physiology of reproductive tract

By Dr. Eman

The hypothalamus
The hypothalamus is composed of neural tissues its physicaly connected to the pituitary by the pituitary stalk, within this the anterior pituitary (adeno hypophysis) is connected to the hypothalamus by the pituitary portal system which are vesceles from the carotid and post. Communicating arteries. The post. Pituitary (neurohypopysis) is connected to the hypothalamus by a rich plexus of nerves

Hypothalamus

: the hypothalamic nerve cells act both as neurones and as endocrine cells the, hormomnes are synthesised in the cytoplasm of the neurons and then passed in the axon of nerve terminals

Definitions & Functions Relative to Reproduction

Produces GnRH which stimulates the production of FSH & LH by the anterior pituitary gland initiating the ovarian cycle. Produces Oxytocin which is stored in the posterior pituitary gland.
Posterior Pituitary: Stores & releases hormone Oxytocin to stimulate uterine contractions (Braxton Hicks) & the milk let-down reflex.

Hypothalamus and pituitary gland

Hormone Sources & Functions
Gonadotropin-releasing Hormone (GnRH) : Source: Hypothalamus
Targets & Functions: Females & Males - Anterior Pituitary Stimulates the production of Follicle Stimulating Hormone (FSH) & Leutinizing Hormone (LH) Regulates the release of FSH & LH by the anterior pituitary gland

Hormone Sources & Functions

Follicle Stimulating Hormones FSH Source: Anterior Pituitary
Targets & Functions: Females - Ovaries Stimulates follicle growth & maturation Stimulates estrogen production Males - Seminiferous Tubules Promotes sperm production (Spermatogenesis) by establishing testosterone receptors on tubules

Leutenizing Hormone LH:

Source: Anterior Pituitary
Targets & Functions: Females - Ovaries Stimulates primary oocyte to complete first meiotic division to become secondary oocyte Triggers ovulation of secondary oocyte
Transforms ruptured follicle into corpus luteum Stimulates production of progesterone by corpus luteum
Males - Seminiferous Tubules Stimulates sperm production (Spermatogenesis) by causing interstitial cells in testes to secrete testosterone
Corpus luteum

Prolactin:

Source: Anterior Pituitary
Targets & Functions breast: Breasts Stimulates alveoli of breasts to produce milk
Regulation Release of prolactin by anterior pituitary is regulated by hypothalamus production of dopamine Prolactin Inhibiting Hormone (PIH)

Oxytocin:

Sources: Manufactured by hypothalamus. In the supraoptic and para ventricular gland Stored & released by Posterior Pituitary
Targets & Functions: Uterus Stimulates contraction of uterine myometrium causing lowering of fetus & labor
Breasts Stimulates contraction of milk ducts and sinuses, releasing milk
Positive Feedback Mechanisms: 1. Childbirth - Stretching of uterus and cervix 2. Suckling - Milk letdown reflex


1. Hypothalamus releases GnRH.
2. GnRH stimulates anterior pituitary to release FSH.
FSH
3. FSH stimulates a follicle to grow & produce estrogen.
Estrogen


FSH
Estrogen
4. Rising levels of estrogen cause anterior pituitary to increase production & storage of LH.
LH
Estrogen


5. High estrogen causes LH to be released in a burst & the endometrium to thicken (proliferative phase).
6. High LH stimulates first meiotic division of primary oocyte.
FSH
Estrogen
Estrogen
LH

7. High LH triggers ovulation.

FSH
Estrogen
Estrogen
LH
8. High LH causes ruptured follicle to become a corpus luteum.


FSH
9. Corpus luteum produces progesterone.
Estrogen
Estrogen
LH
Progesterone
X
X
10. Progesterone inhibits the production of FHS & LH by the anterior pituitary & stimulates secretory phase (negative feedback mechnisim).


11. Diminishing levels of FSH & LH cause corpus luteum to deteriorate & produce less progesterone.
12. Diminishing levels of estrogen & progesterone cause inhibition of FSH & LH to end & thickened endometrium to slough (menses).
Estrogen
FSH
LH
Progesterone
X
X
X



FSH
13. Increasing levels of FSH cause a new cycle to begin.

Menstrual (Uterine) Cycle

Slide 16.38

Cyclic changes of the endometriumRegulated by cyclic production of estrogens and progesteroneStages of the menstrual cycleMenses – functional layer of the endometrium is sloughedProliferative stage – regeneration of functional layerSecretory stage – endometrium increases in size and readies for implantation

Hormonal Control of the Ovarian and Uterine Cycles

Slide 16.39a

Figure 16.12a, b

Hormonal Control of the Ovarian and Uterine Cycles
Slide 16.39b

Figure 16.12c, d

Hormone Production-Ovaries

Slide 16.40

Estrogens Produced by follicle cells Cause secondary sex characteristics Enlargement of accessory organs Development of breasts Appearance of pubic hair Increase in fat beneath the skin Widening and lightening of the pelvis Onset of menses

Hormone Production by the Ovaries

Slide 16.41

Progesterone Produced by the corpus luteum Production continues until LH diminishes in the blood Helps maintain pregnancy

Progesterone:

Source: Corpus Luteum & Placenta
Targets & Functions: Females - Uterus Maintains thickened endometrium Stimulates nutrient release Quiets myometrium
Corpus luteum
Females - Breasts Stimulates development of alveoli for milk production
Females - Anterior Pituitary Inhibits production & release of FSH & LH