Chapter 7: The Skeleton

Part A

The Axial Skeleton Consists of 80 bones Three major regions

Skull Vertebral column Thoracic cage

Figure 7.1a

Skull

Thoracic cage(ribs andsternum)

(a) Anterior view

Facial bonesCranium

Sacrum

Vertebralcolumn

ClavicleScapulaSternumRibHumerusVertebraRadiusUlnaCarpals

PhalangesMetacarpalsFemurPatella

TibiaFibula

TarsalsMetatarsalsPhalanges

The Axial Skeleton

The Skull Two sets of bones

1. Cranial bones Enclose the brain in the cranial cavity Gives attachment sites for head and neck muscles

2. Facial bones Framework of face Contains cavities for the special sense organs of

sight, taste, and smell Provides openings for the passage of air and food Secures the teeth Anchors the facial muscles of expression, which we

use to show emotion

Figure 7.2a

Bones of cranium (cranial vault)

Lambdoidsuture

Facialbones

Squamoussuture

(a) Cranial and facial divisions of the skull

Coronalsuture

Cranial Bones Occipital bone Parietal bones (2) Frontal bone Temporal bones (2) Ethmoid bone Sphenoid bone

Remember: Old P-People From T-Texas Eat Spiders

Figure 7.4a

Parietal bone

Nasal boneSphenoid bone(greater wing)Temporal boneEthmoid boneLacrimal boneZygomatic bone

MaxillaMandible

(a) Anterior view Mandibular symphysis

Frontal bone

Vomer

Ethmoidbone

Parietal Bones and Major Associated Sutures Superior and lateral aspects of cranial

vault Four sutures mark the articulations of

parietal bones with frontal, occipital, and temporal bones:1. Coronal suture—between parietal bones and

frontal bone 2. Sagittal suture—between right and left parietal

bones 3. Lambdoid suture—between parietal bones and

occipital bone 4. Squamous (squamosal) sutures—between

parietal and temporal bones on each side of skull

Coronal suture Frontal bone

Sphenoid bone(greater wing)

Ethmoid bone

Lacrimal bone

Nasal bone

Zygomaticbone

Maxilla

Mandible

Parietal bone

Lambdoidsuture

SquamoussutureOccipitalbone

Occipitomastoidsuture

(a) External anatomy of the right side of the skull

Zygomaticprocess

Temporal bone

Figure 7.5a

Occipital Bone Most of skull’s posterior wall and posterior

cranial fossa Contains the foramen magnum “large hole”

through which the brain connects with the spinal cord

Articulates at the occipital condyles with 1st vertebra

Sites of attachment for the many neck and back muscles

Figure 7.4b

Lambdoidsuture

Occipital bone

Suturalbone

Occipitomastoidsuture

(b) Posterior view

Parietalbone

Sagittal suture

Figure 7.6a

Median palatine sutureIntermaxillary suture

Maxilla

Sphenoid bone(greater wing)

Foramen magnum

Maxilla

Zygomatic bone

Temporal bone(zygomatic process)

Vomer

(a) Inferior view of the skull (mandible removed)

Temporal bone

Parietal bone

Palatine bone

Temporal Bones Inferolateral aspects of skull and parts of

cranial floor Contains the zygomatic process, external

acoustic meatus, the styloid process, and the mastoid process

Articulates with the mandibleat the TMJ

Sphenoid Bone

Complex, butterfly-shaped bone Keystone bone

Articulates with all other cranial bones Three pairs of processes Contains the sella turcica and the

hypophyseal fossa that surround the pituitary gland

Ethmoid Bone

Deepest skull bone Superior part of nasal septum, roof of nasal

cavities Contributes to medial wall of orbits Contains the superior and middle nasal conchae Contains the crista galli (rooster’s comb)

The attachment site for the outermost covering of the brain

Figure 7.10

Sutural Bones Tiny irregularly shaped bones that appear

within sutures

http://www.sciencekids.co.nz/videos/humanbody/skullbones.html

Figure 7.4b

Lambdoidsuture

Occipital bone

Suturalbone

Occipitomastoidsuture

(b) Posterior view

Parietalbone

Sagittal suture

Facial Bones (14 Total)Unpaired Bones:

Mandible Vomer

Paired Bones:

