Earth Science: Anatomy – Joints, Muscles, and Tendons
Coordinated movements are made possible by joints and flexible tendons connecting the rigid skeletal bones of the musculoskeletal system. Muscles are essential for the movement of limbs as well as organ functions.
Joints are a flexible connection between two bones. Normally, the end of a bone fits like a ball into the bowl-shaped depression of another bone or socket. Both joint surfaces are lined with soft and elastic cartilage that provides cushioning for the joint. The joint is surrounded by a capsule of connective tissue.
The articular capsule forms a closed joint cavity filled with a viscous joint liquid called synovial fluid, which serves as lubricant. There are different types of joints characterized by their shape and direction of movement. These are mainly hinge joints like the elbow, ball and socket joints like the hip, and saddle type joints like the basal thumb joint.
Muscles and tendons
Muscles produce power for active movements by contracting. They are also responsible for maintaining body tension for an upright position, for example, while sitting or standing. Language would not be possible without muscles and even a smile requires more than 200 small muscles.
Each muscle is made up of numerous bundles of individual muscle fibers embedded into the connective tissue. Striated muscle such as skeletal muscle or cardiac muscle is characterized by a high degree of alignment of contractile fibers. This muscle type is able to contract and expand much more rapidly and with greater force compared to smooth muscles (responsible for functions such as intestinal action or blood vessel tension), which are slower and show little fatigue.
In contrast to skeletal muscle, which can be controlled by will, this muscle type cannot be influenced voluntarily as it is regulated by hormones rather than direct nervous impulses. Tendons are firm and tight bundles of connective tissue (collagen or elastin fibers) that connect parts of the skeleton, provide elasticity, and transmit muscle force onto the skeletal bones.
Tendons, despite their resistance to pulling force, are prone to painful sports injuries; they cannot endure gravitational forces or pressure for an extended period of time. Sudden muscle contractions or extreme loads may result in a full rupture of the tendon.
PROSTHESES
Sometimes people lose limbs in serious accidents. Joints may be damaged through overuse so that they need to be replaced. In these cases, replica body parts are implanted into the body or attached externally as replacements (prostheses).
The most obvious are artificial limbs: prostheses of arms or legs. Today, arm and leg prostheses have been developed that are controlled by micro- processors and allow complex movements and even sport
BASICS
A BONE FRACTURE requires immediate medical attention The bone is straightened and fixed into position using plaster or traction bandages Fractured bones take weeks to heal, sometimes up to a year.