Joints and Muscles

Joints (articulations) n Where parts of skeleton meet n Allows varying amounts of mobility n Classified by structure or function n Arthrology: study of joints

Classification of Joints n Function: – Synarthroses = no/little movement – Amphiarthroses = slight movement – Diarthroses = great movement

Joints by Functional Classification TypeMovementExample SynarthrosisNone (minimal) Sutures, Teeth, Epiphyseal plates, 1 st rib and costal cart. AmphiarthrosisSlightDistal Tibia/fibula Intervertebral discs Pubic symphysis DiarthrosisGreatGlenohumeral joint Knee joint TMJ

Joint Classification n Structure – Cartilagenous n Synchondrosis: connected by hyaline cartilage n Symphysis: connected by fibrocartilage – Fibrous n Sutures: connected by short strands of dense CT n Syndesmoses: connected by ligaments n Gomphosis: peg in socket w/short ligament – Synovial Page 20 & 23

Joints by Structural Classification StructureTypeExample CartilagenousSynchondrosis Symphysis Epiphyseal plates Intervertebral discs FibrousSutures Syndesmoses Gomphosis Skull Distal Tibia/fibula Teeth in sockets Synovial6 ShapesGlenohumeral joint Knee joint TMJ

Components of SYNOVIAL JOINTS: ( Structural Joint Classification continued) n Articular cartilage: hyaline; covers ends of both bones articulating n Synovial (joint) cavity: space holding synovial fluid n Articular capsule: Made of 2 layers – Fibrous: external, dense CT for strength – Synovial membrane: internal, produces synovial fluid n Synovial fluid: viscous; lubricates and nourishes; contained in capsule and articular cartilages n Reinforcing ligaments: extracapsular/intracapsular n Nerves + vessels: Highly innervated, Highly vascular n Meniscus (some): fibrocartilage; improves the fit of 2 bones to increase stability pg 21

Bursae & Tendon Sheaths n Bursae: flat, fibrous sac w/synovial membrane lining n Tendon Sheaths: elongated bursae that wraps around tendons n 3 Factors in Joint Stability: – Muscle Tone – Ligaments – Fit of Articular Surface pg 671

Shapes of Synovial Joints n Hinge: cylindrical end of 1 bone fits into trough shape of other – Uniaxial movement – (eg) elbow, ankle, interphalangeal n Plane: articular surface in flat plane – Short gliding movement – (eg) intertarsal, articular processes of vertebrae Pg 715 Pg 725

Joint Shapes n Condyloid: egg-shape articular surface + oval concavity – Multiaxial movement – (eg) metacarpophalangeal (knuckle) n Pivot: round end fits into ring of bone + ligament – Uniaxial movement – rotation on long axis – (eg) prox. radius/ulna, atlas/dens pg 753 pg 725

Joint Shapes n Saddle: articular surface both concave + convex – side-to-side, back-forth movement – Multiaxial movement – (eg) carpometacarpal jt of thumb – Pg 664, 753

n Ball + Socket: spherical head + round socket – multiaxial movement – (eg) shoulder, femur pg 534 Joint Shapes

!Muscles! Function: 1) movement 2) maintain posture 3) joint stability 4) generate heat !Muscles!

Muscle Basics to Remember n 3 Types: Skeletal, Cardiac, Smooth n Origin vs. Insertion n Direct vs. Indirect Attachments – direct = right onto bone – indirect = via tendon/aponeurosis n more common n leave bony markings = tubercle, crest, ridge, etc. n Sometimes attach to skin

Special Features of Muscle n Contractibility = cells generate pulling force n Excitibility = nervous impulses travel through muscle plasma membrane to stimulate contraction n Extensibility = after contraction, muscle can be stretched back to original length by opposing muscle action n Elasticity = after being stretched, muscle passively recoils to resume its resting length

Muscle System: uses levers to move objects n How it works: A rigid bar moves on fixed point when a force is applied to it, to move object n Lever = rigid bar = bone n Fulcrum = fixed point = joint n Effort = force applied = muscle contraction n Load = object being moved = bone

Movements of Muscles n Extension: increasing angle between body parts n Flexion: decreasing angle between body parts – Dorsiflexion vs. Plantarflexion – Inversion vs. Eversion n Abduction: moving away from the median plane n Adduction: moving towards the median plane n Rotation: moving around the long axis n Circumduction: moving around in circles

n Elevation: lifting body part superiorly n Depression: moving body part inferiorly n Protraction: Anterior movement n Retraction: Posterior movement n Supination: rotating forearm laterally n Pronation: rotating forearm medially n Opposition: movement of thumb against other fingers Movements of Muscles

Functional Muscle Groups n Agonist = primary mover of a muscle, major response produces particular movement – (eg) biceps brachii is main flexor of forearm n Antagonists = oppose/reverse particular movement, prevent overshooting agonistic motion – (eg) triceps brachii is antagonist to biceps brachii

Functional Muscle Groups n Synergists = muscles work together, adds extra force to agonistic movement, reduce undesirable extra movement – (eg) muscles crossing 2 joints n Fixators = a synergist that holds bone in place to provide stable base for movement – (eg) joint stablilizers

Naming Muscles n Location: (eg) brachialis = arm n Shape: (eg) deltoid = triangle n Relative Size: (eg) minimus, maximus, longus n Direction of Fascicles: (eg) oblique, rectus n Location of Attachment: (eg) brachioradialis n Number of Origins: (eg) biceps, quadriceps n Action: (eg) flexor, adductor, extensor