Bone Flashcards
Functions of bone (5)
Support
Protection
Levers for muscles
Reservoir for minerals (Ca2+ and P)
Houses marrow cavity which is responsible for hemopoiesis
Aceullar components of bone (2)
Inorganic
Organic
Inorganic component of bone
Ca2+ and P in the form of hydroxyapatite crystals (65% dry wt)
Organic component of bone
Almost exclusively Type I collagen (35% of dry wt)
Cellular components of bone (4)
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Where can you find osteoprogenitor cells
Located in periosteum, Haversian canals, and endosteum
Osteoblasts are derived from
osteoprogenitor cells
Osteoblasts function
Make/secrete osteoid (organic cmpd of ECM)
Osteocytes derived from
Osteoprogenitor cells
When osteoblasts become enveloped in osteoid they
Become osteocyte
Osteoclasts are derived from
monocyte/MQ
Osteoclasts are involved with
Resorption of bone (remodeling)
T/F Osteoclasts are motile
T
2 layers of periosteum
Outer dense fibrous CT layer
Inner cellular layer (where osteoprogenitor cells are)
Endosteum
- what is it
- what is it made of
Central cavity of bone with specialized thin CT layer
Made of osteoprogenitor cells and osteoblasts
Types of bone (2)
Woven (immature)
Lamellar (mature)
Woven bone (immature)-1sts
1st type of bone made during skeletal development and 1st type of bone to be laid down during fracture repair
Woven bone phenotype
Mottled appearance of matrix
Large osteocytes
Random orientation of cells
2 types of lemellar bone (mature)
Compact
Spongy (cancellous)
What system is observed in compact bone
Haversian system
What is the smallest functional bone unit
Osteon
Haversian canal contains
Blood vessels, nerves, endosteal cells
What are the vascular spaces that connect adjacent Haversian canals
Volkmann’s canals
Fibrocartilage in intervertebral discs are caused by
FGF4 retrogene insert in chondrocytes to cause inappropriate activation of FGFR3
2 diff bone histogenesis
Endochondral ossification
Intramembranous ossification
Endochondral ossification process seen in what type of bones
Long (wt bearing) bones
Endochondral ossification requires
Hyaline cartilage template
Intramembranous ossification seen in what type of bones
Flat and short (non wt bearing) bones
Intramembranous ossification results in what for long bones
Thickening of long bones
Intramembranous ossification formation of bone directly from/within
Fibrous CT membranes
Origin of cartilage (3 steps)
Condensation of primordial mesenchymal cells
Mesenchymal cells differentiate into chondroblasts and exhibit interstitial growth as they are separated by their own secretory products
Periochondrium formed-hyaline cartilage model continues to grow by appositional and interstitial growth
T/F All long bones in an embryo start out as a hyaline cartilage template
T
T/F Bone replaces cartilage everywhere on bone
F
Except where there’s a joint formation
T/F Growth in thickness of bones is only by interstitial growth
F
Appositional growth
Process of bones growing in thickness
- What differentiaties
- What forms
APPOSITIONAL GROWTH
Periosteal osteogenic cells differentiate into osteoblasts which secrete ECM
Ridges fuse and periosteum becomes endosteum
New concentric lamellae are formed
Osteoblasts under periosteum form new circumferential lamellae
Growth in length of bones incorporates
epiphyseal growth ( a results of cartilage growth)
Zones of growth in length (4) from earliest to latest
Zone of reserve cartilage
Zone of proliferation
Zone of maturation and hypertropy
Zone of calcification and ossification
3 phases of bone repair
Inflammatory
Reparative
Remodeling
Inflammatory phase of bone repair (2)
Hematoma formation
Ischemic necrosis of bone
Reparative phase of bone repair (3 stages)
Hematoma invaded by small capillaries to form granulation tissue then by osteoprogenitor cells forming a fibrocartilaginous callus and later bony callus
- ->there’s stabilization
- ->size of callus related to amt of movement
Early woven bone formation and/or cartilage formation
Eventual replacement of cartilage with woven bone
Remodeling phase of bone repair (3 stages)
Woven bone replaced by lamellar bone
Bony callus reabsorbed
Repaired zone restored to original shape and strength
Red marrow vs yellow marrow
Red-hematopoietic cells (younger animals)
Yellow-adipose tissue (older animals)
The outer dense fibrous CT layer of periosteum contains (3)
fibroblasts
blood vessels
collagen
Osteoclasts lacunae
Howship’s lacunae
How osteoclasts help with resorption (3)
Resorb bone via
Carbonic anhydrase-reabsorb inorganic cmpds (Ca2+, P)
Lysosomal enzymes and meralloproteinases- resorb organic cmpds
Endochondral ossification
What’s the first bone tissue that appears?
How is it formed
Bone collar via intramembranous ossification
Endochondral ossification
what happens in the primary center of ossification (3)
1-Periochondrium becomes vascularized and becomes periosteum
2-Chondrogenic cells turn into osteoprogentor cells which turn into osteoblasts and secrete bone matrix forming bone collar
3-Chondrocytes in diaphysis die and form a cavity, Cavity is invaded by blood vessels and allows development of red marrow
Endochondral ossification
What happens at secondary center of ossification
-Osteoprogenitor cells invade cartilage of epiphysis and turn into osteoblasts that secrete bone matrix on cartilage model but NO BONE COLLAR MADE
What is different between secondary center of ossification and primary?
No bone collar made in secondary
Hyaline cartilage remains at surface (articular cartilage) and at growth plate at secondary.
Epiphyseal growth contributes to length or width of bone growth
Length
In intramembranous ossification, the portino of CT that does not undergo ossification…
Gives rise to endosteum and periosteum of intramembranous bone.
