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Chapter 7: The Skeleton Part A The Axial Skeleton Consists of 80 bones Three major regions Skull Vertebral column Thoracic cage The Axial Skeleton Skull Thoracic cage (ribs and sternum) Vertebral column Sacrum Cranium Facial bones Clavicle Scapula Sternum Rib Humerus Vertebra Radius Ulna Carpals Phalanges Metacarpals Femur Patella Tibia Fibula (a) Anterior view Tarsals Metatarsals Phalanges Figure 7.1a The Skull Two sets of bones 1. Cranial bones 2. Enclose the brain in the cranial cavity Gives attachment sites for head and neck muscles 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 Bones of cranium (cranial vault) Coronal suture Squamous suture Lambdoid suture Facial bones (a) Cranial and facial divisions of the skull Figure 7.2a 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 Frontal bone Parietal bone Nasal bone Sphenoid bone (greater wing) Temporal bone Ethmoid bone Lacrimal bone Zygomatic bone Ethmoid bone Maxilla Mandible (a) Anterior view Vomer Mandibular symphysis Figure 7.4a 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. 2. 3. 4. Coronal suture—between parietal bones and frontal bone Sagittal suture—between right and left parietal bones Lambdoid suture—between parietal bones and occipital bone Squamous (squamosal) sutures—between parietal and temporal bones on each side of skull Coronal suture Parietal bone Frontal bone Sphenoid bone (greater wing) Ethmoid bone Temporal bone Lacrimal bone Lambdoid suture Squamous suture Occipital bone Zygomatic process Occipitomastoid suture Nasal bone Zygomatic bone Maxilla Mandible (a) External anatomy of the right side of the skull 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 Sagittal suture Parietal bone Sutural bone Lambdoid suture Occipital bone Occipitomastoid suture (b) Posterior view Figure 7.4b Maxilla Palatine bone Zygomatic bone Temporal bone (zygomatic process) Intermaxillary suture Median palatine suture Maxilla Sphenoid bone (greater wing) Vomer Temporal bone Parietal bone Foramen magnum (a) Inferior view of the skull (mandible removed) Figure 7.6a 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 mandible at 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/skullbon es.html Sagittal suture Parietal bone Sutural bone Lambdoid suture Occipital bone Occipitomastoid suture (b) Posterior view Figure 7.4b 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) Virgil Can Not Make My Pet Zebra Laugh! Mandible Lower jaw Largest, strongest bone of face Articulates at the temporomandibular joint (TMJ): only freely movable joint in skull Temporomandibular joint Ramus of mandible Mandibular angle Body of mandible (a) Mandible, right lateral view Figure 7.11a 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 Frontal bone Parietal bone Nasal bone Sphenoid bone (greater wing) Temporal bone Ethmoid bone Lacrimal bone Zygomatic bone Ethmoid bone Maxilla Mandible (a) Anterior view Vomer Mandibular symphysis Figure 7.4a 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 Maxilla Palatine bone Zygomatic bone Temporal bone (zygomatic process) Intermaxillary suture Median palatine suture Maxilla Sphenoid bone (greater wing) Vomer Temporal bone Parietal bone Foramen magnum (a) Inferior view of the skull (mandible removed) Figure 7.6a 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 Friendly Zebras Speed Past Elderly Lions Mating Roof of orbit • Lesser wing of sphenoid bone • Orbital plate of frontal bone Lateral wall of orbit • Zygomatic process of frontal bone • Greater wing of sphenoid bone • Orbital surface of zygomatic bone Medial wall • Sphenoid body • Orbital plate of ethmoid bone • Lacrimal bone Nasal bone Floor of orbit Zygomatic bone • Orbital surface of maxillary bone • Zygomatic bone (b) Contribution of each of the seven bones forming the right orbit 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 Frontal sinus Ethmoid bone Nasal bone Sphenoid bone Palatine bone (perpendicular plate) Maxillary bone (palatine process) Palatine bone (horizontal plate) (a) Bones forming the left lateral wall of the nasal cavity (nasal septum removed) Figure 7.14a Paranasal Sinuses Mucosa-lined, air-filled spaces Lighten the skull Enhance resonance of voice Found in frontal, sphenoid, ethmoid, and maxillary bones Frontal sinus Ethmoidal air cells (sinus) Sphenoid sinus Maxillary sinus (a) Anterior aspect Frontal sinus Ethmoidal air cells Sphenoid sinus Maxillary sinus (b) Medial aspect Figure 7.15 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 Skull The Cleft Lip and Palate Caused by right and left halves of the palate failing to fuse medially Leads to difficulties feeding/nursing Risk for aspiration (inhalation) pneumonia Review Slides
