such as ovaries and uterus, unless an embryo is stimulated by testosterone
• most internal female organs have formed by the third month of development
• immature ova (eggs), form in ovary before birth
• female produces all eggs she will ever make before birth
• baby girls are born with reproductive organs present but immature and unable to function
• grow very little during childhood
• grow rapidly and mature during puberty
4. Changes of puberty
• girls begin puberty a year or two earlier than boys
• complete puberty in about four years instead of six
• major sex hormone is estrogen rather than testosterone
• puberty starts when hypothalamus stimulates pituitary gland to secrete hormones that target ovaries
• LH and FSH stimulate ovary to produce estrogen
• estrogen promotes growth and other physical changes in females
• stimulates development of bones and contributes to adolescent growth spurt in height
• changes also involve maturation of organs that are necessary for reproduction
• mature reproductive organs are primary sex characteristics
• other changes lead to traits that are secondary sex characteristics
• menarche (beginning of menstruation) is most significant change (discussed later) 
5. Adolescent growth spurt
• females go through growth spurt in height like boys do 
• growth spurt in girls starts a year or two earlier and ends about three years sooner
• do not grow as rapidly during their peak grow rate
• average about 10 cm shorter than males on average after growth spurt
6. Timing of puberty
• changes of puberty happens in same order for most females
• first observable change is beginning of breast development by about age 10 in the U.S.
• the appearance of pubic hair also occurs next, at age 10.5 years, on average
• growth spurt in height begins first year of puberty
• ovaries and uterus gradually increase in size
• menarche occurs usually between age 12 and 13 in U.S. girls
• attains adult height by age of 14.5 years
• menarche may occur as early as 8 years or as late as 16 years
7. External female reproductive organs
• referred to collectively as vulva
• include labia and mons pubis
• labia protect vagina and urethra
• mons pubis consists of fatty tissue covering the pubic bone, protecting the pubic bone and vulva from injury
8. Internal female reproductive organs
• includes vagina, uterus, fallopian tubes, and ovaries
• vagina
• tube-like structure about 8-10 cm long
• begins at vulva and extends to uterus
• has muscular walls lined with mucous membranes
• receives sperm during sexual intercourse
• provides passageway for baby to leave mother's body during birth
• uterus
• muscular organ about 7.5 cm long and 5 cm wide
• thick lining of tissues known as endometrium
• lower, narrower end of uterus is called cervix
• cervix is where fetus grows and develops until birth
• uterus can expand to accommodate growing baby during pregnancy
• muscular contractions of uterus push the baby through cervix during childbirth
• fallopian tubes
• two of them 
• 7-14 cm long
• each tube reaches one of the ovaries
• ovary end of tube has fringe-like structure that moves with wavelike motions
• ovaries
• two small, oval-shaped organs that lie on either side of uterus
• egg-producing organs of the female reproductive system
• contains hundreds of thousands of immature eggs
• each egg is located within a follicle
• follicle consists of egg surrounded by special cells that protect egg until puberty then help the egg mature
9. Breasts
• secondary sex characteristics
• role in nurturing an infant after birth
• each breast contains mammary glands
• cells of mammary glands secrete milk, which drains into ducts leading to the nipple
10. Egg production
• a female's ovaries contains all the eggs she will ever produce at birth
• eggs do not start to mature until puberty
• one egg typically matures each month throughout female's adult years until she reaches middle adulthood
11. Oogenesis
• process of producing eggs in the ovary
• eggs are haploid cells, which have half the number of chromosomes of other cells in the body (diploid cells) 
• must be haploid for sexual reproduction to result in diploid offspring
• occurs in several steps that involve different types of cells
• begins when oogonium with diploid number of chromosomes undergo mitosis to form primary oocytes
• proceeds as primary oocyte undergoes first cell division of mitosis
• forms secondary oocytes with haploid number of chromosomes
• secondary oocyte undergoes second meiotic cell division to form haploid, if fertilized by sperm
• oogenesis begins with oogonia
• immature eggs that form in ovaries before birth
• diploid cells and equivalent to spermatogonia in males
• ovaries contain about seven million oogonia by fifth month of fetal development
• oogonia undergoes mitosis, forming cells called primary oocytes
• oocytes are also diploid cells
• primary oocytes begin first division of meiosis, but do not complete it until long after birth
• average female has about 2 million primary oocytes in ovaries
• number of oocytes falls as they deteriorate and disappear
• by puberty, about 300,000 to 400,000 primary oocytes left in average girl's ovaries
12. Maturation of a follicle
• each month, one follicle starts to mature
• primary oocyte in follicle resumes meiosis and divides to form secondary oocyte and polar body (smaller cell) 
• both are haploid cells
• secondary oocyte has most of the cytoplasm from original cell and is larger than polar body
