L10 The principles of articulation: fibrous, cartilaginous and synovial joints

Question 1

Articulation/joint/arthrosis

Answer 1

Point of contact between:

• Neighbouring bones
• Bone and cartilage
• Bone and teeth

Question 2

How are joints classified

Answer 2

• Structure
• Function
• Movement

Question 3

Structural classification

Answer 3

• Presence or absence of a synovial cavity and the type of connective tissue
• Described as either fibrous, cartilaginous or synovial

Question 4

Functional classification

Answer 4

Based on the degree of movement permitted:

• Synarthrosis (immovable)
• Amphiarthrosis (partially moveable)
• Diarthrosis (freely moveable)

Question 5

Fibrous joints

Answer 5

• No synovial cavity
• Held together by a fibrous connective tissue
• Permits little or no movement (synarthrosis/amphiarthrosis)

Question 6

Types of fibrous joints

Answer 6

1. Suture
2. Syndemosis
3. Interosseous membrane

Question 7

Fibrous joints - suture

Answer 7

• Unite skull bones
• Thin layer of dense connective tissue
• Irregular
• Interlocking edges provide strength, permit no movement (synarthrosis)
• Ossification of a suture forms a synostosis

Question 8

Fibrous joints- syndesmosis

Answer 8

• More connective tissue than seen in a suture
• Crosses a greater distance than a suture
• Connective tissue typically arranged into bundles (ligament)
• Typically permit slightly movement(amphiarthrosis)

Question 9

Examples of synesmosis in fibrous joints

Answer 9

Between fibula and tibia - anterior tibiofibular ligament

Gomphosis (or dentoalveolar)

Question 10

Fibrous joints - interosseous membranes

Answer 10

• Sheet of dense connective tissue
• Binds adjacent long bones
• Amphiarthrosis

Question 11

Examples of interosseous membranes in fibrous joints

Answer 11

Two main examples between the radius and ulna in forearm, and tibia and fibia in the leg

Question 12

Cartilaginous joints

Answer 12

• No synovial cavity
• Held together by a fibrocartilage or hyaline cartilage
• Permits little or no movement (synarthrosis/amphiarthrosis)

Question 13

Types of cartilaginous joints

Answer 13

1. Synchrondosis

2. Symphysis

Question 14

Cartilaginous joints - synchrondosis

Answer 14

• The connective tissue is hyaline cartilage
• Synarthrosis
• Example - epiphyseal plate (growth plate)
• At skeletal maturity the epiphysis, metaphysis and epiphyseal plate fuse forming a synostosis

Question 15

Cartilaginous joints - symphysis

Answer 15

• Connective tissue is fibrocartilage
• Adjacent bones lined with hyaline cartilage, but with a broad disc of fibrocartilage connects the bones
• Amphiarthrosis

Question 16

Where do all symphysis occur

Answer 16

All symphysis occur in the midline of the body:

• Junction of the manubrium and sternum
• Intervertebral discs
• Pubic symphysis

Question 17

Synovial joints

Answer 17

• Synovial (joint) cavity between articulating bones
• Freely moveable - diarthrosis
• Layer of hyaline cartilage called articular cartilage

Question 18

Synovial joint structure - articular cartilage

Answer 18

• Covers the bones at synovial joints

- Avascular

Question 19

What is articular cartilage composed of

Answer 19

• Composed of collagen and proteoglycan

- Orientation of collagen structure imparts resistance to compression and an extremely low resistance surface

Question 20

Synovial joint structure - articular capsule

Answer 20

• Encapsulates a synovial joint
• Composed of two layers
• Outer fibrous membrane connects to periosteum (flexibility permits movement, fibres arranged into bundles - high tensile strength)
• Inner layer termed synovial membrane (areolar connective tissue rich in elastic fibres occasionally contains structural fat pads

Question 21

Synovial joint structure - synovial fluid

Answer 21

• Secreted by synovial membrane
• Rich in hyaluronic acid, secreted by fibroblast-like cells, and interstitial fluid from blood plasma
• Lubricates articular surface (reducing friction)
• Provides some shock-absorbing properties
• Supplies nutrition to, and removes waste products from the avascular articular cartilage
• Phagocytes remove microbes and debris

Question 22

Synovial joint structure - accessory ligaments

Answer 22

Intracapsular and extracapsular ligaments

Question 23

Location of intracapsular ligaments

Answer 23

Intracapsular ligaments lie within the joint capsule

• Excluded from synovial fluid by folds in synovial membrane
• eg. anterior and posterior cruciate ligaments of the knee

