1. Unit B: Reproduction and Development
Chapter 16
Section
Hormonal Control of the Female Reproductive System

2. Primary Sex Characteristics
Primary sexual characteristics – physical characteristics of an organism that are directly involved in reproduction.
Includes all the structures of the female reproductive system.
Examples for females:
ovaries
uterus
Fallopian tubes
etc.
Primary Sex Characteristics

3. Secondary Sex Characteristics
Secondary sexual characteristics – external features of an organism that are indicative of its gender, but are not reproductive organs themselves.
Examples for females:
enlarged breasts
less facial hair
more body fat
wider hips
Secondary Sex Characteristics

4. Female Reproductive Hormones
1. Estrogen
produced and secreted by the follicle cells in the ovaries
inhibits growth of facial hair
initiates secondary sexual characteristics
causes thickening of the endometrium
Female Reproductive Hormones

5. 3. Follicle Stimulating Hormone (FSH)
2. Progesterone
produced and secreted by the corpus luteum
inhibits ovulation during pregnancy
firms the cervix to prevent expulsion of the fetus
continues stimulation of the endometrium
3. Follicle Stimulating Hormone (FSH)
gonadotropic hormone – hormone produced by the pituitary that regulates the function of the ovaries in females and the testes in males
produced and secreted by the pituitary gland
stimulates the development of the follicle cells in the ovary

6. 4. Luteinizing Hormone (LH)
gonadotropic hormone
produced and secreted by the pituitary gland
stimulates ovulation and the formation and maintenance of the corpus luteum
5. Gonadotropin Releasing Hormone (GnRH)
produced by the hypothalamus
stimulates FSH and LH

7. Menstrual cycle – an almost monthly cycle in which the endometrial lining of the uterus prepares for pregnancy; if pregnancy does not occur the lining is shed at menstruation.
The menstrual cycle is divided into 4 phases.
Flow Phase (menstruation)
Follicular Phase
Ovulatory Phase
Luteal Phase
Menstrual Cycle

8. Flow Phase: Days 1-5 AKA menstruation.
The shedding of the endometrium.
It is the only phase in the menstrual cycle that can be determined externally; therefore this phase is used to mark the beginning of the cycle.
Approximately 5 days is required to clean the uterus.
Flow Phase: Days 1-5

9. Follicular Phase: Days 6-13
Is the development of the follicle cells in the ovaries.
As the follicles develop, estrogen is produced and secreted, increasing the estrogen concentration in the blood.
Endometrium is produced.
Follicular Phase: Days 6-13

10. Ovulatory Phase: Day 14 Secondary oocyte bursts from the ovary.
Estrogen levels fall.
Follicle cells begin to change into the corpus luteum.
Ovulatory Phase: Day 14

11. The full development of the corpus luteum marks the beginning of the luteal phase.
Corpus luteum secretes both estrogen and progesterone.
Estrogen and progesterone levels rise in the blood.
Estrogen and progesterone cause thickening of the endometrium in preparation of pregnancy.
Luteal Phase: Days 15-28

12. Inhibits further ovulation.
Firms the cervix to prevent expulsion of the fetus.
When fertilization does not occur, estrogen and progesterone levels drop causing uterine contractions.
These contractions cause the endometrium to pull away from the uterine wall.
Shedding of the endometrium marks the beginning of the flow phase once again.

13. Phase
Description of Events
Hormone Produced
Days
Flow
menstruation
1-5
Follicular
follicles develop
endometrium is formed
estrogen produced by follicle cells
6-13
Ovulation
s. oocyte bursts from ovary 14
Luteal
corpus luteum forms and endometrium thickens
estrogen and progesterone produced by the corpus luteum
15-28

16. Negative Feedback Systems for FSH and LH
Beginning at puberty when estrogen is low, the hypothalamus secretes GnRH.
GnRH activates the pituitary gland to secrete FSH.
During the follicular phase of the menstrual cycle, the blood carries FSH to the ovary, which stimulates the development of the follicle cells.
The follicle cells secrete estrogen, which initiates the development of the endometrium.
Negative Feedback Systems for FSH and LH

17. As estrogen levels rise, a negative feedback message is sent to the pituitary gland to turn off secretions of FSH.
The follicular phase has ended.
Simultaneously, the rise in estrogen stimulates the release of LH.
LH acts on the follicles stimulating the release of the secondary oocyte.
Ovulation occurs.
After ovulation LH acts on the remaining follicle cells turning them into corpus luteum.

18. The luteal phase has now begun.
The corpus luteum secretes both estrogen and progesterone, this increases further development of the endometrium.
As these two hormones build up, a second negative feedback system is activated.
It tells the pituitary to stop releasing LH and the hypothalamus to stop releasing GnRH.
Estrogen and progesterone levels drop, signaling the beginning of menstruation.