Exercise Science 3

Musculoskeletal System: Bones and Joints

Chapter 3: Overview

• Instructor: Nicole Mendola, MS, RCEP, C-EP, EIM III, GEI

Course Objectives

• Define universally accepted reference positions.
• Review planes of motion.
• Discuss joint movement and anatomical terms.
• Review the structure of the skeletal system and joint structure.

Anatomical Position and Key Terms

Anatomical Position

• Reference point for anatomical terms: body standing upright, facing forward, arms at side, palms facing forward.

Key Anatomical Directions

• Superior: Toward the head.
• Inferior: Away from the head.
• Medial: Toward the midline of the body.
• Lateral: Away from the midline of the body.
• Proximal: Closer to any reference point (often used for limbs).
• Distal: Farther from any reference point.

Planes of Motion

Definitions of Planes

• Mid-sagittal Plane: Divides the body into left and right halves.
• Sagittal Plane: Runs front to back (flexion and extension movement).
• Frontal (Coronal) Plane: Divides the body into anterior and posterior parts (abduction and adduction movement).
• Transverse (Horizontal) Plane: Divides the body into upper and lower parts (rotation).

Joint Movement

• Joint movements are described by their spatial movement patterns in relation to the anatomical position.

Anatomical/Directional Terms

Musculoskeletal Anatomy

• Interaction of bones, joints, and muscles determines:
  • Range of Motion (ROM) of joints.
  • Specific movements allowed.
  • Force produced during movements.

Skeletal System

Components of the Skeletal System

• Comprises cartilage, periosteum, and bone (osseous) tissue.

Functions of the Skeletal System

• Supports soft tissue.
• Protects internal organs.
• Acts as a source of nutrients and blood constituents.
• Serves as rigid levers for movement.

Structure of the Skeletal System

• Total Bones: 206 bones in the human body.
• Voluntary Movement: 177 bones engage in voluntary movement.
• Axial Skeleton: Includes the skull, hyoid bone, vertebral column, sternum, and ribs.
• Appendicular Skeleton: Comprises remaining bones.

Bone Structure Components

• Diaphysis: The shaft of a bone.
• Medullary Cavity: The central cavity for bone marrow storage.
• Endosteum: Tissue lining the medullary cavity; contains cells for bone development.
• Epiphysis: The ends of the bone, covered by articular cartilage.
• Metaphysis: Region where the diaphysis meets the epiphysis; consists of mature bone.

Bone Covering

• Periosteum: The outer layer covering the bones.
  • Composed of two layers.
  • Processes: Serves as attachment points for ligaments and tendons; critical for bone growth, repair, and nutrition.

Types of Bone

• Compact Bone: Contains few spaces, forms the outer layer of all bones, and comprises a large part of the diaphysis of long bones.
• Spongy Bone: Less dense; consists of a three-dimensional lattice (trabeculae) with open spaces that provide strength against normal stresses.

Bone Shapes

• Long Bones: Examples include the femur, humerus, ulna, radius.
• Short Bones: Examples include carpals and tarsals.
• Flat Bones: Examples include the sternum, scapulae, ribs, pelvis.
• Irregular Bones: Examples include vertebrae, sacrum, coccyx.
• Sesamoid Bones: Example includes patella.

Articular System

Components of the Articular System

• Composed of bones, joints, and ligaments.

Joints

• Definition: Articulations between bones.

Ligaments

• Definition: Tough fibrous connective tissues that anchor bone to bone.

Types of Joints

Joint Classification

• Synarthrodial Joints: Immovable joints.
• Amphiarthrodial Joints: Slightly movable joints.
• Diarthrodial (Synovial) Joints: Freely movable joints.

Characteristics of Synovial Joints

• Five distinct features:
  1. Fibrous joint capsule enclosing the joint cavity.
  2. Joint cavity lined with synovial membrane.
  3. Synovial fluid occupies the joint cavity.
  4. Articulating surfaces of bones covered by hyaline cartilage.
  5. Function: Helps absorb shock and reduce friction during movement.

Joint Motions

Types of Joint Movements

• Rolling: Movement during joint actions.
• Sliding: Movement seen in joints during particular actions.
• Spinning: Rotational movement at joints.

Open and Closed Chain Movements

• Open Chain: When the distal segment of a joint moves through space.
  • Example: Leg extension performed on a machine.
• Closed Chain: When the distal segment of a joint is fixed in space.
  • Example: Standing barbell squat, where the squat motion occurs with the legs fixed.

Range of Motion (ROM)

• Defined as the degree of movement possible within a joint.
  • Types: Active, Passive, Hypermobile, Hypomobile.
• Movement at one joint may impact other joints.

Joint Stability

• Definition of Joint Stability: Resistance of a joint to displacement.
• Not all joints exhibit the same level of stability.
• Increased range of motion (ROM) may come at the expense of stability.

Factors Contributing to Joint Stability

• Ligaments: Assist in checking normal movement and resisting excessive movement.
• Muscles and Tendons: Span joints and enhance stability.
• Atmospheric Pressure: Generates a force outside the joint that can offer stability.
• Suction: Important for maintaining joint integrity and stability.
• Bony Structures: Contribute to the overall stability of joints.