Lecture 6 Movement and Power Functional Classification Joints

Lecture 6 Movement and Power

Functional Classification Joints can be classified by how much motion they allow: • Synarthrosis – does not allow any movement between articulating bones • Amphiarthrosis – allows only a small amount of movement between articulating bones • Diarthrosis – freely moveable, allowing a wide variety of specific movements

Structural Classification Joints can be classified based on their structural features. • Fibrous joints – fastened together by dense regular collagenous connective tissue without a joint space between articulating bones; can be synarthroses or amphiarthroses • Cartilaginous joints – fastened together with cartilage without a joint space; can be synarthroses or amphiarthroses • Synovial joints – diarthrosis joints have a layer of hyaline cartilage on articulating surface of each bone; joint space is a fluid-filled cavity found between articulating bones © 2016 Pearson Education, Inc.

Fibrous Joints • Synarthroses • United by fibrous tissue • Examples: sutures of skull, splint bones of horses

Sutures • Suture – immoveable joint between edges of bones that make up cranium; fully fused sutures are very stable, well suited for protecting brain © 2016 Pearson Education, Inc.

Gomphoses • Gomphosis – immoveable joint between each tooth and its bony socket in jaw; periodontal ligament is a strong fibrous membrane that links tooth firmly to jaw bone

Syndesmoses • Syndesmosis – joint between tibia, fibula, ulna, and radius; bones are joined by an interosseous membrane or ligament composed of dense regular collagenous connective tissue, which allows for small amount of movement

Cartilaginous Joints • Amphiarthroses • Capable of slight rocking movement • Examples: mandibular symphysis, pubic symphysis, intervertebral disks

Intervertebral discs are another symphyses joints. Intervertebral discs have a shape of a tablet. It consist of an outer fibrous coverage called anulus fibrosus and an inner gel -like pulp center called nucleus pulposus. The anulus fibrosus consists of several layers (laminae) of fibrocartilage. The stiff laminae can withstand outside compressive forces. The nucleus pulposus consists of a hyaline cartilage. It prevents the development of stress concentration in vertebral column and acts as a shock absorbing pads.

Synovial Joints Synovial joints have a complex structure. These joints permit different degree movement and are classified as diarthroses. Because movement compromises structural stability, synovial joints usually are accompanied by additional supporting structures outside of the joint, such as ligaments.

Synovial joint has a space between bones called synovial cavity filled with slippery fluid called synovial fluid. Synovial fluid contains protein lubricin secreted by synovial fibroblasts. Fluid reduces friction between bone surfaces. It also contains phagocytes that remove microbes and the debris from the joint. The apical ends of both bones are covered by articular cartilage. Articular cartilage is a hyaline cartilage: a slippery glossy tissue. The articular cartilage together with synovial fluid provides a smooth frictionless movement. Outside joint is covered by the connective tissue membrane called synovial capsule. Synovial capsule encloses ends of adjacent bones and completely covers their surfaces, except the areas covered by the articular cartilage.

The internal surface of the synovial capsule is lined by a synovial membrane. Synovial membrane is made of a special type of connective tissue called synovial tissue. Synovial tissue is composed of vascularized connective tissue that lacks a basement membrane. It has two types of cells called type A and type B. Type A cells are derived from white blood cells monocytes. These cells remove the bacteria and wear-and-tear debris from the synovial fluid. Type B cells produce hyaluronic acid, lubricin, proteinases, and collagenases. Synovial joints are diarthrosis and allow next movements: • Flexion • Extension • Adduction • Abduction • Rotation • Circumduction

Some synovial joints have a fibrocartilage that grows inward from the joint capsule. Sometimes this fibrocartilage completely crosses the entire joint capsule between articulating bones. This fibrocartilage is called articular disc. Articular discs were found inside the temporomandibular joint (TMJ), distal radioulnar joints, sternoclavicular, and acromioclavicular joints. Menisci are fibrocartilage pads that have shape of a flat donut with thick border and thin central region. They do not divide synovial cavity completely. These cartilages absorb shock and pressure, stabilize knee joint, and reduce the chance of dislocation.

Some synovial joints are enforced by so-called intracapsular ligaments. For example, in hip joint ligamentum teres fastens a rounded depression on the head of femur called fovea and depression on the bottom of the acetabulum called acetabular notch. Ligamentum teres prevents hip joint dislocation. The knee joint is stabilized by a set of intracapsular ligaments. A pair of cruciate ligaments: anterior (ACL), also known as a cranial (CCL), and posterior (PCL) bind lateral condyle of the femur with the anterior intercondylar area of the tibia and medial condyle of the femur with the posterior intercondylar area of the tibia correspondingly. The ACL prevents the tibia from being pushed too far anterior relative to the femur. It is often torn during twisting or bending of the knee. The PCL prevents posterior displacement of the tibia relative to the femur. The transverse ligament connects lateral and medial menisci

Structurally, synovial joints fall in six groups: plane or gliding, hinge, pivot, condylar, saddle, and ball-andsocket

Hinge Joints • Ginglymus joints • One joint surface swivels around another • Only capable of flexion and extension • Example: elbow joint

Gliding Joints • Arthrodial joints • Rocking motion of one joint surface on the other • Primarily capable of flexion and extension • Abduction and adduction possible • Example: carpus

Pivot Joints • Trochoid joints • One bone pivots (rotates) on another • Only capable of rotation • Example: the atlantoaxial joint

Ball-and-Socket Joints • Spheroidal joints • Allow for all joint movements • Examples: shoulder and hip joints

Tenacious tendons • Most ligaments and tendons connect into the periosteum • Both ligaments and tendons are made of connective tissue; tendons are much thicker, having both strength and elasticity

Synovial Joint Movements Flexion and Extension • Opposite movements • Increase or decrease the angle between two bones

While we’re on the subject…. • Flexion: reducing the angle between bones • Extension: increasing the angle between bones

Synovial Joint Movements Adduction and Abduction • Opposite movements • Move an extremity toward or away from medial plane

Other Examples – Joint Movements • abduction/adduction • dorsiflexion/plantarflexion • flexion/extension/hyperextension 24 Abduction: moving a limb or part of a limb away from the median plane. We sometimes will also use this term to describe movement of one structure in relation to another. The opposite of abduction is adduction; again, we are describing things relative to the median plane

Synovial Joint Movements Rotation • Twisting movement of a part on its own axis Circumduction • Movement of an extremity so that the distal end moves in a circle

Elevation/depression Moving dorsally, or above the median plane moving ventrally, or below the median plane

Pronation/supination • Pronation is moving the plantar or palmar surface ventrally or toward the ground • Supination is moving the plantar or palmar surface dorsally, or toward the top • In general, supination of the paw is only possible in carnivores and pigs

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