ch 3. embryology week 3

Question 1

week 3: gastrulation
-what happens to the bilaminar disc during gastrulation

Answer 1

converted into the trilaminar embryonic disc

Question 2

week 3: gastrulation
-gastrulation

Answer 2

formation of the three primary germ layers: ectoderm, mesoderm, and endoderm

Question 3

week 3: gastrulation
-the three germ layers are the

Answer 3

precursor for all the body tissues

Question 4

week 3: gastrulation
-start:

Answer 4

begins with the appearance of a raised groove on the dorsal surface of the epiblast. during days 14-15, called the primitive streak.
-closer to the tail end.

Question 5

week 3: gastrulation
- where do the epiblast cells migrate to and what do they do?

Answer 5

the epiblast cells migrate towards the primitive streak and displace the epiblast and hypoblast layers.

Question 6

week 3: gastrulation
-first cells migrating to the primitive streak:

Answer 6

on days 14-15 epiblast cells migrate through the streak through the epiblast layer and displace the hypoblast layer= forming the endoderm

Question 7

week 3: gastrulation
-second group of cells migrating to the primitive streak:

Answer 7

form a new layer between the epiblast and the endoderm= mesoderm.
-day 16

Question 8

week 3: gastrulation
-third group of cells migrating to the primitive streak

Answer 8

cells that remain on the dorsal surface of the embryo form the ectoderm, layer

Question 9

the skin is associated with

Answer 9

ectoderm

Question 10

endoderm is associated with

Answer 10

lining of the inner tube of the body, GI tube and airway

Question 11

mesoderm

Answer 11

becomes most of all connective tissues and muscles

Question 12

endoderm and ectoderm are both made of:

Answer 12

epithelial tissues

Question 13

week 3: notochord and initial neural tube formation
-what is the primitive node

Answer 13

• a swelling at the cranial end of the primitive streak
  -has the ability for cells to fall through

Question 14

week 3: notochord and initial neural tube formation
-what happens to the cells that fall through the primitive node?

Answer 14

forms the notochord: a portion of the mesoderm. on day 16

Question 15

week 3: notochord and initial neural tube formation
-notochord

Answer 15

defines the axis of the body and is the site of the future vertebral column; stiffened rod of cells, gives head and tail end.

Question 16

week 3: notochord and initial neural tube formation
-neurolutaion

Answer 16

the notochord signals to the ectoderm to form the brain and spinal cord in a process called neurulation

Question 17

week 3: notochord and initial neural tube formation
-neural plate

Answer 17

forms as the notochord develops
-ectoderm thickens over the notochord

Question 18

week 3: notochord and initial neural tube formation
-neural groove:

Answer 18

happens as the neural plate is being formed, it starts to fold inward.
-gradually deepens until a hollow neural tube is pinched off into the dorsal surface of the body.

Question 19

week 3: notochord and initial neural tube formation
-neural tube

Answer 19

forms the brain and spinal cord

Question 20

week 3: notochord and initial neural tube formation
-when does the neural tube begin to close?
-when is it completely closed?

Answer 20

-closure begins at the end of week 3 in the future cerivical region and continues both cranially and caudally until complete closure at the end of week 4

Question 21

week 3: notochord and initial neural tube formation
-the cranial part of the neural tube becomes the _____ and the rest becomes the ________

Answer 21

-the brain
-the spinal cord

Question 22

week 3: notochord and initial neural tube formation
-neural crest and purpose

Answer 22

as the neural cord develops, some ectoderm cells migrate along its sides; flattened sheets of mass external to the neural tube
-purpose: give rise to the sensory nerve cells and sensory ganglia of spinal nerves.

Question 23

week 3: mesodermal differentiation
-middle and end of week 3

Answer 23

-middle: mesoderm lies lateral to the notochord in a cranio-caudal direction
-end of week 3: mesoderm differentiates into three distinct regions- somites, intermediate mesoderm, and lateral plate mesoderm

Question 24

week 3: mesodermal differentiation
-somites

Answer 24

a series of paraxial mesdoerm blocks found closest to the notochord; these are first body segments- bulges, round, most internal

Question 25

week 4: mesodermal differentiation
-inter3ediate mesoderm:

Answer 25

-lateral to the paraxial mesoderm , also segmented and attached to each somite; between the somite and lateral plate
-loses segmentation by the start of week 5

Question 26

week 4: mesodermal differentiation
-lateral plate mesoderm

Answer 26

never divides into segments, begins as a single layer that quickly splits into parts and encloses a space- coelom cavity

Question 27

week 3: mesodermal differentiation
-coelom:

Answer 27

embryonic body cavity

Question 28

week 3: mesodermal differentiation
-the coelom divides the lateral mesoderm into two layers

Answer 28

-somatic mesoderm and splanchnic mesoderm

Question 29

week 3: mesodermal differentiation
-somatic mesoderm:

Answer 29

next to the ectoderm (outer, parietal)- somatic: body

Question 30

week 3: mesodermal differentiation
-splanchnic mesoderm:

Answer 30

next to endoderm (inner, visceral); splanchnic=inside

Question 31

week 3: mesodermal differentiation
-after the coelom is enclosed it becomes

Answer 31

the pleural, pericardial, and peritoneal cavities (serous cavities of the ventral body cavity)