Bones, Part 1: the Axial Skeleton

PowerPoint® Lecture Slides The Skeleton prepared by Leslie Hendon University of Alabama, Birmingham • Consists of: • Bones, cartilage, joints, and ligaments Composed of 206 named bones grouped into C H A P T E R • 7 two divisions Part 1 • Axial skeleton (80 bones) Bones, Part 1: • Appendicular skeleton (126 bones) The Axial Skeleton

The Axial Skeleton(in green) The Axial Skeleton Cranium Skull Cranium Facial bones Bones of Clavicle pectoral Clavicle girdle • Formed from 80 Thoracic cage Scapula (ribs and Scapula Sternum sternum) Upper named bones Rib limb Humerus Rib Humerus Vertebra • Consists of skull, Vertebral Vertebra column Radius Ulna Radius Ulna vertebral column, Sacrum Carpals Bones of and bony thorax pelvic girdle Carpals Phalanges Phalanges Metacarpals Metacarpals Femur Patella Femur Lower Tibia limb Tibia Fibula Fibula

The Skull The Cranium • Formed by cranial and facial bones • Is the body’s most complex bony structure Frontal bone Parietal bone Glabella • Formed by cranial and facial bones Squamous part Frontonasal suture of frontal bone Supraorbital foramen Nasal bone (notch) • The cranium Sphenoid bone Supraorbital margin (greater wing) Superior orbital fissure • Encloses and protects brain Temporal bone Optic canal Ethmoid bone Inferior orbital fissure Lacrimal bone • Provides attachment for head and neck Zygomatic bone Middle nasal concha muscles Infraorbital foramen Ethmoid Perpendicular plate bone Maxilla Inferior nasal concha Vomer Mandible

1 The Face The Cranium Bones of cranium (cranial vault)

• Facial bones serve to Coronal • Form framework of the face suture

• Form cavities for the sense organs of sight, Squamous taste, and smell suture • Provide openings for the passage of air and food • Hold the teeth in place Lambdoid Facial • Anchor muscles of the face suture bones

(a) Cranial and facial divisions of the skull

Overview of Skull Geography Overview of Skull Geography

• Facial bones form anterior aspect • The skull contains smaller cavities • Cranium is divided into cranial vault and the • Middle and inner ear cavities—in lateral base aspect of cranial base • Internally, prominent bony ridges divide skull • Nasal cavity—lies in and posterior to the into distinct fossae nose

Temporal lobe Frontal lobe Anterior cranial of cerebrum of cerebrum Orbits—house the eyeballs fossa • Cerebellum • Air-filled sinuses—occur in several bones Middle cranial fossa around the nasal cavity

Posterior cranial Posterior fossa Cranial Middle fossae Anterior

(b) Superior view of the cranial fossae (c) Lateral view of cranial fossae showing the contained brain regions Copyright © 2011 Pearson Education, Inc. Figure 7.2b, c Copyright © 2011 Pearson Education, Inc.

Overview of Skull Geography Cranial Bones

• The skull contains approximately 85 named • Formed from eight large bones openings • Paired bones include • Foramina, canals, and fissures • Temporal bones • Provide openings for important structures • Parietal bones • Spinal cord • Unpaired bones include • Blood vessels serving the brain • Frontal bone • 12 pairs of cranial nerves • Occipital bone • Sphenoid bone • Ethmoid bone

2 Parietal Bones and Sutures Parietal Bones and Sutures

• Parietal bones form superior and lateral parts • Four sutures of the cranium (continued) of skull • Sagittal suture—occurs where right and left • Four sutures of the cranium parietal bones meet superiorly • Coronal suture—runs in the coronal plane • Lambdoid suture—occurs where the parietal • Located where parietal bones meet the bones meet the occipital bone posteriorly frontal bone • Squamous suture—occurs where each parietal bone meets a temporal bone inferiorly

Sutural Bones The Skull— Posterior View Sagittal suture

• Small bones that occur within sutures • Irregular in shape, size, and location Parietal bone • Not all people have sutural bones Sutural bone Lambdoid suture Occipital bone

