How are bones connected in the human body? Doctrine of bones Types of continuous connection of bones table
Each human bone is a complex organ: it occupies a certain position in the body, has its own shape and structure, and performs its own function. All types of tissues take part in bone formation, but bone tissue predominates.
General characteristics of human bones
Cartilage covers only the articular surfaces of the bone, the outside of the bone is covered with periosteum, and the bone marrow is located inside. Bone contains adipose tissue, blood and lymphatic vessels, and nerves.
Bone has high mechanical properties, its strength can be compared with the strength of metal. The chemical composition of a living human bone contains: 50% water, 12.5% organic substances of a protein nature (ossein), 21.8% inorganic substances (mainly calcium phosphate) and 15.7% fat.
Types of bones by shape divided into:
- Tubular (long - shoulder, femoral, etc.; short - phalanges of the fingers);
- flat (frontal, parietal, scapula, etc.);
- spongy (ribs, vertebrae);
- mixed (wedge-shaped, zygomatic, lower jaw).
The structure of human bones
The basic structural unit of bone tissue is osteon, which is visible under a microscope at low magnification. Each osteon includes from 5 to 20 concentrically arranged bone plates. They resemble cylinders inserted into each other. Each plate consists of intercellular substance and cells (osteoblasts, osteocytes, osteoclasts). In the center of the osteon there is a channel - the channel of the osteon; blood vessels run through it. Intercalated bone plates are located between adjacent osteons.
Bone is formed by osteoblasts, releasing the intercellular substance and immuring in it, they turn into osteocytes - cells of a process form, incapable of mitosis, with weakly expressed organelles. Accordingly, the formed bone contains mainly osteocytes, and osteoblasts are found only in areas of growth and regeneration of bone tissue.
The largest number of osteoblasts is located in the periosteum - a thin but dense connective tissue plate containing many blood vessels, nerve and lymph endings. The periosteum provides bone growth in thickness and nutrition of the bone.
osteoclasts contain a large number of lysosomes and are able to secrete enzymes, which can explain the dissolution of bone substance by them. These cells take part in the destruction of the bone. In pathological conditions in the bone tissue, their number increases sharply.
Osteoclasts are also important in the process of bone development: in the process of building the final shape of the bone, they destroy calcified cartilage and even newly formed bone, “correcting” its primary shape.
Bone structure: compact and spongy substance
On the cut, sections of the bone, two of its structures are distinguished - compact matter(bone plates are located densely and in an orderly manner), located superficially, and spongy substance(bone elements are located loosely), lying inside the bone.
Such a structure of bones fully corresponds to the basic principle of structural mechanics - to ensure the maximum strength of the structure with the least amount of material and great ease. This is also confirmed by the fact that the location of the tubular systems and the main bone beams corresponds to the direction of action of the forces of compression, tension and twisting.
The structure of bones is a dynamic reactive system that changes throughout a person's life. It is known that in people engaged in heavy physical labor, the compact layer of bone reaches a relatively large development. Depending on the change in the load on individual parts of the body, the location of the bone beams and the structure of the bone as a whole may change.
Connection of human bones
All bone joints can be divided into two groups:
- Continuous connections, earlier in development in phylogenesis, immobile or inactive in function;
- intermittent connections, later in development and more mobile in function.
Between these forms there is a transition - from continuous to discontinuous or vice versa - semi-joint.
The continuous connection of the bones is carried out through connective tissue, cartilage and bone tissue (the bones of the skull itself). A discontinuous connection of bones, or a joint, is a younger formation of a connection between bones. All joints have a common structural plan, including the articular cavity, articular bag and articular surfaces.
Articular cavity it is allocated conditionally, since normally there is no void between the articular bag and the articular ends of the bones, but there is liquid.
Articular bag covers the articular surfaces of the bones, forming a hermetic capsule. The articular bag consists of two layers, the outer layer of which passes into the periosteum. The inner layer secretes a fluid into the joint cavity, which plays the role of a lubricant, ensuring the free sliding of the articular surfaces.
Types of joints
The articular surfaces of the articulating bones are covered with articular cartilage. The smooth surface of the articular cartilage promotes movement in the joints. The articular surfaces are very diverse in shape and size, they are usually compared with geometric figures. Hence and names of joints according to shape: spherical (shoulder), elliptical (radio-carpal), cylindrical (radio-ulnar), etc.
