BIOMED 10/9b Joint Structure, Function, and Mechanobiology

Question 1

define arthrology

Answer 1

study of the classification, structure, and function of joints

• movement occurs through sequenced rotations around the joints
• joint surfaces transfer and disperse internal and external forces

Question 2

classification of joints

Answer 2

• movement potential (how they move)

- synovial joitns based on mechanical analogy

Question 3

classification of joints based on movement potential

Answer 3

two main ways

1. synarthroses
2. diarthroses

Question 4

synarthroses classification of joints

Answer 4

• allows slight to no movement
• function is to transfer forces between bones
• two different kinds
  1. fibrous
  2. cartilaginous

Question 5

fibrous joint definition

Answer 5

• synarthroses classification
• stabilized by dense connective tissue with high concentration of collagen
• baby’s skull has fibrous tissue between the bones that eventually fissures and comes together as they get older
• forearm (radius and ulna connected by interosseous membrane) syndesmosis is strong tissue with dense collagen that prevents those bones from being pulled apart
• shin

Question 6

purpose of syndesmosis

Answer 6

part of a fibrous joint

has a large surface area to transfer force to the other side that has a large surface area

Question 7

cartilaginous joint

Answer 7

• part of the synarthroses classification
• stabilized by flexible fibrocartilage or hyaline cartilage
• pubic symphysis joins two pubic joints of the pelvis together
• intervertebral discs: as a whole, the spine has a lot of motion because they’re added together, but not as one unit

Question 8

diarthroses definition

Answer 8

• allows moderate to extensive movement

- synovial joints are diarthroses

Question 9

what are the 7 main elements of all synovial joints?

Answer 9

1. articular cartilage
2. joint capsule
3. synovial membrane
4. synovial fluid
5. ligaments
6. blood vessels
7. sensory nerves

Question 10

what are other joint support elements of synovial joints?

Answer 10

1. intra-articular discs or meniscus
2. peripheral labrum
3. fat pads
4. bursae
5. synovial plica

Question 11

what is articular cartilage?

Answer 11

• part of every synovial joint
• cartilage that covers the articular surface of the bone (typically the end)
• like a cap of low friction paint on the end of the bone
• gets chipped down with arthritis
• protects the end of teh bone
• has stiffness that allows for less damage at the end of the bone
• avascular and aneural

Question 12

what is the joint capsule

Answer 12

• part of every synovial joint
• has two main layers
  1. visible = dense fibrous outer layer, innervated, tells about stretch
  2. inner layer = synovial membrane (thin cerand wrap around join and creates synovial fluid); highly innervated with nociceptors and nerve fibers, often a PAIN GENERATOR

Question 13

synovial membrane

Answer 13

• inner layer of the joint capsule
• synovitis is inflammation of the synovium
• 3-10 cell layers thick
• creates synovial fluid
• highly innervated with nociceptors and nerve fibers

Question 14

synovial fluid

Answer 14

• part of every synovial joint
• contains hyalurornan and glycoproteins
• LUBRICATES the joint surfaces
• provides NOURISHMENT to articular cartilage
• as you move, you start to squeeze the fluid out
• with OA, the fluid gets thicker and gets more visocus because other biproducts of inflammation get into the fluid and make it thicker

Question 15

ligaments

Answer 15

• part of every synovial joint
• CT that attaches between joints
• prevent excessive joint movement
• 2 primary types
  1. capsular (thickenings of joint capsule; cover a lot of SA because broad sheet; resist movement in multiple planes bc of wideness)
  2. extracapsular (cordlike structure; partially or completely separate from joint capsule; may resist movement in 1 or 2 planes bc of small SA)

Question 16

blood vessels and synovial joints

Answer 16

• associated with all synovial joints
• penetrate capsule and extend to junction of fibrous and synovial layer
• without BF, no healing

Question 17

sensory nerves and synovial joints

Answer 17

• all synovial joints have sensory nerves

- sensory nerve fibers innervate external and internal capsular layers - pain and proprioception

Question 18

intra-articular discs or meniscus

Answer 18

• not all synovial joints have this
• made of fibrocartilage
• increased joint congruency, improves stability, the more stable, he less play and movement you have at that joint
• provides SHOCK ABSORPTION
• not designed to be sheared, so when it is in the articular cartilage, it helps with lack of shear

Question 19

peripheral labrum

Answer 19

• not all synovial joints have this
• fibrocartilage
• rubber washer that surrounds and SEALS YOUR JOINT
• extend around the periphery of the joint
• deepens joint concavity and support capsular attachment
• typical for highly mobile, ball and socket joints

Question 20

fat pads

Answer 20

• not all synovial joints have this
• reinforce capsule and filles in recesses in the joint
• cushions surfaces to reduce forces

Question 21

bursae

Answer 21

• not all synovial joints have this
• spaces filled with synovial fluid and provide a bit of cushion
• can only feel with palpation when they are inflamed
• when inflamed, they fill with fluid
• extension/outpouch of synovial membrane
• prevents friction

Question 22

synovial plica

Answer 22

• not all synovial joints have this
• folds in the synovial membrane
• redundancy is necessary to prevent or undo tension during motions
• can get thickening or inflammation of the synovial “pleat” and become a mechanical block
• folded because it would tear bery easily if tehre was not any slack and the joint still had mobility

Question 23

different classifications of joints based on mechanical analogy

Answer 23

1. hinge
2. pivot
3. ellipsoid
4. ball and socket
5. plane
6. saddle
7. condyloid

Question 24

hinge joint

Answer 24

• Humero-ulnar joint
• Singe axis of rotation
• Motion occurs perpendicular to axis of rotation

Question 25

pivot joint

Answer 25

• Humero-radius joint
• Spinning
• Rotation occurs parallel to the axis of rotation
• Single axis of rotation

Question 26

ellipsoid joint

Answer 26

• Wrist
• Two axes of rotation
• One side elongated concave surface and other elongated concave surfa
• Bi-planar motion flexion/extension and ab/adduction
• Limits spin motion at joint

Question 27

ball and socket

Answer 27

• 3 axes of rotation
• Spherical convex surface and cup like concave socket
• Allows three degrees of freedom for joint angular motion

Question 28

plane

Answer 28

• Lacks a definitive axis of rotation
• Sliding and rotation of one surface on the other
• Metacarpals
• Tarsals
• Patella

Question 29

saddle joint

Answer 29

• 2 axes of rotation
• Perpendicularly oriented convex and concave surfaces
• Allows ample bi-planar motion but limits spin motion
• Thumb

Question 30

condyloid joint

Answer 30

• Primarily 2 axes of rotation
• Spherical convex ball articulates with relatively flat or non-concave surfaces
• Motions vary based on particular structure
• Flat tibial plateau
• Knee

Question 31

axis of rotation

Answer 31

• fixed

- instantaneous

Question 32

instantaneous axis of rotation

Answer 32

• knee and hip
• changes as the joint position changes
• axis of rotation in joints is rarely fixed
• therefore moment arm changes
• therefore mechanical advantage changes
• thus proving that at different locations, your body has different strengths and different ranges of motion