Embryology Flashcards
Zygote
One cell but 2n (made up of female pronucleus and male pronucleus)
When does the morula form and what is it made of
Day 3/4
Morula is made up of blastomeres (about 16)
When does blastocyst form
Day 5
When does formation of primitive germ layers take place
3rd week
When does organogenesis take place
Embryonic period
2-8 weeks
When is the fetal period
9-38 weeks
Growth differentiation and maturation
Totipotent pluripotent multipotent unipotent
What makes up the blastocyst
Embryoblast (inner cell mass) and trophoblast (outer)
What needs to be present in uterus lining for successful implantation of blastocyst
Progesterone
What lines the inner wall of the blastocyst after implantation
Inner cystotrophoblast
Outer synctiotrophoblast
What forms the bilaminar disc
Hypoblast
Epiblast
What is the histology and location of the hypoblast and epiblast
Hypoblast cuboidal and ventral
Epiblast columnar and dorsal
What is the function of the placenta
Life support,
Provides oxygen and nutrients removes waste
Circulations of baby and mother blood do not mix, separated by thin barrier
Chorionic villus sampling
Chorionic villus sampling may be used for genetic and chromosome testing in the first trimester of pregnancy . Here are some reasons that a woman might elect to undergo CVS:
Previously affected child or a family history of a genetic disease, chromosomal abnormalities, or metabolic disorder
Maternal age over 35 years by the pregnancy due date
Risk of a sex-linked genetic disease
Previous ultrasound with questionable or abnormal findings
Abnormal cell-free DNA test
Difference between identical and fraternal twins at the trophoblast stage
Identical twins are from the same trophoblast fraternal twins are from two different trophoblasts
How does the trilaminar embryonic disc form
Ectoderm - leftover Epiblast
Mesoderm - Epiblast cells that migrated inwards
Endoderm - Epiblast cells that replaced Hypoblast layer
When does gastrulation take place
Day 15 , start of week 3
First organ to be developed
CNS
What are the derivates of the ectoderm germ layer
Skin
ENAMEL
Mucous membranes
CNS
Derivatives of the mesoderm
Most connective tissues (dermis, tendons, cartilage, bone)
Muscle
Blood vessels
Heart
Kidney
Reproductive system
Derivatives of the endoderm
Thyroid
Parathyroid
Respiratory
GIT
Irogenital (some)
When does spontaneous abortion occur
First. 2 weeks
First trimester period
Week 3-12
Greatest sensitivity
Ectomesenchyme importance in dentistry
Derivatives are dentine cementum pulp PDL jaw bones
Most of the mesenchyme in the head
PNS
What is ectomesenchyme
Another name for neural crest
Very important for development of head
Derived from ectoderm but has characteristics of mesenchyme
Where does primitive streak extend from
Formation of primitive node , primitive node and primitive pit extends towards the caudal end forming the primitive groove
(cranial end of primitive streak expands)
What does dental papilla cells differentiate into?
What does IEE cells differentiate into?
Dental papillae cells into odontoblasts
IEE cells differentiate into ameloblasts
Stomodaeum
Primitive mouth
What forms the enamel organ and what forms the dental papilla
Ectoderm cells into dental lamina into enamel organ
Ectomesenchyme condensation into dental papilla
What is the name of the point where EEE and IEE meet
Cervical loop
(Extends apically in root formation)
4 cells of enamel organ
Stratum intermedium
IEE
EEE
Stellatereticulum
What is the Stellate reticulum function
Hydrophilic, to help maintain space for developing crowns
Which comes first? Dentine genesis or amelogenesis?
Dentinogenesis
What differentiates into odontoblasts and ameloblasts
Dental papilla cells into odonto
IEE into ameloblasts
Enamel proteins
Enamelins
Ameloblastins
Amelogenins (90%)
Describe secretory and maturation phase of amelogenesis
30% mineralised then 96% mineralised when matrix proteins are removed
What is the epithelial attachment important for
Cells that generate junctional epithelium (hemidesmosomes)
Which way does the nucleus migrate during the tome’s processes
Basally (tomes process at the apical side)
Which direction does the cervical loop move in root formation
Apical
HERS (hedwig epithelial root sheath)
2 layers (IEE AND EEE)
Cell rests of malassez
Remnants when HERS degenerates
No function but can cause cysts/Tumours
What stimulates cementoblasts in root formation
When Ectomesenchyme cells comes in contact with dentine, differentiate into cementoblasts and starts producing cementum