Since the movements of the articulating links are made around one, two or many axes, joints are also usually divided by the number of axes of rotation into multiaxial (spherical), biaxial (elliptical, saddle) and uniaxial (cylindrical, block-shaped).
Depending on the number of articulating bones joints are divided into simple, in which two bones are connected, and complex, in which more than two bones are articulated.
The bones of the human skeleton are combined into a common functional system (the passive part of the musculoskeletal system) using various types of connections. All bone joints are divided into three types: continuous, discontinuous and symphyses. Depending on the type of tissues that connect the bones, the following types of continuous connections are distinguished: fibrous, bone and synchondrosis (cartilaginous connections) (Fig. 9).
Rice. 9.
A - joint; B - fibrous connection; B - synchondrosis (cartilaginous connection); G. symphysis (hemiarthrosis); 1 - periosteum; 2- bone; 3- fibrous connective tissue; 4 - cartilage; 5 - synovial membrane; 6 - fibrous membrane; 7 - articular cartilage; 8 - articular cavity; 9 - gap in the interpubic disc; 10- interpubic disc
Fibrous joints have great strength and low mobility. These include syndesmoses (ligaments and interosseous membranes), sutures, and impaction.
Ligaments are thick bundles or plates formed by dense fibrous connective tissue with a large number of collagen fibers. In most cases, ligaments connect two bones and reinforce the joints, limiting their movement, and withstand significant loads.
Interosseous membranes connect the diaphysis of tubular bones, serve as a place of attachment of muscles. There are openings in the interosseous membranes through which blood vessels and nerves pass.
A variety of fibrous joints are the sutures of the skull, which, depending on the configuration of the connected edges of the bone, are spongy, scaly and flat. In all types of sutures between the connected bones there are thin layers of connective tissue.
Impaction is a special type of fibrous connection, which is observed in the connection of the tooth with the bone tissue of the dental alveolus. Between the tooth and the bone wall there is a thin plate of connective tissue - paradont.
Synchondrosis - connection of bones with the help of cartilage tissue. They are characterized by elasticity, strength; they perform amortization function.
The replacement of cartilage between bones by bone tissue is called synostosis. Mobility in such compounds disappears, and strength increases.
Discontinuous (synovial or articular) joints are the most mobile joints of bones. They have great mobility and a variety of movements. Characteristic features of the joint are the presence of articular surfaces, articular cavity, synovial fluid and capsule. The articular surfaces of the bones are covered with hyaline cartilage with a thickness of 0.25 to 6 mm, depending on the load on the joint. The articular cavity is a slit-like space between the articular surfaces of the bones, which is surrounded on all sides by the articular capsule and contains a large amount of synovial fluid.
The joint capsule covers the connecting ends of the bones, forms a sealed bag, the walls of which have two layers: the outer one is fibrous and the inner one is the synovial membrane.
The outer fibrous layer consists of a dense fibrous connective tissue with a longitudinal direction of the fibers and provides the articular capsule with significant strength. In some joints, the fibrous layer can form thickenings (capsular ligaments) that strengthen the articular bag.
The inner layer (synovium) has small outgrowths (villi rich in blood vessels) that greatly increase the surface of the layer. The synovial membrane produces a fluid that hydrates the articular surfaces of the joints, eliminating their friction against each other. In addition, this shell absorbs liquid, ensuring a continuous metabolic process.
If the articular surfaces do not match, there are cartilaginous plates of various shapes between them - articular discs and menisci. They are able to shift during movements, smooth out the irregularities of the articulating surfaces and perform a shock-absorbing function.
In some cases (for example, the shoulder joint), along the edge of the articular surface in one of the bones, there is an articular lip, which deepens it, increases the area of the joint, and gives a greater conformity to the shape of the articulating surfaces.
Depending on the structure of the articulating surfaces in the joints, movements can be made around different axes. Flexion and extension are movements around the frontal axis; abduction and adduction - around the sagittal axis; rotation - around the longitudinal axis; circular rotation - around all axes. The amplitude and range of movements in the joints depend on the difference in the angular degrees of the articulating surfaces. The greater this difference, the greater the range of motion.
By the number of articulating bones, the shape of their articular surfaces, the joints may differ from each other.
