Osteology Test

Osteology

The study of bone structure and the treatment of bone disorders

Function of Bone

1. Support

2. Protection of internal organs

3. Assist with movement

4. Mineral storage

5. Storage of energy via lipid storage in yellow marrow

6. Site of blood cell production (red marrow)

Bone tissue consist of matrix

intercellular substance surrounding widely separated cells

bone matrix

1. 25% water

2. 25% protein fiber

3. 50% mineral salts

4. 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

1. Osteoprogenitor cells

2. Osteoblasts

3. Osteocytes

4. 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

1. Osteoporosis

2. Rickets

3. Paget’s disease

4. Osteosarcoma

5. 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