MDCAT Support & Movement 2026

Skeletal System

• Axial: skull, vertebral column, ribcage. Appendicular: limbs + girdles.
• 206 bones in adult human; 270+ at birth (some fuse).
• Joints: synovial (movable), fibrous (immovable, e.g., skull), cartilaginous (slightly movable).

Muscle Types

• Skeletal — voluntary, striated, multinucleate.
• Cardiac — involuntary, striated, single nucleus, intercalated discs.
• Smooth — involuntary, non-striated, single nucleus.

Sliding Filament Theory

Actin and myosin slide past each other; ATP-powered cross-bridge cycle. Sarcomere shortens; Z-discs move closer.