Bone Ultrastructure Flashcards
What tissue type is bone
Connective tissue
Bone function
Structure, protection, lipid and mineral storage, haematopoiesis
Three types of bone cells
Osteoblasts, osteocytes, osteoclasts
Osteoblasts…
Synthesise uncalcified ECM called osteoid
Osteocytes
Are matured osteoblasts entombed in the lamellae of lacunae and monitor proteins/minerals for bone mass
Osteoclasts
Mature monocytes which re absorb bone by the release of H+ and lysosomal enzymes
ECM of bone is … and is impregnated with… in particular …
Highly specialised … mineral salts … hydroxyapatite crystals
Hydroxyapatite crystals …
Associate with collagen fibres which makes bone hard
Bone Matrix is organised…
Organised into numerous thin layers called lamellae
Two types of bone
Woven bone (primary) and lamellar bone (secondary)
Primary bone
Woven bone
Secondary bone
Lamellar bone
Internal layer of bone
Endosteum
External layer of bone
Periosteum
Two subtypes of lamellar bone
Compact bone and spongy bone
In compact bone, lamellae is organised into…
Concentric circles
The lamellae in compact bone surround…
Haversian canals
The unit which contains osteocytes, lamellae and Haversian canals
Osteon
Haversian canals are connected horizontally by…
Volkmann’s canals
Haversian canals contain…
Neurovascular and lymphatic vessels, arteries and veins
Volkmann’s canals contain…
Small vessels which join the arteries of Haversian canals
Osteocytes are in…
Cavities called lacunae
Lacunae are connected by
Canaliculi
Spongy bone location
Interior of most bones
Bony matrix is a 3D…
A 3D network of fine columns which which cross link to form trabeculae
Trabeculae produces light…
Light porous bone which is resistant against multidirectional lines of force
Spaces between trabeculae are usually filled with…
Yellow bone marrow
Ossification is…
The process of making new bone
Endochondrial ossification
Hyaline cartilage is replaced by osteoblasts secreting osteoid
Example of a bone made by endochondral ossification
Femur
Intramembranous ossification
Mesenchymal tissue is condensed into bone
Bone example of intramembranous ossification
Flat bones such as the scapula
Remodelling is…
Where osteoblasts lay down osteoid where osteoclasts have reabsorbed bone
Osteogenesis imperfecta is…
Excessive synthesis of collagen from osteoblasts
Symptoms of osteogenesis imperfecta
Fragile bones - easier to fracture
Osteoporosis is…
The decrease in bone integrity due to an increased activity in osteoclast activity over osteoblast activity
Osteoporosis treatments
Bisphosphonates - taken up by osteoclasts to undergo apoptosis
Rickets is…
Poor osteoid mineralisation due to vitamin D deficiency- leads to distorted epiphyseal growth plates
Osteomalacia is…
Vitamin D deficiency in adults leading to poorly mineralised osteoid and therefore easier fractures
