1.4 Bone and skeleton

Question 1

What is bone?

Answer 1

Connective tissue made up of cells suspended in a matrix

• 65% mineral compound (hydroxyapatite)
• 30% organic material (mostly type I collagen)

Question 2

What is a long bone?

Answer 2

A bone with a shaft and two ends and is longer than it is wide

Question 3

What are features of a long bone?

Answer 3

Cortical bone 
Trabecular bone 
Articular cartilage 
Epiphyseal plate 
Medullary cavity 
Marrow 
Blood vessels 
Periosteum

Question 4

What is important about the medullary cavity?

Answer 4

Present in dead bone but filled with bone marrow in living bones
- storage site for fat, blood and stem cells

Question 5

What is important about the epiphyseal plate?

Answer 5

AKA growth plate

• filled with avascular cartilage which supplies tissue to elongate the bone
• ossifies when maturity is reached

Question 6

What is important about the metaphysis region?

Answer 6

Absent in non long bones

- how long bones grow

Question 7

What is important about the periosteum?

Answer 7

Has a blood supply - perforates the inner regions of bone
- essential for bone maintenance and bone re-scaling
greater osteogenesis (growth) than osteolysis (death)
- two layers

Question 8

What are structural features of flat bones?

Answer 8

No medullary cavity

2 layers of compact bone surrounding either spongy bone or air/space

Question 9

What are structural features of short/irregular bones?

Answer 9

Also have no medullary cavity

Develop from a single centre of ossification

Question 10

What is important about the endosteum?

Answer 10

Lines the medullary cavity
Single layer
Osteolysis greater than osteogenesis

Question 11

Describe the blood and nervous supply of blood

Answer 11

Well vascularised
Arteries enter via nutrient foramen in diaphysis and pass through subchondral bone to supply calcified part of cartilage
Haversian and Volkmann canals supply cortical bone
Trabecular bone supplied via bone marrow

Question 12

Why are bones stiffer along the long axis than the transverse axis?

Answer 12

Due to layering that occurs in the long axis - wrapping around the layers of the lamellae

Question 13

What is an osteon?

Answer 13

Structural unit of compact bone, consisting of concentric bone layers called lamellae, which surround a long passageway (Haversian canal)

Question 14

What is an important feature of an osteon?

Answer 14

Collagen fibres run in different directions in neighbouring lamellae

Question 15

What is a sesamoid bone?

Answer 15

Small bones that usually appear in places with a high stress concentration e.g., the patellar attached proximally via the quadraceps tendon and distally via the patellar tendon to the tibia

Question 16

What are the functions of sesamoid bones?

Answer 16

1. Ease tendon path and prevent excessive tendon wear

2. Increases moment arm of muscle

Question 17

What are surface markings found on bones?

Answer 17

Protuberences and prominences

Question 18

How are surface markings formed?

Answer 18

High stress = muscle/tendon attached to bone which pulls the regional portion of the tissue

Question 19

What are functions of the surface markings?

Answer 19

1. Leverage
2. Muscle attachment
3. Response to strain within bone
4. Articulations with other bones