EXERCISE 9 The Axial Skeleton - Pearson
EXERCISE9The Axial SkeletonObjectives Name the three parts of the axial skeleton. Identify the bones of the axial skeleton, either by examining isolated bonesor by pointing them out on an articulated skeleton or skull, and namethe important bone markings on each. Name and describe the different types of vertebrae. Discuss the importance of intervertebral discs and spinal curvatures. Identify three abnormal spinal curvatures. List the components of the thoracic cage. Identify the bones of the fetal skull by examining an articulated skull or image. Define fontanelle, and discuss the function and fate of fontanelles. Discuss important differences between the fetal and adult skulls.Materials Intact skull and Beauchene skullX-ray images of individuals with scoliosis,lordosis, and kyphosis (if available)Articulated skeleton, articulated vertebralcolumn, removable intervertebral discsIsolated cervical, thoracic, and lumbarvertebrae, sacrum, and coccyxIsolated fetal skullFor related exercise study tools, go to theStudy Area of MasteringA&P. There youwill find: Practice Anatomy A&PFlixLab Practice quizzes, PhysioExHistology Atlas,eText, Videos,and more!Pre-Lab Quiz1. The axial skeleton can be divided into the skull, the vertebral column,and the:a. thoracic cagec. hip bonesb. femurd. humerus2. Eight bones make up the, which encloses and protects thebrain.a. craniumb. facec. skull3. How many bones of the skull are considered facial bones?4. Circle the correct underlined term. The lower jawbone, or maxilla /mandible, articulates with the temporal bones in the only freely movablejoints in the skull.5. Circle the correct underlined term. The body / spinous process of a typicalvertebra forms the rounded, central portion that faces anteriorly in thehuman vertebral column.6. The seven bones of the neck are calledvertebrae.a. cervicalb. lumbarc. spinald. thoracic7. Thevertebrae articulate with the corresponding ribs.a. cervicalb. lumbarc. spinald. thoracic8. The, commonly referred to as the breastbone, is a flatbone formed by the fusion of three bones: the manubrium, the body, andthe xiphoid process.a. coccyxb. sacrumc. sternum9. Circle True or False. The first seven pairs of ribs are called floating ribsbecause they have only indirect cartilage attachments to the sternum.10. A fontanelle:a. is found only in the fetal skullb. is a fibrous membranec. allows for compression of the skull during birthd. all of the above121
122TExercise 9he axial skeleton (the green portion of Figure 8.1 onp. 108) can be divided into three parts: the skull, the vertebral column, and the thoracic cage. This division of theskeleton forms the longitudinal axis of the body and protectsthe brain, spinal cord, heart, and lungs.The SkullThe skull is composed of two sets of bones. Those of the cranium (8 bones) enclose and protect the fragile brain tissue.The facial bones (14 bones) support the eyes and positionthem anteriorly. They also provide attachment sites for facialmuscles. All but one of the bones of the skull are joined byinterlocking fibrous joints called sutures. The mandible isattached to the rest of the skull by a freely movable joint.9read through this material, identify each bone on an intact and/or Beauchene skull (see Figure 9.10).Note: Important bone markings are listed in the tables forthe bones on which they appear, and each bone name iscolored to correspond to the bone color in the figures.Activity 1The CraniumIdentifying the Bones of the SkullThe cranium may be divided into two major areas for study—the cranial vault, or calvaria, forming the superior, lateral,and posterior walls of the skull; and the cranial base, formingThe bones of the skull (Figures 9.1–9.10, pp. 123–131)are described in Tables 9.1 and 9.2 on p. 128. As you(Text continues on page 128.)Table 9.1AThe Axial Skeleton: Cranial Bones and Important Bone MarkingsCranial boneFrontal (1)Figures 9.1, 9.3, 9.7,9.9, and 9.10Important markingsDescriptionN/AForms the forehead, superior part of the orbit, and the floor of the anteriorcranial fossa.Supraorbital marginThick margin of the eye socket that lies beneath the eyebrows.Supraorbital foramen (notch)Opening above each orbit allowing blood vessels and nerves to pass.GlabellaSmooth area between the eyes.Parietal (2)Figures 9.1, 9.3, 9.6,9.7, and 9.10N/AForm the superior and lateral aspects of the skull.Temporal (2)Figures 9.1, 9.2, 9.3,9.6, 9.7, and 9.10N/AForm the inferolateral aspects of the skull and contribute to the middle cranialfossa; each has squamous, tympanic, and petrous parts.Squamous partLocated inferior to the squamous suture. The next two markings are locatedin this part.Zygomatic processA bridgelike projection that articulates with the zygomatic bone to form thezygomatic arch.Mandibular fossaLocated on the inferior surface of the zygomatic process; receives thecondylar process of the mandible to form the temporomandibular joint.Tympanic partSurrounds the external ear opening. The next two markings are located in this part.External acoustic meatusCanal leading to the middle ear and eardrum.Styloid processNeedlelike projection that serves as an attachment point for ligaments andmuscles of the neck. (This process is often missing from demonstration skullsbecause it has broken off.)Petrous partForms a bony wedge between the sphenoid and occipital bones and contributesto the cranial base. The remaining temporal markings are located in this part.Jugular foramenLocated where the petrous part of the temporal bone joins the occipital bone. Formsan opening which the internal jugular vein and cranial nerves IX, X, and XI pass.Carotid canalOpening through which the internal carotid artery passes into the cranial cavity.Foramen lacerumAlmost completely closed by cartilage in the living person but forms a jaggedopening in dried skulls.Stylomastoid foramenTiny opening between the mastoid and styloid processes through whichcranial nerve VII leaves the cranium.Mastoid processLocated posterior to the external acoustic meatus; serves as an attachmentpoint for neck muscles.(Table continues on page 126.)
