Musculoskeletal System - Muscle Development

From Embryology
Revision as of 15:31, 22 September 2010 by S8600021 (talk | contribs)
Endochondral bone

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.

Musculoskeletal Links: Introduction | mesoderm | somitogenesis | limb | cartilage | bone | bone timeline | bone marrow | shoulder | pelvis | axial skeleton | skull | joint | skeletal muscle | muscle timeline | tendon | diaphragm | Lecture - Musculoskeletal | Lecture Movie | musculoskeletal abnormalities | limb abnormalities | developmental hip dysplasia | cartilage histology | bone histology | Skeletal Muscle Histology | Category:Musculoskeletal
Historic Embryology - Musculoskeletal  
1853 Bone | 1885 Sphenoid | 1902 - Pubo-femoral Region | Spinal Column and Back | Body Segmentation | Cranium | Body Wall, Ribs, and Sternum | Limbs | 1901 - Limbs | 1902 - Arm Development | 1906 Human Embryo Ossification | 1906 Lower limb Nerves and Muscle | 1907 - Muscular System | Skeleton and Limbs | 1908 Vertebra | 1908 Cervical Vertebra | 1909 Mandible | 1910 - Skeleton and Connective Tissues | Muscular System | Coelom and Diaphragm | 1913 Clavicle | 1920 Clavicle | 1921 - External body form | Connective tissues and skeletal | Muscular | Diaphragm | 1929 Rat Somite | 1932 Pelvis | 1940 Synovial Joints | 1943 Human Embryonic, Fetal and Circumnatal Skeleton | 1947 Joints | 1949 Cartilage and Bone | 1957 Chondrification Hands and Feet | 1968 Knee


--Mark Hill 02:30, 22 April 2010 (EST) Page Template only - content from original UNSW Embryology site currently being edited and updated.

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.


Somite cartoon3.pngSomite cartoon4.pngSomite cartoon5.png

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 (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


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, March 29) Embryology Musculoskeletal System - Muscle Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Musculoskeletal_System_-_Muscle_Development

What Links Here?
© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G