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BIO202 - Ch 28 - Pregnancy & Development - Marieb/Hoehn - RioSalado - AZ

Conceptus Developing offspring during pregnancy
gestation period Last menstral period to birth - 280 days
embryonic period fertilization to week 8
fetal period week 9 to birth
Sperm fertilizes the __ oocyte. ovulated secondary oocyte
Fertilized egg zygote - first cell of new individuals
What capacitates a sperm so it can fertilize? Cervical mucus, uterus, uterine tube & secretions of female tract - removes cholesterol of acrosomal membrane.
Ovulated oocyte surrounded by? Corona radiata & zona pellucida - both must be reached by sperm.
Sperm receptor on egg. ZP3 glycoprotein in zona pellucida.
Acrosomal reaction Breakdown of acrosomal membrane & plasma membrane to release acrosomal enzymes to digest hole in zona pellucida.
What occurs to block polyspermy? A corticle reaction - calcium surge that spills enzymes - zonal inhibiting proteins (ZIPs) - that destroy sperm receptors & prevent further sperm entry.
What do sperm lose when it enters oocyte? Tail, midpiece, & centrosome in midpiece that holds microtubules.
What prompts secondary oocyte to complete meiosis 2? Calcium surge due to sperm penetration - forms ovum nubleus to 2nd polar body.
Female pronucleus Ovum nubleus after penetration of ovum & awaits fusion with male pronucleus.
When is the true moment of fertilization? When female pronucleus & male pronucleus combine as their membranes rupture & their chromosomes are released - zygote formed.
cleavage Phase of rapid miotic cell division in zygote without intervening growth periods - blastocyst formed - 2 identical cells.
morula At 72 hours - berry-shaped cluster of 16+ cells
Why is multicellular blastocyte only slightly larger than single-celled zygote? Virtually no growth occurs between successive divisions of cleavage.
Trophoblast cells help form? placenta
Inner cell mast in blastocyst becomes? Embryonic disk & then embryo
What surging hormones in blood repare endometrium for implantation? Estrogens & progesterone
Which cells of blastocyte adheres to endometrium? Trophoblast cells overlying inner cell mass.
Period of implantation 5 days & complete usually by 12th day after ovulation.
Viability of corpus luteum is maintained by __. hCG - human chorionic gonadotropin - LH-like hormone secreted by trophoblast cells. Keeps corpus luteum secreting progesterone & estrogen.
What do pregnancy tests test for? Antibody tests that detect hCG.
Placentation Placenta formation - chorion -> chorionic villi + decidua basalis = placenta.
What does placenta do? Nutritive, respiratory, excretory, & endocrine organ.
What are the mother/embryo barriers? Chorionic villi & endothelium of embryonic capillaries.
Levels of estrogen & progesterone __ during pregnancy, while hCG levels __. increase-decline
The blastocyst becomes a __. gastrula - 3 primary germ layers form & extraembryonic membranes develop.
Extraembryonic membranes amnion, yolk sac, allantos, & chorion
amnion Amniotic sac that fills with amniotic fluid & surrounds embryo.
yolk sac Primitive gut - hangs from ventral surface of embryo - forms digestive tube & earliest blood cells & vessels.
allantois Structural base for umbilical cord - links embryo to placenta & becomes part of urinary bladder.
The chorion encloses __. embryonic body & all other membranes.
Primary germ layers. ectoderm, mesoderm, & endoderm
gastrulation 2-layered embryonic disk - transforms into 3-layered embryo - week 3
The primitive streak establishes __. the longitudinal axis of embryo.
Most inferior germ layer endoderm
First axial support of embryo notochord - rod of mesodermal cells
Ectoderm forms? "Outer skin" - nervous system & epidermis.
Endoderm forms? "Inner skin" - epithelial lining of digestive, respiration, & urogenital system, & glands.
Mesoderm forms? Skeleton & muscles of body.
Organogenesis Formation of body organs & systems.
1st major even of organogenesis Neurulation - ectoderm that produces brain & spinal cord over notochord.
Anterior end of neural tube becomes? Brain & rest becomes spinal cord.
somites Paired mesodermal blocks that hug notochord on either side - 40 pairs - becomes verterbra & rib, dorsal dermis & muscles of neck, trunk, & limbs.
Splanchnic Mesenchymal cells form heart, blood vessels, & CT of body.
Somatic mesoderm Form ventral dermis, parietal serosa, limbs, bones, ligaments, & limb dermis.
coelom Ventral body cavity - forms it from lateral mesodermal layers.
ductus venosus Venous shunt that bypasses liver sinusoids.
Fetus' hepatic veins & ductus venosus empty __. Into the inferior vena cava where placental blood mixes with deoxygenated blood.
Where does fetus' vena cava convey blood? R-atrium
Foramen ovale Allows fetal blood to pass from right atrium to left atrium - opening in interartrial septum.
ductus arteriosus Transfers blood to aorta & bypasses pulmonary circuit.
teratogens Factors that produce congenital abnormalities - alcohol, drugs, measles.
Chadwick's sign Vagina develops purplish hue as it engorges with blood.
chloasma mask of pregnancy - pigmentation
parturition birth - 280 days from last menstral period
What hormone events induce labor? Estrogen from placenta induces oxytocin receptors on uterus (myometrial cells) - this antagonizes progesterone - fetal cells produce oxytocin & placenta releases prostaglandins - stimulates muscle contraction - positive feedback mech.
Both __ & __ are essential for initiating labor. Oxytocin & prostaglandins
Vertex presentation head-first
dystocia difficult birth due to malformed pelvis.
5 Apgar signs heart rate, respiration, color, muscle tone, & reflexes.
What causes baby's first breath? CO2 build up - acidosis - excites respiratory centers in brain.
What hormone causes let-down reflex? oxytocin
Created by: Ladystorm