Myofibrils and Heart Conduction System

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Questions and Answers

What role does Bone morphogenetic protein 4 (BMP4) play in muscle development?

It is involved in the formation of muscle vascularization.

It signals dermomyotome cells to produce MyoD. (correct)

It directly stimulates muscle contraction.

It provides nutritional support for muscle cells.

Which proteins are secreted by the notochord and floor plate of the neural tube during muscle development?

WNT proteins

Sonic hedgehog (SHH) proteins (correct)

Fibroblast growth factors

BMP4 proteins

Which cells are indicated to be influenced by WNT proteins from the dorsal neural tube?

Abaxial muscle cells

Ventral dermomyotome cells

VLL cells of the dermomyotome (correct)

Primaxial muscle cells

In the context of muscle development, what distinguishes primaxial domains from abaxial domains?

Primaxial domains derive from the dermomyotome. Signup and view all the answers

What is the difference between epimeres and hypomeres in muscle classification?

Epimeres correspond to axial muscles, while hypomeres correspond to limb and body wall muscles. Signup and view all the answers

What is a characteristic feature of Poland sequence?

Absence or displacement of nipple and areola Signup and view all the answers

Poland sequence is primarily attributed to which type of tissue development?

Connective tissue derived from parietal layer of lateral plate mesoderm Signup and view all the answers

What unusual digital defects may occur in individuals with Poland sequence?

Syndactyly - fused digits Signup and view all the answers

Cardiac muscle myofibrils share similarities with which type of muscle?

Skeletal muscle, but will not fuse Signup and view all the answers

What component facilitates the adherence of myoblasts in developing cardiac muscle?

Intercalated discs Signup and view all the answers

Which of the following statements about Poland sequence is FALSE?

It involves complete absence of pectoralis major muscle Signup and view all the answers

The muscles in the head and neck during the embryonic stage are derived from which source?

Somitomeres and myotomes Signup and view all the answers

What is the result of cardiac muscle development from splanchnic mesoderm?

Development of specialized cardiac structures Signup and view all the answers

Which type of muscle is derived from the splanchnic layer of lateral plate mesoderm?

Smooth muscle Signup and view all the answers

Which transcription factor is primarily responsible for smooth muscle differentiation?

Serum Response Factor (SRF) Signup and view all the answers

What role do Myocardin and MRTFs play in smooth muscle development?

They enhance the activity of SRF. Signup and view all the answers

From where does the mesenchyme that contributes to limb musculature originate?

Dorsolateral cells of the somites Signup and view all the answers

When is the first indication of limb musculature observed during development?

Week seven Signup and view all the answers

What initiates the genetic cascade responsible for smooth muscle development?

Growth factors and SRF Signup and view all the answers

What is NOT a derived structure from the ectoderm?

Smooth muscle in the gut wall Signup and view all the answers

Which somite group contributes to the development of the craniofacial muscles?

Somites 2 to 5 Signup and view all the answers

What comprises the abaxial muscle cell precursors?

Muscle cells that cross the lateral somitic frontier into the lateral plate mesoderm Signup and view all the answers

Which cells are primarily responsible for forming tendons during muscle development?

Scleraxis - transcription factor Signup and view all the answers

Which region do the VLL cells migrate to in muscle development?

Into the parietal layer of lateral plate mesoderm Signup and view all the answers

What is formed from cells at the DML and VLL regions of the somite?

Dermomyotome Signup and view all the answers

What differentiates the primaxial mesodermal domain from the abaxial mesodermal domain?

It only comprises somitic cells Signup and view all the answers

From where do primaxial muscle cell precursors primarily receive their developmental signals?

From the neural tube and notochord Signup and view all the answers

What do somite-derived cells contribute to in the context of muscle cell formation?

The abaxial mesodermal domain Signup and view all the answers

What is the primary origin of muscle cell precursors in the ventral region ventral to the dermatome?

Cells from the dermomyotome Signup and view all the answers

What is a characteristic feature of Prune Belly Syndrome?

Visible organs due to thin abdominal wall Signup and view all the answers

Which embryonic origin is responsible for smooth muscle in coronary arteries?

Neural crest cells Signup and view all the answers

Which signal induces VIL in the development of smooth muscle?

WNT from lateral plate mesoderm Signup and view all the answers

What type of musculature is affected in Prune Belly Syndrome?

Smooth abdominal musculature Signup and view all the answers

What causes the accumulation of fluid in the abdomen associated with Prune Belly Syndrome?

Urethral obstruction Signup and view all the answers

What does the connective tissue generate in muscle pattern establishment?

Muscle pattern templates Signup and view all the answers

Which signals from the notochord induce DML cells?

SHH and WNT Signup and view all the answers

From which embryonic layer are the smooth muscles of the dorsal aorta and large arteries derived?

Lateral plate mesoderm and neural crest cells Signup and view all the answers

Study Notes

Myofibril Formation and Muscle Development

Distributed myofibrils emerge during later stages of muscular development.
Cardiac conduction fibers originate from specialized muscle cells crucial for heart function.
Smooth muscle in large arteries and the dorsal aorta develops from lateral plate mesoderm and neural crest cells.

Prune Belly Syndrome

Characterized by partial or complete absence of abdominal muscles, leading to visible and palpable organs.
Common malformations include urinary tract defects and bladder issues, such as urethral obstruction.
This condition can result in fluid accumulation in the abdomen, causing muscle atrophy.

Poland Sequence

Occurs in approximately 1 in 20,000 individuals.
Noted for the absence of the pectoralis minor muscle and partial loss of the pectoralis major, specifically the sternal head.
Accompanying symptoms may include nipple and areola displacement and digital defects such as syndactyly and brachydactyly.

Cardiac Muscle Development

Cardiac muscle arises from splanchnic mesoderm around the endothelial heart tube.
Myoblasts form intercalated discs through cell adhesion, essential for cardiac function.
Purkinje fibers, unique muscle cell bundles, develop from remaining embryonic muscle cells.

Dermomyotome and Muscle Patterning

Dermomyotome is derived from the combination of ventrolateral (VLL) and dorsomedial (DML) cells.
Abaxial muscle cell precursors migrate into lateral plate mesoderm, influenced by signals from the neural tube and notochord.
Primaxial muscle cells remain in the paraxial mesoderm, relying on locally sourced developmental signals.

Molecular Regulation of Muscle Development

Bone morphogenetic protein 4 (BMP4) and fibroblast growth factors guide differentiation in muscle cells.
WNT proteins stimulate VLL cells to express muscle-specific gene MyoD, vital for muscle development.
Sonic hedgehog (SHH) signaling from the notochord also impacts the DML cells for muscle patterning.

Innervation of Axial Skeletal Muscles

Each myotome is innervated by spinal nerves from the same segment, ensuring coordinated function.
New classification of muscle development splits muscles into primaxial (back) and abaxial (limb) domains, replacing older definitions based on innervation styles.

Smooth Muscle Sources

Smooth muscle in the gut wall and related organs arises from the splanchnic layer of lateral plate mesoderm.
Sphincter muscles, pupil muscles, and glandular tissues come from ectoderm.
Serum Response Factor (SRF) is crucial for smooth muscle differentiation, influenced by growth factors and signaling pathways.

Limb Musculature

Initial limb musculature appears in week 7 of embryonic development as mesenchymal condensation.
This mesenchyme originates from dorsolateral somite cells that migrate to limb buds to establish the muscular framework.

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Description

Explore the development of myofibrils and their role in the heart's conduction system. Learn about Prune Belly Syndrome, which is characterized by a lack of abdominal musculature. This quiz covers the importance of these physiological concepts in human anatomy.