Chapter 21

Chapter 21

Female Reproduction

The Female Private Parts• Ovaries makes the eggs• Oviducts also called fallopian tubes. Tube that leaves the

ovaries. Carries the egg from ovary to uterus.• Uterus This is were a fetus grows.• Cervix the opening to the uterus and connects the vagina

to the uterus.• Vagina Used for sexual intercourse, and used in giving

birth.• Clitoris sexual stimulation• Endometrium The inner lining of the uterus. Makes the

placenta during pregnancy. When not pregnant the endometrium is shed. This is the “period”

Estrogen, the female hormone• Secondary sexual characteristics– Breast development– Pubic Hair

• Estrogen and progesterone maintain the sex organs (like the uterus)

• Involved in the Uterine Cycle– Menstrual Cycle or Uterine Cycle or A Period– The Ovarian Cycle making an egg

How do Ladies make an Egg?• There are many follicles in the ovary and each contains

an immature egg.• One follicle will start to develop and it will also produce

female sex hormones estrogen and progesterone.• The follicle will then release the egg (also called an

oocyte)• The egg will then travel down the fallopian tubes and

to the cervix• After the ovary has released the oocyte the follicle

then turns into the corpus luteum. This produces hormones for about 10 days and then slowly degrades.

Primary FollicleSecondary Follicle

Oocyte

Secondary Oocyte

Corpus LuteumDegenerated Corpus Luteum

• We see three main phases in the ovary1. The first is the follicle making an oocyte. This is

called the follicular phase2. The second is the moment that the oocyte is

released (this a mature oocyte, which is called a secondary oocyte) into the fallopian tube. This is called ovulation

3. The thrid is after the follicle releases the oocyte and the follicle develops into the corpus luteum. This is called the luteal phase.

The Ovarian Cycle

Ovarian Cycle

Follicular PhaseOvulation

Luteal Phase

The Uterine Cycle• This is the menstrual cycle. This is usually a 28 day cycle.

1. Dat 1 to 5. There is a low level of hormones. This causes the endometrium to shed. This is what is commonly called a woman’s period. Called Menstruation.

2. Day 6 to 13. Increased estrogen by the ovary follicle causes the endometrium to build up again. This is called the proliferation phase.

3. Day 14. Ovulation usually occurs.4. Day 15 to 28. progesterone produced by the corpus luteum

thicken the endometrium. Endometrium is now ready to receive a developing embryo. This is called the secretory phase

Uterine Cycle

How the cycles are controlled• The hypothalamus releases GnRH (gonadotropin

releasing hormone).• This causes the anterior pituitary gland to release FSH

(follicle stimulating hormone) and LH (Luteinizing hormone).

• FSH causes the ovary to stimulate the follicle to produce estrogen.

• LH stimulates the corpus luteum to produce progesterone.

• The estrogen and progesterone causes a feedback to tell the hypothalamus if it needs more GnRH

Fertilization and Pregnancy• Fertilization happens in the fallopian tubes (oviduct).• When the embryo gets to the uterus the endometrium is now

ready to receive the embryo.• The placenta is made out of both maternal and fetal tissues. • The placenta starts off making Human chorionic gonadotropin

(HCG). This maintains the corpus luteum until it the placenta is developed enough to make its own estrogen and progesterone.

• The placenta and the corpus luteum make estrogen and progesterone for two reasons1. To send a message to the hypothalamus so it does not make GnRH

and the pituitary does not make LH and FSH2. To maintain the lining of the uterus.

Feedback Loops• Testosterone production is a negative feedback loop.– If there is a lot of testosterone the body stops making

testosterone– If there is little testosterone the body starts making more

tesosterone– Negative feedback loops are used to maintain homeostasis

• A positive feedback loop works differently.– If there is a lot of something then it will make even more and

then even more and more until an event occurs– An example is platelets clotting blood. When one starts to

clot then it starts a reaction that tells more and more platelets to clot that are close to it.

Pregnancy and Positive Feedback Loops• During Childbirth contractions occur• A contraction is when the muscles of the uterus

contract to signal and help push the baby out.• Contractions are brought about by the hormone

oxytocin and the more contractions occur then the more oxytocin is released.

• This means that more and more oxytocin is released in the body and more and more contractions occur.