S1) Bones and Joints

Question 1

What is a joint?

Answer 1

A joint / articulation is a point of contact between neighbouring bones, between cartilage and bones, or between teeth and bones

joint with low range of movement has a higher stability

Question 2

Which factors are affected by the structural characteristics of a specific joint?

Answer 2

• Strength
• Magnitude of movement
• Types of movement

Question 3

What are the three main categories of joints?

Answer 3

fibrous least mobile

synovial most mobile

Question 4

Describe the structure and function of fibrous joints and provide some examples

Answer 4

• Structure: lack a synovial cavity, articulating bones are held very closely together by fibrous connective tissue
• Function: permit little/no movement
• E.g. skull sutures, inferior tibiofibular joint, posterior sacroiliac joint*

Question 5

State the structure and function of cartilaginous joints

Answer 5

• Structure: lack a synovial cavity, articulating bones are tightly connected by cartilage
• Function: permit little/no movement as cartilage acts as a glue holding bones together

primary top left - tertiary bottom right

Question 6

There are two types of cartilaginous joints.

Identify and describe them

Answer 6

• Primary cartilaginous joints: hyaline cartilage connecting tissue e.g. epiphyseal plate
• Secondary cartilaginous joints (symphyses): fibrocartilage disc as connecting tissue e.g. pubic symphysis

Question 7

What are 6 important characteristics of synovial joints?

Answer 7

• Joint cavity
• Articular cartilage
• Articular capsule (two layers)
• Rich blood and nerve supply
• Accessory ligaments (extracapsular & intracapsular)
• highly mobile

Question 8

Identify and describe the two layers of the synovial joint capsule

Answer 8

• Outer fibrous capsule (may have accessory ligaments)
• Inner synovial membrane (secretes lubricating synovial fluid)

Question 9

Identify the 6 different types of synovial joints

Answer 9

ball and socket - max movement

ellipsoid = condyloid

Question 10

Identify and describe the general types of movement that occur at synovial joints

Answer 10

• Gliding movements: articulating surfaces slide across each other
• Angular movements: change in the angle between articulating bones (flexion, extension, abduction, adduction, circumduction)
• Rotation: a bone turns around its own longitudinal axis (medial rotation, lateral rotation)

Question 11

Describe the structure and function of planar joints and provide an example

Answer 11

• Structure: articulating surfaces are flat / slightly curved (non-axial joint)
• Function: gliding movements occur
• E.g. sternoclavicular joint*

Question 12

Describe the structure and function of hinge joints and provide some examples

Answer 12

• Structure: convex surface of one bone fits into the concave surface of another bone (mono-axial joint)
• Function: flexion and extension occur
• E.g. knee joint, elbow joint, ankle joint*

Question 13

Describe the structure and function of pivot joints and provide an example

Answer 13

• Structure: rounded/pointed surface of one bone articulates within a ring formed by another bone and a ligament (mono-axial joint)
• Function: rotation occurs
• E.g. atlanto-axial joint (C1 and C2)*

Question 14

Describe the structure and function of condyloid (ellipsoidal) joints and provide an example

Answer 14

• Structure: oval-shaped condyle of one bone rests against the elliptical cavity of another bone (bi-axial joint)
• Function: flexion, extension, abduction, adduction, circumduction occur
• E.g. wrist joint*

Question 15

Describe the structure and function of saddle joints and provide an example

Answer 15

• Structure: articular surface of one bone is saddle-shaped and articular surface of the other bone resembles the legs of a rider sitting in a saddle (bi-axial)
• Function: movement is less restricted
• E.g. CMCJ between trapezium the base of metacarpal I*

Question 16

Describe the structure and function of ball-and-socket joints and provide two examples

Answer 16

• Structure: ball-like surface of one bone rests against the cuplike depression of another bone (poly-axial)
• Function: flexion, extension, abduction, adduction, circumduction, rotation occur
• E.g. shoulder and hip joints*

Question 17

Identify and describe the 6 special movements which occur only at certain joints

Answer 17

• Elevation&depression – upward and downward movement of the mandible
• Protraction&retraction – mandible or shoulder girdle move forward and backward parallel to the ground
• Inversion&eversion – sole of foot moves medially and laterally
• Dorsiflexion&plantar flexion – bending of the ankle joint
• Supination&pronation – forearm turns anteriorly and posteriorly
• Opposition – movement of the thumb across the palm

Question 18

What are the 5 factors affecting contact and range of motion at synovial joints?

Answer 18

• Structure/shape of the articulating bones
• Strength&tension of the joint ligaments
• Arrangement&tone of muscles around the joint
• Apposition of neighbouring soft tissues
• Disuse of a joint

Question 19

What drives the effects of ageing on joints?

Answer 19

The effects of ageing on joints are variable among individuals and are affected by genetic factors and wear and tear

Question 20

Identify 5 effects of ageing on synovial joints

Answer 20

• Decreased production of synovial fluid
• Thinning of articular cartilage
• Shortening of ligaments
• Decrease in ligamentous flexibility
• Degenerative changes in load-bearing joints

Question 21

Bone function

Answer 21

• support
• protection of organs
• metabolic - regulate calcium and phosphate
• storage for calccium and phosphate ions
• movement
• heamoatopoiesis

Question 23

histology of bone

Answer 23

(collagen adds to tensile strength)

made of several cylinders which keep the shape compact

Question 25

bone features

Answer 25

• muscle attachments - bones have large muscle attachments to keep structure stable and are associated with powerful movement
• grooves - associated with presence of nerves or blood vessels
• dips - where other bones can fit in
• holes - where blood vessels and nerves can pass
• nutrient paramner - allow blood vessels to enter bone and feed

Question 27

blood supply to bones

Answer 27

Question 28

development of synovial joints

Answer 28

1. point where joint will form you see cell death
2. left with a gap between 2 bones
3. some ligaments remain intact

whole bone is surrounded by perichondrium which becomes periostium of bone and fibrous sheath

Question 30

classes of leavers

Answer 30

E = effort applied by muscle

L = load