Joints I
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Joint classifications and movements
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Joints I
- 6. Suture Joint held together with very short, interconnecting fibers, and bone edges interlock. Found only in the skull. Suture line Fibrous connective tissue
- 8. Syndesmosis Joint held together by a ligament. Fibrous tissue can vary in length, but is longer than in sutures. Fibula Tibia Ligament
- 10. Gomphosis “Peg in socket” fibrous joint. Periodontal ligament holds tooth in socket. Socket of alveolar process Root of tooth Periodontal ligament
- 13. Synchondroses Bones united by hyaline cartilage Sternum (manubrium) Epiphyseal plate (temporary hyaline cartilage joint) Joint between first rib and sternum (immovable)
- 15. Symphyses Bones united by fibrocartilage Body of vertebra Fibrocartilaginous intervertebral disc (sandwiched between hyaline cartilage) Pubic symphysis
- 20. Ligament Joint cavity (contains synovial fluid) Articular (hyaline) cartilage Fibrous layer Synovial membrane (secretes synovial fluid) Periosteum Articular capsule
- 23. Acromion of scapula Subacromial bursa Fibrous layer of articular capsule Joint cavity containing synovial fluid Articular cartilage Tendon sheath Synovial membrane Tendon of long head of biceps brachii muscle Fibrous layer Humerus Frontal section through the right shoulder joint
- 24. Bursa rolls and lessens friction. Humerus head rolls medially as arm abducts. Humerus moving Enlargement of slide 23, showing how a bursa eliminates friction where a ligament (or other structure) would rub against a bone
- 33. Gliding Gliding movements at the wrist
- 35. Hyperextension Extension Flexion Angular movements: flexion, extension, and hyperextension of the neck
- 36. Extension Hyperextension Flexion Angular movements: flexion, extension, and hyperextension of the vertebral column
- 37. Flexion Hyperextension Extension Flexion Extension Angular movements: flexion, extension, and hyperextension at the shoulder and knee
- 39. Abduction Adduction Circumduction Angular movements: abduction, adduction, and circumduction of the upper limb at the shoulder
- 41. Rotation Lateral rotation Medial rotation Rotation of the head, neck, and lower limb
- 43. Pronation (radius rotates over ulna) Supination (radius and ulna are parallel) P S Pronation (P) and supination (S)
- 44. Dorsiflexion Plantar flexion Dorsiflexion and plantar flexion
- 47. Protraction of mandible Retraction of mandible Protraction and retraction
- 52. Plane joint Nonaxial movement Metacarpals Carpals Flat articular surfaces Gliding Examples: Intercarpal joints, intertarsal joints, joints between vertebral articular surfaces
- 53. Hinge joint Humerus Cylinder Trough Uniaxial movement Medial/lateral axis Ulna Flexion and extension Examples: Elbow joints, interphalangeal joints
- 54. Pivot joint Uniaxial movement Sleeve (bone and ligament) Vertical axis Ulna Radius Axle (rounded bone) Rotation Examples: Proximal radioulnar joints, atlantoaxial joint
- 55. Condylar joint Phalanges Medial/ lateral axis Oval articular surfaces Biaxial movement Anterior/ posterior axis Meta- carpals Flexion and extension Adduction and abduction Examples: Metacarpophalangeal (knuckle) joints, wrist joints
- 56. Saddle joint Anterior/ posterior axis Metacarpal I Articular surfaces are both concave and convex Biaxial movement Medial/ lateral axis Adduction and abduction Flexion and extension Trapezium Example: Carpometacarpal joints of the thumbs
- 57. Ball-and-socket joint Multiaxial movement Anterior/posterior axis Cup (socket) Medial/lateral axis Scapula Spherical head (ball) Humerus Flexion and extension Adduction and abduction Rotation Examples: Shoulder joints and hip joints Vertical axis
Notas del editor
- The body is adapted to movement, which occurs only at joints where 2 bones connect (articulations). Joints have different structures that determine the direction and distance they can move. Joints always compromise strength to increase mobility (so in other words, the more anatomy that makes up the joint the more stability that it has but the less mobility such as the knee and on the other hand the less anatomy that makes up the joint allows for more mobility but much less stability such as in the shoulder). Joints can be classified by structure such as being bony, fibrous, cartilaginous or synovial.
- Joints can also be divided into functional groups such as: Synarthroses (also known as synarthrotic joint syn means together and arthro means joint), or immovable joints, which are bound together by fibrous or cartilaginous connections and also they may fuse over time. Amphiarthroses (also known as amphiarthrotic joint), or slightly moveable joints have fibrous or cartilaginous connections. Diarthroses (also known as diarthrotic joint), or synovial joints, are freely moveable and are subdivided by their type of motion.
