Embryonic Development (lecture) Flashcards
What is fertilization?
- When nucleus of sperm enters egg
- acrosome: acrosomal enzyme breaks down zona pellucida of egg
- fertilization membrane -> no longer penetrable
What is a blastocyst
- form of the egg that gets implanted
- human chorionic gonadotropin
- released when implanted
- Fx: maintains corpus luteum: maintains uterine lining
What is the outer layer of a blastocyst?
Trophoblast
- becomes placenta
What is the inner portion of a blastocyst?
Inner cell blast
- becomes embryo
- totipotent stem cells
What is implantation?
Trophoblast cells invade endometrium -> form chorionic villi -> become chorion -> placenta
What is placenta previa?
Placenta blocking the cervix. Requires c-section birth
What is different with fetal blood circulation?
Diverts blood away from lungs since there is no breathing yet
Functions of ductus arteriosus and foramen ovale of the atria. What do they develop into outside of the womb?
Ductus arteriosus: Bypasses pulmonary circuit to the aorta. Connects the aorta and pulmonary trunk. becomes ligamentum arteriosus
Foramen Ovale of the Atria: Shunts blood from the R. atria to the L. atria. Develops into fossa ovale
Where does the umbilical vein go to?
Through liver into IVC
Where does the umbilical artery go to?
Internal iliac arteries
What is gastrolation
inner cell mass forms 3 primary germ layers:
- ectoderm
- mesoderm
- endoderm
Amnion
- contains amnionic fluid. ruptures during labor (“water breaking”)
- amniocentesis; allows genetic testing for baby
What is ontogeny recapitulates phylogeny?
- embryonic development proves evolution
- all vertebrates look identical in early stages of development
Organogenesis
Two major processes:
- morphogenesis: formation of 3D shape of organ
- Differentiation: specialization of stem cells to differentiated cells
How does organogenesis occur?
Through localization signals
1. chemical gradient
2. induction: physical contact between cells
Induction of chicken teeth
e.g. injected mouse mesoderm cells into chicken embryo = induced chicken teeth
What is neurulation?
Example of induction
Process of nervous system formation. Complete after 18 yo
What is spina bifida?
neural tube doesn’t close posteriorly. results in paralysis from waist down
What is ancephaly?
Neural tube doesn’t close anteriorly. Results in no brain formation - ends at brainstem
Describe the formation of neural crests
- PNS
- melanocytes
What are Mongolian spots?
collection of crest cells at buttocks
- common in Asian babies
What is a unique structure identified in 4-week-old embryos?
Branchial Arches
- make gills in fish
- make bones in humans
Somites
become vertebrae and other repeating structures
Limb bud
from chemical gradient and conduction
Limb development
- controlled apoptosis between fingers
- incorrect development causes webbing between fingers
When does a human embryo become a fetus?
Week 10
Facial development
morphological movement
Fetal alcohol syndrome
- Drinking alcohol during first 10 weeks of development
Sx: mental handicap
Signs:
- eyes far apart
- flat nose bridge
- no philtrum
- wide mouth
Cleft lip/ cleft palate
2 maxilla or palatine bone don’t meet in the middle
Reproductive structure development
starts at six weeks
-external genitalia
What is hypospadias?
urethra doesn’t form in middle of penis
Childbirth
- 40 weeks total
- mother’s Neurohypophysis (PPG) makes oxytocin
- oxytocin is on a positive feedback loop
What is the role of oxytocin during childbirth?
- causes contractions of smooth muscle of the uterus
Labor Function:
1. cervical dilation
2. baby expulsion
3. placenta expulsion
Indication for cesarean section birth
- transverse/breeched presentation
- placenta abruptio
- placenta previa
What is situs inversus?
Organs develop mirrored flipped
