Bone tissue

Question 1

main functions:

Answer 1

• mechanical support
• movement, protection
• fat and mineral storage (cal, phos.)
• encloses red bone marrow (hemopoiesis- production of blood cells)

Question 2

primary bone tissue: features

Answer 2

(immature/ woven)

• temporary -> replaced by mature
• irregular array collagen fibres
• low mineral content
• high proportion of oseteocytes

Question 3

secondary bone tissue: features

Answer 3

(mature, lamellar)

- collagen fibres arranged in lamellae (thin plate-like structure)

Question 4

main parts of long bone:

Answer 4

• diaphysis (shaft) with medullary cavity
• epiphysis (ends)
• metaphysis (middle) with epiphyseal plate

Question 5

(a)vascular? for? major blood supply in long bone

Answer 5

• highly vascular, allow growth and change
• epiphyseal A
• metaphyseal
• nutrient (distal/ proximal) - mid shaft
• periosteal

Question 6

osteogenic cell: features/ location

Answer 6

unspecialised stem cell, can undergo cell division
- for growth/ remodelling

• inner portion of periosteum, endosteum, blood vessel canals

Question 7

osteoblast cell: features/ location

Answer 7

• for synthesis of organic extracellular matrix, influence inorganic components’ deposition
• only on the cell surface (cuboidal/ columnar/ squamous)
• when completely surrounded by matrix = osteocyte

Question 8

osteocyte cell: features/ location

Answer 8

• maintain bone matrix
• respond to mechanical forces, lay down new/ remove matrix
• in lacunae (cavities) within/between lamellae
• communicate to other osteocytes via canaliculi (small canals) -> processes travel through

Question 9

osteoclasts: features/ location

Answer 9

• stimulated by the parathyroid hormone (indirectly) and inhibited by calcitonin (thyroid gland)
• bone resorption (breaking down)
• uses lysosomes -> matrix
• large, multinucleated, motile, phagocytic, ruffled border (invaginations)
• fusion of monocytes/ macrophages
• attached to bone matrix (tight seal)

Question 10

compact bone structure: general features

Answer 10

Haversian system/ osteon

• cylindrical unit (concentric lamellae bone matrix) around central canal
• osteon parallel to long axis of bone
• 1-2 capillaries, lymph vessels and nerves

Question 11

compact bone structure: between/surround Haversian systems features

Answer 11

between: interstitial lamellae/ outer-circumferential

surrounded by cementing substance: mineralised matrix, few collagen fibres

Question 12

compact bone structure: Volkmann’s canals

Answer 12

perpendicular to Haversian canals, transversely from periosteum -> endosteum, connecting osteons
- blood vessels

Question 13

spongy bone structure: features

Answer 13

• no osteons, lamellae in irregular lattice of thin columns (trabeculae)
• spaces in btw contain red and yellow bone marrow
• each trabecula-> osteocytes (in lacunae)
• blood supply directly form surrounding blood vessels

Question 14

difference between periosteum and endosteum: features

Answer 14

Periosteum:

• tough sheet, outer surface of bone (excl. art cartilage)
• outer (fibrous) layer DICT
• inner layer: osteogenic

Endosteum:

• thin membrane, lines internal cavities within bone
• single layer: bone-forming cells, lil ct.

Question 15

bone formation: before birth

Answer 15

intramembranous and endochondral

Question 16

bone formation: after birth

Answer 16

length and width

Question 17

features: intramembranous growth

Answer 17

flat bones of skull (parietal, frontal), mandible

• apposition (growth) on tissue within embryonic connective tissue membrane (mesenchyme)
• bony tissue will develop directly from mesenchyme

Question 18

intramembranous growth: development stages (formal)

Answer 18

development of ossification centre –> calcification –> formation of trabeculae –> development of periosteum (stimulates compact bone)

Question 19

endochondral ossification: features

Answer 19

• cartilage first -> replaced with bone

- more common

Question 20

endochondral ossification: stages of development (formal)

Answer 20

(cartilage model) hyaline cartilage covered in perichondrium (DICT layer) -> interstitial/ appositional cartilage model growth –> periosteum develops (primary ossification centre) —> dev. medullary cavity –> dev. secondary ossification centres –> formation of articular cartilage and epiphyseal plates

Question 21

intramembranous growth: development stages (informal explanation)

Answer 21

mesenchyme differentiates: osteoblasts, activated -> patches of bone matrix- ossify, merge= trabeculae (spongy bone), blood vessels help, periosteum forms (new osteoblasts outside)-> make compact bone

Question 22

endochondral ossification: stages of development (informal explanation)

Answer 22

mesenchymal cells: differentiate later in chondrocytes–> calcify and kill cells, nutrient artery (feeds inside) cells differentiate= osteoblasts –> make bony matrix, (primary ossification centre) –> moves towards ends of bones (epiphyses)

secondary ossification centre- ossification from surface which penetrates deeper –> cartilage will only stay at metaphysis

Question 23

growth in width: features

Answer 23

appositional growth (new layers) of bone tissue on pre-existing bone surface (under periosteum) = increase in width
- osteoclasts also on endosteum surface remove bone -> expand medullary cavity

bone growth always regulated

Question 24

growth in length: features

Answer 24

interstitial growth (length) via formation of new cartilage within existing cartilage mass

Question 25

growth in length: epiphyseal plate zones

Answer 25

- resting cartilage: connects cartilage to bone (epiphysis) - proliferating cartilage: new chondrocytes- matrix grows/ stack cartilage, push closer to bone side- will die - hypertrophic cartilage: mature chondrocytes enlarge leaving large spaces - calcified cartilage: where cartilage is replaced with bone tissue leaves epiphyseal line

Question 26

danger of bone fracture in children:

Answer 26

- this cartilage-> bone growth will stop during teens once all cartilage is replaced - fracture prematurely disrupts growth/ blood supply = early ossification (shorter)

Question 27

bone remodelling: how?

Answer 27

- stress to periosteum of bony prominences --> osteoblasts activation (stimulate more bone tissue) - stronger bones - create more ridges for muscle attachment - no stress= loss of bone tissue

Question 28

Wolff's law

Answer 28

bone is healthy person/ animal will adapt to the loads it is placed under

Question 29

eg of bone remodelling:

Answer 29

Patagonia skull modelling - bandaging skulls - culturally beautiful

Question 30

bone repair:

Answer 30

fracture: - Heamatoma (blood collection outside bl. vessel) - swollen - -> once cleaned up temporary fibrocartilaginous callus forms (quick framework) - -> replaced by bony callus, osteoclasts clean up - -> bone remodelling (try to fix bump)

Question 31

osteoporosis:

Answer 31

more likely in older female - after menopause, sharp decline of oestrogen - brittle bones, easier to break bones - really slow recovery - Vitamin D and calcium good, active lifestyle too