- Sutures are synarthroses where bones are interlocked and bound by dense fibrous connective tissue. Sutures are very strong and the bones will eventually fuse together. Sutures are found only in the skull. At a syndesmosis the bones are connected by ligaments. These are amphiarthrotic joints and can be found between the bones of the forearm (radius and ulna). A gomphosis is a fibrous connection so it is also considered a synarthroses. This joint can be found binding teeth in their sockets by a periodontal ligament.
- Sutures are fibrous joints composed of a thin layer of dense fibrous connective tissue. They are found between and unite the bones of the skull. The bones are united by a thin layer of dense fibrous connective tissue (irregular structure gives them added strength and decreases chances of fractures). Sutures are functionally classified as synarthroses (are immovable), when we are young the joints allow for movement to help during birth and allow for growth but as we get older the bones in the skull will fuse to allow for better protection of the brain.
- In a syndesmosis bones are connected by ligaments, which are bands of fibrous tissue. Fiber length varies, so movement also varies. Shorter fibers offer little to no movement (such as the inferior tibiofibular joint) and longer fibers offer a larger amount of movement (such as the interosseous membrane connecting the radius and ulna).
- The word gomphosis means to bolt together. A gomphosis is a fibrous joint in which a cone-shaped peg fits into a socket. These joints are only found found in articulation of the roots of the teeth with the alveoli (sockets) held in place by the periodontal ligament in the maxillae and mandible.
- A synchondrosis is a rigid cartilaginous bridge between 2 bones such as the epiphyseal cartilage of long bones and the connection between the vertebrosternal ribs and the sternum. Synchondroses are synarthrotic joints. A symphysis can be found where are bones separated by fibrocartilage and are considered amphiarthroses.
- A synchondrosis is a cartilaginous joint in which the connecting material is hyaline cartilage. This type of joint can be found between the first rib and the sternum (manubrium) and also in the epiphyseal plate (a temporary joint since it is eventually replaced by bone when growth ceases) in a long bone before the completion of bone growth.
- A symphysis is a cartilaginous joint in which the connecting material is a broad, flat disc of fibrocartilage. These are found between bodies of the vertebrae in the spinal column and at the pubis symphysis between the anterior surface of hip bones.
- Diarthroses (synovial joints) are found at the ends of long bones, within articular capsules lined with a synovial membrane.
- There is articular cartilage (hyaline) that covers the surfaces of the bones at their point of articulation, but does not bind the bones together. The distinguishing anatomical feature of a diarthrosis is the synovial (joint) cavity, a fluid-filled space that separates the articulating bones. The articular capsule is a sleeve-like articular capsule surrounding the joint, uniting the two bones by forming a sac-like structure that incorporates the ends of each bone. The outer layer of the articular capsule is the fibrous capsule. It is formed of dense irregular connective tissue that blends with the periostea of the two bones and provides flexibility with resistance to dislocation. The inner layer of the articular capsule is the synovial membrane which is composed of synoviocytes, areolar tissue, and adipose tissue.
- Synoviocytes, lining the inside surface of the synovial membrane, secrete synovial fluid into the joint cavity for lubrication of the articular cartilages and the nourishment of the cartilage cells. Synovial fluid (which contains slippery proteoglycans secreted by fibroblasts) has 3 main functions: lubrication, nutrient distribution and shock absorption. In addition to the ligaments formed by thickenings of the fibrous capsule, most synovial joints have accessory ligaments as well. These are not an integral part of the fibrous capsule, though. Extracapsular ligaments lie outside the articular capsule and bridge the two bones. Intracapsular ligaments lie within the articular capsule and bridge the two bones. They are excluded from the joint cavity by wraps of the synovial membrane. These various kinds of accessory ligaments support and strengthen joints (an injury which tears collagen fibers in a ligament is a sprain).
- A synovial joint is a joint in which there is a space between articulating bones and the synovial (joint) cavity is the name of that space. Articular cartilage covers the surface of the articulating bones bust does not bind the bones together. The articular capsule encloses the synovial cavity and unites the articulating bones. The articular capsule is composed of two layers: a fibrous capsule which is the outer layer consisting of dense connective (collagenous) tissue. The fibers are arranged in parallel bundles and are highly adapted to resist recurrent strain the synovial membrane is the inner layer composed of loose connective tissue with elastic fibers and a variable amount of adipose tissue. The synovial membrane secretes synovial fluid which lubricates the joint and provides nourishment for the articular cartilage. (synovial fluid is similar in appearance and consistency to uncooked egg white).
