Chapter #8: Joints Flashcards
Joints
(articulations) the site where two bones meet (may or may not allow movement)
What are the general functions of joints?
Mobility & Stability
Mobility
Allow movement of various body parts
Stability
hold the skeleton together (holds bones in place and prevent damage to internal structures)
Which skeleton has more mobility?
Appendicular skeleton
Which skeleton has more stability?
Axial skeleton
Structural Classifications of Joints
Fibrous, cartilaginous, and synovial
Fibrous joints
joints composed of collagen fibers of connective tissue (no joint cavity present; movement allowed with mostly synarthroses and a few amphiarthroses)
Types of fibrous joints
sutures, syndesmoses, and gomphoses
Sutures
Found only between bones of the skull (composed of bundles of very short & strong collagen fibers) and permits very little movement
Why do you want little movement with sutures?
don’t want anything injuring your brain
What happens to sutures over time?
ossifies over time in adults to form syntoses
Syndesmoses
bones are connected to each other only by ligaments (movement allowed by joint depends on the length of the ligament bands)
Ligaments
bands of fibrous tissue that join bone to bone
What is the relationship between length and movement allowed within ligaments?
more length = more movement
Gomphoses
only joint type that does not join bone to another bone (joins tooth to bony alveolar socket)
-fibers of joint are very short, providing very limited movement (exception: braces)
Periodontal Ligament
joins the bone of the mandible/maxilla to the tooth
Cartilaginous Joints
bones joined by cartilage
-no joint cavity
-movement allowed: synathroses & amphiarthroses
Types of cartilaginous joints
Synchondroses & symphyses
Synchondroses
bones unites with a plate of hyaline cartilage
-mostly synathroses
-ex. epiphyseal plate in long bones, costal cartilage
Symphyses
fibrocartilage joins bone
-some movement allowed, but limited (see this with joints that bear a lot of weight)
-ex. intervertebral joints (discs can herniate)
-ex. pubic symphysis
What is the benefit of fibrocartilage at symphyses joints?
Permitting small amount of movement prevents injury
Synovial joints
possesses joint cavity, diarthroses, most joints fall under this category
Why are almost all synovial joints found in the appendicular skeleton?
we need lots of movement
Structures found in synovial joints
articular cartilage, joint cavity, articular capsule, synovial fluid, reinforcing ligaments, innervation & vascularization
Articular Cartilage
hyaline cartilage covering bone ends
What is the function of articular cartilage?
prevents bone from rubbing on bone
Joint cavity
small space between articulating bones
What is the function of a joint cavity?
responsible for temporarily storing synovial fluid
Articular capsule
two-layered capsule that encloses the joint cavity
What two layers make up the articular capsule?
Fibrous layer and synovial membrane
Fibrous layer
outer layer that is continuous with periosteum of bones
What is the function of the fibrous layer?
connects one bone to the bone it joins with; reinforces structure
Synovial membrane
inner layer that lines joint cavity
Where is the synovial membrane NOT found?
never found where articular cartilage is found; never found wrapped around bone ends
What is the function of the synovial membrane?
produce and secrete synovial fluid
Synovial fluid
slippery fluid occupying space in joint capsule & articular cartilages
-when the joint is not active, fluid is viscous
-when the joint is active, fluid thins, becomes watery
What is the function of synovial fluid?
allow joints to slide past one another; prevents articular cartilage from breaking down
Where is the synovial fluid found when the joint is not active?
fluid will soak up into articular cartilage and become thicker
Where is the synovial fluid found when the joint is active?
in the joint cavity
Reinforcing ligaments
bandlike ligaments that join articulating bones (reinforce articular capsule; extend from one bone to joining bone)
What is the function of reinforcing ligaments?
reinforce joint to prevent bones from coming out of place & excessive movement; may limit mobility to an extent
Innervation & Vascularization
Innervation to synovial joints: joints supplied with sensory nerve fibers
Vascularization: rich blood supply to joints, nutrients to synovial fluid
What sensation(s) do we typically perceive at joints?
Stretch, pain, and position
Why is innervation to the joints important?
-sensing overstretch which can lead to injury
-position: you can feel if bones are not lined up properly
-if you ignore stretch and position, you feel pain
Structures that may (or may not) be associated with synovial joints (depends on the joint)
Bursae & tendon sheath
Bursae
flattened sacs that contain a small amount of synovial fluid
Where are you most likely to find bursae?
in between structures that would otherwise rub together
What is the function of bursae?
reduce friction between adjacent structures
Tendon sheath
elongated bursa that wraps completely around a tendon subjected to frequent friction
Where in the body do you typically see tendon sheaths?
found where tendons are packed closely together; avoid rubbing tendons
What is the function of tendon sheaths?
prevents excessive friction for a particular tendon
ex. wrists & ankles have tendon sheaths and if there are not enough tendon sheaths, then tendonitis can occur
Factors influencing joint stability
articular surfaces, ligaments, muscle tone
Articular surfaces
how well do the two articulating bones fit together
Ligaments
the more ligaments, the stronger the joint; reinforcing ligaments however must be joined by other factors
Muscle tone
tendons attach muscle to bone & often wrap around/over joints; this braces the joint and holds it in place; most important because tendons are thicker than ligaments
What is the relationship between mobility and stability?
