Visceral Skeleton

Start of Muscular

Visceral Skeleton

• Spanchnocranium– Develops within the pharyngeal arches– Fishes –

• jaw skeleton• Gill arches

Fig. 7.3

• Squalus

1st Basibranchial

2nd Basibranchial

Palatoquadrate (I)

Meckel’s cartilage (I)

Ceratohyal (II)IIIIVVVIVII

Cartilages ofthe Pharyngealarches

• 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. Skeletal2. 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 cross-section 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)