Musculoskeletal System - Muscle Development: Difference between revisions
Line 11: | Line 11: | ||
|-bgcolor="F5FAFF" | |-bgcolor="F5FAFF" | ||
| | | | ||
* '''The expression pattern of myogenic regulatory factors MyoD, Myf6 and Pax7 in postnatal porcine skeletal muscles'''<ref><pubmed>20888930</pubmed></ref> "The MyoD, Myf6 genes, which belong to the family of muscle regulatory factors (MRFs) play a major role in muscle growth and development. These basic helix-loop-helix (bHLH) transcription factors regulate myogenesis: they initiate the formation of muscle fibres and regulate the transcription of muscle specific genes. The paired-box transcription factor Pax7 plays critical roles during fetal development and this protein is essential for renewal and maintenance of muscle stem cells. In particular, expression of Pax7 and MyoD is correlated with presence of active satellite cells, important in hyperplastic and hypertrophic growth in skeletal muscle." | |||
* '''Expression of Gα(z) in C2C12 cells restrains myogenic differentiation'''PMID20946953 "The recent identification of Gα(z) expression in C2C12 myoblasts and its demonstrated interaction with the transcription factor Eya2 inferred an unanticipated role of Gα(z) in muscle development.In the present study, endogenous Gα(z) mRNA and protein expressions in C2C12 cells increased upon commencement of myogenesis and peaked at around 4-6days after induction but were undetectable in adult skeletal muscle. " | |||
|} | |} | ||
==Myogenesis== | ==Myogenesis== | ||
[[File:Stage11 sem100c.jpg|thumb|Somites in human embryo ([[Carnegie stage 11]])]] | [[File:Stage11 sem100c.jpg|thumb|Somites in human embryo ([[Carnegie stage 11]])]] |
Revision as of 09:04, 2 November 2010
Introduction
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
|
Myogenesis
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.
Muscle Groups
Epaxial Muscle
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.
Hypaxial Muscle
(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.
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 |
Mitochondrial density | High | High | Medium | Low |
Capillary density | High | Intermediate | Low | Low |
Oxidative capacity | High | High | Intermediate | Low |
Glycolytic capacity | Low | High | High | High |
Major storage fuel | Triglycerides | Creatine phosphate, glycogen | Creatine phosphate, glycogen | Creatine phosphate, glycogen |
Myosin heavy chain, human genes |
MYH7 | MYH2 | MYH1 | MYH4 |
Myotome
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.
Puberty
- 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
References
- ↑ <pubmed>20888930</pubmed>
- ↑ 2.0 2.1 <pubmed>18945372</pubmed>| PMC2596796 | BMC Syst Biol.
Reviews
Articles
Search PubMed
June 2010 " Skeletal Muscle Development" All (19316) Review (2515) Free Full Text (5587) Manage Filters Search Pubmed: Skeletal Muscle Development
Additional Images
Terms
External Links
Glossary Links
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2024, May 19) Embryology Musculoskeletal System - Muscle Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Musculoskeletal_System_-_Muscle_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G