Developmental Origins of Muscle Flashcards
From which germ layer does muscle arise?
Mesoderm.
List the structures that give rise to skeletal muscle (mesoderm derivatives).
Paraxial mesoderm, somites, myotome, skeletal muscle.
List the structures that eventually give rise to cardiac and some smooth muscle.
Lateral plate mesoderm, splanchnic, cardiac and smooth.
List the three compartments of a somite and what each gives rise to.
Sclerotome- vertebrae and rib cartilage
Myotome- musculature of the back, limbs and ribs
Dermatome- dermis of back.
Interaction of the somite with which structure gives rise to skeletal muscle?
Dorsal neural tube.
Do the somite cells that interact with the dorsal or the ventral part of the neural tube form skeletal muscle?
Dorsal.
What are the precursor cells of myocytes?
Myoblasts.
What are the two sections that the myotome splits into and what does each give rise to?
Epimere- back muscle
Hypomere- thorax and abdominal muscles
The spinal nerves divide to support the myotome. Which division supports which part of the myotome?
Dorsal rami- epimere (back muscle)
Ventral rami- hypomere (thorax and abdominal muscle)
Describe the stages of progression from a myoblast to a myocyte.
Myoblasts frequently divide
Form a syncytial myotube/muscle fibre
Nuclei are first central then move to the periphery
Produce contractile filaments throughout develppment.
How can we visualise fused muscle cells?
When cells fuse, they produce myosin, which can be stained with DAPI.
What is the smallest contractile unit of muscle?
Sarcomere.
What is the effect of either a MyoD or myf-5 KO on muscle formation?
No effect, muscle development is normal.
What is the effect of MyoD and myf-5 KO on muscle formation?
Muscle formation fails.
What signalling molecules negatively regulates muscle formation?
Myostatin, member of the TGF-beta family of signalling molecules.
What is the function of myostatin?
Negatively regulate muscle formation and stop muscle growth when it has reached normal size.
What family of signalling molecules does myostatin belong to?
TGF-beta.
What are type I muscle fibres?
Slow twitch fibres
What are type II muscle fibres?
Fast twitch fibres
What are the two types of fast twitch (type II) muscle fibres?
Oxidative (type II-a) and glycolytic (type II-b)
What is a satellite cell?
Cells within the basal laminar involved in fibre growth and regeneration. Proliferate and fuse to form regenerating muscle fibres.
Possibly, persistent myoblasts
What are the two types of smooth muscle?
Multiunit and visceral
Describe multiunit smooth muscle.
Functionally independent cells, often innervated by a single nerve, never contract simultaneously, derived from local mesoderm.
Describe visceral smooth muscle.
Bundles of cells connected by gap junctions. Contract simultaneously when stretch at a threshold. Derived from splanchnic mesoderm.
