Somites And Embryonic Folding

Question 1

Clefts appear in?

Answer 1

Lateral plate mesoderm

Question 2

The cavities in the intraembryonic coelom eventually…

Answer 2

Forms a horseshoe shaped cavity and becomes continuous with extraembryonic coelom

Question 3

Intracellular-embryonic coelom will eventually form…

Answer 3

Pericardial cavity;
Peritoneal cavity;
Pleural cavity;

Question 4

Intraembryonic mesoderm forms 3 longitudinal columns…

Answer 4

Paraxial;
Intermediate;
Lateral plate - continuous with extraembryonic mesoderm;

Question 5

At the beginning of the fourth week, paraxial mesoderm forms...
The medial part forms?
The intermediate part forms?
The lateral part forms?
The intermediate mesoderm forms?
Lateral mesoderm forms?

Answer 5

Cuboidal bodies (segments; somites);
Sclerotome -skeleton;
Myotome - muscle;
Dermotome - skin;
Genitourinary system (nephrotome); 
Parietal (body wall) an visceral (gut wall);

Question 6

Somites form the cranio-caudal sequence in the 4th week

Answer 6

3 occipital - tongue musculature 
8 cervical 
12 thoracic
5 lumbar
5 sacral

Question 7

Somite receives?

Answer 7

A segmental spinal nerve;

Follows the tissue wherever it migrates;

Question 8

The lateral plate is split into

Answer 8

Somatopleuric mesoderm - continuous with mesoderm of amniotic cavity which will form striated (voluntary) muscle (somatic, parietal);

Splanchopleuric mesoderm - continuous with mesoderm of yolk sac - forms the smooth muscle of the gut (splanchic, visceral);

Question 9

Longitudinal folding is known as?

1, 2, 3, 4, 5

Answer 9

Reversal;
1,2,3 - Heart and diaphragm;
3-4 - mouth;
5 - prospective brain;

Question 10

after reversal the amnion is only attached to the embryo over a small region called…

Answer 10

Umblicus

Question 11

Enlargement in longitudinal folding

Answer 11

Amniotic cavity enlarges;
Yolk sac constricts;
Rapid growth of neural tube;

Question 12

Lateral folding

Answer 12

Amnion grows towards yolk sac;

Folding reduces communication of intra and extraembryonic coelom;