Reproductive Physiology
1) Menstrual Cycle2) Pregnancy 3) Lactation
Menstrual Cycle: Generalizations and terms•Two main phase: follicular & luteal
•Pituitary Gland secretes•Luteinizing Hormone (LH)•Follicle Stimulating Hormone (FSH)
•Ovary produces follicle containing an egg
•Follicle then Corpus Luteum secretes Estrogen, Progesterone, Inhibin
•Uterus prepares for egg fertilization & growth
•Spike in Progesterone leads to Body Temp spike
Menstrual Cycle: Step-by-stepFOLLICULAR PHASE
1) Period: old uterine lining sloughed FSH is high > a follicle matures
2) Estrogen gradually increases inhibiting FSH ***ensures only one follicle***
LUTEAL PHASE
3) Estrogen levels peak causing spike in FSH & LH***ovulation: egg leaves follicle***
Uterine wall thickens
**Fertilization can now occur in a ~ 12 hour window**
4) Follicle converted to Corpus Luteum ** Secretes Progesterone & Inhibin** Prepares Uterus for implantation
***If Fertilization DID NOT OCCUR within 12 hours after 3) then….5
5) Corpus Luteum and Egg dies, Uterine Wall sloughed Estrogen, Progesterone, Inhibin levels drop
> FSH increase..back to 1)
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Pregnancy…..stopping the menstrual cycle!E
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Corpus Luteum and later Placenta secrete Estrogen & Progesterone
This prevents the breakdown of the uterine wall….thus preventing menstruation
Estrogen & Progesterone Levels stay elevated due to Human Chorionic Gonadotropin (hCG)
Pregnancy tests = hCG tests!
Parturition: LaborMechanism that initiates labor is not well understood:
1) Progestrone & Estrogen drop after labor begins
1) Oxytocin initiates Uterine contractions…but inducing labor with artificial oxytocin doesn’t always work
3) Fetus may secrete a hormone…(CRH, corticotropin releasing hormone, controls adrenal gland)
Labor IS well understood:
Once labor begins uterus undergoes powerful contractions+
Tissue in birth canal softens due to the peptide, RELAXIN=
Which eject the baby from uterus and cause delivery
Lactation
Mammary Gland
Myoepitheleal cells
Milk secreting cells
Smooth Muscle cells
Milk Ducts
Control of Lactation
Suckling Mechanoreceptors
Higher Brain
Hypothalamus
Ant. Pituitary
Post. Pituitary
PIH
Prolactin Oxytocin
HAPPY BABY!
Milk Secretion
Smooth MuscleContration
Oxytocin: Myoepithelial & Duct Muscle Contraction
Crying baby
PIH = prolactin inhibiting hormone
Prolactin: Milk secretion in mammary gland
Hope you enjoyed Human Physiology
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