Bones, Part 1: The Axial Skeleton

Composed of 206 named bones grouped into two divisions The Skeleton Consists of Bones, cartilage, joints, and ligaments Composed of 206 named bones grouped into two divisions Axial skeleton (80 bones) Appendicular skeleton (126 bones) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Formed from 80 named bones The Axial Skeleton Formed from 80 named bones Consists of skull, vertebral column, and bony thorax Figure 7.1a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Axial Skeleton Figure 7.1b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Projections that provide attachment for muscles and ligaments Bone Markings Projections that provide attachment for muscles and ligaments Projections that help form joints Depressions and openings for passage of nerves and blood vessels Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Formed by cranial and facial bones The Skull Formed by cranial and facial bones Figure 7.2a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Cranium The cranium serves to Enclose brain Provide attachment sites for some head and neck muscles Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Face Facial bones serve to Form framework of the face Form cavities for the sense organs of sight, taste, and smell Provide openings for the passage of air and food Hold the teeth in place Anchor muscles of the face Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of Skull Geography Facial bones form anterior aspect Cranium is divided into cranial vault and the base Internally, prominent bony ridges divide skull into distinct fossae Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of Skull Geography The skull contains smaller cavities Middle and inner ear cavities – in lateral aspect of cranial base Nasal cavity – lies in and posterior to the nose Orbits – house the eyeballs Air-filled sinuses – occur in several bones around the nasal cavity Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of Skull Geography The skull contains approximately 85 named openings Foramina, canals, and fissures Provide openings for important structures Spinal cord Blood vessels serving the brain 12 pairs of cranial nerves Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Formed from eight large bones Cranial Bones Formed from eight large bones Paired bones include Temporal bones Parietal bones Unpaired bones include Frontal bone Occipital bone Sphenoid bone Ethmoid bone Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Forms the forehead and roofs of the orbits Forms superciliary arches Frontal Bones Forms the forehead and roofs of the orbits Forms superciliary arches Internally, it contributes to the anterior cranial fossa Contains frontal sinuses Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Parietal Bones and Sutures Parietal bones form superior and lateral parts of skull Four sutures of the cranium Coronal suture – runs in the coronal plane Located where parietal bones meet the frontal bone Squamous suture – occurs where each parietal bone meets a temporal bone inferiorly Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Parietal Bones and Sutures Sutures of the cranium (continued) Sagittal suture – occurs where right and left parietal bones meet superiorly Lambdoid suture – occurs where the parietal bones meet the occipital bone posteriorly Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Small bones that occur within sutures Sutural Bones Small bones that occur within sutures Irregular in shape, size, and location Not all people have sutural bones Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Skull – Posterior View Figure 7.2b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Forms the posterior portion of the cranium and cranial base Occipital Bone Forms the posterior portion of the cranium and cranial base Articulates with the temporal bones and parietal bones Forms the posterior cranial fossa Foramen magnum located at its base Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Features and structures Occipital Bone Features and structures Occipital condyles Hypoglossal foramen External occipital protuberance Superior nuchal lines Inferior nuchal lines Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Inferior Aspect of the Skull Figure 7.4a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lie inferior to parietal bones Temporal Bones Lie inferior to parietal bones Form the inferolateral portion of the skull Term “temporal” Comes from Latin word for time Specific regions of temporal bone Squamous, temporal, petrous, and mastoid regions Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lateral Aspect of the Skull Figure 7.3a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Temporal Bone Figure 7.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones, Part 1: The Axial Skeleton

Spans the width of the cranial floor Resembles a butterfly or bat The Sphenoid Bone Spans the width of the cranial floor Resembles a butterfly or bat Consists of a body and three pairs of processes Contains five important openings Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Sphenoid Bone Figure 7.6a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Sphenoid Bone Figure 7.6b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lies between nasal and sphenoid bones The Ethmoid Bone Lies between nasal and sphenoid bones Forms most of the medial bony region between the nasal cavity and orbits Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Ethmoid Bone Figure 7.7 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones of the Skull Table 7.1 (1 of 2) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Facial Bones Unpaired bones Paired bones Mandible and vomer Maxillae Zygomatic bones Nasal bones Lacrimal bones Palatine bones Inferior nasal conchae Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The lower jawbone is the largest and strongest facial bone Mandible The lower jawbone is the largest and strongest facial bone Composed of two main parts Horizontal body Two upright rami Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Mandible Figure 7.8a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Articulate with all other facial bones except the mandible Maxillary Bones Articulate with all other facial bones except the mandible Contain maxillary sinuses – largest paranasal sinuses Forms part of the inferior orbital fissure Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Maxillary Bones Figure 7.8b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Maxillary Bones Figure 7.4a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Other Bones of the Face Zygomatic bones Nasal bones Lacrimal bones Form lateral wall of orbits Nasal bones Form bridge of nose Lacrimal bones Located in the medial orbital walls Palatine bones Complete the posterior part of the hard palate Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Inferior nasal conchae Other Bones of the Face Vomer Forms the inferior part of the nasal septum Inferior nasal conchae Thin, curved bones that project medially form the lateral walls of the nasal cavity Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Facial Bones Table 7.1 (2 of 2) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones, Part 1: The Axial Skeleton

