Chapters 6 and 7

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal System Lab

An Introduction to the Axial Skeleton

Structures of Bones

ArticulationsContacts with other bones

Landmarks (Bone Markings; Marks)Areas of muscle and ligament attachment

ForaminaOpenings for nerves and blood vessels

Classification of BonesBones are classified by

Shape

Internal tissue organization

Bone markings (surface features; marks)

Classification of Bones

Figure 6–1 A Classification of Bones by Shape.

Classification of BonesBone Shapes

Long bonesAre long and thinAre found in arms, legs, hands, feet, fingers, and toes

Flat bonesAre thin with parallel surfacesAre found in the skull, sternum, ribs, and scapulae

Sutural bonesAre small, irregular bonesAre found between the flat bones of the skull

Classification of BonesBone Shapes

Irregular bonesHave complex shapes Examples: spinal vertebrae, pelvic bones

Short bonesAre small and thickExamples: ankle and wrist bones

Sesamoid bonesAre small and flatDevelop inside tendons near joints of knees, hands, and

feet

Classification of BonesBone Markings

Depressions or groovesAlong bone surface

ProjectionsWhere tendons and ligaments attach

At articulations with other bones

TunnelsWhere blood and nerves enter bone

Classification of Bones

Classification of Bones

Classification of BonesStructure of a Long Bone

Diaphysis The shaft A heavy wall of compact bone, or dense boneA central space called medullary (marrow) cavity

Epiphysis Wide part at each endArticulation with other bonesMostly spongy (cancellous) bone Covered with compact bone (cortex)

Metaphysis Where diaphysis and epiphysis meet

Classification of Bones

Figure 6–2 Bone Structure.

Classification of BonesStructure of a Flat Bone

The parietal bone of the skull

Resembles a sandwich of spongy bone

Between two layers of compact bone

Within the cranium, the layer of spongy bone

between the compact bone is called the diploë

Classification of Bones

Figure 6–2 Bone Structure.

Compact and Spongy BoneThe Structure of Compact Bone

Osteon is the basic unit Osteocytes are arranged in concentric lamellae

Around a central canal containing blood vessels

Perforating Canals:

perpendicular to the central canal

carry blood vessels into bone and marrow

Circumferential LamellaeLamellae wrapped around the long bone

Bind osteons together

Compact and Spongy Bone

Figure 6–4 The Histology of Compact Bone.

Compact and Spongy Bone

Figure 6–5a The Structure of Compact Bone.

Compact and Spongy BoneThe Structure of Spongy Bone

Does not have osteonsThe matrix forms an open network of

trabeculaeTrabeculae have no blood vesselsThe space between trabeculae is filled with red

bone marrow:Which has blood vesselsForms red blood cellsAnd supplies nutrients to osteocytes

Yellow marrowIn some bones, spongy bone holds yellow bone marrowIs yellow because it stores fat

Compact and Spongy Bone

Figure 6–6 The Structure of Spongy Bone.

Compact and Spongy BoneWeight-Bearing Bones

The femur transfers weight from hip joint to

knee joint

Causing tension on the lateral side of the shaft

And compression on the medial side

Compact and Spongy Bone

Figure 6–7 The Distribution of Forces on a Long Bone.

Compact and Spongy BoneCompact bone is covered with a

membranePeriosteum on the outside

Covers all bones except parts enclosed in joint capsulesIs made up of an outer, fibrous layer and an inner,

cellular layerPerforating fibers: collagen fibers of the periosteum:

connect with collagen fibers in boneand with fibers of joint capsules; attach

tendons, and ligaments

Compact and Spongy Bone

Figure 6–8a The Periosteum.

