10. Muscular System Devo

Question 1

Skeletal Muscle progenitor tissue

Answer 1

Myotome tissue of the somites Head mesoderm

Question 2

Iris muscles, arrector pili muscles,

myoepithelial cells of mammary gland from which progenitor tissue

Answer 2

ectoderm

Question 3

ciliary muscles are from what progenitor tissue

Answer 3

neural Crest

Question 4

Cardiac muscle from what progenitor

Answer 4

Splanchnic mesoderm of heart fields

Question 5

Skeletal muscle forms from the______. Under the influence of______ from the surface ectoderm the dorsal half of the somite remains an epithelium and is called the _______

Answer 5

somite
Wnt
Dermomyotome (DM).

Question 6

During skeltal muscle formation, cells of the DM are exposed and influenced by a gradient of signaling molecules from the

Answer 6

dorsal neural tube and notochord, surface ectoderm and lateral mesoderm.

Question 7

Cells at the medial edge or lip of the DM are primarily influenced by signals ________from the
dorsal neural tube and notochord. These cells undergo an (EMT) and travel where?

Answer 7

(Wnt & Shh)

migrate beneath the remaining epithelial cells of the DM.

Question 8

Cells at the lateral edge or lip of the DM are primarily influenced by signals ______ from the lateral mesoderm. They also undergo an EMT and go where?

Answer 8

(Bmp)

migrate beneath the DM epithelium.

Question 9

The mesenchyme cells beneath the DM become and

Answer 9

Myogenic (skeletal muscle precursor) Cells

Question 10

The mesenchyme cells beneath the DM become Myogenic (skeletal muscle precursor) Cells and begin to express

Answer 10

Myogenic Regulatory Factors (e.g. Myf5 and MyoD)

Question 11

The mesenchyme cells beneath the DM become Myogenic (skeletal muscle precursor) Cells and are called

Answer 11

Myotomes

Question 12

muscle precursor cells from the central DM as a result of signals from the _______ These cells undergo an EMT and join the myogenic cells in the myotome.

Answer 12

overlying surface ectoderm.

Question 13

Many of the central DM derived muscle precursors will

become _______ associated with differentiated skeletal muscle cells.

Answer 13

the satellite cells

Question 14

myogenic cells derived from the somites develop in one of two domains. The domains are separated by a boundary called the _________ that is located between the paraxial and lateral mesoderm.

Answer 14

Lateral Somite Frontier (LSF)

Question 15

boundary is and interface created by the opposing gradients of signaling molecules from the lateral mesoderm and the dorsal neural tube and
notochord.

Answer 15

Lateral Somite Frontier (LSF)

Question 16

The domain located medial to the LSF is the _______, while that lateral to the LSF is the Abaxial Domain. muscles forming in the here attach to bones derived from scleratome cells.

Answer 16

Primaxial Domain

Question 17

The domain located lateral to the LSF is the _______,

Answer 17

Abaxial Domain.

Question 18

can proliferate and migrate or become displaced by differenential growth… eventually they become postmitotic and are then called _______

Answer 18

Myogenic Cells

Myoblasts

Question 19

Myoblasts begin to express additional myogenic regulatory factors (e.g. myogenin, Mef2, Myf4) and begin to produce

Answer 19

myosin and actin.

Question 20

Myoblasts in the chains fuse with each other by upregulating cell adhesion molecules to form ________which undergo further differentiation to become ________

Answer 20

Multinucleated Myotubes.

Primary Muscle Fibers.

Question 21

Cardiac muscle forms from

Answer 21

splanchnic mesoderm of the primary and secondary

heart fields.

Question 22

Cardiac myoblasts retain the capability to divide, but do not fuse into myotubes. Instead they……

Answer 22

they branch and form junctional complexes with each other resulting in a functional syncytium.

Question 23

Visceral Smooth Muscle (associated with GI, Respiratory, UG organs) Visceral smooth muscle cells are derived from

Answer 23

splanchnic mesoderm.

Question 24

master regulatory factors that control smooth muscle development.

Answer 24

Myocardin and serum response factor

Question 25

Vascular Smooth Muscle Precursor cells for vascular smooth muscle are derived from

Answer 25

local mesenchyme that surrounds forming endothelial tubes.

Question 26

Pre-muscle masses may “remodel” into specific muscles by:

Answer 26

Fusion of adjacent myotomes
Splitting longitudinally into parts (bellies) or tangentially into layers
changing fiber direction
atrophy of portions of the muscle mass
migrate or are displaced to regions remote from their
origin at the myotome.

Question 27

Skeletal muscle is derived from myotomes in the trunk are innervated by

Answer 27

spinal nerves,

Question 28

skeletal muscle derived from head mesoderm or occipital

somites is innervated by .

Answer 28

cranial nerves

Question 29

myotomes in the trunk split have traditionally be subdivided into what two portions

Answer 29

Epaxial portion Hypaxial portion

Question 30

Epaxial portion is innervated by

Answer 30

branches of the Dorsal Primary Ramus of a spinal nerve

Question 31

Hypaxial portion innervated by

Answer 31

branches of the ventral primary ramus of a spinal nerve

Question 32

refer to domains (regions) of the embryo in which myotomes cells develop into specific skeletal muscles.

Answer 32

primaxial and abaxial

Question 33

terms used to designate which skeletal muscles are

innervated by branches of the ventral primary ramus or dorsal primary ramus of a spinal nerve.

Answer 33

Hypaxial and epaxial ar

Question 34

All muscles developing in the abaxial domain are innervated by

Answer 34

ventral primary rami.

Question 35

With respect to muscles developing in the Primaxial
domain, the intrinsic back muscles are innervated by branches of the _______, and branches of __________ innervate all other Primaxial muscles.

Answer 35

dorsal primary rami

ventral primary rami

Question 36

family of genetic diseases that cause progressive

deterioration of skeletal muscle. The nervous system is not affected.

Answer 36

Muscular dystrophy

Question 37

X-linked and affects boys in early childhood. The skeletal muscle myocytes are susceptible to damage when physically stressed due to a lack of Dystrophin, an actin binding glycoprotein.

Answer 37

Duchennes

Question 38

fixed rotation of the head to one side is caused by a defect or deformation of the sternocleidomastoid muscle

Answer 38

Torticollis

Question 39

Congenital torticollis is often acquired due to birth injury to the _________. It can also occur in childhood as a secondary effect of infections or trauma.

Answer 39

sternocleidomastoid muscle

Question 40

condition in which the muscles of the abdominal wall

are absent. It is often associated with anomalies of the urinary bladder and urinary tract or urethral obstruction.

Answer 40

Prune Belly syndrome

Question 41

is a condition characterized by absence of the pectoralis
major (usually sternocostal head) and pectoralis minor muscles. This influences nipple placement and axillary fold morphology on the affected side.

Answer 41

Poland sequence

Question 42

Associated anomalies of Poland sequence

Answer 42

absence of breast tissue, hypoplasia of the rib cage and

upper limb defects.

Question 43

Poland sequence is more common on the____ side, is more prevalent in ——– and has a frequency of 1/20,000 – 1/50,000 births

Answer 43

right

males

Question 44

muscles forming in the here attach to bones derived from scleratome cells.

Answer 44

Primaxial Muscle Domain

Question 45

Muslces of ventrolateral abdominal wall and limbs

Answer 45

Abaxial Muscle Domain