Bones of the Face Figure 7.2a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Special Parts of the Skull Orbits Nasal cavity Paranasal sinuses Hyoid bone Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Nasal Cavity Figure 7.9a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Nasal Septum Figure 7.9b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Orbits Figure 7.10b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Air-filled sinuses are located within Paranasal Sinuses Air-filled sinuses are located within Frontal bone Ethmoid bone Sphenoid bone Maxillary bones Lined with mucous membrane Serve to lighten the skull Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Paranasal Sinuses Figure 7.11a, b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones, Part 1: The Axial Skeleton

Lies inferior to the mandible The Hyoid Bone Lies inferior to the mandible The only bone with no direct articulation with any other bone Acts as a movable base for the tongue Figure 7.12 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Formed from 26 bones in the adult The Vertebral Column Formed from 26 bones in the adult Transmits weight of trunk to the lower limbs Surrounds and protects the spinal cord Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Serves as attachment sites for muscles of the neck and back The Vertebral Column Serves as attachment sites for muscles of the neck and back Held in place by ligaments Anterior and posterior longitudinal ligaments Ligamentum flavum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Vertebral Column Figure 7.13 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Cushion-like pads between vertebrae Act as shock absorbers Intervertebral Discs Cushion-like pads between vertebrae Act as shock absorbers Compose about 25% of height of vertebral column Composed of Nucleus pulposus and annulus fibrosis Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Intervertebral Discs Nucleus pulposus The gelatinous inner sphere of intervertebral disc Enables spine to absorb compressive stresses Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Intervertebral Discs Annulus fibrosis An outer collar of ligaments and fibrocartilage Contains the nucleus pulposus Functions to bind vertebrae together, resist tension on the spine, and absorb compressive forces Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Ligaments and Intervertebral Discs Figure 7.14a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

May be caused by trauma to the spine Herniated Disc May be caused by trauma to the spine Aging is also a contributing factor Nucleus pulposes loses cushioning properties Anulus fibrosis weakens Figure 7.14c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Regions and Normal Curvatures Vertebral column is about 70 cm (28 inches) Vertebral column is divided into five major regions Cervical vertebrae 7 vertebrae of the neck region Thoracic vertebrae 12 vertebrae of the thoracic region Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Regions and Normal Curvatures Vertebral column is divided into five major regions (continued) Lumbar vertebrae 5 vertebrae of the lower back Sacrum Inferior to lumbar vertebrae Articulates with coxal bones Coccyx Most inferior region of the vertebral column Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Regions and Normal Curvatures Four distinct curvatures give vertebral column an S-shape Cervical and lumbar curvature Are concave posteriorly Thoracic and sacral curvatures Are convex posteriorly Curvatures increase the resilience of the spine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Regions and Normal Curvatures PLAY Spine (vertical) Figure 7.13 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

General Structure of Vertebrae PLAY Spine (horizontal) Figure 7.15 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones, Part 1: The Axial Skeleton

Regions Vertebral Characteristics Specific regions of the spine perform specific functions Types of movement that occur between vertebrae Flexion and extension Lateral flexion Rotation in the long axis Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Seven cervical vertebrae (C1 – C7) – smallest and lightest vertebrae C3 – C7 are typical cervical vertebrae Body is wider laterally Spinous processes are short and bifid (except C7) Vertebral foramen are large and triangular Transverse processes contain transverse foramina Superior articular facets face superoposteriorly Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Cervical Vertebrae Table 7.2a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Cervical Vertebrae Figure 7.17a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lacks a body and spinous process Supports the skull The Atlas C1 is termed the atlas Lacks a body and spinous process Supports the skull Superior articular facets receive the occipital condyles Allows flexion and extension of neck Nodding the head “yes” Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Atlas Figure 7.16a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Atlas Figure 7.16b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Has a body and spinous process The Axis Has a body and spinous process Dens (odontoid process) projects superiorly Formed from fusion of the body of the atlas with the axis Acts as a pivot for rotation of the atlas and skull Participates in rotating the head from side to side Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Axis Figure 7.16c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones, Part 1: The Axial Skeleton

