Chapter 11

Question 1

The muscular system develops from the mesodermal germ layer and consists of___, ___, and ____.

Answer 1

skeletal, smooth, and cardiac muscle

Question 2

Smooth muscle differentiates from ___ surrounding the gut and its derivatives and from ectoderm (pupillary, mammary gland, and sweat gland muscles)

Answer 2

Visceral (splanchnic) mesoderm

Question 3

Skeletal muscle is derived from ____, which forms somites from the occipital to the sacral regions and somitomeres in the head

Answer 3

paraxial mesoderm

Question 4

Cardiac muscle is derived from ____ surrounding the heart tube

Answer 4

Visceral (splanchnic) mesoderm

Question 5

Head musculature is derived from seven ___, which are partially segmented whorls of mesenchymal cells derived from paraxial mesoderm

Answer 5

somitomeres

Question 6

Musculature of the axial skeleton, body wall, and limbs is derived from ___, which initially form as somitomeres and extend from the occipital region to the tail bud

Answer 6

somites

Question 7

Immediately after segmentation, these somitomeres undergo a process of ___ and form a “ball” of epithelial cells with a small cavity in the center

Answer 7

epithelization

Question 8

The ventral region of each somite then becomes mesenchymal again and forms the ____, the bone-forming cells for the vertebrae and ribs. Cells in the upper region of the somite form the dermatome and two muscle-forming areas at the ventrolateral (VLL) and dorsomedial (DML) lips (or edges), respectively

Answer 8

sclerotome

Question 9

Cells from these two areas migrate and proliferate to form progenitor muscle cells ventral to the ___, thereby forming the ___

Answer 9

dermatome - dermomyotome

Question 10

Here, they form ___, ____ (rectus abdominis, internal and external oblique, and transversus abdominis), and ___

Answer 10

infrahyoid, abdominal wall - limb muscles

Question 11

The remaining cells in the myotome form muscles of the___, ___, and ___ muscles

Answer 11

back, shoulder girdle, and intercostal

Question 12

Initially, there is a well-defined border between each somite and the parietal layer of lateral plate mesoderm called the ____

Answer 12

lateral somitic frontier

Question 13

The ___ that comprises the region around the neural tube and containsonly somite-derived (paraXial mesoderm) cells

Answer 13

primaxial domain

Question 14

The ___ that consists of the parietal layer of lateral plate mesoderm together with somite cells that have migrated across the lateral somitic frontier

Answer 14

abaxial domain

Question 15

Muscle cells that cross this frontier (those from the VLL edge of the myotome) and enter the lateral plate mesoderm comprise the ____ muscle cell precursors and receive many of their signals for differentiation from lateral plate mesoderm

Answer 15

abaxial

Question 15

the paraxial mesoderm and do not cross the frontier (the remaining VLL cells and all of the DML cells) comprise the ___ muscle cell precursors and receive many of their developmental signals from the neural tube and notochord

Answer 15

primaxial

Question 16

Origins of muscles Cervical region, primaxial precursors

Answer 16

Scalenes
Geniohyoid
Prevertebra

Question 17

Origins of muscles Cervical region, abaxial precursors

Answer 17

Infrahyoid

Question 18

Origins of muscles Thoracoabdominal region, abaxial precursors

Answer 18

Pectoralis major and minor
External oblique
Internal oblique
Transversus abdominis
Sternalis
Rectus abdominis
Pelvic diaphragm

Question 18

Origins of muscles Thoracoabdominal region, primaxial precursors

Answer 18

Intercostals

Question 19

Origins of muscles Upper limb, primaxial precursors

Answer 19

Rhomboids
Levator scapulae
Latissimus dorsi

Question 20

Origins of muscles Upper limb, abaxial precursors

Answer 20

Distal limb muscles

Question 20

The new description is based on the actual ___ of muscle cells from two different populations of muscle cell precursors, the abaxial and primaxial cells, and not their innervation

Answer 20

embryological origin

Question 21

During differentiation, precursor cells, the ___, fuse and form long, multinucleated muscle fibers

Answer 21

myoblasts

Question 22

Origins of muscles Lower limb, abaxial precursors

Answer 22

All lower muscles

Question 23

___ for the attachment of muscles to bones are derived from sclerotome cells lying adjacent to myotomes at the anterior and posterior borders of somites

Answer 23

Tendons

Question 24

The transcription factor ___ regulates development of tendons

Answer 24

SCLERAXIS

Question 25

Both MyoD and MYF5 are members of a family of transcription factors called ___, and this group of genes activates pathways for muscle development.

Answer 25

myogenic regulatory factors (MRFs)

Question 26

In the head region, these connective tissues are derived from ___; in cervical and occipital regions, they differentiate from __; and in the body wall and limbs, they originate from the ___

Answer 26

neural crest cells - somitic mesoderm - parietal layer of lateral plate mesoderm

Question 27

Somitomeres1 and 2, muscles and innervation

Answer 27

Superior, medial, ventral recti - Oculomotor [III]

Question 28

Somitomeres 3, muscles and innervation

Answer 28

Superior oblique - Trochlear 4

Question 29

Somitomeres 4, muscles and innervation

Answer 29

Jaw closing - Trigeminal 5

Question 30

Somitomeres 5, muscles and innervation

Answer 30

Lateral rectus - Abducens 6

Question 31

Somitomeres 6, muscles and innervation

Answer 31

Jaw opening, other second arch - Facial 7

Question 32

Somitomeres 7, muscles and innervation

Answer 32

Stylopharyngeus - Glossopharyngeal 9

Question 33

Somitomeres 1 and 2, muscles and innervation

Answer 33

Intrinsic laryngeals - Vagus 10

Question 34

Somitomeres 2-5, muscles and innervation

Answer 34

Tounge - Hypoglossal 12

Question 35

___ is a transcription factor responsible for smooth muscle cell differentiation. This factor is upregulated by growth factors through kinase phosphorylation pathways

Answer 35

Serum response factor (SRF)

Question 36

Partial or complete absence of a muscle is common and usually not debilitating. Examples include partial or complete absence of the palmaris longus, serratus anterior, or quadratus femoris muscles. A more serious defect is called ___

Answer 36

Poland sequence

Question 37

___ and ____ then act as co-activators to enhance the activity of SRF, thereby initiating the genetic cascade responsible for smooth muscle development

Answer 37

Myocardin and myocardin-related transcription factors (MRTFs)

Question 38

Partial or complete absence of abdominal musculature is called ____. Usually, the abdominal wall is so thin that organs are visible and easily palpated

Answer 38

prune belly syndrome

Question 39

___ is the term for a group of inherited muscle diseases that cause progressive muscular wasting and weakness

Answer 39

Muscular dystrophy

Question 40

There are a large number of these types of diseases of which ___ is the most common [1 per 4,000 male births]

Answer 40

Duchenne muscular dystrophy [DMD]

Question 41

The disease is inherited as ___ such that males are much more often affected than females.

Answer 41

X-linked recessive

Question 42

Both DMD and___ are caused by mutations in the gene for dystrophin on the X chromosome

Answer 42

Becker muscular dystrophy [BMD]