Lecture 3: Bone (Wronski) Flashcards
what creates the extreme hardness of bone?
mineralization of its extracellular matrix
name 4 functions of bone
- provides support and protection for the bodys soft tissue and organs
- serves as an attachment for muscle and tendons
- serves as a source of minerals (calcium and phosphate) for homeostasis
- encloses hematopoietic tissues (bone marrow)
what type of bone is very dense?
compact or cortical bone
what type of bone is less dense and lattice-like, and is composed of spicules and trabeculae of bone within bone marrow?
cancellous, trabecular or spongy bone (they all mean the same thing)
most bones possess what 5 features?
- articular surface
- cortex
- medullary cavity
- periosteum
- endosteum
define periosteum
specialized connective tissue that lines the external surface of cortical bone
what are the two layers of periosteum?
- outer fibrous layer
2. inner osteogenic (cambian) layer
is periosteum vascularized?
yes, very vascularized
what makes up the inner osteogenic layer of the periosteum?
osteogenic (osteoprogenitor) cells, stem cells capable of producing osteoblasts when needed for growth, maintenance, repair of bone
describe the endosteum layer of bone
it lines all internal surfaces of bone including the inner surface of cortical bone as well as the canals of cortical bone
define lamellar bone
the extracellular matrix that makes up one is organized into arrays of lamellae which is where the term lamellar bone comes from
define lacunae
numerous small cavities at the margins of each lamina. they each house an osteocyte
define canaliculi
minute canals that radiate out in all directions from each lacuna and communicate directly with neighboring lacuna.
how do osteocytes make cell-to-cell contact?
through specialized gap junctions
what are the 4 lamellar patterns of bone?
- cylindrical lamellae aka Haversian aka osteonal
- interstitial
- outer circumferential
- inner circumferential
define interstitial lamellae
angular lamellae situated betwen haversian systems
define inner and outer circumerferential lamellae
cortical lamellae that extend completely around the entire cortex just beneath the periosteum and endosteum
what is the difference between outer and inner circumferential lamellae?
the outer circumferential is along the periosteal surface, the inner circumferential is along the endocortical surface
define cement lines
thin lines of uncalcified matrix that delineatemargins of haversian and interstitial systems
define cylindrical lamellae aka haversian canals aka osteons
cylindrical lamellae of bone matrix that form the cylindrical units of bone that comprise haversian systems or osteons.
is bone vascular?
YES!
what are the central openings of haversian systems called? what do they contain?
haversian canals. they contain 1-2 small vessels they are usually either capillaries or postcapillary venules.
there are two vascular channels that communicate with haversian canals - what are they called?
- Volkmann’s canals aka communicating canals
2. perforating canals
in what direction do volkmann’s canals or communicating canals travel?
they pass transversely or obliquely through the lamellae