Chapter 7: The Axial Skeleton part 1

The Axial Skeleton - longitudinal axis Supports and protects organs in body cavities Attaches to muscles of: head, neck, and trunk respiration appendicular skeleton

Bones of the Axial Skeleton - 80 The skull: 8 cranial bones 14 facial bones The thoracic cage: 24 ribs the sternum Bones associated with the skull: 6 auditory ossicles the hyoid bone The vertebral column: 24 vertebrae the sacrum the coccyx

The Skull The skull protects: Has 22 bones: the brain entrances to respiratory and digestive system Has 22 bones: 8 cranial bones: form the braincase or cranium 14 facial bones: protect and support entrances to digestive and respiratory tracts

Cranial Bones

1. The Frontal Bone Forms the anterior cranium and upper eyesockets Contains frontal sinuses Figure 7–6

The Frontal Bone-con’t Marks Frontal squama/glabella (forehead) Supraorbital margin (protects eye) Lacrimal fossa (for tear ducts)

2-3. The Parietal Bones forms part of the superior and lateral surfaces of the cranium

4-5. The Temporal Bones Part of lateral walls of cranium and zygomatic arches Surround and protect inner ear Attach muscles of jaws and head Figure 7–7

Marks Mandibular fossa-articulates with the mandible Zygomatic process: inferior to the squamous portion articulates with temporal process of zygomatic bone forms zygomatic arch (cheekbone)

Mastoid process: Styloid process: Auditory ossicles: for muscle attachment contains mastoid air cells connected to middle ear Styloid process: to attach tendons and ligaments of the hyoid, tongue and pharynx Auditory ossicles: 3 tiny bones in tympanic cavity (middle ear) transfer sound from tympanic membrane to inner ear

Foramina Carotid canal: Foramen lacerum: for internal carotid artery for carotid and small arteries hyaline cartilage auditory tube

Cranial Bones - 8 6. The Occipital Bone Marks Foramina Forms posterior/inferior surfaces of cranium Largest cranial bone Marks Occipital condyles -articulate with neck Inferior and superior nuchal lines -to attach ligaments External occipital protuberance(Inion)- for trapezius attachment External occipital crest -to attach ligaments Foramina Foramen magnum-connects cranial and spinal cavities

7. The Sphenoid Part of the floor of the cranium Unites cranial and facial bones Strengthens sides of the skull Contains sphenoidal sinuses Figure 7–8

Marks Sphenoid body: at the central axis of the sphenoid Sella turcica: saddle-shaped enclosure on the superior surface of the body Lesser wings: anterior to the sella turcica Greater wings: form part of the cranial floor sphenoidal spine posterior wall of the orbit Hypophyseal fossa: a depression within the sella turcica holds the pituitary gland Sphenoidal sinuses: either side of the body inferior to the sella turcica

7. The Ethmoid Forms anteromedial floor of the cranium Roof of the nasal cavity Part of the nasal septum and medial orbital wall Contains ethmoidal (sinuses) Figure 7–9

Foramina Optic canals: Superior orbital fissure: Foramen rotundum: for optic nerves Superior orbital fissure: For blood vessels and nerves of the orbit Foramen rotundum: for blood vessels and nerves of the face Foramen ovale: for blood vessels and nerves of the face Foramen spinosum: for blood vessels and nerves of the jaws

Ethmoid Cribiform plate roof of the nasal cavity -contains crista galli Perpendicular plate is part of the nasal septum Olfactory foramina in the cribriform plate for olfactory nerves

The 4 Major Sutures (immovable joints of the skull) Lambdoid suture-separates occipital from parietal bones Coronal suture-attaches frontal bone to parietal bones Sagittal suture-between the parietal bones lambdoid suture to coronal suture Squamous suture-form boundaries between temporal bones and parietal bones

The Infant Skull Grows rapidly Is large compared to the body Has many ossification centers Fusion is not complete at birth: 2 frontal bones 4 occipital bones several sphenoid and temporal elements Figure 7–15

Fontanels Are areas of fibrous connective tissue (soft spots) Cover unfused sutures in the infant skull Allow the skull to flex during birth Anterior fontanel-frontal, sagittal, and coronal sutures Occipital fontanel-lambdoid and sagittal sutures

The Facial Bones Superficial facial bones for muscle attachment Maxillary Lacrimal Nasal Zygomatic Mandible Deep facial bones separate the oral and nasal cavities & form the nasal septum Palatine bones Inferior nasal conchae Vomer

Facial Bones - 14 Maxillary (2) - Functions Support upper teeth Form inferior orbital rim Form lateral margins of external nares Form upper jaw and hard palate Contain maxillary sinuses (largest sinuses) -failure to fuse results in cleft palate Figure 7–10a

Marks Anterior nasal spine-attaches cartilaginous anterior nasal septum Alveolar processes-borders the mouth, supports upper teeth -Maxillary sinuses-to lighten bone -Infraorbital foramen: for sensory nerve to brain (via foramen rotundum of sphenoid)

The Palatine Bones (2) Functions Form the posterior portion of the hard palate Contribute to the floors of the orbits Figure 7–10b,c

Nasal Bones- 2 -Support the bridge of the nose Connect to cartilages of the distal part of the nose (external nares)

Vomer (1) Forms the inferior portion of the bony nasal septum

Inferior Nasal Conchae (2) -create air turbulence in the nasal cavity, increase the epithelial surface area, warm and humidify inhaled air

Zygomatic Bones (2) Contribute to the rim and lateral wall of the orbit Form part of the zygomatic arch Marks Temporal process

Lacrimal Bones (2) (smallest facial bones) Form part of the medial wall of the orbit Lacrimal sulcus: location of the lacrimal sac

milk eye squirt - YouTube

The Mandible (1) Articulations Forms the lower jaw Mandibular fossae of the temporal bones Body of the mandible - horizontal portion Alveolar processes - support the lower teeth Ramus - ascending from the mandibular angle on either side Figure 7–12a,b

Foramina Mental foramen-for sensory nerves of lips and chin Mandibular foramen-for blood vessels and nerves of lower teeth

The Hyoid Bone (assoc w/facial bones) Functions Supports the larynx Attaches muscles of the larynx, pharynx, and tongue Articulations Connects lesser horns to styloid processes of temporal bones