A: Histology of muscle Flashcards
Types of skeletal muscle connective tissue:
- Epimysium: surrounds entire muscle
- Perimysium: surrounds each fascicle
- Endomysium: surrounds each fibre/muscle cell.
Structure of skeletal muscle fibre
- Long unbranched cylindrical shape
- Multinucleated
- Nuclei positioned peripherally
- Striated
Thin (actin) filaments
From from Z disc to centre of sarcomere
Thick (myosin) filaments
In the centre of the sarcomere, contain ATPase enzymes.
A bands
Full length of thick filament (including parts of thin filament)
H zone
Centre part of A band, no thin filament.
M line
Centre of H zone
L band
Only thin filaments, lies within 2 adjacent sarcomeres.
T tubules
Runs around myofibrils in sarcolemma, makes sure all myofibrils contract simultaneously.
Sarcoplasmic reticulum
Interconnecting tubules surrounding each myofibril. Contains Ca2+
Nerve impulse direction in muscle
T-tubule –> release of Ca2+ from sarcoplasmic reticulum –> Ca2+ into cytoplasm –> contraction.
Sliding filament theory
- Thin filaments are pulled towards the centre of the sarcomere
- Sarcomere shortens
Smooth muscle cell structure
- Fibres are shorter than skeletal
- Spindle shaped
- Single nucleus in centre.
- No myofibrils or sarcomeres, so not striated
- Thin + thick filaments are scattered + attached to dense bodies throughout the sarcoplasm
- Have calveolae
Dense bodies
noncontractile intermediate filaments
Caveolae
Indentations in sarcolemma that act like T tubules.
Types of smooth muscle
Unitary/ tonic
Phasic
Unitary smooth muscle
- Cells arranged in sheets in hollow viscera
- Cells contract spontaneously (no need for nerves to contract)
- Have gap junctions which allow the spread of excitation and for ions to move between cells.
- Influenced by Autonomic nervous system
Cardiac muscle cell structure
- Long + cylindrical
- One central nucleus
- Branching cells
- Have intercalated discs: cells join end to end which facilitates spread of excitation along row of cells.
- Striated (have myofibrils with sarcomeres)
- T-tubules associated with single small cistern of SR
Identify
Cardiac
Identify
Cardiac cell
Identify
smooth muscle
Identify
Skeletal muscle
Identify
Intercalated discs
In which muscle types are intercalated discs absent?
Smooth + skeletal
