Skeletal and Muscular Systems: Joints, Movements and Muscles
Skeletal System
- The skeletal system provides support, protection, movement, storage for minerals and lipids, blood cell production, and energy storage.
- The skeletal system is composed of bones, cartilage, ligaments and tendons.
- The human skeleton is typically made up of 206 bones which can be classified as either axial (80 bones) or appendicular (126 bones).
- Axial skeleton consists of the skull, vertebral column, ribs and sternum while the appendicular skeleton involves the limbs and pelvic girdle.
- Bones are either categorised as long, such as the femur, short, such as the carpals, flat, such as the scapula, or irregular, such as the vertebrae.
Joints
- A joint, also known as an articulation, refers to any point where two bones meet.
- Joints can provide varying degrees of movement and can be functionally classified as synarthroses (immovable), amphiarthroses (slightly movable), or diarthroses (freely movable).
- They can also be structurally categorised into fibrous (joined by dense connective tissue), cartilaginous (joined by cartilage), or synovial (not directly joined).
- Synovial joints are enclosed by a fibrous articular capsule lined with synovial membrane and contain synovial fluid to lubricate the joint. These include hinge, pivot, saddle, plane, condyloid, and ball and socket joints.
Movements at Joints
- Flexion and extension refer to decreases/increases in the angle between articulating bones, respectively.
- Abduction is the motion of a structure away from the midline while adduction refers to motion towards the centre of the body.
- Rotation can refer to the movement of a body part around its own axis. Rotation can be internal (toward the centre of the body) or external (away from the centre of the body).
- Circumduction is the movement of a body segment in a circle.
- Pronation and supination refer to rotations of the forearm, with pronation turning the hand to face downwards, while supination turns the hand to face upwards.
Muscular System
- The muscular system is responsible for producing movement, maintaining posture, stabilising joints, and generating heat.
- Muscles can be classified into three types: skeletal, cardiac, and smooth muscles.
- Skeletal muscles are voluntary muscles, which contract and relax to move bones, while cardiac muscles and smooth muscles are involuntary.
- Muscles work in pairs known as agonists and antagonists. The agonist is the primary muscle responsible for movement, while the antagonist opposes the agonist to provide balance.
- Basic components of a muscle include muscle fibres, myofibrils, actin and myosin filaments, sarcoplasmic reticulum, and sarcolemma. These are all critical in the process of muscular contraction.