The Skeleton

Question 1

What are the 5 primary functions of the skeleton?

Answer 1

• Support, also attachment of soft tissues & organs
  
  • Storage of minerals & lipids e.g. Ca, lipids stored in yellow bone marrow
  • Blood cell production e.g. RBC, WBC produced in red bone marrow
  • Protection e.g. brain, spinal cord (extension of brain)
  • Leverage – alter the magnitude & direction of forces produced by skeletal muscles- movement of arms is possible because of muscles which allow the bones to move

Question 2

What components make up the bone matrix?

Answer 2

• Ca3(PO4)2 make up 2/3 bone weight
  
  • Interacts with Ca(OH)2 to form hydroxyapatite crystals
  • Collagen fibres make up 1/3 bone weight collagen is in skin but in the bone it is a framework that the hydroxyapatite crystals bind to
  • Collagen provides an organic framework on which hydroxyapatite crystals can form
  • Periosteum covers outer surface of bones

Question 3

Name the four types of bone cells.

Answer 3

-Osteoblasts
-Osteocytes
-Osteogenic cells
-Osteoclasts

Question 4

What are osteocytes?

Answer 4

-Mature bone cells, each occupying a lacuna (pocket sandwiched between layers of matrix)
-Do not divide- terminally differentiated
-Canaliculi are narrow passageways through the matrix which extend between the lacunae and blood vessels
-Forms a network for exchange of nutrients, waste products etc.

Question 5

What is the function of Osteocytes?

Answer 5

To maintain protein & mineral content of surrounding matrix and repair damaged bone

Question 6

What are osteoblasts?

Answer 6

-Stem cells
-Immature precursor cell
-Osteocytes develop from osteoblasts which have become surrounded by
matrix

Question 7

What is the function of osteoblasts?

Answer 7

Produce new bone matrix – ossification or osteogenesis

Question 8

What are osteogenic cells?

Answer 8

They are progenitor cells
-Stem cells which divide to produce osteoblasts
- found in the inner layer of the periosteum

Question 9

What is the function of osteogenic cells?

Answer 9

·Maintain populations of osteoblasts

Question 10

What are the functions of osteoclasts?

Answer 10

· Absorb & remove bone matrix
· Release acids & enzymes which dissolve matrix & release stored minerals
· Osteolysis- breaking down of bones
· Regulation of Ca & PO4 concentrations in body fluids

Question 11

Repair of bones- Haematoma formation

Answer 11

Extensive bleeding occurs, haematoma closes off injured vessels, fibrous meshwork produced

Question 12

Repair of bones- Callus formation

Answer 12

Internal callus (fibrous tissue and cartilage) unites edges of fracture, external callus (cartilage and bone) stabilises outer edges. The callus tries to unite the bits of bone depending on the degree of displacement the new bone can try unite the two broken bits.

Question 13

Repair of bones- spongy bone formation

Answer 13

Osteoblasts replace external callus with spongy bone, ends of fracture are stable & can withstand normal muscle contractions. Can be laid down quickly when normal bone is formed properly you can then have normal functions.

Question 14

Repair of bones- Compact bone formation

Answer 14

Fracture area is remodeled by osteoblasts & osteoclasts, repair is as strong or stronger than original bone. Repair is stronger than original bone unlikely to break that point again it is replaced with tissue stronger than the original.

Question 15

What is the axial skeleton composed of?

Answer 15

Bones of the head and trunk
· 80 of them
· Skull – 8 cranial & 14 facial
· Bones associated with the skull – 6 auditory ossicles & hyoid bone (only bone not attached to any other bone- base of tongue)
· Vertebral column – 24 vertebrae, sacrum (base of spine) & coccyx (where tail is attached)
· Thoracic cage – sternum & 24 ribs
· Framework that supports and protects brain, spinal cord, thoracic and abdominal organs
· Extensive surface area for attachment of muscles
· Joints are very strong with limited movements – many ligaments- join bones together at joints

Question 16

What are sinuses?

Answer 16

Sinuses are air-filled chambers
→ 3 major functions
· Lessen the weight of bone
· Mucus membrane lining them produces mucus that moistens and cleans the air
· Resonating chambers in speech production
· Joined to nasal cavity by ostia (ostium)
· Easily blocked by allergic inflammation or swelling of nasal lining
(cold) because there isn’t a good circulation of air through your sinuses it can then become infected.
· Drainage affected leading to sinusitis

Question 17

What is the appendicular skeleton composed of?

Answer 17

· Bones of the limbs & bones that connect them to the body
· 126 of them
· Allows manipulation of objects & movement
· Dominated by long bones basically all the bones in your arms and legs

Question 18

What are synovial joints?

Answer 18

· Joint capsule surrounds synovial joint
· Synovial membrane, articular cartilage & synovial fluid
· Articular cartilage (composed of collagen) cover articulating surfaces – smooth surface
· Reduces friction during movement
· Synovial fluid acts as lubricant & shock absorber
· Accessory ligaments support & strengthen synovial joints- holds it together
· Tendons passing around joints also provide support
· Bursa are small, fluid filled pockets containing synovial fluid where a ligament might rub a bursa would be there to prevent it.
· Form where tendons/ligaments rub against other tissues
· Reduce friction

Question 19

Name the 6 types of synovial joints

Answer 19

-gliding/plane
-hinge
-condylar
-saddle
-pivot
-ball and socket

Question 20

What conditions are a result of degenerative changes in joints?

Answer 20

-arthritis
-damage to articular cartilage
- Osteoarthritis
-Rheumatoid arthritis

Question 21

What is the structure and function of ligaments?

Answer 21

· Fibrous connective tissue that connects bones to other bones
· Type 1 collagen
· Stabilise joints – limiting or preventing movements
· Ligaments are viscoelastic - they gradually strain when under tension
and return to their original shape when the tension is removed e.g. elastic band analogy
· If damaged, ligaments cannot usually be fully regenerated naturally very slow process replaced by type 4 collagen, different pattern of collagen it is really strong but it’s not elastic
· Scar tissue will limit effectiveness

Question 22

What is the structure of tendons?

Answer 22

Fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension
-Type 1 collagen
-Tendinopathies