The Principles of Articulation

Question 1

Define the following:

Synarthrosis

Amphiarthrosis

Diarthrosis

Answer 1

• Synarthrosis: immovable
• Amphiarthrosis: partially moveable
• Diarthrosis: freely moveable

Question 2

Describe Fibrous joints

• subdivisions

Answer 2

• No synovial cavity
• Held together by a fibrous connective tissue
• Permits little or no movement (synarthrosis/amphiarthrosis)
• Three types of fibrous joint:
  
  • 1. Suture
  • 2. Syndesmosis
  • 3. Interosseous membrane

Question 3

Describe Fibrous joints - Suture

Answer 3

• 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
  
  • e.g. left & right sides of frontal bone fuse ~6 years of age

Question 4

Describe Fibrous joints- Syndesmosis

- examples

Answer 4

• More connective tissue than seen in a suture
• Crosses a greater distance than a suture
• Connective tissue typically arranged into bundles (ligament)
• Typically permit slight movement (amphiarthrosis)
• example
  
  • Distal tibiofibular joint: connected by the tibiofibular ligament
  • Gomophosis (dentoalveolar): connective tissues is called periodontal ligament

Question 5

Describe Fibrous joints: Interosseous membranes

• example

Answer 5

• Sheet of dense connective tissue
• Binds adjacent long bones
• Amphiarthrosis
• Two main examples between the radius and ulna in forearm, and tibia and fibula in the leg

Question 6

Describe Cartilaginous joints

• different types

Answer 6

• No synovial cavity
• Held together by fibrocartilage or hyaline cartilage
  
  • hyaline cartilage is more synarthrotic
• Permits little or no movement (synarthrosis/amphiarthrosis)
• Two types of cartilaginous joint:
  
  • 1. Synchrondosis
  • 2. Symphysis

Question 7

Describe Cartilaginous joints: Synchrondosis

• example
• clinical relevance

Answer 7

• 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 become stronger and more solid

Question 8

Describe Cartilaginous joints: Symphysis

• example

Answer 8

• Connective tissue is fibrocartilage
• Adjacent bones lined with hyaline cartilage, but with a broad disc of fibrocartilage connects the bones
• Amphiarthrosis
• All symphysis occur in the midline of the body:
  
  • Junction of the manubrium and sternum
  • Intervertebral discs
  • Pubic symphysis

Question 9

Describe Synovial joints

Answer 9

• Synovial (joint) cavity between articulating bones
• Freely moveable - diarthrosis
• Layer of hyaline cartilage called articular cartilage lining the bone
  
  • there is an additional lining cartilage at the knee

Question 10

Describe the role and structure of Articular cartilage

Answer 10

• Covers the bones at synovial joints
• Avascular (no point)
• Composed of collagen and proteoglycan
• Orientation of collagen structure impairs resistance to compression & an extremely low resistance surface
  
  • arches of chondrocytes gives it a strong structure

Question 11

Describe the role and structure of the Articular capsule

Answer 11

• Encapsulates a synovial joint
• Composed of two layers
• Outer fibrous membrane connects to the periosteum of the bone
  
  • 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 articular fat pads

Question 12

Describe the role and composition of Synovial fluid

Answer 12

• Secreted by the 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 13

What are the types of Accessory ligaments found at the synovial joint

-example

Answer 13

• Intracapsular ligaments lie within the joint capsule
• Excluded from the synovial fluid by folds in the synovial membrane

- e.g. anterior and posterior cruciate ligaments of the knee

• Extracapsular ligaments lie outside the joint capsule

- e.g. fibular and tibial collateral ligaments of the knee

Question 14

What is the role and structure of Accessory articular discs at Synovial joints?

• example/ clinical relevance

Answer 14

• Fibrocartilage pads lie between articular cartilage of some synovial joints e.g.meniscus of the knee
• Called meniscii or articular discs
• Help maintain joint stability
• Direct the flow of synovial fluid
• meniscal tears are common in athletes: important to try and maintain as much of it as possible as if removed –> osteoarthritis

Question 15

What are the key nerve and blood supply points about synovial joint structures

Answer 15

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

Question 16

What are Bursae and tendon sheaths of Synovial joint structures.

