Skeletal System Axial Skeleton

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Skeletal System Axial Skeleton. Anatomy Chapter 7. Axial skeleton. axis- center consists of the center bones of the body 80 bones 3 major regions: skull vertebral column thoracic cage. Skull. most complex structure mostly flat bones has about 85 named openings - PowerPoint PPT Presentation

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Skeletal System Axial Skeleton

AnatomyChapter 7Skeletal SystemAxial Skeletonaxis- centerconsists of the center bones of the body80 bones

3 major regions:skullvertebral columnthoracic cageAxial skeleton

most complex structuremostly flat boneshas about 85 named openings22 bones, usu interlocked along suture lines8 cranium bones14 facial bonesSkullhelmetencloses and protects the brain, provides areas for muscle attachment for head movements and chewingheld together by sutures- immovable jointsCranium8 bones

frontal- foreheadparietal- largest part (2)occipital- external occipital protuberanceforamen magnumoccipital condyles temporal (2)- Latin- temporum- time passingexternal auditory meatusmastoid processstyloid process- (stake-like)zygomatic process

FrontalOccipital

Temporal5. sphenoid- (spheno-wedge)helps form base of cranium, sides of skull, floors and sides of orbits; keystonesella turcica- Turks saddle6. ethmoid bone- forms most of bony area of nasal cavity & eye orbitscribiform platescrista galli- cocks comb

SphenoidFacial bones14 bones- 13 immovable; 1 movableFxn: form basic shape of face, provide attachment for muscles, contain cavities for special sense organs, provide openings for air & food, & secure teeth

1. Maxillaekeystone bone of the faceform upper jaw, roof of mouth, floors of orbits and nasal cavity

Cleft palate2. Zygomatic bonesform cheekbones

3. Mandible

horseshoe shaped bodySinusesfxn:warm and humidify airlighten skullenhance resonance of voice

sinus infections

Fontanels

aka soft spotallows for movement through birth canalclose up by 2 years of ageVertebral Column

~ 28 long in adults26 irregular bones adultsinfants 33 bonesseparated by intervertebral discsCervical Vertebrae

C1 atlasnod yes; up and down mmentC2- axisshake no; side to side mment7 vertebrae

Thoracic VertebraeLarger than cervicalArticulate with ribs12 vertebrae

Lumbar Vertebrae

biggest vertebraebears most of bodys weightsmall of back5 vertebraeSacrum and Coccyxsacrum- 5 fused vertebraeform base of column

coccyx- lowest part of column4 fused bones

Thoracic Cage

includes ribs, thoracic vetebrae, sternum, costal cartilagesfxn: support pectoral girdle, protect viscera, aid in breathing12 pairs (usually) join to a thoracic vertebra1st 7 ribs are TRUE RIBS- join sternum directly by their costal cartilagesnext 5 pairs are FALSE RIBS- cartilage doesnt reach sternum diriectlynext 2 (3) pairs are FLOATING RIBS- no cartilaginous attachment to sternum

Ribs

usu break at greatest curvaturemiddle ribs commonly fractured

Sternumaka breastbone~ 6 longxyphoid process doesnt completely ossify until about 40 years old

Hyoid Bone

Only bone in body that doesnt articulate w/ other bonesEnables us to talk

process of bone developingbones form by replacing existing connective tissue in either of 2 ways:

1. intramembranous ossification- formation of bone directly on or within fibrous membranesOssificationsimplest, most direct type of bone development

osteoblasts form bone tissueskull & clavicles formed this way

replacement of hyaline cartilage shapes by bone tissueendo= withinchondro= cartilage

2. endochondral ossification

growth takes place at the epiphyseal plates on the long bones

most bones of body form this waymore complex methodby age 25 all bones are ossifiedclavicle- last bone to stop growing

bone REMODELING occurs continuously thru-out life

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