Thoracic Vertebrae (T1 – T12) All articulate with ribs Have heart-shaped bodies from the superior view Each side of the body of T1 – T10 bears demifacts for articulation with ribs T1 has a full facet for the first rib T10 – T12 only have a single facet Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Thoracic Vertebrae Table 7.2b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Spinous processes are long and point inferiorly Thoracic Vertebrae Spinous processes are long and point inferiorly Vertebral foramen are circular Transverse processes articulate with tubercles of ribs Superior articular facets point posteriorly Inferior articular processes point anteriorly Allows rotation and prevents flexion and extension Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lumbar Vertebrae (L1 – L5) Bodies are thick and robust Transverse processes are thin and tapered Spinous processes are thick, blunt, and point posteriorly Vertebral foramina are triangular Superior and inferior articular facets directly medially Allows flexion and extension – rotation prevented Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lumbar Vertebrae Table 7.2c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lumbar Vertebrae Figure 7.17c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Shapes the posterior wall of pelvis Formed from 5 fused vertebrae Sacrum (S1 – S5) Shapes the posterior wall of pelvis Formed from 5 fused vertebrae Superior surface articulates with L5 Inferiorly articulates with coccyx Sacral promontory Where the first sacral vertebrae bulges into pelvic cavity Center of gravity is 1 cm posterior to sacral promontory Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Sacrum Sacral foramina Ventral foramina Dorsal foramina Passage for ventral rami of sacral spinal nerves Dorsal foramina Passage for dorsal rami of sacral spinal nerves Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Sacrum Figure 7.18a, b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Formed from 3 – 5 fused vertebrae Coccyx Is the “tailbone” Formed from 3 – 5 fused vertebrae Offers only slight support to pelvic organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones, Part 1: The Axial Skeleton

Forms the framework of the chest Components of the bony thorax Thoracic vertebrae – posteriorly Ribs – laterally Sternum and costal cartilage – anteriorly Protects thoracic organs Supports shoulder girdle and upper limbs Provides attachment sites for muscles Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Bony Thorax Figure 7.19a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Bony Thorax Figure 7.19b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Formed from three sections Sternum Formed from three sections Manubrium – superior section Articulates with medial end of clavicles Body – bulk of sternum Sides are notched at articulations for costal cartilage of ribs 2–7 Xiphoid process – inferior end of sternum Ossifies around age 40 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Sternum Anatomical landmarks Jugular notch Sternal angle Central indentation at superior border of the manubrium Sternal angle A horizontal ridge where the manubrium joins the body Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

All ribs attach to vertebral column posteriorly True ribs - superior seven pairs of ribs Attach to sternum by costal cartilage False ribs – inferior five pairs of ribs Ribs 11–12 are known as floating ribs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Ribs Figure 7.20a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Ribs Figure 7.20b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of the Axial Skeleton Abnormal spinal curvatures Scoliosis – an abnormal lateral curvature Kyphosis – an exaggerated thoracic curvature Lordosis – an accentuated lumbar curvature – “swayback” Stenosis of the lumbar spine A narrowing of the vertebral canal Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Axial Skeleton Throughout Life Membrane bones begin to ossify in second month of development Bone tissue grows outward from ossification centers Fontanels Unossified remnants of membranes Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Fontanels Figure 7.21a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Fontanels Figure 7.21b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Axial Skeleton Throughout Life Many bones of the face and skull form by intramembranous ossification Endochondral bones of the skull Occipital bone Sphenoid Ethmoid bones Parts of the temporal bone Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Axial Skeleton Throughout Life Curvatures of the vertebral column Primary curvatures – thoracic and sacral curvatures An infant's spine is C-shaped at birth Secondary curvatures – cervical and lumbar curvatures Develop when a baby begins to walk Redistributes weight of the upper body over the lower limbs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Axial Skeleton Throughout Life Aging of the axial skeleton Water content of the intervertebral discs decreases By age 55, loss of a few centimeters in height is common Thorax becomes more rigid Bones lose mass with age Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings