The Skeleton Chapter 7 Part A The Skeleton

The Skeleton Chapter 7 Part A

The Skeleton • Skeleton = Greek for ‘dried up body’ or ‘mummy’ • Composed of bones, cartilages, joints, and ligaments – Mostly bone – Ligaments connects bones and reinforces joints

The Skeleton • About 20% of body mass – 160 pound person would have about 30 pound skeleton • Classified into 2 parts – Axial and Appendicular

The Axial Skeleton • 80 bones in 3 regions – Skull – Vertebral column – Bony thorax • Supports the head, neck, trunk • Protects the brain, spinal cord, and the organs in the thorax

The Axial Skeleton in Green Figure 5. 6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 20 b

The Skull • Most complex structure – 22 bones – mostly flat • Two sets of bones – Cranium – Facial bones

The Skull • Bones are joined by sutures – Except mandible • Sutures are interlocking joints – saw-toothed or serrated appearance • Only the mandible is attached by a freely movable joint

The Skull • • • Major skull sutures are Coronal Sagittal Squamous Lambdoid

The Skull • Cranial bones or cranium – Protects brain – Site of attachment for head and neck muscles

The Skull • Facial bones – Framework for face – Cavities for special sense organs of sight taste and smell – Openings for air and food passage – Secure teeth – Anchor facial muscles of expression

Anatomy of the Cranium • • Eight cranial bones – two Parietal two Temporal Frontal Occipital Sphenoid Ethmoid Cranial bones are thin and remarkably strong for their weight

Frontal Bone • Forms the anterior portion of the cranium • Articulates posteriorly with the parietal bones via the coronal suture • In yellow

Frontal Bone • Major markings – Frontal squama (forehead) – supraorbital margins – Supraorbital foramen – the anterior cranial fossa – the frontal sinuses – glabulla

Parietal Bones • Two curved retangular bones that form most of the superior and lateral aspects of skull • In Green

Parietal Bones and Major Associated Sutures • Four sutures mark the articulations of the parietal bones – Coronal suture – articulation between parietal bones and frontal bone anteriorly – Sagittal suture – where right and left parietal bones meet superiorly

Parietal Bones and Major Associated Sutures • Four sutures mark the articulations of the parietal bones – Lambdoid suture – where parietal bones meet the occipital bone posteriorly – Squamosal or squamous suture – where parietal and temporal bones meet

Skull: Posterior View Parietal bones in maroon Figure 7. 2 b

Occipital Bone • Forms most of skull’s posterior wall and base • Occiptal bone in brown Figure 7. 2 b

Occipital Bone • Forms most of skull’s posterior wall and base • Major markings – Posterior cranial fossa (inside) – Foramen magnum – Occipital condyles – Hypoglossal canal – External occipital protuberance (you can feel this) Figure 7. 2 b

Human Skull, Inferior View Figure 5. 9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 24

Temporal Bones • Temple and temporal are latin words for ‘time’ – Gray hair usually appears first at the temples

• Divided into four major Temporal regions – Squamous – Tympanic • Ear drum – Mastoid – Petrous • Contributes to the cranial base • Houses middle and inner ear cavities Bones

Human Skull, Inferior View Figure 5. 9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 24

Temporal Bones • Major markings – Zygomatic process (squamous region) • Zygomatic process meets zygomatic bone of face – you can feel this – your cheek bone

Temporal Bones • Major markings – Styloid process (needle like projection in the tympanic region)

Temporal Bones • Major markings – Mastoid process (felt as a lump posterior to the ear) – Mandibular fossae – Middle cranial fossae ( in Petrous region)

Temporal Bones • Major openings – stylomastoid foramina – jugular foramina – external and internal auditory meatuses (ear canal) – carotid canal

Sphenoid Bone • Butterfly-shaped bone that spans the width of the middle cranial fossa • Forms the central wedge that articulates with all other cranial bones • Consists of a central body, greater wings, lesser wings, and pterygoid processes • Major markings: the sella turcica, hypophyseal fossa, and the pterygoid processes • Major openings include the foramina rotundum, ovale, and spinosum; the optic canals; and the superior orbital fissure

Human Skull, Superior View Sphenoid Bone in pink Figure 5. 8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 23

Sphenoid Bone Figure 7. 6 a, b

Ethmoid Bone • Most deep of the skull bones; lies between the sphenoid and nasal bones • Forms most of the bony area between the nasal cavity and the orbits

