FOM 6.2.1

Question 1

What is first step of gastrulation (the creation of the trilaminar germ disc)?

Answer 1

Creation of the primitive streak

Question 2

The primitive streak is form via what process of the epiblast?

Answer 2

Invagination

Question 3

What are the two possible layer destinations of cells that pass through the primitive streak of the epiblast?

Answer 3

Endoderm (ventral) Mesoderm

Question 4

If a cell doesn’t pass through the primitive streak and remains in the epiblast, what is it fate in terms of layer formation?

Answer 4

Ectoderm (dorsal)

Question 5

During which day of development, does primitive streak formation occur?

Answer 5

~ Day 14

Question 6

Where is the primitive node located in relation to the primitive streak?

Answer 6

Anterior margin of streak

Question 7

When does the primitive steak cease in existence?

Answer 7

4th week

Question 8

What is the organizer of gastrulation (specifically caudal organization)?

Answer 8

Primitive node

Question 9

After epiblast cells pass through the invagination, describe their dispersion pattern? What influences their movement?

Answer 9

Early cells move upward to form notochord (prenotochordal cells) After that cells move lateral and cranial, influenced by FGF signaling

Question 10

What is the fate of the hypoblast? Which membrane and extra-embryonic layers?

Answer 10

Heuser’s membrane. Extra-embryonic endo- and mesoderm

Question 11

What is the name of the schematic that illustrates the pathway of epiblast cells that pass through the primitive streak? Draw and label layers.

Answer 11

Fate map

Question 12

Draw the flow chart of the formation of embryonic germ layers starting with the blastocyst.

Answer 12

(Pic)

Question 13

Describe the directionality of notochord formation.

Answer 13

Cranial to caudal (head to tail)

Question 14

What lies cranial of the the notochord?

Answer 14

Prechordal mesoderm (future brain and CNS)

Question 15

The notochord plays a vital role in the induction of what embryonic structure?

Answer 15

Neural plate -> neural tube

Question 16

When the neural tube is formed, describe the position of the notochord relative to the neural tube.

Answer 16

Ventral

Question 17

How do the prenotochordal cells interact with the hypoblast?

Answer 17

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

Question 18

What are the three body axes?

Answer 18

Left-right, dorsal-ventral, anterior-posterior

Question 19

What acts the second signaling region in the head?

Answer 19

AVE (Anterior Visceral Endoderm)

Question 20

What are the two main purposes of the the Anterior Visceral Endoderm (AVE)?

Answer 20

Head formation & inhibition of PS (primitive streak) in head

Question 21

What molecule is involved with ventralizing the mesoderm?

Answer 21

Bone morphogenetic protein 4 (BMP4)

Question 22

What molecules secreted by the node and prechordal mesoderm acts to dorsalize cranial mesoderm (eventually leads to formation of notochord (NC) and paraxial mesoderm?

Answer 22

Chordin, Noggin, Follistatin

Question 23

What is the dorsalizing gene of the middle and caudal embryo?

Answer 23

Brachyury (T) gene

Question 24

Inappropriate regulation of expression of what leads to conjoined twins?

Answer 24

Goosecoid (dorsalizes head mesoderm)

Question 25

Absence of Brachyury (T) gene leads to what condition?

Answer 25

Caudal dysgenesis (sirenomelia)

Question 26

What molecule establishes left-sidedness? What molecule eventually overrides this signal to establish right-sideness

Answer 26

FGF8, SHH (sonic hedgehog)

Question 27

High doses of alcohol during pregnancy can to what? It is characterized by craniofacial malformations.

Answer 27

Holoprosencephaly

Question 28

What is situs inversus?

Answer 28

Transposition of viscera in thorax and abdomen

Question 29

Remnants of primitive streak (active when it isn’t supposed to be) leads to what condition?

Answer 29

Sacrococcygeal Teratoma

Question 30

Decribe primary, secondary, tertiary villus.

Answer 30

pri: 2 trophoblast cell layers sec: extraembryonic mesoderm core tert: capillaries present