| Question | Answer |
| what are osteoprogenitor cells and what can they differentiate into? | they are undifferentiated mesenchymal cells. they can differentiate into either osteoblasts or under low oxygen tension chondroblasts |
| red marrow functions as what? | haemopoetic function |
| where are the haversian canals located? | they are located in the midcortex |
| how does bone initially form? | as a disorganized coarse mesh called woven bone. this type is found in the fetus and post-injury |
| describe endochondral ossification. | occurs when a hyaline cartilaginous model continues to grow and forms as a scaffold for the developing bone |
| what are osteoblasts derived from and what is their responsibility? | they are derived from osteoprogenitor cells and are responsible for depositing bone |
| define remodeling | the process by which bone matrix is turned over, conducted by BMU - basic multicellular unit |
| what are the primary ossification centers? | where endochondral ossification begins, responsible for the formation of the diaphysis of long bones |
| cartilaginous joints occur when bones are joined by what or what | hyaline cartilage or fibrocartilage |
| bone is a ____ tissue and consisting of cells embedded in a _____ | connective, matrix |
| what are the two types of lamellae? | 1. outer circumferential lamellae found on the periosteal surface
2. inner circumferential lamellae found on the endosteal surface |
| osteoblasts are stimulated by what to resorb bone? | positive piezoelectric charges |
| the sutures of the skull are what types of joints? | fibrous joints |
| what hormone is secreted when the blood calcium level rises? | calcitonin |
| what do osteoblasts secrete? | small vesicles with organic bone matrix precursors onto the appositional surface. |
| what is longitudinal growth? | growth that increases bone length by adding new bone at the growth plates |
| where are osteoprogenitor cells found? | they are found on the periosteal surface as well as lining haversian canals |
| what four things drive remodeling? | 1. mobilization of calcium
2. removal of microdamage
3. vascularization
4. mechanical stress |
| what gland secretes calcitonin? | thyroid |
| what do BMUs (basic multicellular units) do? | turn over cylindrical packets of bone by:
1. localized destruction - resorption space
2. formation of new concentric lamellae - haversian system |
| how does the epiphyseal plate elongate? | by proliferation of chondrocytes |
| how are osteocytes formed and what are they responsible for? | they form when osteoblasts become surrounded with matrix. they are responsible for the resorbtion of bone |
| at what location do long bones grow in length? | at the epiphyseal plate |
| how to osteocytes communicate with neighboring osteocytes? | via long processes |
| the production of parathyroid hormone results in what? | osteoblasts have receptors that recognize this hormone and they stimulate osteoclasts to resorb bone to liberate calcium |
| what are the primary organic components of bone? | collagen (mainly type 1)
proteoglycans
glycoproteins (osteocalcin, osteopontin, bone sialoprotein, & osteonectin) |
| what are howship's lacunae? | small cavities that form when osteoclasts resorb bone |
| the compressed side of bone is electro____ and the tension side is electro____ | negative, positive |
| bone stores which minerals? | calcium and phosphorus |
| what are central canals? | canals containing a neurovascular bundle that supplies the surrounding bone. |
| what does the ruffled border of osteoclasts secrete? | H+ ions
lysosomal hydrolases
collagenase |
| what are volkman's canals? | canals that allow central canals of adjacent osteons communicate |
| what is bone's primary inorganic component? | calcium hydroxyapatite |
| yellow marrow functions as what? | energy storage |
| unlike osteoblasts, osteoclasts orginate from what? | monocyte precursors (granulocyte-macrophage progenitor cell) |
| during bone formation, what does the perichondrium surrounding the diaphysis become? | periosteum |
| calcitonin inhibits what? | osteoclast activity and thus bone resorption |
| in the diaphysis, what do chondrogenic cells differentiate into? | osteoblasts |
| what are canaliculi? | small canals that connect the lacunae and allow the osteocytes to communicate via long processes with gap junctions |
| where is subchondral bone found? | at joints underlying hyaline cartilage |
| what are the four types of bones based on their gross morphological appearance? | long bones, short bones, flat bones, and irregular bones |
| what is appositional growth? | growth that increases diameter by adding new bone under the periosteum |
| describe intramembranous ossification. | it occurs when mesenchymal cells differentiate directly into osteoblasts. the osteoblasts then start laying down spciules of bone |
| what are the three distinct processes involved in the microstructure of bone? | 1. growth
2. modeling - primary bone
3. remodeling - secondary bone |
| what is the mechanostat hypothesis? | that strain magnitude within the bone regulates modeling and remodeling |
| what are the three types of bone based on their internal structure? | 1.cortical (compact) bone
2.cancellous (spongy/trabecular) bone
3.subchondral bone |
| what are lamellae? | highly organized and arranged sheet of mature compact bone |
| what ties the periosteal membrane to the bone surface? | sharpey's fibers |
| what are the two ways bone can form? | 1. intramembranous ossification (like bones of the cranial vault, face and clavicles)
2. endochondral ossification (all other bones) |
| what do osteoblasts communicate with neighboring osteoclasts via? | gap junctions |
| according to the mechanostat hypothesis, an above acceptable strain level results in what two things? | modeling stimulated and remodeling suppressed |
| cancellous bone consists of a meshwork of struts or ____ | trabeculae |
| define modeling (aka surface remodeling) | the process by which bones modify their gross morphology and internal architecture - limited in mature bones. it is also the primary process by which bones adapt to their mechanical environment |
| osteoblasts are stimulated by what to deposit bone? | negative piezoelectric charges |
