Anatomy: Joints

Synostoses (subtype of sutures...?)

"Bony junctions" Joint type: fibrous, synarthrosis -joints that completely fuse -located b/n metopic suture (in the fetal skull) -epiphyseal line -b/n coccygeal bones = coccyx -fusion: fibrous tissue ossify

Sutures

"Seams'" Joint type: fibrous, synarthrosis -located only between the bones of the skull -dense c.t. articulates bone and is continuous with periosteum -joint is held together with short, very rigid fibers, but allow the skull to expand as brain grows during youth -during middle age, the fibrous tissue ossifies and the skull bones fuse together into a single unit, which are then called synostoses -fibrous: collagen fibers

Hinge Joints

-uniaxial (monoaxial): allows movement in one plane only: flexion and extension -the most common type of synovial joint Examples: -knee joint -elbow joints -interphalangeal joints

Anatomy of Synovial Joints

1. Articular or joint capsule 2. Synovial membrane (synovium) 3. Synovial fluid 4. Articular cartilage 5. Ligaments 6. Menisci (-cus) 7. Bursae

Special Movements

1. Pronation 2. Supination 3. Dorsiflexion 4. Plantar Flexion 5. Inversion 6. Eversion 7. Protraction 8. Retraction 9. Elevation 10.Depression 11. Opposition

Articular/Joint Capsule

A 2-layered capsule that encloses that articular/joint cavity: 1. External fibrous layer -an extension of the periosteum of the bones -composed of dense irregular c.t. -function: strengthens joint so that bones are not pulled apart 2. Inner membrane: synovial membrane

Abduction/Adduction

Abduction -movement of a limb away from the midline or median plane of body, along the frontal plane -i.e. raising arm or thigh laterally, spreading fingers or toes apart -*lateral bending of trunk is lateral flexion, not abduction Adduction -opposite of abduction: movement of limb toward the body midline

Saddle Joint

Biaxial movement: -allows movement in 2 planes: a. flexion/extension b. adduction/abduction Example: -carpometacarpal joints of thumbs

Condylar Joint

Biaxial movement: -allows movement in 2 planes: a. flexion/extension b. adduction/abduction Examples: -metacarpophalangeal (knuckle) joints -wrist joints

Synovial Fluid

Clear, viscous fluid that occupies all free spaces within the joint capsule Composed of: -water -hyaluronic acid -phagocytes: rid the joint cavity of microbes and cellular debris Synthesized and secreted by the synovial membrane Function: -provides lubrication to reduce friction between cartilages

Tendon

Connect muscle to bone -composed of fibrous c.t.

Critical Thinking

Considering the anatomy of a synovial joint and prior knowledge, determine what structure of the synovial joint is involved in each of the following types of arthritis: Gouty arthritis Osteoarthritis Rheumatoid arthritis

Ligament

Cords/ brands that connect bone to bone -composed of fibrous c.t.

Critical Thinking

Crash McBang hurt his knee in an auto accident by ramming it into the dashboard. The doctor tested the knee for ligament damage by having Crash sit on the edge of a table with his knee flexed at a 90-degree angle. The doctor attempted to pull the tibia in an anterior direction (anterior drawer test) and then tried to push the tibia in a posterior direction (the posterior drawer test). No unusual mvmt of the tibia occurred in the anterior drawer test but did occur during the posterior drawer test. Explain the purpose of each test, and tell Crash which ligament he damaged.

Ligaments

Dense regular c.t. bands that connect articulating bones Function: -strengthen and reinforce joints

Dorsiflexion/Plantar flexion

Dorsiflexion: -lifting the foot so that its superior surface approaches the skin -corresponds with wrist extension Plantar flexion: -depressing the foot (pointing the toes) -corresponds to wrist flexion

Elevation/Depression

Elevation: -lifting a body part superiorly -i.e. scapulae are elevated when you shrug your shoulders Depression --moving the elevated part inferiorly -i.e. during chewing, the mandible is alternately elevated and depressed

Movements at Synovial Joints

Every skeletal muscle is attached to bone or other c.t. structures at at least 2 points -muscle's origin is attached to the immovable (or less movable) bone -the insertion end is attached to the movable bone Body movement occurs when muscles contract across joints and their insertion moves toward their origin 3 General types of movement: 1. Gliding 2. Angular Movements 3. Roation

Flexion/Extension

Flexion -bending movement (usually along sagittal plane) that decreases angle of joint -brings articulating bones closer together Extension -reverse of flexion: increases angle between articulating bones -typically straightens a flexed limb or body part -i.e. straightening a flexed neck, body trunk, elbow, or knee Hyperextension -extension movements beyond the anatomical position

