Muscle tissue derived from the mesoderm
Definition of muscle
Cats of mm
Muscle cells can
Skeletal muscle
Crash course Muscles: Muscle cells
Definition of muscle
- Basic tissue specialised for contraction and transmission of impulses
Cats of mm
- 2 forms: either striated or not
- Striated: cardiac or skeletal
- Smooth is not striated: visceral or 'involuntary' , found in internal organs
- Sarcolemma: plasma membrane
- Saccroplasm: cytoplasm
- Sarcomplasmic reticulum: endoplasmic reticulum
- Muscle fibres: actin and myosin filaments, myosin thick actin thin
Muscle cells can
- Stretch beyond their length
- Expand and return to resting state
- Increasee in size with increased physiological need
- However specialisation has caused loss of other cellular abilityies, muscle tends to heal more like scarring because lack of stem cells to replace all the myocytes
Skeletal muscle
- Each fibre is individual cell, very long cells, up to 30 cm or more
- Individiual cells have multiple nuclei peripherally located, cardiac muscl has nuclei located centrally
- Non branching whereas cardiac is branching
- Myofibrils-sarcomeres, long muscle fibre has lots of sarcomeres
- Sarcomeres-> filaments-> myosin and actin
- Fibre intidigitation allows for contraction and expansion
- A band is dark band and I band is the white band which is split down the middle by the z line.
- I bands get smaller during contraction and H band
- Voluntary muscle
- Innervation is most
- Connective tissue at several levels
- Each muscle fibre is surrounded by endomysium (thin layer of connective tissue) a bundle of muscle fibres form fascicles surrounded by permysium, fascicles surrouned by epimysium, fascia may separate individual muscle and compartments-epimysium lies underneath fascia.
- Muscle fibres are shorter and joined together by special junctions calle dintercalated discs which allow for rapid transmission of impulses
- Striated, single oval nucleus (located centrally), branching, involuntary contraction (governed by SA node)
- Contains sarcomeres
- Surrounded by a bit of endomysiu but no perimysium but tissue layer surrounding otuside of heart called epicardium.
- Involuntary
- Fusiform cells, very elongated
- No obvious striations, contractile elements different to skeletal and cardiac muscle
- Each cell has a single oval nucleus located centrally within the fibre.
- Not branched
- Located in the contractile wlals of viscera, includes airways, GIT, UGT
- Both sympathetic and parasympathetic innervation, can respond to nerve signals, hormones and drugs etc.
- Lacks sarcomeres but does contain both actin and myosin filaments
- On inside of cell membrane attachment points that actin attaches to and that contacts myosin filaments
Crash course Muscles: Muscle cells