Repro IV: Pregnancy and Development Flashcards
What are the 3 stages of gestation and how long do they last?
- germinal stage (1st 2 weeks)
- embryonic stage (weeks 3-8)
- fetal stage (weeks 9-38)
What happens during the germinal stage of gestation?
zygote becomes morula which becomes a blastocyst which then enters the uterus
once blastocyst is implanted it is called an embryo
What happens during the embryonic stage of gestation?
embryo develops 3 primary tissue layers and develops beginnings of organs and organ system
embryo becomes fetus at end of 8th week
What are the 3 primary germ layers?
ectoderm
mesoderm
endoderm
What two organs/organ systems develop from the ectoderm?
all nervous tissue
epidermis of skin
What organs/organ systems develop from the mesoderm?
cartilage, bone, connective tissues
skeletal, cardiac, smooth muscles
blood and lymphatic vessels
epithelium of gonads
What organs/organ systems develop from the endoderm?
epithelium of digestive tract
epithelium of respiratory system
epithelium of thyroid, liver, pancreas
epithelium of bladder
When does the placenta form>
during 3rd month of gestation
What does the placenta develop from?
embryonic chorion and uterine tissue
What are the 3 functions of the placenta?
- site of nutrient, gas, and waste exchange
- secretes hormones that maintain pregnancy
- barrier to microorganisms, except some viruses
What viruses and substances can pass through the placenta?
AIDS, measles, chickenpox, poliomyelitis, encephalitis
drugs, alcohol
What structure connects the embryo and the placenta?
umbilical cord
What vessels does the umbilical cord contain?
two umbilical arteries
one umbilical vein
What is the maternal portion of the placenta?
decidua basalis of uterus
contains maternal vessels
What is the fetal portion of the placenta?
chorionic villi of chorion
contains umbilical cord vessels and amnion, fetal blood vessels
What hormone does the chorion of the embryo produce?
human chorionic gonadotropin (hCG)