bone A&P Flashcards
6 main functions
support mush
protect (organs etc)
assist movement
mineral homeostasis (Ca2+, P)
blood cell create
(Red bone marrow = RBC, WBC, platelet)
store fat
(yellow bone marrow)
anatomy of long bone
Diaphysis (shaft)
Epiphysis (head/end)
(distal/proximal epiphysis)
Metaphysis (neck)
where is yellow bone marrow?
in diaphysis
what is diaphysis made of? (what type of bone?)
compact bone (cortical bone)
compact vs cancellous bone (spongy bone)
Epiphysis primarily
cancellous bone (spongy bone)
where is red bone marrow?
in epiphysis
structural characteristic of epiphysis
projections and fossae
I.e. forming joints
In other words, around joints are red bone marrow (?)
metaphysis
between diaphysis and epiphysis (Zone of transition)
WEAKEST
where is epiphyseal plate
in metaphysis
what is epiphyseal line
epiphyseal plate becomes epiphyseal line at around 20y.o. when growth (height) stops
epiphyseal plate is area of cartilage where bone growth appears
medullary cavity
cavity in diaphysis
contains YBM
contains blood vessels
endosteum
lines the medullary cavity
what is endosteum made of? (tissue type?)
DENSE IRREGULAR CT
periosteum
surrounds bone
two layers of periosteum
fibrous layer (Dense irr CT)
cellular layer
function of periosteum
covers bone
merges with tendons
sensory nerves
blood vessels
cellular layer holds OSTEOPROGENITOR CELLS (precursors to osteoblasts)
articular (hyaline) cartilage
covers epiphysis
reduce friction
reminder: CT is made of
CT is made of…
a) specialized cells
b) ECM (ground substance + fibres)
histology of bone
GS in bone is very hard
4 main types of cells:
osteoprogenitor
osteoblast
osteocyte
osteoclast
ECM of bone (fibres + GS) – Fibres
Collagen fibres (30% bone weight)
= flexibility of bones
ORGANIC COMPONENT OF ECM
ECM of bone (fibres + GS) – GS
crystalized mineral salts
only enamel is harder
CALCIUM PHOSPHATE
55% bone weight
HYDROXYAPATITE salts
Calcium phosphate
+
Calcium HYDROXIDE
Also incorporates other salts (e.g. calcium carbonate)
and ions (Na+, Mg2+, F-)
INORGANIC COMPONENT OF ECM
ground substance in bone
made of HYDROXYAPATITE
extremely hard
4 bone cell types
osteoprogenitor
osteoblast
osteocyte
osteoclast
osteoprogenitor
stem cells derived from mesenchyme
only bone cells that undergo MITOSIS
develop into OSTEOBLASTS
Part of deep (cellular) layer of periosteum AND ENDOSTEUM
osteoblast
bone building
on bone surface
secrete COLLAGEN
form osteoid
TURN OSTEOID into BONE
osteoid
“Osteoid is an unmineralized organic tissue that eventually undergoes calcification and is deposited as lamellae or layers in the bone matrix.”
TURN OSTEOID into BONE
“assist in depositing the mineral salts (initiate calcification) to turn osteoid into bone”
osteocytes
mature bone cells
inside bone tissue
DENDRITIC processes
nutrient/waste exchange
(METABOLIC ACTIVITY OF BONE)
which bone cell type maintains metabolic activity?
osteocyte (mature bone cells)
where are osteocytes contained
in LACUNAE
where are lacunae?
between concentric layers of LAMELLAE
Interconnected via CANALICULI
Osteoclasts
break down (resorb) bonew
what is resorption
taking Ca2+ from bone
put it back in blood
(OPPOSITE TO OSTEOBLASTS)
what are osteoclasts derived from (common origin)
Macrophage (WBC that performs phagocytosis)
which cells are multinucleated?
Osteoclasts
where are osteoclasts?
also found on surface of bone
grooves called HOWSHIP’S LACUNAE
two types of bone tissue
compact
spongy (cancellous/trabecular)
why compact
“structure comprising mostly of calcium, phosphate, collagen, and other minerals “
No SPACE between cells
where compact?
diaphysis
external layer of all bones
3 types of LAMELLAE in bone matrix
concentric lamellae
interstitial lamellae
circumferential lamellae
Osteon
individual structural units of bone
made via concentric lamellae
haversian/central canal
at centre of concentric lamellae
note lacunae and canaliculi
note osteocytes via lacunocanalicular network
interstitial lamellae
between osteons
circumferential lamellae
next to medullary cavity
next to periosteum
not part of osteon
haversian canals
longitudinally along shaft of bone
blood vessels
lymph vessels
nerves
Volkmann’s canal (PERFORATING canals)
perforating canals
perpendicular
interconnect haversian/central canals
(bv/lymph/nerve
superficial to deep
note about canaliculi
filipodia of osteocytes
FILIPODIA
Spongy bone (trabecular/cancellous)
no osteon units – no haversian system
which bone GREATER BLOOD SUPPLY
spongy
Red bone marrow
= RBC, WBC, platelets
trabeculae
contain lamellae of spongy bone
less organized
weaker
where spongy? …
epiphyses of long bones
flat bones – periosteum and thin layer of compact bone – but primarily spongy at centre/core
ossification/osteogenesis
“bone formation”
begins during 6th week of embryo development
2 types of bone formation
endochondral ossification (replacement of cartilage w/ bone)
intramembranous ossification
(replacement of connective tissue membranes with bone tissue)
ENDOCHONDRAL ossification
initial skeleton of embryo = hyaline cartilage
cartilage replaced via endochondral ossification
cartilage is “small model”
occurs in LONG BONES
where endochondral ossification?
long bones