Lecture 5: Bone Growth in Joints - Tissue And Structures (Joints I)

Question 1

What does it begin as and when does bone start to grow?

Answer 1

Bones begin as a cartilage model ad start to grow 6 weeks after fertilisation.

Question 2

What is endochrondral ossification?

Answer 2

The process of transforming cartilage to bone

Question 3

What is the primary centres of ossification?

Answer 3

Diaphyses (shafts) are primary ossification centres
• Epiphyses remain cartilage
• Develop at different times depending on the bone

Question 4

What is the secondary ossification centre?

Answer 4

Epiphyses are the secondary ossification centres
• Same ossification process as primary centres
Separates from diaphysis by an epiphseal plate

Question 5

What is bone growth enabled by?

Answer 5

Epiphyseal plates (aka growth plates)

Question 6

What happens when bone growth is finished?

Answer 6

Starting from puberty (when bone growth is finished), epiphyses start to fuse with diaphyses.

Question 7

How does a bone grow in length?

Answer 7

Through the epiphyseal plate (growth plates)

Question 8

How does a bone grow in width?

Answer 8

• Appositional growth
• OB activity prodxes circumferential lamellae.
• OC’s mould the bone shape and form the medullary cavity.

Question 9

What is a joint?

Answer 9

• Location that holds bones together
• Is where bones meet (articulation)
• Involves bone shapes and soft tissues
• Allows free movement / control of movement

Question 10

What soft tissues are associated with joints?

Answer 10

• Different compositions depending on function
• Having no inorganic component
• Cartilage: Hyaline (articular) + Fibrocartilage

Question 11

What is the general composition if cartilage?

Answer 11

• Collagen fibres in a ground substance, chondrocytes in lacunae
• Blood vessels don’t penetrate cartilage
• Nutrients diffused through matrix by joint loading

Question 12

What is hyaline (articular) cartilage?

Answer 12

• Collagen fivrew are barely visible
• High Pressure ater content in matrix
• Smooth frictionless surface

Question 13

What are the functions of hyaline (articular) cartilage?

Answer 13

• To resist compression
• To mould to surfaces of bones where they articulate

• Degrades with age

Question 14

What is fibrocartilage?

Answer 14

• Collagen fibres that have formed throughout matrix.
• Orientation of fibres aligns with stresses

Question 15

What are the functions of fibrocartilage?

Answer 15

• To resist compression and tension
• Deepening of articular surfaces
• Acts as a buffer/shock absorber (distribute force over a wider area)

Question 16

What structures are associated with joints?

Answer 16

Ligaments and tendons
• Dense fibrous connective tissue (DFCT)
• Collagen
• Elastin (more stretchy)
• Fibroblasts (cytes)

Question 17

What is the purpose of a ligament in joints?

Answer 17

To connect bone to bone

Question 18

What is the function of ligaments in joints?

Answer 18

To restrict movement (away from themselves), e.g. lateral ligaments will restrict movement medially
• Elastin + collagen means they stretch and allow recoil)

Question 19

What is the purpose of tendons in joints?

Answer 19

To connect muscle to bone

Question 20

What is the function of tendons in joints?

Answer 20

To facilitate and control movements (less elastin content than ligaments)
• Contraction of muscles transmitted to bone

Question 21

What affects the amount of soft tissue support in joints?

Answer 21

The amount of bony congruency

Question 22

How does the amount of bony congruency affect the amount of soft tissue support in joints?

Answer 22

Less congruency = more soft tissue support needed

Question 23

What is bony congruency?

Answer 23

How well 2 surfaces fit together (e.g. bones at the hip joint have high bony congruency and the bones at the knee joint have low bony congruency).

Question 24

What is the difference between tissues and structures?

Answer 24

• Tissues are cells that have grouped together in a highly organised manner according to specific structure and function.
• Structures are things that are formed of tissue.

Question 25

What are the different types of joints?

Answer 25

• Fibrous
• Cartilaginous
• Synovial

Question 26

What type of range of motions (ROM) do the different joint types have?

Answer 26

• Fibrous & cartilaginous = < ROM
• Synovial = > ROM

Question 27

What is a fibrous joint?

Answer 27

Tissue: DFCT
Structure: ligament
Function: limit movement and provide stability

Example: cranial sutures (stability for brain case)

Question 28

What is a cartilaginous joint?

Answer 28

Tissue: fibrocartilage
Structure and function: various structures with special functions

Example: intervertebral disc (structure between vertebrae) or pubic symphysis (joint)