Skeletal Muscle Types and Joint Movement Mechanics

Skeletal Muscle Characteristics and Function

• Muscle Types (Morphology): Monocephalic, two-headed, three-headed, tetracephalic, pennate, semipenniform, polygastric, dentate.

Muscle Contraction Mechanics

The muscle trabecula (likely referring to muscle fibers or structure) may be dynamic or static:

• Dynamic: Force exerted on the points of origin and insertion of bone; the length is unchanged. This includes:
  • Concentric: The distance between the origin and insertion shortens.
  • Eccentric: The opposite situation (lengthening under tension).
• Static: The muscle contracts without any movement occurring.

Major Upper Body Muscle Groups

• Trapezius: Spacers/stabilizers for arm muscles.
• Latissimus Dorsi (Dorsal width): Tilts arm muscles.
• Deltoid: Levator muscles of the arm.
• Biceps: Muscles for elbow flexion.
• Triceps: Muscles for elbow extension.
• Pectoralis: Approximators (adductors) of the arm.

Trunk and Lower Body Muscles

• Abdominals: Trunk and hip flexors.
• Gluteal-Lumbar (Buttock-Lumbar): Trunk and extensor muscles of the hip.
• Adductors: Muscles that approximate (bring toward the midline) the leg.
• Quadriceps: Knee extensor muscles.
• Biceps Femoris: Muscle for knee flexion.

Vertebral Column and Joint Mobility

Spinal Column Structure

The column consists of 7 cervical vertebrae, 12 thoracic, 5 lumbar, 5 fused vertebrae forming the sacrum, and 3 or 4 coccygeal vertebrae (coccyx).

Spinal Mobility

Movements include flexion, extension, rotation (abdominals involved), and lateral flexion (lumbar region).

Shoulder Mobility (Arm Movements)

• Protraction: Raising or projecting the arm forward.
• Retroversion: The opposite movement (pulling back).
• Abduction: Separation of the arm from the body.
• Adduction: Movement toward the body.
• Rotation: Internal and external rotation.

Hip Mobility

Movements include extension, flexion, alignment (likely referring to neutral position/adduction), separation (abduction), and external and internal rotation.

Elbow and Forearm Mobility

Flexion and extension occur at the elbow. Transverse motion involves pronation and supination (turning the radius over the ulna, with the hand moving passively).

Knee Joint Anatomy and Movement

Knee Structure

The skeleton of the leg is formed by the more robust tibia bone internally and the fibula externally. The knee joint involves the distal femur and the proximal tibia (tibial plateau), where the glenoid cavities are located. Between the two plateaus are the tibial menisci, which are crescent-shaped fibrocartilaginous rims. The joint capsule encloses the knee; anteriorly, it has an opening where the patella engages. It is reinforced laterally by the lateral and external collateral ligaments, and internally by the cruciate ligaments, as well as strong crossing tendons.

Knee Mobility

The knee has a single primary axis of motion, allowing for transverse flexion and extension. However, when flexed, small movements allow for internal and external rotation.