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Chapter 28
Pregnancy and Development
90
Anatomy
Undergraduate 2
05/09/2012

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Term
What is the preembryo?
Definition
conceptus from fertilization until it is two weeks old
Term
What is the embryo?
Definition
conceptus during the third through the eighth week
Term
What is teh fetus?
Definition
conceptus from the ninth week through birth
Term
For how much time is the oocyte viable for?
Definition
24 hours
Term
For how long is sperm viable for?
Definition
72 hours
Term
What is an ovulated oocyte encapsulated by?
Definition
corona radiata and zona pellucida
Term
After sperm binds to the zona pellcuida what happens?
Definition
it undergoes the acrosmal reaction
Term
What is the acrosomal reaction?
Definition
enzymes are rleleased near the oocyte, hundres of acrosomes release their enzymes to digest the zona pellcuida
Term
What is the role of the beta protein after sperm makes contact with the oocyte's membrane?
Definition
finds and binds to receptors on the oocyte membrane
Term
What is the role of the alpha protein after sperm makes contact with the oocyte's membrane?
Definition
causes sperm to insert into the membrane
Term
What are the two mechanisms that ensure monospermy?
Definition
fast block, slow block
Term
What is the fast block?
Definition
membrane depolarization prevents sperm from fusing with the oocyte membrane
Term
What is the slow block?
Definition
zonal inhibiting proteins destroy sperm receptors, cause sperm already bound to receptors to detach
Term
What happens to the secondary oocyte after entry of the sperm?
Definition
meiosis II is completed, casts out second polar body
Term
What happens after the second polar body is cast out?
Definition
ovum nucelus swells, and teh two nuclei approach each other
Term
What are teh two nuclei called when fully swollen?
Definition
pronuclei
Term
What is fertilization?
Definition
when the pronuclei come together
Term
Preembryonic Development: First cleavage
Definition
two daughter cells produced called blastomeres
Term
Preembryonic Development: Morula
Definition
16 or more cell stage (72 hours old)
Term
Preembryonic Development: 4/5th day
Definition
preembryo consists of 100 or so cells, (blastocyst)
Term
Preembryonic Development: Blastocyst
Definition
fluid filled hollow sphere
Term
What is the blastocyst composed of?
Definition
single layer of trophoblasts, an inner cell mass
Term
What do trophoblasts take part in?
Definition
placenta formation
Term
What does the inner cell mass become?
Definition
embryonic disc
Term
What are the steps to embryo?
Definition
implantation, placentation, gastrulation, organogenesis, neuralization
Term
When does implantation begin?
Definition
6-7 days after ovulation when the trophoblasts adhere to a properly prepared endometrium
Term
What happens after the blastocyst is implanted?
Definition
covered over by endometrial cells
Term
When is implantation completed?
Definition
by the 14th day of ovulation
Term
How is the viability of the corpus luteum maintained by?
Definition
hCG made by developing embryo trophoblasts
Term
What is another role of hCG?
Definition
prompts the corpus luteum to continue to secrete progesterone and estrogen
Term
What is the chorion?
Definition
developed from trophoblasts after implantation, continues this hormonal stimulus
Term
What is the placenta doing between the second and third month?
Definition
assumes the role of progesterone and estrogen production, providing nutrients and removing wastes
Term
What tissues does placenta formation develop from?
Definition
embryonic trophoblastic tissues, maternal endometrial tissues
Term
What other hormones does the placenta secrete?
Definition
human placental lactogen, human chorionic thyrotropin, relaxin
Term
How long does it take the placenta to be fully formed and functional?
Definition
by the end of the 3rd month
Term
What is the role of human placental lactogen?
Definition
initiate milk production
Term
What is the role of human chorionic thyrotropin?
Definition
kick up metabolism
Term
What is the role of relaxin?
Definition
cause the pelvic ligature to relax
Term
What are teh embryonic membranes?
Definition
amnion, yolk sac, allantois, chorion
Term
What is the amnion?
Definition
transparent membrane filled with amniotic fluid
Term
What is the role of the amnion?
Definition
provides a buoyant environment that protects the embryo, helps maintain a constant homeostatic pressure
Term
Where does amniotic fluid come from?
Definition
maternal blood and later fetal urine
Term
What is the yolk sac?
Definition
hypoblast cells that form a sac on the ventral surface of the embryo
Term
What is the role of the yolk sac?
