Anatomy

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The Axial Skeleton

Objectives • Identify the bones of the axial skeleton and specify their functions. • Identify the bones of the cranium and face. • Describe the differences between adult, child, and infant skulls. • Identify and describe the curvatures of the spinal column. • Identify the vertebral regions and give characteristics of each. • Explain the articulations between the thoracic vertebrae, the ribs, and sternum.

Skeletal system includes both: • Axial skeleton – 80 Bones

• Skull – 28 bones • 8 cranial bones: frontal, parietal (2) occipital, temporal (2), sphenoid, ethmoid • 14 facial bones: nasal (2), maxillae (2), zygomatic (2), palatine (2), vomer,

inferior nasal conchae (2), lacrimal (2), mandible • Auditory ossicles (6 bones)

• 1 hyoid bone • Vertebral column- 24 vertebrae, sacrum, cocyx • Thoracic cage – 24 ribs and sternum

• Appendicular skeleton – 126 bones • Pectoral and pelvic girdles – 6 bones • Upper and lower limbs – 120 bones

• Total of 206 bones

The Axial Skeleton

The skull • Consists of the cranium and the bones of the face

• The cranium encloses cranial cavity or cranial vault • Facial bones surround and protect the entrances to the respiratory and digestive

tracts

Lab Experience

Locate the following axial skeleton landmarks on the plastic and natural bone specimens in the lab.

DO NOT use your pen or pencil to point, use the supplied pipe cleaners

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List of Cranial Bones and Landmarks

Region View Bone Bone Landmarks Cranium Frontal Frontal Supraorbital foramen

Nasal

Sphenoid Superior orbital fissure Inferior orbital fissure Optic foramen (canal)

Ethmoid Perpendicular plate Superior nasal concha Middle nasal concha

Inferior nasal concha

Lacrimal

Zygomatic

Mandible Body Ramus Alveolar processes Angle Mental foramen

Cranium Lateral Maxilla Infraorbital foramen

Mandible Coronoid process Condylar process/Articular surface Mandibular notch Body Ramus Mental foramen

Zygomatic Temporal process

Temporal Zygomatic process Styloid process Mastoid process External auditory (acoustic) meatus

Sphenoid Greater wing

Other Bones Nasal, Lacrimal, Occipital, Frontal

Other Landmarks Coronal suture, Squamous suture, Lambdoid suture, Sagittal suture (superior view)

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Region View Bone Bone Landmarks Cranial Floor Superior Frontal Frontal sinus (not always visible) w/ calvaria removed

Ethmoid Cribiform plate Olfactory foramina Crista galli

Sphenoid Sella turcica (Pituitary fossa) Greater wing Lesser wing

Temporal Pterous portion

Occipital Foramen magnum

Cranium Inferior Maxilla Palatine process (hard palate) w/ mandible removed Palatine Horizontal plate (hard palate)

Vomer

Sphenoid

Temporal Mastoid process Styloid process Mandibular process

Occipital External occipital protuberance Foramen magnum Occipital condyles

Orbit Frontal Orbital Bones Frontal, Maxilla, Zygomatic, Lacrimal, Ethmoid, Sphenoid, Palatine

Nasal Cavity Frontal Ethmoid Middle nasal concha, Perpindicular plate Boney septum Vomer Inferior nasal concha Nasal Sinuses Frontal Bones w/ sinuses Frontal sinus, Sphenoidal sinus,

Ethmoidal sinus, Maxillary sinus Sutures

Coronal - Between Frontal & Parietal Sagittal - Between Parietals Lambdoidal - Between Parietals & Occipital Squamous - Between Parietals & Temporals

Fetal Skull Anterior (frontal) fontanel Posterior (occipital) fontanel Sphenoidal (anterolateral) fontanel Mastoid (posterolateral) fontanel

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Vertebral Column Divisions

Cervical (7) Thoracic (12) Lumbar (5) Sacral (5 fused into 1 bone) & Coccygeal (3-5 fused into 1 bone)

Curves Each region has its own curve Primary Curves – Thoracic and sacral form “C” shape in infant Secondary Curves – Cervical develops when supporting head, lumbar develops when supporting body weight while sitting

Bony Landmarks Typical Vertebrae

Body Pedicle Lamina Vertebral arch Spinous process Transverse processes Superior articular process and facet Inferior articular process and facet Vertebral foramen Intervertebral notch – forms Intervertebral foramen when 2 vertebrae articulate

Regional Differences

Cervical Smallest C1 also called Atlas, C2 also called Axis form atlantoaxial joint C1 mostly a bony ring, C2 contains the Dens or Odontoid process Allows for turning head as in saying No C2 – C6 contain bifid spinous processes C7 has a large spinous process called vertebra prominens

Thoracic Medium sized Downward projecting spinous processes Presence of facets for rib articulations

Lumbar Largest Blunt projections

Sacrum Base Median sacral crest Apex Auricular surface Sacral foramina Ala or wing Sacral canal Sacral hiatus

Coccyx

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Thoracic Cage

Sternum Manibrium Jugular notch Body Clavicular notch Xiphoid process

Ribs 12 pair (in both male and female!) True ribs (vertebrosternal) – Ribs 1 – 7 False ribs (vertebrochondral) –Ribs 8-12 *Ribs 11 & 12 are floating ribs (false ribs, but not vertebrochondral)