Somitogenesis and neural tube formation

Question 1

In which stage of foetal development does neurulation occur?

Answer 1

Organogenesis

Question 2

What is neurulation?

Answer 2

Process of neural tube formation that occurs during organogenesis

Question 3

What structure is formed in gastrulation that induces formation of the neural tube?

Answer 3

Notochord

Question 4

What is the first inductive effect of the notochord?

Answer 4

Causes ectodermal cells to differentiate into neuroectoderm

Question 5

What is the structure of neuroectoderm?

Answer 5

Pseudostratified columnar neuroepithelium

Question 6

Where does the open neural plate begin to form during neurulation?

Answer 6

Cranial end of embryo

Question 7

What direction does the open neural plate differentiate in during neurulation?

Answer 7

Cranial-caudal direction

Question 8

What is the 2nd inductive effect of the notochord, that occurs once the open neural tube has been completed?

Answer 8

Induces folding of lateral surface ectoderm and neuroectoderm to form neural folds

Question 9

When neural folds form in the open neural tube, what is the depression in the middle called?

Answer 9

Neural groove

Question 10

How is the open neural tube closed up to form a hollow neural tube?

Answer 10

Neural folds on each side of the neural groove fuse together

Question 11

Where are neural crest cells formed?

Answer 11

Neural plate lateral regions

Question 12

When do neural crest cells detach from the neural tube?

Answer 12

During neural tube formation

Question 13

What happens to neural crest cells after they detach from the forming neural tube?

Answer 13

Migrate in embryo to contribute to tissues/organs

Question 14

When does paraxial mesoderm develop during neurulation?

Answer 14

During neural tube formation

Question 15

What is meant by paraxial mesoderm being organised into bilateral columns?

Answer 15

There are 2 streaks (columns) of paraxial mesoderm in total, each streak is lateral on each side of the neural tube

Question 16

What intermediate and definitive structure is formed from paraxial mesoderm?

Answer 16

Intermediate structure is somitomere

Definitive structure is somite

Question 17

During somitogenesis, what do the bilateral columns ultimately divide into?

Answer 17

Paired somites, so that one somite is on each side of the neural tube

Question 18

How are somitomeres formed from paraxial mesoderm?

Answer 18

Paraxial mesodermal cells come together to form blocks called somitomeres, so there is incomplete segmentation between the blocks

Question 19

How are somites formed from somitomeres?

Answer 19

Somitomeres become compacted and bound by epithelium to form somites, which are completely segmented blocks of paraxial mesoderm

Question 20

What direction does somitogenesis occur in?

Answer 20

Craniocaudal sequence

Question 21

What 2 neural tube formation events are occurring at the same time of somitogenesis?

Answer 21

Formation of neural folds, regression of primitve streak

Question 22

How many somite pairs are formed in total?

Answer 22

38

Question 23

Which somitomeres don’t condense into somites?

Answer 23

Somites in more cranial parts of head

Question 24

Where do the first pairs of somites develop?

Answer 24

Occipital region (back of head)

Question 25

What are the 2 subdivisions of a somite?

Answer 25

Mesenchymal sclerotome, dermomyotome

Question 26

What cells in the somite differentiate into mesenchymal sclerotomes?

Answer 26

Ventromedial

Question 27

What cells in the somite differentiate into dermomyotomes?

Answer 27

Dorsolateral

Question 28

Which surface of the embryo do somites develop along?

Answer 28

Dorsolateral

Question 29

What 3 type of muscles do myotomes develop into?

Answer 29

Limb muscles in developing limbs

Hypaxial (ventrolateral)

Epaxial (dorsal)

Question 30

What do dermatomes develop into?

Answer 30

Skin dermis

Question 31

Give 2 structures that mesenchymal sclerotomes develop into?

Answer 31

Vertebral column (spine), ribs

Question 32

What is the definition of the notochord, and why does it need to develop before the neural tube?

Answer 32

Temporary structure in embryo midline that acts as axis around which vertebral column develops

Neural tube forms along notochord