ANP1111 Lecture 8 2022 Joints PDF

Chapter 8 in the textbook! Classification of Joints: a joint is a site where 2 or more bones meet classified by structure (what holds the joint together? Is there a cavity?) & by function (how much freedom of movement is allowed at that joint?) structurally – 3 types: fibrous...

Chapter 8 in the textbook! Classification of Joints: a joint is a site where 2 or more bones meet classified by structure (what holds the joint together? Is there a cavity?) & by function (how much freedom of movement is allowed at that joint?) structurally – 3 types: fibrous cartilaginous synovial [arthro = joint] functionally – 3 types: synarthroses amphiarthroses diarthroses FIBROUS JOINTS: bones joined by fibrous CT; no joint cavity so very little to no movement at joint Sutures (NO movement): seams only found between bones of skull overlapping or interlocking of 2 bones; junction filled with very short CT fibers Syndesmoses (very LIMITED movment): cord (ligament) or sheet (interosseous membrane) of fibrous CT Gomphoses: (gompho = nail [Greek]) peg-in-socket; only example = tooth in bony socket Fig. 8.1 CARTILAGENOUS JOINTS: bones are united by cartilage (no joint cavity) Synchondroses: areas of growth: eg: epiphyseal plates, between each of 1st 7 ribs & sternum Symphyses: articular surfaces covered with hyaline cartilage - linking plate of fibrocartilage strength with flexibility: eg: pubic symphysis, intervertebral joints Fig. 8.2 6 characteristics: SYNOVIAL JOINTS 1. Articular cartilage: covers opposing bone surfaces cushioning so bone not crushed Fig. 8.3: General 2. Joint cavity: structure of a synovial = synovial cavity; fluid-filled joint 3. Articular capsule: double-layered; outer fibrous layer is dense irregular CT; inner synovial membrane is loose CT and source of synovial fluid 4. Synovial fluid: fills joint cavity; egg-white consistency; reduces friction 5. Reinforcing ligaments: restrict movement of joint and maintain bone-to-bone alignment 6. Nerves & Blood Vessels: nerves sense pain; also monitor joint  Fig. 8.4 Bursae & tendon sheaths Bursae & tendon sheaths: bags of lubricant → reduce friction (1) A bursa is a sac lined with synovial membrane & containing a thin film of synovial fluid; found where ligaments, muscles, skin or muscle tendons overlie & rub against bone (2) A tendon sheath can be thought of as an elongated bursa that wraps around a tendon Factors that influence stability of synovial joints synovial joints allow lots of movement, so not as stable as fibrous or cartilaginous joints 3 factors influence joint stability: (1) articular surfaces: shapes of articular surfaces of many joints do NOT contribute to joint stability deep ball & socket joints have good shape for stability (2) ligaments: more ligaments = more strength ligaments can only stretch ~6% of length before they break - stretched ligaments stay stretched (3) muscle tone: tendons of muscles crossing joints are usually the most important stabilizing factor - kept taut by muscle tone esp: shoulder, knee, arches of foot www.uky.edu/.../110Lab7/ Lab7Images/KneeJoint.jpg Common Joint Injuries Cartilage injuries: usually the knee - because cartilage has no blood supply, it self-repairs very slowly & pieces can break off & interfere with joint function »» arthroscopic surgery Dislocations: bones forced out of their normal positions at a joint; need to be reduced repeat dislocations common because joint capsule & ligaments get stretched Sprains: partially torn ligaments repair themselves (slowly due to poor vascularization) completely torn ligaments require surgery  Movements allowed by Synovial Joints (Fig. 8.5 & 8.6) Can be nonaxial (gliding only), or monoaxial, biaxial, or multiaxial, depending on the joint. Axial refers to the three planes of the body along which movement can occur (coronal, sagittal, transverse). Special movements  Shape of articulating surfaces determines types of movements permitted by these synovial joints (1) plane joint: 2 flat opposing surfaces gliding e.g. intercarpal joints Focus Figure 8.1 (this slide plus the next 5 slides) (2) hinge joint: cylinder into trough – flexion/ extension e.g. elbow  (3) pivot joint : insertion into a ring or sleeve eg: between atlas & dens of axis (4) condylar joint = “knuckle-like”- both articulating surfaces oval → movement possible in two planes (5) Saddle joint – similar to condylar, but saddle shape permits even more freedom of movement (6) Ball-and-socket joint – shoulder joints and hip joints Knee joint Lateral view Figure 8.11 Frontal view Knee joint – flexion, extension, and slight rotation when knee is partially flexed Three joints – femoropatellar, lateral tibiofemoral and medial tibiofemoral Anteriorly, joint capsule is replaced by 3 broad ligaments that are continuous with the quadiceps tendon (patellar ligament plus medial and lateral patellar retinacula). There are 2 intracapsular ligaments (anterior and posterior cruciate), 2 menisci (medial and lateral, attached at the fibrous capsule) and 2 extracapsular ligaments (fibular collateral and tibial collateral). Note the subcutaneous prepatellar bursa.  Tearing of tibial collateral & anterior cruciate ligaments and medial meniscus Knee joint This slide is not to introduce new material, but to show the joint in context of muscle attachments – Note that the cruciate ligaments, while inside the joint capsule, are covered by synovial membrane and therefore are outside the synovial cavity. Elbow joint Lateral view; right elbow Annular Right Elbow - Lateral Right Elbow - Sagittal Annular Hinge joint: - largely through the articulation of the trochlea of the humerus with the trochlear notch on the ulna. The joint is stabilized by collateral ligaments and of note is the annular ligament allowing rotation of the radius during pronation and supination. Right Elbow - Medial Figure 8.9 Shoulder joint Figure 8.8 Glenohumoral joint – the glenoid cavity is broadened slightly by the glenoid labrum (fibrocartilagenous rim) but is still only 1/3rd the size of the head of the humerus. The only ligament of note is the coracohumeral. It is largely the tendons of the rotator cuff muscles that stabilize this joint. Hip joint Deep ball and socket joint. There is an intracapsular ligament that extends from the fovea capitis (ligament of the head of the femur – ligamentum teres) but its function in humans is unclear. Damage to its artery may lead to arthritis of the hip joint. Extracapsular ligaments to note are the iliofemoral, pubofemoral and ischiofemoral. Frontal section; right hip joint Anterior view; Figure 8.10 Posterior view; right hip joint right hip joint Temporomandibular joint * Figure 8.7 Articulation of the mandibular condyle with the mandibular fossa and the articular tubercle of the temporal bone. Stabilized by a lateral ligament. There is an articular disk that divides the synovial cavity into superior and inferior joint cavities. Initial jaw opening is hinged (mandibular condyle within the temporal fossa – inferior joint cavity and inferior surface of the disc) followed by disc sliding.  Figure 8.7 (cont.) There is gliding when the condyle moves from side to side via articulation with the superior joint cavity and the superior surface of the disc. Animation of TMJ movements: Articular eminence in the video = articular tubercle End of Joints!