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THE SKELETON. CHAPTER 7. Introduction . A strong, yet light, internal support for the human body The skeleton is adapted for the protection, locomotor, and manipulative functions The upright stance increases the ability of the skeletal muscle to resist gravity. Introduction .

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the skeleton



  • A strong, yet light, internal support for the human body
  • The skeleton is adapted for the protection, locomotor, and manipulative functions
  • The upright stance increases the ability of the skeletal muscle to resist gravity
  • The skeleton maintains its upright position through a series of compensating curves
  • The skeleton accounts for approximately 20% of the body mass
  • The 206 bones of the body are grouped into the axial and appendicular skeleton
Axial skeleton

Forms the long axis of the body

80 bones in three major regions


vertebral column

bony thorax




Bones of upper & lower extremities and girdles

126 bones in three major regions


Shoulder girdle

Pelvic girdle

upper extremity

lower extremity

the skull



the skull1
The Skull
  • The skull is the body’s most complex bony structure
  • It is formed by two sets of bones, the 8 cranial bones and the 14 facial bones
  • These 22 bones combine to form the cranial cavity and the facial features
  • In addition, there are 3 bones in each inner ear to assist in sound transmission
the skull introduction
The Skull: Introduction
  • The bones of the skull provide . . .
    • A case to house the brain, the cranium
    • A framework for the face
    • Cavities to house the organs of sight, taste, and smell
    • Passages for air and food
    • Attachment sites for the teeth
    • Attachment sites for muscle
the skull introduction1
The Skull: Introduction
  • Most bones of the skull are flat bones
  • Except for the mandible, all bones are firmly united by interlocking sutures
  • The major sutures of the skull are . . .
    • Coronal (Between Frontal & Parietal)
    • Sagittal (Between Parietal bones)
    • Squamosal (Between Parietal & Temporal)
    • Lambdoidal (Between Parietal & Occipital)
  • Other skull sutures connect facial bones and are named after these structures









overview of skull geography
Overview of Skull Geography
  • Facial bones form the anterior aspect
  • The cranial bones enclose the brain
  • The cranial vault or calvaria forms the superior, lateral, and posterior aspects of skull
  • The cranial base forming the inferior aspect of skull
cranial base
Cranial Base
  • Cranial base forms the skull’s inferior aspect
  • Three prominent ridges divide the base into fossae
  • The brain rests on these cranial fossae completely enclosed by the cranial vault
  • The brain occupies the cranial cavity
cavities of the skull
Cavities of the Skull
  • In addition to the large cranial cavity there are many smaller cavities
    • Middle and inner ear cavities
    • Nasal cavity
    • Orbits of the eyes
    • Several bones contain air filled sinuses
      • Sinuses surrounding the nasal cavity are referred to as the paranasal sinuses
study note
Study Note
  • As you read about the bones of the skull, locate each bone on the different skull views in Figures 7.2, 7.3, 7.4
  • The skull bones and their important markings and features are summarized in Table 7.1 on pages 213-214
  • The 8 cranial bones include; 2 parietal, 2 temporal frontal, occipital, sphenoid, ethmoid
  • Cranium is self- bracing allowing the bones to be thin, yet strong
frontal bone
Frontal bone
  • Forms the anterior portion of the cranium, the forehead, roofs of the orbits, and most of the anterior cranial fossa
frontal bone landmarks
Frontal bone - landmarks
  • Frontal squama
  • Supraorbital margins
  • Supraorbital foramen
  • Orbits
  • Anterior cranial fossa
  • Glabella
  • Frontal sinuses
parietal bones
Parietal bones