Compact and Spongy BoneFunctions of Periosteum

Isolates bone from surrounding tissues

Provides a route for circulatory and nervous

supply

Participates in bone growth and repair

Compact and Spongy BoneCompact bone is covered with a

membrane:Endosteum on the inside

An incomplete cellular layer:

lines the medullary (marrow) cavitycovers trabeculae of spongy bonelines central canalscontains osteoblasts, osteoprogenitor cells,

and osteoclastsis active in bone growth and repair

Compact and Spongy Bone

Figure 6–8b The Endosteum.

The Axial SkeletonThe axial skeleton

Forms the longitudinal axis of the body

Has 80 bonesThe skull:

8 cranial bones

14 facial bones

Bones associated with the skull: 6 auditory ossicles

the hyoid bone

The Axial SkeletonThe axial skeleton

The vertebral column 24 vertebrae (singular = vertebra) The sacrum The coccyx

The thoracic cage 24 ribs The sternum

The Axial Skeleton

Figure 7–1 The Axial Skeleton.

The Axial Skeleton

Figure 7–1 The Axial Skeleton.

The Axial SkeletonFunctions of the Axial Skeleton

Supports and protects organs in body cavities

Attaches to muscles of

Head, neck, and trunk

Respiration

Appendicular skeleton

The SkullThe skull protects

The brainEntrances to respiratory systemEntrance to digestive system

The skull contains 22 bones8 cranial bones:

Form the braincase or cranium 14 facial bones:

Protect and support entrances to digestive and respiratory tracts

The Skull

Figure 7–2 Cranial and Facial Subdivisions of the Skull.

The SkullSinuses

Cavities that decrease the weight of the skull Lined with mucous membranesProtect the entrances of the respiratory system

SuturesThe immovable joints of the skull The four major sutures

Lambdoid sutureCoronal sutureSagittal sutureSquamous suture

The Cranial Bones of the Skull

The Cranial BonesOccipital bone

Parietal bones

Frontal bone

Temporal bones

Sphenoid

Ethmoid

The Cranial Bones of the Skull

The Occipital BoneForamen MagnumOccipital CondylesExternal Occipital Protuberance

The Cranial Bones of the Skull

Figure 7–5a The Occipital and Parietal Bones.

The Cranial Bones of the Skull

The Parietal Bone

Figure 7–5b The Parietal Bone.

The Cranial Bones of the Skull

The Frontal boneFrontal squama (forehead)Supra-orbital margin (protects eye)Lacrimal fossa (for tear ducts)Frontal sinuses

The Cranial Bones of the Skull

Figure 7–6 The Frontal Bone.

The Cranial Bones of the Skull

The Temporal BonesSquamous part: borders the squamous suture

Mandibular fossa: articulates with the

mandible

Zygomatic processInferior to the squamous portion

Articulates with temporal process of zygomatic bone

Forms zygomatic arch (cheekbone)Mastoid process

For muscle attachmentContains mastoid air cells connected to middle ear

The Cranial Bones of the Skull

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Styloid process

To attach tendons and ligaments of the hyoid, tongue, and

pharynx

Petrous part

Encloses structures of the inner ear

Auditory ossicles

Three tiny bones in tympanic cavity (middle ear)

Transfer sound from tympanic membrane (eardrum) to inner earExternal acoustic meatus (canal): ends at tympanic membraneInternal acoustic meatus (canal)

For blood vessels and nerves of the inner earFacial nerve

The Cranial Bones of the Skull

Figure 7–7 The Temporal Bones.

The Cranial Bones of the Skull

The SphenoidSphenoid body

At the central axis of the sphenoid

Sella turcicaSaddle-shaped enclosureOn the superior surface of the body

Hypophyseal fossaA depression within the sella turcicaHolds the pituitary gland

The Cranial Bones of the Skull

Marks of the SphenoidSphenoidal sinuses

On either side of the bodyInferior to the sella turcica

Lesser wingsAnterior to the sella turcica

Greater wingsForm part of the cranial floorSphenoidal spinePosterior wall of the orbit

Pterygoid processesForm pterygoid platesTo attach muscles of the lower jaw and soft palate

The Cranial Bones of the Skull

Foramina of the Sphenoid Optic canals: for optic nervesSuperior orbital fissure: for blood vessels and

nerves of the orbitForamen rotundum: for blood vessels and

nerves of the faceForamen ovale: for blood vessels and nerves

of the faceForamen spinosum: for blood vessels and

nerves of the jaws

The Cranial Bones of the Skull

Figure 7–8 The Sphenoid.

