Joints

Question 1

What is the definition of a joint?

Answer 1

Connection between two bones in the skeleton

• Synovial= articular cavity
• Solid= connective tissue

Question 2

Describe Cartilage

Answer 2

• Reinforces articulating surfaces
• Supports soft tissue structures
• Avascular, aneural
• Able to tolerate stress and maintain flexibility

Question 3

What is the Ultrastructure (1) of cartilage?

Answer 3

• Produced by chondroblasts (flat irregular cells)

- Produces ECM which is composed mainly of collagen

Question 4

What are Chondrocytes?

Answer 4

Chondroblasts that become less active with age

Question 5

What is Lacunae?

Answer 5

Pools of ECM which contain the chondrocyte

Question 6

What are the types of cartilage?

Answer 6

• Hyaline
• Fibrocartilage
• Elastic

Question 7

How are joints classified?

Answer 7

-Type of tissue forming the joint
-Degree of movement across the joint:
=Fibrous tissue- synarthrosis movement
=Cartilaginous- amphiarthrosis movement
=Synovial- diarthrosis

Question 8

What are fibrous joints?

Answer 8

• Strong joints made up of tough fibrous tissue
• Joined by dense connective tissue
• Collagen is main constituent

Question 9

What are the types of fibrous joints?

Answer 9

• Sutures
• Gomphoses
• Syndesmoses

Question 10

Describe Sutures

Answer 10

• Immobile (synarthrosis)
• Between flat bones of the skull
• Important during birth (deformation)
• Fixation around 20 years of age

Question 11

Describe Gomphoses

Answer 11

• Immobile (synarthrosis)
• Between upper teeth and maxilla, and lower teeth and mandible
• Periodontal ligament

Question 12

Describe Syndesmoses

Answer 12

• Slightly mobile (amphiarthroses)
• Bone bound together by interosseous membrane
• Middle radioulnar joint and middle tibiofibular joints

Question 13

What are cartilaginous joints?

Answer 13

• Bones are connected by either hyaline or fibrocartilage
• Hyaline= glassy, semi-transparent
• Fibrocartilage= hybrid tissue between dense fibrous connective tissue and hyaline cartilage

Question 14

What are the types of cartilaginous joints?

Answer 14

• Synchondroses

- Sympheses

Question 15

Describe Synchondroses

Answer 15

• Hyaline cartilage between bones
• Immobile (synarthrosis)
• Between diaphysis and epiphysis or growing long bone

Question 16

Describe Sympheses

Answer 16

• Fibrocartilage between bones
• Slightly mobile (amphiarthrosis)
• Pubic symphysis, intervertebral joints

Question 17

What are synovial joints?

Answer 17

• Fluid filled cavity within fibrous joint capsule
• Highly mobile
• Most common joint type in body
• Subclasses (articular surface and movement)
• Articular capsule, articular cartilage, synovial fluid

Question 18

What is the Articular Capsule?

Answer 18

-Continuous with periosteum
-Encloses the joint
-2 layers
=Fibrous layer (outer)- white fibrous tissue, capsular ligament
=Synovial layer (inner)- serous connective tissue, vascularized, synovium
-Synovium secretes synovial fluid and controls exchange of nutrients

Question 19

Describe Articular Cartilage

Answer 19

• Articulating surfaces are covered in hyaline cartilage

- Cartilage reduces friction for movement and acts as shock absorber

Question 20

What is synovial fluid?

Answer 20

-Lies in the joint cavity and acts to:
=Lubricate the joint
=Absorb shock
=Distribute nutrients to the articular cartilage (avascular)

Question 21

What are Accessory Ligaments?

Answer 21

• Connective tissue

- Resist excess strain across joint

Question 22

What are Bursae?

Answer 22

• Synovial fluid filled sac
• Protective, cushions joint
• Reduces friction

Question 23

Describe the Innervation of Synovial Joints

Answer 23

• Articular nerves
• Hilton’s law: the nerves supplying a joint also supply the muscles moving the joint and the skin covering their distal attachments

Question 24

Describe Synovial joint vasculature

Answer 24

• Articular arteries arise from vessels surrounding the joint
• Lie within the synovial membrane
• Form communications (anastomoses)
• Articular veins

Question 25

What are the types of synovial joint?

Answer 25

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

Question 26

Describe a Hinge joint

Answer 26

- Movement in 1 plane (flexion and extension) | - Found in the elbow, ankle and knee joints

Question 27

Describe a Saddle joint

Answer 27

- Opposing articular surfaces (concave-convex) | - Found in carpometacarpal joints

Question 28

Describe a Plane joint

Answer 28

- Flat articular surfaces - Bones glide over each other - Found in acromioclavicular joint of the shoulder and subtalar joint

Question 29

Describe a Pivot joint

Answer 29

- Central bony pivot surrounded by ligamentous ring - Allows rotational movement - Found in atlantoaxial joint and proximal and distal radioulnar joints

Question 30

Describe a Condyloid joint

Answer 30

- Also known as an ellipsoid joint - Convex surface articulating with concave surface - Found in joints of wrist, metacarpophalangeal and metatarsophalangeal joints

Question 31

Describe a Ball and Socket joint

Answer 31

- Ball shaped surface of one bone articulating with cup shaped surface of another bone - Highly mobile joint with movement across many axes - Found in joints of the hip and shoulder

Question 32

What are Synarthrosis joints?

Answer 32

- Immovable, fixed joint - Fibrous connective tissue - Provide protection - Sutures of the skull

Question 33

What are Amphiarthrosis joints?

Answer 33

- Slightly moveable - Fibrous and cartilaginous joints - Intervertebral joints of the spine, pubic symphysis of the pelvis

Question 34

What are Diarthrosis joints?

Answer 34

- Freely moveable - All synovial joints - Appendicular skeleton - Uniaxial, biaxial, multiaxial

Question 35

What is uniaxial?

Answer 35

- Movement in 1 plane | - Hinge: elbow, knee, ankle

Question 36

What is biaxial?

Answer 36

- Movement in 2 planes | - Condyloid: metacarpophalangeal joints

Question 37

What is multiaxial?

Answer 37

- Movement in several planes (3 axes) | - Ball and Socket joints: shoulder, hip

Question 38

What factors affect joint stability?

Answer 38

- Articular surfaces= size, shape, arrangement - Ligaments= number, rigidity - Muscle= tone, arrangement

Question 39

Describe the role of ligaments in joint stability

Answer 39

- The more ligaments a joint has and the more rigid they are, the more stable the joint will be - Reduce movement across a joint

Question 40

Describe the role of muscles in joint stability

Answer 40

- Increased muscle tone around a joint increases joint stability - Rotator cuff muscles around the shoulder joint