Structure and Function of Joints

our basic types of connective tissue form the structure of joints are

1.Dense irregular connective tissue 2.Articular cartilage 3.Fibrocartilage 4.Bone

The structural classification of Joints include the following

1.Fibrous 2.Cartilaginous 3.Synovial

Special Movements

Lateral flexion Right and Left Rotation Lateral and Medial Excursion Opposition Dorsiflexion and Plantarflexion Inversion and eversion

Types of Fibrous Joints

Sutures, Syndesmosis, Gomphosis

Common Elements of Synovial Joints

Synovial fluid, Articular cartilage, Articular (Joint) Cavity, Articular or Joint capsule, Synovial membrane, Capsular ligaments, Blood vessels, Sensory nerves

an ellipsoid joint

The joint between the occipital condyles and the atlas (atlantooccipital joint) is a(n)

what are 3 main fiber types comprising the connective tissue of joints

Type I collagen fibers Type II collagen fibers Elastin

the syndesmosis

Which of these types of joints are bones united by fibrous connective tissue, with no joint cavity, and with little or no movement?

Categories of Synovial Joints

a. Non-axial Joint - linear in motion such as in the plane joint b. Uniaxial Joint - motion occurs in one axis such as in hinge and pivot joint c. Biaxial Joint - motion occurs in two different axes such as in condyloid and saddle joints d. Multiaxial Joint - motion occurs in all 3 axes such as in ball and socket joint

Muscles function as?

active stabilizers

Ligaments connect to?

bone to bone and maintain a joint's structure, with irregular crossing patterns of collagen fibers

articular cartilage or the joint cavity of synovial joints

do not enter the Blood vessels and nerves

the tendon sheath

is NOT covered with synovial membrane?

a pivot joint called the atlantoaxial joint

is the joint between the dens of the axis and the atlas

Muscles cannot respond as quickly as?

ligaments to external force, but allow a graded and more controlled response

Non-axial Joint

linear in motion such as in the plane joint

Multiaxial Joint

motion occurs in all 3 axes such as in ball and socket joint

Biaxial Joint

motion occurs in two different axes such as in condyloid and saddle joints

Tendons connect to?

muscle to bone and convert muscular force into bony motion, with parallel alignment of collagen fibers

Blood vessels

provide nutrients to the joint

Bony conformation and ligamentous networks provide ?

static stability

Joint immobilization increases?

stiffness and decreases tissue ability to withstand forces

Cells are responsible for

the maintenance and repair of tissues that constitute joints

Capsular ligaments

thickened regions of connective tissue that limit excessive joint motion

Sensory nerves

transmit signals regarding pain and proprioception

Connective Tissues

•All connective tissues supporting the joints of the body are composed of fibers, ground substance, and cells •Most connective tissues serve to bind organs to each other (muscle to bone) •These biologic materials are blended in various proportions on the basis of the joint's mechanical demands

Hinge joint

•Allows motion in only one plane about a single axis of rotation (Uni-axial), similar to the hinge of a door •e.g., the humeroulnar joint (elbow)

Pivot joint

•Allows rotation about a single longitudinal axis of rotation, similar to the rotation of a doorknob •e.g., the proximal radioulnar joint Copyright

Cartilaginous Joints

•Also called Amphiarthrosis or Amphiarthroidal joint •Two adjacent bones are linked by cartilage

Synovial Joint

•Also called Diarthrosis •Articulation that contains a fluid-filled joint cavity between two or more bones •Highly movable joint, found in nearly all joints of the limbs, whose bone ends are separated by a fluid filled cavity

Fibrous Joints

•Also called Synarthrosis or synarthoidal joint •Adjacent bones are bound by collagen fibers (dense connective tissue) that emerge from one bone and penetrate into the other •Mostly immovable

Condyloid joints

•Articulation between a large, rounded, convex member and a relatively shallow concave member •Most often these joints allow 2 degrees of freedom •e.g., tibiofemoral (knee) joint

Ball-and-socket joint

•Articulation between spherical convex surface and cup-like socket •Allows wide ranges of motion in all three planes (Tri-axial ) •e.g., hip joint

Plane joint

•Articulation between two relatively flat bony surfaces •Allows limited amount of motion; may slide and rotate in many different directions •e.g., intercarpal joints of the hand

Syndesmosis

•Bones are joined by ligaments, cords or bands of fibrous tissue •Interosseus membrane between radius and ulna and between tibia and fibula

Articular or Joint capsule

•Connective tissue that surrounds and binds the joint together •Encloses the cavity and retains the fluid •It has an outer fibrous capsule that is continuous with the periosteum of the adjoining bone •It has an inner, cellular synovial membrane

