Musculoskeletal System - Muscle Development: Difference between revisions
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--[[User:S8600021|Mark Hill]] 02:30, 22 April 2010 (EST) '''Page Template only''' - content from original [http://embryology.med.unsw.edu.au/ UNSW Embryology] site currently being edited and updated. | --[[User:S8600021|Mark Hill]] 02:30, 22 April 2010 (EST) '''Page Template only''' - content from original [http://embryology.med.unsw.edu.au/ UNSW Embryology] site currently being edited and updated. | ||
===Myogenesis=== | |||
* 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. | |||
* Skeletal muscle - cells originate from the paraxial mesoderm. 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. | |||
===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''' | |||
* 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. | |||
* The electrical properties of the motor neuron will regulate the contractile properties of all associated myofibres. | |||
'''MH-''' you do not need to know the table below in detail, it is provided for information purposes only. | |||
{|class="wikitable" | |||
|- | |||
!bgcolor="LightSteelBlue"|Fibre Type ||bgcolor="LightSteelBlue"|Type I fibres ||bgcolor="LightSteelBlue"|Type II a fibres ||bgcolor="LightSteelBlue"|Type II x fibres ||bgcolor="LightSteelBlue"|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, <br/>human genes || MYH7 || MYH2 ||MYH1 || MYH4 | |||
|} | |||
===Myotome=== | |||
This term is used to describe the region of the somite that contributes skeletal muscle to the embryo body. Each somite pair level gives rise to a group of skeletal muscles supplied by a specific segmental spinal nerve. The muscle arises from a specific somite and the spinal nerve arises from a specific level of the spinal cord (identified by vertebral 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. | |||
==Myotome== | ==Myotome== |
Revision as of 10:25, 12 June 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. (More? Cardiac or GIT Development)
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. (see OMIM entry). It needs to form a dimer to be active and is maintained in an inactive state by binding of Id (see OMIM entry).
System Links: Introduction | Cardiovascular | Coelomic Cavity | Endocrine | Gastrointestinal Tract | Genital | Head | Immune | Integumentary | Musculoskeletal | Neural | Neural Crest | Placenta | Renal | Respiratory | Sensory | Birth |
--Mark Hill 02:30, 22 April 2010 (EST) Page Template only - content from original UNSW Embryology site currently being edited and updated.
Myogenesis
- 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.
- Skeletal muscle - cells originate from the paraxial mesoderm. 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.
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
- 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.
- The electrical properties of the motor neuron will regulate the contractile properties of all associated myofibres.
MH- you do not need to know the table below in detail, it is provided for information purposes only.
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
This term is used to describe the region of the somite that contributes skeletal muscle to the embryo body. Each somite pair level gives rise to a group of skeletal muscles supplied by a specific segmental spinal nerve. The muscle arises from a specific somite and the spinal nerve arises from a specific level of the spinal cord (identified by vertebral 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.
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.
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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