A joint formed by only two articular surfaces is called a simple joint, and a joint of three or more articular surfaces is called a complex joint.
There are complex and combined joints. The former are characterized by the presence of an articular disc or meniscus between the articulating surfaces; the latter are represented by two anatomically isolated joints that act together (temporomandibular joint).
According to the shape of the articular surfaces, the joints are divided into cylindrical, elliptical and spherical (Fig. 10).
1 - block-shaped; 2 - elliptical; 3 - saddle; 4 - spherical
There are also variants of the above forms of joints. For example, a type of cylindrical joint is a block-shaped joint, a spherical joint is a bowl-shaped and flat joint. The shape of the articular surfaces determines the axes around which movement occurs in a given joint. With a cylindrical shape of the articular surfaces, the movement is carried out around one axis, with an elliptical shape - around two axes, with a spherical shape - around three or more mutually perpendicular axes. Thus, there is a certain relationship between the shape of the articular surfaces and the number of axes of motion. In this regard, one-, two- and three-axis (multi-axial) joints are distinguished.
Uniaxial joints include cylindrical and block-shaped. For example, in a cylindrical joint, rotation occurs around a vertical axis that coincides with the axis of the bone (rotation of the 1st cervical vertebra along with the skull around the odontoid process of the 2nd vertebra). In block joints, rotation occurs around one transverse axis, for example, flexion and extension in the interphalangeal joints. The screw joint also belongs to the block-shaped joint, where the movement is carried out in a spiral (shoulder-ulnar joint).
Biaxial joints include elliptical, saddle and condylar joints. In the elliptical joint, movements occur around mutually perpendicular axes (for example, the wrist joint) - flexion and extension around the frontal axis, adduction and abduction - around the sagittal axis.
In the saddle joint (carpometacarpal joint of the thumb of the hand), movements occur similar to those in the elliptical joint, that is, not only abduction and adduction, but also opposition of the thumb to the rest.
The condylar joint (knee joint) is a transitional form between the block-shaped and elliptical. It has two convex articular heads that resemble the shape of an ellipse and are called condyles. In the condylar joint, movement around the frontal axis is possible - flexion and extension, around the longitudinal axis - rotation.
Triaxial (multiaxial) joints include spherical, bowl-shaped and flat joints. In the spherical joint, flexion and extension, adduction and abduction, as well as rotation occur. As a result of a significant difference in the size of the articular surfaces (the head of the joint and the articular cavity), the spherical (shoulder) joint is the most mobile among all joints.
The cup-shaped joint (hip joint) is a type of ball-and-socket joint. It differs from the latter by a greater depth of the articular cavity. Due to the small difference in the angular dimensions of the articular surfaces, the range of motion in this joint is small.
In flat joints, movements are carried out around three axes, but the amplitude of rotation is limited due to the slight curvature and size of the articular surfaces. Flat joints include arcuate (intervertebral), tarsal-metatarsal joints.
The bones forming can be connected in various ways - motionless, semi-movable and movable.
A fixed connection is characteristic of most bones of the skull: numerous protrusions of one bone enter the recess of another, forming a strong seam. The bones are fixedly connected as a result of fusion. This is how the vertebrae of the coccyx are interconnected.
interconnected by discs- elastic pads. The vertebrae "slide" relative to each other, but their mobility is limited. It is thanks to their semi-movable connection that you tilt your torso, turn, etc.
A movable joint of bones is a joint that provides complex movements. How is the joint arranged? On one of the bones is located the articular cavity, which includes the head of the other bone. Their surfaces are covered with a layer of smooth. The bones in the joint are tightly pulled together by ligaments - strong strands of connective tissue.
articular connection from the outside it is surrounded by an articular bag, the cells of which secrete a viscous fluid. It reduces the friction of the bones in the joint when they move. Joints differ in shape and number of rotation axes. Bones have the greatest mobility in joints with three axes, and the smallest - with one axis of rotation.
Structure
In the human skeleton, the same sections are distinguished as in other mammals: the skeletons of the head, trunk and limbs.
- this is . The bones of the brain section reliably protect the brain. In the occiput there is a large opening through which the spinal cord passes into the cranial cavity, and through many small openings - nerves and blood vessels. The largest in the facial region are the bones of the jaw: fixed upper and movable lower. They have teeth, the roots of which enter into special bone cells of these bones. The brain section of the human skull is larger than the facial one, since the human brain is more developed than that of other mammals. But due to a change in the type of food, the jaws of a person are less developed.