  • Forms most of the superior & lateral aspects of the skull
  • Articulates with other cranial bones to form four major sutures
parietal bones landmarks
Parietal bones - landmarks
  • The four largest sutures cranial sutures, Coronal, Sagittal, Lambdodial, Squamosal
occipital bone
Occipital bone
  • Forms most of the posterior wall and base of skull
  • Articulates with parietal & temporal
  • Joins w/ sphenoid in the cranial floor
  • Forms internal walls of posterior cranial fossa
occipital bone ext landmarks
Occipital bone - Ext. landmarks
  • Foramen magnum, Occipital condyles, External occipital protuberance, Nuchal lines, External occipital crest
occipital bone int landmarks
Occipital bone - Int. landmarks
  • Hypoglossal canal, Posterior cranial fossa
temporal bone
Temporal Bone
  • Forms the infero-lateral aspects of the skull
  • Parts of the cranial floor
  • Divided into four regions; squamous tympanic, mastoid, and petrous-(int)
temporal bone1
Temporal Bone
  • The internal petrous region contributes to the cranial base
  • The petrous region and the sphenoid bone form the middle cranial fossa
temporal bone landmarks
Temporal Bone - landmarks
  • Zygomatic process
    • Meets the zygomatic bone
    • Forms the cheek
  • Mandibular fossa
    • Receives condyle of mandible
temporal bone landmarks1
Temporal Bone - landmarks
  • External Auditory Meatus
    • Middle and inner ear
  • Styloid process
    • Muscle of tongue
  • Mastoid process
    • Muscles of neck
temporal bones landmarks
Temporal bones - landmarks
  • Jugular foramen
    • Entry point for the Jugular artery
  • Internal acoustic meatus
    • Entry point for the auditory nerve

Jugular Foramen

temporal bones landmarks1
Temporal bones - landmarks
  • Stylomastoid foramen
    • exit for facial nerve
  • Carotid canal
    • entrance for the carotid artery which supplies blood to cerebral hemispheres
sphenoid bone
Sphenoid bone
  • Bone spanning the width of middle cranial fossa
  • Articulates as central wedge of all cranial bones
  • Consists of central body and three processes; greater and lesser wings and pterygoid process (pos. view)
sphenoid landmarks
Sphenoid - landmarks
  • Sella turcica (enclosure for pituitary gland)
  • Optic foramina (passage of optic nerves)
  • Superior orbital fissure (Nerves III, IV, V enter orbit)
  • Foramen rotundum & ovale (Cranial Nerve V to face)
  • Foramen spinosum (Middle meningeal artery)
ethmoid bone
Ethmoid bone
  • Forms most of the area between the nasal cavity & orbits of eyes
  • Lies between nasal bones & sphenoid
  • Complex shape gives rise to nasal septum, sinuses and cribiform plate
ethmoid bone landmarks
Ethmoid bone - landmarks
  • Cribiform plates
    • Forms roof of nasal cavity
  • Olfactory formina
    • Olfactory nerves enter brain
  • Crista galli
    • Attachment of the dura mater which secures brain in cavity
ethmoid bone landmarks1
Ethmoid bone - landmarks
  • Perpendicular plate
    • Forms superior part of nasal septum
  • Lateral mass
    • House ethmoid sinuses
  • Nasal concha
    • Project into nasal cavity
  • Orbital plates
    • Medial walls of orbits
facial bones
Facial bones
  • Consists of 14 bones w/ only mandible and vomer unpaired
  • Others include maxillae, lacrimals, nasals, zygomatics, inferior nasal conchae, and palatines (not pictured)
  • Forms the lower jaw
  • Largest, strongest bone of the face
  • It has a body and two upwardly projecting sections called rami
  • Houses lower dentition
mandible landmarks
Mandible - landmarks
  • Mandibular angle
  • Mandibular notch
  • Coronoid process
  • Mandibular condyle
  • Alveolar margin
  • Mandible formina
  • Mental formina
  • Ramus of mandible
maxillary bone
Maxillary bone
  • Forms upper jaw and central portion of facial skeleton
  • Fused medially
  • Articulates with all facial bones except mandible
  • Upper dentition
  • Forms 2/3 of hard palate of the mouth





maxillary bones landmarks
Maxillary bones - landmarks
  • Alveolar margin
    • Upper dentition
  • Frontal process
    • Forms lateral aspects of nose
  • Zygomatic process
    • Articulates with zygomatic bone
  • Maxillary sinuses
    • (Fig. 7.11)
maxillary bones landmarks1
Maxillary bones - landmarks

Palatine Process

  • Palatine processes
    • Forms roof of mouth
  • Incisive fossa
    • Passage of nerves and blood vessels
  • Infraorbital foramen
    • Infraorbital nerve and blood vessel to face
maxillary bones landmarks2
Maxillary bones - landmarks
  • Inferior orbital fissure
    • Located deep within the orbit
    • Permits passage of the zygomatic nerve, maxillary nerve, and blood vessels to reach face
zygomatic bones
Zygomatic bones
  • Commonly called the cheekbones
  • Form prominences of cheeks and inferolateral margins of orbits
  • Articulate with the Zygomatic process of temporal bone and Zygomatic process of maxallae


