EMBRYOLOGY

Question 1

What does the ectoderm form?

Answer 1

Forms outer epithelium (skin)
Forms nervous system

Question 2

What does the mesoderm become?

Answer 2

Musculoskeletal system, including smooth muscle

Question 3

What does endoderm become?

Answer 3

Intestinal epithelium

Question 4

What does mesoderm produce as it differentiates?

Answer 4

Embryonic mesenchyme
Term for loose tissue stuff that forms blood vessels, tendons, cartilage, muscles etc.

Question 5

What are the 4 different tissue types in embryology and what are they formed form?

Answer 5

1. Epithelium—> skin, lungs and GIT lining (ectoderm)
2. Neural (ectoderm)
3. Contractile, muscles —> (mesoderm)
4. Connective —> everything not 1,2,3 (endoderm)

Question 6

Where is most of the loose connective tissue formed during embryonic development and what are its features?

Answer 6

Umbilical cord
Hydrophilic ECM
Jelly like (Whartons jelly)

Question 7

What are the 5 main stages in embryology?

Answer 7

Fertilisation
Early cell division
Formation of 3 fundamental cell type
Emergence of body plan
Post embryonic development

Question 8

What is each cell in the morula called

Answer 8

Blastomere

Question 9

At what point is it called a morula

Answer 9

16-32 cells

Question 10

What is a blastocysts

Answer 10

Shell around exterior and inner cell mass has formed

Question 11

What are the two parts of the inner cell mass called

Answer 11

Epiblast
Hypoblast

Question 12

What is gastrulatiom

Answer 12

Process of cellular rearrangement which involved formation of tri- laminar disk

Question 13

What is the first visible sign of gastrulatiom

Answer 13

Formation of primitive streak (midline groove at epiblast cells migrate caudal to cranial)

Question 14

What is the primitive node

Answer 14

The end of the streak

Question 15

How is endoderm formed

Answer 15

Epiblast cells migrate through the primitive pit and displace the hypoblast cells

Question 16

How ks the mesoderm formed?

Answer 16

Epiblast cells migrate through the primitive pit and lie between the epiblast layer and the newly created endoderm

Question 17

How is the ectoderm formed

Answer 17

By the Epiblast cells that remain in position

Question 18

How is the notochordal process formed

Answer 18

Prenotochodral cells move into pit and cranially becoming notochordal process
Forms notochordal plate, allowing pressure equilibrium Plate fuses together to form notochord

Question 19

How is neural tube for,ed

Answer 19

Notochordal has natural kinks (grooves) in it
Lateral edges form neural fold, which fuse together to form neural tube
Occurs cranially (brain) and causally (spinal chord_

Question 20

How is the neural crest formed?

Answer 20

Neural tube has already formed
Some ectodermsl cells from tube migrate which forms neural crest

Question 21

What does the neural crest form

Answer 21

Peripheral NS

Question 22

What does the neural tube form?

Answer 22

Spinal cord

Question 23

What are somites formed from and where are they?

Answer 23

Derived from para axial mesoderm (either side of neural tube)
Same amount each side of tube
Lateral to neural tube and notochord

Question 24

How can you age mesoderm

Answer 24

By how many somites there are

Question 25

What will somites form

Answer 25

Skeletal muscles
Tendons
Cartilage

Question 26

What are somites important for

Answer 26

Segmentation

Question 27

What’s are the three different parts of the somite?

Answer 27

Dermatome
Myotome
Sclerotome

Question 28

What determines fate of multi potent cells within somites

Answer 28

Location within somite and factors from surrounding tissues

Question 29

What generates the axial (vertebrae) skeleton

Answer 29

Somites

Question 30

What generates the limb skeleton

Answer 30

Lateral plate mesoderm

Question 31

What generates the skull and face

Answer 31

Neural crest and head mesoderm

Question 32

How is the vertebrae developed?

Answer 32

Sclerotome cells are attracted to notochord and neural tube region
Sclerotome cells form vertebrae body
Develops from caudal part of one Sclerotome to cranial part of the next one
Sclerotome cells covering neural tube form neural arches which fuses which corresponding vertebrae body

Question 33

What are the three different axes in ensuring limbs are laid out correctly

Answer 33

• proximal distal (shoulder- finger tip)
• antero- posterior (thumb- little finger)
• dorso- ventral (knuckle- palm)

Question 34

How are limb buds formed?

Answer 34

Proliferation of skeletal and muscle precursors
Cells accumulate under the ectoderm creating a bulge (limb bud)

Question 35

What is the AER

Answer 35

Apical ectoderm ridge (thickening of ectoderm at the tip of the limb bud)
Major signalling centre
Induced my mesenchyme cells

Question 36

What is the progress zone?

Answer 36

Distal part of the mesenchyme extends the limb bud by proliferation

Question 37

What helps coordinate the anterior posterior axis

Answer 37

Sonic hedgehog signalling molecule
Organised by a small block of the mesoderm called zone of polarising activity

Question 38

How are digits formed

Answer 38

Via concentration gradient of sonic hedgehog molecule
Apoptosis

Question 39

What controls the dorsal ventral axis

Answer 39

Ectoderm
Peels off and rotates the ectoderm relative to the mesenchyme

Question 40

How are synovial joints formed?

Answer 40

1. Pre cavitation —> mesenchyme converted into cartilage. Then chondral ossification occurs and and chondrocytes left over form articular cartilage
2. Cavitation —> interzone between adjacent bones differentiate into dense connective tissue. Cells undergo apoptosis and hyaluronic acid synthesis
3. Post cavitation—> hyaluronic acid causes tissue separation to create joint cavity