In the skeleton of the body, the spine and chest are distinguished. The spine is the backbone of the body's skeleton. It is formed by 33-34 vertebrae.
The vertebra consists of a massive body, an arch and several processes to which muscles are attached. The arc and the body form a ring. The vertebrae are arranged one above the other so that the bodies make up the spinal column, and the rings make up the spinal canal, which forms the bony sheath of the spinal cord.
The spine is divided into cervical, thoracic, lumbar and sacral regions. The lumbar vertebrae are massive: due to upright posture, this part of the spine is subjected to the greatest stress. The sacral vertebrae are fused together, as are the coccygeal vertebrae. The coccygeal vertebrae are undeveloped and correspond to the tail vertebrae of animals.
Spine
Spine has four bends, giving it elasticity, this property helps to prevent concussion during jumps.
Rib cage
Rib cage formed by the thoracic vertebrae, twelve pairs of ribs and a flat sternum, or sternum. With the help of cartilages, the anterior ends of ten pairs of upper ribs are connected, and their posterior ends are semi-movably connected to the thoracic vertebrae. This ensures the mobility of the chest during breathing. The two lower pairs of ribs are shorter than the rest and end freely. The chest protects the heart and lungs, liver and stomach. It is wider in men than in women.
limb skeleton
It consists of two sections: the skeleton of the upper limbs and the skeleton of the lower limbs. In the skeleton of the upper limbs, the skeleton of the shoulder girdle and the skeleton of the hand are distinguished. The skeleton of the shoulder girdle consists of paired bones: two shoulder blades and two clavicles. These bones provide support for the arms attached to them. shoulder blade- a flat bone connected to the ribs and spinal column only with the help of muscles. The clavicle is a slightly bent bone, which at one end is connected to the scapula, and at the other end to the sternum. The outer angle of the scapula, together with the head of the humerus, forms the shoulder joint. The bones of the skeleton of the upper extremities in men are more massive than in women.
AT skeleton hand three sections: shoulder, forearm and hand. The shoulder has only one humerus. The forearm is formed by two bones: the ulna and the radius. The humerus is connected by the elbow joint with the bones of the forearm, and the forearm is movably connected to the bones of the hand. Three sections are distinguished in the hand: the wrist, hand and phalanges of the fingers. The skeleton of the wrist is formed by several short spongy bones. Five long bones of the hand make up the skeleton of the palm and support the phalanges - the bones of the fingers. The phalanges of each finger are movably connected to each other and to the corresponding bones of the hand. A feature of the structure of the human hand is the location of the phalanges of the thumb, which can be placed perpendicular to all the others. This allows a person to perform various precise movements.
Skeleton of the lower extremities
Consists of a pelvic girdle skeleton and a leg skeleton. The pelvic girdle is formed by two massive flat pelvic bones. Behind, they are firmly connected to the sacral spine, and in front - to each other. In each pelvic bone is a spherical cavity, with which the head of the femur is combined, forming the hip joint. The pelvic girdle supports the internal organs from below. It has such a structure only in humans, which is due to upright walking. The pelvic girdle is wider in women than in men.
The skeleton of the legs consists of the bones of the thigh, lower leg and foot, which are adapted to significant physical exertion. The mobile foot is formed by short bones of the tarsus, among which the calcaneus is the most massive, as well as five long bones of the metatarsus and bones of the flanks of the fingers. The bones of the skeleton of the legs in men are more massive than in women.
Introduction
Physiology is the science of functions, i.e. about the vital activity of organs, systems and the organism as a whole. Its ultimate goal is the knowledge of functions, which would provide the possibility of active influence on them in the desired direction.
The value of the musculoskeletal system is very high. The supporting function is that the skeleton supports all other organs, gives the body a certain shape and position in space. The musculoskeletal system is presented in the form of two systems - bone and muscle.
Bones, connected by cartilage, ligaments, as well as muscles attached to them, form cavities (receptacles) in which vital organs are located. This is a protective function of the musculoskeletal skeleton. The motor function is carried out mainly by muscles.
Of no small importance to the musculoskeletal system are exercises for the development of movement. These classes allow us to maintain our body in the right shape, improve and develop various abilities.
