BONE PT1
Axial Skeleton - Study Notes
Introduction
Axial Skeleton is a major part of the human skeletal system, comprised primarily of bones that form the skull, vertebral column, and rib cage.
Osseous Tissue - Compact Bone
Key Structures:
Osteocyte in Lacuna: Mature bone cell located in small cavities (lacunae) within the bone matrix.
Osteon: The basic structural unit of compact bone, characterized by a central canal surrounded by concentric lamellae.
Central Canal: The central channel of an osteon containing blood vessels and nerves.
Lamella: The layers of bone matrix in an osteon.
Canaliculi: Microscopic channels that connect lacunae, allowing for the exchange of nutrients and waste.
Bone Vocabulary and Directional Terms
Directional Terms:
Supra: Above.
Infra: Below.
Openings:
Foramen: A hole in a bone.
Meatus: A passageway in a bone.
Projections:
Process: An outgrowth from a bone.
Protuberance: A bulge or raised area on a bone.
Condyle: A rounded protuberance at the end of a bone.
Depressions:
Fossa: A shallow depression in a bone.
Notch: A deep indentation in a bone.
Other Terms:
Orbital: Pertaining to the eye socket.
Optic: Related to the eye.
Suture: A junction between bones.
Concha: Shell-like structures within the nasal cavity.
Superficial Skull - Bones
Bones Identified:
Frontal Bone: Forms the forehead.
Zygomatic Bones (x2): Cheekbones.
Maxilla Bone: Upper jawbone.
Mandible Bone: Lower jawbone.
Parietal Bones (x2): Form sides and roof of the skull.
Temporal Bones (x2): Located at the sides and base of the skull.
Nasal Bones (x2): Form the bridge of the nose.
Sphenoid Bone: Bat-shaped bone at the base of the skull.
Occipital Bone: Forms the back of the skull.
Base of the Skull - Bones (Inferior View)
Bones Identified:
Occipital Bone: Forms the base.
Temporal Bones (x2): Located laterally.
Maxilla Bone: Upper jawbone located anteriorly.
Zygomatic Bones (x2): Lateral cheek area.
Sphenoid Bone: Located centrally at the base.
Palatine Bone: Forms part of the hard palate.
Vomer: Forms the nasal septum.
Base of the Skull - Bones (Superior View)
Bones Identified:
Ethmoid Bone: Forms part of the cranial base and nasal cavity.
Sphenoid Bone: Central location at the base of the skull.
Occipital Bone: At the back base.
Frontal Bone: In the forehead area.
Temporal Bones (x2): Lateral sides behind the eyes.
Parietal Bones (x2): Form the sides and roof of the skull.
Skull Sutures
Sutures Identified:
Sagittal Suture: Separates the parietal bones.
Lambdoidal Suture: Between parietal and occipital bones.
Coronal Suture: Between frontal and parietal bones.
Squamosal Suture: Between parietal and temporal bones.
Superficial Skull - Bone Markings
Identified Markings:
Supraorbital Foramen (x2): Opening above each orbit.
Zygomatic Process of Temporal Bone (x2): Lateral extension.
Temporal Process of Zygomatic Bone (x2): Projects toward the temporal bone.
Infraorbital Foramen (x2): Located below the eye sockets.
Mental Foramen (x2): Opening in the mandible.
Zygomatic Arch: Framework including the temporal and zygomatic processes.
External Auditory Meatus: Ear canal.
Mastoid Process: Bony prominence behind the ear.
Styloid Process: Long, pointed projection beneath the ear.
The Mandible
Key Features:
Mental Foramen (x2): Openings in the mandible.
Coronoid Process (x2): Triangle-shaped projection.
Mandibular Condyle (x2): Articulates with the cranium.
Mandibular Notch (x2): Curved area between processes.
Deep Skull - Bones of the Orbit
Bones Identified:
Lacrimal Bone (x2): Small bone forming part of the eye socket.
Sphenoid Bone: Floor of the eye socket.
Zygomatic Bone (x2): Lateral aspect of the eye socket.
Frontal Bone: Superior aspect of the eye socket.
Maxilla Bone: Inferior part of the eye socket.
Ethmoid Bone: Contributes to the medial wall of the orbit.
Palatine Bone: Contributes to the floor of the orbit.
