Musculoskeletal System - Muscle Development
|Embryology - 5 Jun 2020 Expand to Translate|
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|contributors to the site. The good news is Embryology will remain online and I will continue my association with UNSW Australia. I look forward to updating and including the many exciting new discoveries in Embryology!|
- 1 Introduction
- 2 Some Recent Findings
- 3 Myogenesis
- 4 Muscle Groups
- 5 Skeletal Muscle Stages
- 6 Muscle Fibre Types
- 7 Muscle Contraction
- 8 Myotome
- 9 Mouse Limb Muscle
- 10 Histology Images
- 11 Puberty
- 12 Abnormalities
- 13 References
- 14 Additional Images
- 15 External Links
- 16 Glossary Links
There are 3 different types of muscle: skeletal, cardiac and smooth. This page describes skeletal muscle development, descriptions of cardiac muscle and smooth muscle development can be found in other notes. Skeletal muscle forms by fusion of mononucleated myoblasts to form mutinucleated myotubes.
Differentiation/determination of mesoderm into muscle cells is thought to involve a family of basic Helix-Loop-Helix transcription factors, the first of which discovered was MyoD1. MyoD1 needs to form a dimer to be active and is maintained in an inactive state by binding of an inhibitor, Id.
Some Recent Findings
|More recent papers|
This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.
Search term: Muscle Development
<pubmed limit=5>Muscle Development</pubmed>
Three different types of muscle form in the body.
- Skeletal muscle - cells originate from the paraxial mesoderm, forming somites, then dermamyotome and finally the myotome. Myoblasts undergo frequent divisions and coalesce with the formation of a multinucleated, syncytial muscle fibre or myotube. The nuclei of the myotube are still located centrally in the muscle fibre. In the course of the synthesis of the myofilaments/myofibrils, the nuclei are gradually displaced to the periphery of the cell.
- Cardiac muscle - cells originate from the prechordal splanchnic mesoderm.
- Smooth muscle - cells originate from undifferentiated mesenchymal cells. These cells differentiate first into mitotically active cells, myoblasts, which contain a few myofilaments. Myoblasts give rise to the cells which will differentiate into mature smooth muscle cells.
Anatomical term describing skeletal muscles which lie dorsal (posterior) to the vertebral column developing from the somite myotome. In humans, this is only a small muscle group formed by the transversospinalis, longissimus, and iliocostalis muscles. Also at the ribcage level the levatores costarum muscles involved with rib elevation during respiration. The body muscles lying ventral (anterior) to the vertebral column are the hypaxial muscles.
(hypomere) Anatomical term describing skeletal muscles which lie ventral (anterior) to the vertebral column developing from the somite myotome. These muscles contribute both body (trunk) and limb skeletal muscle.
- In the trunk, these form the three anterior body muscle layers.
- In the limb, these form the extensor and flexor muscle groups.
- jaw associated muscles mainly from cranial mesoderm.
- jaw, connective tissues and tendons from neural crest cells.
Head muscle precursor myoblast summary from a review.
- myoblasts for the tongue muscle, migrate like those seen in the limb.
- myoblasts for extraocular muscles, condense within paraxial mesoderm, then cross the mesoderm:neural crest interface en route to periocular regions.
- myoblasts for branchial muscle, establish contacts with neural crest populations before branchial arch formation and maintain these relations through subsequent stages of development.
See also for head muscle and connective tissue.
Skeletal Muscle Stages
Myoblast - individual progenitor cells
Myotube - multinucleated, but undifferentiated contractile apparatus (sarcomere)
Myofibre (myofiber, muscle cell) - multinucleated and differentiated sarcomeres
- primary myofibres - first-formed myofibres, act as a structural framework upon which myoblasts proliferate, fuse in linear sequence
- secondary myofibers - second later population of myofibres that form surrounding the primary fibres.
Muscle Fibre Types
Muscle fiber types
- type IIB, IIA, IIX, and I fibres - based only on the myosin ATPase activity.
- Type I fibres appear red, due to the presence of myoglobin.
- Type II fibres appear white, due to the absence of myoglobin and their glycolytic nature.
- A group of individual myofibres within a muscle will be innervated by a single motor neuron (motor unit).
- The electrical properties of the motor neuron will regulate the contractile properties of all associated myofibres.
|Fibre Type||Type I fibres||Type II a fibres||Type II x fibres||Type II b fibres|
|Contraction time||Slow||Moderately Fast||Fast||Very fast|
|Size of motor neuron||Small||Medium||Large||Very large|
|Resistance to fatigue||High||Fairly high||Intermediate||Low|
|Activity Used for||Aerobic||Long-term anaerobic||Short-term anaerobic||Short-term anaerobic|
|Maximum duration of use||Hours||<30 minutes||<5 minutes||<1 minute|
|Power produced||Low||Medium||High||Very high|
|Major storage fuel||Triglycerides||Creatine phosphate, glycogen||Creatine phosphate, glycogen||Creatine phosphate, glycogen|
|Myosin heavy chain,
Individual myoblasts in the developing muscle bed initial fuse together to form multi-nucleated myotubes. These myotubes then express the contractile proteins, that are organized into sarcomeres in series along the length of the myotube.