Types of bones. Types of bone connection
The bones that make up the skeleton make up approximately 18% of the total body weight.
The classification of bones is currently carried out not only on the basis of their structure, but also on the basis of function and development. As a result, there are tubular, spongy, flat and mixed bones.
Tubular bones carry the function of support, protection and movement. They are shaped like a tube with a medullary canal inside. The relatively thinner middle part of the tubular bones is called the body or diaphysis, and the thickened ends are called the epiphyses. The thickening of the ends of long tubular bones is functionally substantiated. The epiphyses serve as the junction of bones with each other, here muscle attachment occurs. The wider the contact surface of the bones, the stronger; more stable connection. At the same time, the thickened epiphysis moves the muscle away from the long axis of the bone, as a result of which the latter approaches the site of attachment at a large angle. This, according to the rule of parallelogram of forces, increases the efficiency of the muscle. Tubular bones are divided into long and short.
Long bones, the length of which significantly exceeds their other sizes, make up the proximal links of the skeleton of both limbs.
Short bones are located in the metacarpus, metatarsus, phalanges, t. where at the same time greater strength and mobility of the skeleton are needed.
Spongy bones are divided into long, short, sesamoid.
Long spongy bones (ribs, sternum) consist mainly of a spongy substance covered with a compact substance, they have the function of support and protection.
Short spongy bones (vertebrae, bones of the wrist, tarsus) consist mainly of spongy substance, serve as a support.
Sesamoid bones (patella, pisiform bone, sesamoid bones of the fingers and toes) consist of spongy substance, develop in the thickness of the tendons, strengthen the latter and serve as a block through which they are thrown. This increases the leverage of muscle force application and creates more favorable conditions for its work. Sesamoid bones got their name for their resemblance to sesame seeds.
Flat bones form the walls of cavities containing internal organs. Such bones are curved on one side, convex on the other; their width and length significantly predominate over their thickness. These are the pelvic bone, scapula, bones of the brain skull.
Mixed bones lie at the base of the skull, have a different shape and development, the complexity of which corresponds to the variety of functions performed.
Among the flat and mixed bones of the skull, there are air-bearing ones, containing a cavity lined with a mucous membrane and filled with air, which lightens the bones without compromising their strength.
The relief of the bone surface is not the same and is due to the mechanical action of neighboring organs. The vessels and nerves adjacent to the skeleton, the muscles and their tendons leave traces on the bones in the form of grooves, notches, holes, roughness and channels. Areas on the surface of the bone, free from attachment of muscles and ligaments, as well as articular surfaces covered with hyaline cartilage, are completely smooth. The surfaces of the bones in the places of attachment of strong muscles to them are elongated in the form of tuberosities, tubercles and processes, increasing the area of attachment. Therefore, in people whose profession is associated with the implementation of a large physical load, the surfaces of the bones are more uneven.
The bone, with the exception of the connecting surfaces, is covered with periosteum. This is a thin connective tissue sheath, which is rich in nerves and blood vessels that penetrate from here into the bone through special openings.
Through the periosteum, bone nutrition and its innervation are carried out. The value of the periosteum lies in facilitating the attachment of the muscles and ligaments that are woven into its outer layer, as well as in softening the shocks. The inner layer of the periosteum contains bone-forming cells - osteoblasts, which ensure the growth of developing young bones in thickness.
In bone fractures, osteoblasts form a callus that connects the ends of a broken bone, restoring its integrity.
Classification of compounds. The mobility of parts of the skeleton depends on the nature of the joints of the bones. The apparatus connecting the bones develops from the mesenchyme, which lies between the rudiments of these bones in the embryo. There are two main types of bone connections: continuous and discontinuous, or joints. The former are more ancient: they are found in all lower vertebrates and in the embryonic stages of higher ones. When bones are laid in the latter, their original material (connective tissue, cartilage) is preserved between them. With the help of this material, the bones are fused, i.e., a continuous connection is formed. At later ontogenetic stages, more perfect, discontinuous connections appear in terrestrial vertebrates. They develop due to the appearance of a gap in the original material preserved between the bones. Remnants of cartilage cover the articulating surfaces of the bones. There is a third, intermediate type of joints - a semi-joint.
