Cartilage, Bones and Joints

Question 1

Explain what cartilage is and describe how it is classified

Answer 1

• Cartilage is a strong, flexible and semi-rigid supporting tissue, and forms a precursor to bone
• Is involved in supporting structures which are subject to forces
• Elastic cartilage: Ear and epiglottis
• Fibrocartilage: intervertebral disks and symphysis pubis
• Hyaline cartilage: articular surfaces of bones in joints and costal cartilages of rib cage

Question 2

What are the cells of cartilage?

Answer 2

• Chondrocytes

Question 3

Describe spongey and compact bone

Answer 3

• Compact: made of tightly packed circular units (osteons) and lamellar bone
• Spongy: the result of osteons being partially removed, leaving gaps between the remaining struts of bone *this is done by osteoclasts

Question 4

List the cells of cartilage and bone, their matrix,p and give their functions

Answer 4

• Osteoprogenitor cells: stem cells located in the bone that play an important role in bone repair and growth – produce osteoblasts
• Osteoblasts: derived from osteoprogenitor cells. They form bone tissue by synthesising and secreting bone matrix
• Osteocytes: derived from osteoblasts. They are mature bone cells which maintain bone tissue
• Osteoclasts: derived from haemopoietic stem cells and are involved in the resorption of bone

Question 5

Define the parts of the skeleton and their functions

Answer 5

• Axial: trunk
• Appendicular: limbs
• Bones that connect limbs to trunk: limb girdles
• Functions: support, movement, protection, storage (calcium) and haemopoiesis (in adults, only axial and limb girdles)

Question 6

List the anatomical terms to describe bones and give examples

Answer 6

• Long bones – humerus
• Short bones – carpal bone
• Flat bone – sternum
• Irregular bone – vertebra
• Sesamoid bone - patella

Question 7

Name the 6 basic types of joints (give examples)

Answer 7

• Ball and socket – shoulder (scapula and head of humerus)
• Saddle – carpal and first metacarpal
• Pivot – radius and ulna
• Hinge – humerus and ulna
• Gliding – carpals
• Ellipsoid – metacarpal and phalanx

Question 8

Classify and describe the different types of joints by structure (name examples of each)

Answer 8

• Fibrous joints – connects bones without allowing any significant movement (eg. tibia and fibula)
• Cartilaginous joints – joints in which bones are attached by cartilage and allow for a little movement (ribs or intervertebral disks)
• Synovial joints – allow for much more movement. Surfaces of the bones are covered in hyaline cartilage and cavities between bones in synovial joints are filled with synovial fluid to help lubricate and protect bones (hip, knee, shoulder)

Question 9

Classify and describe the different types of joints by movement (name examples of each)

Answer 9

• Uni-axial – moves in one plane only (gliding joints, hinge joints, pivot joints)
• Bi-axial – moves in two planes (ellipsoid joint, saddle joint)
• Tri-axial – moves in three planes )ball and socket)

Question 10

Describe the structure and role of intra-articular disks

Answer 10

• Are fibrocartilage found inside the cavity of joints and serve to aid the movement of a joint *largest are the menisci of the knee joint

Question 11

Describe the different structures that determine joint stability

Answer 11

• Articular shape – deep socket is better than a shallow one
• Strength of capsule – capsule which tightens upon movement will provide stability against that movement
• Ligaments – either within or outside the capsule will give added support against unwanted movements
• Muscles – tone of muscles crossing a joint play an important factor in providing support
• Tendons – provide a physical barrier to unwanted movements of the joint