Lecture 15: Establishing the Basic Body Plan

Question 1

notochord formed from what layer

Answer 1

mesenchymal cells

Question 2

where does the notochord originate

Answer 2

the primitive node, mesenchymal cells migrating cranially

Question 3

where does notochord end

Answer 3

prechordal plate

Question 4

what is the main function of the notochord

Answer 4

primary inductor of the embryo

Question 5

what does the notochord induce in the overlying ectoderm

Answer 5

formation of the neural plate

Question 6

what gives rise to the CNS

Answer 6

neuroectoderm

Question 7

when does the neural groove form

Answer 7

day 18

Question 8

where does fusion of neural tube begin

Answer 8

cranially

Question 9

when do the anterior and posterior neuropore close

Answer 9

anterior: day 24-25
posterior: day 27

Question 10

fate of neural tube

Answer 10

forebrain: cerebral hemispheres
midbrain: adult midbrain
hindbrain: pons, cerebellum, medulla oblongata
Rest becomes spinal cord

Question 11

what are neural crest cells

Answer 11

neuroectodermal cells at the crest of the neural folds that detach as neural tube separates from ectoderm. migrate to each side

Question 12

neural crest cells become

Answer 12

DRG, ganglia of ANS, CN V VII IX and X, peripheral nerve sheaths, melanocytes, adrenal medulla, facial muscles/bones

Question 13

names of mesoderm

Answer 13

embryonic (somatic) = paraxial, intermediate, lateral and

extraembryonic (splanchnic) = continues with it

Question 14

where are the endo and ectoderm not separated by mesoderm

Answer 14

oropharyngeal membrane (prechordal plate) and cloacal membrane

Question 15

when are somites formed

Answer 15

end of week 3

Question 16

what does the paraxial mesoderm become

Answer 16

paired blocks called somites

Question 17

where do somites first appear

Answer 17

cranially

Question 18

how many pairs of somites by the end of week 5

Answer 18

42-44

Question 19

what do somites become

Answer 19

axial skeleton, skeletal muscles, dermis

Question 20

how does the body cavity form

Answer 20

coelomic spaces in lateral mesoderm and cardiogenic mesoderm. spaces coalesce to form intraembryonic coelom

Question 21

embryonic coelom becomes

Answer 21

pericardial cavity (heart), pleural cavity (lungs), peritoneal cavity (abdominal organs)

Question 22

when does angiogenesis begin

Answer 22

start of week 3

Question 23

where does angiogenesis begin

Answer 23

extraembryonic mesoderm, yolk sac, connecting stalk, chorion

Question 24

how are blood islands formed

Answer 24

mesenchymal cells in yolk sac called angioblasts aggregate

Question 25

how is the endothelium of blood vessels formed

Answer 25

angioblasts flatten to form endothelium, these fuse to form blood vessels

Question 26

initial blood cells formed from

Answer 26

endothelial cells called hemocytoblasts

Question 27

heart and great vessels formed from

Answer 27

mesenchyme (cardiogenic area)

Question 28

how/when is the primitive heart tube formed

Answer 28

paired endocardial tubes form and fuse

Question 29

when does the heart begin to beat

Answer 29

end of week 3

Question 30

allantois

Answer 30

outpouching of yolk sac into the connecting stalk, becomes bladder