Arthrology Introduction

Question 1

Define ‘joint’

Answer 1

A joint is defined as a place where two or more bones meet or articulate.

Question 2

Where are joints formed in long bones?

Answer 2

In long bones the ends are the parts which form the joints;.

Question 3

Where are joints formed in short bones?

Answer 3

Various parts of the surface

Question 4

Where are joints formed in flat bones?

Answer 4

At the edges

Question 5

What is the nature of the joint dependent on?

Answer 5

The amount of movement permitted or required between two bones .

Question 6

Define ‘arthrology’

Answer 6

The study of the structure and function of the joints in the body.

Question 7

What are the 3 classifications of joints?

Answer 7

Fibrous
Cartilagenous
Synovial

Question 8

Describe the structure of a fibrous joint

Answer 8

Bones are srongly connected by fibrous tissue with no joint cavity and little movement occurring between bones.

Question 9

Describe the structure of a cartilagenous joint

Answer 9

Bones are strongly connected by cartilage with no joint cavity, some movement occurs between bones.

Question 10

Describe the structure of a synovial joint

Answer 10

Bones are in contact with one another, but are connected by a specialised fibrous tissue in the form of capsule and ligaments.
Between the bones there is a joint cavity which allows varying degrees of movement.
The most common type of joint.

Question 11

What are the 3 types of fibrous joints

Answer 11

Sutures
Gomphosis
Syndesmoses

Question 12

Describe the structure and location of sutures

Answer 12

Sutures are found only in the skull where the margins of the bones articulate with each other.
They are strongly reinforced by fibrous tissue in the form of a sutural ligament. As a result, there is no appreciable movement at a fibrous joint.

Question 13

Describe the structure and location of gomphosis

Answer 13

Gomphosis are special fibrous articulations restricted to the fixation of the teeth into the mandible and maxilla.

Question 14

Describe the structure and location of syndesmoses

Answer 14

Syndesmoses are rare in mammals and the only true example of this type of articulation is the inferior tibiofibular joint.

Question 15

What are the 2 types of cartaligenous joints

Answer 15

Synchondroses (primary cartilaginous joints)
Symphyses (secondary cartilaginous joints)

Question 16

Describe the structure and function of synchondroses

Answer 16

These joints are held together by a plate of hyaline cartilage. These are temporary joints designed to allow growth of bones but not movement
Joints at the growth plates of long bones fall into this category and are gradually ossified when growth is complete.

Question 17

Describe the structure and function of symphyses

Answer 17

The secondary cartilaginous joints or symphyses are all in the midline of the body. The articular surfaces are covered by hyaline cartilage and the bones are held together bya plate of fibrocartilage. The bones are also united by ligaments which fuse with the
fibrocartilage at the periphery and provide additional, flexible linkage.
A symphysis joint allows a limited degree of movement due to the compressibility of the
Fibrocartilage and the degree of leverage available.

Question 18

Describe the features of synovial joints

Answer 18

The bony surfaces of the joint are in contact but not continuity and are normally covered by a glassy, friction free substance known as articular hyaline cartilage.

Question 19

Describe the function of hyaline cartilage

Answer 19

The function of hyaline articular is to provide a wear resistant, low friction and lubricated surface which has both compressibility and elastici ty and is able to accommodate the forces of compression and shearing that human movement creates. Hyaline cartilage is one of the most resilient substances in the human body.

Question 20

How thick is articular hyaline cartilage?

Answer 20

The thickness of the cartilage varies with the shape of the surface and the area of the
body. In large joints, such as the hip, articular cartilage can be almost 1cm thick! Whereas
it may only be 1mm thick in joints of the fingers, for example.

Question 21

What is a joint cavity?

Answer 21

The space between the bones.

Question 22

What is synovial fluid?

Answer 22

Viscous pale yellow fluid in the joint cavity. Only present in small amouts even in large joints

Question 23

Give functions of synovial fluid

Answer 23

• As a source of nutrition for the articular cartilage
• As a lubricant to increase joint efficiency and reduce wear

Question 24

What is the role of the firbous capsule?

