FOM 6.2.1 Flashcards
What is first step of gastrulation (the creation of the trilaminar germ disc)?
Creation of the primitive streak
The primitive streak is form via what process of the epiblast?
Invagination
What are the two possible layer destinations of cells that pass through the primitive streak of the epiblast?
Endoderm (ventral) Mesoderm
If a cell doesn’t pass through the primitive streak and remains in the epiblast, what is it fate in terms of layer formation?
Ectoderm (dorsal)
During which day of development, does primitive streak formation occur?
~ Day 14
Where is the primitive node located in relation to the primitive streak?
Anterior margin of streak
When does the primitive steak cease in existence?
4th week
What is the organizer of gastrulation (specifically caudal organization)?
Primitive node
After epiblast cells pass through the invagination, describe their dispersion pattern? What influences their movement?
Early cells move upward to form notochord (prenotochordal cells) After that cells move lateral and cranial, influenced by FGF signaling
What is the fate of the hypoblast? Which membrane and extra-embryonic layers?
Heuser’s membrane. Extra-embryonic endo- and mesoderm
What is the name of the schematic that illustrates the pathway of epiblast cells that pass through the primitive streak? Draw and label layers.
Fate map
Draw the flow chart of the formation of embryonic germ layers starting with the blastocyst.
(Pic)
Describe the directionality of notochord formation.
Cranial to caudal (head to tail)
What lies cranial of the the notochord?
Prechordal mesoderm (future brain and CNS)
The notochord plays a vital role in the induction of what embryonic structure?
Neural plate -> neural tube
When the neural tube is formed, describe the position of the notochord relative to the neural tube.
Ventral
How do the prenotochordal cells interact with the hypoblast?
Initially intercalate; The hypoblast is replaced with the endoblast causing the notochordal plate to exist in two layers (meso and endo). The endoderm will close back up when notochord forms b/t mesoderm
What are the three body axes?
Left-right, dorsal-ventral, anterior-posterior
What acts the second signaling region in the head?
AVE (Anterior Visceral Endoderm)
What are the two main purposes of the the Anterior Visceral Endoderm (AVE)?
Head formation & inhibition of PS (primitive streak) in head
What molecule is involved with ventralizing the mesoderm?
Bone morphogenetic protein 4 (BMP4)
What molecules secreted by the node and prechordal mesoderm acts to dorsalize cranial mesoderm (eventually leads to formation of notochord (NC) and paraxial mesoderm?
Chordin, Noggin, Follistatin
What is the dorsalizing gene of the middle and caudal embryo?
Brachyury (T) gene
Inappropriate regulation of expression of what leads to conjoined twins?
Goosecoid (dorsalizes head mesoderm)
Absence of Brachyury (T) gene leads to what condition?
Caudal dysgenesis (sirenomelia)
What molecule establishes left-sidedness? What molecule eventually overrides this signal to establish right-sideness
FGF8, SHH (sonic hedgehog)
High doses of alcohol during pregnancy can to what? It is characterized by craniofacial malformations.
Holoprosencephaly
What is situs inversus?
Transposition of viscera in thorax and abdomen
Remnants of primitive streak (active when it isn’t supposed to be) leads to what condition?
Sacrococcygeal Teratoma
Decribe primary, secondary, tertiary villus.
pri: 2 trophoblast cell layers sec: extraembryonic mesoderm core tert: capillaries present
