HUMAN ANATOMY
LECTURE EIGHT
ARTICULATIONS
ARTICULATIONS
(or JOINTS)
Articulation or Joint
• Place where bones (or bones and cartilage) come together
• Can be freely moveable, have limited, or no apparent movement
• Structure is correlated with the movement
Naming
• According to bones or parts involved
eg: temporo-mandibular
• According to only one of articulating bones eg: humoral
• By Latin equivalent of common name eg: cubital
CLASSIFICATION OF JOINTS
Structural - based on major connective tissue that
binds the bones
• Fibrous
• Cartilaginous
• Synovial
Functional - based on degree of motion
• Synarthrosis - non-movable
• Amphiarthrosis - slightly movable
• Diarthrosis - freely movable
FIBROUS JOINTS
• Two bones united by fibrous connective tissue
• Tight - no joint cavity
• Little or no movement
Types:
(1) sutures
(2) syndesmoses
(3) gomphoses
(1) SUTURES – FIBROUS JOINTS
• Synarthrotic joint between bones
of skull
• Periosteum of one bone is
continuous with the other
• In newborns - sutures are quite
wide
• Fontanels - wider membranous
areas in the suture that allow for
change in shape of head during
birth and rapid growth of brain
after birth
(2) SYNDESMOSES – FIBROUS JOINTS
• Bones run parallel to each
other and connected by
ligaments
• Allows for some movement
- amphiarthrosis joint
• eg: radioulnar or between
tibia and fibula
(3) GOMPHOSES – FIBROUS JOINTS
• Pegs that fit into sockets and
held in place by ligaments
• eg: tooth in socket of
maxillae and mandible held
in place by periodontal
ligaments
CARTILAGINOUS JOINTS
•
•
•
•
Two bones united by cartilage
No joint cavity
Allows only slight movement
Some are reinforced by extra collagen fibers - in
areas of extreme stress = fibrocartilage
• Types:
(1) synchondroses
(2) symphosis
(1) SYNCHONDROSES – CARTILAGINOUS
JOINTS
• Hyaline cartilage between
two articulating bones
• Little or no movement synarthroses
• eg: epiphysial plate,
sternocostal
(2) SYMPHYSES – CARTILAGINOUS JOINTS
• Fibrous cartilage between
two bones
• Slightly moveable amiphiarthoses
• eg: symphysis pubis,
between manubrium sternum
and sternum body,
intervertebral discs
SYNOVIAL JOINTS
• Allow widest range of movement - diarthroses
• Contain synovial fluid
• Unite ends of long bones - greater movement of
appendicular skeleton compared to axial skeleton
SYNOVIAL JOINT STRUCTURE
• Articular cartilage - articular
surfaces covered with hyaline to
provide smooth surface
• Joint cavity - filled with synovial
fluid
• Joint capsule - encloses joint cavity
fibrous capsule - dense irregular
connective tissue, continuous with
periosteum, portions thicken to form
ligaments
synovial membrane - lines joint
cavity except over articular cartilage,
produces synovial fluid
Synovial fluid - mixture of
polysaccharides, proteins, fats - very
slippery
- functions: lubrication, nutrient
distribution, shock absorption
ACCESSORY STRUCTURES OF SYNOVIAL
JOINTS
• Bursae - pockets of synovial membrane and fluid that extend from the
joint
- found in areas of friction eg: where a tendon crosses a bone
• Ligaments and tendons - stabilization
• Meniscus/articular discs - fibrocartilage pads between opposing bones
within the joint
• Fat pads - areas of adipose tissue covered by a layer of synovial
membrane
- protect articular cartilage, act as packing material as fill spaces
• Tendon sheath (tubular bursae) - synovial sacs surrounding tendons as
they pass near or over bone
MOVEMENT AT SYNOVIAL JOINTS
• Monoaxial - occurs around one axis
- forward and back
eg: elbow, knee, fingers
• Biaxial - occurs around two axes at right angles to each other
- forward/back and left/right but not rotating
eg: thumb, neck (atlas/axis)
• Triaxial - occurs around several axes
- combination of rotation and angular movement
eg: ankle, shoulder, wrist, hip
PLANE or GLIDING JOINTS
• Two opposed flat surfaces that glide over each other
• Monaxial movement - limited by surrounding structures
