Human Skeletal and Muscular System Anatomy Essentials

Human Skeletal System

The skeletal system is the framework of the human body, consisting of approximately 206 bones. It provides stiffness, flexibility, and elasticity.

Key Features

• Unique Bone: The hyoid bone (located in the neck) is the only bone that is not articulated.
• Bone Types:
  • Long: Femur, radius, ulna.
  • Flat: Skull bones, shoulder blades.
  • Short: Vertebrae, ear bones.

Bone Functions

• Support and protection of internal organs.
• Production of red blood cells.
• Enables movement by acting as levers for muscles.
• Storage of minerals.

Distribution of Bones

• Head: Skull (8), face (14), hyoid (1), ear (6).
• Vertebral Column: Cervical (7), thoracic (12), lumbar (5), sacrum (1), coccyx (1).
• Chest: Ribs (24), sternum (1), thoracic vertebrae.
• Upper Limbs: Girdle (4), arm (2), forearm (4), hand (54).
• Lower Limbs: Pelvic girdle (2), thigh (2), leg (6), foot (52).

Muscular System

Muscles are active organs responsible for movement, with approximately 600 muscles in the human body.

Muscle Classification

• Smooth: Involuntary contraction.
• Striated:
  • Skeletal: Voluntary contraction.
  • Cardiac: Involuntary contraction.

Types of Muscle Contraction

• Static (Isometric): No variation in muscle length.
• Dynamic (Isotonic):
  • Concentric: Muscle shortening.
  • Eccentric: Muscle lengthening.

Muscle Fiber Types

• Type 1 (Red): Slow-twitch fibers.
• Type 2 (White): Fast-twitch fibers.

Functional Classification

• Flexors: Flex and approximate.
• Extensors: Stretch.
• Adductors: Bring together.
• Abductors: Separate.
• Rotators: Rotate to either side.

Joints

Joints are the union of two or more bone or cartilage pieces.

Components

• Joint Surfaces: The ends of the bones.
• Hyaline Cartilage: Covers surfaces to protect against friction.
• Stabilizing Elements: Joint capsule, ligaments, and tendons.

Mobility Types

• No mobility, limited mobility, and mobile.

Growth Considerations

Bone growth in children is influenced by genetics, nutrition, hormones, and physical movement.