Superior nuchal line

External occipital protuberance

Inferior nuchal line

Inferior Aspect of the Skull Lateral Aspect of the Skull Maxilla Incisive fossa (palatine process) Intermaxillary suture Hard Median palatine suture Frontal bone palate Palatine bone (horizontal plate) Infraorbital foramen Coronal suture Sphenoid bone Maxilla (greater wing) Zygomatic bone Sphenoid bone Parietal bone Ethmoid bone (greater wing) Lacrimal bone Vomer Pterygoid process Squamous suture Nasal bone Temporal bone Foramen ovale Temporal bone (zygomatic process) Foramen spinosum Lacrimal fossa Foramen lacerum Zygomatic process Zygomatic

Mandibular fossa Carotid canal bone Lambdoid suture Coronoid External acoustic meatus process Styloid process Occipital bone Stylomastoid Maxilla foramen Mastoid process External occipital Temporal bone Jugular foramen protuberance Alveolar margins (petrous part) Occipitomastoid Occipital condyle suture Mandible Basilar part of Mental foramen the occipital bone Inferior nuchal line External acoustic meatus Mandibular Occipital bone Superior nuchal line notch Mastoid process External occipital crest Mandibular Styloid Mandibular ramus Foramen magnum process External occipital condyle Mandibular angle protuberance (b) Photograph of right side of skull (a) Inferior view of the skull (mandible removed) Copyright © 2011 Pearson Education, Inc. Figure 7.7a Copyright © 2011 Pearson Education, Inc. Figure 7.4b

3 The Temporal Bone The Sphenoid Bone

Optic Lesser wing canal External acoustic Squamous meatus region Mastoid region Greater Foramen rotundum wing Foramen ovale Sella Foramen spinosum turcica Body of sphenoid

Zygomatic process Mandibular Mastoid process fossa

The Sphenoid Bone The Ethmoid Bone

Body of sphenoid Lesser wing

Superior orbital fissure Crista galli Greater Cribriform wing Olfactory plate Pterygoid foramina process

Orbital plate Left lateral mass Ethmoidal air cells Perpendicular Middle (b) Posterior view plate nasal concha Copyright © 2011 Pearson Education, Inc. Figure 7.10b Copyright © 2011 Pearson Education, Inc. Figure 7.12

Facial Bones Facial Bones

Frontal bone Parietal bone Glabella • Unpaired bones Squamous part Frontonasal suture of frontal bone Supraorbital foramen • Mandible and vomer Nasal bone (notch) Sphenoid bone Supraorbital margin (greater wing) • Paired bones Superior orbital fissure Temporal bone Optic canal Ethmoid bone • Maxillae Inferior orbital fissure Lacrimal bone Zygomatic bone • Zygomatic bones Middle nasal concha Infraorbital foramen Ethmoid Perpendicular plate bone • Nasal bones Maxilla Inferior nasal concha Lacrimal bones Vomer • Mandible • Palatine bones Mental • Inferior nasal conchae foramen Mental protuberance (a) Anterior view of skull Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 7.6a

4 Mandible Maxillary Bones Mandibular fossa Temporomandibular of temporal bone joint Coronoid Mandibular notch process Mandibular Articulates with condyle frontal bone Mandibular foramen Frontal process Orbital surface

Zygomatic Infraorbital Alveolar process foramen Ramus margin (cut) Anterior nasal of Mental spine mandible foramen Alveolar margin Mandibular angle Body of mandible (b) Maxilla, right lateral view (a) Mandible, right lateral view

Maxillary Bones Other Bones of the Face Maxilla Incisive fossa (palatine process) Intermaxillary suture Hard Median palatine suture palate Palatine bone (horizontal plate) Infraorbital foramen Maxilla • Zygomatic bones Zygomatic bone Sphenoid bone (greater wing) • Form lateral wall of orbits Vomer Pterygoid process Temporal bone Foramen ovale • Nasal bones (zygomatic process) Foramen spinosum Foramen lacerum • Form bridge of nose Mandibular fossa Carotid canal External acoustic meatus Styloid process Lacrimal bones Stylomastoid • Mastoid process foramen Temporal bone Jugular foramen • Located in the medial orbital walls (petrous part) Occipital condyle Basilar part of • Palatine bones the occipital bone Inferior nuchal line Occipital bone Superior nuchal line • Complete the posterior part of the hard palate External occipital crest External occipital Foramen magnum protuberance (a) Inferior view of the skull (mandible removed) Copyright © 2011 Pearson Education, Inc. Figure 7.7a Copyright © 2011 Pearson Education, Inc.