- Cartilages and fat pads cushion the joint. Inside the shoulder and knee joints are pads of fibrocartilage called the articular discs (menisci). These pads lie between the articular bone surfaces in addition to the articular cartilages and are attached to the fibrous capsule by ligaments. They serve to allow the ends of the articulating bones to fit more closely together, give more stability to the joint by giving a better fit between the bones and direct the flow of synovial fluid to areas with greatest friction.
- Bursae are pockets of synovial fluid that cushion areas where tendons or ligaments rub and tendons attach to the muscles around a jointto help support the joint.
- Associated with may synovial joints are synovial membrane-lined, synovial fluid-filled sacs called bursae. Bursae are strategically located between moving parts. In general, they are found between skin and bone, tendon and bone, muscle and bone, ligament and bone, or articular capsule and bone.
- The function of bursae is to reduce the great amounts of friction that are generated between moving parts during various motions.
- Several factors stabilize joints and prevent injury by limiting range of motion including the structure or shape of the articulating bones, strength and tension of the joint ligaments, arrangement and tension of muscles around the joint, apposition of soft parts (example if you bend your arm at the elbow, it can move no further as the anterior surface of the forearm presses against the arm) and hormones (relaxin). An injury to a joint in which articulating surfaces are forced out of position is called a dislocation (luxation). A partial dislocation is a subluxation. Luxation can damage articular cartilage, tear ligaments, or distort the joint capsule.
- All muscles attach to bone or connective tissue at no fewer than two points the origin which attaches to the immovable bone and the insertion which attaches to the movable bone. Muscle contraction causes the insertion to move toward origin. Movements occur along a transverse, frontal, or sagittal plane. Terms to describe the number of planes or axes in which a joint can move are monaxial (1 axis), biaxial (2 axes) and triaxial (3 axes). Three general types of movement include: Linear or gliding motion, where vertical orientation is maintained, but changes its position. 2. Angular motion, where position is maintained, but changes it orientation. (A circular angular motion is called circumduction.) 3. When both position and orientation are maintained, but spins on its axis, this motion is called rotation.
- Plane or gliding joints are usually flat. Only side-to-side and back-and-forth movements are permitted, but twisting and rotation are inhibited at gliding joints, generally because ligaments or adjacent bones restrict the range of movement. Gliding joints are referred to as nonaxial, because it does not move around an axis. Examples: joints between carpal bones, tarsal bones, the sternum and clavicle, and the scapula and clavicle.
- Angular movements are those in which the angle between the articulating bones changes. There are five: Flexion decreases the angle between the two articulating bones Extension increases the angle between the articulating bones Hyperextension continues the extension movement beyond the anatomical position Abduction refers to movement away from the body’s midline Adduction refers to movement towards the body’s midline Rotation movements are movements of a bone in a single plane about its own longitudinal axis. In medial rotation the anterior surface of the bone or extremity rotates towards the midline. Lateral rotation is just the opposite. Circumduction movements are those in which the distal end of the bone moves in a circle while the proximal end remains relatively fixed in position. This is really a combined movement of flexion-extension and abduction-adduction. The shoulder joint and hip joint are capable of circumduction.
- Flexion involves a decrease in the angle between the surfaces of the articulating bones. Examples: bending the head forward (the joint is between the occipital bone and the atlas); bending the elbow; and bending the knee.
- Extension involves an increase in the angle between the surfaces of the articulating bones. It restores a body to its anatomical position after it has been flexed. Examples: head to anatomical position. Straightening the arm after flexion; straightening the leg after flexion.
- Hyperextension is a continuation of extension beyond the anatomical position. Example: bending the head or arm backward.
- Abduction usually means movement of a bone away from the midline of the body(just remember when someone gets abducted they get taken away). Example: moving the arm upward and away from the body until it is held straight out at right angles to the chest. Adduction is usually movement of a part toward the midline of the body (just remember when you add something you put it together). Example: returning the arm to the side after abduction. Circumduction is a combination of flexion, extension, abduction, and adduction. It involves a 360 degree rotation. Example: moving the outstretched arm in a circle to wind up to pitch a ball.
- Circular or rotation movements are movements of a bone in a single plane about its own longitudinal axis. In medial rotation the anterior surface of the bone or extremity rotates towards the midline. Lateral rotation is just the opposite.
