Synovial Joints Classification

Joints and Movement

• Synovial joints are classified into categories based on their structure and allowed movements.
• Hinge joints have a cylindrical projection of one bone fitting into a trough-shaped surface on another bone, allowing single plane movement in two directions (flexion and extension).
• Examples of hinge joints include elbow and knee joints, which allow for free movement.
• Ball and socket joints have a spherical or hemispherical head of one bone articulating with a cuplike socket of another bone, allowing multiple plane movement in several directions.
• Examples of ball and socket joints include shoulder and hip joints, which allow for free movement and enable lifting heavy loads.

Arthritis and Gout

• Arthritis is characterized by inflammation of joints, degeneration, and damage to joint tissue.
• Typical symptoms of arthritis include pain after walking, creaking sounds in joints, difficulty in getting up from a chair, and pain on walking up or down stairs.
• Rheumatoid arthritis is an auto-immune disorder that causes inflammation of the synovial membrane due to a faulty immune system.
• Osteoarthritis is a progressive disease that causes articular cartilages to soften and disintegrate, affecting knee, hip, and intervertebral joints.
• Gouty arthritis results from a metabolic disorder that causes an abnormal amount of uric acid to be retained in the blood, leading to the deposition of sodium urate crystals in joints, mainly affecting the big toe.

Types of Muscles

• Muscles are specialized tissues that can undergo contraction and relaxation, providing movements to body parts or the whole body.
• The study of muscles is called myology.
• Muscles have the ability to transform ATP into mechanical energy, enabling them to exert force.
• Smooth muscles are the earliest forms of muscles to evolve and are present throughout the animal kingdom.
• Cardiac muscles and skeletal muscles are found only in vertebrates.
• Cardiac muscles have intercalated discs and function to hold body parts in postural positions, move body fluids, and produce heat.

Characteristics of Muscles

• Smooth muscles are unstriped/non-striated, have irregular stripes, and are spindle or cylindrical in shape, with one nucleus per cell, and contract slowly.
• Cardiac muscles are striated, branched, and have one nucleus per cell, with slow to rapid contraction speed.
• Skeletal muscles are regularly striated, spindle in shape, and have many nuclei per cell, with an intermediate contraction speed.

Structure of Skeletal Muscles

• Skeletal muscles are surrounded by a connective tissue sheath called epimysium.
• The sarcoplasm of skeletal muscles is filled with myofibrils, which are the contractile machinery of the muscle.
• The external connective tissue surrounds and holds muscle fibers together.
• The sarcolemma is a part of the internal structure of skeletal muscles.
• Myofibrils are the internal contractile machinery of skeletal muscles.