Bone Flashcards
Function of bone (5)
- support
- movement
- protection
- calcium homeostasis
- storage
haematopoiesis
formation of blood cellular components
haematopoiesis location
takes place in bone marrow. specifically red
Types of bone
- sutural
- pneumatised
- flat
- short
- long
- irregular
- sesamoid
sutural bones
- Small, flat, oddly shaped
- Found between flat bones of skull in the suture line
- Develop from separate centres of ossification
- Type of flat bone
Flat bones
- Contain thin, roughly parallel surfaces of compact bone
- Resembles spongy bone sandwich
- Strong but light
- Roof of the skull, sternum, ribs and scapulae
- Provide protection for soft tissues and extensive surface area for attachment of skeletal muscles
- Thick layers of compact bone = internal and external tables
Layer of spongy bone between = diploë
Pneumatised bones
- hollow
- contain numerous air pockets
- ethmoid (nose)
short bones
- Boxlike
- External surfaces covered by compact bone
- Interior contains spongy bone
- Carpal bones (wrists)
- Tarsal bones (ankles)
long bones
- Long and slender - Contain a diaphysis, 2 metaphysis, 2 epiphyses and a medullary cavity
- Found in upper and lower limbs
e.g. humerus, radius, ulna, femur, tibia, fibula
irregular bones
- Complex shapes with short, flat, notched or ridged surfaces
- Varied internal structure
- Vertebrae, bones in the skull
sesamoid bones
- Small, round and flat
- Develop inside tendons
- Mostly located in joints at the knee/hands/feet
- kneecaps
order of sections of bone from top to centre
epiphysis -> metaphysis -> diaphysis
articular surface
located on epiphysis, provides smooth lubricated surface for articulation
order of sections of bone from outside in
articular cartilage -> periosteum -> compact bone -> endosteum -> trabecular bone -> medullary cavity
periosteum
- Is a tough, vascularised fibrous sheath
- Superficially covers parts of the bone where there is no cartilage
- Nourishes and protects the bone
- Forms an attachment site for ligaments and tendons
- Superficial layer high on fibres
- Deep layers have osteogenic (bone forming) cells for bone repair
Endosteum
- A thin membrane that lines medullary cavity
- Single layer of bone forming (osteoprogenitor) cells
- Sparse matrix of collagen fibres
medullary cavity
- a hollow cavity containing bone marrow
- minimises the weight of the bone where it is least needed
organic matrix of bone
- 35%
- type 1 collagen
- Proteoglycans and glycosaminoglycan
- Glycoproteins: osteonectin and osteocalcin
inorganic matrix of bone
- 65%
- calcium phosphate -> hydroxypatite
- hardness, compressive strength
osteocyte
mature bone cell that maintains and monitors the protein and mineral content of the matrix, signals stress
osteoprogenitor cell
a stem cell that differentiates from mesenchyme and divisions of which produces osteoblasts
osteoblast
immature bone cell that secretes organic components of matrix in the process of osteogenesis
osteoclast
a large, multinucleate cell derived from monocytes which secretes acids and enzymes to dissolve bone matrix in the process of osteolysis
woven bone
- Immature bone
- Random arrangement of collagen fibres
- First formed during foetal development or repair of fracture
- Remodelled into lamellar bone
lamellar bone
- Mature bone - virtually all bone in healthy adults
- Either compact or spongy
- Concentric bands of collagen
- Fibres are oriented in one direction in each layer, but each layer is in different directions -> increase in strength
Osteon
- functional unit consisting of concentric lamellae
contains: - lacunae
- canaliculi
- haversian canals
- Volkmann canals
lacunae
spaces between concentric lamellae
canaliculi
small extracellular fluid filled channels radiating from lacunae, link lacunae
haversian canals
- central canals
- neurovascular
Volkmann canals
- perforating canals
- provide channels for neurovascular structures between adjacent osteons, periosteum and marrow`
spongy bone
- Also known as cancellous or trabecular bone
- Composed of a latticework of thin plates of bone called trabeculae, oriented along lines of stress
- Spaces in between the struts are filled with red marrow
- It is found in the ends of long bones with inside flat bones such as hip bones, sternum and ribs
- Although the concentric lamellae within resembles that of an osteon, there are no true osteons in spongy bone
concentric lamellae
tubes of different size fitting inside each other to make an osteon
2 methods of bone formation
- intramembranous ossification
- endochondral ossification
intramembranous ossification
- Ossification within a membrane
- Special cells secrete a protein matrix that later mineralises
- Primarily flat and irregular bones (facial bones, skull, clavicle)
endochondral ossification
- The replacement of hyaline cartilage by bone
- Mesenchyme turns into cartilage that is later replaced by bone
- Majority of bones in skeletal system
- Normally associated with growth in length
