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Osteology
The study of bone structure and the treatment of bone disorders
Function of Bone
Support
Protection of internal organs
Assist with movement
Mineral storage
Storage of energy via lipid storage in yellow marrow
Site of blood cell production (red marrow)
Bone tissue consist of matrix
intercellular substance surrounding widely separated cells
bone matrix
25% water
25% protein fiber
50% mineral salts
Bone cells
Protein fiber
collagen
mineral salts
calcium, phosphates
hardness
provided by the calcification of mineral salts
calcification
mineral salts crystallizes around collagen fibers hardening the matrix
tensile strength
collagen fibers reinforces the matrix making bone flexible and brittle
Four main types of cells in bone tissue
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Osteoprogenitor cells
unspecialized precursor cells that form osteoblasts by mitosis- found in periosteum and endosteum
Osteoblasts
immature bud cells that form bone
they secrete collagen and organic compounds that build bone tissue matrix
osteocytes
mature bone cells
-osteoblasts surround themselves with matrix secretions thus becoming osteocytes
-maintain daily cell activities of bone tissue
Osteoclasts
Develop from white blood cells
-function in reabsorption bone
-important for development, growth, maintenance, and repair of bone
Two types of bone tissue
Compact bone- dense
Cancellous bone(spongy bone)- porous
Cancellous(Spongy Bone)
Location: make up tissue in short, flat, and irregularly shaped bones and epiphysis of long bone
Function: Stores red bone marrow and provides some support
Structure: Made up of trabeculae
Compact (dense) bone
Location: found in external layers of all bones and make up the diaphysis of long bones
Function: provides protection and support, and helps long bone resist stress of weight
Structure: made up of concentric rings called osteons
Structure of an Osteon
perforating (Volkmann’s) canals
central (Haversian) canals
concentric lamellae
lacunae
canaliculi
perforating (Volkmann’s) canals
canals that run horizontally through bone
central (Haversian) canals
canals run longitudinally (vertically) through bone
concentric lamellae
rings of hard calcified matrix that surround the central canal
lacunae
small spaces between lamellae which contain osteocytes
canaliculi
minute canals radiating in all directions connecting lacunae
-filled with extracellular fluid that provides passage for nutrients, O2, and waste to reach osteocytes
Interstitial lamellae
fragments of older osteons found in spaces between osteons
Structure of long bone
diaphysis
epiphysis
metaphysis
articular cartilage
periosteum
outer fibrous layer
inner elastic layer
medullary cavity
endosteum
cancellous bone
compact bone
diaphysis
central shaft
epiphysis
end of long bones
metaphysis
region between diaphysis, joins the epiphyses
articular cartilage
thin layer of hyaline cartilage, covers the end of bones
periosteum
thick double layered membrane covering bone
Function: helps bone to grow in diameter, protects the bone, repairs, nourishes, and serves as an attachment for ligament and tendons
medullary cavity
central cavity, containing yellow marrow
endosteum
thin membrane lining medullary canal
cancellous bone
spongy bone, mostly found in the epiphysis
compact bone
dense bone, mostly found in the diaphysis
Ossification
the process of bone formation
-embryonic connective tissue hardens into bone
-begins around the 6th week of utero and continues through adulthood
two patterns of ossification
-Intramembranous ossification
-endochondral ossification
Intramembranous ossification
occurs directly within fibrous connective tissue
-occurs in flat bones of skull and lower jaw
-osteoprogenitor cells develop into osteoblasts which secrete bony material
Endochondral ossification
occurs within hyaline cartilage tissue
-occurs in most bones, long bones
-cartilage becomes calcified from inside out
-hyaline cartilage remains on articular surfaces
Nutrient artery
-blood vessels that enter the bone through the periosteum
-branches through the Haversian canals from epiphyseal to periosteal arteries
Remodeling
the replacement of old, worn, or injured bone tissue
Osteoclast: removes collagen and minerals
Osteoblasts: secretes new collagen and minerals
Normal bone growth requirements
a) minerals: calcium, phosphorus, magnesium, etc
b) vitamins: A, B12, C and D
c) hormones: HGH, testosterone, insulin
bone strength varies depending on
mechanical stress increasing mineral deposition and production of collagen fibers
mechanical stress is mainly affected by
muscle work and gravity
removal of stress
weakens bone and reduces density
exercises such as walking and lifting
increase bone density
Demineralization
loss of calcium and other minerals from matrix
-females: begins at age 30
-males: begins at age 45
Decrease in protein synthesis
reduces collagen production
Disorders
Osteoporosis
Rickets
Paget’s disease
Osteosarcoma
Scoliosis
Osteoporosis
a loss of too much calcium making bone less dense
Rickets
too flexible, vitamin D deficiency
Paget’s disease
abnormal acceleration of the remodeling process
osteosarcoma
bone cancer
scoliosis
is a sideways curvature of the spine that occurs most often during the growth spurts