Reproductive Physiology

1) Menstrual Cycle

2) 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-step

FOLLICULAR 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)

1

1

2

1 2

2

3

3

3

3

4

4

4

5

5

Pregnancy…..stopping the menstrual cycle!E

stra

diol

~ E

stro

gen

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

Confocal image of retinal layers