Axial Skeleton

Basic Features

-Skeleton is divided into two sections

      -Axial skeleton and appendicular skeleton

-There are 206 separate bones

-Axial skeleton consists of 80 bones

-Appendicular skeleton consists of 126 bones

Basic Features

-Axial skeleton Consists of: skull bones/auditory ossicles/hyoid/vertebral column/thoracic cage

-Appendicular skeleton Consists of: limbs/pectoral girdle/pelvic girdle

Function of the Axial Skeleton

-Framework that supports and protects organs in the dorsal and ventral body cavities

-Protects special sense organs for taste, smell, hearing, balance, and vision

-Attachment sites for muscles that:

      -Adjust the posture of the head, neck, and trunk

      -Move the thoracic cage for respiration

      -Stabilize the appendicular skeleton

The Skull and Associated Bones Cranial and Facial Subdivisions of the Skull

-The skull consists of

Face

Cranium

Associated bones

The face: 14 individual bones

The cranium: 8 individual bones

The associated bones: 7 individual bones

Bones of the Cranium The bones that make up the cranium are: Frontal (single) Parietal (paired) Temporal (paired) Occipital (single) Sphenoid (single) Ethmoid (single) Sutures of the Skull Lambdoid suture Suture between the occipital and parietal bones Sagittal suture Suture between the parietal bones Coronal suture Suture between the frontal and parietal bones Sutures of the Skull Squamous suture Suture between the temporal bone and the parietal bones Frontonasal suture Suture between the nasal and frontal bones Bones of the Face The bones that make up the face are: Maxillae (paired) Palatine (paired) Nasal (paired) Inferior nasal conchae (paired) Zygomatic (paired) Lacrimal (paired) Vomer (single) Mandible (single) The Orbital and Nasal Complexes and the Hyoid Bone The Hyoid Bone The only bone in the human body that does not articulate with any other bone Bony projections of the hyoid bone Greater horn Lesser horn Body The Skulls of Infants, Children, and Adults Major features of the infant skull 4 major fontanel areas Membranous areas where sutures will eventually form Allow for distortion of the skull during childbirth Anterior fontanel (baby’s “soft spot”) Posterior fontanel Sphenoidal fontanels Mastoid fontanels The Vertebral Column The adult vertebral column is made up of 26 bones 24 vertebrae 7 cervical vertebrae 12 thoracic vertebrae 5 lumbar vertebrae 1 sacrum (5 fused vertebrae) 1 coccyx (3 to 5 fused vertebrae) The Vertebral Column Functional Anatomy of the Vertebral Column Encloses and protects the spinal cord Supports the skull Supports the weight of the head, neck, and trunk Transfers weight to the lower limbs Helps maintain the upright position of the body The Vertebral Column Spinal Curves There are 4 major curves of the vertebral column Cervical curve Thoracic curve Lumbar curve Sacral curve These curves, along with muscle attachment to the various vertebral processes, help to maintain balance The Vertebral Column Abnormal curvatures of the vertebral column Scoliosis Abnormal lateral curvature Kyphosis Exaggerated posterior curvature of the thoracic region Lordosis Exaggerated anterior curvature of the lumbar region The Vertebral Column Vertebral Anatomy The vertebral body Supports weight along the axis of the body An anterior structure A vertebral body is separated from another vertebral body by a pad of cartilage called the intervertebral disc The Vertebral Column Vertebral Anatomy The vertebral arch Forms the vertebral foramen Made of pedicle and lamina Spinous process projects posteriorly Transverse processes project laterally The Vertebral Column Vertebral Anatomy The articular processes Superior articular process Inferior articular process Vertebral articulation Vertebral bodies are separated by intervertebral discs This results in creating a space called the intervertebral foramen The Vertebral Column Vertebral Regions Numbering system of vertebrae Cervical region C1, C2, C3, etc. Thoracic region T1, T2, T3, etc. Lumbar region L1, L2, L3, etc. The Vertebral Column Cervical Vertebrae There are 7 Support the weight of the head Spinous processes are bifid except for C7 All have transverse foramen Two cervical vertebrae have specific names C1 is the atlas C2 is the axis The Vertebral Column The Atlas (C1) Articulates with the occipital condyles of the skull Does not have a body Has the largest vertebral foramen of all vertebrae Allows the head to nod in a “yes” manner The Axis (C2) Has a dens The transverse ligament binds the dens to the atlas Allows the head to move in a “no” manner The Vertebral Column Thoracic Vertebrae There are 12 All have rib articulation points They support the ribs Most spinous processes point inferiorly The Vertebral Column Lumbar Vertebrae There are 5 Support the weight of the torso Vertebral bodies are quite large Spinous process points posteriorly The Vertebral Column The Sacrum There is one sacrum but consists of five fused vertebrae Structures of the sacrum Ala Sacral promontory The Vertebral Column The Coccyx Consists of 3-5 fused vertebrae Adult male coccyx points anteriorly Adult female coccyx points inferiorly The Thoracic Cage The thoracic cage has two functions It protects the heart, lungs, thymus, and other structures within the cavity It serves as the attachment site for muscles involved in: Respiration Positioning the vertebral column Movements of the pectoral girdle and upper limb The Thoracic Cage The Ribs Two types of rib classification Ribs (one type of classification) True ribs: 1–7 False ribs: 8–12 The Thoracic Cage The Ribs 12 pairs of ribs Each rib articulates with a thoracic vertebra Structures of a rib Head Neck Tubercle Angle Body The Thoracic Cage The Sternum Consists of Manubrium Jugular notch Body Xiphoid process Begins as hyaline cartilage Ossifies into bone by 60-70 years old