Department of Human Anatomy KNMU ARTICULAR SYSTEM GENERAL INFORMATION

1. Department of Human AnatomyKNMUARTICULAR SYSTEMGENERAL INFORMATION Slide-lecture for students of the 6 Faculty of Medicine Leсktor – associate professor Zharova Nataliya 2015

2. PLAN: Development of joints. Classification of bone articulations. Continuous bone articulations. Synovial joints. The most typical features of the joints. Accessory structures of joints. Congruent and incongruent joints. Movements in the joints. Classification of the joints based on the number of articulating surfaces. Classification of the joints based on the shape of articulating surfaces. Clinical applications.

3. Development of joints Embryonic development of the joints is greatly dependent on the bone development. In the areas, where discontinuous articulations will form between the developing bones, the mesenchyme is resorbed in the center of the primordium forming a cleft-like cavity of the future joint. On the contrary, peripheral regions of the mesenchyme, which surround the cavity, condense, giving rise to the fibrous capsule and ligaments of the joint. Cartilaginous epiphyses ossify in such away that a thin layer of articular cartilage remains on their surfaces for life, which provides the smoothness of articular surfaces.

4. CLASSIFICATION OF BONE ARTICULATIONS Continuous articulations(synarthroses)are characterized by the presence of an uninterrupted articulating tissue -connective, cartilaginous, or osseous. Such articulations are either slightly movable or completely fixed. Discontinuous (synovial) articulationscontain a cavity lined with the synovial membrane. They possess a great mobility. They are called joints. Intermediate formsbetween the continuous and discontinuous articulations are symphyses (or hemiarthroses). They are represented by the cartilaginous articulations with the cleft-like cavity lacking a fibrous capsule and without synovial membrane.

5. CONTINUOUS BONE ARTICULATIONS Depending on the tissue type, which articulates two bones, continuous articulations are divided into fibrous, syndesmoses, cartilaginous, synchondroses, osseous, synostoses.

7. Syndesmoses,syndesmosis, (juncturae fibrosae) are formed from the fibrous connective tissue and are divided into the following groups: gomphosis,gomphosis, dentoalveolar syndesmosis, a fibrous articulation between the periodontium of alveolar socket and the root of the tooth; sutures,sutura, fibrous articulations between the bones of the skull, which contain a thin layer of connective tissue; fontanelles,fonticuli, between bones of skull of the new-born; interosseous membranes,membranae interosseae; ligaments,ligamenta, most of the ligaments consist of a dense regular connective tissue. Fibers in the ligaments run obliquely and cross over like in the rope. Therefore, ligaments are quite resilient. Collagen fibers of the ligaments, besides resiliency, provide great elasticity. Some ligaments, besides collagen fibers, contain a considerable amount of elastic tissue yellow in color. They are characterized by lower resilience but greater elasticity. They perform a shock-absorbing function (e.g. yellow ligaments of the vertebral column). Because of their low resilience, elastic ligaments are not very common in the body.

12. SYNCHONDROSES: ACCORDING TO THE DURATION OF THE EXISTENCE :1—TEMPORARY— exist only to the definite age. 2—PERMANENT— exist throughout the life. ACCORDING TO THE PROPERTY OF THE CARTILAGINOUS TISSUES :1—HYALINE— between I rib and sternum. 2—FIBROUS—between vertebral bodies. These cartilages have no vessels and nerves.

15. When ossified, synchondrosis can be transformed into the osseous articulation synostosis(synostosis). Synostosesor bone articulations (juncturaossea)is contiguous joining of bones by means of bone tissue, for instance, synostoses between three bones of the hip bone in an adult.

16. SYNOVIAL JOINTS Thesynovial articulations (juncturaesynoviales, articulatio, diarthrosis) are discontinuous joints characterized by the presence of the synovial membrane. They are also characterized by a variety of movement amplitudes. Consequently these joints are most common in higher vertebrates and humans.

17. THE MOST TYPICAL FEATURES OF THE JOINTS Each joint possesses four basic elements: articular surfaces, faciesarticulares; articular capsule, capsulaarticularis; articular cavity, cavitasarticularishermetically sealed, cleft-like cavity; between the articulating bones. synovial fluid

19. Articular surfaces.The articular surfaces of the bones are covered with the hyaline cartilage (sometimes fibrous), which is 2.5 mm thick on average. The thickness of the cartilage depends on the amount of compression experienced by the joint. The surface of the cartilage is not covered with the perichondrium. The surface is smooth lubricated with the synovial fluid which reduces friction to minimum and facilitates the movement. Articular capsule.The capsule of the joint attaches to the edges of articular surfaces or somewhat over them. The articular capsule hermetically seals the articular cavity and consists of two layers - external fibrous layer, membrana fibrosa, and internal synovial layer, membrana synovialis. The fibrous layer of the capsule has a mechanical function. It consists of bundles of resilient connective tissue fibers, which attach to the bone penetrating it in the form of Sharpie's fibers. Synovial membrane. This layer of the articular capsule is a thin connective tissue membrane, which is lined on the inside with squamous synovial cells of mesenchymatous origin. Consequently, the synovial membrane can form folds and protrusions.

