anatomy_axial_skeleton_pearson.ppt

PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
7
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Bones, Part 1:
The Axial
Skeleton
PART 1

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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)

The Axial Skeleton
 Formed from 80
named bones
 Consists of skull,
vertebral column,
and bony thorax
Figure 7.1a

The Axial Skeleton
Figure 7.1b

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 Figure 7.2a
The Skull
 Formed by cranial and facial bones

The Cranium
 The cranium serves to
 Enclose brain
 Provide attachment sites for some head and neck
muscles

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

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

 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

 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

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

Frontal Bones
 Forms the forehead and roofs of the orbits
 Forms superciliary arches
 Internally, it contributes to the anterior cranial
fossa
 Contains frontal sinuses

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

Sutural Bones
 Small bones that occur within sutures
 Irregular in shape, size, and location
 Not all people have sutural bones

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

Occipital Bone
 Features and structures
 Occipital condyles
 Hypoglossal foramen
 External occipital protuberunce
 Superior nuchal lines
 Inferior nuchal lines

Inferior Aspect of the Skull
Figure 7.4a

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

Lateral Aspect of the Skull
Figure 7.3a

The Temporal Bone
Figure 7.5

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

The Sphenoid Bone
Figure 7.6b

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 Figure 7.7
The Ethmoid Bone

Bones of the Skull
Table 7.1 (1 of 2)

Facial Bones
 Unpaired bones
 Mandible and vomer
 Paired bones
 Maxillae
 Zygomatic bones
 Nasal bones
 Lacrimal bones
 Palatine bones
 Inferior nasal conchae

Mandible
 The lower jawbone is the largest and strongest
facial bone
 Composed of two main parts
 Horizontal body
 Two upright rami

Mandible
Figure 7.8a

Maxillary Bones
 Articulate with all other facial bones except the
mandible
 Contain maxillary sinuses – largest paranasal
sinuses
 Forms part of the inferior orbital fissure

Maxillary Bones
Figure 7.8b

Maxillary Bones
Figure 7.4a

Other Bones of the Face
 Zygomatic 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

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

Bones of the Face
Figure 7.2a

Special Parts of the Skull
 Orbits
 Nasal cavity
 Paranasal sinuses
 Hyoid bone

Nasal Cavity
Figure 7.9a

Nasal Septum
Figure 7.9b

Orbits
Figure 7.10b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.12
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

The Vertebral Column
 Formed from 26 bones in the adult
 Transmits weight of trunk to the lower limbs
 Surrounds and protects the spinal cord

 Serves as attachment sites for muscles of the neck
and back
 Held in place by ligaments
 Anterior and posterior longitudinal ligaments
 Ligamentum flavum

Figure 7.13

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

 Nucleus pulposus
 The gelatinous inner sphere of intervertebral disc
 Enables spine to absorb compressive stresses

 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

Ligaments and Intervertebral Discs
Figure 7.14a

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

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

 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

 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

Figure 7.13
PLAY Spine (vertical)

General Structure of Vertebrae
PLAY Spine (horizontal)
Figure 7.15

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

Cervical Vertebrae
 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

Cervical Vertebrae
Table 7.2a

Cervical Vertebrae
Figure 7.17a

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”

The Atlas
Figure 7.16a

The Atlas
Figure 7.16b

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

The Axis
Figure 7.16c

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

Thoracic Vertebrae
Table 7.2b

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

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

Lumbar Vertebrae
Table 7.2c

Lumbar Vertebrae
Figure 7.17c

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

Sacrum
 Sacral foramina
 Ventral foramina
Passage for ventral rami of sacral spinal nerves
 Dorsal foramina
Passage for dorsal rami of sacral spinal nerves

Sacrum
Figure 7.18a, b

Coccyx
 Is the “tailbone”
 Formed from 3 – 5 fused vertebrae
 Offers only slight support to pelvic organs

Bony Thorax
 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

The Bony Thorax
Figure 7.19a

The Bony Thorax
Figure 7.19b

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

Sternum
 Anatomical landmarks
 Jugular notch
Central indentation at superior border of the
manubrium
 Sternal angle
A horizontal ridge where the manubrium joins the
body

Ribs
 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

Ribs
Figure 7.20a

Ribs
Figure 7.20b

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

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

Fontanels
Figure 7.21a

Fontanels
Figure 7.21b

 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

 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

 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

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