joints Flashcards
what is a joint
A joint is also called an articulation
Some joints may be lubricated, permitting a range of movements
Other joints may be more fixed or fused
A joint may involve a point of contact between:
two bones.
or bone and cartilage.
or bone and teeth.
what are joint classified in
Joints can be classified according to:
Function: Related to the degree of movement they permit.
Structure: Based on anatomical characteristics.
what are the 3functional processes?
Synarthrosis- A fixed and immovable joint
Articular surfaces are joined by tough fibrous tissue.
The edges may be dovetailed together.
Examples: sutures of the skull, the manubriosternal joint (between the manubrium and body of the sternum), the teeth in the mandible, the 1st sternocostal joints (between the 1st ribs and the sternum)
Amphiarthrosis-Slightly movable.
- A pad of cartilage lies between the bone surfaces, acting as shock absorbers
- A fibrous capsule holds bone and cartilage in place.
- Examples: intervertebral discs in the spine, the symphysis pubis of the pelvis
Diarthrosis-Freely moving joints with synovial fluid in them
- Some movement is restricted by the:
- Shape of the articulating surfaces.
- Ligaments (elastic connective tissue) holding them together.
- Examples: hip, shoulder, knee, ankle, wrist, elbow, temporomandibular joint
what are the 3 structural processes
Fibrous joint
cartilaginous joint
synovial
what is fibrous structural and its 3 processes
Suture
Fibrous joint composed of a thin layer of dense fibrous connective tissue.
Occur between bones of the skull.
The irregular interlocking edges of sutures give them added strength and decrease their chance of fracturing.
A suture is immovable.
Classified functionally as synarthrosis.
examples include Serrate Sutures: margins are serrated like the teeth of a saw, e.g. sagittal suture between the 2 parietal bones.
- Squamous Suture: margin of one bone overlaps that of adjacent bone, e.g. parietal & temporal bones.
- Plane Suture: even, fairly regular margins (lacrimo-maxillary suture).
2 Syndesmosis
- Fibrous joint in which there is a greater distance between the articulating surfaces and more dense irregular connective tissue.
- The joint is held together by ligaments, allowing the joint to have limited movement.
- Classified functionally as an amphiarthrosis.
3 Interosseous membrane
- A substantial sheet of dense irregular connective tissue that binds neighbouring long bones and permits slight movement.
- Classified functionally as an amphiarthrosis.
There are two principal interosseous membrane joints in the human body.
Between the radius and ulna in the forearm.
Between the tibia and fibula in the leg.
what is colinginous and its 2 processes
- Piece of cartilage between the bones, that holds the bones together and makes a joint.
- These joints lack a synovial cavity.
- Little or no movement.
- The articulating bones are tightly connected by either hyaline cartilage or fibrocartilage.
1 Synchondrosis (Primary cartilaginous joints). 2Symphysis (Secondary cartilaginous joints).
1 Synchondrosis
- Connecting material is hyaline cartilage (chondro = cartilage).
- Joint is immovable and strong.
- Some of these joints are temporary in nature – after a certain age the cartilaginous plate is replaced by bone.
- Classified functionally as synarthrosis (no movement).
- The epiphyseal plate that connects the epiphysis and metaphysis of a growing bone.
- When bone elongation ceases, bone replaces the hyaline cartilage.
- The joint between the 1st rib and the sternum, which ossifies during adult life and becomes an immovable bony joint.
2 . Symphysis
-Occurs in the midline of the body.
-Cartilaginous joint in which the ends of the articulating bones are covered with hyaline cartilage but there is also a broad, flat disc of fibro-cartilage between the bones.
-Classified functionally as an amphiarthrosis – a slightly moveable joint.
-symphysis menti in the mandible
pubic symphysis between the anterior surfaces of the hip bones
what is synovial joints
- Incorporates a space between the articulating bones, called a synovial cavity, filled with lubricant synovial fluid .
- Functionally ALL synovial joints are classified as diarthroses - freely movable.
There are some very defined characteristics of synovial joints which make them different from the other 2 types.
These characteristics are responsible for:
Stability.
Movability.
characteristics of synovial joints
articular cartilage and articular capsule
Articular cartilage: the bones are covered by a layer of hyaline cartilage.
