lecture 3 & 4 Flashcards
Physiology of Bone Metabolism
define osteoblasts
promote bone formation
what are osteoclasts?
promote bone resorption and are found on the growth surfaces of bone
what are osteocytes?
play a role in the transfer of mineral form the interior of bone to the growth surfaces
what is bone?
consists of an extracellular matrix composed of proteins and hydroxyapatite crystals with a small population of cells.
what does the bone matrix provide?
strength and stability
what is hard bone called?
cortical bone
what is soft/spongy bone called?
trabecular bone
once osteoblasts have performed their major job in bone growth what happens to them?
they become osteocytes
describe the life of a “bone cell”
starts out as an osteogenic cell to become an osteoblast to form bone matrix and then once complete it becomes an osteocyte maintaining bone tissue.
what is significant about the shape of the osteoclast?
large, multinucleate and have ruffled borders
what is the idea of the osteoclast?
sits on bony surface and seals itself using the ruffled borders to release enzymes onto bone surface and begins chewing up bone to release inorganic ions to release into circulation and osteoblast comes back to remodel that part of the bone
what is the osteoid?
organic part of the matrix
what are some facts about the osteoid?
makes up 1/3 of the matrix
includes proteoglycan, glycoproteins, & collagen -which contributes to flexibility and tensile strength of bone to resist stretching and twisting
why is collagen important?
it contributes to flexibility and tensile strength of bone to resist stretching and twisting. Multiple types: collagen type I,II,III.
where and what is type I collagen?
found in the bone
so how can we relate collagens to a cut in the skin?
collagen type III comes into the area and needs to be replaced by type II and if not replaced, colloids develop - tumor because of the production of so much collagen type III because it was not replaced
what type of collagen is cartilage?
collagen type II
what type of collagen is bone?
collagen type 1
what is ossification?
the makeup of bone. So it starts with gathering of osteoblasts from the center or center of ossification and move outward to make a bone
what are the two types of ossification?
intramembraneous and endochondral ossification
what types of bones are made from intramembraneous ossification?
flat bones of the skull except those at the base, clavicles.
since flat and long bones are made via intramembraneous ossification, what bone is the exception?
clavicle
intramembraneous ossification growth pattern?
it starts from the center and moves outward. As the osteoblasts mature, they become osteocytes and become like a mesenchyme added to the periosteum like a cover for the bone
how does endochondral ossification work?
bones are first modeled in hyaline cartilage eventually replaced by bone tissue and the process uses hyaline cartilage as the pattern for bone construction