Ethmoid Bone • Major markings – cribriform plate – crista galli – perpendicular plate – nasal conchae – ethmoid sinuses

Human Skull, Superior View Figure 5. 8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 23

Human Skull, Inferior View Figure 5. 9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 24

Wormian Bones • Also called sutural bones • Tiny irregularly shaped bones that appear within sutures • Structurally unimportant • Not all skulls exhibit them

Facial Bones

Facial Bones • Fourteen bones of which only the mandible and vomer are unpaired • The paired bones are the maxillae, zygomatics, nasals, lacrimals, palatines, and inferior conchae • Usually facial bones of men are more elongated than of women

Mandible and Its Markings • The mandible (lower jawbone) is the largest, strongest bone of the face

Mandible and Its Markings • Its major markings include the coronoid process, mandibular condyle, the alveolar margin, and the mandibular and mental foramina

Mandible and Its Markings • Dentists inject Novocain into the mandibular foramina to numb teeth

Maxillary Bones • Medially fused bones that make up the upper jaw and the central portion of the facial skeleton

Maxillary Bones • Facial keystone bones that articulate with all other facial bones except the mandible

Maxillary Bones • Their major markings include palatine, frontal, and zygomatic processes, the alveolar margins, inferior orbital fissure, and the maxillary sinuses

Zygomatic Bones • Irregularly shaped bones (cheekbones) that form the prominences of the cheeks and the inferolateral margins of the orbits In Teal

Other Facial Bones • Nasal bones – thin medially fused bones that form the bridge of the nose

Other Facial Bones • Lacrimal bones – contribute to the medial walls of the orbit and contain a deep groove called the lacrimal fossa that houses the lacrimal sac

Other Facial Bones • Palatine bones – two bone plates that form portions of the hard palate, the posterolateral walls of the nasal cavity, and a small part of the orbits

Other Facial Bones • Vomer – plowshaped bone that forms part of the nasal septum

Other Facial Bones • Inferior nasal conchae – paired, curved bones in the nasal cavity that form part of the lateral walls of the nasal cavity

Orbits • Bony cavities in which the eyes are firmly encased and cushioned by fatty tissue • Formed by parts of seven bones – frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid

Orbits Figure 7. 9 b

Nasal Cavity • Constructed of bone and hyaline cartilage • Roof – formed by the cribriform plate of the ethmoid

Nasal Cavity • Lateral walls – formed by the superior and middle conchae of the ethmoid, the perpendicular plate of the palatine, and the inferior nasal conchae • Floor – formed by palatine process of the maxillae and palatine bone

Paranasal Sinuses · Hollow portions of bones surrounding the nasal cavity Figure 5. 10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 25 a

Paranasal Sinuses • Mucosa-lined, air-filled sacs found in five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones

Paranasal Sinuses • Air enters the paranasal sinuses from the nasal cavity and mucus drains into the nasal cavity from the sinuses

Paranasal Sinuses • Lighten the skull and enhance the resonance of the voice and amplifies Figure 7. 11

Hyoid Bone • Not actually part of the skull, but lies just inferior to the mandible in the anterior neck • Only bone of the body that does not articulate directly with another bone • Attachment point for neck muscles that raise and lower the larynx during swallowing and speech

The Hyoid Bone · The only bone that does not articulate with another bone · Serves as a moveable base for the tongue Figure 5. 12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 26

The Fetal Skull · The fetal skull is large compared to the infants total body length Figure 5. 13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 27 a

The Fetal Skull · Fontanelles – fibrous membranes connecting the cranial bones · Allow the brain to grow · Convert to bone within 24 months after birth Figure 5. 13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 27 b

Quiz – Next time! Complete study guide Pages 143 - 150

Skull: Anterior View Figure 7. 2 a

Parietal Bones and Major Associated Sutures • Form most of the superior and lateral aspects of the skull Figure 7. 3 a

Occipital Bone and Its Major Markings Figure 7. 4 b

Anterior Aspects of the Skull Figure 7. 2 a

Posterior Aspects of the Skull Figure 7. 2 b

External Lateral Aspects of the Skull Figure 7. 3 a

Midsagittal Lateral Aspects of the Skull Figure 7. 3 b

Inferior Portion of the Skull Figure 7. 4 a

Inferior Portion of the Skull Figure 7. 4 b

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