1. Hormonal Regulation of the Reproductive System
Chapter 9.4
McGraw-Hill Ryerson
Biology 12 (2011)

2. MALE REPRODUCTIVE HORMONES
SBI 4U: Metablic Processes
MALE REPRODUCTIVE HORMONES
The male reproductive organ, the testes contain:
seminiferous tubules (containing Sertoli cells)
Interstitial cells of Leydig (Leydig cells) located between the tubules
Section 1.3

3. SBI 4U: Metablic Processes
Leydig cells produce mainly testosterone, and smaller amounts of androsterone.
Sperm are produced in the tubules and nourished by the Sertoli cells.
Section 1.3

4. Effects of TESTOSTERONE
SBI 4U: Metablic Processes
Effects of TESTOSTERONE
Spermatogenesis (creation of sperm)
Secondary sex characteristics at puberty (deeper voice, muscle development, body hair, acne)
Development of testes and penis
Levels are associated with sex drive
Section 1.3

5. Control of Testosterone
SBI 4U: Metablic Processes
Control of Testosterone
Pituitary and hypothalamus control the release of male sex hormones and therefore sperm production.
Pituitary produces and stores gonadotropic hormones:
Male follicle stimulating hormone (FSH)
Male lutenizing hormone (LH)
Section 1.3

6. SBI 4U: Metablic Processes
At puberty the hypothalamus begins to secrete gonadotropic releasing hormone (GnRH) which causes the anterior pituitary to release FSH and LH.
Section 1.3

7. SBI 4U: Metablic Processes
FSH stimulates seminiferous tubules Sertoli cells to produce sperm
Sertoli cells also release inhibin which feeds back to the anterior pituitary to inhibit further FSH release.
Section 1.3

8. SBI 4U: Metablic Processes
LH stimulates Leydig cells to increase testosterone production which binds to receptors in Sertoli cells to activate genes that increase and maintain sperm production, etc.
High levels of testosterone feedback on the anterior pituitary and hypothalamus to inhibit further LH release.
Section 1.3

9. SBI 4U: Metablic Processes
Section 1.3

10. FEMALE REPRODUCTIVE HORMONES
SBI 4U: Metablic Processes
FEMALE REPRODUCTIVE HORMONES
Reproductive organ: Ovaries
An ovary contains follicles, which are groups of cells surrounding an ovum (egg).
The follicular cells nourish the egg and produce the female hormones estrogen and progesterone.
~ follicles at puberty, only ~400 will develop into mature ovum.
Section 1.3

11. Menstrual Cycle and Female Reproductive Hormones
SBI 4U: Metablic Processes
Menstrual Cycle and Female Reproductive Hormones
Males produce sperm at a constant rate, females go through a complicated monthly cycle where one follicle and egg matures more than the rest and the egg is released (ovulation).
The surrounding follicular cells form the corpus luteum (CL) which secretes hormones essential for pregnancy.
The CL degenerates after ~10 days if pregnancy does not occur.
The menstrual cycle lasts ~28 days and occurs in phases regulated by GnRH, FSH and LH.
Section 1.3

12. SBI 4U: Metablic Processes
Female Feedback Loop
Section 1.3

13. SBI 4U: Metablic Processes
Follicular Phase
(day 6-13), follicles developing
Hypothalamus releases GnRH to anterior pituitary
FSH is released: stimulates follicle cells to mature and release estrogen
Estrogen causes:
endometrial lining of uterus to thicken
Inhibits release of FSH from pituitary and stimulates LH release
Section 1.3

14. SBI 4U: Metablic Processes
Section 1.3

15. SBI 4U: Metablic Processes
Ovulation
LH rise causes ovulation of the most mature ovum (~d14)
caught by fimbriae of fallopian tubes
slight dip in estrogen.
Birth control pills contain high concentrations of progesterone which inhibits ovulation and thereby prevents conception.
Section 1.3

16. SBI 4U: Metablic Processes
Luteal Phase
(d15-28) remaining follicle turn into the corpus luteum (CL)
CL secretes progesterone (P) and small amount of estrogen (E)
Prog. promotes build up of endometrium (uterine lining), inhibits further ovulation and inhibits contractions of uterus (preparing for pregnancy)
Build up of P and E inhibit further release of LH and FSH, causing CL to deteriorate
If egg not fertilized then levels of E and P decrease, and endometrium degenerates. This leads to menstruation.
Section 1.3

17. SBI 4U: Metablic Processes
Female Feedback Loop
Section 1.3

18. SBI 4U: Metablic Processes
Flow Phase
~5 days (d1-5), shedding of endometrial lining.
Section 1.3

19. Aging Ovaries and Menopause
SBI 4U: Metablic Processes
Aging Ovaries and Menopause
Female hormone levels fluctuate throughout reproductive years until menopause.
Chances of offspring with genetic disorders increases with mother's age, it is theorized that as follicles age they become genetically inferior.
Menopause: female sex hormones cease to be secreted, signals end of reproductive life (gradual process)
Section 1.3

20. Homework
Pg 425 #1, 2, 5, 6, 8, 9