The Female Reproductive System

Female Reproductive Structures

Female Reproductive Structures (side view) Oviduct Ovary Uterus Urinary Bladder Rectum Pubic bone Cervix Urethra Body (erectile tissue) Vagina Glans Clitoris Vestibular (Bartholin’s) gland Prepuce Labia minora Labia majora Vaginal opening

Step by Step – The life of a female Ovaries develop in fetus Produce sex hormones (estrogen and progesterone) 400 000 follicles develop (potential eggs) Constant decline after puberty Each menstrual cycle, ~1000 follicles develop but only one becomes mature

Reproductive success declines after age 27 Do the math! Question: How many periods will a female have in her life? About 400 Question: How long will she be able to reproduce? (Assuming her first period is at age 13) 33 years, From age 13 – 46 (approximately) Reproductive success declines after age 27

Skip to Puberty: Oogenesis Ovary Follicles have two kinds of cells Primary oocyte ( meiosis  becomes the egg) Granulosa cells (nutrient for the oocyte) FSH from pituitary causes follicle development FSH = follicle stimulating hormone Ovary

Oogenesis Nutrient cells around primary oocyte divide Meiosis I (in the ovary) Majority of nutrients to one cell (secondary oocyte) Polar body produced Meiosis II (occurs later if it contacts a sperm) Majority of nutrients to one cell again (egg)

Ovulation Cells around primary oocyte create a fluid filled cavity Follicle (primary oocyte) Cells around primary oocyte create a fluid filled cavity Follicle pushes outwards Blood vessels weaken Secondary oocyte released = ovulation Growing follicle Secondary oocyte Mature follicle Ovary Granulosa cells Ruptured follicle

Ovulation Surrounding follicle cells become the corpus luteum Degenerating corpus luteum Surrounding follicle cells become the corpus luteum Produces progesterone to prepare uterus No pregnancy? Corpus luteum dies after 10 days Becomes corpus albicans Corpus luteum

The journey of the oocyte!

Secondary oocyte enters the oviduct Carried by cilia Could be fertilized here If it doesn’t meet a sperm, the oocyte will die within 24- 48 hours Takes 3-5 days to travel to the uterus (Progesterone from the corpus lutem stops uterine contractions!)

Fertilization (maybe?) Secondary oocyte and sperm could meet in oviduct (oocyte  egg) Acrosome on sperm breaks into the egg Only one sperm can enter

Fertilized Egg development (maybe?) Fertilized egg (zygote) begins to divide

Implantation (maybe?) Fertilized egg can implant in the endometrium (nourishes the egg) Implantation in the oviduct is BAD (ectopic pregnancy)

If fertilization DOESN’T occur (likely!) Corpus lutem eventually dies Lack of progesterone causes uterine contractions Menstruation! Sheds endometerium Start all over again… So… how is this cycle controlled?

(Estrogen and) progesterone FSH = follicle stimulating hormone GnRH = gonadotropin releasing hormone Hypothalamus LH = lutenizing hormone GnRH - FSH - FSH and LH LH and FSH levels drop Corpus luteum dies Progesterone drops Uterus contracts Anterior pituitary + LH FSH LH Follicle development ovulation Corpus luteum forms Estrogen (Estrogen and) progesterone Secondary female Characteristics Prepare endometrium Uterine contractions

2005-2006

Ant. Pituitary releases FSH FSH causes maturation of follicle 5 Ant. Pituitary releases FSH FSH causes maturation of follicle Follicle releases estrogen Endometrium builds Estrogen inhibits FSH, stimulates LH release Increased LH causes ovulation Corpus luteum forms C. luteum secretes progesterone (stops uterine contractions) Progesterone inhibits LH No LH  C. luteum disintigrates Progesterone levels fall (no C. luteum to make it) Uterus contracts, Endometrium is shed 9 1 7 10 6 2 3 8 11 4 12

What if the egg IS fertilized? Important to maintain progesterone levels Stops uterine contractions HCG (human chorionic gonadotropin) keeps the corpus luteum alive Corpus luteum keeps progesterone level high (HCG detected by pregnancy tests)

Animal Development Umbilical blood vessels Mammalian embryo Chorion Bird embryo Amnion Yolk sac Allantois Fetal blood vessels Placenta Maternal blood vessels 2005-2006

Human fetal development 10 weeks 2005-2006

Placenta Materials exchange across membranes 2005-2006

Human embryonic development embryo showing tail & limb buds 2004-2005

Human embryonic development beginning of the eye can be seen, as well the bulging heart & the umbilical cord 2004-2005

Human embryonic development lens of the eye can be seen forming, the mass of the heart bulging from the chest, & the beginnings of the finger rays 2004-2005

Human embryonic development beginning of the ear is clearly seen note the bend of the elbow joint has begun, the fingers are forming and toes are beginning to bud off the foot 2004-2005

Human embryonic development Note the formation of the nose, eyelids, ear flap & well defined toes & fingers 50–60 days (8 weeks) Both knee & elbow are visible. Embryo has formed most of basic organ systems & will spend remainder of development in “fetal” period. Organs grow, mature, & begin to learn their respective functions 2004-2005

Human fetal development 4 weeks 7 weeks 2005-2006

Human fetal development Week 9 - week 40 = fetus after 12 weeks or so, the baby's development is largely "finished" some exceptions: brain & lung development Week 16 2004-2005

Human fetal development 12 weeks 20 weeks 2005-2006

Human fetal development The fetus just spends much of the 2nd & 3rd trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid Week 20 2005-2006

Human fetal development 24 weeks (6 months; 2nd trimester) fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix 2005-2006

Human fetal development 30 weeks (7.5 months) umbilical cord 2005-2006

Getting crowded in there!! 32 weeks (8 months) The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming 2005-2006

Birth (38-40 weeks) Baby’s head pushes on cervix Oxytocin Stimulates contraction of uterus Each contraction causes more oxytocin release Intestine Placenta Umbilical cord Wall of uterus Bladder Cervix 2005-2006 Vagina

Birth A positive feedback loop! 2005-2006

The end of the journey! 2005-2006