The Cranial Bones of the Skull

Three Parts of the EthmoidThe cribriform plate

Floor of the craniumRoof of the nasal cavity Contains the crista galli

The two lateral massesEthmoidal labyrinth (ethmoidal air cells)Superior nasal conchae Middle nasal conchae

The perpendicular platePart of the nasal septum

The Cranial Bones of the Skull

Foramina of the Ethmoid

Olfactory foramina

In the cribriform plate

For olfactory nerves

The Cranial Bones of the Skull

Figure 7–9 The Ethmoid.

The Facial Bones of the SkullThe Facial Bones

Maxillae (maxillary bones)Palatine bonesNasal bonesVomerInferior nasal conchaeZygomatic bonesLacrimal bonesMandible

The Facial Bones of the SkullMarks of the Maxillae

Orbital rim:protects eye and orbitAlveolar processes: borders the mouth and

supports upper teethPalatine processes: form the hard palate (roof

of mouth)Maxillary sinuses: to lighten bone

The Facial Bones of the Skull

Figure 7–10a The Maxillae.

The Facial Bones of the SkullPalatine Bones

Horizontal plate: posterior part of hard palate

Perpendicular plate: from horizontal plate to

orbital process of orbit floor

The Facial Bones of the Skull

Figure 7–10c The Palatine Bones.

The Facial Bones of the SkullZygomatic Bones

Temporal process

Meets the zygomatic process of the temporal bone

The Facial Bones of the SkullThe Lacrimal Bones

Lacrimal sulcus:

location of the lacrimal sac

leads to the nasolacrimal canal (between orbit and

nasal cavity)

The Facial Bones of the SkullThe Nasal Bones

The VomerInferior Nasal Conchae

The Facial Bones of the Skull

Figure 7–11 The Smaller Bones of the Face.

The Facial Bones of the Skull The Mandible

Body of the mandible: horizontal portion

Alveolar processes: support the lower teeth

Mental protuberance: attaches facial muscles

Ramus: ascending from the mandibular angle on either side

Condylar process: articulates with temporal bone at

temporomandibular joint

Coronoid process: insertion point for temporalis muscle

(closes the jaws)

Mandibular notch: separates condylar and coronoid

processes

Mental foramina:for sensory nerves of lips and chin

The Facial Bones of the Skull

Figure 7–12a The Mandible and Hyoid Bone.

The Facial Bones of the Skull

Figure 7–12b The Mandible and Hyoid Bone.

The Facial Bones of the SkullThe Hyoid Bone

Functions of the hyoid boneSupports the larynx

Attaches muscles of the larynx, pharynx, and tongue

The Facial Bones of the Skull

Figure 7–12c The Hyoid Bone.

The Orbital ComplexForms the eye sockets (orbits)

Frontal bone (roof)

Maxilla (floor)

Maxillary, lacrimal, and ethmoid bones (orbital

rim and medial wall)

Sphenoid and palatine bones

The Orbital Complex

Figure 7–13 The Orbital Complex.

The Nasal ComplexBones of the nasal cavities and paranasal

sinusesFrontal bone, sphenoid, and ethmoid

Superior wall of nasal cavities

Maxillae, lacrimal bones, ethmoid, and inferior nasal conchaeLateral walls of nasal cavities

Maxillae and nasal bonesBridge of nose

The Nasal Complex

Figure 7–14a The Nasal Complex.

The Nasal Complex

Figure 7–14b The Nasal Complex.