Other Bones of the Face Special Parts of the Skull

• Vomer • Orbits • Forms the inferior part of the nasal septum • Nasal cavity • Inferior nasal conchae • Paranasal sinuses • Thin, curved bones that project medially form • Hyoid bone the lateral walls of the nasal cavity

5 Nasal Cavity Nasal Septum Frontal sinus Crista galli Superior, middle, and Superior Ethmoid inferior meatus Cribriform Frontal sinus nasal concha bone Ethmoid plate Middle bone nasal concha Inferior nasal concha Nasal bone Sella turcica Nasal bone

Perpendicular Sphenoid sinus plate of ethmoid bone Anterior nasal spine Septal Maxillary bone cartilage Sphenoid (palatine process) sinus Sphenoid Vomer bone Pterygoid process Palatine bone Palatine bone Hard Alveolar margin (perpendicular Palatine bone Palatine process (horizontal plate) plate) palate of maxilla of maxilla (a) Bones forming the left lateral wall of the nasal cavity (b) Nasal cavity with septum in place showing the contributions of the (nasal septum removed) ethmoid bone, the vomer, and septal cartilage Copyright © 2011 Pearson Education, Inc. Figure 7.14a Copyright © 2011 Pearson Education, Inc. Figure 7.14b

Paranasal Sinuses Paranasal Sinuses

Frontal sinus Ethmoidal air cells (sinus) • Air-filled sinuses are located within Sphenoid sinus Maxillary • Frontal bone sinus • Ethmoid bone Sphenoid bone • (a) Anterior aspect • Maxillary bones Frontal sinus Ethmoidal • Lined with mucous membrane air cells

Sphenoid • Lighten the skull sinus Maxillary sinus

(b) Medial aspect

Orbits The Hyoid Bone

Superior Supraorbital notch Optic canal • Lies inferior to the Roof of orbit orbital fissure Lesser wing of mandible sphenoid bone Medial wall Orbital plate of Sphenoid body frontal bone • The only bone Lateral wall of orbit Orbital plate of ethmoid bone Zygomatic process with no direct of frontal bone Frontal process Greater wing of of maxilla articulation with Lacrimal bone sphenoid bone Greater horn Orbital surface of Nasal bone any other bone zygomatic bone Floor of orbit Lesser horn Inferior orbital fissure Orbital process of • Acts as a Infraorbital groove palatine bone Body Zygomatic bone Orbital surface of movable base for (b) Contribution of each of the seven maxillary bone bones forming the right orbit Infraorbital foramen Zygomatic bone the tongue

6 The Vertebral Column The Vertebral Column

• Formed from 26 bones in the adult • Serves as attachment sites for muscles of the • Transmits weight of trunk to the lower limbs neck and back • Surrounds and protects the spinal cord • Held in place by ligaments • Anterior and posterior longitudinal ligaments • Ligamentum flavum

The Vertebral Column Regions and Normal Curvatures

C1 2 Cervical curvature 3 (concave) 4 7 vertebrae, C – C 5 1 7 6 7 • The Vertebral column has five major regions Spinous T1 2 process 3 Transverse • 7 cervical vertebrae of the neck region 4 processes 5 Thoracic 12 thoracic vertebrae curvature • 6 (convex) 7 12 vertebrae, 8 T1 – T12 • 5 lumbar vertebrae 9 Intervertebral 10 discs • Sacrum—five fused bones 11 Intervertebral 12 foramen • Inferior to lumbar vertebrae L 1 2 Lumbar curvature • Coccyx—inferior to sacrum 3 (concave) 4 5 vertebrae, L1 – L5 5 Sacral curvature (convex) 5 fused vertebrae sacrum Coccyx Anterior view 4 fused vertebrae Right lateral view Copyright © 2011 Pearson Education, Inc. Figure 7.18 Copyright © 2011 Pearson Education, Inc.