This animation shows the molecular interactions that occur within the skeletal muscle sarcomere between actin and myosin during skeletal muscle contraction.
In both development and the adult, the group of skeletal muscles supplied by a specific segmental spinal nerve is referred to as a myotome. The muscle arises from a specific somite and the spinal nerve arises from a specific level of the spinal cord (identified by veretebral column).
In humans this corresponds to the following spinal nerves (from top to bottom) and muscular functions:
- C3,4 and 5 supply the diaphragm for breathing.
- C5 supply shoulder muscles and muscles to bend our elbow.
- C6 for bending the wrist back.
- C7 for straightening the elbow.
- C8 bends the fingers.
- T1 spreads the fingers.
- T1 –T12 supplies the chest wall and abdominal muscles.
- L2 bends the hip.
- L3 straightens the knee.
- L4 pulls the foot up.
- L5 wiggles the toes.
- S1 pulls the foot down.
- S3,4 and 5 supply the bladder, bowel, sex organs, anal and other pelvic muscles.
Mouse Limb Muscle
Change in cell types and tissue formation as a function of mouse developmental stage.
- Links: Mouse Development
- Muscle Histology: Muscle Development | Human HE x4 longitudinal and transverse | Human HE x40 transverse | Human HE x40 longitudinal | Human HE x40 longitudinal | Human HE x4 longitudinal and transverse | Muscle Spindle HE x40 | Human HE x40 | Human HE x40 | Human HE x40 | Human HE x100 | Human HE x100 | Fetal human muscle | Myotendinous junction label | Myotendinous junction HE x40 | Whipf 1 | Whipf 2 | Whipf 3 | Tongue HE x10 transverse | Tongue x100 | Muscle spindle HE x20 | Muscle spindle HE x40
Electron Microscopy Virtual Slides
Electron micrographs below are thin longitudinal section cut through adult human skeletal muscle tissue.
Image Source: Contributed by Dartmouth College Electron Microscope Facility special thanks to Chuck Daghlian and Louisa Howard. Gallery. Original images may have been altered in size contrast and labelling. (These images are in the public domain)
- Musculoskeletal mass doubles by the end of puberty
- regulated growth by - sex steroid hormones, growth hormone, insulin-like growth factors
- accumulation of (peak) bone mass during puberty relates to future osteoporosis in old age
There can be abnormalities associated directly with muscle differentiation and function as well as those mediated indirectly by abnormalities of innervation or skeletal development and other associated systems.
Duchenne Muscular Dystrophy
The most common occuring in Boys and in Duchenne Muscular Dystrophy (DMD). This cause of the disease was discovered in 1988 as a mutation in dystrophin, a protein that lies under the muscle fiber membrane and maintains the cell's integrity. As skeletal muscles have little prenatal load or use it is not until postnatally that muscle wasting occurs, usually in the anti-gravity muscles first. This is a progressive disease usually detected between 3-5 years old.
- X-linked dystrophy
- large gene encoding cytoskeletal protein - Dystrophin
- progressive wasting of muscle, die late teens
Becker Muscular Dystrophy
A milder adult (30-40 years old) onset form of the disease Becker's Muscular Dystrophy (BMD) that involves mutations in the same dystrophin gene.
Autosomal Recessive Muscular Dystrophy
Dystroglycan, a protein that associates with both dystrophin and membrane molecules, is a candidate gene for the site of the mutation in autosomal recessive muscular dystrophies. A knockout mouse has been generated that has early developmental abnormalities.
An inherited disorder in which the muscles contract but have decreasing power to relax. With this condition, the muscles also become weak and waste away. The myotonic dystrophy gene, found on chromosome 19, codes for a protein kinase that is found in skeletal muscle, where it likely plays a regulatory role. The disease is "amplified" through generations probably by a similar GC expansion associated with Huntington disease.
Facioscapulohumeral muscular dystrophy (FSHD)
- characterized by the progressive weakness and atrophy of a specific subset of skeletal muscles.
- mostly affects the muscles of the face, scapula, and upper arms.
- involvement of specific muscles that it is often used clinically to distinguish FSHD from other forms of muscular dystrophy.
<pubmed>22274696</pubmed> <pubmed>21621065</pubmed> <pubmed>21183656</pubmed> <pubmed>20553711</pubmed> <pubmed>19762225</pubmed> <pubmed>16118057</pubmed>
<pubmed>21859860</pubmed> <pubmed>20195544</pubmed> <pubmed>20037161</pubmed> <pubmed>19198652</pubmed>
June 2010 " Skeletal Muscle Development" All (19316) Review (2515) Free Full Text (5587)
Search Pubmed: Skeletal Muscle Development
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Cite this page: Hill, M.A. (2020, June 5) Embryology Musculoskeletal System - Muscle Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Musculoskeletal_System_-_Muscle_Development
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G