Definition
forms part of the digestive tube, produces earliest blood cells and vessels, source of primordial germ cells, source of nutrition in some animals
Term
What is the allantois?
Definition
small outpocketing at the caudal end of the yolk sac
Term
What is the role of the allantois?
Definition
structural base for the umbilical cord, becomes part of the urinary bladder
Term
What is the chorion?
Definition
helps form the placenta
Term
What is the role of the chorion?
Definition
encloses the embryonic body and all other membranes
Term
What is the role of gastrulation?
Definition
set the stage for organogenesis
Term
What happens to the embryonic disc during the 3rd week?
Definition
two-layered embryonic disc becomes a three-layered embryo
Term
What are teh primary germ layers?
Definition
ectoderm, mesoderm, endoderm
Term
What is the primitive streak?
Definition
raised dorsal groove that establishes the longitudinal axis of the embryo
Term
What happens to the first cells that begin to migrate into the primitive streak?
Definition
form the endoderm
Term
What happens to the cells that follow the first cells that begin to migrate into the primitive streak?
Definition
push laterally between the cells forming the mesoderm
Term
What happens to the cells that remain on the embryo's dorsal surface?
Definition
form the ectoderm
Term
What is the notochord?
Definition
rod of mesodermal cells that serves as axial support
Term
What is the role of teh primary germ layers?
Definition
serve as primitive tissues from which all body organs will derive
Term
What does the ectoderm develop into?
Definition
forms structures of the nervous system and skin epidermis
Term
What does the endoderm develop into?
Definition
forms epithelial linings of the digestive, respiratory, and urogential systems
Term
What does the mesoderm develop into?
Definition
forms all other tissues
Term
BY what week are all organ systems recognizable?
Definition
8th
Term
What is the first event of oragnogenesis?
Definition
neurulation
Term
What is neurolation?
Definition
gives rise to the brain and spinal cord
Term
What does teh notochord thickening over the ectoderm form?
Definition
neural plate
Term
What happens to the neural plate?
Definition
folds inward as a neural groove with prominent neural folds
Term
By the 22nd day, neural folds fuse into a _______
Definition
neural tube, which pinches off into the body
Term
What does the anterior end of of the neural tube become?
Definition
the brain
Term
What happens to the rest of the neural tube?
Definition
spinal cord
Term
What happens to the rest of the neural tube?
Definition
spinal cord
Term
What does the associated neural crest give rise to?
Definition
cranial, spinal, and sympathetic ganglia
Term
WHat does embryonic folding begin with?
Definition
lateral folds
Term
After lateral fords have formed what appears next?
Definition
head and tail folds
Term
What forms the epithelial lining of the GI tract?
Definition
endoderm tube
Term
After formation the epithelial lining of the GI tract forms what happens?
Definition
Organs of the GI tract become apparent,and oral and anal openings perforate (open)
Term
What else does the endoderm form?
Definition
epithelium linings of the hollow organs of the digestive and respiratory tracts
Term
Specialization of the mesoderm: FIrst evidence
Definition
appearance of the notochord
Term
What are the three mesoderm aggregates that appear lateral to the notochord?
Definition
sclerotome, dermatome, myotome
Term
What is the sclerotome?
Definition
produce the vertebrae and ribs
Term
What is teh dermatome?
Definition
help forms the dermis of the skin on teh dorsal part of the body
Term
What is the myotome?
Definition
form the skeletal muscles of the neck, trunk, and limbs
Term
What does the intermediate mesoderm form?
Definition
gonads and kidneys
Term
What does the somatic mesoderm form?
Definition
dermis of the skin in the ventral region, parietal serosa of the ventral body cavity, bones, ligaments and dermis of the limbs
Term
What does the splanchnic mesoderm form?
Definition
heart and blood vessels, most connective tissues of the body
Term
WHat anatomical changes are present during pregnancy?
Definition
chadwick's sign, breast enlarge/areolae darken, uterues expands
Term
What is chadwick's sign?
Definition
vagina develops a purplish hue
Term
Why is lordosis common in pregnant women?
Definition
change of body's center of gravity
Term
What does relaxin relax?
Definition
pelvic ligaments and pubic symphysis
Term
By how much does blood volume increase during pregnancy?
Definition
25-40%
Term
What causes contractions as birth nears?
Definition
oxytocin and prostaglandins
Term
What are the five signs an infant's status is based on?
Definition
heart rate, respiration, color, muscle tone, reflexes
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