The Skeleton

Bone Facts Living tissue (hard

form of connective tissue)

Chief supporting tissue of body

206 bones Babies are born with

270 soft bones 64 of those bones

eventually fuse together to make the 206 hard permanent bones that an adult has

Male bones tend to be larger and heavier than females

Females pelvic cavity is wider to accommodate childbirth

Functions of the Skeleton Aid in movement of the body

moveable levers which muscles pull to move different parts of the body

To support and protect internal body organs

To produce red and white blood cells 2.6 million red blood cells produced each

second Replace those worn out and destroyed by the

liver To provide a storehouse for minerals

Calcium and phosphorous Protective and supportive framework for

attached muscles and soft tissues that underlie it

Bones Consist of microscopic cells called

osteocytes Organic Part

Protein called bone collagen – fibrous material

Between fibers is jellylike material Inorganic Part

Mineral salts Give bones its hardness and durability

When pressure is applied to a bone: Flexible organic material prevents bone

damage Mineral elements resist crushing under

pressure

Bone Structure Periosteum: outside of the bone

Tough fibrous tissue that contains blood vessels, lymph vessels, and nerves

Necessary for bone growth, repair, and nutrition

Diaphysis Compact bone

Epiphysis End of the diaphysis Contain red marrow where some red blood

cells and some white blood cells are made

Articular cartilage Covers epiphysis Acts as a shock absorber between

two bones at a joint. Endosteum

Lining of the marrow canal to keep the cavity intact

Medullary canal (cavity) Filled with yellow bone marrow

Yellow bone marrow Mostly fat cells, blood vessels, and white

blood cells Functions as a fat storage center

Spongy bone where less strength is needed in the bone Found near the epiphyseal line (growth

plate)

Bone Formation Embryonic skeleton

consists of collagenous protein fibers

During development the body is made up of mostly hyaline cartilage

During the 8th week, ossification beings and bone starts to replace cartilage

As they ossify they become hard and more capable of bearing weight

Bone Growth

Bones grow in length and ossify from the center of the diaphysis towards the epiphyses

Osteoblasts deposit new bone to the outer surface which increases the circumference

Osteoclasts secrete enzymes that digest bony material creating the medullary canal

The length of the bone shaft continues to grow until the growth plates are closed

Bone growth ends for females around 18

Bone growth ends for males around 20-21

New bone growth can occur in a fractured bone at any time

Parts of the Skeleton Axial Skeleton

80 bones Skull, spine, ribs, and sternum

Appendicular Skeleton Made up of the

shoulder girdle, pelvic girdle, and limbs

126 bones 64 bones in the

shoulders and upper limbs

62 bones in the pelvis and lower limbs

Types of Bone Flat

Thin, flattened, and usually a bit curved

Serve protective function Scapula, sternum, ribs, most bones of skull

Irregular Have weird shapes that do not fit other 3

classes Vertebrae, hip, 2 skull bones (sphenoid,

ethmoid bones)

Short Cube-like in shape Found in carpals (wrist) and tarsals

(ankle) Long

Much longer than they are wide All bones of limbs (except patella, carpals,

tarsals) Consists of shaft plus 2 expanded ends

The Skeleton

Skull

Skull

Shoulder

Chest

Sternum

Ribs

Arm

Hand

Upper Extremity

ClavicleScapulaSternumRibsHumerusRadiusUlnaCarpalsMetacarpalsPhalanges

Spine/Pelvis

PelvisSacrumPubic Bone/ Pubis

Sacrum

Pubis

Os Coxa

Leg

Foot

Tarsals

Lower Extremity

The Skeleton