EXAM3_19_Trunk_Development

Question 1

What expression at the primitive node initiates/maintains the primitive streak?

Answer 1

Nodal TGF-B Family expression

Question 2

What expression controls cell migration and invagination?

Answer 2

FGF8 expression

Question 3

What is spemann’s organizer?

Answer 3

Primitive node

Question 4

Somitomeres form on sides of cranial neural tube and differentiate into what?

Answer 4

Most skeletal muscles of the head

Question 5

Somites form on the sides of notochord and neural tube and differentiate into what?

Answer 5

skeletal muscles Axial skeleton

Question 6

What drives somite identification?

Answer 6

HOX expression

Question 7

What gradient drives differentiation of cranial to caudal? and what does that promote?

Answer 7

Retinoic Acid — promotes HOX expression to drive somite identification

Question 8

All skeletal muscle is derived from Paraxial mesoderm somites and somitomeres at the same time as what?

Answer 8

at the same time neurulation occurs in ectoderm

Question 9

SHH is involved as ectoderm forms neuroectoderm (forming neural tube and neural crest). What does SHH and BMP4 then induce?

Answer 9

SHH induces anterior neural tube (motor)

BMP4 induces posterior neural tube (sensory)

Question 10

What two expressions induce sclerotome development?

Answer 10

SHH (from neural tube) and Noggin (from notochord)

Question 11

What expression induces dermatome development?

Answer 11

NT-3

Question 12

What expressions induce myotome development?

Answer 12

WNT + (SHH or BMP4)

Question 13

Sclerotome cells express what?

Answer 13

PAX1

Question 14

Dermatome cells express what?

Answer 14

PAX 3

Question 15

Myotome cells express what?

Answer 15

MyoD (hypaxial) or Myf5 (epaxial)

these divisions form by week 5

Question 16

Myotome differentiation caused by MYF5 expression are what type of muscles? what is significant about their myoblast differentiation?

Answer 16

Epaxial (intrinsic) muscles, the myoblasts don’t migrate

Question 17

Some myoblasts of hypaxial derivatives do not migrate (just like epaxial myoblasts), what is an example of hypaxial myoblasts that do not migrate?

Answer 17

Intercostal Muscles, Abdominal muscles

upper limb muscles DO migrate

Question 18

In utero ossification begins at ___ weeks?

Answer 18

7 weeks

Question 19

When do primary and secondary ossification centers complete?

Answer 19

primary end at age 6

Secondary at age 25

Question 20

Where are the primary ossification centers ? when do they start and end?
secondary ossification centers?

Answer 20

1 body 2 in forming arches 7weeks to 6 years old

secondary are on periphery of bodies and ends of processes and last till about 25yo.

Question 21

What parts of the vertebral column are bony at birth?

Answer 21

two Half -arches and the centrum (forms body)

Question 22

What forms the nucleus pulposus and the anulus fibrosis?

Answer 22

Notochord forms nucleus pulposus

Mesenchyme forms anulus fibrosus

Question 23

Where are the intervertebral discs formed from

Answer 23

Notochord and mesenchyme of somites

Question 24

The vertebral body is made from what neurological layer?

Describe the development of the notochord

Answer 24

Sclerotome.

Most of the notochord degenerates but the parts between the vertebral bodies end up forming the Nucleus pulposus

Question 25

Resegmentation occurs as each vertebra forms from the fusion of the caudal half of the sclerotome of one somite and the cranial half of the subjacent somite. How many cervical somites do we have? why do we have 7 vertebrae?

Answer 25

We have 8 cervical somites (each with its own innervation), The caudal half of O4 and the Cranial half of C1 forms the base of the occipital bone. The caudal half of C8 and cranial half of T1 forms the T1 vertebrae. This is why we only have 7 cervical vertebrae

Question 26

Visceral mesoderm is initially between somites and finish at mid-vertebrae--- these are called?

Answer 26

Intersegmental arteries (Visceral lateral plate mesoderm)

Question 27

outgrowth of neural tube initially at mid-somite level finishes between vertebrae. These represent the?

Answer 27

Spinal nerves (Neural tube- neuro ectoderm)

Question 28

Why do spinal nerves innervate multiple muscles?

Answer 28

Because Most muscles derived from multiple segments

Question 29

Myotomes undergo resegmentation end up spanning two segments of the vertebral column. What muscles are these?

Answer 29

Rotatores brevis (myoblast from a single myotome)

Question 30

Ribs and sternum are derived from two different layers?

Answer 30

Ribs- Sclerotome (just like vertebrae) | Sternum- Lateral plate - parietal layer (b/c part of body wall)

Question 31

What is it called if the left and right halves of the sternum don't fuse appropriately?

Answer 31

Cleft Sternum

Question 32

LOF mutations of HOX9 results in? rodents*

Answer 32

rib cages with 13 ribs attached to sternum

Question 33

LOF Hox9 produces

Answer 33

floating ribs

Question 34

Hox inhibition where its usually expressed leads to

Answer 34

LOF

Question 35

Hox expressed where its usually not

Answer 35

GOF

Question 36

If T1-t10 had a GOF of hox9 what would be seen?

Answer 36

No ribs attached to sternum

Question 37

Hox10 prevents rib formation- so a GOF/LOF

Answer 37

GOF Hox10 has no ribs | LOF hox10 has all ribs

Question 38

HOX11 fuses vertebrae-- sacrum | sometimes 6 fused , othertimes 4 fused. what is that called respectively?

Answer 38

Sacralization of L5 vertebra- Hox11 GOF at L5 Lumbarization of S1 vertebra- Hox11 LOF at S1

Question 39

What is it called when a vertebra doesnt form completely?

Answer 39

Hemivertebra

Question 40

Fracture of vertebral arch called

Answer 40

spondylolysis

Question 41

Dislocation between adjacent vertebrae subsequent to sondylolysis

Answer 41

Spondylosisthesis (congenital developmental defects or trauma)

Question 42

When one or more vertebral arches fail to develop or fuse What called if no herniation of meninges or spinal cord? What called if herniation of meninges/spinal cord?

Answer 42

Spinabifida (caudal neuropore failure) _spinabifida occulta- no herniation Spinabifida cystica

Question 43

Severe caudal failure, in which neural tissue is exposed and often becomes necrotic

Answer 43

Rachischisis (ra kis chi sis)

Question 44

What can indicate a neural tube defect?

Answer 44

Alpha fetoprotein increase in maternal serum or amniotic fluid (need Folic acid before pregnancy)

Question 45

2,3,4,5,6,8 weeks of development

Answer 45

2- uteroplacental exchange & bilaminar disc, 3, Gastrulation, nurulation, body folding 4. limb buds, 5. resegmentation of somites into vertebral bodies 6. chondrification centers form in vertebra 7-8. Primary ossification centers form- fingers developed