Lecture 3: Joints: Structure Determines Function

Question 1

joint

Answer 1

a place where articulating bones are linked to each other by ligaments, cartilage, and other tissues that are scientifically classified as connective tissues.

Question 2

synarthrotic joint

Answer 2

one of three functional classifications of joints … a joint which does not move, i.e. between skull plates … “syn-“ means “united” or “with” … “arthi” means “joint”

Question 3

amphiarthrotic joint

Answer 3

one of three functional classifications of joints … a joint which provides a bit of limited movement, i.e., between two vertebrae … “amphi-“ means “both” or “around” … “arthi” means “joint”

Question 4

diarthrotic joint

Answer 4

one of three functional classifications of joints … a joint which provides free movement in at least two directions, i.e., hips … the most complex joints in the body and the most prone to injury and painful dysfunction… “di-“ means “two” … “arthi” means “joint”

Question 5

fibrous joint

Answer 5

one of three structural classifications of joints … found on joints that have little or no
movement, i.e. between skull bones, connecting teeth to jaw, between the ulna and the radius … this joint unites two bones edge to edge, by some type of dense fibrous connective tissue loaded with collagen fibers (which is why they are said to be dense)

Question 6

cartilaginous joint

Answer 6

one of three structural classifications of joints … found on joints that have little or no
movement … this joint unites two bones end to end, by some type of cartilage, a firm, white, flexible tissue, i.e. between the diaphysis and epiphyesis in long bones, between vertabrae and connecting the pelvic bones.

Question 7

growth plate

Answer 7

a joint between bones, technically within a bone, that should not move … if a growth plate is disrupted by injury, the result can alter the growth of that bone

Question 8

synovial joint

Answer 8

one of three structural classifications of joints … the name refers to the types of fluid-producing membranes that line freely moveable joints (but isn’t what makes synovial joints freely movable) … movement is possible from a joint cavity lined by synovial membrane inside a joint capsule … all diarthrotic joints are synovial joints, and all synovial joints are diarthrotic … the most common articulations in the body and the most
commonly injured

Question 9

joint cavity

Answer 9

a space between the two articulating bones filled with synovial fluid and lined by the synovial membrane and is within a joint capsule

Question 10

joint capsule

Answer 10

a collective, structure – envelope-like or sleeve-like – that spans the two articulating bones at a distance from the actual bony joint and surrounds the joint cavity and unites the bones while providing stability and leaving their facing surfaces free to move against each other … thickened in regions by ligaments … may have tendons incorporated into it … incomplete in places, such as where it allows small blood vessels into the joint or allows a small pocket of synovial membrane to protrude as a bursa … contains sensory nerve endings for both pain, but and for the senses of proprioception or kinesthesia, which relay the locations
and movements of our body parts by monitoring joint position and tension
on the capsule structures. Our nervous system uses these signals to help us
balance as we move, but they are also the reason we know where our body
parts are in space without even looking.

Question 11

articular cartilage

Answer 11

the substance that covers the surface of a bone at a synovial joint

Question 12

synovial membrane

Answer 12

composed of a very thin layer of cells that secrete a mucus-like lubricating fluid … nourishes the structures within the joint and removes waste products from the joint’s
tissues

Question 13

avascular

Answer 13

lacking an internal blood supply, i.e. cartilage

Question 14

synovial fluid

Answer 14

a viscous film of lubricant within the synovial joint cavity that aids free movement and nourishes the cartilage in synovial joints

Question 15

HEALTH FACT

Answer 15

motion is beneficial to the cartilage at synovial joints because movement squishes the cartilage while they circulate the synovial fluid around and promotes the release of waste from the cartilage and the uptake of nutrients into it

Question 16

ligaments

Answer 16

strap-like or cord-like (usually) structures that connect bone to bone … contain parallel bundles of collagen fibers for strength and to resist stress in one main direction … reinforce aspects of the diarthrotic joint that need more support, i.e., medial and lateral sides of a hinge joint … restrict movement on the sides where they cross the joint space, helping to ensure that movement occurs only in the intended directions

Question 17

tendons

Answer 17

connect muscle to bone … contain parallel bundles of collagen fibers for strength and to resist stress in one main direction

Question 18

synovial bursa / bursa

Answer 18

a small fluid-filled sac lined by synovial membrane with an inner capillary layer of viscous synovial fluid … provides a cushion between bones and tendons and/or muscles around a joint … helps to reduce friction between the bones and allows free movement … can be between almost any two structures around a joint (bone and tendon, skin and bone, or bone and ligament)… found around most major joints of the body

Question 19

bursitis

Answer 19

the medical term for an inflamed bursa … bursa can be inflamed from infection, injury or just excess pressure.

Question 20

proprioception

Answer 20

a subtle sensory system that helps one perceive the relative positioning of neighboring parts of the body, and the sense of the strength of effort needed for movement … a part of the nervous system located in a synovial joint that monitors joint position and tension on the capsule structures and relays the locations and movements of body parts … provides the ability to perceive the position of a joint without the aid of vision… help for balance and space perception

Question 21

kinesthesia

Answer 21

the awareness of the position and movement of the parts of the body using sensory organs, which are known as proprioceptors, in joints and muscles … a key component in muscle memory and hand-eye coordination

Question 22

exteroception

Answer 22

a subtle sensory system that helps one perceive the outside world

Question 23

interoception

Answer 23

a subtle sensory system that helps one perceive pain, hunger, and the movement of internal organs.

Question 24

Joint movement (concepts rather than definition)

Answer 24

joint directions and degrees of movement are determined by many factors, such as the specific shapes of the two articulating bones where they meet each other, the size of the
muscles in the area, or the amount of body fat in the area … ligaments and joint capsules can be trained to be increasingly more loose or lax by repeatedly stretching those structures over time in a given direction … joints that don’t get moved and stretched can become increasingly less mobile … joint pathologies, such as carpal tunnel of the wrist and some arthritis can be a result of overuse syndrome.