Chapter 11 Flashcards
The muscular system develops from the mesodermal germ layer and consists of___, ___, and ____.
skeletal, smooth, and cardiac muscle
Smooth muscle differentiates from ___ surrounding the gut and its derivatives and from ectoderm (pupillary, mammary gland, and sweat gland muscles)
Visceral (splanchnic) mesoderm
Skeletal muscle is derived from ____, which forms somites from the occipital to the sacral regions and somitomeres in the head
paraxial mesoderm
Cardiac muscle is derived from ____ surrounding the heart tube
Visceral (splanchnic) mesoderm
Head musculature is derived from seven ___, which are partially segmented whorls of mesenchymal cells derived from paraxial mesoderm
somitomeres
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
somites
Immediately after segmentation, these somitomeres undergo a process of ___ and form a “ball” of epithelial cells with a small cavity in the center
epithelization
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
sclerotome
Cells from these two areas migrate and proliferate to form progenitor muscle cells ventral to the ___, thereby forming the ___
dermatome - dermomyotome
Here, they form ___, ____ (rectus abdominis, internal and external oblique, and transversus abdominis), and ___
infrahyoid, abdominal wall - limb muscles
The remaining cells in the myotome form muscles of the___, ___, and ___ muscles
back, shoulder girdle, and intercostal
Initially, there is a well-defined border between each somite and the parietal layer of lateral plate mesoderm called the ____
lateral somitic frontier
The ___ that comprises the region around the neural tube and containsonly somite-derived (paraXial mesoderm) cells
primaxial domain
The ___ that consists of the parietal layer of lateral plate mesoderm together with somite cells that have migrated across the lateral somitic frontier
abaxial domain
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
abaxial
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
primaxial
Origins of muscles Cervical region, primaxial precursors
Scalenes
Geniohyoid
Prevertebra
Origins of muscles Cervical region, abaxial precursors
Infrahyoid
Origins of muscles Thoracoabdominal region, abaxial precursors
Pectoralis major and minor
External oblique
Internal oblique
Transversus abdominis
Sternalis
Rectus abdominis
Pelvic diaphragm
Origins of muscles Thoracoabdominal region, primaxial precursors
Intercostals
Origins of muscles Upper limb, primaxial precursors
Rhomboids
Levator scapulae
Latissimus dorsi
Origins of muscles Upper limb, abaxial precursors
Distal limb muscles
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
embryological origin
During differentiation, precursor cells, the ___, fuse and form long, multinucleated muscle fibers
myoblasts
Origins of muscles Lower limb, abaxial precursors
All lower muscles
___ for the attachment of muscles to bones are derived from sclerotome cells lying adjacent to myotomes at the anterior and posterior borders of somites
Tendons
The transcription factor ___ regulates development of tendons
SCLERAXIS
Both MyoD and MYF5 are members of a family of transcription factors called ___, and this group of genes activates pathways for muscle development.
myogenic regulatory factors (MRFs)
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 ___
neural crest cells - somitic mesoderm - parietal layer of lateral plate mesoderm
Somitomeres1 and 2, muscles and innervation
Superior, medial, ventral recti - Oculomotor [III]
Somitomeres 3, muscles and innervation
Superior oblique - Trochlear 4
Somitomeres 4, muscles and innervation
Jaw closing - Trigeminal 5
Somitomeres 5, muscles and innervation
Lateral rectus - Abducens 6
Somitomeres 6, muscles and innervation
Jaw opening, other second arch - Facial 7
Somitomeres 7, muscles and innervation
Stylopharyngeus - Glossopharyngeal 9
Somitomeres 1 and 2, muscles and innervation
Intrinsic laryngeals - Vagus 10
Somitomeres 2-5, muscles and innervation
Tounge - Hypoglossal 12
___ is a transcription factor responsible for smooth muscle cell differentiation. This factor is upregulated by growth factors through kinase phosphorylation pathways
Serum response factor (SRF)
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 ___
Poland sequence
___ and ____ then act as co-activators to enhance the activity of SRF, thereby initiating the genetic cascade responsible for smooth muscle development
Myocardin and myocardin-related transcription factors (MRTFs)
Partial or complete absence of abdominal musculature is called ____. Usually, the abdominal wall is so thin that organs are visible and easily palpated
prune belly syndrome
___ is the term for a group of inherited muscle diseases that cause progressive muscular wasting and weakness
Muscular dystrophy
There are a large number of these types of diseases of which ___ is the most common [1 per 4,000 male births]
Duchenne muscular dystrophy [DMD]
The disease is inherited as ___ such that males are much more often affected than females.
X-linked recessive
Both DMD and___ are caused by mutations in the gene for dystrophin on the X chromosome
Becker muscular dystrophy [BMD]
