Basic Embryology 1

Question 1

When does the embryonic disc form?

Answer 1

Second week in utero

Question 2

When does the gastrulation occur or a 3-layered embryo form?

Answer 2

3rd week in utero

Question 3

What are the 3 layers of the embryo called?

Answer 3

Ectoderm, mesoderm, endoderm

Question 4

Invagination of ectoderm along the primitive streak gives rise to what embryonic structure?

Answer 4

Notochord

Question 5

What is the name given to the mesoderm that will give rise to the vertebral column?

Answer 5

Paraxial mesoderm

Question 6

What does paraxial mesoderm give rise to that will form the vertebral column?

Answer 6

Somites

Question 7

Name the areas of cellular differentiation formed within the somite.

Answer 7

Sclerotome, myotome, and dermatome

Question 8

What part of the somite will give rise to the vertebral column?

Answer 8

Sclerotome

Question 9

List, in order, the names of the successive vertebral columns formed during development?

Answer 9

Membranous, cartilaginous, skeletal, or osseous

Question 10

Migration of sclerotomes to surround the notochord forms what developmental feature?

Answer 10

The perichordal blastema

Question 11

The perichordal blastema gives rise to what processes?

Answer 11

Neural processes and costal processes

Question 12

What is the name of the artery located between adjacent perichordal blastemae?

Answer 12

Intersegmental artery

Question 13

Cell proliferation within the perichordal blastema will result in what features?

Answer 13

A loose cranial sclerotomite and a dense caudal sclerotomite

Question 14

What forms between the sclerotomites of a perichordal blastema?

Answer 14

The intraslcerotomal fissure (fissure of von Ebner)

Question 15

The intrasclerotomal fissure (fissure of von Ebner) gives rise to what developmental feature?

Answer 15

The perichordal disc

Question 16

The perichordal disc in the presumptive location of what adult feature?

Answer 16

The intervertebral disc

Question 17

What is the earliest embryonic feature that will identify the position of the adult intervertebral disc?

Answer 17

The intrasclerotomal fissure (fissure of von Ebner)

Question 18

The union of a dense caudal sclerotomite and a loose cranial sclerotomite from adjacent perichordal blastemae gives rise to what feature?

Answer 18

The vertebral blastema

Question 19

What vessel will be identified adjacent to the vertebral blastema?

Answer 19

The segmental artery

Question 20

When will cartilage first form in the membranous vertebral blastema?

Answer 20

Beginning in the 6th embryonic week

Question 21

What is the name given to the replacement of mesoderm by cartilage?

Answer 21

Chondrification

Question 22

Chondrification is first identified in which region of the embryonic vertebral column?

Answer 22

The cervical region

Question 23

What are the names given to the centers of chondrification within the vertebral blastema?

Answer 23

Centrum center, neural arch center, transverse process center

Question 24

How many centers of chondrification typically appear in the vertebral blastema?

Answer 24

6… 2 for the centrum, 2 for the neural arch, 2 for each transverse process

Question 25

What is the earliest time that centers of ossification appear in the cartilaginous vertebra?

Answer 25

During the 7th embryonic week

Question 26

Ossification begins in which region of the embryonic vertebral column?

Answer 26

The lower cervical-upper thoracic region

Question 27

What is the name given to centers of ossification appearing in utero?

Answer 27

Primary centers

Question 28

What is the name given to centers of ossification appearing after birth?

Answer 28

Secondary centers

Question 29

What is the ratio of primary to secondary centers of ossification for a typical vertebra?

Answer 29

3 primary centers: 5 secondary centers

Question 30

What are the names of the primary centers of ossification for a typical vertebra?

Answer 30

Centrum centers and neural arch centers

Question 31

How many primary centers of ossification appear in the typical vertebra?

Answer 31

3… 1 for the centrum, 2 for the neural arch centers

Question 32

What is the classification of the joint forming between primary centers of ossification?

Answer 32

Cartilage synchondrosis/amphiarthrosis synchondrosis

Question 33

What are the names of the synchrondoses forming between primary centers of ossificationin the typical vertebra?

Answer 33

Neurocentral synchondrosis and neural arch synchondrosis

Question 34

What are the names of the 5 secondary centers of ossification for a typical vertebra?

Answer 34

Tip of transverse process, tip of spinous process, epiphyseal plate centers

Question 35

How many secondary centers of ossification appear in the typical vertebra?

Answer 35

5… 1 for the tip of each transverse process, 1 for the tip of spinous process, 1 for each epiphyseal plate

Question 36

What is the classification of the joint forming between secondary centers of ossification and the rest of the typical vertebra?

Answer 36

Cartilage synchondrosis/amphiarthrosis synchondrosis

Question 37

What are the names of the synchondroses forming between secondary centers of ossification and the rest of the typical vertebra?

Answer 37

Tip of transverse process synchondrosis, tip of spinous process synchondrosis, and epiphyseal ring synchondrosis

Question 38

What is the range of appearance for secondary centers of ossification of a typical vertebra?

Answer 38

During puberty, typically ages 11-16 years old