Answer 24

Links bones together.
Limits excessive movement of the joint
Contains and protects the structures of the joint

Question 25

Describe the structure of a fibrous capsule

Answer 25

A capsule consists of bands of tissue which form a sleeve around the joint supporting and enclosing it but not interfering with the movement.
Capsules vary in their structure. Some are a complete sleeve around the joint (such as the hip joint) whereas o thers are incomplete instead being replaced by other structures such as ligaments and muscles (this is the case in the knee joint).
* Outer layer - dense fibrous tissue (collagen)
* Inner layer – synovial membrane – specialist secretory cells
The capsule is often perforated by blood vessels, nerves, and may also allow bursae to protrude from inside the joint.

Question 26

What are bursae?

Answer 26

Fluid filled pouches of the synovial membrane.

Question 27

Where is the synovial membrane located?

Answer 27

In synovial joints: lining the joint capsule and the non
articular parts of the bones inside the capsule.
It also lines structures such as
bursae and tendon sheaths synovial membrane occurs wherever human beings need
to minimize friction between moving parts.

Question 28

What are synoviocytes?

Answer 28

Type A synoviocytes are responsible from the removal of debris within the joint. Type B
synoviocytes produce and secrete synovial fluid into the joint.

Question 29

What is a ligament?

Answer 29

A ligament is a structure made of deep fibrous ligaments which most commonly connect bone to bone.

Question 30

What is the function of a ligament?

Answer 30

Connect bones together, providing the joint with additional support. Prevents excessive or abnormal movement at a joint, and prevent damage to a joint, without impacting normal movement.

Question 31

Define an ‘extracapsular ligament’

Answer 31

Ligaments that often attach beyond the margins of the joint and are also called accessory ligaments.

Question 32

Define an ‘intracapsular structure’

Answer 32

Some synovial joints have specialised structures which reside within the capsule or joint cavity.

Question 33

Define a ‘capsular ligament’

Answer 33

Ligaments that blend with the fibrous capsule or are simply thickenings of the fibrous capsule.

Question 34

What is the extent of movement in a synovial joint determined by?

Answer 34

• The closeness and shape of the joint surfaces
• The nature and density of the surrounding soft tissue (including muscle tissue)
• The form and attachment of the ligaments surrounding the joint

Question 35

Do lower limb joints favour stability or mobility?

Answer 35

Stability

Question 36

Describe the ‘close pack position’

Answer 36

The position of synovial joints where they are most stable. This is when the bony contact is
highest between the bones, or when the ligaments and soft tissue surrounding the joint are at
their most taut, or a combination of the two.

Question 37

Describe the ‘loose pack position’

Answer 37

The position of least stability in synovial joints: where the bony surfaces are in least contact, or where the soft tissue structures of the joint are most lax.

Question 38

Describe the process in which joints are classified

Answer 38

a)Type: Fibrous , Cartilaginous , or Synovial?
b)Complexity:
* Simple-Two articular surfaces without any intervening structures (such as the hip joint)
* Compound-More than two articular surfaces without any intervening structures (such
as the ankle joint)
* Complex-A joint which possess an intra articular structure which intervenes between
the articular surfaces (such as the knee joint)
c)Freedom of movement:
* Uni axial movement can occur in one plane of movement only (such as the ankle joint)
* Bi axial movement can occur in two planes of movement (s uch as the knee joint)
* Multi axial movement can occur in three planes of movement (such as the hip joint)
d)Description or shape:
* Ball and socket such as the shoulder or hip
* Hinge such as the ankle or joints of the toes
* Saddle such as the 1 st Carpometacarpal Joint at the base of the thumb

Question 39

List and describe the different types of fibres found in a joint

Answer 39

• Longitudinal fibres – Straight line between femur and acetabulum
• Oblique fibres – Diagonal line between femur and acetabulum fat pad
• Arcuate fibres – Arch from one part of the acetabulum to another
• Zona Orbicularis – Deep part of the capsule. No bony attachment. Run in a circular fashion around the capsule, strengthening it

Question 40

Identify the bones in articulation at the hip joint

Answer 40

The acetabulum: Hemispherical socket deficient inferiorly on the lateral surface of the innominate at the site of fusion of the ilium, pubis and ischium, depened by the fibrocartilaginous acetabular labrum. The semilunar articular surface is covered with hyaline cartilage: the central part of the acetabulum is the thin walled non-articular acetabular fossa formed mainly by the ischium.
Head of femur: Approx. 2/3 sphere, slightly compressed anteroposterior, covered by hyaline cartilage except for a small area superolaterally adjacent to the neck and at the fovea capitis.