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Visceral Skeleton Start of Muscular Visceral Skeleton • Spanchnocranium – Develops within the pharyngeal arches – Fishes – • jaw skeleton • Gill arches Fig. 7.3 • Squalus Cartilages of the Pharyngeal arches Palatoquadrate (I) Meckel’s cartilage (I) Ceratohyal (II) 1st Basibranchial 2nd Basibranchial III IV V VI VII • Overheads – Mandibles – Skeletal derivatives of pharyngeal arches Muscle stuff for Lab today Few general notes on muscle… • Terminology – Sarco- “flesh”; myo- “muscle” – Sarcolemma – cell membrane – Sarcoplasm – cell cytoplasm – Sarcoplasmic Reticulum – Smooth ER of cell – Sarcosomes – mitochondria of cell – Muscle fibers – muscle cell • Cell morphology – elongated, may be multinucleated • Full of contractile proteins (ex. actin, myosin) • 3 types – skeletal, cardiac, smooth • All derived from embryological mesoderm 3 Types of Muscle • Striated – Alternating light and dark bands – Two types 1. Skeletal 2. Cardiac – Most of the voluntary muscle in body 3. Smooth – not striated – Located in walls of blood vessels and viscera Muscle type Smooth Cardiac Skeletal # nuclei 1 1-2 Many Position of nucleus Central Central Periphery Striations No Yes Yes Shape Spindle Short, branched Long, cylindrical Size (diam) 5-10μm 10-15μm 30-150 μm Function Peristalsis Pumping Movement/ stabilization - Involuntary Involuntary Voluntary Fig. 10.1 Skeletal muscle morphology • Size – 30-150 μm diam. – Hypertrophied muscle > 100 μm – Strength of fiber proportional to diam. – Strength of muscle: • Number of fibers • Thickness of component fibers • Muscle consists of: – Muscle fibers – CT (non-cellular fibers) • Tendons – muscle to bone • Aponeuroses – muscle to muscle • General Appearance – Pink – red • Due to rich vascular supply and the presence of myoglobin pigments – Characterization • Red, White, Intermediate Muscle fiber “types” Characteristics Red White Vascularization Rich Poorer Innervation Smaller nerve fibers Larger nerve fibers Fiber diameter Thinner Thicker Contraction Slow, repetitive, not easily fatigued, weaker Fast, “burst”, easily fatigued, stronger contraction Mitochondria Numerous Few • Muscle tissue crosssection in child • ATPase Stain – dark • “white” muscle – dark • “red” muscle - lighter nuclei Investments of skeletal muscle • Purpose – conserve energy • Epimysium – around entire muscle – Dense irregular collagenous connective tissue – Continuous with tendon • Perimysium – surrounds fascicles of muscle fibers (fascicle = bundle) – Less collagenous – Derived from epimysium • Endomysium – surrounds each muscle fiber – Reticular fibers – External lamina (basal lamina)