Question 24

Location of extracapsular ligaments

Answer 24

Outside the joint capsule

- eg. fibular and tibial collateral ligaments of the knee

Question 25

Synovial joint structure - accessory articular discs

Answer 25

- Fibrocartilage pads lie between articular cartilage of some synovial joints eg meniscus of the knee - Called meniscii or articular discs - Help maintain joint stability - Direct the flow of synovial fluid - Meniscal tears (common in athletes)

Question 26

Synovial joint structure - nerve and blood supply

Answer 26

- Nerve endings same as those - Distributed to the articular capsule and associated ligaments - Pain and proprioception - Many components of the synovial joint are avascular - Rely on numerous branching of arteries and veins to supply associated tissue

Question 27

Synovial joint structure - bursae and tendon sheaths

Answer 27

- Moving parts of joints can cause friction - Bursae are fluid filled sacs lined with synovial like membrane - Bursae cushion movement between body parts - Tendon sheaths are similar to bursae - Specialised membranes that wrap around tendons - Especially where many tendons come together and/or pass through a synovial joint capsule

Question 28

Types of synovial joints - movement

Answer 28

- Planar - Hinge - Pivot - Condyloid - Saddle - Ball and socket

Question 29

Planar synovial joints

Answer 29

- Surfaces flat or slightly curved | - Permit back and forth, and side to side movements

Question 30

Examples of planar joints

Answer 30

- Intercarpal joints (between carpal bones at the wrist) | - Intertarsal joints (between tarsal bones at the ankle)

Question 31

Hinge synovial joint

Answer 31

- Concave surface of one bone fits the convex surface of another - Permits motion in a single axis (flexion and extension)

Question 32

Examples of hinge synovial joints

Answer 32

- Knee joints | - Elbow joints

Question 33

Pivot joints

Answer 33

- Rounded or pointed surface of one bone pivots inside a ring formed by the other bone and a ligament - Permits rotation in its longitudinal axis (monoaxial)

Question 34

Examples of pivot joints

Answer 34

- Radioulnar joints | - Atlanto-axial joint

Question 35

Condyloid joints

Answer 35

- Convex oval projection of one bone fit into the oval depression of the other - Permits movement around two axis (biaxial; flexion and extension, and abduction and adduction)

Question 36

Examples of condyloid joints

Answer 36

- Wrist joint | - Metacarpophalangeal joints

Question 37

Saddle joints

Answer 37

- One bone fits into the saddle shaped bone it opposes - Modified condyloid joint - Permits movement around two axis(biaxial; flexion and extension, abduction and adduction, (sometimes limited rotation)

Question 38

Examples of saddle joints

Answer 38

- Carpometacarpal joint

Question 39

Ball and socket joint

Answer 39

- Ball-like surface of one bone fits into the cup-like depression of the other - Triaxial movement around three planes (triaxial; flexion and extension, abduction and adduction, and rotation)

Question 40

Examples of ball and socket joints

Answer 40

- Shoulder joint | - Hip joint

Question 41

Glenohumeral (shoulder) joint

Answer 41

- Synovial ball and socket joint - Joint between the proximal humerus and the scapula(glenoid fossa) - Due to the shallowness of the glenoid cavity, it is the most mobile joint in the body - Four associated bursae

Question 42

What is the glenoid labrum

Answer 42

- A narrow rim of fibrocartilage - deepens glenoid

Question 43

Which ligaments stabilise glenohumeral joint

Answer 43

- Glenohumeral - Coracohumeral - Transverse humeral

Question 44

Rotator cuff muscles

Answer 44

Supraspinatus Infraspinatus Teres minor Subscapularis

Question 45

Acromioclavicular joint

Answer 45

- Technically a synovial gliding joint(planar) but it acts like a pivot - Joint between the acromion (part of the scapula) and the clavicle - Allows the movement of the scapula, permitting greater arm rotation(above the head)

Question 46

Sternoclavicular joint

Answer 46

- Synovial saddle joint - Medial clavicle fits into a hollow formed by the superlateral surface of the manubrium and the medial costal cartilage of the first rib - Fibrocartilagenous articular disc divides the joint into two synovial cavities

Question 47

Ligaments reinforcing sternoclavicular joint

Answer 47

- Reinforced by interclavicular, anterior, and posterior sternoclavicular ligaments - Although a saddle joint - is capable of triaxial movement - all movement is passive