Somites and embryonic folding

Question 1

What is the intra-embryonic mesoderm divided into

Answer 1

• paraxial
• intermediate
• lateral

columns

Question 2

What happens to the trilaminar disk in the fourth week

Answer 2

Folds

Question 3

Where is the paraxial column of the intraembryonic mesoderm

Answer 3

Nearest to the neural tube

Question 4

Where is the intermediate column of the intraembryonic mesoderm

Answer 4

IN the little fold in the middle of the neural tube and the extra embryonic mesoderm

Question 5

Where is the lateral column of the intraembryonic mesoderm

-What is it continuous with

Answer 5

Nearest to the outside

-continous with the extra-embryonic mesoderm

Question 6

In the beginning of the fourth week, what does the paraxial mesoderm do

Answer 6

Begins to form somites

Question 7

What does the medial part of the paraxial mesoderm become

Answer 7

Sclerotome (skeleton)

Question 8

What does the intermediate part of the paraxial mesoderm become

Answer 8

Myotome (muscle)

Question 9

What does the lateral part of the paraxial mesoderm become

Answer 9

Dermatome (skin)

Question 10

What does the intermediate mesoderm become

Answer 10

Nephrotome

Question 11

What does the nephrotome form

Answer 11

Genitourinary system

Question 12

What does the lateral mesoderm become

Answer 12

Either parietal (body wall) or visceral (wall of gut)

Question 13

In the fourth week, what do somites form

Answer 13

In a crania-caudal sequence

Question 14

Numberings of the somites and what they become

Answer 14

3 occipital
8 cervical
12 thoracic
5 lumbar
5 sacral
1-5 coccygeal

remain

Question 15

What is the occipital

Answer 15

Tongue musculature

Question 16

What does each somite receive

Answer 16

Each receive a segmental spinal nerve which follows that tissue wherever it goes

Question 17

What is the lateral plate split into

Answer 17

• somatopleuric mesoderm

- splanchnopleuric mesoderm

Question 18

What is the somatopleuric mesoderm continuous with

Answer 18

Mesoderm of the amniotic cavity

Question 19

What will the somatopleuric mesoderm eventually form

Answer 19

Striated (voluntary) muscle

Question 20

What is the splanchnopleuric mesoderm continuous with

Answer 20

Mesoderm of the yolk sac

Question 21

What will the splanchnopleuric mesoderm eventually form

Answer 21

Smooth muscle of the gut

Question 22

What will the intraembryonic coelom eventually form

Answer 22

• pericardial cavity
• pleural cavity
• peritoneal cavity

Question 23

What happens in longitudinal folding

Answer 23

Reversal

Question 24

What does the differential growth of the embryo cause it to do

Answer 24

Fold both cranio-caudally and laterally

Question 25

What is important in producing reversal

Answer 25

Rapid growth of the neural tube

Question 26

After reversal, how is the amnion attached to the embryo

Answer 26

Only attached via the ubmilicus

Question 27

In reversal, which part is enlarging quickly

Answer 27

Amniotic cavity

Question 28

What happens to part of the yolk sac after reversal

Answer 28

HAs become incorporated into the gut tube

Question 29

What does folding do

Answer 29

reduce communication between intra and extra embryonic coelom

Question 30

What happens in lateral folding

Answer 30

The edges of the amnion grow downwards towards the yolk sac

Question 31

What is the Vitelli-intestinal duct

Answer 31

In the region of the umbilicus a connection between the gut tube and the yolk sac remains