NATS 1675 TEST 3 NOTES 2025 QUESTIONS AND ANSWERS

NATS 1675 TEST 3 NOTES 2025
QUESTIONS AND ANSWERS


Embryonic period extends from week ____ to week ____ - ....ANSWER ...-

3, 8


Gastrulation - ....ANSWER ...-begins the process of the developing embryo's

body taking shape and becoming organized

Step 1 of Gastrulation - Formation of Bi-laminar Embryonic Disk -

....ANSWER ...-1. A cavity forms between the inner cell mass and implanted

trophoblast cells (forming the amniotic cavity)

2. The inner cell mass flattens (into a 2-layered embryonic disk - becoming the

embryo)


2 layers of the embryonic disk - ....ANSWER ...-1. Hypoblast cells - give rise

to the Yolk Sac

2. Epiblast cells - cells that were originally closest to the implantation site, give rise

to the minion and the 3 primary germ layers




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, Step 2 of Gastrulation - ....ANSWER ...-Formation of the Primitive streak

and groove in the Epiblast cell layer of the Bi-Layered Embryonic Disk


Step 3 of Gastrulation - ....ANSWER ...-Formation of the Tri-Laminar

Gastrula (with 3 Primary Germ Layers) - as the Epiblast cells at the Primitive

Streak Undergo Migration Events


3 Primary Germ Layers - ....ANSWER ...-1. Ectoderm


2. Endoderm

3. Mesoderm


Sequence of Cell changes - Morula to Gastrula - ....ANSWER ...-Day 4 -

Morula: Solid ball of cells formed as the zygote undergoes cleavage

Day 6 - Early blastocyst: hollow ball of cells with a fluid-filled cavity

Day 10 - Late blastocyst: pre-embryo, with the embryonic disk, two laters of cells

that become the embryo proper

Day 16 - Gastrula: embryo with three primary germ layers (ectoderm, mesoderm

and endoderm)


Endoderm layer becomes... - ....ANSWER ...-1. Digestive system


2. Liver

3. Pancreas


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