Embryology Spine

Question 1

What are the derivates of the proatlas ?

Answer 1

1. Caudal part of basiocciput and basion (clivus)
2. Clival tubercle
3. Apical dens
4. Exocciput (occipital condyles and opisthion)

Question 2

Which structure attaches at the clival tubercle?

Answer 2

Fibrous pharyngeal raphe

Question 3

What is the condylus tertius?

Answer 3

Third condyle , rare anatomic variant. Small seperate ossicle formed by failure of the embryonic proatlas to unite with the condyle proper

Question 4

what is the severance line?

Answer 4

Junction between the head and spine which follows and intersomitic, not an interscerotomic boundary

Question 5

What are the derivatives of C1 sclerotome?

Answer 5

1.Anterior arch of atlas
2. Basal dens
3. lateral masses and posterior arch of atlas
The whole atlantal ring derives from C1 sclerotome

Question 6

What are the derivatives of C2 sclerotome?

Answer 6

1. Body of axis

2. Lateral and posterior elements of C2

Question 7

Names of synchondrosis in the axis (C2)

How many vertebral bodies in Axis?

Answer 7

Apicodental synchondrosis
Subdental synchondrosis

2.5 vertebral bodies

Question 8

What is gastrulation and which week?

Answer 8

Conversion of the bilaminar disk to a trilaminar arrangement and establishment of the notochord

Weeks 2bilaminar - 3 laminar

Question 9

Structures of the bilaminar disk?

Answer 9

Epiblast (faces amniotic sac)

Hypoblast (primitive endoderm) faces yolk sac

Question 10

What is the thickening in the middle of the epiblast called on day 16?

Answer 10

Primitive streak (Blastopore)

Question 11

What structure is on the rostrar part of the primitive streak?

Answer 11

The primitive pit (Hensen’s node) the organizer

Question 12

Describe gastrulation

Answer 12

Epiblastic cells migrate through the primitive streak to the epi-endoblast interface to form mesodermal and endodermal progenitors

Question 13

How is notochord made?

Answer 13

Epiblastic cells that migrate through Hensen’s node produce the notochord

Question 14

What is the main purpose of the notochord ?

Answer 14

Development of the neuroectoderm (neural plate)

Question 15

What is debated in humans?

Answer 15

The existence of a neurenteric canal in the formation of notochord. Disputed in humans

Question 16

What is the most common tumour in embryo?

Answer 16

Sarco-coccygeal teratoma due to persistence of cells in the primitive streak which moves caudally in the embryo

Question 17

Most rostral point of the neural tube?

Answer 17

The lamina terminalis

Question 18

When does the anterior neuropore closes?

Answer 18

30 days

Question 19

When is the end of the primary neurulation?

Answer 19

The closure of the posterior neuropore at 31 days

Question 20

Products of the secondary neurulation?

Answer 20

Terminal ventricle, Tip of conus medullaris and filum terminale

Question 21

Describe secondary neurulation and weeks

Answer 21

Caudal cell mass that canalises and connects to the primary neural tube
4-6 weeks

Question 22

What is the border of the secondary neural tube?

Answer 22

approx 32 somite

Question 23

Where does junctional neurulation happen and what is the ‘danger’?

Answer 23

It happens in the posterior neuropore.
Αντί το neural plate να κάνει το neural tube, εκεί έρχονται κι αλλα κυτταρα γίνονται layers φτιάχνουν τον σωλήνα οπότε high incidence of spinal dysraphisms

Question 24

what does the hypochordal bow of the pro-atlas form?

Answer 24

The clival tubercle

Question 25

What does the hypochordal bow of the C1 sclerotome form?

Answer 25

The anterior arch of C1

Question 26

What happens in the primary neurulation?

Answer 26

Neural plate cells proliferate, invaginate and pinch off the surface ectoderm to form the neural tube

Question 27

Origin of somites and divisions?

Answer 27

Paraxial Mesoderm

4 Occipital
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral 
3-6 Coccygeal

Question 28

Resegmented sclerotome description

Answer 28

Upper Ad + Lower Al = Vertebral body (from two somites!)
Upper Ld = neural arch and pedicle
Lower Lloose= nerve roots

Question 29

what does the intervertebral boundary zone do?

Answer 29

Makes Intervertebral disc.

Annulus + Notochord = nucleus palposus

Question 30

What is weird about the CCJ?

Answer 30

4 occipital somites
and first 3 cervical somites

No intersomitic boundary zone
No segmentation of the first 3 occipital axial sclerotomes