Development of the Neuromuscular System

Question 1

What primary germ layer does nervous tissue arise from?

Answer 1

ectoderm

Question 2

What primary germ layer does muscle and connective tissue arise from?

Answer 2

mesoderm

Question 3

What differentiates to give rise to the peripheral nervous system?

Answer 3

The neural crest cells

Question 4

What type of epithelium is seen in the early development of the neural tube?

Answer 4

pseudo stratified columnar epithelium and they have a high degree of mitotic activity

Question 5

What does cellular division and maturation of the neural tube cells give rise to?

Answer 5

neuronal or glial progenitor cells

Question 6

The neural tube epithelium divides to give rise to neuronal lineage progenitor cell. What do neuronal progenitor cells give rise to?

Answer 6

Neurons that transmit electrochemical signals responsible for receptive, integrative and motor functions.

Question 7

Division of the neural tube epithelium gives rise to glial lineage progenitor cells. These glial progenitor cells give rise to what?

Answer 7

Neuroglia: Supporting cells of the CNS. They insulate, nourish, support, and protect neurons.

Question 8

Give the names of each layer of the developing spinal cord.

Answer 8

White space in center= central canal

Green= ventricular layer

purple=mantle layer

gold=marginal layer; contains axons

Question 9

Not really sure what she wanted us to know about this diagram but I think it might be useful to know that the young neurons begin in the ventricular layer and only reach to the mantle layer.

Answer 9

I believe the arrows between the neuroepithelial cells just indicate that this is a pseudostratified tissue and are seen at all layers.

The neuron starts in mantle layer and moves to marginal layer.

The radial glia starts at the ventricular layer and reaches to the marginal layer.

The glioblast (astrocytes/oligodendrocyte cells) are present in the mantle layer and maybe the marginal layer

Question 10

What is the process of cytodifferentiation in neural and glial cells?

Answer 10

Postmitotic neurons and glioblasts migrate forming i_ntermediate mantle or cortical zone_ This becomes the iner grey matter and contains cell bodies and neuroglia.

Neuronal processes (myelinated) move out to surround the developing grey matter and form the outer white matter (also called th marginal zone)

Question 11

What is the intermediate mantle or cortical zone developed from?

Answer 11

The intermediate mantle and cortical zone are developed from the postmitotic neurons and glioblasts. This becomes inner grey matter that contains cell bodies and neuroglia.

Question 12

What is the outer white matter or the marginal zone developed from?

Answer 12

The outer white matter or the marginal zone is developed from the neuronal processes (myelinated) that move out to surround the developing grey matter.

Question 13

What signalling molecule does the roof plate use?

Answer 13

The roof plate(dorsal spinal cord) uses BMP 4 to upregulate a cascade of TGF-beta proteins, including BMP5 and 7, activin, and dorsalin

Question 14

What signaling molecule does the floor plate (ventral spinal cord) use?

Answer 14

The floor plate (ventral spinal cord) uses sonic hedgehog (sHH)

Question 15

With the help of signaling molecules BMP4 and Shh what does the neural tube accomplish?

Answer 15

The neural tube establishes an overlaping gradient involving dorsal and ventral factors that help differentiate neuronal cells into motor or sensory cells within the spinal cord.

Question 16

As the neural tube is differentiating, what is happening to the mesoderm lateral to it?

Answer 16

The mesoderm develops a block called paraxial and another block more lateral called the intermediate mesoderm and then lateral plate mesoderm.

Question 17

True or False. Development of the different regions of the mesoderm is independent of the spatial position of the notochord.

Answer 17

False. The mesoderm is divided into different regions on the basis of spatial position with respect to the notochord.

The mesoderm IS dependent.

Question 18

What is the paraxial mesoderm and what does it give rise to?

Answer 18

Longitudinal blocks of tissue on either side of the notochord. Gives rise to the axial skeleton (bones of the head, vertebrae, and ribs) and skeletal muscle.

Question 19

What is the intermediate mesoderm and what does it give rise to?

Answer 19

cell mass that is just lateral to the paraxial mesoderm and gives rise to the urogenital system

Question 20

What is the lateral plate mesoderm and what does it give rise to?

Answer 20

The lateral plate mesoderm is the outer layer of the embyro and is just lateral to the intermediate mesoderm.It gives rise to connective tissue and skeleton of the limbs and smooth muscle and connective tissue of viscera and blood vessels. It does not give rise to skeletal muscle.

Question 21

What are somitomeres? and how many are there?

Answer 21

Longitudinal blocks derived from the paraxial mesoderm that gives rise to the axial skeleton and skeletal muscle. There are 7 somitomeres and they are located cranially to the somites.

Question 22

What are somites and where are they located? What do they give rise to?

Answer 22

Longitudinal blocks derived from the paraxial mesoderm. They are located on either side of the notochord and give rise to the axial skeleton and skeletal muscle.

Question 23

What is the role of Hox genes?

Answer 23

Hox genes regulate growth and regulation in the head; it tracks neural development and segmentation of mesoderm into somitomeres.

Question 24

What is segmentation of axial mesoderm controlled by?

Answer 24

Segmentation of the axial mesoderm is controlled by oscillations of Hox genes

Question 25

What is derived from the intermediate mesoderm?

Answer 25

urogenital (kidneys and gonads)

Question 26

what is derived from the chordamesoderm?

Answer 26

The notochord

Question 27

What is derived from the paraxial mesoderm?

Answer 27

head and somites that later form skeletal muscle and axial skeleton

Question 28

What derives from the somites?

Answer 28

sclerotome (cartilage), myotome (skeletal muscle), and dermatome (dermis)

Question 29

What is derived form the lateral mesoderm?

Answer 29

splanchnic (circulatory system), somatic (body cavity), extra-embryonic

Question 30

In what direction do the somites form?

Answer 30

They form cranial to caudal.

Question 31

How does gene regulation cause the somites to be segmented?

Answer 31

The gene expression is activated in waves of concentrated signaling. So the blue represents a peak in gene expression and therefore development of a somite and as the signal falls there is a notch created between the somites.

Question 32

What is notch signaling used for?

Answer 32

The notch singaling is protein that creates the notches between the somites. It is an evolutionarily conserved intercellular signaling pathway that regulates interactions between physically adjacent cells. The increase in Notch protein activates other segment-pattering genes that establish the somite.

Question 33

What gradient controls the segmentation clock and activity of the NOTCH pathway?

Answer 33

Retinoic Acid is expressed at high concentrations cranially and decreases in concentration caudally. FGF8 and WNT 3a are expressed in high concentrations caudally and lower concentrations cranially. These overlapping expression gradients control the segmentation clock and activity of NOTCH pathway giving boundaries for each somite.

Question 34

What is the difference in somite development and gene expression between short and long bodied vertebrates?

Answer 34

Long bodied vertebrates, such as snakes, have faster clock-gene expression leading to smaller but many more somites. Shorter-bodied animals have shorter length clock-gene expression leading to less but larger somites.

Question 35

What are the three divisions of the somite?

Answer 35

1) scleratome
2) dermatome
3) myotome

Question 36

What does the dermatome component of the somite develop into?

Answer 36

The dermatome develops into the dermis (under the epidermis of the skin)

Question 37

What does the myotome of the somite develop into?

Answer 37

The myotome develops into the muscles.

Question 38

What does the sclerotome of the somite develop into?

Answer 38

The scleratome develops into the cartilage and vertebrae of the spinal process.

Question 39

What is the sequential order of the layers of the somite (starting laterally and working medially)?

Answer 39

The very outside is the dermatome, then myotome, then sclerotome.