Diarthroses

Freely movable joints: greatest mobility -majority of joints (predominate in the limbs-appendicular skeleton) -most complex -synovial joints Examples: -knee joint -hip joint -shoulder joint -elbow joint -jaw joint

Articular Cartilage

Glassy-smooth hyaline cartilage that covers epiphyses (opposing bone surfaces) Function: -cushioning and absorbing compression

Symphyses

Joint type: cartilaginous, amphiarthrosis Fibrocartilage joins articulating bones -fibrocartilage is compressible and resilient, so it acts as a shock absorber and permits limited movement -designed for strength with flexibility Examples: 1. Invertebral joints (disks) 2. Symphysis pubis (of pelvis)

Synchondroses

Joint type: cartilaginous, synarthrosis Hyaline cartilage articulates with bones -almost all are synarthrotic (immovable) Examples: 1. First sternocostal joint: -the immovable joint between costal cartilage of the first rib and the manubrium of the sternum 2. Epiphyseal plate (in long bones of children): -they are temporary joints and eventually become synostoses

Gomphoses

Joint type: fibrous, amphiarthrosis A peg-in-socket fibrous joint Located only between root of tooth and the alveolar processes of the gums and the roots (refers to the way the teeth are embedded in their sockets) Fibrous connection (that articulates the bones) is the periodontal ligament *note: movements are so microscopic that this may also be referred to as a synarthrosis joint

Syndesmoses

Joint type: fibrous, amphiarthrosis Bones are connected exclusively by ligaments -amount of movement allowed depends on the length of the connecting fibers -distal (inferior) tibiofibular joint -allows for pronation and supination -fibrous: dense regular c.t.

Joint Classification

Joints are classified by: 1. Structure-focusing on the material building the bones together and whether or nor a joint cavity is present 2. Function-based on the amount of movement allowed at the joint

Structural Joint Classification

Joints are named according to: a. the type of c.t. that joins bones together b. whether or not a joint cavity is present 1. Fibrous joints -articulating bones united by collagen fibers (of c.t.) -no joint cavity -most are immovable (synarthroses) 3 types: a. sutures (synostoses) b. syndesmoses c. gomphoses 2. Cartilaginous joints -articulating bones are united by cartilage c.t. -no joint cavity -some are immobile (synarthroses), others are slightly moveable (amphiarthroses) 2 types: a. synchondroses b. symphyses 3. Synovial joints -articulating bones are: a. covered with articular cartilage b. separated by a joint cavity c. enclosed within an articular capsule, which is lined with synovial membrane (which produces synovial fluid) -are freely movable (diarthroses) -nearly all joints of the limbs fall into this class

Functional Joint Classification

Joints named according to degree of movement the joint permits: 1. Synarthrosis -Immovable joints (no movement) -found in skull (after birth) -largely restricted to the axial skeleton (b/c more stable) (*in general, the more stable a joint, the less moveable it is) Distance between articulating bon Includes: sutures, synostoses, synchondroses 2. Amphiarthrosis -slightly moveable joints: limited movement between articulating bone -largely restricted to the axial skeleton (b/c more stable) Includes: symphyses, syndesomoses, gomphoses 3. Diarthrosis Freely movable joints: greatest mobility -majority of joints (predominate in the limbs-appendicular skeleton) -most complex Includes: synovial joint -i.e. shoulder

Joints

Joints, or articulations, are areas where bones join other bones -the site where two or more bones meet Include tendons and ligaments -composed of fibrous connective tissue 2 fundamental functions: 1. provide the skeleton with mobility 2. hold the skeleton together (sometimes providing a protective role in the process) Joints are the weakest parts of the skeleton, but their structure resists various forces

Synovial Membrane

Lines the inner surface of articular capsule -composed of loose c.t. Also covers all internal joint surfaces that are not hyaline cartilage Function: synthesizes synovial fluid

Pivot Joints

Monoaxial joint: allows rotation only Example: -proximal radioulnar joint -atlantoaxial joint

Circumduction

Moving a limb so that it describes a cone in space -consists of flexion, abduction, extension, and adduction performed in succession Example: -pitcher winding up to throw a ball is circumducting their arm

Ball and Socket Joint

Multiaxial movement: -flexion and extension -adduction and abduction -rotation Examples: -shoulder joint -hip joint