Ellipsoid joint

•Convex elongated surface mated with a concave surface •Allows motion to occur in two planes (Bi-axial) •e.g., radiocarpal (wrist) joint

Articular cartilage

•Covers the facing surfaces of the two bones •Layer of hyaline cartilage usually 2 or 3 mm thick •Dissipates and absorbs compressive forces

Elastin

•Elastic in nature •Resist (tensile) forces but have more "give" when elongated •Can be useful in preventing injury because they allow the tissue to "bend, but not break"

Bone

•Forms primary supporting structure of the body and provides a rigid lever to transmit muscle force to move and stabilize the body •Forms internal levers of musculoskeletal system •Specialized arrangement of type I collagen providing a framework for hard mineral salts

Meniscus

•Found in the knees •Cartilages that extend inward from the left and right but do not entirely cross the joint

Sutures

•Immobile joint formed when the gap between two bones ossifies and they become a single bone (Synostosis) •Closed sutures of the skull in an adult •Sagittal Suture of the skull

Ground substance

•It is a water-saturated matrix that contains collagen and elastin fibers •Composed primarily of glycosaminoglycans (gags), water, and solutes •Allows body fibers to exist in a fluid-filled environment, dispersing repetitive forces

Joints are

•Joints or articulations are sites where two or more bones meet. •Joints or articulations can be classified according to the manner in which the adjacent bones are bound to each other, with corresponding differences in how freely the bones can move.

Articular (Joint) Cavity

•Narrow space that separates the articular cartilage in between the two bones •Contains the synovial fluid

Bursae

•Not strictly part of synovial joint •They are flattened fibrous sacs filled with synovial fluid •Located between adjacent muscles, where a tendon passes over a bone, or between bone and skin •They serve as cushion by reducing friction between structures that rub together such as ligaments, muscles, skin or tendons

Saddle joint

•One concave and one convex surface •Allows extensive motion, primarily in two planes •e.g., carpometacarpal joint of the thumb, sternoclavicular joint

Articular disc

•Present in a few joints, such as the TMJ, sternoclavicular and acromioclavicular joints, and between the ulna and carpal bones •Pad of fribrocartilage that crosses the entire joint

Synovial membrane

•Produces synovial fluid •Composed of fibroblast-like cells that secrete the fluid •It is also populated by microphages that remove the debris from the joint cavity

Fibrocartilage

•Provides support and stabilization to joints •Provides shock absorption by resisting and dispersing compressive and shear forces •Composes the intervertebral discs of the spine and the menisci of the knee •Multidirectional bundles of type I collagen

Articular Cartilage

•Resists and distributes compressive and shear forces transferred through articular surfaces •Covers the ends of articulating bones in synovial joints •High type II collagen fiber content; fibers help anchor the cartilage to bone

Synovial fluid

•Similar to raw egg white in texture (viscous, slippery texture) •Rich in albumin and hyaluronic acid •Provides joint lubrication and nutrition

Synchondrosis

•The bones are bounded by hyaline cartilage •Epiphyseal plates in children formed by the cartilage in between the diaphysis and the epiphysis of a long bone •Attachment of the 1st rib to the sternum by hyaline costal cartilage

Tendon Sheaths

•They are elongated cylindrical bursae that wrap a tendon subject to friction seen especially in the hand and foot. •They allow tendons to move back and forth more freely in such tight spaces as the wrist and foot.

Type I collagen fibers

•Thick, rugged fibers that resist elongation •Compose ligaments, tendons, and fibrous capsules

Type II collagen fibers

•Thinner and less stiff than type I fibers •Provide a flexible woven framework for maintaining the general shape and consistency of structures such as hyaline cartilage.

Symphyses

•Two bones are joined by fibrocartilage •Pubic symphysis: the two pubic bones are joined by a cartilaginous interpubic disc. •Intervertebral discs •Act as a shock absorber and permits a limited amount of movement.

Gomphosis

•Two bony surfaces connect as a peg in a hole •Teeth embedded in the alveolar socket by the periodontal ligament

Cartilage

•Type of connective tissue •Skeletal maturation involves replacement of the cartilage models with bone •In cartilage the fibers are embedded in a firm gel instead of a calcified cement substance. This provides cartilage with flexibility of a firm plastic material, whereas bone has the rigidity of cast iron •No canal system and no blood vessels penetrate the cartilage matrix •Cartilage is AVASCULAR. •It receives its nutrients and oxygen through diffusion •It permits to sustain a great amount of weight when covering the articulating surface of bones •Shock absorbing pads

Movements of synovial joints

•flexion •extension •abduction •adduction •circumduction •rotation •supination and pronation •protraction and retraction •elevation and depression