2-5, Cell Differentiation And Development

Front 1

what is a somite

Back 1

A somite is a division of the body of an animal or embryo

Front 2

what musculature is derived from somites

Back 2

Musculature of the axial skeleton, body wall and limbs are derived from somites

Front 3

in their formation, somites undergo epithelialisation, they are classified as either being part of the upper region or the lower region as part of this, name the components of the upper and lower region

Back 3

upper region:

dermatome

dorsomedial muscle cells

ventrolateral muscle cells

lower region:

vertebrae and ribs

Front 4

the dermatome is directed to become the dermis by what and from what location

Back 4

by neutrophin-3 from the dorsal neural tube

Front 5

what sequence of events combine for the expression of MYF5

Back 5

WNT (activating) and BMP (inhibitting) combine to form MYOD which creates a group of muscle cell precursors which expresses MYF5

Front 6

what are MYOD and MYF5

Back 6

they are myogenic regulatory factors, they can:

-activate muscle specific genes

-convert non-muscle cells to muscle cells

Front 7

what induces sclerotome formation

Back 7

sonic hedgehog and noggin

Front 8

where is the scerotome

Back 8

Front 9

what are the two mesodermal domains

Back 9

the primaxial and abaxial domain

Front 10

what is the lateral somitic frontier

Back 10

it is a well defined border between each somite and the lateral plate mesoderm

Front 11

what two mesodermal domains are separated by the lateral somatic frontier

Back 11

the primatial domain and the abaxial domain

Front 12

what is the primaxial domain

Back 12

the region around the neural tube, somite derived mesoderm

Front 13

what is the abaxial domain

Back 13

parietal layer of lateral plate mesoderm and some migratory somitic cells

Front 14

the lateral somatic frontier also separates two other things other than the primaxial and abaxial domains, what are these?

Back 14

also separates the dermis derived from the dermatome, and the dermis derived from the lateral plate mesoderm in the body wall

Front 15

the signals controlling the development of the primaxial and abaxial domains of the mesoderm come from different places, where does the primaxial domain get its signals from

Back 15

Primaxial: many from neural tube and notochord

Front 16

the signals controlling the development of the primaxial and abaxial domains of the mesoderm come from different places, where does the abaxial domain get its signals from

Back 16

Abaxial: many from lateral plate mesoderm

Front 17

each spinal nerve divides into two nerve segments, what are these called

Back 17

the dorsal primary ramus

the ventral primary ramus

Front 18

what are the epaxial muscles

Back 18

the true muscles of the back

Front 19

what are the hypaxial muscles

Back 19

the limb and body wall

Front 20

are the epaxial (true back muscles) innervated by the dorsal or ventral primary ramus

Back 20

dorsal primary rami

Front 21

are the hypaxial (limbs and body wall) innervated the by the dorsal or ventral primary ramus

Back 21

ventral primary ramus

Front 22

Molecular signals for muscle induction arise from tissue which is where in relation to prospective muscle cells

Back 22

Molecular signals for muscle induction arise from tissue adjacent to prospective muscle cells

Front 23

what is gastrulation

Back 23

Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm

Front 24

give a summary of how muscles are made

Back 24

Front 25

in embryonic development, when do the 'limb buds' first become visible

Back 25

week 4

Front 26

when does limb morphogenesis occur

Back 26

weeks 4-8

Front 27

is the lower limb development slightly faster or slower than upper limb development

Back 27

sightly slower, however it catches up by the end of the developmental period

Front 28

from which embryonic part is the mesenchyme derived from

Back 28

from the dorsolateral cells of the somites

Front 29

what type of tissue dictates the pattern of muscle formation

Back 29

connective tissue

Front 30

since connective tissue dictates the pattern of muscle formation, what layer is connective derived from

Back 30

parietal layer of lateral plate mesoderm

Front 31

lim buds consists of a mesenchymal core, from where is this core derived

Back 31

From parietal layer of lateral plate mesoderm

Front 32

what is the mesenchymal core covered by

Back 32

the cuboidal ectoderm

Front 33

when the ectoderm is growing, what area of it "thickens"

Back 33

the distal border thickens

Front 34

what is the distal border of the ectoderm where the ectoderm thickens also known as

Back 34

the 'progress zone'

or

APICAL ECTODERMAL RIDGE

Front 35

does the apical ectodermal ridge ever differentiate?

