bone Flashcards
Definition of Bone
connective tissue characterized by a mineralized ECM
What is the ECM of bone
hydroxyapatite crystals
type 1 collagen
small amt of type 5
glycoproteins (ostecalcin,nectin and pontin)
Cells of BONE
osteocyte
osteoblast
osteoprogenitor cells
osteoclast
What is the function of bone
support
protection
storage site for calcium and phosphate
Endosteum
covers the inner surface of the marrow cavity and contains osteoprogenitor and endosteal cells that become osteocytes
Components of bone
bone tissue hemopoietic tissue fat tissue dense connective tissue vessels and nerves endosteum
examples of long bones
diaphysis, epiphysis, metaphysis, tibia and metacarpals
examples of short bones
carpal bones
examples of flat bones
skull cap and sternum
examples of irregular bones
complex shape like vertabra
haversian lamellae
concentrical lamellae surrounding a haversian canal that forms cylindrical units called osteon; haversian canals contain vessels and nerves
lacunae are between the lamellae with osteocytes
canaliculi penetrate lamellae with osteocytic processes
interstitial lamellae
between osteon space filled with old haversian systems (remodling bone)
outer circumferential lamellae
lining the outersurface of the bone under the periosteum
inner circumferential lamellae
lining the inner surface of the bone under the endosteum
Where is immature bone found
developing fetus, alveolar sockets, tendon attachments
characteristics of immature bone
nonlamellar more cell rich than mature bone cells randomly organized matrix is less mineralized and has more ground substance than mature bone stains more basophilic
What is periosteum
collagenous membrane on the outersurface of the bone
carries vessels and nerves which contain nocireceptros
what are the two layers of the periosteum
outer fibrous layer that has dense irregular connective tissue
inner osteogenic layer: osteoprogenitor cells
endosteum
covers the marrow cavity composed mostly of osteoprogenitor cells
characteristic of osteoprogenitor cells
resemble fibroblasts
basophilic
located in the inner layer periosteum, endosteum and line the haversian and volkmanns canals
can divide and differentiate to osteoblasts and other things
participate in appositional bone formation
osteoblasts
secretory cells capable of division
secrete ground substance and collagen
basophilic cytoplasm-RER
form a single cuboidal cell layer on surface of bone
secrete vesicles containing alkaline phosphatase
when an osteoblast is surrounded by an osteoi it is called a
osteocyte
osteocytes
surrounded by osteoid or mineralized bone
matains matrix
communicate via gap junctions and occupy canaliculi
inactive osteocytes
few organelles
formative osteocytes
RER
resorptive osteocytes
lysosomes
osteoclast
multinucleated acidophilic cells originate from monocytes nuclei on side ruffled border rest in a resorption bay decalcify bone with lysosomal hydrolases PTH increases osteoclast activity
intramembranous ossification occurs when
fractures and embryo skull bone
Endochondral ossification
starts with hyaline cartilage modle
perichondrium forms bony collar
primary ossification center develops
chondrocytes become hypertrophic and secrete alkaline phosphatase
inhibits diffusion of nutrients so death of suicidal cells
death of chondrocytes-matrix breaks down to form a cavity
capillary loop breaks into bone carrying osteoprogenitor cells that settle on surface of cartilage trabecules–osteoblasts
osteoblasts build bone
secondary ossification centers
capillary loop breaks into the epiphysis
how does bone increase in diabeter
appositional growth
