PRACTICAL ROADMAP MUSCLE

WJ van der Spuy

MUSCLE

• Skeletal (striated) • Cardiac (striated) • Smooth

• Identification based on

– Fiber size, shape and presence/absence of branching – Number, shape and position of nuclei – Presence or absence of cross-striations

MUSCLE Skeletal Cardiac Smooth

Cell Elongated Branching Spindle-shaped

Nucleus Multiple peripheral Single or bi-nucleated central

Single central

Striations Cross-striated Cross-striated & Intercalated disks

None

Motor Control Voluntary Involuntary Involuntary

SKELETAL MUSCLE

• Slide 76 Striated Skeletal Muscle – Tongue – Iron haematoxylin stain

Organisation

Epimysium - surrounding muscle

Perimysium - surrounding fascicle

Endomysium - surrounding muscle fibre

Scanning Electron Micrograph – WJ van der Spuy – MSc

100µm

Muscle fibre

Fascicle

Fibre Orientation

Longitudinal section

Transverse section

Identification

Muscle fibre

Muscle fibre

Multiple peripheral nuclei

Cross-striations Fibroblast nuclei in connective tissue

sheath

Striations

A band (dark striation) bisected by light H band

I band (light striation) bisected by dark Z line

SKELETAL MUSCLE

• Slide 50 Musculo-tendinous junction – H&E stain

Musculo-tendinous Junction

Dense regular connective tissue Skeletal Muscle

Musculo-tendinous junction with fibres inserting obliquely into tendon

SKELETAL MUSCLE

• Slide 4 Neuromuscular (myoneural) junction – Snake – H&E and gold impregnation staining

Neuromuscular Junction

Axon Boutons (neuromuscular junction)

Motor Nerve (neuromuscular bundle in longitudinal section) Striated skeletal

muscle fibres

Neuromuscular bundle (transverse section)

Micrograph – WJ van der Spuy – MSc Stain: Toluidine blue pH=11.5

Blood vessel

Neuromuscular Junction

Axon boutons

Motor nerve

Muscular Dystrophy

• Limb-Girdle Muscular Dystrophy type 2B (LGMD2B)

• Increased rate of regeneration in response to ongoing degeneration of muscle

• Characterised by: – Variation in fiber size – Necrosis of muscle tissue – Revascularisation – Inflammatory cell infiltration – Phagocytosis of necrotic debris – Proliferation of mononuclear muscle precursors – Fusion of precursors to form myotubes

LGMD2B CN: Central nucleus Regenerating fibre

FS: Fibre splitting Early hyperplasia

FL: Fibre lobulation Late hyperplasia

LI: Leukocyte infiltration Inflammation

NF: Necrotic fibre Degenerating fibre

PI: Postnecrotic infiltrate Clearing debris after degeneration

SC: Satellite cell Mononuclear muscle precursor – regenerative ability

PN: Peripheral nucleus Mature fibre

Micrograph – WJ van der Spuy – MSc Stain: Toluidine blue pH=11.5

CN FL

PI

PN

FS

NF

SC 10µm

LI

CARDIAC MUSCLE

• Slide 57 Heart (interventricular septum) – Iron haematoxylin stain

Fibre Orientation

Longitudinal section Transverse section

Identification

Cross-striations

Fibre branching

Intercalated discs

Central nuclei

Interventricular Septum

Endocardium

Purkinje fibres

Myocardium with ordinary cardiac muscle fibres

Capillaries with black stained RBCs

Lumen of left ventricle

Purkinje Fibres

Pale-staining fibres

Large glycogen space around nuclei

Nucleus

Ordinary Cardiac Muscle Fibres

Dark-staining fibres

Smaller glycogen spaces around nuclei

Nucleus

CARDIAC MUSCLE

• Slide 86 Heart – H&E and elastic stain

Interventricular Septum

Endocardium

Purkinje fibres

Myocardium with ordinary cardiac muscle fibres

Interventricular Septum

Purkinje fibres Myocardium with ordinary

cardiac muscle fibres

Large glycogen space around nucleus

Nucleus

Small glycogen space around nucleus

Nucleus

SMOOTH MUSCLE

• Slide 10 Smooth muscle – Uterus (baboon) – H&E stain

Overview

Endometrium Myometrium with smooth muscle

Fibre Orientation

Longitudinal section

Transverse section

Identification

Cigar-shaped nucleus centrally located in spindle shaped fibre

Longitudinal section

Transverse section

Smooth Muscle vs. Connective Tissue

Blood vessel with smooth muscle wall

Irregular dense connective tissue

Myometrium with smooth muscle