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BASIC TISSUES - MUSCULAR TISSUE (Functions (Movement, Posture, Respiration…
BASIC TISSUES - MUSCULAR TISSUE
General
Specialised for contraction
Cells = myofibers or muscle fibers
Functions
Movement
Posture
Respiration - breathing muscles
Communication - verbal and facial
Constrictions of organs and vessels - peristalsis, vasoconstriction etc
Heart beat
Heat production - due to metabolism within cells
Characteristics
Contractility - shorten to cause movement
Extensibility - stretch to original length and more
Elasticity - sensitive to nerve impulses
Excitability - sensitive to nerve impulses
Skeletal muscle
General
Voluntary and striated (uniform arrangement of myofibrils)
40% body weight and over 400 in body
Attached to bones by tendons
Muscle fibre has multiple, peripheral nuclei
1 can be up to 10 cm and forms fusion of many 100s of precursor cells (myoblasts) so multinucleated
Adult muscle has precursor cells - divide to form new muscle cells after tissue damage
Functions
Produce skeletal movement
Postural support
Maintain body temp.
Store nutrient reserves
Structure
Refer to diagrams on slides
Sarcomere basic contractile unit of striated muscle
Cardiac muscle
General
Involuntary
Cells (cardiocytes) striated, branched and single (sometimes 2) nuclei
Myocardial cells interconnected to form continuous unit via intercalated discs (couple cells together mechanically - through desmosomes - and electrically - gap junctions)
Intermediate speed of contraction
Functions
Heart contraction - location is cardiac wall
Smooth muscle
General
Found as sheets or bundles in walls of guts, blood vessels etc
Cells spindle shaped and non striated (myofilament not uniformly arranged)
Cells are tapering and have 1 central nucleus
Involuntary - can be stimulated by nerves, hormones or contract spontaneously
Myosin and actin are contractile parts of continuous chains of tensile structures that stretch both across and between smooth muscle cells
Actin filaments of contractile units are attached to dense bodies
Dense bodies also attach intermediate filaments - appear to serve as anchors from which filaments can exert force
Caveoli - depressions of plasma membrane involved in fluid and electrolyte transport
Structure
Refer to diagrams on the slides
Function
Visceral and circulatory - slowest