Muscle Histology Flashcards
What is the function of muscles?
Direct, integrated movement
Muscles are made up fo mycocytes, myofibrils and muscle fibres. What is a muscle fibre?
Muscle cell
NOT made of CT like normal fibres
What are the components of connective tissue found in muscles? What is the function of this CT?
Blood vessels
Nerves
Provide mechanical support
What are the 3 types of muscle and which are striated?
Skeletal - striated
Cardiac - striated
Smooth - non-striated
Skeletal muscle, what are the two types of fibre found and what contractions are associated with each?
Dark fibre -tonic contractions
Pale fibre - phasic contractions
What are the 3 layers of skeletal muscle? WHat does the innermost layer do?
Epimysium
Perimysium
Endomysium - electrical insulation
Contraction of each sarcomere is all or nothing, so how are contractions varied?
Number of fibres contracting
Skeletal muscles have a neuromuscular spindle. What is this? What does it do?
Modified muscle fibre
Sends sensory information about muscle tension to the CNS
What are motor end plates? Which neurotransmitter is released here?
Folds in sarcolemma at the post synaptic membrane
Acetylcholine
Which cells are responsible for myogenesis?
Mesenchymal cells and myoblasts
During myogenesis, myoblasts fuse to form what?
Myocytes and satellite cells
What are satellite cells?
Bipotent muscle stem cells
What is atrophy? What could this be due to?
Loss of myofibrils and nuclei
Interrupted nerve supply
What cells are responsible for regeneration of skeletal muscle?
Satellite cells
Which muscle layer is the holding base for sutures?
Epimysium
What are terminal cisternae?
Enlarged areas of sarcoplasmic reticulum
Surrounding T-tubules
Where is cardiac muscle found?
Heart
Large vessels near the heart
Describe the nuclei and and endomysium of cardiac muscle
Centrally placed nuclei
Abundant endomysium containing blood vessels
Are there visible striations in cardiac muscle? How are fibres arranged?
Yes
Loose arrangement of fibres
What are intercalated discs?
Junctions between cardiomyocytes which allow synchronised cardiac muscle contraction
(Rapid spread of wave)
Which feature is missing from cardiac muscle which is found in the 2 other muscle types?
Terminal cisternae
Describe the presence of mitochondria in the different types of muscles
Smooth - least
Skeletal - more
Cardiac - most
Is cardiac myogenesis possible?
No - lost soon after birth
How are cardiac muscle fibres repaired?
Cannot regenerate cells after birth
Repair by increasing connective tissue
What are purkinje fibres? Where are they found? WHat do they do?
Specialised cardiac muscle
Carry electrical impulse from left and right bundle branch
How do purkinje fibres stain? Why?
Pale staining
High glycogen levels
Which species have more prominent Purkinje fibres in the heart?
Sheep
Dogs
Where is smooth muscle found?
All organs
Tunica media
Describe the shape of smooth muscle cells and their nuclei
Spindle shaped cells
Central nuclei - only 10% visible in transverse section
Do smooth muscle cells have striations? Do they have connective tissue present within fibres?
No striations
yes - CT within fibres
Smooth muscles have no striations. They also have no…. and few…
No T-tubules
Few sarcoplasmic reticulum
What are pericytes?
Undifferentiated muscle cells
What is the name of the huge multi nuclear engined cells that can be several centimetres in length?
Syncytium
What are striations comprised of?
Ends of sarcomeres arranged in parallel rows
Which is the thin filament found here? Which is the thick?
Thin- actin
Thick - myosin
Why do skeletal muscles have multiple nuclei?
They are made up of fused myoblasts
