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Male Reproductive Hormones
GnRH • causes anterior pituitary to secrete gonadotropic hormones FSH and LH
FSH
• produced in anterior pituitary gland
• initiates spermatogenesis in seminiferous tubules
inhibin
• released by the seminiferous tubules with sperm
• forms a negative feedback loop with FSH
FSH + inhibin regulate rate of sperm production.
LH
• also from the anterior pituitary
• stimulates interstitial cells ­> testosterone
testosterone
• the major androgen
• triggers dev of male sex characteristics
• needed for maturation of sperm
LH + testosterone form a negative feedback loop, regulating the amount of testosterone in blood.
2° Male Characteristics:
• enlargement of penis + testes
• enlargement of Adam's apple
• development of muscle tissue
• formation of hair on face, chest, armpits, genital area
Produced by Role
GnRF
FSH
testosterone
LH
inhibin Female Reproductive Hormones
The human reproductive system does not follow a seasonal pattern, but it is cyclical. The release of an ovum is timed so that the uterus is prepared to accept and sustain a developing embryo.
This pattern is called the menstrual cycle, and is under the control of the hypothalamus. It is usually about 28 days long, but can vary from 20 ­ 45 days and can differ from month to month.
Female Reproductive Hormones
The ovaries are composed of follicles, each containing a single ovum. 1st Stage of Menstrual Cycle: follicular stage
• GnRH from hypothalamus causes release of FSH from anterior pituitary
• levels of FSH increase
• in ovary: FSH stimulates follicles to develop and produce estrogen
Estrogen causes
• in uterus: endometrium to thicken and increase blood supply
• in various tissues: dev of 2° female chars
Estrogen forms a negative feedback loop with FSH. What will be the result of the increased estrogen levels on levels of FSH?
Female Reproductive Hormones
Levels of estrogen increase causing:
• less FSH to be produced (negative feedback)
• release of large amounts of LH from anterior pituitary
• in ovary: LH triggers ovulation (day 14)
*i.e. the release of an ovum from one of the ovaries
Female Reproductive Hormones
2nd Stage of the Menstrual Cycle: luteal stage
• Ovulation marks the beginning of the luteal stage
• Immediately following ovulation, the follicle becomes the corpus luteum
• this group of cells produces progesterone and estrogen
Progesterone •
•
•
•
inhibits LH production (negative feedback)
inhibits ovulation from other follicles (so only 1 ovum)
inhibits uterine contractions
continues preparation of endometrium for embryo
As LH levels fall, the corpus luteum degenerates.
Female Reproductive Hormones
As corpus luteum breaks down,
•
•
•
•
•
progesterone and estrogen levels drop
blood supply to endometrium decreases
endometrial tissue is deprived of nutrients and O2 + breaks down
contractions of uterus cause endometrium to pull away from uterine wall
excess blood + tissue passes through the vagina and out as menstrual flow
This marks the beginning of menstruation which coincides with the start of the next follicular stage. Menstruation usually lasts about 5 days.
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Label the stages of the Menstrual Cycle on the diagram below.
Levels of Pituitary Hormones
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Label Stages
Luteal Stage
Follicular Stage
Ovulation
Levels of Ovarian Hormones
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Label Phases
Proliferative
Menstrual
Secretory
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Day
Levels of Pituitary Hormones
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Follicular Stage
Ovulatory
Luteal Stage
Stage
Levels of Ovarian Hormones
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Secretory
Proliferative
Menstrual
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Day
Produced by Role
GnRF
FSH
estrogen
LH
progesterone Homework Questions:
What are some signs of ovulation?
Name and describe 2 prediction kits used to predict ovulation.
Attachments
Endrocrine Gland Function.wpd