THE FEMALE REPROCUCTIVE

TRACTLecture #2

I. THE GOAL

A. To produce a sex cell (egg) to unite with a sperm cell to create a new organism.

B. To maintain an environment suitable for a growing fetus.

II. EGG FORMATION

A. Oogenesis- The formation of egg cells.1. Occurs in the ovary

B. The primary oocyte (immature egg) develops inside of a follicle

II. EGG FORMATION (cont.)

C. As the follicle matures the primary oocyte divides into two cells…

II. EGG FORMATION (cont.)

1. The secondary oocyte2. A polar body (non-functioning cell, degenerates)3. This completes the first division of meiosis

II. EGG FORMATION (cont.)

4. Meiosis II occurs (divides again) producing another polar body and making the egg haploid (1/2)

II. EGG FORMATION (cont.)

D. Females are born with > 2 million eggs!1. Reduced to 400,000 by puberty2. Only 400 mature eggs are actually released!

III. THE JOURNEY

A. Once the secondary oocyte is formed, the follicle bursts and releases it into the oviduct

III. THE JOURNEY (cont.)

B. Ovulation- The release of the secondary oocyte into the oviduct.1. Occurs appx. 1 time per month2. Ovaries usually alternate

III. THE JOURNEY (cont.)

a. If more than one egg is released from one or both ovaries, fraternal twins may be the result.c. After ovulation, the follicle turns into a corpus luteum (CL) which produces progesterone.

III. THE JOURNEY (cont.)

C. Oviduct- Tube that transports the egg from the ovary to the uterus1. AKA uterine tubes, fallopian tubes2. The egg is swept towards the uterus by the cillia (tiny hairs).

III. THE JOURNEY (cont.)

3. Fertilization usually occurs in the first 1/3 of the oviduct.

III. THE JOURNEY (cont.)

D. Uterus- Thick walled, muscular organ that is designed to accommodate a developing fetus

III. THE JOURNEY (cont.)

1. If fertilization occurs, the embryo will embed in the lining of the uterus several days later.

a. Endometrium- Lining of uterus that provides nutrition for embryo.

III. THE JOURNEY (cont.)

2. If fertilization does NOT occur, the egg exits the uterus through the cervix and leaves the body through the vagina.

IV. HORMONES

A. Estrogen1. Egg Maturation2. Secondary sex characteristics

IV. HORMONES

a. Onset of menstrual cycleb. Broadening of pelvisc. Increased haird. Long bone growth (height)e. Fat depositionf. Breast development

IV. HORMONES

B. Progesterone1. Breast development2. Maintains lining of uterus3. Maintains pregnancy

IV. HORMONES

C. Follicle Stimulating Hormone (FSH)1. Begins follicle development2. Follicle releases estrogen

IV. HORMONES

D. Luetenizing Hormone (LH)1. Aides in follicle growth 2. Causes ovulation

IV. HORMONES

E. POSITIVE Feedback Mechanism1. The more estrogen that is produced by the follicle, the more FSH & LH are released from the pituitary.

IV. HORMONES

2. The more FSH & LH released from the pituitary, the more estrogen the follicle releases.3. This mechanism occurs until ovulation.

IV. HORMONES

E. NEGATIVE Feedback Mechanism1. After ovulation, the CL produces progesterone which inhibits FSH & LH

V. THE MENSTRUAL CYCLE

DAY 1-5: “Flow Phase” •High levels of FSH •Follicle is immature•LH, progesterone & estrogen are fairly low

V. THE MENSTRUAL CYCLE

DAY 1-5: “Flow Phase” •Blood, tissue, fluid, mucus and epithelial cells are shed

•Contractions of the uterus causes menstration.

V. THE MENSTRUAL CYCLE

DAY 6-14: “FollicularPhase”

•Increasing estrogen levels LH & FSH

•LH levels peak dramatically at appx. day 14 causing ovulation

•Body temp. increases .5°C

V. THE MENSTRUAL CYCLE

DAY 15-28: “Luteal Phase”

•The ruptured follicle becomes a corpus luteum that secretes progesterone.

V. THE MENSTRUAL CYCLE

DAY 15-28: “Luteal Phase”

•Progesterone maintains the endometrium in preparation for a fertilized egg.

V. THE MENSTRUAL CYCLE

DAY 15-28: “Luteal Phase”

•If fertilization does not occur the CL degenerates causing progesterone to stop

•The endometrium is flushed out•The cycle begins again!