Process of




nasal bones
Nasal bones
  • Forms bridge of the nose
  • Thin, rectangular shape
  • Fused medially
  • Articulate with the frontal bone and maxillary bones laterally
  • Nasal cartilages
    • (Fig. 6.1)
lacrimal bones
Lacrimal Bones
  • Forms part of the medial border of each orbit
  • Articulates with frontal, ethmoid & maxillae
  • Forms part of Lacrimal fossa
    • Permits tears to drain from orbit to nasal cavity
lacrimal bones1
Lacrimal Bones
  • Lacrimal fossa
    • Permits tears to drain from orbit to nasal cavity
palatine bones
Palatine bones
  • The horizontal plates forms the posterior portion of hard palate
  • Vertical plate forms part of the posterolateral wall of nasal cavity and a small portion of orbit
palatine bones landmarks
Palatine bones - landmarks
  • Horizontal plate
    • Posterior section of hard palate
  • Vertical plate
    • Part of the posteriolateral walls of nasal cavity
  • Orbital surface
    • Part of inferior medial aspect of orbit
  • Forms part of the nasal septum
  • Discussed with the nasal cavity
vomer landmarks
Vomer - landmarks
  • Plow shape
    • Divides nasal septum into right and left parts
inferior nasal conchae
Inferior Nasal Conchae
  • Form lateral walls of nasal cavity
  • Project medially from the lateral walls of nasal cavity
  • Largest of nasal conchae
inferior nasal conchae landmark
Inferior Nasal Conchae - Landmark
  • The Inferior nasal conchae is just one of three in the nasal cavity
  • Superior and middle concha are on the Ethmoid bone
the orbits
The Orbits
  • The orbits are bony cavities within which the eyes are encased and cushioned by fatty tissue
  • The muscles that move the eyes and the tear producing lacrimal glands are housed within the orbit
  • Formed by frontal, sphenoid, maxilla, zygomatic, lacrimal palatine & ethmoid
  • Contain superior & inferior orbital fissures
  • Optic foramina
nasal cavity
Nasal cavity
  • The nasal cavity is constructed of bone and hyaline cartilage
  • The cavity is divided into right and left parts by the nasal septum
  • Superior, middle and inferior nasal concha project into the cavity
  • The nasal septum and conchae are lined with mucus-secreting mucosa
nasal cavity1
Nasal cavity
  • Roof of the cavity is the cribriform plates of ethmoid
  • Lateral walls are the superior, middle, and inferior conchae, and vertical plates of palatines



nasal cavity2
Nasal cavity
  • Floor of cavity is formed by palatine processes of the maxillae and the palatine bones
  • Septum is formed by vomer and the perpendicular plate of ethmoid
paranasal sinuses
Paranasal sinuses
  • Five skull bones; frontal, sphenoid, ethmoid, and the paired maxillary contain mucus-lined, air-filled sinuses
  • Cluster around nasal cavity
  • Connected to nasal cavity to allow air to enter and mucus to drain
  • Lighten skull, warm and humidify air, enhance voice resonance
paranasal sinuses1
Paranasal sinuses
  • Note positioning around nasal cavity
paranasal sinuses2
Paranasal sinuses
  • Sphenoid sinus
  • Frontal sinus
  • Ethmoid sinus
  • Maxillary sinuses
hyoid bone
Hyoid bone
  • Not really a part of the skull, it is unique in that it is the only bone that does not articulate with any other bone
  • Positioned just inferior to the mandible
  • Anchored by stylohyoid ligaments to the styloid processes of temporal bone
  • Acts as a movable base for the tongue
hyoid bone1
Hyoid bone
  • Body
    • Neck muscle attachment
  • Greater horn
    • Neck muscle attachment
  • Lesser horn
vertebral column general characteristics
Vertebral Column:General Characteristics
  • Formed from 26 irregular bones
  • It contains four distinct curvatures
  • It provide axial support for the trunk
  • Transmits weight of trunk to lower limbs
  • Protects spinal cord
  • Attachment site for ribs and muscles
  • Separated by intervertebral discs
  • There are 24 vertebrae, a sacrum (5 fused) and a coccyx (4 fused)
general characteristics
General Characteristics
  • Alignment
    • Anterior/ posterior
    • Lateral
  • Curvatures
    • Compensatory curves
  • Features
    • Weight bearing
    • Muscle attachment
    • Protection
regional characteristics
  • Cervical C1-C7
    • Neck / movable
  • Thorasic T1-T12
    • Rib cage / limited movement
  • Lumbar L1-L5
    • Low back / movable
  • Sacral 5 fused
    • Joins the pelvis
  • Coccyx 4 fused
    • Terminus
clinical deviations
  • Scoliosis
    • An abnormal lateral curvature of the spinal column
    • Curvature can occur in an “S” or “C” deviation
clinical deviations1
Clinical deviations
  • Kyphosis
    • An exaggerated dorsal curvature in the dorsal region
    • Common is aged individuals because of osteoporosis
clinical deviations2
Clinical deviations
  • Lordosis
    • Accentuated lumbar curvature
    • Being overweight or pregnant causes an excessive load up front