20. Synovial folds and bursae.The synovial membrane is well developed and, in the majority of the joints forms large folds, plicae synoviales, which contain adipose tissue. They go into the articular cavity, filling its potential spaces and forming cushions, which absorb shock during motion. In certain regions, most frequently in the areas of muscular tendons, the synovial membrane protrudes through the clefts in the fibrous layer and forms synovial bursae. They serve to reduce friction during tendons' movement and can be attributed to the accessory muscular apparatus. Synovial villi.The synovial layer bears numerous, microscopic, synovial villi, villi synoviales, which significantly increase its surface area, contain capillary networks, and produce the synovial fluid. Synovial fluid.In the articular cavity there is a small amount of pale, thick, synovial fluid. It is produced by the synovial membrane. The synovial fluid lubricates the articular surfaces and reduces friction between them. Synovial cavity.Under normal circumstances, the synovial cavity is a thin cleft, bounded by the synovial membrane and the articular surfaces. Between the latter, there is a thin layer of synovial fluid, which separates articulating surfaces. In the pathological processes, the synovial cavity can accumulate large amounts of inflammatory liquid and greatly increases in size.

21. Accessory structures of joints Synovial joints may possess several accessory elements, which facilitate movement to a certain extent: articular disc,discus articularis, a cartilaginous plate, which completely separates the joint into two regions; articular meniscus,meniscus articularis, cartilaginous semilunar plate, which partially separates the synovial cavity; articular lip, labrum articularis, a cartilaginous rim or lip, which deepens the articular socket; intraarticular ligaments, ligg. intraarticularia, connect bones within the joint; they are covered with the synovial membrane. Auxiliary strengthening apparatus of joints– ligaments and tendons of muscles. There are extra-articular and intra- articular ligaments, covered by synovial membranes.

22. Factors, which aid in the stabilization of articular surfaces: The fibrous capsule, which is reinforced by the ligaments; Muscles, which surround the joint and actively hold the bones together due to a constant muscle tone; Molecular attraction of articular surfaces, lubricated by the synovial fluid.

23. Congruent and incongruent joints In those cases, when articulating surfaces entirely correspond to each other and appear as imprints of one another, joints are called congruent (congruo - correspond). In such joints, articular surfaces are tightly joined together as, for example, in the hip joint, in which movements are largely restricted. Incongruent joints have a greater degree of freedom in their movements due to the incomplete correspondence of the articulating surfaces. These joints possess accessory structures such as disks, menisci, synovial folds, which fill the irregularities in the articular surfaces and smooth out their incongruence. The knee joint is an example of the incongruent joint.

24. Movements in the joints The frontal axis runs through the joint from right to left. Flexion (flexio) and extension (extensio) of the shoulder occur around the frontal axis. The sagittal axis is drawn from front to back. Abduction (abductio) and adduction (adductio) of the shoulder occur around this axis. The vertical axis runs through the joint and through the entire arm from the top to the bottom. Medial and lateral rotations (rotatio) of the humerus occur around this axis. Circumduction (circumductio) takes place when the movement passes from one axis to another, as when the hand moves in a circular path. Circular movements are possible in multi-axial and bi-axial joints.

25. CLASSIFICATION OF JOINTS Classification of the joints based on thenumber of articulating surfaces: simple - is composed of only two articulating surfaces; compound - contains more than two articulating surfaces; complex joint - if a joint contains articular discs or menisci, which divide it into two parts; combined joints - two isolated joints, in which movements occur simultaneously.

26. Classification of the joints based on the shape of articulating surfaces: Uni-axial joints Bi-axial joints Multi-axial joints

27. Uni-axial joints. In these joints, movement is restricted to a single axis. There are two types of uni-axial joints: hinge joint, ginglymus, contains articulating surfaces, which resemble hinges (for example, interphalangeal joints of the hand and foot); pivot joint, art. trochoidea (art. cylindrica), a cylindrical joint, formed by the convex and concave articulating surfaces cylindrical in shape (for example, proximal and distal radio-ulnar joints).

28. Bi-axial joints. These joints permit movements around two axes, which are perpendicular to each other. The following bi-axial joints are distinguished based on their shape: ellipsoid joint,art. ellipsoidea, contains elliptical (egg-shaped) articulating surfaces (for example, radiocarpal joint); bicondylar joint,art. bicondylaris, consists of a pair of convex, ellipsoid, articulating surfaces, which are rather prominent. Hence, they are known as condyles (for example, knee joint); saddle joint,art. sellaris, contains two articulating surfaces each of which resembles a saddle (for example, carpometacarpal joint of the thumb).

29. Multi-axial joints include spheroidal joints and their variations. Even though, in principle, movements in these joints arc possible around multiple axes drawn through the joint, rotation occurs only around three axis: spheroidal joint(ball-and-socket joint), art. spheroidea, consists of a globular head and a corresponding concavity. A typical example is the shoulder joint. Variation of the ball-and-socket joint is the cotyloid joint. Its head resides in a deep articular socket, consequently, it is known as the cup-like joint (art. cotylica); plane joint,art. plana, contains two flat surfaces, which can be viewed as sur­faces of a sphere with a large diameter. Because of the small size difference of both articulating surfaces, only slight translations are possible in plane joints (for example, sacroiliac joint).

31. Clinical applications Pathological process can develop in the joints, among which infectious arthritis is the most common (particularly, rheumatic or tuberculous arthritis). Inflammations of the synovial membrane — synovitis and bursitis are also fairly common. Joint deformations, contraction of the synovial cleft, and restriction of movements accompanied by pain syndrome can occur as a consequence of degenerative changes (arthrosis). Traumas can cause various joint dislocations with stretched and ruptured ligaments. Physician of different specialties often have to deal with the diseases of joints.