Anatomy Lecture 3 Arthrology PDF

The skeleton The skeleton The skeleton It is the science dealing with the study of Joints Arthrology is the study of unions (articulation) of two or more bones called joint. An articulation or joint is formed by union of two or more bones or cartilages by other tissue. Without this structure m...

The skeleton The skeleton The skeleton It is the science dealing with the study of Joints Arthrology is the study of unions (articulation) of two or more bones called joint. An articulation or joint is formed by union of two or more bones or cartilages by other tissue. Without this structure movement would not be possible in animal and man. These articulations may be immovable, slightly movable and freely movable. Based on the material that unite them (the uniting medium) joints are classified as follows:  Joints Cartilaginous Fibrous Synovial  I. Fibrous joint (Synarthrosis) are immobile joints united by fibrous tissue. Contain no joint cavity. Most of these joints are temporary, the uniting medium being invaded by the process of ossification with a resulting synostosis.  The classes (types)of fibrous joints are: 1) Suture 2) Syndesmosis 3) Gomphosis 1. Sutures The term suture is applied to those joints in the skull in which the adjacent bones are closely united by fibrous tissue called the sutural ligament. united by fibrous tissue in early life but get ossified with maturity. a) Sutura serrata in which the edges of the bones have irregular interlocking margins, e.g., the interfrontal suture. b) Sutura squamosa The edges of bones are beveled and overlap, forming e.g., the joint between the squamous part of the temporal and the parietal bones. c)Sutura plana (harmonia) in which the edges are plane or slightly roughened, e.g. the internasal suture. d) Sutura foliata The edge of one bone fits into a fissure or recess of an adjacent bone. Where extreme stability is desirable. e.g. wing of presphenoid fits in a fissure of frontal bone. Frontal bone Sphenoid bone Skull, superior view with the top of cranium removed 2. Syndesmosis The uniting medium is white fibrous or elastic tissue or a mixture of the two. Examples are: The union of the shafts of the radius and ulna. The attachments of costal cartilages to each other. Tibia/fibula Radius/ulna 3. Gomphosis: This term is applied to implantation of the teeth in the alveoli. Gomphosis is not, properly considered, a joint at all, since the teeth are not parts of the skeleton.  Gingivitis (gum disease) Bacterial infection destroys the ligament holding the teeth in place Promoted by the presence of plaque  ii. Cartilaginous joints (Ampharthrosis) The bones of cartilaginous joints are united by fibrocartilage or hyaline cartilage, or a combination of the two. The amount and kind of movement are determined by the shape of the joint surfaces and the amount and elasticity of the uniting medium. Two types are recognized under this class 1.Synchondrosis (Hyaline cartilaginous joint) Temporary joints Examples ▪ Epiphyseal plates. ▪ The costochondral junction. ▪ The intermandibular synchondrosis. 2.Symphysis (fibrocartilaginous joints) Temporary joints The uniting medium is fibrocartilage. A limited and variable amount of movement. Examples : The pelvic symphysis The joints between sternebrae of sternum. Joints between the bodies of the vertebrae.  III. Synovial joints Characterized by presence of joint cavity with a synovial membrane in the joint capsule and by their mobility. Movable or true joint This joint may be. Simple joint : joint formed between two bones. E.g. shoulder joint Composite joint : joint formed between more than two bones e.g. carpal joint, elbow joint.:  Necessary structures: 1. Articular surfaces -They are smooth, dense bone. One surface is convex and the other is concave -In certain cases the surface is interrupted by non-articular cavities known as synovial fossae.  Bone Bursa Synovial membrane Joint capsule Articulare Cartilages Joint cavity Tendon Bone Structure of synovial joint 2. Articular cartilage -The articular cartilages, usually hyaline in type, form a covering over the articular surfaces of the bones. -They usually tend to accentuate the curvature of the bone, i.e., on a concave surface the peripheral part is the thickest, while on a convex surface the central part is the thickest. -The articular cartilages are non-vascular, very smooth and have a bluish tinge in the fresh state. -They diminish the effects of concussion and greatly reduce friction. 3. Articular capsule --The articular or joint capsule is, in its simplest form, a tube, the ends of which are attached around the articulating surfaces. -It consists of two layer an external fibrous layer, and an internal synovial layer or membrane. A)- The fibrous layer, is attached either close to the margins of the articular surfaces or at a variable distance from them. -In certain places, it is extremely thick, and sometimes cartilage or bone develops in it; -In other places it is practically absent, the capsule then consisting only of the synovial membrane. -Tendons which pass over a joint may partially take the place of the fibrous layer; in these cases, the deep face of the tendon is covered by the synovial layer. -Parts of the capsule may undergo thickening and so form ligaments which are not separable, except artificially, from the rest of the capsule. B)- The synovial layer (membrane synovialis) lines the joint cavity except where this is bounded by the articular cartilages. -It is a thin membrane and is richly supplied by close networks of vessels and nerves. -It frequently forms folds (plicae synoviales) and villi (villi synoviales), which project into the cavity of the joint. -The synovial membrane secretes a fluid, the synovia, which lubricates the joint; it resembles white of egg, but has a yellowish tinge. It also serves to transport nutrient material to the hyaline articular cartilage. -The chemical composition of synovia is similar to tissue fluid. In addition, it contains albumin, mucin and salts. -. 