Download Pregnancy PowerPoint

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Cell encapsulation wikipedia , lookup

Somatic cell nuclear transfer wikipedia , lookup

Plant reproduction wikipedia , lookup

Umbilical cord wikipedia , lookup

Birth defect wikipedia , lookup

Sexual reproduction wikipedia , lookup

Drosophila embryogenesis wikipedia , lookup

Fetus wikipedia , lookup

Human embryogenesis wikipedia , lookup

Prenatal development wikipedia , lookup

Transcript
Biology 12
Unit 2: Reproduction and
Development
Pregnancy
Fertilization
• Fertilization takes place in the fallopian tube
• When the sperm enters the egg, the ovum undergoes
meiosis II
• if an ovum is fertilized, the levels of estrogen and
progesterone must remain high to maintain the
endometrium and prevent further secretions of FSH
• as the fertilized ovum develops it secretes chorionic
gonadotropin (HCG) which maintains the corpus luteum
until the placenta begins to secrete its own progesterone as
it develops
Clip
Early Development
• The fertilized ovum is called a zygote
• The zygote travels down the fallopian tube, it
continues to divide, becoming a hollow ball of
cells (blastocyst) by the time it reaches the uterus.
• Prior to implantation, the blastocyst undergoes
gastrulation.
• Gastrulation and cell migration set up the three
germ layers - endoderm, ectoderm, and mesoderm
• Implantation is when the zygote attaches to the
endometrium.
• As the embryo continues to grow by mitosis, part of the
outer layer of cells (chorionic villi of the chorion)
contribute the fetal portion of the placenta
• The endometrium forms the maternal side of the placenta
• A layer of tissue inside the chorion forms a fluid
filled membrane called the amnion.
• A third membrane called the allantois provides the
blood vessels to the placenta.
• The embryo is attached to the placenta by the
umbilical cord.
Early Development
Clip
Clip
Early Human Development
Two weeks
after
conception.
Three weeks after
conception.
Five weeks after
conception.
Eight weeks
after
conception.
(Human?)
Twelve weeks
after
conception.
First Trimester
– Zygote becomes embryo when implanted
– Amnion, chorion, and allantois develop early
– Embryo grows to about 5.7 cm by end of
trimester.
– Heart, limbs , and brain have
begun to develop
– By nine weeks the embryo is
called a fetus
– The sucking reflex is present
Second Trimester
– The fetus will begin to kick
– All organ systems will develop and continue to
mature
– Cartilage is replaced with bone
– Hair and eyelids form
– With modern medicine, some fetuses can
survive after only 22 weeks.
– The longer the pregnancy the greater the
chances for survival.
Third Trimester
– The last trimester is marked by rapid growth
and final maturation of the organs.
– The fetus will grow to over 50 cm and up to 4
kg.
– 9 months, 38 weeks, or approximately 266 days
after implantation labor begins
Time of Birth.
Birth
– Progesterone levels drop near the end of
pregnancy. This may trigger labor.
– Relaxin which is produced by the placenta
causes the ligaments of the pelvis to relax.
– Oxytocin produced by the anterior pituitary
causes strong uterine contractions.
– Oxytocin is controlled by a positive feedback
loop.
Lactation
– Lower levels of progesterone after labor allow prolactin
to be released from the anterior pituitary.
– Prolactin stimulates mammary glands to produce breast
milk.
– To let down the milk, oxytocin must be released by the
pituitary
– During the first few days colostrum is let down instead
of milk. Colostrum does not contain fat
– Milk contains all substances the growing infant needs
including antibodies