In the body of an adult, there are 206 bones, while in a newborn child their number reaches 350, then in the process of life they grow together. Most of them are paired, 33-34 remain unpaired. Bones are driven by muscles and tendons. Bones form the skeleton: the spine, upper and lower limbs, and the skull. In order to connect them together, there are various types of connection of bones.
Human Skeleton Functions
The main functions of the skeleton are support for internal organs, as well as providing a person with the ability to move in space. In order to successfully perform them, the bones must have, on the one hand, strength, and on the other - elasticity and lightness. Both of these functions are provided, among other things, due to various types of bone connection.
In addition to support, bones are protection for internal organs, as well as blood-forming organs (due to the spongy substance containing red bone marrow).
Types of bone joint
In the human body there are different types of bones: flat, tubular, mixed, short and long. There are various types of connection of human bones, which provide the skeleton with the ability to perform its functions. There is no unified classification of types of joint joints. Some sources divide bone joints into two, others into three types. According to the first version, these are movable and fixed joints. The third type, which not everyone considers independent, is semi-mobile joints. Most clearly represents the types of bone connection table. Below are the types of mobile connections.
Continuous, or motionless connections
Continuous bone joints are those that have no cavity and are motionless. It is possible to determine a fixed connection even in appearance - the joined surfaces have roughnesses, notches, that is, they are uneven.
Both surfaces come together with connective tissue.
An example is the connection of the bones of the skull, which are formed using a bone suture.
Other immobile joints fuse with each other, that is, the cartilage tissue is replaced by bone, which gives this section special strength. Such types of bone joints can be found in the spine, in the sacral section, where the coccyx is five fused coccygeal vertebrae.
Means of maintaining immobility of bone joints
As can be seen from the examples, immobility is provided in different ways, so there are the main types of bone connection in a continuous way:
- The type of connection is through a dense-fiber type of connective tissue (bones near the joints).
- Syndesmosis, which is a compound with the help of connective tissue (for example, bones of the forearm).
- Synchondrosis - with the help of cartilage (connection of the vertebrae in the spine).
- Synostoses, i.e. bone joints (skull bones, tailbone).
The first and second points are the types of connection of human bones with the help of various types of connective tissue, therefore they are referred to as fibrous compounds.
Syndesmoses perform their function with the help of ligaments, which additionally strengthen bone joints.
The concept of ligaments
They are cords formed by bundles of elastic and collagen fibers. Depending on which type prevails in a particular bundle, they are divided into elastic and collagen.
Depending on the required amplitude, the oscillations of the bones of the ligament can be short or long.
They also distinguish the classification of strands by belonging to joints - articular and extra-articular.
Ligaments are needed not only for connecting bones, they have several more important functions:
- Skeleton role, as the ligaments begin muscles.
- Hold and fix among themselves different parts of the bones or parts of the body (sacral-tuberous ligament).
- Using the ligaments, another anatomical structure is formed (for example, a arch or a niche for the passage of nerves and blood vessels).
Types of connective tissue connections
In addition to ligaments, bone joints can be formed by connective tissue and called membranes. Their difference lies in the fact that the membrane fills the space between the bones, and the distance between them is quite large. Most often, membranes are made up of elastic fibers. However, in their functions, they play the same role with ligaments.
The next type of connective tissue connection between the bones is the fontanel. This type can be observed in newborns and children up to a year, until the fontanels overgrow. This is a formation that has few elastic fibers and is mainly represented by an intermediate substance. This connection allows the bones of the skull to change the configuration for passage through the birth canal.
A suture can be found by studying, for example, joints of the bones of the skull. Seams can be of various shapes, having similar names - serrated, flat, scaly.
Injections connect the alveolar processes with the teeth. Connective tissue in this area is called periodontium. It has good blood supply and nervous innervation due to the vessels and nerve fibers in the intermediate. The periodontal also includes elastic and collagen fibers.
Movable joints
The following types of bone joints are mobile. These include joints (diarthrosis). Discontinuous such types of connection of bones are called due to the fact that there is always a cavity between their surfaces. In order to provide mobility, they consist of articular surfaces, articular bags and cavities.
Components
Joint surfaces are those parts of the bones that adjoin each other in the joint bag. They are covered with cartilage called articular.
In order for such a connection to function properly during a person’s life, the bag has a cavity filled with a fluid that lubricates the closure surfaces. In addition, the liquid performs depreciation functions, providing endurance to the joints, and provides the necessary nutrition for articular cartilage.
The joint bag protects the articular surfaces from damage, for this function it consists of several layers: fibrous and synovial. The inner synovial membrane provides a rich blood supply.
In addition to the mandatory, additional elements may be present in the joint: cartilage and ligaments, synovial bags, sesamoid bones and synovial folds.
Joint classification according to various parameters
The joints can be of various shapes: spherical, ellipsoidal, flat, saddle, etc. In accordance with it, the joints of the same name are isolated. The classification is distinguished by the projection of movement - uniaxial, biaxial and multiaxial. Uniaxial include block and cylindrical joints (for example, ankle, interphalangeal). Biaxial joints - ellipsoidal or saddle-shaped (wrist-metacarpal, wrist). To multiaxial include joints that have a spherical shape - the shoulder, hip.
According to the shape of the joint, it can be assumed in which directions its movement will be carried out. For example, the spherical carries out movements in different directions, that is, it is triaxial.
The device distinguishes between simple and complex joints. Simple consists of two bones, complex - of three or more.
Joints can perform movements of the following types: flexion-extension, reduction-abduction, rotation (in and out, as well as circular).
Semi-mobile bone joints
Many do not consider this group independent. Semi-mobile joints include those that are formed by cartilage, that is, on the one hand, are not mobile, like joints, but they have a certain degree of flexibility.
The type of joint with the help of cartilage is considered as one of the types of motionless joints - synchondrosis, which is not semi-mobile, as many people think. There is a difference between synchondrosis and semi-mobile joints: in the latter there is a small cavity, due to which mobility is ensured.
Semi-continuous compounds are also called symphyses. Under certain conditions, they may diverge somewhat. Thus, the pubic symphysis allows the birth to ensure the passage of the fetus through the birth canal.
Instead of a conclusion
So, we got acquainted with the main types of joints of human bones, their features and functions that they perform.
When considering such topics as types of connection of human bones, a table and a diagram will be the best assistants, since they provide an opportunity to visually see and understand the classification.