(ligaments)
eg: intervertebral, intercarpal, acromioclavicular, sacroiliac
SADDLE JOINTS
• Two saddle-shaped articulating surfaces at right angles to each
other
• Biaxial movement
eg: thumb
HINGE JOINT
• Convex cylinder of bone within a concavity of other bone
• Monaxial movement
eg: elbow, ankle, knee, fingers
PIVOT JOINT
• Cylindrical body of bone that rotates within a ring of bone and
ligament
• Rotation around a single axis
eg: articulation of dens of axis and atlas, proximal radialulnar,
distal radialulnar
BALL AND SOCKET JOINT
• A ball (head) of one bone and a socket of another bone
• Wide range of movement in almost any direction
eg: shoulder, hip
ELLIPSOID JOINT
• Elongated ball and socket joints
• Articular surfaces are elliptical
• Shape of joint limits range of movement - like a hinge
but in two planes (biaxial)
eg: between atlas and axis, between metacarpals and
phalanges
SPECIAL SYNOVIAL JOINTS
ELBOW JOINT
• Compound hinge joint
- humeroulnar joint
- humeroradial joint
• Shape of trochlear notch and
trochlea limit range of movement
• Very stable due to:
- interlocking surfaces
- thick articular capsule
- strong ligaments
• Tendon of biceps brachii muscle
attaches to radius at radial
tuberosity - contraction flexes
elbow joint
GLENOHUMERAL JOINT (SHOULDER)
• Greatest range of motion but
very unstable - ball and socket
• Glenoid labrum - rim of
fibrocartilage built up around
glenoid cavity
• Rotator cuff - 4 muscles that
provide stability to joint
- supraspinatus
- infraspinatus
- subscapularis
- teres minor
• Bursae reduce friction where
muscles and tendons cross the
joint capsule
TEMPOROMANDIBULAR JOINT (TMJ)
• Combination plane and ellipsoid
joint
• Condyle of mandible articulates
with mandibular fossa of temporal
bone
• Fibrocartilage disc
• Ligaments connect to mandible and
temporal bone
ACETABULARFEMORAL JOINT (HIP)
• Acetabulum (socket) articulates
with head of femur (ball)
• Fibrocartilage pad deepens the
acetabulum
• More stable but less mobile than
shoulder
• Extremely strong joint capsule
reinforced by 4 broad ligaments
TIBIOFEMORAL JOINT (KNEE)
• Articulations - medial condyle to medial
condyle, lateral condyle to lateral
condyle, patella to patellar surface of
femur
• Thin and incomplete joint capsule
• Strengthened by ligaments and tendons
• Menisci - fibrocartilage articular discs
that build up margins of the tibia and
deepen the articular surface
• Patella - covers and supports front of
joint
7 major ligaments stabalize knee joint
• Cruciate ligaments - extend between
intercondylar eminence of tibia and fossa
of femur
- Anterior cruciate ligament (ACL)
prevents anterior displacement of tibia
- Posterior cruciate ligament (PCL)
prevents posterior displacement of tibia
• Collateral and popliteal ligaments along with tendons of thigh muscles
strengthen the joint
KNEE INJURIES AND DISORDERS
• Sports injuries - tearing the tibial
collateral ligament, the ACL,
damage to the medial meniscus
• Bursitis - inflammation of bursa
• Chondromalacia - softening of
cartilage due to abnormal
movement of the patella or to
accumulation of fluid in fat pad
posterior to patella
• Hemarthrosis - accute
accumulation of blood in the joint
TALOCRURAL JOINT (ANKLE)
• Highly modified hinge joint
• Lateral and medial thickening of
articular capsule prevents side-toside movement
• Ligaments of the arch
- hold bones in proper relationship
- transfer weight
CLINICAL FOCUS
• Sprain - bones of joint are forcibly pulled apart, surrounding
ligaments are torn or pulled
• Separation - bones remain apart after an injury
• Dislocation - one end of bone is pulled out of the socket
• Arthritis - inflammation of a joint (more than 100 types)
osteoarthritis - wear and tear
rheumatoid - caused by transient infection or autoimmune disease
• Gout - increase in uric acid in the body accumulates as crystals in
joints and tissues