lecture 2 Flashcards
Bone Tissue and Features
what are the functions of bones?
1) support
2) protection
3) movement
4) storage
5) site for hematopoiesis
what are long bones?
proportionally long and thin
what are flat bones?
parallel layers of compact bone sandwiching spongy bone
what are short bones?
small cuboidal shaped bones
what are irregular bones?
they are other various shapes other than long, short and flat like your vertebrae
what are sesamoid bones?
develop within tendons and serve as the fulcrum point of tendon
what is compact bone?
dense and grossly homogenous in composition
what is spongy bone?
trabeculae bridging cavities between layers of compact bone
what is the diaphysis?
shaft of the bone
what is important to note about the diaphysis?
it surrounds the medullary cavity that contains yellow marrow for adult or red marrow for child
what is the epiphysis?
ends of long bone
what is the metaphysis?
located between epiphysis and diaphysis, this includes the epiphyseal plate
what is the epiphyseal plate?
found internally at junction of epiphyseal and medullary marrow cavities; this is the site of longitudinal growth
what is the articular cartilage?
found on articulating surfaces surfaces which cushions and absorbs stress
what is the periosteum?
fibrous membrane that bounds the outer surface of bone
how does intramembraneous ossification work?
embryonic tissue called mesenchyme converted directly to bone, i.e. flat bones
how does endochondrial ossification work?
cartilage model is ossified into bone via primary ossification centers in utero and then secondary ossification occurs after birth and sometimes completed in mid adulthood. The epiphyseal plate is located between the primary and secondary ossification centers and serves as the source of longitudinal growth.
how often does bone remodeling occur?
it is an ongoing process throughout lifetime
why is bone density important?
loss of density causes bone to become brittle, lose their elasticity and fracture easily
what forces act on the remodeling process?
blood calcium levels mechanical stress
hormones
how does mechanical stress affect the bone?
1) affects bone density and prominence of features
2) will have an even greater effect if bone density is already low, moreso in women than men
3) important in maintaining density
4) proper position is important for proper remodeling
what types of hormones are important for bone deposition?
GH, PTH, calcitonin, estrogen, testosterone
what are some clinical correlations of bone?
supernumerary bones, bone growth and assessment of age, displacement and separation of epiphyses, avascular necrosis
what are some examples of supernumerary bones (bones in excess)?
accessory bones (due to failure in bones to fuse or because of genetic variation resulting in extra bone) and heterotopic bones (abnormal form in soft tissues due to repeated micro trauma)
what is avascular necrosis?
loss of blood supply resulting in death of bone tissue, dead bone wears down more easily, and is a major cause in hip replacement
how does bone growth correlate with assessment of age?
we see the development of ossification centers, completing ossification and fusing of bones follows predictable time schedule and used to determine skeletal age. So early age, we see no epiphysis, it becomes more apparent and larger as you get older and eventually when you become older it fuses and no more growth can occur; sometimes used to estimate final height of early or late maturing adolescents
what is a displaced (slipped/dislocated) epiphysis
because the bone (metaphysis) is not held as tightly to cartilage as bone to bone it a fracture (where the metaphysis pulls from the epiphyseal plate) can occur here and so it is only held in place by the periosteum, this happens ONLY in children