- Rotation – Is the turning of a structure around its long axis. Example: rotation of the head, the humerus, or the entire body.
- Special movements are movements that are unique to only one or two joints that do not fit neatly into one of the other categories. Supination is a movement of the forearm in which the palm of the hand is turned anteriorly (anatomical position). Pronation is the movement that turns the palm posteriorly. Dorsiflexion involves bending the ankle in the direction of the dorsum (top) of the foot, as in trying to stand on your heels. Plantar flexion is bending the ankle in the direction of the plantar surface (sole) of the foot, as in standing on your toes.
- Pronation is rotation of the forearm so that the palm faces posteriorly in the relation to the anatomic position. Supination is rotation of the forearm so that the palm faces anteriorly in relation to the anatomic position
- Dorsiflexion involves bending of the foot in the direction of the dorsum (upper surface). Planter flexion involves bending the foot in the direction of the planter surface (sole).
- Inversion is the movement of the sole of the foot inward (medially) so that the soles face each other. Eversion is movement of the sole outward (laterally) so that the soles face away from each other. Protraction is a movement forward on a plane parallel to the ground, as in thrusting the mandible forward. The shoulders can also be protracted. Retraction is the opposite movement.
- Inversion is the movement of the sole of the foot inward (medially) so that the soles face toward each other. Eversion is the movement of the sole outward (laterally) so that the soles face away from each other.
- Protraction is the movement of the mandible or shoulder girdle forward on a plane parallel to the ground. Example: thrusting the jaw outward is protraction of the mandible and bringing your arms forward until the elbows touch requires protraction of the clavicle or shoulder girdle. Retraction is the movement of a protracted part of the body backward on a plane parallel to the ground. Example: pulling the lower jaw back in line with the upper jaw is retraction of the mandible.
- Elevation is an upward movement of a body part, while depression is a downward movement. The mandible and the shoulder do these movements. Opposition is movement of the thumb.
- Elevation is an upward movement of a part of the body. Example: you elevate your mandible when your close your mouth. Depression is a downward movement of a part of the body. Example: you depress your mandible when you open your mouth. (Shoulders can also be elevated and depressed.)
- Opposition is movement of the thumb toward fingers or palm (grasping) Example: when you grasp something
- Synovial joints are classified according to the shape of the adjoining articular surface. They are divided into six subtypes: Plane or Gliding Hinge Pivot Ellipsoidal Saddle Ball-and-Socket
- Plane or gliding joints are usually flat. Only side-to-side and back-and-forth movements are permitted. Twisting and rotation are inhibited at gliding joints, generally because ligaments or adjacent bones restrict the range of movement. Gliding joints are referred to as nonaxial, because it does not move around an axis. Example: joints between carpal bones, tarsal bones, the sternum and clavicle, and the scapula and clavicle.
- Hinge or ginglymus joint is one in which the convex surface of one bone fits into the concave surface of another bone. Movement is usually flexion and extension (motion is similar to that of a hinged door). Movement is primarily in a single plane, and the joint is therefore known as monoaxial or uniaxial. Flexion decreases the angle between articulating bone and extension increases the angle between articulating bones, often to restore a body part to its anatomical position after it has been flexed. Hyperextension is continuation of extension beyond the anatomical position, such as when the head bends backward.
- Pivot or trochoid joint is a rounded, pointed, or conical surface of one bone that articulates within a ring formed partly by another bone and partly by a ligament. The primary movement permitted is rotation, and the joint is therefore monoaxial. Example: joint between the atlas and axis (atlantoaxial [supination and pronation of the palms and rotation of the head from side to side]) and the joint between the proximal ends of the radius and ulna.
- Ellipsoidal or condyloid joint is an oval-shaped condyle of one bone that fits into an elliptical cavity of another bone. Since the joint permits side-to-side and back-and-forth movements, it is biaxial. Example: joint at the wrist between the radius and carpals (when you flex and extend, and abduct and adduct and circumduct the wrist.)
- Saddle or sellaris joint the articular surface of one bone is saddle-shaped and the articular surface of the other bone is shaped like a rider sitting in the saddle. Movement at a saddle joint are side to side and back and forth, thus, the joint is biaxial. Example: joint between the trapezium of the carpus and metacarpal of the thumb.
- Ball-and-socket or spheroid joint consists of a ball-like surface of one bone fitted into a cuplike depression of another bone. Such a joint permits triaxial movement, or movement of three planes of motion: flexion-extension, abduction-adduction, and rotation-circumduction. Example: shoulder joint and coxal (hip) joint.