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V) Fertilization, Pregnancy and Birth Birth
V) Fertilization, Pregnancy and Birth V) Birth
approximately 226 days after implantation uterine contractions begin signaling the beginning of parturition (labour).
the cervix thins and begins to dilate. the amnion is forced into the birth canal
it often bursts and the fluid lubricates the canal (breaking of the water).
as the cervix dilates uterine contractions move the baby through the birth canal.
after the birth the placenta is delivered.
V) Fertilization, Pregnancy and Birth V) Birth as the cervix dilates uterine contractions move the baby through the birth
canal. after the birth the placenta is delivered.
hormones play a vital role in the birthing process Relaxin,
produced by the placenta prior to labour causes the ligaments within the pelvis to loosen and the cervix to
soften. provides a more flexible passageway for the baby during
delivery. the decrease in progesterone is important to the onset of delivery.
V) Fertilization, Pregnancy and Birth V) Birth
causes the ligaments within the pelvis to loosen and the cervix to soften.
provides a more flexible passageway for the baby during delivery.
the decrease in progesterone is important to the onset of delivery.
Oxytocin a hormone from the pituitary gland causes strong uterine contractions appears in the mother’s blood prior to labour.
labour can be induced by administering prostaglandins or pitocin which is a synthetic form of oxytocin.
V) Fertilization, Pregnancy and Birth V) Birth
V) Fertilization, Pregnancy and Birth V) Birth
Estrogen Oxytocin
from ovaries
Induces oxytocin receptors on uterus
from fetus and mother’s posterior pituitary
Stimulates uterus to contract
Stimulates placenta to make
Prostaglandins
Stimulate more contractions
of uterus
Posi
tive
feed
back
+
+
Placenta Umbilical cord
Uterus Cervix
Dilation of the cervix 1
V) Fertilization, Pregnancy and Birth V) Birth
Expulsion: delivery of the infant 2
V) Fertilization, Pregnancy and Birth V) Birth
Delivery of the placenta
Uterus
Placenta (detaching)
Umbilical cord
3
V) Fertilization, Pregnancy and Birth V) Birth
V) Fertilization, Pregnancy and Birth
VI) Lactation
V) Fertilization, Pregnancy and Birth VI) Lactation
elevated estrogen and progesterone levels during pregnancy prepare the breasts for milk. each breast contains about 20 lobes of glandular tissue each
with a duct that carries fluid toward the nipple. prolactin stimulates the glands to produce fluid. prolactin is a hormone that is produced by the pituitary gland.
estrogen stimulates the release of prolactin during pregnancy the action of prolactin is inhibited by progesterone.
V) Fertilization, Pregnancy and Birth VI) Lactation
estrogen stimulates the release of prolactin during pregnancy the action of prolactin is inhibited by progesterone.
a decrease in progesterone and estrogen after birth results in a decrease in prolactin production an increase in prolactin activity
prolactin initially causes the production of colostrum colostrum closely resembles breast milk. contains milk sugar and milk proteins but lacks the milk fats.
a few days after birth, prolactin stimulates the production of milk.
V) Fertilization, Pregnancy and Birth VI) Lactation
colostrum closely resembles breast milk. contains milk sugar and milk proteins but lacks the milk fats.
a few days after birth, prolactin stimulates the production of milk.
colostrum and mother’s milk supply the baby with nutrients and antibodies.
prolactin may increase milk production but the milk still does not flow easily. Milk produced in the lobes of the glandular tissue must be forced
into the ducts that lead to the nipple. newborn suckling stimulates nerve endings in the areola of the
breast. sensory nerves carry information to the pituitary gland.
V) Fertilization, Pregnancy and Birth VI) Lactation
newborn suckling stimulates nerve endings in the areola of the breast. sensory nerves carry information to the pituitary gland.
oxytocin is released. oxytocin is carried by the blood to the breasts and
uterus. in the breast oxytocin causes weak contractions of
smooth muscle, forcing milk into the ducts. in the uterus oxytocin causes weak contractions of
smooth muscle allowing the uterus to return to pre-pregnancy size and shape.
