Skeletal Muscle Histology

From Embryology

Introduction

Skeletal muscle sarcomeres
Skeletal muscle structure cartoon

This page describes skeletal muscle histology which can identify cross-striational structure and /or properties related to contractile speed and fatigue.

Development of skeletal muscle, cardiac muscle and smooth muscle can be found in other notes.

Development of skeletal muscle from mesoderm occurs by mononucleated myoblasts fusing together to form mutinucleated myotubes that express contractile proteins forming sarcomeres within myofibers.

The regular organisation of filament structures within the sarcomeres gives skeletal muscle, and cardiac muscle, the striated appearance.


Histology Links: Skeletal Muscle | Cardiac Muscle | Smooth Muscle


Musculoskeletal Links: Introduction | Mesoderm | Somitogenesis | Limb | Cartilage | Bone | Bone Timeline | Axial Skeleton | Skull | Joint | Muscle | Muscle Timeline | Tendon | Diaphragm | Lecture - Musculoskeletal Development | Lecture Movie | Abnormalities | Limb Abnormalities | Cartilage Histology | Bone Histology | Skeletal Muscle Histology | Category:Musculoskeletal
Historic Musculoskeletal Embryology  
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 | 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 | 1949 Cartilage and Bone | 1957 Chondrification Hands and Feet


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

Skeletal Muscle Stages

3D virtual muscle model[1]
3D virtual muscle model[1]

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 Contraction

Skeletal, cardiac and smooth muscle all contract using the same mechanism: actin thin filaments being drawn together by myosin thick filaments.

  • In skeletal and cardiac muscle these thick and thin filaments are organised' in series into sarcomeres along the length of the muscle cell. This regular organization gives the muscle cells a striated appearance.
  • In smooth muscle these thick and thin filaments are not organised' into sarcomeres but are spread throughout the cell cytoplasm.

This animation shows the molecular interactions that occur within the skeletal muscle sarcomere between actin and myosin during skeletal muscle contraction. This irregular organization gives the muscle a non-striated appearance. This animation shows the molecular interactions that occur within the skeletal muscle sarcomere between actin and myosin during skeletal muscle contraction. This irregular organization gives the muscle a non-striated appearance.

Legend

  • Moving blob and stick - myosin complex.
  • Moving blob and stick - myosin complex with ATPase activation.
  • Ball binding myosin and splitting - ATP losing a phosphate to form ADP.
  • Twisted string of beads - actin helix.
  • Blue string - tropomyosin.
  • Beads stacked on large bead on blue string - troponin.
  • Small ball binding troponin - Calcium ion (Ca2+).
  • Grey pyramid - Magnesiun ion (Mg2+).
Actin myosin crossbridge 3D animation.gif

Muscle Fibre Types

Muscle fiber 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.

Histology Images

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 Micrographs

Electron Microscopy Virtual Slides

Skeletal Muscle EM1

SkeletalMuscleEM01-icon.jpg

 ‎‎Mobile | Desktop | Original

Skeletal Muscle | EM Slides
Skeletal Muscle EM2

SkeletalMuscleEM02-icon.jpg

 ‎‎Mobile | Desktop | Original

Skeletal Muscle | EM Slides
Skeletal Muscle EM3

SkeletalMuscleEM03-icon.jpg

 ‎‎Mobile | Desktop | Original

Skeletal Muscle | EM Slides
Skeletal Muscle EM4

SkeletalMuscleEM04-icon.jpg

 ‎‎Mobile | Desktop | Original

Skeletal Muscle | EM Slides
Skeletal Muscle EM5

SkeletalMuscleEM05-icon.jpg

 ‎‎Mobile | Desktop | Original

Skeletal Muscle | EM Slides

References

  1. 1.0 1.1 Ashley J Waardenberg, Antonio Reverter, Christine A Wells, Brian P Dalrymple Using a 3D virtual muscle model to link gene expression changes during myogenesis to protein spatial location in muscle. BMC Syst Biol: 2008, 2;88 PubMed 18945372 | PMC2596796 | BMC Syst Biol.

Search PubMed

June 2010 " Skeletal Muscle Development" All (19316) Review (2515) Free Full Text (5587) Manage Filters Search Pubmed: Skeletal Muscle Development

Terms

Skeletal muscle sarcomeres
  • A-band - (anisotropic band, Greek, anisos = unequal + tropos = turning) meaning having not equal properties in every direction,transverse bands in living skeletal muscle which rotate the plane of polarised light.
  • H-band - (Hell-band, German, hell = light + band; also Henle's band) light band within A-band of the myofibril.
  • I-band - (isotropic band, Greek, isos = equal + tropos = a turning, direction) Meaning having equal properties in every direction, of transverse bands in skeletal muscle which do not rotate the plane of polarised light.
  • sarcolemma - (Greek, sarkos = flesh + lemma = rind, husk) The plasma membrane plus basement membrane of a single muscle cell.
  • sarcomere - (Greek, + meros = a part) The structural subunit of striated muscle, repeating unit (segment) of myofibril from one Z-disc to the next.
  • sarcoplasm - (Greek, + plasma = a thing formed) the cytoplasm of a muscle cell.
  • sarcoplasmic reticulum - the endoplasmic reticulum of a muscle cell.
  • Z-disc - (Z-band, Z-line, Zwischenscheibe German, Zwischenscheibe = a between-disc) dark disc in centre of I-band; end disc of a sarcomere; Dobbie's line; Krause's line.

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Cite this page: Hill, M.A. 2017 Embryology Skeletal Muscle Histology. Retrieved September 24, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/Skeletal_Muscle_Histology

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© Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G