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(b) Progesterone and estrogens.
(a) Estrogen (high levels) and oxytocin.
(b) Any two of: • Declining progesterone levels. • Loss of placental competency (placenta deteriorates). • High estrogen levels increasing uterine sensitivity
to oxytocin. • Peak in oxytocin. • The physiological state of fetus (release of stress hormones etc.)
is now known to play a major part in labor onset
also. 3. The placenta secretes hormones that are important in
maintaining the pregnancy and preparing the breasts
for lactation. 1. 5. 6. (a) In the case of labor, positive feedback between
oxytocin and uterine contraction accelerates the
physiological processes that bring about delivery
of the infant. Oxytocin causes uterine contraction
and stretching of the cervix, which causes more
release of oxytocin and so on until the delivery,
after which stretching of the cervix ceases and
the positive feedback loop is ended.
(b) Positive feedback is also important in lactation
and milk letdown. Suckling stimulates the
secretion of prolactin (milk production) and
oxytocin (milk let down). The more the infant
suckles, the more these hormones are produced.
This mechanism is important for maintaining
lactation and inducing greater milk production,
especially during periods of infant growth.
(a) Antibodies are used to detect the presence of
the hormone (HCG) produced by the placenta in
pregnancy. The antibodies are produced against
the glycoprotein hormone and bind them to form
a complex, which is captured and immobilized by
capture antibodies to create a color change in the
test window. (a) Drugs may induce release of FSH from the
pituitary so that development of ova is stimulated.
(b) Some drugs contain FSH and/or LH and directly
induce the development and release of many ova. 2. (a) Where the fallopian tubes are blocked.
(b) Where the ovaries are not functioning normally (a
donor egg may be necessary). 3. Risk associated with fertility drugs: Multiple pregnancy
(twins or triplets). These involve a higher risk of ea...
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- Winter '13