Chapter 6 - The Skeletal System: Bone Tissue Flashcards
Functions of bone
- structural framework
- protects organs
- assistance in movement
- mineral storage (calcium and phosphorus)
- hemopoeisis
- triglyceride storage
Hemopoeisis
- production of red blood cells, white blood cells, and platelets
- occurs in red bone marrow
Structure of a long bone
- diaphysis
- epiphyses
- metaphyses
- periosteum
Diaphysis
- medullary cavity (middle of bone)
- endosteum (layer of bone forming cells around medullary cavity)
Epiphyses
- ends of bone
- covered by articular cartilage
Metaphyses
-epiphyseal plate vs. epiphyseal line
Epiphyseal plate
- before maturation
- cartilage allows growing in length, damage of both plates stops growth
Epiphyseal line
after maturation
Periosteum
- layer of bone forming cells
- growth in thickness, protects bone, fracture repair, nourishes bone tissue, attachment point for ligaments
- everything on outer bone not covered by cartilage
Osteogenic cells
- stem cells
- undifferentiated; divide; develop into osteoblasts
- found in periosteum and endosteum
Osteoblasts
- immature bone cells
- secrete collagen fibers and extracellular matrix
- trapped in secretions to become osteocytes
Osteocytes
- mature bone cells
- main cells of bone; maintains metabolism
Osteoclasts
- resorption (breakdown of bone extracellular matrix
- endosteum
Extracellular matrix
- water (15%)
- collagen fibers (30%)
- hydroxyapatite (rest)
Hydroxyapatite
ground substance in bone, calcifies, crystallized mineral salts
Compact bone
- 80% of bone in body
- strongest form of bone tissue
- found beneath periosteum and make sup most of diaphysis of long bone
- protection, support, and resists stresses produced by weight and movement
- can withstand stress in single direction
- osteons
Osteons
- found in diaphysis
- Haversion canals and perforating canals (have blood vessels)
- lamalle- extracellular fluid here
- osteocytes in lacunae
- canaliculi- allow communiction, tunnels
Spongy bone
- trabeculae
- marrow (vascular)
- can withstand stress in multiple directions
Trabeculae
- lamalle arranged in irregular lattice
- lacunae containing osteocytes by canaliculi
- forms epiphyses of long bones, along edge of medullary cavity in diaphysis, and short/flat/irregular bones
- no blood supply- wherever you find spongy bone marrow (vascular)
Periosteal arteries
supply periosteum
Nutrient arteries
- enter through nutrient foramen
- supplies compact bone of diaphysis, spongy bone, and red marrow
Epiphyseal arteries
supply red marrow and bone tissue of epiphyses
Hemopoeisis in a newborn
- a lot of bone marrow
- found in medullary cavity of long bones
- cavities between trabeculae of spongy bone of all bones
Hemopoeisis in an adult
- cavities between trabeculae of spongy bone of irregular and flat bones
- epiphyses of long bones
Intramembranous ossification
- bone forms directly from or within mesenchyme
- flat bones of skull and mandible
- occurs in spongy bone becuase of trabeculae, flat bones and mandible (not long bones)
- differentiate inot osteoblasts
- calcification
- formation of trabeculae
- development of periosteum
Calcification
- osteoblasts differentiate into osteocytes
- extracellular matrix hardens
Endochondral ossification
- forms most skeletal bones
- development of cartilage model
- development of primary ossification center
- differentiate into osteoblasts
- development of medullary cavity
- development of second ossification center
- formation of articular cargilage and epiphyseal plate
Longitudinal (interstital) growth
- increasing length, stops around age 20
- occurs at epiphyseal plate
- diaphysis gets longer, epiphyses stays same size
Appositional growth
- lamalle added to periosteum
- osteoclasts destroy bone tissue in endosteum
- diameter of medullary cavity increases
