The number of bones in an adult skeleton

206

Functions of the Bone

1) Support and Protections

2) Movement

3) Hemopoiesis

4) Storage of Mineral and Energy Reserves

Hemopoeisis

blood cell productionin red bone marrow, which is located in some spongy bone

Classification by Bone Shape

Long Bone

Short Bone

Flat Bone

Irregular Bone

Long Bone

- greater length than width and vary in size

- composed of diaphysis (long shaft) with epiphyses (distinct ends)

- located in upper and lower limbs

diaphysis

the shaft of the long bone

epiphysis

the epanded, knobby region of the long bone

proximal epiphysis

the end of the bone closest to the body trunk

distal epiphysis

the end of the bone farthest from the trunk

metaphysis

the region in a mature bone sandwhiched b/t the diaphysis and epiphysis

epiphyseal line

a thin layer of compact bone

articular cartilage

the thin layer of hyaline cartilage covering the epiphysis at a joint surface

medullary cavity

the hollow cylindrical space w/in the diaphysis

endosteum

an incomplete layer of cells that covers all internal surfaces of the bone

periosteum

tough sheath that covers the outer surface fo the bone

perforating fibers

the periosteum is anchored to the bone by numberous strong collage fibers

sutural or wormian bones

small bones located w/in the sutures of certain cranial bones number of sutural bones vary from person to person

Short Bone

- length ~= width

- esternal surface is compact bone while interior is spongy bone

- includes wrist bones and feet bones

- seasmoid bones

- patellla is the largest seasmoid bone

seasmoid bones

tiny, seed shaped bones along tendones of some muscles

Flat bone

- flat, thin surface

- parallel surfaces of compact bone with a internal layer of spongy bone

- provide extensive surfaces of muscle attachements and protect underlying tissues

- form the roof of the skull, scapulae, sternum and ribs

Irregular Bone

- elaborate, complex shapes ando not fit in any of the above categories

- examples include vewrtebrae and several bones in the skull

Bone matrix is composed of

organic and inorganic material

1/3 = cells, colagen fibers, and ground substance

2/3 = calcium phosphate

calcium phosphate + calcium hydroxide

hydroxyapatite

hydroxyapatite + mineral salts + ions

mineral salts

Calcification

mineral salts deposited in the collagen fiber framework where they crystallize and tissue hardens

Calcification is initiated

by osteoblasts

Osteoprogenitor/ osteogenic cells

stem cells derived from mesenchyme which produce other stem cells and osteoblasts

osteoblasts

produces new bones

osteocytes

mature bone cells

- main cells in bone tissues and maintain daily metabolism functions

osteoclasts

- huge cells derived from fusion of monocytes (WBCs)

- involved in bone resorption, which is part of the normal development, growth, maintenance and repair of bone

4 types of bone cells

- osteoblasts

- osteocytes

-osteoprotegenitor

- osteoclasts

2 types of bone tissue

compact and spongy

Compact Bone Tissue

- solid and dense forming the outer roegion of bone

- found where stresses come from a limited range of directions

- forms the external solid walls of long bones

Spongy Bone Tissue

- located internally and appears more porous

- found where stress is relative low and comes from various directions

- forms an open lattice of narrow plates of bones (trabeculae)

primarily found w/in the epiphyses

Flat Bones w/in the SKull

- compoes of 2 layers of compact bone w/a region of spongy bone (diploe)

- both layers of compact bone are covered by periosteum

Ossification

- begins in the embryo and continues as the skeleton grows during childhood and adolescence

- b/t the eighth and twelth wks of embryonic development, skeleton begins forming from thick condensations of mesenchyme or hyaline cartilage

Intramembranous ossification

produces the flat bones of the skull, some fo the facial bones, the mandible and the central part of the clavicle

Steps of the Intramembranous Ossification

1) Ossification centers from w/in thickened regons of mesenchyme

2) Osteoid undergoes calcification

3) Woven bone (primary bone) and its surrounding periosteum form

4) Lamellar bone replaces woven bone, as compact and spongy bone form

Endochondral Ossification

begins w/ a hyaline cartilage model and produces most of the other bones of the skeleton

Steps of the Endochondral Ossification

1) Fetal hyaline cartilage model develops

2) Cartilage calcifies and a periosteal bone collar forms

3)The primary ossification center forms in the diaphysis

4) Secondary ossification centers form in the epiphyses

5) Bones replaces cartilage

6) Epiphyseal plates ossify and from epiphyseal lines

Bone Remodeling

- bone tissues constantly being replaced & widened

- bone tissue is formed/lost in response to mechanical stress

- replaced as we age due to loss of calcium and collagen

- occurs at both the periosteal and endoseteal surfaces of a bone

Three categories of blood vessels develop to supply a typical bone

- Nutrient vessels

- Metaphyseal vessels

- Periosteal vessels

Nutrient Vessels

- nutrient artery and nutrient vein

- supply the diaphysis of the bone

Metaphyseal vessels

- metaphyseal arter and metaphyseal vein

- supplies blood to the diaphyseal side of the epiphyseal plate

Periosteal vessels

- periosteal artery and periosteal vein

- supply the superficial osteons w/in the compact bone

Effects of Hormones and Vitamins

- Control & and regulate growth patterns in bone by altering the rates of both osteoblast and osteoclast activity

- a continual dietary source of vitamins is requred for normal bone growth

Calcitonin

promotes calcium deposition in bone and inhibits osteoclast activity

Growth Hormone

stimulates liver to produce the hormone somatomedin which causes carilage proliferation at epiphyseal plate and resulting bone elongation

Parathyroid hormone

increases blood calcium levels

Sex hormones (estrogen and testoterones)

stimulate osteoblasts; promote epiphyseal plate growth and closure

Thryoid Hormone

stimulate bone growth by stimulating metabolic rate of osteoblasts

Vitamin A

activates osteoblasts

Vitamin C

promotes collagen production

Vitamin D

promostes absorption of calcium and phosphate into blood

Stress fracture

a thin break caused by incrased physical activity during repetitive loads

Pathological fracture

occurs in a bone weakened by disease

Simple fracture

broken bone does not penetrate the skin; heals in 2-3 months

Compound fracture

one or both ends of the broken bone pierces the skin; takes longer to heal

Bone Markings

- provides articulate surfaces

- provide muscle/tendon/ligament attachment sites

- allow passage of nerves/vessels/tendons/ligaments