Human Development Flashcards
The developing embryo becomes a solid ball of 16+ cells called…
a morula (day 4)
The ball of cells hollows out to form a ______ on day 5.
blastocyst
Late blastocyst (day 10)
pre-embryo with the embryonic disk, two layers of cells that become the embryo proper
Gastrula (day 16)
Embryo with three primary germ layers
What are the three primary germ layers?
ectoderm(outer), mesoderm(middle), endoderm(inner)
Endoderm forms…
Digestive tract, lungs, liver, and pancreas
Mesoderm forms…
muscle, connective tissue(bone), internal reproductive organs, and kidneys
Ectoderm forms…
Nervous system and skin
Supportive structures
structures that support and protect the embryo
Umbilical cord
has stem cells
Amniotic sac
- fluid maintains constant temperature and pressure
- contains fetal urine and cells
Placenta (fully formed at 10 weeks)
- secretes hormones that maintain pregnancy
- sends nutrients to fetus
Multiple Births
Dizygotic twins (fraternal)
Monozygotic twins (identical)
When does oogenesis start?
when the neural tube develops
Spina bifida
Neural tube defect
By 4 weeks…
Heart, CNS, arms and legs start to extend, immature lungs and kidneys start to develop
By 7 weeks…
Large head, eyes opened by no lids, cartilage skeleton forms
By week 8…
Prenatal human has tiny versions of all structures that will be present at birth
A prenatal human is considered a _____ for the first 8 weeks.
embryo
Why are the first 8 weeks so important?
Critical period
What is the critical period?
The time during pregnancy when teratogens have the most effect on a prenatal human.
What is a prenatal human considered from 9 weeks till birth?
fetus
During fetal period…
body proportions approach those of a newborn, bone replaces soffter cartilage, nerve and muscle functions become coordinated
By 12 weeks…
sucks thumb, kicks, makes fists and faces, and has the beginnings of teeth
18 weeks…
vocal cords formed
Final trimester…
fetal brain cells link into networks as organs elaborate and grow, and fat fills out the skin
Last…
digestive and respiratory system matures
Teratogens
chemical or other agents that cause birth defects
3 categories of teratogens
- Vitamins
- Viruses
- Drugs
Drug teratogens
Thalidomide- limb defects
Alcohol- fetal alcohol syndrome (FAS)
Accutane- birth defects, miscarriage
Cocain- stroke, nervous system
Vitamin teratogens
Folic acid deficiency- neural tube defects
Vitamin C excess- immune effects
Virus teratogens
Rubella, herpes, HIV, hepatitis B
Thalidomide
Many mothers took during early stages of pregnancy to help with morning sickness
FAS
Learning and mental disabilities, behavior problems, lack social and communication skills, growth slowed before and after birth
