Articulations, Joint Movements, and Bone Markings
Articulations, Joint Movements, and Bone Markings
Articulations
Definition: Joints where bone meets bone.
Classification:
Structural Classes:
Fibrous:
Description: Fibrous connective tissue binds articulating bones.
Cartilaginous:
Description: Cartilage binds bones together.
Synovial:
Description: Synovial cavity present with ligaments assisting movements.
Functional Classes (based on degree of movement):
Synarthroses:
Description: Immovable joints.
Characteristics: Bones in close contact, separated by a thin layer of fibrous connective tissue.
Example: Sutures in the skull.
Amphiarthroses:
Description: Slightly movable joints.
Characteristics: Bones connected by hyaline cartilage or fibrocartilage.
Examples:
Ribs to sternum connected via hyaline cartilage.
Symphysis pubis bones connected with fibrocartilage, vertebrae, and intervertebral discs.
Diarthroses:
Description: Freely movable joints; most common in the body.
Characteristics:
Bones have articular cartilage surrounding them.
Separated by a joint cavity and surrounded by a capsule with ligaments holding bones together in the outer layer.
Synovial fluid made by the synovial membrane (inner membrane of the capsule).
Synovial Joints
Components:
Synovial membrane
Articular cartilage
Fibrous joint capsule
Joint cavity filled with synovial fluid
Ligaments
Diarthroses Subtypes
Hinge Joints:
Description: Spool-shaped surface fits into concave surface.
Movement: In one plane about a single axis, like a hinged door.
Examples: Elbow, knee, ankle, and interphalangeal joints.
Pivot Joints:
Description: Arch-shaped surface rotates about rounded or peg-like pivot.
Movement: Rotation.
Example: Joint between axis and atlas (C1 and C2 vertebrae).
Ball and Socket Joints:
Description: Ball-shaped head fits into concave socket.
Movement: Widest range of movements.
Examples: Shoulder joint and hip joint.
Condyloid (Ellipsoidal) Joints:
Description: Oval-shaped condyle fits into an elliptical cavity.
Movement: In two planes at right angles to each other.
Example: Wrist joint (between radius and carpals).
Saddle Joints:
Description: Saddle-shaped bone fits into a socket that is curved in the opposite direction.
Movement: Same kinds of movement as condyloid joint but freer; resembles rider in saddle.
Example: Thumb joint (between first metacarpal and carpal - trapezium).
Gliding Joints:
Description: Articulating surfaces are usually flat.
Movement: Gliding - a nonaxial movement.
Examples: Between carpal bones; between sacrum and ilium (sacroiliac joints).
Joint Movements
Description: Skeletal muscles allow movements to take place at diarthrotic joints.
Usually, the muscle is attached to an immovable part on one side of the joint and to a movable part on the other side.
Muscle contraction pulls on the movable part, and movement occurs at the joint.
Action Types
Antagonistic Actions:
Flexion: Decreasing the angle between two bones.
Extension: Increasing the angle between two bones.
Abduction: Movement of a body part away from the midline.
Adduction: Movement of a body part toward the midline.
Medial Rotation: Turning of a bone on its own axis toward the midline of the body.
Lateral Rotation: Turning of a bone on its own axis away from the midline of the body.
Supination: Placing the palm of the hand in anatomical position.
Pronation: Placing the palm opposite to anatomical position (toward back).
Elevation: Raising of a body part.
Depression: Lowering of a body part.
Protraction: Thrusting forward of a body part.
Retraction: Withdrawal of a body part.
Dorsiflexion: Bending of the foot toward the shin.
Plantar Flexion: Bending of the foot away from the shin.
Inversion: Rotation of the sole of the foot inward.
Eversion: Rotation of the sole of the foot outward.
Angular Movements
Flexion and Extension:
Notable movements of the shoulder and knees.
Illustration of angular movements of the neck and vertebral column (flexion and extension represented).
Circular Movements
Rotation and Circumduction:
Movements at the shoulder and hip providing a broad range of motion.
Bone Markings
Definition: Bones have markings and features that are products of what they do and the forces to which they have been subjected.
Classes of Bone Markings:
Articulations:
Description: Where two bone surfaces come together, usually conforming to one another (i.e., one rounded, the other cupped).
Projections:
Description: Areas of bone that project above the surface.
Function: Attachment point for tendons and ligaments.
Characteristics: Size and shape indicative of forces exerted through the attachment to bone.
Holes:
Description: Openings or grooves that allow blood vessels and nerves to enter the bone.
Characteristics: Size and shape reflect the size of vessels and nerves penetrating the bone at those points.
Examples of Bone Markings
Articulations:
Description: Where two bones meet.
Example: Knee joint.
Prominent Rounded Surfaces:
Head:
Example: Head of femur.
Facet:
Example: Vertebrae.
Condyloid:
Example: Occipital condyles.
Raised Markings:
Spinous Process:
Example: Spinous process of the vertebrae.
Protuberance:
Example: Chin.
Process:
Example: Transverse process of vertebrae.
Spine:
Example: Ischial spine.
Tubercle:
Example: Tubercle of humerus.
Tuberosity:
Example: Deltoid tuberosity.
Line:
Example: Temporal lines of parietal bones.
Crest:
Example: Iliac crest.
Holes and Depressions:
Foramen: Holes where blood vessels can pass, e.g., Foramen magnum in occipital bone.
Fossa: Elongated basin, e.g., Mandibular fossa.
Fovea: Small pit, e.g., Fovea capitis on head of femur.
Sulcus: Groove, e.g., Sigmoid sulcus of temporal bones.
Canal: Passage in bone, e.g., Auditory canal.
Fissure: Slit through bone, e.g., Auricular fissure.
Meatus: Opening into canal, e.g., External auditory meatus.
Sinus: Air-filled space in bone, e.g., Nasal sinus.