10-9b Joint Structure, Function, and Mechanobiology

Question 1

two ways joints are classified

Answer 1

movement potential

mechanical analogy

Question 2

what are the characteristics of synarthrosis and diarthrosis joints? What are the types of each?

Answer 2

Synarthrosis: 
small movement potential
strong dense tissue support
fibrous or cartilaginous
Diarthrosis/synoavial joints:
moderate to extensive movement potential

Question 3

List the seven elements contained in all synovial joints

Answer 3

Articular cartilage

2. Joint capsule
3. Synovial membrane
4. Synovial fluid
5. Ligaments
6. Blood vessels
7. Sensory nerves

Question 4

List the other support elements contained in some synovial joints

Answer 4

Intra-articular discs or menisci 
Peripheral labrum
Fat pads
Bursae
Synovial Plica

Question 5

What are the two ways we describe joints based on movement potential?

Answer 5

synarthroses

diarthroses

Question 6

What are the two types of synarthrosis joints?

Answer 6

fibrous

cartilaginous

Question 7

What is a fibrous joint? Example?

Answer 7

skull
interosseous membrane between radius and ulna (called syndesmosis)
strong tissue with dense collagen that prevents bones from being pulled apart
designed to disperse force

Question 8

What is a fibrous joint? Example?

Answer 8

ex: skull, interosseous membrane between radius and ulna (called syndesmosis)
strong tissue with dense collagen that prevents bones from being pulled apart
designed to disperse force

Question 9

What is a cartilagenous joint? Examples?

Answer 9

ex: pubic symphysis, intervertebral discs
stabilized by flexible fibrocartilage or hyaline cartilage
allow very little movement

Question 10

What is the function of synarthrodial joints?

Answer 10

transfer forces between the bones

Question 11

What is articular cartilage?

Answer 11

Cartilage that covers the articular surface of the bone

Question 12

What is articular cartilage? What is an analogy for it? Is vascularized? innervated?

Answer 12

Cartilage that covers the articular surface of the bone (shiny)
cap of low-friction paint painted on end of bone
stiff
there to protect the end of the bone against forces
no vascularization or innervation

Question 13

what is arthritis

Answer 13

when the articular cartilage starts “chipping,” “cracking,” etc.
OA

Question 14

What is a joint capsule? What are its two layers?

Answer 14

two layers:
dense, fibrous outer layer/envelope
synovial membrane

Question 15

Describe the synovial membrane:

cell layers? what do the cells secrete? analogy?

Answer 15

3-10 cell layers thick
highly specialized
cells that secrete synovial fluid
folded syran wrap inside the joint 
pain generator: highly innervated

Question 16

Describe the synovial membrane:

cell layers? what do the cells secrete? analogy? innervation? What does movement do to it?

Answer 16

3-10 cell layers thick
highly specialized
cells that secrete synovial fluid
folded syran wrap inside the joint 
pain generator: highly innervated
releases synovial fluid

Question 17

Is the joint capsule innervated?

Answer 17

yes, stretch receptors

Question 18

Is the joint capsule innervated?

Answer 18

yes, stretch receptors

Question 19

describe synovial fluid

Answer 19

super slippery/lubricates the joint
helps joint surfaces glide
nourishes the joint/articular cartilage

Question 20

What does OA do to the synovial fluid?

Answer 20

thickens it bc it releases inflammatory cells into the synovium

Question 21

What are ligaments? What do they do? What are the two primary types?

Answer 21

connective tissue that attach between bones
prevent excessive joint movement
capsular and extracapsular

Question 22

What are capsular ligaments? What do they look like? Examples?

Answer 22

distinct thickenings of the joint capsule
broad sheets of fibers
resist movement in multiple planes
ex: mcl of the knee

Question 23

What are extracapsular ligaments?

Answer 23

more chord-like
resist motion in one to two planes
partially or completely separate from the joint capsule
ex. LCL

Question 24

What are blood vessels’ roles in synovial joints?

Answer 24

penetrate the capsule and extend to the junction of the fibrous and synovial layers

Question 25

What are nerve fibers' role in synovial joints?

Answer 25

innervate external and internal capsular layers (pain & proprioception) n. cells within fibrocartilage

Question 26

What are intra-articular discs/menisci? What is their role? Examples?

Answer 26

fibrocartilage structures that have give/are spongy shock absorbers and increase joint congruency > improves stability (provides bowl for joint to sit in/avoids shearing force across articular cartilage) ex. in vertebrae/knee joints

Question 27

What are peripheral labrum? What is their role? Examples? Analogy?

Answer 27

Fibrocartilage structure Extend around the periphery of joint Deepen joints concavity and support capsular attachment rubber washer that surrounds and seals the joint provides stability and deepens the cavity and has suction in shoulder and hip (highly mobile and need extra support)

Question 28

What are fat pads? What is their role? Analogy?

Answer 28

Reinforces capsule & fills in ‘recesses’ in the joint Cushions surfaces to reduce forces Often interposed between fibrous layer & synovial membrane serves as protection/insulation, cushioning against force ex. under patellar tendon to protect it against the tibia

Question 29

What are bursae? What is their role? When are they palpable?

Answer 29

spaces filled with synovial fluid that provide cushion when inflamed, fill up with fluid Extension or outpouching of synovial membrane Filled with synovial fluid Cushions and prevents friction between moving tissue surfaces extra-articular

Question 30

What are synovial plicae? What is their role? What happens when they are inflamed? Why are they folded?

Answer 30

Redundancy or folds in synovial membrane Redundancy is necessary to prevent undue tension during motions can be inflamed > pathological synovial plicae (causes swelling) and causes mechanical block to accommodate mobility/prevent tearing only in knee

Question 31

What is a hinge joint? How many axes of rotation? What is a mechanical example? Biological?

Answer 31

Single axis of rotation Motion occurs perpendicular to axis of rotation hinge humeroulnar joint

Question 32

What is a pivot joint? How many axes of rotation? What is a mechanical example? Biological?

Answer 32

Single axis of rotation Rotation occurs parallel to the axis of rotation humeroradial joint (spin) doorknob

Question 33

What is an ellipsoid joint? What is a mechanical example? Biological?

Answer 33

Two axes of rotation (no spin) One side elongated concave surface & other elongated concave surface Bi-planar motion flexion/extension & abduction/adduction Limits spin motion at joint the wrist one convex and one concave

Question 34

What is a ball and socket joint? What is a mechanical example? Biological?

Answer 34

3 axes of rotation Spherical convex surface & cup like concave socket Allows 3 degrees of freedom for joint angular motion hip and shoulder

Question 35

What is a plane joint? What is a mechanical example? Biological?

Answer 35

Lacks a definitive axis of rotation Sliding and rotation of one surface on the other sliding a book across a table tarsals slide against each other

Question 36

What is a saddle joint? What is a mechanical example? Biological?

Answer 36

2 axes of rotation Perpendicularly oriented convex and concave surfaces Allows ample bi-planar motion but limits spin motion (can't rotate) two concave shapes saddle thumb

Question 37

What is a condyloid joint? What is a mechanical example? Biological?

Answer 37

``` Primarily 2 axes of rotation Spherical convex ball articulates with relatively flat or non-concave surface Motions vary convex ball and flat surface knee ```

Question 38

Does the axis of rotation change? What is this called? What does this mean for the moment arm? mechanical advantage? muscle strength?

Answer 38

yes instantaneous axis of rotation: axis of rotation can be different at different instances of time/it shifts it changes as you move mechanical advantage changes throughout the range of motion muscles are stronger at certain ranges than others ex. knee