The third week

Question 1

what does the third week represent in the development of the human ?

Answer 1

gasturlation, formation of the three layers and organs

Question 2

at the end of the second week what happens to the embryonic disk ?

Answer 2

becomes elongated and is broader at the butt end (cephalic end)

Question 3

What happens on day 15

Answer 3

epiblast cells begin to migrate towards the midline forming a groove

Question 4

the primitive pit develops into what

Answer 4

notochord

Question 5

What is the notochord composed of ?

Answer 5

mesoderm and endodermal cells

Question 6

What are the four functions of the notochord ?

Answer 6

CNS development, development of the vertebral column, anatomic midline, and forms the nucleus pulposis

Question 7

ectopodiacordis

Answer 7

heart is outside of the body

Question 8

what contributes to the longitudinal (head tail fold)

Answer 8

occurs along the saggital plane and is due to the rapid growth of the CNS and differential growth

Question 9

What roles do the primitive streak and the primitive node play in development ?

Answer 9

determination of the body axes

Question 10

dextrocardia

Answer 10

heart is on the wrong side of the body

Question 11

what induces the epiblast to proliferate and migrate towards the midline forming a groove ?

Answer 11

hypoblast cells

Question 12

day 16

Answer 12

epiblast cells proliferate and migrate through the primitive streak into the space between the epiblast and the hypoblast

Question 13

when cells completely display the hypoblast cells so that thehypoblast is completely repopulatioed this is defined as what ?

Answer 13

endoderm

Question 14

epiblast cells begin to occupy the space between the endoderm and the epiblast

Answer 14

intraembryonic mesoderm

Question 15

epiblast that do NOT migrate through the streak are known as

Answer 15

ectoderm

Question 16

cells from the primitive pit invaginate and create a hollow tube what is this called

Answer 16

notochord

Question 17

floor of notochorrdal processes fuse with endoderm and form

Answer 17

notochordal plate

Question 18

notochordal plate detaches beginning at the cranial end to form/

Answer 18

notochord

Question 19

where does the notochord extend from ?

Answer 19

prechordal plate to primitive pit

Question 20

what is the neurenteric canal

Answer 20

connection between the amniotic cavity and the yolk sac

Question 21

neurenteric cysts

Answer 21

masses of endodermally derived tissue commonly associated with spinal cord derived from neurenteric canal where ectoderm and endoderm are closely associated

Question 22

at the buccopharyngeal membrane what begins to forms in the 3rd week

Answer 22

mouth

Question 23

at the cloacal membrane what begins to form in the 3rd week

Answer 23

anus

Question 24

what is the major outcome of the longitudinal fold

Answer 24

elongated gut tube and closure of the body cavity

Question 25

situs inversus

Answer 25

complete-all organs are mirror image of normal orientation; incomplete-only a single organ is involved

Question 26

sirenomelia

Answer 26

caudal dysgenesis resulting from inadequate mesoderm in caudal regions (limb and urogenitcal defects)

Question 27

sacrococcygeal teratoma

Answer 27

results from persistence of the primitive streak and pluripotent cells

Question 28

during the first week of the embryonic period how is the age determined

Answer 28

by the number of somites

Question 29

after week four how is the age of the embryo expressed

Answer 29

crown rump length (vertex of skull to caudal tip of the trunk)

Question 30

sacrococcygeal teratoma

Answer 30

persistence of the primitie streak and pluripotent cells

Question 31

dextrocardia

Answer 31

heart is on the wrong side of the body

Question 32

ectopia cordis

Answer 32

heart outside of the body