Maxillary bones (2) Zygomatic bones (2) Nasal bones (2) Lacrimal bones (2) Palatine bones (2) Inferior nasal Conchae

(2)

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Mandible Lower jaw Largest, strongest bone of face Articulates at the temporomandibular joint

(TMJ): only freely movable joint in skull

Figure 7.11a

Mandibularangle

Ramusofmandible

Body of mandible(a) Mandible, right lateral view

Temporomandibularjoint

Maxillary Bones Medially fused to form upper jaw and central

portion of facial skeleton Keystone bone of the facial bones: all facial

bones except the mandible articulate with it

Zygomatic Bones

Cheekbones Inferolateral margins of

orbits Articulates with 3

separate zygomatic processes

Frontal zygomatic process Maxillary zygomatic

process Temporal zygomatic

process

Nasal Bones and Lacrimal Bones Nasal bones

Form bridge of nose Attach to the cartilage that forms most of the

skeleton of the nose

Lacrimal bones In medial walls of orbits Forms part of the canal that drains tears into the

nasal cavity

Lacrimation = crying/tear production

Figure 7.4a

Parietal bone

Nasal boneSphenoid bone(greater wing)Temporal boneEthmoid boneLacrimal boneZygomatic bone

MaxillaMandible

(a) Anterior view Mandibular symphysis

Frontal bone

Vomer

Ethmoidbone

Palatine Bones and Vomer Palatine bones

Posterior one-third of hard palate

Posterolateral walls of the nasal cavity

Small part of the orbits

Vomer Plow shaped Lower part of

nasal septum

Figure 7.6a

Median palatine sutureIntermaxillary suture

Maxilla

Sphenoid bone(greater wing)

Foramen magnum

Maxilla

Zygomatic bone

Temporal bone(zygomatic process)

Vomer

(a) Inferior view of the skull (mandible removed)

Temporal bone

Parietal bone

Palatine bone

Orbits Encase eyes and lacrimal glands Sites of attachment for eye muscles Formed by parts of seven bones

Frontal bones Zygomatic Sphenoid bones Palatine Ethmoid Lacrimal Maxilla

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Roof of orbit

Medial wall

Floor of orbit

Nasal bone

Lateral wall of orbit

Zygomatic bone

(b) Contribution of each of the seven bones forming the right orbit

• Lesser wing ofsphenoid bone

• Orbital plate offrontal bone

• Zygomatic processof frontal bone

• Greater wing ofsphenoid bone

• Orbital surface ofzygomatic bone

• Sphenoid body

• Orbital plateof ethmoid bone

• Lacrimal bone

• Orbital surface ofmaxillary bone

• Zygomatic bone

Figure 7.13a

Nasal Cavity Roof, lateral walls, and floor formed by

parts of four bones Ethmoid Palatine bones Maxillary bones Inferior nasal conchae

Nasal septum of bone and hyaline cartilage Ethmoid Vomer Anterior septal cartilage

Figure 7.14a

Maxillary bone(palatine process)

Palatine bone(perpendicular plate)

Palatine bone(horizontal plate)

(a) Bones forming the left lateral wall of the nasal cavity (nasal septum removed)

Sphenoidbone

Frontal sinus

Ethmoidbone

Nasal bone

Paranasal Sinuses Mucosa-lined, air-filled spaces Lighten the skull Enhance resonance of voice Found in frontal, sphenoid, ethmoid, and

maxillary bones

Figure 7.15

Frontalsinus

Ethmoidalair cells(sinus)

Maxillarysinus

Sphenoidsinus

Frontalsinus

Ethmoidalair cells

Maxillarysinus

Sphenoidsinus

(a) Anterior aspect (b) Medial aspect

Hyoid Bone

Not a bone of the skull Does not articulate directly with another bone Site of attachment for muscles of swallowing

and speech

Developmental Aspects of the Skull

At birth, the newborn’s skull not fully developed and sutures have not yet fused

• Allows for head compression during birth• Allows for brain growth in the infant

Unossified regions are covered with fibrous membranes called fontanelles “little fountains”

Anterior fontanelle is present until 1-1/2 –2 years of age

Homeostatic Imbalance of the SkullThe Cleft Lip and Palate

Caused by right and left halves of the palate failing to fuse medially

Leads to difficulties feeding/nursingRisk for aspiration (inhalation) pneumonia

Review Slides