NOTES: CH 46, part 2 –
Hormonal Control /
Reproduction
Hormones Involved in Reproduction - MALES
● Androgens: produced in Leydig cells in testes
(i.e. TESTOSTERONE)
● GnRH: from hypothalamus; stimulates anterior
pituitary to release FSH and LH
● FSH: acts on seminiferous
tubules to increase sperm
production
● LH: stimulates androgen
production
*primary sex characteristics:
-development of internal and external
reproductive organs
-sperm production
*secondary sex characteristics:
-deepening of voice
-distribution of facial & pubic hair
-muscle growth
Hormones Involved in
Reproduction - FEMALES
● MENSTRUAL CYCLE = changes that
occur in uterus
● OVARIAN CYCLE = changes that occur in
ovaries
Menstrual cycle occurs in 3
phases:
1) Menstrual flow phase (3-5 days):
endometrium is being shed from uterus
2) Proliferative phase (1-2 weeks):
regeneration & thickening of
endometrium
Menstrual cycle occurs in 3 phases:
3) Secretory phase (2 weeks):
endometrium continues to thicken,
becomes more vascularized & develops
glands which secrete a glycogen rich fluid
which serves as nutritional fluid for the
embryo
(IF embryo does NOT implant in uterine
lining by the end of this phase, a new
menstrual flow phase begins)
Ovarian Cycle:
1) Follicular phase: several follicles in
ovaries begin to grow
2) Ovulatory phase: follicle & adjacent wall
of ovary rupture, releasing the egg
(2° oocyte)
(Follicular phase)
Ovarian Cycle:
3) Luteal phase: the remaining follicular
tissue in ovary after ovulation becomes the
CORPUS LUTEUM which is endocrine
tissue that secretes hormones
(Luteal phase)
Menstrual and Ovarian Cycles
are closely related:
● increased amts. of estrogen secreted by
growing follicle stimulates endometrium to
thicken in preparation for embryo
(PROLIFERATIVE PHASE)
● after ovulation, estrogen & progesterone
secreted by the CORPUS LUTEUM
stimulate continued development &
maintenance of the endometrium
(SECRETORY PHASE)
Menstrual and Ovarian Cycles
are closely related:
● decreased concentration of estrogen &
progest. due to disintegration of the C.L.
reduces blood flow to the endometrium; the
endometrium breaks down & passes out of
the uterus
● IF embryo is present, it secretes HCG which
maintains estrogen & progest. secretion by
the C.L. so the endometrium is maintained
MENOPAUSE
Menopause: cessation of
ovulation and menstruation
-between ages of 46 and 54
-ovaries lose their
responsiveness to FSH/LH
-decline in production of
estrogens
FERTILIZATION & IMPLANTATION
● fertilization occurs in the
OVIDUCT
● female repro. tract produces
secretions which capacitate
sperm cells
● a capacitated sperm cell
reaches the egg and must
penetrate the ZONA
PELLUCIDA
FERTILIZATION & IMPLANTATION
● when sperm cell binds to
receptor molecules in zona
pellucida, the
ACROSOME releases its
contents (i.e. digestive
enzymes) so that it can
penetrate the plasma
membrane of the egg
(= “acrosomal reaction”)
FERTILIZATION & IMPLANTATION
● binding of sperm cell to egg triggers
depolarization of egg membrane (functions
as a “fast block” to polyspermy)
(= “cortical reaction”; a series of
changes in outer zone, “cortex,” of the
egg cytoplasm)
FERTILIZATION & IMPLANTATION
● CLEAVAGE (cell division) begins
approx. 24 hours after
conception
● after 3 days, embryo contains
approx. 16 cells (MORULA)
● embryo reaches uterus approx. 7
days after fertilization & contains
approx. 100 cells
(BLASTOCYST)
FERTILIZATION & IMPLANTATION
● implantation occurs within next
5 days
● for the first 2-4 weeks, embryo
obtains nutrients directly from
endometrium
● in 2nd trimester, fetus secretes
its own progesterone to
maintain pregnancy
BIRTH
● high estrogen levels
during the last weeks of
pregnancy trigger
formation of oxytocin
receptors in uterus
● oxytocin secreted by
fetus & posterior pituitary
of mother stimulate
smooth muscles of
uterus to contract
BIRTH
● oxytocin stimulates prostaglandin
secretion by placenta which enhances
muscle contraction of uterus
● decreased levels of progesterone after
birth remove inhibition from anterior
pituitary which allows for prolactin
secretion
BIRTH
● PROLACTIN stimulates milk production
after 2-3 days
● OXYTOCIN controls release of milk from
mammary glands
BIRTH CONTROL:
Methods of Contraception:
1) COITUS INTERRUPTUS: withdrawal of
penis before ejaculation
2) RHYTHM METHOD:
requires abstinence
from sexual intercourse
a few days before/after
ovulation
3) MECHANICAL BARRIERS:
-condom (male, female)
-diaphragm
-cervical cap
4) CHEMICAL BARRIERS:
-creams, foams, jellies w/spermicide
-easy to use, but high failure rate
unless used with a condom or
diaphragm
5) ORAL CONTRACEPTIVES:
-“the pill”
-contain synthetic hormones to disrupt the
ovarian cycle and prevent ovulation
-can be taken in pill form, injected, or
implanted
6) INTRAUTERINE DEVICE (IUD):
-small, solid object placed
within the uterus
-prevents implantation
of blastocyst
7) SURGERY:
-in males: VASECTOMY
-in females: TUBAL LIGATION