The Skeleton Chapter 7 Part A

The Skeleton Skeleton = Greek for ‘dried up body’ or ‘mummy’               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 Axial Skeleton in Green Slide 5.20b Figure 5.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 7.2b

Occipital Bone Forms most of skull’s posterior wall and base Occiptal bone in brown Figure 7.2b

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 7.2b

Human Skull, Inferior View Figure 5.9 Slide 5.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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

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

Human Skull, Inferior View Figure 5.9 Slide 5.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 Slide 5.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Sphenoid Bone Figure 7.6a, 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 Slide 5.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Human Skull, Inferior View Figure 5.9 Slide 5.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 – plow-shaped 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 7.9b

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 Slide 5.25a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 Slide 5.26 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The Fetal Skull The fetal skull is large compared to the infants total body length Figure 5.13 Slide 5.27a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 5.27b

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

Skull: Anterior View Figure 7.2a

Parietal Bones and Major Associated Sutures Form most of the superior and lateral aspects of the skull Figure 7.3a

Occipital Bone and Its Major Markings Figure 7.4b

Anterior Aspects of the Skull Figure 7.2a

Posterior Aspects of the Skull Figure 7.2b

External Lateral Aspects of the Skull Figure 7.3a

Midsagittal Lateral Aspects of the Skull Figure 7.3b

Inferior Portion of the Skull Figure 7.4a

Inferior Portion of the Skull Figure 7.4b

Quiz – Next time! Complete study guide