Intro To Bone And Soft Tissue

Question 1

What makes up the musculoskeletal system?

Answer 1

Bone

Muscle

Connective tissue - tendon, ligaments, cartilage

Question 2

How many bones in adults and children?

Answer 2

Children 270

Adults 206

Question 3

What are the Sri pets of the skeleton?

Answer 3

Appendicular: pectoral girdle, upper and lower limbs, pelvic girdle

Axial: cranium, vertebral column, rib cage

Question 4

What are the functions of the skeleton?

Answer 4

1. Support, helps to stand
2. Protection of vital organs
3. Movement, works with muscles to you can get around
4. Mineral storage, calcium and phosphate
5. Produces blood cells

Question 5

How do bones develop in utero?

Answer 5

Flat bones: intermembranous mesenchymal cells —> bone

Long bones: endochondral mesenchymal —> cartilage —> bone

Question 6

How does intramembranous ossification occur?

Answer 6

Mesenchymal to flat bones: skull, clavicle and mandible

1. Condensation of mesenchymal cells which differentiate into osteoblasts - ossification centre forms
2. Secreted osteoid traps osteoblasts which become osteocytes
3. Trabecular matrix and periosteum form
4. Compact bone develops superficial to cancellous bone. Crowded blood vessels condense into red bone marrow

Question 7

How does endochondral ossification occur?

Answer 7

Development of long bones from a hyaline cartilage model

1. Bone collar formation
2. Cavitation
3. Pereosteal bud invasion
4. Diaphysis elongation
5. Epiphyseal ossification

Question 8

What are bones made up of?

Answer 8

Cells

Matrix

Question 9

What are the bone cells?

Answer 9

Osteogenic cells - bone stem cells

Osteoblasts - bone forming, secrete osteoid, catalyse mineralisation of osteoid

Osteocyte - mature bone cells, forms when an osteoblast becomes embedded in its secretions, sense mechanical strain to direct osteoblast and osteoclast activity

Osteoclast - bone consuming, dissolve and resorb bone by phagocytosis, derived from bone marrow

Question 10

Where are each of the bone cells found?

Answer 10

Osteogenic - deep layers of periosteum

Osteoblast - growing portions of bone including periosteum and endosteum

Osteocytes - entrapped in matrix

Osteoclasts- bone surfaces and at sites of old injuries or unneeded bone

Question 11

What is the contents of the bone matrix?

Answer 11

Organic (40%) -

Type I collagen (90%) and ground substance (proteoglycans, glycoproteins, cytokines and growth factors) (10%)

Inorganic (60%) -

Calcium hydroxyapatite and osteocalcium phosphate

Question 12

What are the types of bone?

Answer 12

Immature bone: first bone produced. Layed down in a woven manner, relatively weak. Mineralised and replaced by mature bone

Mature bone: mineralised woven structure. Lamellar (layer) structure, relatively strong

Types of mature bone:

Cortical (lamellar)- ‘compact’ dense. Suitable for weight bearing

Cancallous - ‘spongy’ honeycomb structure. Not suitable for weight bearing. Has trabeculae (spikes) that form lots of air spaces

Question 13

What is an osteon?

Answer 13

The unit of bone found in compact bone. There are few spaces and it proves protection, support and resists stresses produced by weight of movement

Each osteon is made up of concentric lamellae around a central Haversian canal

Haversian canals contain blood vessels, nerves and lymphatics

Volkmans canals are transverse perforating canals that connect the Haversian canals

Lacunae are small spaces containing osteocytes

Question 14

What is the structure of long bones?

Answer 14

Periosteum - connective tissue covering

Outer cortex - compact bone

Cancellous bone - in the middle

Medullary cavity - ossification centre, contains yellow bone marrow

Nutrient artery

Articular cartilage on surfaces at joints only

Question 15

What are the plates at the end of bones?

Answer 15

Epiphysis - at very end

Physis- growth plate

Metaphysics

Diaphysis - long bit

Question 16

How do bones grow?

Answer 16

Interstitial - long bones increasing in length

Appositional - increase in thickness and diameter

Question 17

What is interstitial growth?

Answer 17

Long bone lengthening

Happens at the physis (physeal plate):

Zone of elongation of the bone

Contains hyaline cartilage

Epiphyseal side: hyaline cartilage active and dividing to form hyaline cartilage matrix

Diaphysis side: cartilage calcifies and dies, then replaced by bone

Question 18

What is appositional growth?

Answer 18

Deposition of bone beneath the periosteum to increase thickness

1. Ridges in periosteum create groove for periosteal blood vessel
2. Periosteal ridges fuse forming an endosteum lined tunnel
3. Osteoblasts in endosteum build new concentric lamellae inward towards centre of tunnel, forming a new osteon
4. Bone grows outwards as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new pereosteal ridges fold over blood vessel

Question 19

What is the role of bone in calcium homeostasis?

Answer 19

Bone strores 99% of total body calcium - calcium hydroxyapatite- structural support

Calcium is deposited and withdrawn during bone remodelling

Regulated by PTH and calcitriol (vitamin D)

Calcitonin (parathyroid cells) stimulates calcium uptake into bone

Question 20

How are joints classified?

Answer 20

Fibrous - sutures (skull), syndesmosis (tibia and fibia, radius and ulna) , interosseus membrane

Cartilaginous - synchondroses (spine), symphyses (pubic)

Synovial - plane, hinge, condyloid, pivot, saddle, ball and socket

Question 21

What is the structure of a synovial joint?

Answer 21

Most common and most mobile joints

Joint capsule:

• articulate capsule (outer) - keeps bones together structurally
• synovial membrane (inner) - contains and secreted synovial fluid into synovial cavity (this reduces friction during movement)

Question 22

How are synovial joints stabilised?

Answer 22

Bone surface congruity - well captured, very stable

Ligaments - made of collagen, stop bones moving in excess.

Muscles/tendons - help to stabilise joints

Question 23

How do ligaments affect joint stability?

Answer 23

Prevent excessive movement that could damage joint

More ligaments and tighter ligaments: more stability but less mobility

Fewer or laxer ligaments: more mobility but less stability

Poor stability —> risk of dislocation

Disproportionate, in appropriate or repeated stress to ligaments -> Injury

Excessive ligament laxity -> hyper mobility-> risk of injury

Question 24

What is a comparison of the hip vs shoulder?

Answer 24

Joint articulation: S(mismatch shallow socket) H(complete fit, deep socket)

Joint capsule: S(weak) H(strong)

Ligaments: S(lacks strong ligaments) H(strong network of ligaments)

Muscles: S(rotator cuff dependant) H(supported by muscles)

Stability: S(unstable) H(stable)

Mobility: S(extremely) H(less)