2. NORMAL ANATOMY
• Normal muscle is composed of number of
fasicles which are bound by epiphysium
and each fascicle is composed of muscle
fibres and wrapped by collagen called as
perimysium.The arterioles,nerve bundles
venules and muscle fibres are located in
the perimysium.
• In children,the muscle fibres are rounded
• In adult,the fibres are polygonal opposed to
each other with very little intervening
stroma
• Myocytes are synctial and nuclei are seen
subsarcolemmaly
3. • Each myofiber is a multinucleate syncytium formed by
fusion of precursor skeletal muscle cells termed myoblasts.
• Sarcoplasm is composed of myofibrils arranged in
sarcomeres,which are the contractile units of the cell
• It has alpha actinin,actin and myosin
• The sarcoplasm between the myofibrils is called intermyofibrillar
network and contain mitochondria,lipid,glycogen,t-tubules and
sarcoplasmic reticulum
4. MUSCLE CONTRACTION
• The electrical signals conducted by the T-tubules stimulate the
sarcoplasmic reticulum to release calcium.
• This calcium then binds to troponin, one of the proteins associated
with the thin actin filaments; through a series of a few steps, this
results in the binding of the thick filaments to the thin filaments.
• The binding of the myosin head to the actin filaments, together with
the concomitant hydrolysis of ATP for energy, results in the
contraction of the sarcomeres that in turn causes contraction of the
entire muscle.
6. Muscle biposy
• A muscle biopsy is the removal of a small piece of muscle
tissue for examination.
There are 2 types of muscle biopsy:
•A needle biopsy involves inserting a needle into the
muscle. When the needle is removed, a small piece of
tissue remains in the needle. More than one needle
stick may be needed to get a large enough sample.
•An open biopsy involves making a small cut in the
skin and into the muscle. The muscle tissue is then
removed.
8. Indications of muscle biopsy
General conditions
•Weakness of uncertain cause-generalised,proximal,floppy baby
syndrome
•Muscle pain,cramps,stiffness
•Persistently elevated muscle enzymes
Specific reasons
•Hereditary muscle disease in other family members
•Carrier detection
9. • Systemic connective tissue disease and vasculitis
• Certain metabolic diseases such as storage disease
• Suspicion of steroid myopathy in treated myositis
• Exclude drug induced myopathy
• Conflicting clinical,EMG or lab findings
• Confirm/reinforce clinical diagnosis
11. SITE OF MUSCLE BIOPSY
• Muscle with moderate disease
• Muscle belly not from tendon
• Proximal myopathies/generalised ststemic diseases-vastus lateralis
• Other sites-biceps,gastronemius
• EMG is used to select pathological muscle site
12. 2/23/2024
NORMAL MUSCLE:
The centre of this area of a
cryostat H&E cross-section of
muscle is largely occupied by the
majority of a single fascicle.
high power view shows
• peripheral nuclei
• endomysial connective tissue
13. 2/23/2024
NADH
NORMAL MUSCLE
• type 1 myofibres stain more darkly
than type 2 myofibres.
• high power reveals a punctate
distribution of stain throughout the
cell due to the mitochondria in
intermyofibrillar network
15. 2/23/2024
MYOSIN HEAVY CHAIN IH STAIN
NORMAL MUSCLE
in slow type
• type 1 are brown and type 2 are
pink
in fast type
• type 1 are pink and type 2 are
brown
