E7-1 Hormonal Control of Reproduction femalemale Dendrobates azureus.
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Transcript of E7-1 Hormonal Control of Reproduction femalemale Dendrobates azureus.
E7-1
Hormonal Control of Reproduction
female maleDendrobates azureus
E7-2
Hormonal Control of Reproduction
1. Critical importance to fitness
“its ability to perpetuate itself as measured
by its reproductive success” (Pianka 2000)
Energetically expensive
Therefore, must be precisely timed to insure maximal survival of young
young born at time most favorable for survival in cyclical environment
E7-3
2. Control of Reproduction
HYPOTHALAMUS
ADENOHYPOPHYSIS
GONAD: TESTIS OROVARY
MEDIAN EMINENCE
E7-4
DAYLENGTH
E7-5
DAYLENGTHTEMPERATURE
E7-6
DAYLENGTHTEMPERATURENUTRITION
E7-7
DAYLENGTHTEMPERATURENUTRITIONENDOGENOUS CLOCK
E7-8
Gonadotropin-Releasing Hormone (GnRH)
DAYLENGTHTEMPERATURENUTRITIONENDOGENOUS CLOCK
E7-9
GnRHStimulates
Gonadotropins: Luteinizing Hormone (LH) Follicle-Stimulating Hormone
(FSH)
E7-10
3. Functions of gonadotropins
a. Stimulate gametogenesis
production (meiosis) and maturation of gametes
Male: spermatozoa
Female: oocyte
E7-11
b. Stimulate steroidogenesis
steroid hormone production by gonads
Male: androgens (testosterone)
Female: estrogens (estradiol)
progestins (progesterone)
androgens
Actions similar in male and female, only timing and targets that differ
E7-12
4. Female system
Precise, often brief, secretion of gonadotropins in regular cycles
Cycles range from multiannual to days
E7-13
a. Ovary Structure
(1) connective tissue capsule
(2) ovarian follicle (1 to millions)
oocyte: premeiotic gamete
follicle cells: two layers of steroidogenic cells surrounding oocyte
inner layer: granulosa
outer layer: theca
(3) Ducts for oocyte transport and packaging
oviduct, uterus
E7-14
b. Control of ovarian function
LH Theca Cells+
E7-15
b. Control of ovarian function
LH Theca Cells Androgen+
E7-16
b. Control of ovarian function
LH Theca Cells Androgen
FSH+LH
Granulosa Cells
+
+
E7-17
b. Control of ovarian function
LH Theca Cells Androgen
FSH+LH
+
+
Estrogen
Granulosa Cells
E7-18
b. Control of ovarian function
LH Theca Cells Androgen
FSH+LH
Granulosa+
+
Estrogen
Blood
Granulosa Cells
E7-19
b. Control of ovarian function
LH Theca Cells Androgen
FSH+LH
Granulosa+
+
Estrogen
BloodOogenesis
Granulosa Cells
E7-20
c. Estrogens
(1) Local effects (paracrine)
Stimulate oocyte and follicle cell growth
Oocyte and follicle size increase
(2) Distant effects (endocrine)
(a) Feedback: slight negative feedback on LH
E7-21
(b) Primary Sexual Characteristics
Growth of ducts and organs directly responsible for gamete production and transport:
ovary, oviduct, uterus
(c) Secondary Sexual Characteristics
Anatomical structures not directly involved in gamete production, but associated with reproductive activity
physical and behavioral:
mating receptivity
E7-22
(d) Metabolic effects
tissue growth
follicle, ducts, mammary gland
energy storage
appetite stimulant
fat deposition
yolk production
vitellogenin : precursor protein
of yolk proteins.
E7-23
Ovary
FSHLH ESTROGEN
VITELLOGENESIS
LIVER
E7-24
Ovary
ESTROGEN
VITELLOGENIN
VITELLOGENESIS
(calcium, lipids,carbohydrates,phosphorous)
LIVER
FSHLH
E7-25
Ovary
ESTROGEN
VITELLOGENIN
VITELLOGENESIS
(calcium, lipids,carbohydrates,phosphorous)
LIVER
Folliculargrowth
E7-26
Vitellogenin concentration in blood plasma or serum can be measured by immunoassays known as ELISAs
Requires an antibody specific for vitellogenin.
E7-27
Vitellogenesis Cycle on the Kemp's ridley sea turtle
0
2
4
6
8
10
12
Jun Sep Dec Mar May Jul
POSTNESTING
PREMATING
MATING NESTING
E7-28
Female Reproductive Cycles
(1) Follicular Phase of the cycle
oocyte and follicle growth under
influence of estrogen
Oocyte can not be fertilized in the follicle
E7-29
(2) Ovulation
rupture of follicle and release of oocyte
stimulated by LH surge
Regulation of LH surge:
(a) environmental cues
e.g., daylength, temperature, substrate, mates, etc.
(b) endocrine cues
e.g., estrogen positive feedback
E7-30
LH surge transforms follicle cells into new endocrine gland:
Corpus luteum (CL)
External fertilizers:
eggs shed, CL very brief
cycle ends here
Internal fertilizers:
eggs retained, CL persists
E7-31
(3) Luteal Phase , the CL is steroidogenic
Estrogens
maintain 1° and 2° sexual characteristics
Progestins
negative feedback on LH with estrogen
prepare female for embryo support
stimulate structures essential for
embryo survival
e.g., uterus, mammary gland, albumin glands
All preparation in anticipation of fertilization
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(4) No fertilization
CL regresses, negative feedback gone, cycle restarts if CNS permits
(5) Fertilization
CL persists: progesterone
New endocrine gland: placenta
Progestins maintained until termination
Cycle can be manipulated: GnRH, steroids