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 moved by muscles and tendons. The 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.
Functions of the human skeleton
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, on the other, elasticity and lightness. Both of these functions are provided, among other things, thanks to various types of bone connection.
In addition to support, bones are a protection for internal organs, as well as hematopoietic organs (due to the spongy substance containing red bone marrow).
Types of bone connections
There are different types of bones in the human body: flat, tubular, mixed, short and long. Existvarious types of connection of human bones, which provide the skeleton with the ability to perform its functions. There is no single classification of bone articulation types. Some sources divide bone connections into two, others into three types. According to the first version, these are mobile and fixed connections. The third type, which not everyone considers independent, is semi-movable connections. The table most clearly represents the types of bone connections. Below are the types of movable connections.
Continuous or fixed connections
Continuous connections of bones are those that do not have a cavity and are immovable. You can even determine a fixed connection by its appearance - the surfaces to be joined have roughness, notches, that is, they are uneven.
Both surfaces are closed with connective tissue.
An example is the joints of the bones of the skull, which are formed using a bone suture.
Other fixed joints fuse with each other, that is, cartilage is replaced by bone, which gives this department a special strength. These types of bone connections can be found in the spine, in the sacral region, where the coccyx is five fused coccygeal vertebrae.
Means for maintaining immobility of bone joints
As you can see from the examples, immobility is provided in different ways, so there are basic types of connecting bones in a continuous way:
- A type of connection by dense fibrous connective tissue (bones near joints).
- Syndesmoses, which are connections using connective tissue (for example, the bones of the forearm).
- Synchondroses - with the help of cartilage (the connection of the vertebrae in the spine).
- Synostoses, that is, bone connections (bones of the skull, coccyx).
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 connections.
Syndesmoses carry out their function with the help of ligaments, which additionally strengthen the joints of the bones.
The concept of bundles
They are strands formed by bundles of elastic and collagen fibers. Depending on which type prevails in a particular ligament, they are divided into elastic and collagen.
Depending on the required amplitude, the vibrations of the bones of the ligament can be short or long.
There is also a classification of cords according to belonging to the joints - articular and extra-articular.
Ligaments are needed not only to connect bones, they have several other important functions:
- Frame role, since muscles begin with ligaments.
- Hold and fix various parts of the bones or parts of the body (sacral-tuberous ligament) between themselves.
- With the help of ligaments, another anatomical structure is formed (for example, a vault or a niche for the passage of nerves and blood vessels).
Typesconnective tissue connections
In addition to ligaments, bone connections can be formed by connective tissue and are 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 consist of elastic fibers. However, in terms of their functions, they perform the same role with bundles.
The fontanel is the next type of connective tissue connection between bones. 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 represented mainly by an intermediate substance. This connection allows the bones of the skull to reconfigure to pass through the birth canal.
The seam can be found by studying, for example, the joints of the bones of the skull. The seams can be of various shapes, having similar names - jagged, flat, scaly.
Injections connect the alveolar processes with the teeth. The connective tissue in this area is called the periodontium. It has a good blood supply and nerve innervation due to vessels and nerve fibers in the intermediate substance. Periodontium also contains elastic and collagen fibers.
Mobile connections
The following types of bone connections are movable. These include joints (diathrosis). Such types of bone connections are called discontinuous due to the fact that there is always a cavity between their surfaces. In order to provide mobility, theyconsist of articular surfaces, joint capsule and cavity.
Component parts
Articular surfaces are those parts of the bones that are adjacent to each other in the articular bag. They are covered with cartilage called articular.
In order for such a connection to perform its function properly during a person's life, the bag has a cavity filled with a liquid that lubricates the contact surfaces. In addition, the fluid performs shock-absorbing functions, providing endurance to the joints, and provides the necessary nutrition to the articular cartilage.
The articular bag protects the articular surfaces from damage; to perform 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.
Classification of joints according to various parameters
Joints can be of different shapes: spherical, elliptical, flat, saddle, etc. In accordance with it, joints of the same name are also distinguished. There are also classifications according to the projection of movement - uniaxial, biaxial and multiaxial. Uniaxial include block-shaped and cylindrical joints (for example, ankle, interphalangeal). Biaxial joints - ellipsoid or saddle-shaped (carpal-metacarpal, radiocarpal). Multiaxial joints include joints that have a spherical shape - shoulder, hip.
Pothe shape of the joint can be assumed in which directions its movement will be carried out. For example, a spherical one carries out movements in different directions, that is, it is triaxial.
According to the device, simple and complex joints are distinguished. Simple ones consist of two bones, complex ones consist of three or more.
The joints can perform the following types of movements: flexion-extension, adduction-abduction, rotation (in and out, and also circular).
Semi-movable bone joints
Many do not consider this group independent. Semi-movable joints include those formed by cartilage, that is, on the one hand, they are not mobile, like joints, but they have a certain degree of flexibility.
The type of cartilage connection is considered as one of the types of fixed connection - synchondrosis, which is not semi-movable, as many people think. There is a difference between synchondrosis and semi-mobile joints: the latter have a small cavity, due to which mobility is ensured.
Semi-continuous connections are also called symphyses. Under certain conditions, they may diverge somewhat from each other. So, the pubic symphysis allows during childbirth to ensure the passage of the fetus through the birth canal.
Instead of a conclusion
So, we got acquainted with the main types of human bone joints, their features and functions that they perform.
When considering such a topic as connection typeshuman bones, a table and a diagram will be the best helpers, as they make it possible to visually see and understand the classification.