• polar body disintegrates and disappears from ovary
13. Ovulation
• release of secondary oocyte by ovary
• occurs every 28 days in sexually mature female
• may range normally from 24-36 days
• each month only one of the ovaries matures a follicle
• releases egg
• eggs released seem to be at random
• after secondary oocyte leaves ovary, it is swept into fallopian tube by the fringe-like ends
• cilia line the tube and help oocyte through to the uterus
• if secondary oocyte is fertilized by sperm as it is passing through the fallopian tube, it divides to form mature egg and polar body
• if not, then it passes into the uterus as an immature egg
14. Menstrual cycle
• ovulation is part of the menstrual cycle
• occurs each month in a sexually mature female
• menstruation is the process in which blood and other tissues are shed from uterus and leave body through vagina
• also called menstrual period, or menses
• sometimes divided into two cycles, ovarian cycle and uterine cycle
• ovarian cycle includes events that occur in the ovary
• uterine cycle includes events that occur in the uterus
• two cycles are closely related, so will be talked about as one
15. Phases of menstrual cycle
• cycle begins with menstrual phase
• typically lasts from one to four days
• when menstruation occurs
• arteries that supply endometrium of uterus constrict and break
• blood and endometrial tissue detach from inside of uterus and pass from uterus to vagina, then out of the body
• if there is an immature egg in the uterus, it passes out of the body with the menstrual flow
• ovarian cycle
• maturation of follicle, release of an egg, and formation of corpus luteum
• uterine cycle
• menstruation, development of endometrium, and thickening of endometrium in preparation for an egg
• follicular phase
• after menstruation
• endometrium in uterus begins to build up again
• several follicles start maturing in the ovary at the same time
• only one follicle will complete maturation
• rest will deteriorate and disappear
• around day 14 of menstrual cycle, the remaining mature follicle releases oocyte from ovary during ovulation
• luteal phase
• follows ovulation
• endometrium of uterus continues to prepare for fertilized egg
• becomes thicker and develops more blood vessels
• mature follicle develops into structure called corpus luteum
• if egg is fertilized and implants in the endometrium, the endometrium will help nourish it
• if not fertilized, the endometrium will break down, leading to menstruation
• events of menstrual cycle always occur in the same sequence, but timing may vary
• variation may occur from one female to another and from one cycle to the next for a given female
• some females have symptoms (bloating, abdominal cramps, and mood swings) before menstruation each month
• if symptoms are severe enough to interfere with daily life, condition is called premenstrual syndrome (PMS) 
• PMS can be helped with medications of lifestyle changes
16. Role of hormones
• same hormones that control female puberty and oogenesis also controls menstrual cycle
• LH, estrogen, and FSH
• estrogen controls secretion of two pituitary hormones by acting on the hypothalamus
• controls pituitary gland
• when estrogen levels rise in the blood, it stimulates pituitary gland to secrete more or less LH and FSH
• rising levels of hormones initiate a negative feedback that decreases production of hormones
• in positive feedback, rising levels of hormones feedback to increase hormone production
• estrogen and progesterone provide negative feedback during most of the menstrual cycle
• keeps levels more or less constant
• estrogen provides positive feedback to hypothalamus and pituitary gland during days 12-14
• causes rapid rise in production of estrogen by ovary and leads to ovulation
• progesterone
• hormone that promotes gestation, or carrying of a fetus
• function is to maintain endometrium of uterus
• changes in levels of 4 hormones (estrogen, LH, FSH, and progesterone) occurs during menstrual cycle
• estrogen secreted by ovaries increases, causing the endometrium of uterus to thicken
• FSH stimulates follicles in ovary to mature
• the maturing follicles produce estrogen, and level of estrogen rises
• when estrogen reaches a certain level, the pituitary gland releases surge of LH
• spike in LH stimulates one remaining mature follicle to release oocyte
• negative feedback keeps level of FSH, LH, estrogen, and progesterone stable
• during ovulation, positive feedback causes increase of FSH, LH, and estrogen
• progesterone rises as corpus luteum matures and produces progesterone
• negative feedback helps keep levels of other three hormones constant
• LH stimulates mature follicle to develop into corpus luteum after oocyte is released
• if egg has been fertilized, it will produce a hormone that helps maintain corpus luteum
• will continue producing progesterone and maintain endometrium
• if it has not been fertilized, the corpus luteum will disappear and stop producing progesterone
• endometrium will break down, detach from uterus, and pass out of the body during menstruation
17. Menopause
• menopause occurs when a woman has gone through 12 consecutive months without menstrual period
• can no longer reproduce because ovaries can no longer produce eggs
• cause of menopause is natural decline in estrogen secretion by ovaries as a woman ages
• may take a long time before her body adjusts to drop in estrogen
• may experience hot flashes, mood swings, and other symptoms during adjustment period