Protraction/Retraction

Nonangular anterior and posterior movements in a transverse plane Protraction -nonangular anterior movement in transverse plane -i.e. mandible is protracted when your jut out your jaw Retraction -nonangular posterior movement -i.e. mandible is retracted when your bring jaw back from protraction

Range of Motion Allowed by Synovial Joints

Nonaxial movement: slipping only Uniaxial movement: movement in one plane Biaxial movement: movement in two planes Multiaxial movement: movement in or around all three planes of space and axes)

Angular Movements

Occur in any plane of the body -they increase or decrease angle between two bones Include: 1. Flexion 2. Extension 3. Hyperextension 4. Abduction 5. Adduction 6. Circumduction

Gliding Movements

Occurs when one flat (or nearly flat) bone surface glides or slips over another -back and forth, side to side -w/o appreciable angulation or rotation Occurs at: -intercarpal and intertarsal joints -b/n flat articular processes of the vertebrae

Menisci

Pads of fibrocartilage located between epiphyses of articulating bones Function: -cushioning -improves the fit between the two bones that articulate -minimizes wear and tear Located in: -knee joint -jaw joint

Pronation/Supination

Refer to the movement of the radius around the ulna Pronation ("turning forward") -forearm rotates medially and the palm faces posteriorly/inferiorly -this is the forearm's position when we are standing in a relaxed manner -radius and ulna form and 'X' Supination ("turning backward") -rotating the forearm laterally so that palm faces anteriorly/superiorly -in anatomical position, the hand is supinated and the radius and ulna are parallel

Inversion/Eversion

Special movements of the foot Inversion: -sole of foot turns medially Eversion: -sole of foot faces laterally

Bursae

Synovial filled sacs (bags of lubricant) Located in b/n bone prominences, muscles, tendons, ligaments Function: -act as ball bearings to reduce friction during joint activity Bursitis: is inflammation of the bursa, usually due to the reduction in fluid, causing friction Tendon sheath -elongated bursa that wraps completely around a tendon subjected to friction -i.e. in wrist

Types of Synovial Joints

Synovial joints are categorized by types of movements allowed at the joint 1. Planar or gliding joint 2. Hinge joint 3. Pivot joint 4. Condylar joint 5. Saddle joint 6. Ball and socket joint

Synovial Joint: Knee Joint

The largest and most complex joint in the body -single joint cavity -3 joints in one: 1. femoropatellar joint 2. tibiofemoral joint 3. Menisci of the tibia: -lateral meniscus -medial meniscus Major ligaments of knee joint: -fibular collateral ligament (LCL) -tibial collateral ligament (MCL) -patellar ligament -anterior cruciate ligament (ACL) -posterior cruciate ligament (PCL) Major tendons of knee joint -quadriceps tendon

Opposition

The movement occurring at the saddle joint b/n metacarpal I and the trapezium -is the action taken when you touch your thumb to the tips of the other fingers on the same hand Opposition is responsible for the hand to grasp and manipulate objects

Rotation Movements

Turning of a bone around its own long axis -the only movement allowed between the first two cervical vertebrae -common at the hip and shoulder joints Rotation may be directed toward or away from the midline Examples: -medial rotation of thigh: the femur's anterior surface moves toward the median plane of the body -lateral rotation is the opposite

Synovial Joint: Shoulder Joint

a.k.a Glenohumeral joint -the most moveable joint in the body Anatomy: 1. Articular Capsule -loose fitting and shallower as compared to the knee joint 2. Ligaments a. Coracohumeral ligament -extends from coracoid process to greater tubercle b. Glenohumeral ligaments -three ligaments that form part of the articular capsule -extend from glenoid cavity to lesser tubercle and neck of humerus 3. Rotator Cuff -4 muscles and their associated tendons: a. Infraspinatus b. Supraspinatus c. Subscapularis d. Teres minor

Planar or Gliding Joints

a.k.a Plane joint -allows non-axial (gliding) movement in 2 planes -the simplest type of synovial joint Examples: -intercarpals -intertarsals -acromioclavicular -joints between vertebral articular surfaces

Synovial Joint: Hip Joint

a.k.a. Coxal joint Anatomy: 1. Articular Capsule -tight fitting and deeper than the knee and shoulder joint 2. Ligaments a. Iliofemoral ligament: -iliac border of acetabulum to intertrochanteric line b. Ischiofemoral ligament: -ischial border of acetabulum to neck of femur c. Pubofemoral ligament: -pubis border of acetabulum to neck of femur

Muscles of the Rotator Cuff

know their associated tendons -4 muscles and their associated tendons: a. Infraspinatus b. Supraspinatus c. Subscapularis d. Teres minor