What is the main structure of the joint, the basic structure and function of the joint

Main structures: articular surface, articular capsule, articular cavity.

Auxiliary structures: ligaments; articular discs, labials; Synovial sac, synovial folds.

The articular surface is the contact surface of two or more adjacent bones, one is slightly convex and is called the joint head, and the other is slightly concave and is called the joint fossa. The articular surface is covered with a smooth layer of cartilage that reduces friction during exercise, and the cartilage is elastic and also slows down vibrations and shocks during exercise.

The joint capsule is a tough connective tissue that holds two adjacent bones together. The outer layer of the joint capsule is a fibrous layer, and the inner layer is a synovial layer, which secretes synovial fluid and reduces friction during exercise. The joint cavity is a narrow space between the articular cartilage and the joint capsule, which normally contains only a small amount of synovial fluid.

The bundle of dense connective tissue (or membrane) between two adjacent bones or that supports internal organs is called a ligament. Because the ligaments are tough, they strengthen the stability of the bones and hold the internal organs in their normal positions, limiting their range of motion.

The main ligaments in the human body are the knee cruciate ligament, inguinal ligament, coraco-shoulder ligament, radial collateral ligament of the elbow joint, ulnar collateral ligament, etc. Some ligaments are remnants of embryonic organs, such as arterial ligaments, which are closed by the ductus arteriosus during fetal period, and round ligaments that are formed by atrophy of the umbilical vein.

The main structure of the joint includes three parts: the articular surface, the joint cavity and the joint capsule, which is the most basic structure of the synovial joint.

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

In general, a joint is made up of three parts.

1. Articular surface, each joint has at least two articular surfaces corresponding to each other, some articular surfaces are spherical at one end, called the joint head, and the corresponding end is concave type, called the joint capsule. The articular surface is very smooth, which facilitates the movement of the joint because there is a layer of smooth articular cartilage on the articular surface. Many arthritis often the destruction of articular cartilage, leading to joint pain and dysfunction.

2 joint capsule.

It is composed of an outer layer of tough fibrous connective tissue and an inner layer of synovial membrane, which connects the two ends of the joint and closes the joint to form a cavity that secretes synovial fluid to lubricate the joint and nourish the articular cartilage. In arthritis, synovial fluid secretion increases, resulting in joint effusion.

3 Joint cavities.

It is the space between the articular surface and the joint capsule, and the joint fluid is in the joint cavity.

The above three structures are important structures to maintain the normal movement of joints, and attention should be paid to protection.

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.

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.

Joints are an indirect connection between bones and play an important role in maintaining the body's activities. The basic structure of a joint includes the articular surface, joint capsule, joint cavity, and other accessory structures.

The articular surface is the surface of contact between bones, one side is more prominent, and the other side is relatively concave, forming a joint socket, which plays an important role in maintaining the stability of the joint. On the articular surface, it is covered with a smooth layer of cartilage tissue, which can reduce friction in the joint during exercise, and the cartilage tissue is elastic to relieve vibration or shock during exercise.

The joint capsule is a kind of connective tissue, which is a firm connection between the two adjacent bones, the joint capsule is divided into two layers, the outer layer is the fiber layer, which mainly plays a fixed role, and the inner layer is the synovial layer, which can secrete synovial fluid and play a role in reducing intra-articular friction during exercise.

The joint cavity is a cavity surrounded by articular cartilage and joint capsule, and normally contains a small amount of synovial fluid secreted by the synovial sac. In pathological conditions, the amount of fluid in the joint cavity increases, resulting in the formation of joint effusions.

The joint will also have other accessory structures, such as ligaments that can increase the stability of the joint; There may also be joint discs, meniscus, sesamoids, etc., which are more conducive to alleviating the impact of external forces on the joints during exercise, increasing the stability of the joints, reducing friction between joints, and protecting tendons.

Joints are relatively easy to be injured in the human body structure, and play an important role in the movement of the human body, so in daily life and work, we must carefully protect the joints.

1. The basic structure of the joint includes three parts: the articular surface, the joint cavity and the joint capsule, which is the most basic structure of the synovial joint.

2. Articular surface: that is, the adjacent surface that constitutes the bones of the joint, and the articular surface is covered with a thin layer of smooth cartilage. The shape of the cartilage is consistent with the balance shape of the bone articular surface, which has the ability to reduce friction during exercise; At the same time, the cartilage is elastic and can slow down the action of oscillation and impact during exercise.

Articular cartilage is hyaline cartilage with no perichondrium on its surface. Usually one bone forms a convex surface and forms a joint head, and one bone forms a concave surface and becomes a joint fossa.

3. Joint capsule: The joint capsule is a membranous capsule composed of unique fibrous tissue that crosses the joint and attaches it to the adjacent bone, sealing the joint cavity. The joint capsule is divided into two layers, the inner and the outer, the outer layer is a thick and tough fibrous layer, which is composed of dense connective tissue.

The thickened part of the fibrous layer, called the ligament, strengthens the connection between bones and prevents overmobility of the joints. The inner layer of the joint capsule is a thin and flexible synovial layer, composed of loose connective tissue with abundant blood vessels, containing parallel and intersecting dense fibrous tissues that are attached to each other, and migrate to the periphery of the articular cartilage, and have a strong bridge-type solid connection with the episteum. The synovium forms folds that surround the edge of the articular cartilage but does not cover the articular surface of the cartilage.

The synovial layer produces synovial fluid, which provides nutrients and lubricates.

4. Joint cavity: The potential sealing cavity surrounded by the joint capsule and the articular cartilage surface is called the joint cavity. The cavity contains a small amount of synovial fluid to keep the joint moist and smooth; The cavity is usually under negative pressure to enhance the stability of the joint.