Chapter 7 The Skeleton

Skeletal Facts

• Skeleton accounts for 20% of body mass –about 30 lbs. in a 160 lb. person

• Skeleton – axial (skull, vertebral column, and thoracic cage) & appendicular

The Axial Skeleton

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Figure 5.6

The Skull

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Skull is the body’s most complex bony structure

Two sets of bones (22 bones)

Cranium

Facial bones

Bones are joined by sutures

Only the mandible is attached by a freely movable joint

Skull

• Cranial bones – protect the brain & furnish attachment sites for head and neck muscles

• Facial bones

– Form framework for the face

– Cavities for sense organs (sight, taste, & smell)

– Openings for food & air

– Secures the teeth

– Anchors facial muscles for expression

Cranial Bones• 8 bones• Frontal – anterior cranium• Paired Parietal – superior & lateral skull (where

the four largest sutures occur)• Occipital – posterior wall and base• Paired temporal – lateral surface• Sphenoid – meets with all other cranial bones• Ethmoid – forms bony area between nasal cavity

• Middle nasal conchae- posterior to cartilage in the nose, but above inferior

• Form the “helmet”

Facial Bones• Mandible – lower jawbone

• Maxillary bone – upper jaw

• Zygomatic bone (2)– cheekbones

• Nasal bones (2) – nose

• Lacrimal bones (2) –lateral nose/inside eye socket

• Palatine bones (2) – posterior part of the upper mouth

• Vomer –posterior to cartilage in the nose

• Inferior nasal conchae - posterior to cartilage in the nose

• 14 bones total

The Skull

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Figure 5.7

Bones of the Skull

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Figure 5.11

Human Skull, Superior View

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Figure 5.8

Human Skull, Inferior View

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Figure 5.9

Orbits & Nasal Cavity

• Orbits – bony cavities around eyes

• Nasal cavity – bones & hyaline (separated by nasal septum)

–Bony part – vomer and ethmoid bone

Paranasal Sinuses

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Hollow portions of bones surrounding the nasal cavity

Figure 5.10

Paranasal Sinuses

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Functions of paranasal sinuses

Lighten the skull

Give resonance and amplification to voice

Figure 5.10

The Hyoid Bone

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The only bone that does not articulate with another bone

Serves as a moveable base for the tongue

Above Adam’s Apple

Figure 5.12

The Fetal Skull

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The fetal skull is large compared to the infants total body length

Figure 5.13

The Fetal Skull

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Fontanelles – fibrous membranes connecting the cranial bones

Allow the brain to grow

Convert to bone within 24 months after birth

Figure 5.13