Regions and Normal Curvatures Regions and Normal Curvatures

• Curvatures of the spine • Curvatures increase resilience of spine • Cervical and lumbar curvatures • Thoracic and sacral curvatures • Concave posteriorly • Primary curvatures • Thoracic and sacral curvatures • Present at birth • Convex posteriority • Lumbar curvature • Develops when baby begins to walk

7 Ligaments of the Spine Ligaments of the Spine

Intervertebral Supraspinous ligament disc Transverse process Anterior • Major supporting ligaments longitudinal ligament Sectioned spinous process • Anterior longitudinal ligament Intervertebral foramen Ligamentum flavum Posterior longitudinal ligament Interspinous Anulus fibrosus • Attaches to bony vertebrae and ligament Nucleus pulposus intervertebral discs Inferior articular process Sectioned body of vertebra Posterior longitudinal (a) Median section of three vertebrae, illustrating the composition ligament • Prevents hyperextension of the discs and the ligaments

Anterior longitudinal • Posterior longitudinal ligament ligament • Narrow and relatively weak • Attaches to intervertebral discs Body of a vertebra Intervertebral disc

(b) Anterior view of part of the spinal column

Ligaments of the Spine Intervertebral Discs

• Are cushion-like pads between vertebrae Vertebral spinous process (posterior aspect of vertebra) • Composed of Spinal cord Spinal nerve root Nucleus pulposus of intact disc • Nucleus pulposus

Transverse • Anulus fibrosus process Herniated portion of disc

Anulus fibrosus of disc Nucleus pulposus Herniated nucleus of disc pulposus

(c) Superior view of a herniated intervertebral disc (d) MRI of lumbar region of vertebral column in sagittal section showing normal and herniated discs

Intervertebral Discs General Structure of Vertebrae Posterior Lamina Vertebral arch Spinous Transverse process • Nucleus pulposus process • Gelatinous inner sphere • Absorbs compressive stresses Superior • Anulus fibrosus articular process Outer fings formed of ligament and • facet

• Inner rings formed of fibrocartilage Pedicle Vertebral • Contain the nucleus pulposus foramen Body (centrum) Anterior

PLAY Spine (horizontal)

8 General Structure of Vertebrae Regions Vertebral Characteristics

• Common structures to all regions • Specific regions of the spine perform specific • Body functions • Vertebral arch • Types of movement that occur between • Vertebral foramen vertebrae • Spinous process • Flexion and extension • Transverse process • Lateral flexion • Superior and inferior articular processes • Rotation in the long axis • Intervertebral foramina

Cervical Vertebrae 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 The Atlas Dens of axis Transverse ligament of atlas • C1 is termed the atlas C (atlas) 1 • Lacks a body and spinous process C2 (axis)

C3 • Supports the skull Inferior articular • Superior articular facets receive the occipital process condyles Bifid spinous process • Allows flexion and extension of neck Transverse processes • Nodding the head “yes”

C7 (vertebra prominens)

9 The Atlas The Atlas

C 1 Posterior C1 Posterior Posterior tubercle Posterior Posterior tubercle arch Inferior Posterior arch Lateral Transverse articular Lateral masses process facet Transverse masses foramen

Superior articular Anterior facet Transverse foramen Anterior arch arch Anterior tubercle Facet for dens Anterior tubercle (a) Superior view of atlas (C1) (b) Inferior view of atlas (C1)

The Axis The Axis

C Posterior • Has a body and spinous process 2 Spinous process • Dens (odontoid process) projects superiorly Inferior Lamina • Formed from fusion of the body of the atlas articular process with the axis Pedicle • Acts as a pivot for rotation of the atlas and skull Superior articular • Participates in rotating the head from side to Transverse facet side process Dens Body

Thoracic Vertebrae (T1—T12) Thoracic Vertebrae

• 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

10 Thoracic Vertebrae Lumbar Vertebrae (L1—L5)

• Spinous processes are long and point • Bodies are thick and robust inferiorly • Transverse processes are thin and tapered • Vertebral foramen are circular • Spinous processes are thick, blunt, and point • Transverse processes articulate with posteriorly tubercles of ribs • Vertebral foramina are triangular • Superior articular facets point posteriorly • Superior and inferior articular facets directly • Inferior articular processes point anteriorly medially • Allows rotation and prevents flexion and • Allows flexion and extension—rotation extension prevented

Lumbar Vertebrae Lumbar Vertebrae

Superior articular process

Transverse Body process Intervertebral disc

Inferior articular process Spinous process

Sacrum (S1—S5) Sacrum

• Shapes the posterior wall of pelvis • Sacral foramina • Formed from 5 fused vertebrae • Ventral foramina

• Superior surface articulates with L5 • Passage for ventral rami of sacral spinal • Inferiorly articulates with coccyx nerves • Sacral promontory • Dorsal foramina • Where the first sacral vertebrae bulges into • Passage for dorsal rami of sacral spinal pelvic cavity nerves • Center of gravity is 1 cm posterior to sacral promontory • Ala—develops from fused rib elements

