7.2 Flashcards
Bone Matrix
*70% made of salts & most are called hydroxyapatite
*also includes collagen
*Ca2+ levels (homeostatic level) in the blood determine the formation and resorption of bone tissue
Low blood Ca2+
parathyroid hormone released that stimulates osteoclasts
High blood Ca2+
calcitonin released stimulating osteoblasts
Homeostasis in bone matrix
*collagen fibers add strength and resilience
*salts make bone hard
Compact Bone
*made up of osteons (Haversian system)
*In higher abundance in long bones & has no gaps in the matrix
-helps to resist compressive forces
Osteons
Cylinder-shaped units
Osteon Anatomy
*Central Canal
*Lamellae
*Lacunae
*Canaliculi
*Perforating Canals
Central Canal
Central tubular portion runs length (up and down) of the bone
Perforating Canals
*Transverse tubes that connect all central canals (run left to right)
*Allows for connection with the surface & medullary cavity
*Blood, lymph and nerve vessels from the periosteum penetrate the compact bone through this
Lamellae
Rings of hard calcified matrix laid down by osteoblasts
Lacunae
Spaces within the lamellae that contain osteocytes
Canaliculi
Small tubes in the extracellular matrix that connect osteocytes to each other and blood suppy
Spongy bone
*Does not contain true osteons
*No central canals, perforating canals, lamellae
*Does have lacunae and canaliculi
*Composed of Traveculae
*Most prevalent in short, flat and irregular bones
*Is also in the epiphysis of long bones
Trabeculae
Composed of branching, irregular bony plates
From superficial to deep (in diaphysis)
*periosteum
*compact bone
*endosteum
*spongy bone
*Medullary cavity