The Nasal ComplexParanasal Sinuses

Air-filled chambers connected to the nasal

cavities

Lighten skull bones

Provide mucous epithelium (flushes nasal cavities)

FontanellesThe Infant Skull

Grows rapidly

Is large compared to the body

Has many ossification centers

Fusion is not complete at birth

Two frontal bones

Four occipital bones

Several sphenoidal and temporal elements

FontanellesFontanelles (sometimes spelled fontanels)

Are areas of fibrous connective tissue (soft spots)

Cover unfused sutures in the infant skull Allow the skull to flex during birth

Anterior fontanelle: frontal, sagittal, and coronal sutures

Occipital fontanelle: lambdoid and sagittal sutures

Sphenoidal fontanelles: squamous and coronal sutures

Mastoid fontanelles: squamous and lambdoid sutures

Fontanelles

Figure 7–15a The Skull of an Infant.

Fontanelles

Figure 7–15b The Skull of an Infant.

The Vertebral ColumnThe spine or vertebral column

Protects the spinal cord

Supports the head and body

26 bones 24 vertebrae, the sacrum, and the coccyx

The Vertebral Column

Figure 7–16 The Vertebral Column.

The Vertebral ColumnVertebrae

The neckSeven cervical vertebrae

The upper back12 thoracic vertebrae

Each articulates with one or more pair of ribs

The lower backFive lumbar vertebrae

The Vertebral ColumnThe Sacrum and Coccyx

The fifth lumbar vertebra articulates with the

sacrum

The sacrum articulates with the coccyx

The Vertebral ColumnFour Curvatures of the Vertebral Column

Cervical curve

Thoracic curve

Lumbar curve

Sacral curve

The Vertebral ColumnThoracic and sacral curves

Are called primary curves (present during fetal

development)

Or accommodation curves (accommodate

internal organs)

Lumbar and cervical curvesAre called secondary curves (appear after

birth)

Or compensation curves (shift body weight

for upright posture)

The Vertebral Column

Figure 7–17 Abnormal Curvatures of the Spine.

The Vertebral ColumnStructure of a Vertebra

The vertebral body (centrum)Transfers weight along the spine

The vertebral archPosterior margin of vertebral foramen

The articular processesLateral projections between laminae and pedicles

The Vertebral Column

Figure 7–18a Vertebral Anatomy.

The Vertebral Column

Figure 7–18c Vertebral Anatomy.

The Vertebral ColumnStructure of a Vertebra

The vertebral archPedicles:

walls of the vertebral arch

Laminae:

roof of the vertebral arch

Spinous process:

projection where vertebral laminae fuse

Transverse process:

projection where laminae join pedicles

The Vertebral ColumnStructure of a Vertebra

The articular processes

Superior articular process

Inferior articular process:

have articular facets on articular faces

The Vertebral Column

Figure 7–18 Vertebral Anatomy.

The Vertebral ColumnVertebral Foramina

Intervertebral foramina Gaps between pedicles of adjacent vertebraeFor nerve connections to spinal cord

Vertebral canal Formed by vertebral foraminaEncloses the spinal cord

Intervertebral DiscsAre pads of fibrous cartilage Separate the vertebral bodies Absorb shocks

The Vertebral Column

Figure 7–18 Vertebral Anatomy.

Vertebral RegionsVertebral Regions

Vertebrae are numbered

By region, from top (superior) to bottom(inferior)

C1 articulates with skull, L5 with sacrum

Vertebrae of each region

Have characteristics determined by functions

Vertebral RegionsRegions of the Vertebral Column

Cervical (C)

Thoracic (T)

Lumbar (L)

Sacral (S)

Coccygeal (Co)

Vertebral RegionsThe Cervical Vertebrae

Small body (support only head)Large vertebral foramen (largest part of spinal

cord)Concave superior surfaceSlopes posterior to anteriorC1 (atlas) has no spinous process

All others have short spinous processestip of each spinous process is notched (bifid)

Vertebral Regions

Figure 7–19 The Cervical Vertebrae.