Back 35

no, it always remains undifferentiated

Front 36

as the limb grows, at what places do the cells differentiate and what do they differentiate into

Back 36

the cells that are farthest form the Apical ectodermal ridge, differentiate the most and they differentiate into cartilage and muscle

Front 37

what are the 2 main things the Apical Ectodermal Ridge is responsible for

Back 37

limb development

key signalling centre

Front 38

development of limbs occurs in what direction

Back 38

proximodistally

Front 39

what are the 3 components of the proximodistal limb development

Back 39

stylopod

zeugopod

autopod

Front 40

what are the components in the stylopod zeugopod and autopod subsequently

Back 40

– Stylopod – humerus and femur

– Zeugopod – radius/ulna and tibia/fibia

– Autopod – carpels, metacarpals, digits, tarsals/metatarsals

Front 41

at week 6 the terminal portion of the 'buds' become flattened to form what 2 different entities

Back 41

handplates

footplates

Front 42

how do the fingers form

Back 42

• Cell death in the AER separates ridges into 5 parts – 5 digits grow out under influence of 5 ridge parts

• Mesenchyme condenses to form cartilaginous digits

• By d56, digit separation is complete

Front 43

roughly how far behind is the development of the lower limbs compared with the upper limbs

Back 43

1-2 days

Front 44

when does limb rotation occur in the embryo

Back 44

week 7

Front 45

what direction do the upper and lower limbs rotate in

Back 45

upper limbs --> 90o laterally

lower limbs --> 90o medially

Front 46

limb outgrowth is regulated by what growth factor and from where is it secreted

Back 46

FGF10

secreted by lateral plate mesoderm

Front 47

what is the AER induced by

Back 47

BMPs

Front 48

what does the RADICAL FRINGE in the ​dorsal limb do

Back 48

restricts AER to the distal tip and induces SER2

Front 49

what maintains the undifferentiated zone

Back 49

FGF 4 and FGF 8

Front 50

the positioning of the limbs along the craniocaudal axis is controlled by what gene

Back 50

the HOX gene

Front 51

in what sort of way is the HOX gene expressed

Back 51

Front 52

what transcription factors are expressed in the upper limbs

Back 52

TBX-5

Front 53

what transcription factors are expressed in the lower limbs

Back 53

TBX-4 and PITX1

Front 54

from where do limbs arise from

Back 54

the lateral mesoderm and overlying ectoderm

Front 55

explain how bone limb development occurs

Back 55

• As the external shape is being established, mesenchyme in the buds becomes condensed

• Cells differentiate into chondrocytes
• At week 6, hyaline cartilage models can be

seen

• Areas where chondrogenesis is arrested makes joints

– Cell proliferation, increased density, differentiation then cell death – induced by WNT 14

Front 56

when is the first cartilage laid down in bone development

Back 56

week 6

Front 57

by what week are the primary ossification centres present in all long bones

Back 57

Primary centres of ossification are present in

all long bones by week 12

Front 58

list the stages in limb bone development

Back 58

Cells in centre of cartilage model proliferate, enlarge, make new kind of matrix

– can be calcified

– calcified cartilage matrix does not allow diffusion of nutrients, so cartilage cells die

–left with spicules of calcified cartilage matrix

–acts as a scaffolding on which bone can be deposited

Periosteum – vascular connective tissue around the model – blood vessels grow in – bringing progenitor cells

Osteoprogenitor cells become osteoblasts, line up on spicules and start producing bone matrix

Core of calcified cartilage matrix is removed by osteoclasts

Trapped osteoblasts – become osteocytes

Front 59

during childhood in what directions do bones grow

Back 59

in both length and width

Front 60

define interstitial growth

Back 60

growth throughout the tissue

Front 61

what is appositional growth

Back 61

growth at the bone surface

Front 62

cartilage is capable of interstitial growth, is bone?

Back 62

nope

Front 63

when do growth plates 'close' and what happens to them

Back 63

they close at puberty

they are converted to bone

Front 64

during the growth period, what is the remodelling of bones done by? and why

Back 64

it is done by osteoclasts to retain overall shape and proportion