Chapter 6: Bone Tissue (Lecture)

Endoskeleton

Lies within soft tissues of body

Axial skeleton

Bones on central axis of the body; bones of head, vertebral column, ribs, and sternum

Appendicular skeleton

Bones of the extremities; bones of pectoral and pelvic girdles

Number of bones in the body

206

Basic functions of skeleton

Support, protection, movement, mineral reservoir, blood cell formation, and triglyceride storage

Hemopoises

Blood cell formation

Organic components of bone (components and function)

Glycoseaminoglycans (GAGs) and osteoids; resist stretching, provides tensile strength, adds flexibility and support

Osteoid

Extracellular matrix that has not been mineralized yet

Organic components (components and function)

Mineral salts (calcium phosphate, calcium hydroxide); makes bone harder, “the cement”, adds strength

Osteoblasts

Build bone

Osteoclasts

Carve/crush - break down bown

Osteocytes

Mature bone cells

Bone shapes

Long, short, flat, irregular, sutural, sesamoid

Long bones

Long, most bones of extremities, levers for movement

Short bones

Short; e.g. wrists and ankles

Flat bones

Two plates of compact bone separated by diploe that bridges the marrow cavity

Diploe

Spongy bone that separates layers of compact bone in flat bones

Irregular bones

Various shapes; e.g some skull bones, vertebrae, pelvis

Sutural bones

Small, extra piece of bone that develops between skull bones

Sesamoid bones

Inside tendon; kneecap (produced inside tendon, only forms once walking starts)

Diaphysis

Central part/shaft, has a thick collar of compact bone

Medullary cavity (marrow cavity)

Runs through center, contains fat of diaphysis

Epiphyses

Ends of bones, proximal/distal, spongy interior containing red BM, covered by hyaline cartilage

Epiphyseal line (metaphysis)

Between diaphysis and epiphysis, once was epiphyseal/growth plate

Periosteum

Covering of the bone, two layers: fibrous and osteogenic

Fibrous layer of periosteum

Outer layer, dense irregular CT

Osteogenic layer of periosteum

Inner layer of osteoblasts and osteocytes

Foramen

A hole in a bone

Nutrient foramen

Hole where nutrient artery goes through bone to provide nutrients

Sharpey’s fibers

attach periosteum to bone

Endosteum

Membrane lining marrow cavity; contains osteoblasts and osteoclasts

Osteon/havarian system

Structural unit

Circumferential lamellae

Entire circumference of diaphysis

Concentric lamella

Hollow rings of matrix that forms an osteon

Lacunae

Spaces at lamelle junctions containing osteocytes

Canaliculi

Connect lacunae, “little canals”

Central canal

Runs through center of osteon, contains small BVs

Perforating canal

Blood and nerve supply of periosteum to those in central canal and meduallary cavity

Interstitial lamellae

incomplete osteons between complete ones; gap fillers or remenants of old osteons