Vertebral RegionsThe Cervical Vertebrae

Transverse processestransverse foramina (protect arteries and veins)

Atlas (C1)Articulates with occipital condyles of skullHas no body or spinous process

Axis (C2)Supports the atlasHas heavy spinous processTo attach muscles of head and neck

Vertebral Regions

Figure 7–19 The Cervical Vertebrae.

Vertebral Regions

Figure 7–19 The Cervical Vertebrae.

Vertebral Regions

Thoracic vertebrae (T1–T12)

Have heart-shaped bodies

Larger bodies than in C1–C7

Smaller vertebral foramen than in C1–C7

Long, slender spinous processes

Articulate with ribs

Vertebral Regions

Figure 7–20a The Thoracic Vertebrae.

Vertebral Regions

Figure 7–20b The Thoracic Vertebrae.

Vertebral Regions

Figure 7–20c The Thoracic Vertebrae.

Vertebral RegionsLumbar vertebrae (L1–L5)

Largest vertebraeOval-shaped bodiesThicker bodies than T1–T12

Triangular vertebral foramenSpinous process:

Short, heavy For attachment of lower back muscles

Vertebral Regions

Figure 7–21a The Lumbar Vertebrae.

Vertebral Regions

Figure 7–21b The Lumbar Vertebrae.

Vertebral Regions

Figure 7–21c The Lumbar Vertebrae.

Vertebral RegionsThe sacrum

Is curved, more in males than in females

Protects reproductive, urinary, and digestive

organs

The adult sacrumConsists of five fused sacral vertebrae

Fuses between puberty and ages 25–30

Leaving transverse lines

Sacral foramina - holes for nerves

Auricular Surface - articular surface for sacroiliac joint

Vertebral RegionsThe coccyx

Attaches ligaments and a constricting muscle of the anus

Mature coccyxConsists of three to five fused coccygeal vertebrae

Vertebral Regions

Figure 7–22 The Sacrum and Coccyx.

The Thoracic CageThe skeleton of the chest

Supports the thoracic cavityConsists of:

thoracic vertebrae

ribs

sternum (breastbone)

The Rib CageFormed of ribs and sternum

The Thoracic Cage

Figure 7–23a The Thoracic Cage.

The Thoracic Cage

Figure 7–23b The Thoracic Cage.

The Thoracic CageRibs 1–7 (true ribs)

Vertebrosternal ribsConnected to the sternum by costal cartilages

Ribs 8–12 (false ribs) Do not attach directly to the sternumVertebrochondral ribs (ribs 8–10)

Fuse together Merge with cartilage before reaching the sternum

Floating or vertebral ribs (ribs 11–12)Connect only to the vertebrae and back musclesHave no connection with the sternum

The Thoracic CageStructures of the Ribs

The head (capitulum)

At the vertebral end of the rib

The neck

The short area between the head and the tubercle

The tubercle (tuberculum)

The body (shaft)

The Thoracic Cage

Figure 7–24a The Ribs.

The Thoracic Cage

Figure 7–24b The Ribs.

The Thoracic CageThe sternum

A flat bone

In the midline of the thoracic wall

Three parts of the sternumThe manubrium

The sternal body

The xiphoid process

The Thoracic CageManubrium

The superior portion of sternum

Broad, triangular shape

Articulates with clavicles (collarbones)

Articulates with cartilages of first rib pair

Has a jugular notch, a shallow indentation

between clavicular articulations

The Thoracic CageThe sternal body

Is tongue-shaped

Attaches to the manubrium

Attaches to costal cartilages of ribs 2–7

The xiphoid processIs the smallest part of the sternum

Attaches to the sternal body

Attaches to diaphragm and rectus abdominis

muscles

The Thoracic Cage

Figure 7–23 The Thoracic Cage.