Continuous connections. A continuous connection - synarthrosis, or fusion - occurs when the bones are connected to each other by a continuous layer connecting their tissues. Movement is limited or non-existent. By the nature of the connective tissue, there are connective tissue adhesions, or syndesmoses, cartilaginous adhesions, or synchondrosis, and adhesions with the help of bone tissue - synostoses.
Syndesmoses are of three kinds: 1) interosseous membranes, for example, between the bones of the forearm or lower leg; 2) ligaments connecting bones (but not associated with joints), for example, ligaments between the processes of the vertebrae or their arches; 3) seams between the bones of the skull. Interosseous membranes and ligaments allow some displacement of the bones. In the seams, the layer of connective tissue between the bones is insignificant and movements are impossible.
Synchondrosis is, for example, the connection of the 1st rib with the sternum by means of costal cartilage, the elasticity of which allows some mobility of these bones.
Discontinuous connections - diarthrosis, articulation, or joint, characterized by the presence of a small space (gap) between the ends of the connecting bones. There are simple joints, formed by only two bones (for example, the shoulder joint), complex, when a larger number of bones are included in the joint (for example, the elbow joint), and combined, allowing movement only simultaneously with movement in other, anatomically separate, joints (for example, proximal and distal radioulnar joints). The obligatory structural formations of the joint include the articular surfaces, the articular bag, or capsule, and the articular cavity.
In addition to the mandatory ones, auxiliary formations can occur in the joint. These include articular ligaments and lips, intra-articular discs and menisci.
There are two types of bone connections - continuous and discontinuous.
1. Continuous connection of bones– synarthrosis -synarthrosis . Depending on what tissue connects the bones, there are five types of synarthrosis: synsarcosis, synelastosis, syndesmosis, synchondrosis, synostosis.
Synsarcosis– synsarcosis - the connection of bones through muscles.
synelastosis– synelastosis - the bones are connected using elastic tissue that can be highly stretched and resist rupture. Synelastoses include the supraspinous and nuchal ligaments.
syndesmosis– syndesmosis bones are connected by dense connective (fibrous) tissue. Its collagen fibers are soldered by loose connective tissue into bundles, strands or membranes. Syndesmoses occur as ligaments, membranes, sutures and impaction.
Bundle – ligamentum- Formed by bundles of collagen fibers moving from one bone to another.
Membrane – membrane- consists of bundles of collagen fibers that form thin plates between the bones (for example, the membrane in the occipito-atlantic joint).
The seam –sutura- a special type of connection of the lamellar bones of the skull. Connective tissue is located in the form of a very thin layer between two connecting bones. According to the structure of the contacting surfaces of the bones, it distinguishes sutures: flat, serrated, foliate, scaly.
flat seam –sutura plana- when the edges of the connecting bones have smooth surfaces. Such a connection is characterized by fragility and therefore, during digestion or maceration, the bones are easily separated from the skeleton (the connection of the nasal bones to each other, especially in ruminants).
notched seam –sutura serrata (from serra- saw)- the jagged edges of the connecting bones enter into each other (the connection of the nasal bones with the frontal or frontal bones with the parietal). The serrated seam is very durable.
Leaf seam –sutura foliata(fromfolia- sheet)- in shape it resembles a dentate, but its individual teeth in the form of a woody leaf are deeply embedded in the edge of the adjacent bone (the connection of the wings of the sphenoid bone with the frontal and parietal bones). This connection is highly durable.
Scale seam –sutura squamosa(from squama – scales ) - when the edges of the bones overlap each other, like the scales of a fish (connection of the parietal bone with the scales of the temporal bone).
Injection – gomphosis ( from gomphos – nail ) - characteristic for the connection of teeth with the incisor, maxillary and mandibular bones, when each tooth, located in the alveolar recess, has a dental ligament ( lig. dentale), which is the periosteum, or periodontium ( periodontum, from peri– around + odontos- tooth) and which is common to both the alveoli and the root of the tooth.
Synchondrosis–synchondrosis - bones are connected by cartilage tissue - hyaline or fibrous. In synchondroses without great mobility, there is hyaline cartilage, for example, in the joints between the epiphyses and the diaphysis of the tubular bones of young animals. In the presence of high mobility in synchondrosis, there is fibrous cartilage in the form of discs, for example, between the vertebrae.
Connections of bones through connective and cartilaginous tissue with age of animals can ossify. This bone connection is called synostosis–synostosis .
