Joints

Question 1

what is the definition of a joint

Answer 1

The union between two bones, but joints do not necessarily imply movement as some are specialised to permit little or no movement

Question 2

how are bones classified

Answer 2

based on the way in which the bones are held togetehr

Question 3

what are the three groups of joints

Answer 3

fibrous
cartilaginous
synovial

Question 4

what is a fibrous joint and what are the three types

Answer 4

united by collage

• sutures
• syndesmosis
• gomphosis

Question 5

what is a cartilaginous joint and what are the two types

Answer 5

united by cartilage

• synchondroses or primary cartilaginous joints
• symphysis or secondary cartilaginous joints

Question 6

what do synovial joints do

Answer 6

unite the skeletal elements by fibrous capsule which is fluid filled

Question 7

fibrous joints : sutures

where are they found

Answer 7

found only between skull bones

Question 8

fibrous joints : sutures

structure in the foetal skull

Answer 8

• sutures are wide and the bones present smooth opposing surfaces
• this allows a slight degree of movement between the skull bones during the passage of the head through the birth canal

Question 9

fibrous joints : sutures

structure after birth

Answer 9

• sutures become quite rigid
• allowing no movement between the articulating bones
• sutures develop into one of three types
• as time goes on sutures lock together begin to ossify and fuse and disappear

Question 10

fibrous joints : sutures

types of sutures after birth

Answer 10

squamous
serrated
denticulate

Question 11

fibrous joints : syndesmosis

structure

Answer 11

two bony components are slightly apart, united by an interosseous membrane and a little movement is permitted between them
e.g. in between radius and ulna

Question 12

fibrous joints : gomphoses

structure

Answer 12

has the form of a peg in socket i.e. the root of a tooth in the jaw
- fibrous tissue is arranged as the periodontal ligament

Question 13

cartilaginous joints : symphyses

structure

Answer 13

partially moveable joint in which the apposing surfaces are covered by hyaline cartilage but separated by intervening fibrous tissue or fibrocartilage.

Question 14

cartilaginous joints : symphyses

where are they found

Answer 14

in midline of body

e.g. sternum and vertebrae, between two halves of the pelvis

Question 15

cartilaginous joints : synchondroses

where do these joints develop

Answer 15

between bones of endochondral origin

Question 16

cartilaginous joints : synchondroses

structure

Answer 16

solid plate of hyaline cartilage between apposing surfaces. The cartilage plate acts as an epiphyseal plate between primary and secondary ossification centres of long bones and therefore provides an area for growth

Question 17

synovial joints : four basic features

and 2 features that are sometimes present

Answer 17

1. ends of bones are covered by hyaline cartilage
2. the presence of a joint cavity
3. a joint capsule
4. a synovial membrane
5. (disc)
6. (bursae)

Question 18

synovial joints : why is bone not suitable for forming apposing surfaces

Answer 18

• its rigidity means that the forces are transmitted over a small area of contact and thereby generating enormous pressures

Question 19

synovial joints : why is cartilage a suitable surface for forming apposing surfaces

Answer 19

• tough, but deformable and surface adapts under pressure

- its elastic properties allow it to regain its original form when the pressure is removed

Question 20

synovial joints : joint cavity

Answer 20

the ends of the bones are separated by a joint cavity which is not large and contains a small amount of synovial fluid

Question 21

synovial joints : what is the structure of the joint capsule

Answer 21

• joint capsule surrounds joint like a sleeve completely enclosing it
• consists of bundles of collagen fibres
• may vary in tautness and thickness
• thickenings of capsule are called ligaments

Question 22

synovial joints : where is the synovial membrane

Answer 22

• capsule is lined by a synovial membrane but not the articular surfaces and has a rich capillary network

Question 23

synovial joints : what does the synovial membrane contain and what are its properties

Answer 23

• membrane capable of both secretion and absorption of fluid

- viscosity of fluid changes with the speed of joint movement becoming thinner as the speed increases

Question 24

synovial joints : what are discs and where are they found

Answer 24

• may be interposed between articular surfaces thus dividing joint into two cavities and thereby increasing the range of movements possible at a joint
• discs may also increase the congruency of the joint and to help spread the load over the joint

Question 25

synovial joints : what are bursae and where are they found

Answer 25

- sacs filled with synovial fluid - most bursae are found close to the joint and may have continuous synovial membranes - occur in places where structures which move relative to each other are in close apposition

Question 26

synovial joints : how are synovial joints classified

Answer 26

shape of joint surfaces or movements which take place at the joint

Question 27

types of joints

Answer 27

``` ball & socket condyloid - knuckles hinge - elbow plane ellipsoid in foot saddle - shaped - base of thumb pivot - allows head to turn ```

Question 28

movements - what is the simplest movement

Answer 28

gliding - two surfaces slide past eachother

Question 29

other movements occur in pairs of opposites - what are they

Answer 29

angular or rotationary

Question 30

angular movements

Answer 30

flexion and extension | abduction and adduction

Question 31

what is flexion

Answer 31

decreases angle at joint

Question 32

what is extension

Answer 32

inc angle at joint

Question 33

what is abduction

Answer 33

to move away from the midline

Question 34

what is adduction

Answer 34

to move towards the midline

Question 35

rotational movements

Answer 35

external (lateral) and internal (medial)

Question 36

what is external

Answer 36

to turn away from midline

Question 37

what is internal

Answer 37

to turn towards midline

Question 38

special terms that apply to specific joint

Answer 38

pronation - to turn the palmar surface of the hand to face posteriorly supination -to turn the palmar surface of the hand to face anteriorly inversion - to turn plantar surface of the foot medially eversion - to turn plantar surface of the foot laterally

Question 39

what are joints that only have one axis of rotation called?

Answer 39

uniaxial

Question 40

in smaller joints movement is possible in all directions what are they referred to as

Answer 40

non axial

Question 41

what features is movement at synovial joint related to

Answer 41

1. shape of articulations 2. the tension of the joint capsule 3. the position of ligaments 4. the position of the muscle surrounding the joint

Question 42

the temporomandibular joint : shape of articulation

Answer 42

- condyle of the mandible is roller shaped and fits into the fossa in the temporal bone - fossa is surrounded by a bar of bone except anteriorly

Question 43

the temporomandibular joint : joint capsule

Answer 43

has a loose capsule attached to the margins of the articular area

Question 44

the temporomandibular joint : ligaments

Answer 44

the lateral ligament is a thickening of the joint capsule | - two accessory ligaments

Question 45

the temporomandibular joint : muscles

Answer 45

4 major pairs of muscles which move the joint | - muscles form a rotator cuff around the joint and confer dynamic stability to the joint

Question 46

what is the movement in fibrous joints

Answer 46

sutures - none syndesmosis - little gomphoses - shock absorbing

Question 47

what is the movement in cartilaginous joints

Answer 47

synchondroses - none | symphysis - little

Question 48

what is the movement in synovial joints

Answer 48

allow a lot of movement