During formation of these crystals, CaCO3, Na+, Mg++, & F- are incorporated
Hard & inflexible, Brittle
Resists to compression(will shatter when exposed to bending twisting, or suddent impacts)
Bone Anatomy: Matrix
Organic Component
33% of bone weight
Collagen Fibers (very small amount of cells)
Tough BUT flexible (stronger than steel)
Tolerates twisting & bending
Scaffolding for crystal formation
What is the Bone Matrix composed of?
INorganic component (67%)
Orgnaic component (33%)
Very Little Ground Substance
Functions of the Periosteum:
*Superficial Layer of compact bone that covers All bones(NOT within joint cavities)
Isolates the bone from the surrounding tissues
Provides a route for the circulatory and nervous supply
Actively participates in bone growth, remodeling and repair
Anchors bones to tendons & ligaments
BONE CYTOLOGY:
PERIOSTEUM (not found in joints)
Isolates bone from surround tissue
Provides route for vessels and nerves
Anchors bone to tendons and ligaments
Active in growth, repair, and remodeling
(NOTE: osteocytes are the only ones NOT found in periosteum)
Bone Cytology
Endosteum
Lines marrow Cavity and Central Cannal
Active in growth, repair and remodeling.
<incomplete CELLULAR layer)
(NOTE: osteocytes are the only ones NOT found in endosteum)
Bone Cell Physioogy:
Osteoprogenitors
Origin: mesenchymal cells
Location: Cellular layer of the persiosteum, endosteum and linings of canals
Function: stem cells of bone, differentiate into osteoblast.
Which of the following is NOT found in both the periosteum and endosteum:
A. Osteocytes (remember they are osteoblasts that get stuck in the MATRIX)
Bone Cell Physiology:
Osteoblasts
Origin: Osteoprogenitor Cells
Location: Periosteum and Endosteum
Functions: Osteogenesis: Production of bone matrix (fibers and ground substance)
Process: Initially, matrix is primarily organic (collagen)- OSTEOID (aka before calcium is deposited)
Calcium Phosphate is then deposited (which converts Osteoid to bone)
What is the organic matrix called before salts are deposited?
Osteoid
OSTEOCYTES develop from osteoblasts that have become completely surrounded by bone matrix
Which of the following is very important for repairing a fracture?
C. Osteoprogenitors (remember: its a stem cell)
Which of bone cells elevate the concentration of calcium phosphate above its solubility limit triggering the deposit of calcium salts in the organic matrix... which converts osteoid to bone?
Osteoblasts (remember blast-precursor aka a producer)
Bone Development:
Bone skeleton starts to form 6 weeks after fertilization
Before this+ Cartilage
Portions do not stop growing until ~25 years
"Remodled" for lifetime
Process of replacing tissue with bone
Ossification
2 Types of Ossification:
1. Endochondral Ossification : Most Bones (long bones), Bone replaces existing cartilage
2. Intramembranous Ossification: Flat Bones, Develops from fibrous connective tissue or meschyme
Calcification:The deposition of calcium-salts occurs during ossification, but it can also occur in other tissues.
Fibrodysplasia Ossificans Progressive (FOP)
Rare Genetic disease that from form normal bone in the wrong places after minor injury and provide the most dramatic demonstartions of heterotopic bone formation