“The nature of the body is the beginning of medical science”

Hippocrates

09/29/2011

Introduction to Anatomy

The Skeletal System:The Axial SkeletonAxial Skeleton

80 boneslie along longitudinal axisskull, hyoid, vertebrae, ribs,

sternum, ear ossiclesAppendicular Skeleton

126 bonesupper & lower limbs and pelvic

& pectoral girdles

Types of Bones5 basic types of bones:

long = compactshort = spongy except

surfaceflat = plates of compact

enclosing spongyirregular = variablesesamoid = develop in

tendons or ligaments (patella)

Sutural bones = in joint between skull bones

Anatomy of a Long BoneDiaphysis = shaftEpiphysis = one end of a long boneMetaphysis = growth plate regionArticular cartilage over joint surfaces

acts as friction & shock absorberMedullary cavity = marrow cavityEndosteum = lining of marrow cavityPeriosteum = tough membrane

covering bone but not the cartilage fibrous layer = dense irregular CTosteogenic layer = bone cells & blood

vessels that nourish or help with repairs

Histology of BoneA type of connective

tissue as seen by widely spaced cells separated by matrix

Matrix of 25% water, 25% collagen fibers & 50% crystalized mineral salts

4 types of cells in bone tissue

http://www.youtube.com/watch?v=ylmanEGjRuY

Matrix of BoneInorganic mineral salts provide bone’s hardness

hydroxyapatite (calcium phosphate) & calcium carbonate

Organic collagen fibers provide bone’s flexibilitytheir tensile strength resists being stretched or tornremove minerals with acid & rubbery structure results

Mineralization (calcification) is hardening of tissue when mineral crystals deposit around collagen fibers

Bone is not completely solid since it has small spaces for vessels and red bone marrowspongy bone has many such spacescompact bone has very few

Cell Types of Bone

Osteoprogenitor cells ---- undifferentiated cells can divide to replace themselves & can become osteoblastsfound in inner layer of periosteum and endosteum

Osteoblasts--form matrix & collagen fibers but can’t divideOsteocytes ---mature cells that no longer secrete matrixOsteoclasts---- huge cells from fused monocytes

function in bone resorption at surfaces such as endosteumImportant regulator of calcium and phosphate concentrations

Hydroxyapatite crystals

Osteoporosis vs Normal Bone

http://www.gla.ac.uk/ibls/US/fab/tutorial/generic/bone5.html