What are the functions of the joints? What are the joints

The major joints of the human body have flexion activities and simple rotational activities, and the functional positions of the joints are basically the flexion positions of the joints.

In the major joints, the position of the joint is not described by the functional position, such as the functional position of the hand is the wrist cocked by about 30°. The whole finger is close to the thumb, which is called the functional position of the hand function, because the hand is a function of the palm, and some functional positions are to facilitate the patient to apply a plaster cast and reduce the damage of the hand function. Under normal circumstances, large joints are not described by functional positions, and the most common joints are the joints of the hands and wrists.

The place where the bones are connected is called a joint, and the place where it can move is called a "moving joint", and the place where it cannot move is called a "moving joint". The joints mentioned here refer to the moving joints, such as the shoulders, elbows, fingers, hips, knees and other joints of the limbs. Joints are made up of joint capsules, articular surfaces, and articular cavities.

The joint capsule is surrounded by the outside of the joint, the smooth bone in the joint is called the articular surface, and the cavity part in the joint is the joint cavity. Normally, there is a small amount of fluid in the joint cavity to reduce friction during joint movement. When the joint is diseased, it can increase the fluid in the joint cavity, resulting in joint effusion and swelling.

There are many muscles attached around the joint, and when the muscles are contracted, they can be used for extension, flexion, abduction, adduction, and circumference.

Anatomically speaking, joints are divided into four categories, 1, condylar joints 2, sliding joints 3, pivot joints 4, and saddle joints.

The basic structure of the joint.

Although the joints of the human body are diverse, their basic structure is no less than the joint surface, joint capsule, and joint cavity.

1. Articular surface: The smooth surface where each bone touches each other is called the articular surface. The articular surface is covered by a layer of cartilage called articular cartilage.

2. Joint capsule: It is composed of connective tissue, which attaches to the bone surface around the articular surface. It can be divided into two layers, the outer layer is the fiber layer, which is composed of dense connective tissue; The inner layer is the synovial layer, which is composed of a thin layer of loose connective tissue, which secretes synovial fluid and plays a lubricating role.

3. Joint cavity: It is the closed space between the articular cartilage and the joint capsule.

4. Articular cartilage: reduce friction between bones.

5. Joint head: Closely linked with the joint socket for exercise.

6. Joint socket: Tightly connect with the joint head and carry out exercise. Basic lesions of the joints.

Under the traction of the muscles, the joints can be used for various movements. The forms of movement are: flexion is a decrease in the angle between the two connected bones, and extension is an increase in the angle; Adduction is the approach of the limb to the median sagittal plane, and abduction is to leave the median sagittal plane; Rotation is the rotation of the bone around the longitudinal axis (vertical axis) of itself, for example, the front of the limb turns to the inside is supinated, and the front of the limb turns to the outside is supinated; The compound movement of flexion, extension, adduction, and abduction is circumferential, when the proximal end of the bone rotates in situ, and the distal end moves in a circular motion, and the whole bone movement surface is conical.

The connection between bones is called a bone junction. Bone connections are further divided into direct connections and indirect connections, and joints are a form of indirect connection. A joint is made up of two or more bones, and the basic structure is the joint surface, joint capsule, and joint cavity (see figure).

The articular surface is the contact surface of the two adjacent bones that make up the joint, one convex and the other concave, and the surface is covered with a layer of articular cartilage, which has the effect of reducing friction and cushioning impact. The joint capsule is a connective tissue capsule attached to the bone surface around and near the articular surface, and the closed cavity enclosed by the joint capsule is called the joint cavity, and there is a small amount of synovial fluid in it. In addition to these basic structures, some joints also have auxiliary structures such as ligaments, intra-articular cartilage, glenoid margins, and synovial sacs.

The various structures of the joints make the joints both strong, stable, and flexible. Joints can do several forms of exercise, such as flexion and extension, adduction and abduction, and rotation. According to the number of joint motion axes and the shape of the joint surface, joints can be divided into various types, such as uniaxial joints, biaxial joints, and multiaxial joints.

2. Intensive lecture on the basics of arthritology in the open course of medical examination - the auxiliary structure of joints.

Articular surfaces, articular cavities, articular capsules.

People's every move is inseparable from joints, and the main function of joints is movement. They have a variety of forms of movement, and there are great differences in their range of motion. The normal range of motion of each joint is affected by age, gender, fat and thinness, and exercise, and the general rule is that young, female, thin, and regular exercisers have a larger range of motion for their joints; Elderly, male, obese, and inactive people have a smaller range of motion for their joints.

The movement forms of joints are basically divided into 3 groups: flexion and extension, adduction (the joint is close to the midline of the body) and abduction (the joint is away from the midline of the body), internal rotation and external rotation. For example, the elbow joint of the upper limb can act and stretch a group of movements, and the wrist joint can do two sets of actions of flexion and extension, adduction and abduction; The shoulder joint can perform three sets of movements: flexion and extension, adduction and abduction, internal rotation and external rotation.

Joints need to move and also need to be stable, and this pair of contradictions is perfectly unified through the special structure of joints. The cartilage that makes up the joint, the synovial layer of the joint capsule, the joint cavity and the synovial fluid in the cavity all favor joint mobility; The fibrous layer of the joint capsule, the ligaments inside and outside the joint, and the muscle tension around the joint all contribute to the stability of the joint. From a functional point of view, the mobility of joints with good stability is limited to a certain extent; The stability of joints with high mobility is affected to a certain extent.

For example, the main function of the spine is to support body weight and protect the spinal cord, therefore, the stability of the spinal joints is large and the mobility is small; The main function of the upper limb is mobility, therefore, the mobility of the joints of the upper limb is large and the stability is small.

There are many joints in the human body, and the joints in different positions play different functions, of course, most of them play a role in helping the human body bend and walk.

Joints act as fulcrums in movement.

Flexion and extension, adduction, and abduction.