Skeletal System and Bones

what is the unique aspect of bones?

• has passive mechanical properties of non-living materials

• and self-repair properties of biological materials

components of the skeletal system

• bones

• cartilage

• ligaments

• other supportive connective tissue

structure of skeletal system

• hard, elastic, tough connective tissue

• internal “endo” skeleton; scaffold structure

• articulated through many individual bones

• dense bone exterior and relatively open interior

• protrusions have attachment sites

functions of skeletal system

• support and protection for body and internal organs

• connections to tendons, muscles, ligaments for dynamic movement

• calcium and phosphate homeostasis and storage

• blood cell production (stem cell marrow)

What type of tissue is bone?

connective

specialized cells of bones

• osteoclasts

• osteoblasts

• osteocytes

osteoclasts

bone breakdown

osteoblasts

bone matrix deposition

osteocytes

bone matrix maintenance

bone specific matrix protein

collagen

collagen

• triple helix

• most abundant protein in the body

• provides flexibility, ductility, and toughness

ground substance of bone

• many minerals

• hydroxyapatite mineral: Ca₁₀(PO₄)₆(OH)₂

In its natural state bone is both…

• somewhat flexible

• very strong

What breaks down collagen and why? What does it do to the bone?

• baking because heat denatures proteins

• causes the bone to be more brittle

What degrades hydroxyapatite and why? What does it do to the bone?

• vinegar because its an acid that will react with the hydroxide (and phosphate) in hydroxyapatite and become water

• bone is not sturdy anymore

types of bones

• cortical/compact

• cancellous/spongy

cortical/compact bone

• dense/ “solid” outer layers

• external layers of both long and flat bones

• mechanically, can be conceptualized as an elastic beam of uniform dimension

  • benefit: provides lots of material strength without much actual materials or density

cancellous'/" “spongy” bone

• “spongy” refers to the fact that is has holes, not soft like a sponge

• open interior lattice

• narrow plates of bones called trabeculae

• note that the lattice does have order

  • similar to structure of Eiffel Tower

osteon

• runs parallel to the long bone axis

• cylinder of hollow tubes of bone matrix, with a central canal carrying blood vessels and nerves

• also called Helenians canals

lacunae

gap inside of an osteon

epiphysis

• knobby region at each end

• for strength and site of attachment

metaphysis

• region between the epiphysis and diaphysis

• contains the growth plate

diaphysis

• elongated, cylindrical shaft of bone

articular cartilage

• supporting connective tissue

• reduces friction

periosteum

membrane of tough, irregular, dense, connective tissue covering the external surface of a bone

endosteum

membrane of “vascular” connective tissue; internal surface of the bone

medullary cavity

• red marrow in flat bones

  • produces rbc, wbc and platelets

• yellow marrow

  • in long bones for fat storage