Question | Answer |
Compact Bone | Outer Layer |
Spongy Bone (Cancellous bone/trabecular bone) | network of bone-pieces (called trabeculae or spicules) |
Trabeculae | Individual bone pieces in spongy bone network |
Where is bone marrow located? | between spaces of trabeculae |
medullary cavity (marrow cavity) | middle of long bones that still contains bone marrow but not trabeculae |
Periosteum | membrane of dense connective tissue that covers every bone in body
lays down bones during repair and growth |
Endosteum | covers inner surface of compact bone and trabeculae |
How much compression can bones resist? | 25,000 lbs. per square inch
not only weight-bearing columns but bending force
tension allowed by collagen |
Diaphysis | shaft of bone (growth between) |
Epiphysis | ends (Growth upon) |
Nutrient Artery | artery Located in the middle of the shaft |
Epiphyseal artery | Artery located into ephyphsis |
Why does it hurt so bad when bones are broken? | Supply to periosteum is rich in blood supply and highly innervated |
Osteocytes | Most numerous of bone components
like fibroblast and chondrocyte.
shaped like spider, central cell body (nucleus)
occupy lacunae (hollow space in matrix) |
Canaliculi | cell processes of osteocytes connected by these tiny canals
nutrients from blood capillaries carried from osteocyte to osteocyte by these junctions
Maintain extracellular matrix
sense stresses blase on matrix, signal remodeling accordingly |
Osteoblasts | NOT located in matrix but periosteium, enosteum
hemisphere shaped
Bone forming cells
become osteocytes once matrix calcifies them |
Osteoclasts | Bone-resorbing/destroying
derived from blood-forming cells in bone marrow, not bone-forming cells |
Woven Bone of Compound Bone | present in development, 1st type of bone tissue
between embryonic blood vessels
matrix appears uniform |
Lamellar Bone of Compound Bone | mature bone
replaces woven bone in fetus
in adults, all bone tissue lamellar |
lamellae | sheet bent into tube
resists twisting |
osteon | Haversian system
column system |
Central Canal | middle of osteon
filled with loose connective tissue
supply nutrients to living bone cells especially osteocytes in wall of osteon |
Why do bone components specifically undergo constant eating away and replacement? | allow constant turnover of calcium and phosphate between bone and body fluids
Also realign the osteon pillars along new lines of compression |
How are bones classified? | to whether or not they are first formed in cartilage
Membrane bones
endochondral bones |
Membrane Bones | not from cartilage but membranes from mesenchyme
Only related bone in humans is skull bones (not including condyles and base of skull)
Form by intramembranous ossification |
Mesenchyme | tissue that gives rise to connective tissue |
Endochondral Bones | all other bones formed by cartilage first
not including clavicles
but vertebrae, long bones of limbs, fingers/toes
Endochondral ossification, which begins |
When does endochondral ossification begin in development | end of the 8th week (late embryo/early fetus)
ends 15 to 20 years later, when skeleton stops growing
Only increase bones in length |
What does growing bone contain (hard tissue) | Hyaline Cartilage
Calcified Cartilage
Bone Tissue |
What are the steps of Endochondreal ossification? | 1. Periosteum Forms
2. Cartilage Calcifies in Shaft
3. Artery enters, first spongy bone forms
4. Epiphyses takes form
5. Ephyses start to ossify (Begins at birth)
6. Growth occurs at epiphyseal plates
7. Closure of epip plates |
Mesenchyme | From artery, comes these cells that turn into osteoblasts. |
How long will epiphyses take form? | Chondrocytes will continue to promote efficient growth from fetal period to time of birth |
What signals the ephyseal plates (growth plates) to grow? | growth hormone, from pituitary gland
sex hormone speeds growth but eventually stops growth as adolescence ends |
How do bones widen? | Osteoblasts in the periosteum add bone to outside of diaphysis while osteoclasts erode away inner wall at same rate. |