Bones and joints
Bone is the scaffold of human body. The human skeleton consists of 206 groups of bones with different sizes and shapes. These bone groups are constructed by the skeletal system, and a complete hard skeleton structure is constructed to maintain the body shape and support the weight.
Bones alone can't make the body move. The human body can move freely because of the joints between bones. Bones and joints are the main parts of the motion system, that is, components. When the tendons of bones move, bones play a lever role in the movement and joints play a pivotal role. Joints have a set of basic structures and characteristics, and have great range of motion and flexibility.
Basic structure of joint
The joints between bones are called joints, and the movable joints are called joints? Movable joints? , don't move the joints? Joint immobility? .
The joint consists of joint capsule, joint surface and joint cavity. The joint capsule surrounds the outside of the joint, the smooth bone in the joint is called the joint surface, and the joint cavity is the joint cavity.
Articular surface: The shiny surfaces where bones contact each other are called articular surfaces. The articular surface is covered by a layer of cartilage, and the achievement of this layer of cartilage is articular cartilage.
Joint capsule: composed of connective tissue groups, attached to the bone surface around the articular surface. It can be divided into inner layer and outer layer, and the outer layer is a fiber layer composed of dense connective tissue; The inner layer is synovial layer, which is composed of thin and loose connective tissue, which can secrete synovial fluid and play a role in lubrication.
Joint cavity: a sealed cavity between articular cartilage and articular capsule. It contains synovial fluid, which can reduce the friction between bones. Under normal circumstances, there is a small amount of liquid in the joint cavity to reduce the friction during joint movement. When the joint is sick, it may lead to the increase of fluid in the joint cavity, resulting in joint effusion and swelling.
Articular cartilage: the shape of articular cartilage is consistent with the shape of articular surface, which can reduce friction during exercise; At the same time, cartilage has elasticity, which can slow down the vibration and impact during exercise. Articular cartilage is hyaline cartilage with no perichondrium on its surface. Usually, the bony process forms the joint head and the bony depression forms the joint fossa.
Joint head and joint socket: Joint head and joint socket are closely connected and can move.
Popular science? Basic structure of bones and joints
Basic function of joint
In the above connection structure, each part plays an important role. Articular cartilage, synovial layer of joint capsule, joint cavity and synovial fluid in the cavity are all beneficial to joint activity; The fibrous layer of joint capsule, ligaments inside and outside the joint and muscle tension around the joint are all beneficial to enhance the stability of the joint.
Articular cartilage: reduce joint friction and cushion vibration.
Synovium of joints: Secrete synovial fluid, lubricate joints, produce anti-inflammatory products, such as hyaluronic acid, and maintain the stability of joint environment.
Joint synovial fluid: lubricate joints, penetrate into cartilage through joint movement, nourish and repair cartilage tissue. Bones: Support the weight and provide the foundation for the movement and stability of joints.
Ligament: through the traction of muscles, the position of joints is fixed and the function of joints is strengthened. Dense fibrous connective tissue bundles connected between two adjacent bones are called ligaments, which can strengthen the stability of joints. The external ligament located outside the joint capsule is called the external ligament of the joint capsule, which is partially attached to the joint capsule and is a local thickening of the joint capsule, such as the iliofemoral ligament of the hip joint; Some are not attached to the capsule and exist alone, such as the fibular collateral ligament of the knee joint. The intra-capsule motion area located in the joint capsule is wrapped by synovium, such as the cruciate ligament in the knee joint. There are abundant sensory nerves in ligaments and joint capsules, which are extremely painful after injury.
Popular science? Basic structure of bones and joints
There are many muscles attached around the joints. When muscles contract, they can stretch, bend, abduction, adduction and rotation. Functionally, the range of motion of joints with good stability is limited to some extent; The stability of highly active joints is affected to some extent. For example, the main function of the spine is to support the weight and protect the spinal cord, so the stability of the spinal joint is large and the activity is small; The main function of the upper limb is mobility, so the joint mobility of the upper limb is large but the stability is small.