• what is their role?

Answer 16

Bursae

• 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

• Similar to bursae
• Specialised membranes that wrap around tendons
• Especially where many tendons come together and/or pass through a synovial joint capsule

Question 17

What is the classification for synovial joints by movement?

(6)

Answer 17

• Planar
• Hinge
• Pivot
• Condyloid
• Saddle
• Ball & Socket

Question 18

Describe a Hinge Synovial joint

• examples (2)

Answer 18

• Concave surface of one bone fits the convex surface of another
• Permits motion in a single axis (flexion and extension)
• Examples include:
  
  • knee joints
  • elbow joints

Question 19

Describe a Pivot Synovial joint

• examples (2)

Answer 19

• Rounded or pointed surface of one bone pivots inside a ring formed by the other bone and a ligament
• Permits rotation in its the longitudinal axis (monoaxial)
• Examples include:
  
  • radioulnar joints
  • atlanto-axial joint
    
    • allows shaking of the head

Question 20

What is the Atlanto-axial joint?

Answer 20

• Dens of the axis slots into and against the atlas,
• bounded by the transverse atlantal ligament
• allows shaking of the head

Question 21

Describe A Planar Synovial joint

• examples (2)

Answer 21

• Surfaces flat or slightly curved
• Permit back and forth, and side to side movements
• Examples include:
  
  • intercarpal joints (between carpal bones at the wrist)
  • intertarsal joints (between tarsal bones at the ankle)

Question 22

Describe a Saddle Synovial joint

• examples (1)

Answer 22

• 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))
• Examples include:
  
  • carpometacarpal joint

Question 23

Describe a Ball and Socket Synovial joint

• examples (2)
• clinical significance

Answer 23

• 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)
• Examples include:
  
  • shoulder joint
  • hip joint
• most at risk of dislocation due to wider range of movement

Question 24

Describe a Condyloid Synovial joint

• examples (2)

Answer 24

• 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)
  
  • Examples include:
  • wrist joint
  • metacarpophalangeal joints

Question 25

What is the role of the Glenohumeral joint

• type of joint
• structure
• ligaments

Answer 25

• 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
• Glenoid labrum; a narrow rim of fibrocartilage – deepens glenoid
• Stabilised by three ligaments:
  
  • glenohumeral
  • coracohumeral
  • transverse humeral
• Four associated bursae
• more strength provided by the Rotator cuff muscles

Question 26

What is the role of the Acromioclavicular joint

• type of joint
• structure
• ligaments

Answer 26

• Technically a synovial gliding joint (planar) but it acts like a pivot
• Joint between the acromion (part of the scapula) and the clavical
• Stabilised by three ligaments:
  
  • acromioclavicular
  • coracoacromial
  • coracolclavicular (conoid and trapezoid)
• Allows the movement of the scapula, permitting greater arm rotation (above the head)

Question 27

What is the role of the Sternoclavicular joint

• type of joint
• structure
• ligaments

Answer 27

• Synovial saddle joint
  
  • Although a saddle joint – is capable of triaxial movement – all movement is passive
• Medial clavicle fits into a hollow formed by the superolateral surface of the manubrium and the medial costal cartilage of the first rib.
• The fibrocartilagenous articular disc divides the joint into two synovial cavities
• Reinforced by ligaments
  
  • interclavicular, anterior, and posterior sternoclavicular ligaments

Question 28

What are the 3 ligaments of the glenohumeral joint?

• structure/ role

Answer 28

• Glenohumeral ligaments: superior, middle and inferior ligaments are thickenings of the joint capsule
• Coracohumeral ligament: joins superior joint capsule to the coracoid process
• Transverse humeral ligament: bridges bicipital groove, stabilizing bices tendon

Question 29

What are the rotator cuff muscles?

• individual movements
• joint role

Answer 29

• Supraspinatus - abducts and externally rotates humerus
• Infraspinatus - externally rotates humerus
• Teres minor - externally rotates humerus
• Subscapularis - internally rotates humerus
• they join the scapula with the humerus and encircle the glenohumeral joint and fuses the joint with the capsule providing more strength