Histology of the muscle Flashcards
what are the 3 types of muscle
skeletal
cardiac
smooth
functions of the muscular system
locomotion
posture maintenance
muscle tone
heat generation
joint stability
vasoconstriction and vasodilation
peristalsis
cardiac motion and contractility
transverse Tubule
Well developed in skeletal and cardiac muscles to transport calcium (absent in smooth muscle)
intercalated disk
Specialized intercellular junction that is only present in cardiac muscle
control
Skeletal muscle is under voluntary control‚ smooth and cardiac muscles are under involuntary control
types of skeletal muscle
parallel
convergent
pennate
circular
label the image
types of connective tissue sheaths
epimysium
perimysium and fascicles
endomysium
epimysium
overcoat of dense irregular connective tissue that surrounds the whole muscle
perimysium and fascicles
within each skeletal muscle the fibers are grouped into fascicles that resemble bundles of sticks
surrounding each fascicle is a layer of dense irregular connective tissue perimysium
endomysium
sheath of connective tissue that surrounds each muscle fibre and is connective tissue in nature
what is in the image and from which view
cross section of skeletal muscle
what is in the image and from which view
cross section of skeletal muscle
skeletal muscle in cross section
hexagonal profile with individual cells moulded together
nucleic beneath cell membrane
fibrocollagenous septa contain blood vessels
what is in the image and from which view
skeletal muscle in a longitudinal view
skeletal muscle in longitudinal view
shows prominent cross striations
dark bands termed A bands and light are termed I bands
correspond to the arrangement of thick and thin filaments in myofibrils
nuclei appear as elongated structures beneath cell membrane, each fibre has many nuclei
what is a sarcomere
the region of myofibril between 2 successive Z discs
smallest contractile unit of a muscle fibre
what are the two different bands
dark and light
A and I
dark band
A bands
has lighter region in midsection called H zone
H zone
bisected vertical by dark line called M line
M for middle
light band
I band
has a midline interruption called Z disc or Z line
where are I bands found
thin filaments
where are H zones found
thick filaments only q
where is the M line found
thick filaments linked by accessory proteins
outer edge of the A bands
thick and thin filaments overlap
what is a motor endplate
specialised chemical synapses formed at the sites where the terminal branches of the axon of a motor neuron contact a target muscle cell.
action of the motor end plate
activation causes release of acetylcholine from storage granules by exocytosis
then diffuses across gap between axon and muscle fibre and interacts with specific membrane receptors to cause depolarisation of muscle fibre
initiates contraction
activity of secreted acetylcholine is curtailed by activity of acetylcholinesterase
bound to basement membrane
hydrolyses acetylcholine into acetic acid and choline
specialised motor axons innervate fibres in the muscle spindle
myasthenia graves
autoimmune disease
antibodies bind to acetylcholine receptors
prevent acetylcholine from interacting with receptors causing depolarisation
develop muscle weakness manifested by fatiguability, unable to lift arms
failure to maintain upright posture of head and drooping of eyelids
treatment is by administration of anticholinesterases
potentiates action of acetylcholine and allows it to bind to receptors not blocked by antibody
Duchenne muscular dystrophy
deficiency of dystrophin
genetic disorder
dystrophin encoded by gene on short arm of X chromosome Xp21
linked to cytoplasmic side of sarcolemma of muscle fibre
rapid progression of skeletal muscle degeneration
mainly young boys
muscle weakness and wasting
what is in the image
Duchenne muscular dystrophy
lack of dystrophin results in damage to skeletal muscle cell membrane with eventual death of muscle fibers
dead muscle cells replaced y fat cells
muscle fibres are of various diameters
what is in the image
longitudinal section of cardiac muscle cells
contain 1 or 2 nucleus
extensive eosinophilic cytoplasm
gives 3d appearance
elongated nuclei central located
what is in the image
transverse section of cardiac muscle
what is in the image
ID are intercalated disks
cross section under polarised light
what is in the amigo and what are the red lines
intercalated discs
longitudinal section of cardiac muscle
what is in the image
transverse section of cardiac muscle
what is in the image
longitudinal section of smooth muscle
can see serosa and elongated nuclei but there’s no striations
what is in the image
cross section of smooth muscle
skeletal muscle summary
Striations
Long cylindrical unbranched fibres
Multinucleated peripheral nuclei
No cell junctions
Highly developed sarcoplasmic reticulum with termina cisterns
Regeneration with satellite cells
cardiac muscle summary
Striations
Short branch anastomosing fibres
Uninucleated, central
Intercalated discs cell junctions
Small cisterns and less well developed sarcoplasmic reticulum
Not able to regenerate
smooth muscle summary
No striations
Short spindle shaped fibres
Uninucleated, central
Gap junctions and adherents junctions
Poorly developed sarcoplasmic reticulum
Regeneration by mitosis
what are satellite cells
are adult myogenic stem cells that repair damaged muscle. - produce myoblasts that can replace damaged fibers
- undergo self-reneweal
