Transcript Hormonal Regulation of the Reproductive System Chapter 9.4 McGraw-Hill Ryerson Biology 12 (2011) MALE REPRODUCTIVE HORMONES • The male reproductive organ, the testes contain: – seminiferous tubules (containing Sertoli.

Hormonal Regulation of the
Reproductive System
Chapter 9.4
McGraw-Hill Ryerson
Biology 12 (2011)
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
• Leydig cells produce mainly testosterone, and smaller
amounts of androsterone.
• Sperm are produced in the tubules and nourished by the
Sertoli cells.
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
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)
• At puberty the
hypothalamus begins to
secrete gonadotropic
releasing hormone
(GnRH) which causes the
anterior pituitary to
release FSH and LH.
• 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.
• 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.
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.
• ~400 000 follicles at puberty,
only ~400 will develop into
mature ovum.
http://embryology.med.unsw.edu.au/Notes/
images/week1/ovary/ovary5x.gif
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.
Female Feedback Loop
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
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.
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.
Female
Feedback
Loop
Flow Phase
• ~5 days (d1-5),
shedding of
endometrial
lining.
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)
Homework
• Pg 425 #1, 2, 5, 6, 8, 9