Curves develop in response to:

Upright posture

Weight bearing


characteristics ligaments
Characteristics - Ligaments
  • Ligaments hold the vertebral column in an upright position
    • The broad Anterior Longitudinal Ligament prevents hyperextension and is quite strong
    • The cord like Posterior Longitudinal Ligament prevents hyperflexion and is relatively weak
characteristics ligaments1
Characteristics - Ligaments
  • Ligaments also connect specific vertebra and support disc position
    • Supraspinos ligament
    • Ligamentum flavum
    • Interspinous ligament
intervertebral discs
Intervertebral Discs
  • Intervertebral discs are cushion like pads interposed between vertebra
  • The discs provide elasticity and compressibility
  • Compression flattens discs
  • Discs are thickest in the cervical and lumbar to provide flexibility
characteristics discs
Characteristics - discs
  • Annulus fibrosus surrounds the outer margin
    • Collagen fibers
  • Nucleus pulposus is the semi fluid substance which shifts under body weight & pressure
  • Herniation of disc


of disk

general structure of vertebrae
General structure of vertebrae
  • Common pattern
    • Body or centrum
    • Vertebral arch
      • lamina
      • pedicle
    • Vertebral foramen
    • Spinous process
      • Muscles attach
    • Transverse process
      • Muscles attach
general structure of vertebrae1
General structure of vertebrae

Superior Articular


  • Interlocking pattern
    • Superior and inferior processes interlock
    • The inferior from above and the superior from the vertebrae below form a movable joint
    • The movement contributes to spinal rotation
general structure
General structure
  • Pedicles have notches on their superior and inferior borders
  • Lateral openings are called intervertebral foramen
    • Spinal nerves from spinal cord exit through these foramina
regional characteristic cervical
Regional Characteristic: Cervical
  • Body is oval, but wide side to side C3 - C7
  • Spinous process is short and bifid (split) except in C7
  • Vertebral foramen is triangular
  • Transverse processes contain foramina for blood vessels leading to brain
cervical vertebrae c1 and c2
Cervical Vertebrae C1 and C2
  • The first two cervical vertebrae are named the atlas and axis respectively
  • There is no intervertebral disc between them
  • They are highly modified for carrying the skull on top of the vertebral column
  • The atlas (C1) functions are a cradle to support the head
  • The axis (C2) functions as a pivot point for the rotation of the atlas
cervical vertebrae c1
Cervical Vertebrae C1
  • Lateral masses articulates with the occipital condyles of the skull
cervical vertebrae c11
Cervical Vertebrae C1

Body of the

Vertebrae is


  • Inferior articular surface articulates with C2 below
cervical vertebrae c2
Cervical Vertebrae C2
  • The axis has the odontoid process or dens is its unique feature
  • The dens is the missing body of the atlas which fuses with the atlas during embryonic development
regional characteristic cervical1
Regional Characteristic: Cervical
  • Spinous processes project directly posteriorly
  • Superior facets directed superoposteriorly
  • Inferior facets directed inferoanteriorly
  • Flexion/extension, lateral flexion and rotation
regional characteristic thoracic
Regional Characteristic: Thoracic
  • Body is larger than cervical; heart shaped
  • Spinous process is long and sharp
  • Vertebral foramen is circular
  • Transverse processes project posteriorly and bear facets for ribs
regional characteristic thoracic1
Regional Characteristic: Thoracic
  • Body bears two costal demifacets
  • Spinous processes projects inferiorly
  • Superior facets directed posteriorly
  • Inferior facets directed anteriorly
  • Rotation, limited lateral flexion, flexion/extension prevented
regional characteristic lumbar
Regional Characteristic: Lumbar
  • Body is massive and kidney shaped
  • Spinous processes are short and blunt
  • Vertebral foramen is triangular
  • Transverse processes are perpendicular to spinous process but has no special features
regional characteristic lumbar1
Regional Characteristic: Lumbar
  • Spinous process projects posteriorly
  • Superior facets directed medially
  • Inferior facets directed laterally
  • Flexion/extension, some lateral flexion, rotation prevented
  • The triangular shaped structure formed by five fused vertebrae
  • Forms the posterior wall of the pelvis
  • Articulates with L5 of the vertebral column
  • Articulates with the iliac bone of the pelvic girdle
  • Transfers the weight of the upper torso and limbs to the lower extremities


