### body part:

Joint
* ALL joints have synovial sacs for the lubrication of that joint.
* All joints are painful when moving
  - have a cavity containing a small amount of synovial fluid that allows for movement
* Any joint can become arthritic but it is more common in the hands, knees, hip and spine.
* Many joints have a large range of movement and are called ball and socket joints
  - utilize water as a lubricant and water is involved in the senses of sight and hearing
* Most joints allow bone movement.
* Most joints are mobile, allowing the bones to move
  - part of endoskeletons
  - lock two building parts tightly together
  - move legs
* Some joints allow for movement early in life, becoming rigid as the animal matures
  - are immovable, such as the sutures between the bones of the cranium
* Some joints connect jaws
  - lower jaws.
  * have cartilage in between them, which help to make the movement flexible. Joints are described structurally and functionally
* allow a skeleton to move.
* allow bones to meet and bind together without actually grinding together
  - move relative to each other, and keep the ends of the bones properly aligned
* also become stiff after resting, especially after a night s sleep
  - form in gineous rocks in response to cooling
  - move with particular speeds and in response to applied forces
* are a major source of damping in MT structures.
* are also more prone to fracture due to the loss of bone mass
  - planes of fracture, but where there is no relative movement of the rocks
  - where friction occurs
  - areas of contact between bones that are bridged by connective tissue
  - body parts
  - breaks with movement normal to the plane of the break
  - cigarettes
  - classified both structurally and functionally
  - critical to exercise because joints are moved by the muscles to produce movement
* are fractures in rock that occur with regular spacing
  - rocks along which significant displacement occurs
  - where there has been no displacement
  - which are found regularly repeated in the bedrock
  - geologist jargon for cracks
  - junctions
  - more likely to be damaged if supporting muscles and ligaments are weak
  - natural cracks in rocks
  - often tender, and range of motion is often restricted due to pain
  - one of the most common features in the crust of the earth
* are part of bodies
* are places of weakness in otherwise strong rock
  - where two bones come together
* are points in the body where two bones meet
  - of union between bones
  - red and swollen and extremely sensitive to touch and is aggravated by motion
  - small fractures in rocks
  - splits usually found near the surface of stressed rock
  - spots
* are the areas where bones come together
  - connections made between different parts of a structure
  - place where two bones meet and are held together by the ligaments
  - too large for limbs and cause nerves to be pinched
  - virtually invisible to the human eye
  - warm, swollen, tender, painful, and difficult to move
  - where two bones meet and movement occurs
* attach bones.
* become more stable as muscles generate force to cause joint compression
  - the main sites of chemical and physical weathering
* can be stiff or over-flexible and can lead to osteoarthritis in later life
  - withstand enormous pressure by slowly releasing water from the cartilage
* commonly injected are the shoulder, knee, ankle and small joints of the hand and foot.
* contain discs.
* detach so easily onto clothing or flesh that it seems as if they jump.
* form free space in rock by which other agents of chemical or physical weathering can enter.
* have a poor blood supply, so they grow and heal slowly.
  - hip sockets
  - lobes
  - sections
* lose their mobility and deteriorate from constant wear and pressure.
* maintain their normal range of motion by being moved.
* make movement of the bony skeleton possible.
* occur where different bones meet
* often stiffen after periods of rest, but clear up within seconds or minutes of motion
  - for short durations after periods of rest
* osteoarthritis, rheumatoid arthritis, other arthritides.
* provide pathways for water and thus pathways for chemical weathering attack on rocks.
* require motion to stay healthy.
* specify the relationships among parts, which in turn are composed of subparts and joints.
* tend to be hairline in thickness, whereas faults are thicker
  - involved in a symmetrical pattern
  - become restricted in their range of movements
  - occur under conditions of decreasing stress
* usually occur as sets, with each set made up of joints that are parallel to each other.
+ Joint (geology): Geology
  * Joints push out in various directions, usually vertically. They can have smooth, clean surfaces, or they can be scarred from sliding against another joint. Joints usually occur as sets, with each set made up of joints that are parallel to each other.