Articular capsule: sleeve-like; surrounding a synovial joint; encloses the synovial cavity
articular capsule composed of outer fibrous capsule and inner synovial membrane
Outer fibrous capsule:
Attaches to the periosteum of the articulating bones.
Flexible - permitting considerable movement of a joint.
Great tensile strength (resistance to stretching) which helps prevent the bones from dislocating.
Fibres of some fibrous capsules are arranged as parallel bundles of dense regular connective tissue - highly adapted for resisting strains.
The strengths of these fibre bundles, called ligaments – are the principal mechanical factor that holds the bones together in a synovial joint.
2 Synovial Membrane:
Inner layer composed of areolar connective tissue with elastic fibres.
Can also include accumulations of adipose tissue, called articular fat pads.
“Double jointed” people have no extra joints but greater flexibility in their articular capsules and ligaments - more likely to ‘dislocate’ their joints.
synovial fluid in the synovial membranecharacteristics
- The synovial membrane secretes synovial fluid: a viscous, clear or pale yellow fluid.
- It forms a thin film over the surfaces within the articular capsule.
- Lubricates the joint - reduces friction & absorbs shock.
- Supplies O2 and nutrients, removes CO2 and metabolic wastes from cartilage cells (chondrocytes) within the articular cartilage.
- Phagocytosis - phagocytic cells in the fluid remove microbes and debris (result of wear and tear).
- When immobile the fluid becomes viscous.
- When mobile the fluid becomes less viscous.
- Warm up before exercise!
accessory ligaments of synovial joints
Extracapsular ligaments:
-Lie outside the articular capsule, e.g. fibular and tibial collateral ligaments of the knee joint.
Intracapsular ligaments:
-Occur within the articular capsule but are excluded from the synovial cavity by folds of the synovial membrane, e.g. anterior and posterior cruciate ligaments of the knee joint.
Example: Cruciate ligaments: paired, cross-shaped ligaments, extended from the head of the tibia to the intercondylar notch of the femur.
other joint structures of synovial joints
- Articular discs or menisci:
Pads of fibro-cartilage that lie between the articular surfaces of the bones and are attached to the fibrous capsule.
Act as shock absorbers.
Providing adaptable surfaces for combined movements.
Permit weight distribution over a greater contact surface.
Maintain the stability of the joint
Direct the flow of synovial fluid to the areas of greatest friction.
By modifying the shape of the joint surfaces of the articulating bones, articular discs allow two bones of different shapes to fit together more tightly.
Examples: lateral & medial menisci in the knee joint.
Temporo-mandibular joint (TMJ).
- Bursae:
Sack-like, filled with synovial fluid, have a cushioning effect.
Found between skin and bones, tendon and bones, muscles and bones, or ligament and bones.
Strategically situated to alleviate friction in some joints, e.g. shoulder and knee joints.
Friction is created between moving parts during joint movements. - Tendon Sheaths:
- Tendons connect muscles to bones, acting as attachment points. When muscles contract, tendons convey the muscle force which moves bones
- Tendon sheaths are tube-like bursae, filled with fluid, that wrap around certain tendons that experience considerable friction during muscle contraction.
- They are found where tendons pass through synovial cavities e.g. the tendon of the biceps muscle in the shoulder joint.
- Ligaments:
- Ligaments (elastic connective tissue) help to hold joints together, giving extra strength and stability.
- Consist of fibrous tissue. They often surround a joint capsule, although occasionally, as in the cruciate ligaments of the knee, they may be inside the capsule
- Ligaments connect bones to other bones. They do not connect muscles to bones. That is the job of the tendons.
joints blood supply
Many of the components in a joint are avascular (have no blood vessel supply).
- Arteries in the vicinity send out numerous branches that penetrate the ligaments and articular capsule to deliver oxygen and nutrients.
- Branches from several different arteries merge around a joint before penetrating the articular capsule.
- Veins remove CO2 and waste e.g. from chondrocytes to synovial fluid to blood.
joints nerve supply
- Synovial joints contain many nerve endings that are distributed to the articular capsule and associated ligaments.
- Information about pain is conveyed from the joint to the spinal cord and brain for processing.
- Nerves respond to the degree of movement & stretch at a joint.
- Impulses are sent through different nerves to the muscles to adjust body movements.
types of body movements of joints
Pronation Supination Dorsiflexion Plantar flexion Inversion Eversion