  • Ala are fused remnants of transverse processes that articulate with hip bones to form the sacro iliac joints of the pelvis
  • Sacral promontory
    • Center of gravity is 1 cm posterior of this point
  • Transverse line are sites of vertebral fusion
  • Sacral foramina transmit blood vessels and nerves



  • On the posterior aspect median sacral crest are fused spinous processes
  • The vertebral canal continues inside the sacrum as the sacral canal
  • Sacral hiatus is at the inferior end of the sacral canal
  • Superior articular surface form a joint with the spinal column
  • Coccyx articulates with sacrum
the bony thorax
The Bony Thorax
  • The thorax is the chest which includes
    • Thoracic vertebrae posteriorly
    • The ribs laterally
    • The sternum and costal cartilages anteriorly
  • It is cone shaped with its broad opening inferiorly
  • The thorax forms a bony cage around the heart, lungs and major blood vessels
functions of the bony thorax
Functions of The Bony Thorax
  • Protection
  • Attachment point for muscles of the back, chest, and shoulders
  • The intercostal muscles attach to the thorax to lift and depress the thorax during respiration
the sternum
The Sternum
  • The sternum lies in the anterior midline of the thorax
  • It is three fused bones
    • Manubrium
      • Jugular notch
      • Clavicular notch
    • Sternal body
      • Sternal angle
    • Xiphoid process
      • Xiphisternal joint
bony thorax
Bony Thorax
  • Thorax is the chest and its bony underpinnings is called the thoracic cage
  • Elements consist of the thoracic vertebrae, ribs, sternum, and costal cartilages which secure ribs to the sternum
  • A cone opening inferiorly, the thorax provides a protective cage around the vital organs of the thoracic cavity (heart, lungs, great blood vessels)
bony thorax continued
Bony Thorax - continued
  • Provides support for the shoulder girdles
  • Bony attachment points for muscles of the back, chest and shoulders
  • Intercostal spaces between ribs are occupied by the intercostal muscles which lift and depress the thorax during breathing
  • Located on the anterior midline of the thorax
  • Consists of three fused bones; manubrium, body, and xiphoid process
  • Manibrium articulates with clavicle & 2 ribs
  • Body with ribs 2 - 7
  • Xiphoid attachment site for abdominal muscle
  • Twelve pairs forming thoracic cage
  • All attach posteriorly to thoracic vertebrae
  • Curve inferiorly toward anterior body surface
  • Ribs 1-7 attach directly to sternum by separate costal cartilages and are referred to as true ribs
  • Ribs 8-10 attach indirectly to sternum by attaching to costal cartilages immediately above
  • Ribs 11-12 have no anterior attachments and are referred to as floating ribs
  • Ribs are bowed flat bones
  • Long shaft
  • Tear drop shaped with a costal groove on inner surface
  • Head of rib has 2 facets to articulate with its vertebrae as well as the one above
  • Neck is just beyond the head
  • Angle of rib
  • Costal cartilages attach rib to sternum
  • Attachments are secure but flexible
  • Tubercle of rib articulates with transverse process
  • Ligaments secure rib to transverse process
  • Note how the transverse processes of thoracic vertebrae are angled posteriorly
the appendicular skeleton
The Appendicular Skeleton
  • Appended to the axial skeleton
  • Pectoral girdle is for manipulation and is a lighter, less heavily reinforced structure
  • Pelvic girdle is for weight bearing and locomotion and is a heavier, more robust structure
  • Differences appear in bone structure, joint structure, ligaments, and muscle