more mobility = less stability
Types of movements allowed by synovial joints
Nonaxial movement, uniaxial movement, biaxial movement, and multiaxial movement
Nonaxial Movement
-No axis around which movement takes place
-bones that articulate have flat surfaces
-movement allowed: gliding
-Joint shape: plane joint
-ex. intercarpal & intertarsal joints
Uniaxial Movement
-Allows for movement of joint around a single axis
-Movement allowed: flexion, extension, rotation
-joint shape: hinge joint (ex. between humerus & ulna)
-joint shape: pivot joint (ex. between radius & ulna)
Biaxial Movement
-Allows for movement of a joint around two axes
-Movement allowed: flexion/extension AND adduction/ abduction
-joint shape: condylar joint (ex. knuckle of finger)
-joint shape: saddle joint (ex. joint at base of thumb)
Multiaxial Movement
-Allows for movement of a joint around multiple axes
-Movement allowed: flexion/extension, abduction/adduction, AND rotation
-joint shape: ball-and-socket joints (ex. should & hip joints)
Specific Examples of Synovial Joints
TMJ, Glenohumeral joint, elbow joint, coxal joint, knee joint
Temporomandibular Joint (TMJ)
-where the mandible articulates to the temporal bone
-Joint shape: modified hinge joint
-Articular disc divides synovial cavity into superior and inferior portions
-Superior: allows lateral excursion
-Inferior: allows elevation/depression
Glenohumeral (shoulder) Joint
-where the humerus articulates with the scapula
-Most freely moving joint in the body, but still needs some stability:
1) Reinforcing ligaments are very thin and loose
-Coracohumeral ligament & glenohumeral ligaments
2) Rotator cuff
-4 muscles (and their tendons) encircle the joint
3) Glenoid labrum
-Rim of fibrocartilage around glenoid fossa; provides some stability
How does the glenoid labrum provide stability?
serves to slightly deepen sockets
Elbow Joint
-where the humerus articulates with the ulna
- Stability provided by:
1) Close fit of trochlea (on humerus) and trochlear notch (on ulna)
2) Muscle and tendon of arm muscles wrap around elbow to provide further stability
3) Ulnar collateral ligament (medial side) and radial collateral ligament (lateral side) prevent lateral movement
Coxal Joint
-where the head of the femur articulates with the os coxa
-Stability provided by articular surfaces and strong ligaments
-Acetabulum of os coxa has acetabular labrum to further deepen socket
Ligaments of the articular capsule
Iliofemoral ligament, pubofemoral igament, ischiofemoral ligament
-twist and wrap around joints; help brace for standing & walking
Ligamentum teres
ligament of the head of the femur
Knee Joint
single joint cavity shared by 3 separate joints
1) Femoropatellar joint (1): between patella and femur
2) Tibiofemoral joint (2) : between femur and tibia (1 medial, 1 lateral)
-Muscle and tendon reinforces joint with several ligaments
Important Stabilizing Structures in the Knee Joint
Menisci, Extracapsular & capsular ligaments, Intracapsular ligaments
Menisci
thin layer of fibrous cartilage at outer margins of tibiofemoral joints
-Forms ridges along outer margins of joint
Extracapsular & capsular ligaments
prevent hyperextension of knee
Intracapsular ligaments
(cruciate ligaments) secure articulating bones, prevent displacement
-Anterior crulate ligament (ACL)
-Posterior crulate ligament (PCL)
Anterior crulate ligament (ACL)
prevents forward sliding of tibia & prevents hyperextension of knee
-Attaches to anterior portion of tibia
Posterior crulate ligament (PCL)
prevents backward sliding of tibia and forward sliding of femur
-Attaches to posterior portion of tibia
Homeostatic Imbalances of joints
Arthritis
Arthritis
-Can be inflammatory or degenerative
-Most widespread crippling disease in North America
-Can be acute or chronic
-Acute forms: bacterial, inflammatory
-Easily treated with antibiotics
-Chronic forms: inflammatory/degenerative, long-lasting
Types of arthritis
1)Osteoarthritis (OA)
2)Rheumatoid Arthritis (RA)
Osteoarthritis (OA)
-Most common form of chronic arthritis (progresses slowly & is irreversible - treatment but no cure)
-affects females more than males
-affects farmers and long term labor careers
-Caused by: more articular cartilage being destroyed than is replaced
-Effect: exposed bone rubs together, forming bone spurs
-Bone ends deform, which restricts movement at joint
Rheumatoid Arthritis (RA)
-autoimmune chronic inflammatory disorder
-bilateral & degenerative condition (bilateral: if it’s on one side, it’s on the other)
-Joints of fingers, wrist, ankles, feet most likely to be affected
-Individuals with condition have flare-ups followed by periods of remission
-Pain and swelling felt in joints affected by RA during flare-ups
-During periods of remission; no pain/swelling in joints affected by RA
Progression of Rheumatoid Arthritis
1) Synovial membrane becomes inflamed
2) Lymphocytes and macrophages flood area to destroy cause of inflammation
-Macrophages also destroy some of synovial membrane
3) Synovial fluid accumulates and a pannus forms
-Pannus is a thickening of synovial membrane
-Pannus breaks down cartilage tissue over time
-Ankylosis can occur due to cartilage destruction
-Bones fuse together where cartilage/joints used to be