4. The articular or joint cavity - is enclosed by the synovial membrane and the articular cartilages. Normally it contains only a sufficient amount of synovia to lubricate the joint.  Bone Bursa Synovial membrane Joint capsule Articulare Cartilages Joint cavity Tendon Bone Structure of synovial joint  The synovial fluid or synovia: ▪ lubricate the joint. ▪ helps reduce friction. ▪ absorb shock. ▪ Serves to transport nutrient material to the hyaline cartilage.  Other structures: 1- Ligaments They are strong bands of white fibrous tissue. There are several ligaments that help hold the portions of the joint together. Intracapuslar Ligament: hold the bones together. Not found in every joint. Extracapsular Ligament : called the collateral ligament. It is a single band that is actually a thickening of the joint capsule 2- Articular discs and menisci They are plates of fibrocartilage or dense fibrous tissue situated between the articular cartilages. Divide the joint cavity either partially or completely. Give adaptation to the articular surfaces and give great variety of movement of the joint and diminish concussion 3- Marginal cartilage Is a ring of fibrocartilage which surround the margin of an articular cavity. It enlarge the cavity and tends to prevent fracture of the margin. Movements of the synovial joints 1. Gliding 2. Angular movements A. Flexion B. Extension C. Abduction D. Adduction 3. Circumduction 4. Rotation, Movements of the synovial joints 1- Gliding movement is the simplest kind of motion that can take place and is represented by one surface gliding over another. 2- Angular movements may be flexion and extension or abdunction and adduction. a- Flexion occurs when an angle between two bones is decreased. b- Extension means straightening of a joint which occurs when the angle between the bones is increased. c- Abduction occurs when a part is moved away from the median plane of the body, or if a digit is moved away from the axis of the limb. d- Adduction when the part is moved toward the median plane of the body or the digits toward the median axis of the limb. 3- Circumduction is that form of motion, which occurs when a bone is made to circumscribe a conical space; the base of the cone is described by the distal end of the bone and the apex is the articular cavity. 4- Rotation indicates turning of one segment around the longitudinal axis of the other segment forming the joint. It is seen typically in the atlantoxial joint.  Classification of Synovial joints I. According to the axes of movement 1. Uniaxial the movement occurs around one axis which may be: - transverse axis as in the elbow joint (flexion and extension are the main movements). - Longitudinal axis e.g. atlantoaxial joint (between the first & second cervical vertebrae). - Hinge and trochoid or pivot joints are uniaxial J. 2. Biaxial is the joint in which the movements occur around two horizontal axes at right angles to each other. - In this form of joint, all movements can occur, but no axial rotation. - Condylar, ellipsoid and saddle joints are biaxial joints. 3. Multiaxial is the joint in which the movements occur around many axes and the axial rotation is permitted). - Examples of the multiaxial joint are the shoulder and hip joints. II. According to the form of the articular surfaces: 1-Ball and socket or spheroidal joint (enarthrosis) the articular surface of one bone is spheroid in form (ball) and moves within a socket of the other bone Head of one bone fits into the cup shaped cavity of another bone. E.g. shoulder and Hip joint. Movements : multiaxial, all movements 2- Hinge or ginglymus joint The articular surface is in the form of in which one articular surface is in the form of cylinder received into a corresponding cavity. Uniaxial joint permit movement in one transverse direction. E.g. elbow joint flexion and extension. 3- Trochoid or Pivot joint in which one bone rotates around the longitudinal axis of the other bone forming the joint. It is uniaxial.The axis is longitudinal e.g. atlanto-axial joint 4- Condylar joint in which a condyle or ovoid articular surface is received into elliptical cavity. It is biaxial e.g. knee (stiffle) joint. 5- Ellipsoidal joint in which the circumference of the joint resemble an ellipse. The articulating surface are longer in one direction It is biaxial e.g. radiocarpal joint 6- Saddle joint in which the surfaces are saddle shaped. It is biaxial e.g. interphalangeal joint 7- Plane joint in which the articular surfaces are approximately flat, providing simple gliding or sliding movement. allows slight gliding movement between flat apposed surfaces. e.g. carpal joint, vertebral articular processes.  Bursae: ▪ They are found between the muscle and tendons and the bone/joint. ▪ These are fluid filled sacs that reduce friction. In some cases they are extensions of the synovial sac. ▪ When these bursa become dry, friction and inflammation result, causing BURSITIS.  Clinical importance ▪ Joints are prone to a condition called disarticulation or dislocation ▪ The two articular surfaces get separated ▪ Joints that are prone to disarticulation are: 1. Fore limb :Shoulder joint and elbow joint 2. Hind limb :Hip joint and hock joint  Sprain and Strain Sprain: ligament Strain: Tendon or muscle tear tear  Summary of Joint Classes Structural Characteristics Types Mobility Class Fibrous Bones united by 1. Suture 1. Immobile fibrous tissue 2. Syndesmosis (synarthrosis) 3. gomphosis 2. Slightly moveable (amphiarthrosis) 3. Immobile Cartilaginous Bone ends united by 1. Synchondrosis 1. Immobile cartilage (hyaline) 2. Slightly 2. Symphysis moveable (fibrocartliage) Synovial Bone ends covered 1. Plane Freely moveable with articular 2. Hinge (diarthrosis) which cartilage and 3. Pivot depends on joint enclosed within a 4. Condyloid design capsule lined with a 5. Saddle synovial membrane 6. Ball and socket Thank You