11 Sacrum Coccyx

Body Sacral promontory Sacral Facet of superior articular process • Is the “tailbone” Ala canal • Formed from 3—5 fused vertebrae Body of first Auricular surface sacral • Offers only slight support to pelvic organs vertebra

Lateral Transverse Median sacral ridges (sites sacral crest of vertebral crest Anterior fusion) Posterior sacral sacral Apex foramina foramina Sacral hiatus Coccyx Coccyx

(a) Anterior view (b) Posterior view

The Thoracic Cage The Thoracic Cage Jugular notch Clavicular notch

Manubrium • Forms the framework of the chest Sternal angle Body Sternum • Components Xiphisternal True joint ribs Xiphoid • Thoracic vertebrae—posteriorly (1–7 process • Ribs—laterally • Sternum and costal cartilage—anteriorly • Protects thoracic organs

False • Supports shoulder girdle and upper limbs ribs (8–12) • Provides attachment sites for muscles Intercostal spaces

L1 Vertebra Costal cartilage Floating ribs (11, 12) Costal margin (a) Skeleton of the thoracic cage, anterior view Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 7.24a

The Thoracic Cage Sternum

T2 Jugular notch • Formed from three sections

T3 • Manubrium—superior section T Sternal angle 4 • Articulates with medial end of clavicles • Body—bulk of sternum • Sides are notched at articulations for costal Heart cartilage of ribs 2–7

Xiphisternal • Xiphoid process—inferior end of sternum T9 joint • Ossifies around age 40

(b) Midsagittal section through the thorax, showing the relationship of surface anatomical landmarks of the thorax to the vertebral column

12 Sternum Ribs

• Anatomical landmarks • All ribs attach to vertebral column posteriorly • Jugular notch • True ribs - superior seven pairs of ribs • Central indentation at superior border of the • Attach to sternum by costal cartilage manubrium • False ribs—inferior five pairs of ribs • Sternal angle • Ribs 11–12 are known as floating ribs • A horizontal ridge where the manubrium joins the body • Xiphisternal joint • Where sternal body and xiphoid process fuse • Lies at the level of the 9th thoracic vertebra

Ribs Facets for articulation Articular facet Ribs Head Neck Shaft with vertebrae on tubercle Articular facet on tubercle of rib Spinous process

Shaft

Junction with Costal groove Costal angle costal cartilage Transverse (a) A typical rib (rib 6, right), posterior view costal facet Ligaments Transverse costal facet (for tubercle (for tubercle of rib) Superior costal facet Angle (for head of rib) of rib) of rib Body of vertebra Neck of rib Head of rib Body of Intervertebral disc Head of rib Neck of rib thoracic Tubercle of rib Superior costal facet vertebra Shaft Sternum (for head of rib)

Cross- section (c) Superior view of the articulation between a rib and a of rib Costal groove Costal cartilage thoracic vertebra (b) Vertebral and sternal articulations of a typical true rib Copyright © 2011 Pearson Education, Inc. Figure 7.25a, b Copyright © 2011 Pearson Education, Inc. Figure 7.25c

Disorders of the Axial Skeleton Disorders of the Axial Skeleton

• Cleft palate • Abnormal spinal curvatures • A common congenital disorder • Scoliosis—an abnormal lateral curvature • Right and left halves of palate fail to fuse • Kyphosis—an exaggerated thoracic medially curvature • Stenosis of the lumbar spine • Lordosis—an accentuated lumbar curvature; • Narrowing of the vertebral canal “swayback” • Can compress roots of spinal nerves

13 The Axial Skeleton Throughout Life Fontanelles

Frontal suture • Membrane bones begin to ossify in second Frontal bone month of development Anterior fontanelle • Bone tissue grows outward from ossification centers • Fontanels Ossification center • Unossified remnants of membranes Parietal bone

Posterior fontanelle Occipital bone (a) Superior view

Fontanelles The Axial Skeleton Throughout Life

• Many bones of the face and skull form by Parietal bone Frontal bone intramembranous ossification Ossification Sphenoidal center fontanelle • Endochondral bones of the skull Posterior Temporal bone • Occipital bone fontanelle (squamous portion) • Sphenoid Mastoid • Ethmoid bones fontanelle Occipital bone • Parts of the temporal bone (b) Lateral view

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