Bone mobility in synarthrosis depends primarily on the physical properties of the connective tissue. Thus, maximum mobility is observed in synsarcosis, followed by synelastosis, syndesmosis and synchondrosis in descending order. There is no mobility in synostoses.
2. Discontinuous connection of bones–diarthrosis–diarthrosis or a jointarticulation .
The joint is characterized by the presence of a slit-like cavity between the bones. Joints connect bones that perform the function of movement.
Mandatory structural elements of the joint:
articular surfaces - facies articulares.
Articular cartilage - cortilago articularis.
joint capsule - capsula articularis.
articular cavity - cavum articulare.
joint fluid - sinovia.
Auxiliary joint formations:
Intra-articular ligaments ligamentum interarticulares.
Articular lips (hip joint) - labia articulares.
articular discs - discus articulares.
Articular menisci - meniscus articulares.
Sesamoid bones – ossa articulares.
Articular surfaces – facies articulares - formed by two or more articulating bones. The relief of the articular surfaces to a certain extent affects the volume and functional functions of the joints. Articular surfaces covered with articular cartilage are usually congruent, i.e. congruent (from congruo- converge, coincide) and in rare cases - mismatched, or incongruent. Incongruence is eliminated due to intra-articular inclusions - articular lips, discs, menisci.
articular cartilage – cartilago articularis - covers the articular surfaces of bones. According to the type of structure, it is hyaline, having a smooth surface, reduces friction between the bones.
joint capsule–ca psula articularis - consists of two membranes: outer (fibrous) and inner (synovial). The fibrous membrane of the capsule is a continuation of the periosteum, which passes from one bone to another. The synovial membrane is built of loose connective tissue, it is rich in blood vessels and nerves, and from the side of the articular cavity is lined with one or more layers of connective tissue cells that secrete synovial fluid into the cavity.
Articular cavity – cavum articulare - is a slit-like space between the articular surfaces and the ends of the articulating bones, surrounded by a joint capsule. It is sealed and contains a small amount joint fluid.
Joint fluid, or synovia-si novia - has a yellow color, is transparent and has a significant viscosity. Synovia performs various functions: lubricates the articular surfaces of bones, thereby reducing friction between them; serves as a nutrient medium for articular cartilage; plays a buffering role.
By structure, the joints are of two types:
1. Simple joints -articulation simplex , in the formation of which only two bones participate.
2. Complex joints -articulation composite formed by more than two articulating bones or contain auxiliary formations in their joint (intra-articular ligaments, menisci, discs, sesamoid bones).
It also distinguishes combined joints, when movement is carried out simultaneously in several joints, as, for example, in paired jaw joints, in the occipito-atlantic and atlant-axial joints.
By function, the joints are divided into uniaxial, biaxial and multiaxial.
In uniaxial joints, movement occurs around one axis: bending -f l exi o and extension -extensio . According to the shape of the articular surface, these joints can be block-shaped, helical and rotational.
In biaxial joints, movement occurs along two axes perpendicular to each other: along the segmental axis - flexion and extension, along the sagittal axis - abduction -abductio and cast -adductio . By the nature of the articular surface of the bones, biaxial joints can be ellipsoidal and saddle-shaped.
In multiaxial joints, movement is possible along many axes, since the articular surface on one of the bones represents part of the ball, and on the other, the corresponding fossa. Such a joint is called spherical (for example, the shoulder and hip joints). In this type of joints, movements are possible: along the segmental axis - extension and flexion, along the sagittal axis - abduction and adduction. Along an axis drawn longitudinally through the center of the bone, movements are possible: rotation -rotation ; outward rotation - supination -supinatio ; inward rotation - pronation -pronatio .
Questions to consolidate the studied material.
Types of bone joints and their varieties.
What is typical for continuous connections?
What is syndesmosis, suture, hammering, synchondrosis, symphysis, synsarcosis and their characteristic differences.
What is characteristic of discontinuous connections?
The main structural components of a discontinuous connection.
Classification of joints and their morphological characteristics.
Ligaments of joints and their varieties.
Intra-articular inclusions and their characteristics.
Combined joints and their characteristics.
Types of seams and their characteristics (with examples).
Factors affecting the development, structure and specialization of bone joints.
Practical value of knowledge of artrology for biology, zootechnics, veterinary medicine?