VII) Twins
there are two basic types of twins: monozygotic or identical dizygotic or fraternal
VII) Twins two thirds of all twins are dizygotic.
occurs when two sperm fertilize two distinct eggs (in trizygotic triplets, three eggs are fertilized by three sperm)
dizygotic can be one of three combinations: two males
represents about 25% of all dizygotic twin sets two females
represents about 25% of all dizygotic twin sets one male and one female
represents 50% of all dizygotic twin sets
VII) Twins two males
represents about 25% of all dizygotic twin sets two females
represents about 25% of all dizygotic twin sets one male and one female
represents 50% of all dizygotic twin sets
the fertilization of two eggs by two sperm results in two separate embryos each with its own: chorion (outer membrane of the amniotic sac) amnion (inner membrane of the amniotic sac) placenta
in some instances, if the embryos implant very nearby each other along the uterine wall, the placentas can become fused.
VII) Twins chorion (outer membrane of the amniotic sac) amnion (inner membrane of the amniotic sac) placenta
in some instances, if the embryos implant very nearby each other along the
uterine wall, the placentas can become fused.
VII) Twins
in monozygotic twins one sperm fertilizes one egg. shortly after fertilization, instead of the blastocyst
remaining as one cell group, it splits in two. when the split happens it will determine how the
twins will implant in the uterine lining. the earlier the split, the more independent the
embryos will be.
VII) Twins the earlier the split, the more independent the embryos will be.
some scenarios include:
a very early split leading to the embryos having separate chorions, amnions and placentas. (This happens in approximately one-third of identical twins.)
twins having separate amnions and separate placentas but share one chorion.
twins having separate amnions but share one chorion and one fused placenta.
twins share one chorion, one amnion and one placenta (rarest combination).
VII) Twins twins having separate amnions and separate placentas but share one chorion. twins having separate amnions but share one chorion and one fused placenta. twins share one chorion, one amnion and one placenta (rarest combination).
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VII) Twins twins having separate amnions and separate placentas but share one chorion. twins having separate amnions but share one chorion and one fused placenta. twins share one chorion, one amnion and one placenta (rarest combination).
VII) Twins
the placenta provides the developing baby with the nourishment and oxygen it requires. it is advantageous for the monozygotic twins to have
separate placentas (even if they are fused). monozygotic twins who share a placenta will not
develop equally because one twin will receive more nourishment via the placenta than the other twin does. this is known as fetal growth restriction.
VII) Twins
VII) Twins monozygotic twins who share a placenta will not develop equally because one twin
will receive more nourishment via the placenta than the other twin does. this is known as fetal growth restriction.
monozygotic twins come from the same fertilized egg they share identical genetic material.
they can only be same-sex if splitting occurs very late and is incomplete, conjoined
twins result.
VII) Twins conjoined twins are monozygotic twins who are joined at some region of their bodies.
they are classified by the area where the attachment is located: Terata Catadidyma refers to twins joined in the lower portion of their body, or they
may appear to be two bodies on top and one body on the bottom. Pygopagus - back-to-back, joined at the rump Ischiopagus - joined sacrum to sacrum Dicephalus - one body with two separate heads
Diprosopus - single body and head, but bearing two faces
VII) Twins Terata Anadidyma refers to twins with one single upper body with a double
lower half or twins who are connected by a single body part. Cephalopagus - connected at the head Syncephalus - connected in the facial region Cephalothoracopagus - connected in the facial region and at the thorax Dipygus - one upper body with two lower bodies (including the abdomen,
pelvis and legs)
VII) Twins Terata Anacatadidyma refers to
twins who are joined somewhere along the midsection of the body.
Thoracopagus - joined at the chest; may share a single heart or have some cardiac connection; some organs in the abdominal region may be malformed
Omphalopagus - joined at the chest
Rachipagus - back-to-back, joined along the spine above the sacrum