Embryology Flashcards
What week of embryogenesis does gastrulation occur?
2-3 weeks
What week of embryogenesis does organogenesis occur?
3-8 weeks
Cleavage
Day 1-3 ball of cells (blastomere) stays the same size with subsequent divisions
Cells are totipotent
Compaction
Blastomere maximize their contact with each other
Forms Morula
Blastocyst
Forms on day 4
Two cell lineages trophoblast and inner cell mass
Cavity is called blastocoel
Zona Pellucida
Forms around day 5
Acts as barrier from other sperm
Acts as an immunological barrier
Holds the blastomeres together
Two layers of the trophoblast
Synctiotrophoblast creates cavity in endometrium
Cytotrophoblast basal cells that nourish synctio
Formation of bilaminar disc
Occurs around day 8
Create epiblast, hypoblast, amniotic cavity
Cells above the epiblast layer are called the amnioblast
1st, 2nd and 3rd lineage decisions
- Compaction forming blastocyst day 3
- Formation of bilaminar disc epiblast and hypoblast cell lineages day 8
- Formation of trilaminar germ disc week 3
Complete implantation occurs around?
Week 3
Formation of villus capillaries
Transformation of connecting stalk into umbilical chord
Formation of functional placenta
Primitive streak grows
Caudal to rostral
Notochord grows
Rostral to caudal with regression of primitive streak.
Major body axis are established vai
Gastrulation
Formation of the primitive streak is facilitated by
Secretion of NODAL in the caudal portion of the epiblast cells
Secretion of NODAL inhibitor in the raustral portion of the hypoblast cells
Differentiation
Subdivision of germ layers
Morphogenesis
Closure of the body cavities
Neural Tube Grows
On top of notochord in rostral to caudal fashion
Neural Plate
Neural Fold
Neural Tube
Paraxial Mesoderm Forms
Somites
Intermediate Mesoderm forms
urinary system and major portions of the reproductive system
Somatic Mesoderm
Also called parietal mesoderm: dermis of the lateral and ventral body wall and limbs
Visceral Mesoderm
Also called splanchnic mesoderm: muscular and connective tissue layers of the gut.
Induction
Interactions between tissues lead to a change in the course of development of one or both tissues
Malformations
Morphological defects of an organ
i.e. thalidamide babies
Disruptions
Alteration of already formed structures by destructive processes
i.e. ring consriction of limbs caused by amniotic bands
Deformations
abnormal form, shape or position of an organ by mechanical forces
i.e. club feet due to too little amniotic fluid
Time period of highest risk of teratogenesis
5 weeks
Syndrome
A well-characterized group of anomalies that occur together in a predictable manner presumably due to a single underlying etiology
Association
a group of anomalies that occur more frequently together than by chance, but the cause is unknown
Sequence
a group of related anomalies that stem from a single initial major anomaly that alters the development of related tissues.