Deep Skull - The Ethmoid Bone and Nasal Concha (Anterior View)
Structures Identified:
Middle Nasal Conchae: Bony structures that aid in filtering air.
Perpendicular Plate: Forms part of the nasal septum.
Inferior Nasal Conchae: Separate bones aiding in air passage.
Crista Galli: Superior projection of the ethmoid bone.
Superior Nasal Conchae: Conchae formed by the ethmoid bone.
Deep Skull - The Ethmoid Bone and Nasal Concha (Superior View)
Components Viewed:
Cribriform Plate: Located horizontally within the ethmoid bone.
Crista Galli: Superior midline projection.
Perpendicular Plate: Forms part of the nasal septum.
Deep Skull - Sphenoid Bone (Superficial View)
Structures Identified:
Greater Wings: Extend laterally from the body of sphenoid.
Lesser Wings: Smaller extensions above the greater wings.
Sella Turcica: Depressed area containing the pituitary gland.
Optic Foramen: Opening for the optic nerve to pass.
The Hyoid Bone
Singular U-Shaped Bone located in the neck, unique as it does not directly articulate with any other bone; supports the tongue and assists in swallowing.
Vertebral Column
Regions Identified:
Cervical vertebrae (C1 to C7): 7 vertebrae of the neck region (Atlas C1, Axis C2).
Thoracic vertebrae (T1 to T12): 12 vertebrae of the upper and mid-back.
Lumbar vertebrae (L1 to L5): 5 vertebrae of the lower back.
Os Sacrum: Fusion of sacral vertebrae.
Coccyx: Tailbone, fusion of coccygeal vertebrae.
Curvatures:
Cervical curve: Curved forward.
Thoracic curve: Curved backward.
Lumbar curve: Curved forward.
Sacral curve: Curved backward.
Cervical Vertebrae
Atlas (C1) Key Features:
Vertebral Foramen: Large opening for spinal cord.
Anterior Arch: Front part of the atlas.
Posterior Arch: Back part of the atlas.
Transverse Process: Side projections.
Transverse Foramen: Unique features for vertebral arteries.
Superior Articular Process: Articulates with the occipital bone.
Axis (C2) Key Features:
Dens (Odontoid Process): Projection allowing rotation of the head.
Vertebral Foramen: Opening matching Atlas.
Body: Central part of the vertebra.
Transverse Processes: Side projections.
Bifid Spinous Process: Notched spinous process for C2.
C3-C7 General Features:
Pedicles: Short bony projections connecting the body to processes.
Superior Articular Processes: For articulation with adjacent vertebrae.
Vertebral Foramen: Size and shape vary.
Laminae and Spinous Process: Thin plates supporting and directing vertebrae.
Thoracic Vertebrae
Key Features:
Laminae: Thin bony plates forming part of the vertebral arch.
Transverse Processes: For connecting ribs.
Pedicles: Connecting bony structures to the vertebrae body.
Spinous Processes: Long bony projections posteriorly.
Vertebral Foramen: More circular than cervical vertebrae.
Lumbar Vertebrae
Key Features:
Vertebral Foramen: Larger than in thoracic but smaller than cervical.
Pedicles: Thick bony links between the body and processes.
Laminae: Boards connecting spinous and transverse processes.
Spinous Processes: Shorter than thoracic; more robust for muscle attachment.
Body: Largest and strongest support of the vertebral column.
Sacrum and Coccyx
Sacrum: Composed of five fused vertebrae in adults, forming the back part of the pelvis.
Coccyx: Composed of three to five small vertebrae fused together, known as the tailbone.
Sternum
Anatomy Identified:
Manubrium: Upper section of the sternum.
Body: The central part of the sternum.
Xiphoid Process: The lowermost section of the sternum.
Rib Anatomy
Key Features:
Costal Angle: The bend of the rib.
Costal Groove: Groove along the rib for nerves and vessels.
Head: Articulates with thoracic vertebrae.
Tubercle: Projection for rib articulation.
Neck: Area between the head and tubercle.
Articular facets: Surfaces for articulation with vertebrae.
Shaft: The long, slender part of the rib.
Articulation with Costal Cartilage: Connects rib to sternum.
Ribs Types
True Ribs: Ribs 1-7 directly attached to the sternum.
False Ribs: Ribs 8-10 indirectly attached to the sternum via costal cartilage.
Floating Ribs: Ribs 11-12 do not attach to the sternum.