intro to bones and tissues

Question 1

• How many bones in adults and children respectively?

Answer 1

206 (+ sesamoids)

270 children

Question 2

• What is the Axial skeleton comprised of?

Answer 2

Cranium

Vertebral Column

Rib Cage

Question 3

• What is the Appendicular skeleton comprised of?

Answer 3

Pectoral girdle

Upper and Lower Limbs

Pelvic Girdle

Question 4

• What are the functions of the skeleton?

Answer 4

Supports body so you can stand up and not fall

Protection of your vital organs

Movement - works with muscles so you can get around

Mineral storage - Stores calcium and phosphate

Produces blood cells

Question 5

• What two ways do bones develop in utero?

Answer 5

Intramembranous Ossification - First occurs after conception → flat bones
mesenchymal cells -> bone

Endochondral Ossification - Begins 2 months into utero → long bones mesenchymal cells -> cartilage -> bone

Question 6

• What are the different types of bone cells and what do they do?

Answer 6

Osteogenic cell - Bone ‘stem cell’

Osteocyte - 'Mature' bone cell, formed when osteoblast becomes imbedded in its secretions and they sense mechanical strain to direct osteoclast and osteoblast activity

Osteoblast - Bone 'forming' Secretes 'osteoid' and catalyses mineralisation of osteoid

Osteoclast - Bone 'breaking', dissolve and resorb bone by phagocytosis and are derived from bone marrow?

Question 7

• Where are Osteogenic cells and Osteocytes found respectively?

Answer 7

Osteogenic cells - Deep layers of periosteum

Osteocytes - Entrapped in matrix

Question 8

• Where are Osteoclasts and Osteoblasts found respectively?

Answer 8

Osteoblasts - Growing portions of bone, including periosteum and endosteum

Osteoclasts - Bone surfaces and at sites of old, injured or unneeded bone

Question 9

• What are the organic and inorganic compositions of the bone matrix respectively?

Answer 9

Organic - 40%

Type 1 Collagen 90%

Ground Substance 10% - Proteoglycans, Glycoproteins, Cytokine and Growth Factors

Inorganic - 60%

Calcium hydroxyapatite

Osteocalcium phosphate

Question 10

• Describe the structure of immature bone

Answer 10

Laid down in a ‘woven’ manner - relatively weak, disorganised

Mineralised and replaced by mature bone

Question 11

• How would you describe the structure of mature bone?

Answer 11

Mineralised woven bone- organised

Lamellar (layer) structure - very strong

Question 12

• Describe the structures of the individual mature bone types (Cortical and Cancellous)

Answer 12

Cortical

• ‘Compact’ - dense
• Suitable for weight baring
• has osteons, few spaces, and provides protection support and resisting stresses

Cancellous

- 'Spongy' - honeycomb structure
- Not suitable for weight baring

Question 13

• Describe what an osteon is comprised of?

Answer 13

Concentric ‘lamellae’ around a central ‘Haversian Canal’

The 'Haversian Canal' contains blood vessels, nerves and lymphatics

Question 14

• What are Lacunae?

Answer 14

Small spaces containing osteocytes

Tiny Canaliculi radiate from lacunae filled with extracellular fluid

Question 15

• What are transverse perforating canals in the bone called?

Answer 15

Volkmans Canals

Question 16

• What is the Physis ?

- What happens here during interstitial growth?

Answer 16

aka the physeal plate - the Zone of elongation in long bone, which contains hyaline cartilage

Epiphyseal side - Hyaline cartilage active and dividing to form hyaline cartilage matrix
Diaphyseal side - Cartilage calcified and dies and then replaced by bone

Question 17

• In the femur, where does growth occur?

Answer 17

Proximal physis around the hip and the distal physis around the knee

Question 18

• What is appositional growth?

Answer 18

Deposition of bone beneath the periosteum to increase thickness

Question 19

• How does appositional growth occur?

Answer 19

Ridges in periosteum create a groove for periosteal blood vessel

Periosteal ridges fuse, forming an endosteum-lined tunnel

Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon

Bone grows outwards as osteoblasts in periosteum build new circumferential lamellae

Osteon formation repeats as new periosteal ridges fold over blood vessel

Question 20

• How do you classify the 3 joints?

-

Answer 20

Fibrous - Sutures, Syndesmosis, Interosseous membrane

Cartilaginous - Synchondroses (Spine), Symphyses (pubic)

Synovial - Plane, Hinge, Condyloid, Pivot, Saddle, Ball & Socket

Question 21

• Describe the structure of the synovial joint capsules

Answer 21

Articular capsules (Outer) - keeps bones together structurally

Synovial membrane (Inner) contains synovial fluid

Question 22

• What is the function of synovial fluid?

- How are synovial joints stabilised?

Answer 22

To reduce friction during movement

Bone surfaces - hip joint for example has a congruent bone surface so the ball and socket are very stable

Ligaments prevent bones moving in excess and in extreme directions to keep the joint in tact

also muscles/tendons

Question 23

• How does the shoulder joint’s stability compare with that of the hip?

Answer 23

Joint articulation- Mismatch-shallow socket, whereas the hip has a complete fit as it has a deep socket

Joint Capsule - Weak in shoulder, strong in hip

Ligaments - Lacks strong ligaments in shoulder, strong network of ligaments in hip

Muscles - Rotator cuff dependent with the shoulder but hip joint is supported by muscles in the hip

Stabilty - Unstable in shoulder, more stable in hip

Mobility - Extremely mobile in shoulder, less mobile in hip

Question 24

• Which type of cartilage is found in intervertebral discs?

Answer 24

Fibrocartilage

Question 25

• Which cartilage consists of chondrocytes and comprised of type II collagen interacting with proteoglycans and elastin?
• Which cartilage consists of chondrocytes and fibroblasts surrounded by type I collagen?

Answer 25

Elastic cartilage

Fibrocartilage

Question 26

• Which cartilage consists of chondrocytes surrounded by territorial and interterritorial matrices containing type II collagen interacting with proteoglycans?
• Which cartilages are surrounded by perichondrium?

Answer 26

Hyaline cartilage

Hylaine and elastic cartilage

Question 27

• Which cartilage is not surrounded by perichondrium?

- Are fibrocartilage, elastic and hyaline cartilage vascular or avascular?

Answer 27

Fibrocartilage

Avascular

Question 28

Explain how intramembranous ossifiation leads to the development of mesenchymal to bone?

Answer 28

1. Mesenchymal stem cells aggregate and form osteoblasts by differentiation
2. Ossification centre forms
3. Osteoblasts begin to secrete osteoid
4. Peripheral mesenchymal cells continue to differentiate
5. Osteoblasts secrete osteoid inwards towards ossification centre
6. Osteoblasts become trapped in osteoid causing differentiation into osteocytes
7. Osteoid calcifies and hardens after several days
8. Osteoid continues to be deposited, assembles in random manner around embryonic blood vessels
9. Finely woven trabeculae forms
10. Mesenchyme begins to differentiate int periosteum
11. Lamellar bone replaces woven bone at outer edge creating layers internal spongy bone remains
12. Vascular tissue within trabecular spaces forms red marrow
13. Osteoblasts remain on bone surface to remodel when needed