The Axial SkeletonCoronal sutureFrontal boneParietal boneSphenoid bone(greater wing)123Ethmoid boneTemporal boneLacrimal boneLacrimal maticprocessNasal boneZygomatic boneOccipitomastoidsutureExternal acousticmeatusMaxillaMastoid processStyloid processAlveolar processesCondylar processMandibleMandibular notchMental foramenMandibular ramus(a)Mandibular angleCoronal sutureParietal boneSquamoussutureCoronoid processFrontal boneSphenoid bone(greater wing)Ethmoid boneLacrimal boneTemporal boneZygomaticprocessNasal boneLambdoidsutureLacrimal fossaOccipitalboneZygomatic boneOccipitomastoidsutureCoronoid processExternal acousticmeatusMaxillaMastoid processAlveolarprocessesStyloid processMandibleCondylarprocessMandibular angleMental foramenMandibular notchMandibular ramus(b)Figure 9.1 External anatomy of the right lateral aspect of theskull. (a) Diagram. (b) Photograph.Watch videos of the Cranium and Temporal Bone Study Area Pre-Lab Videos9
124Exercise 9Maxilla(palatine process)HardpalatePalatine bone(horizontal plate)Incisive fossaIntermaxillary sutureMedian palatine sutureInfraorbital foramenMaxillaZygomatic boneTemporal bone(zygomatic process)Sphenoid bone(greater wing)Foramen ovaleForamen spinosumVomerForamen lacerumMandibularfossaStyloid processMastoid process9Temporal bone(petrous part)Basilar part of theoccipital boneCarotid canalExternal acoustic meatusStylomastoidforamenJugular foramenOccipital condyleInferior nuchal lineParietal boneExternal occipital crestSuperior nuchal lineExternal occipitalprotuberanceForamen magnumOccipital bone(a)Hard palateZygomaticarchForamen ovaleForamen lacerumMandibularfossaForamen spinosumCarotid canalStyloid processMastoidprocessJugular foramenOccipital condyleForamen magnumSuperior nuchalline(b)Figure 9.2 Inferior view of the skull, mandible removed.Watch a video of the Zygomatic Arch Study Area Pre-Lab Videos
The Axial SkeletonEthmoidboneCribriform plateCrista galliFrontal boneAnterior cranial fossaSphenoid125Cribriform foraminaLesser wingGreater wingOptic canalForamen rotundumForamen ovaleForamen lacerumHypophyseal fossaof sella turcicaForamen spinosumHypoglossal canalMiddle cranialfossaTemporal bone(petrous part)Anterior cranialfossaInternal acousticmeatusJugular foramenMiddle cranialfossaPosteriorcranial fossaParietal boneOccipital bonePosterior cranialfossaForamen magnum(a)(b)EthmoidboneCrista galliCribriform plateFrontal boneCribriform foraminaAnterior cranial fossaOptic canalSphenoidLesser wingGreater wingForamen rotundumHypophyseal fossaof sella turcicaForamen ovaleMiddle cranialfossaForamen lacerumForamen spinosumTemporal bone(petrous part)Posteriorcranial fossaJugular foramenParietal boneOccipital boneForamen magnum(c)Figure 9.3 Internal anatomy of the inferior portion of the skull.(a) Superior view of the base of the cranial cavity, calvaria removed.(b) Diagram of the cranial base showing the extent of its major fossae.(c) Photograph of superior view of the base of the cranial cavity,calvaria removed.Watch a video of the Occipital Bone Study Area Pre-Lab Videos9
126Exercise 9Table 9.1AThe Axial Skeleton: Cranial Bones and Important Bone MarkingsCranial boneImportant markingsN/AOccipital (1)Figures 9.1, 9.2, 9.3, Foramen magnumand 9.6(continued)DescriptionForms the posterior aspect and most of the base of the skull.Large opening in the base of the bone, which allows the spinal cord to joinwith the brain stem.Occipital condylesRounded projections lateral to the foramen magnum that articulate with thefirst cervical vertebra (atlas).Hypoglossal canalOpening medial and superior to the occipital condyle through which cranialnerve XII (the hypoglossal nerve) passes.External occipital protuberanceMidline prominence posterior to the foramen magnum.The number in parentheses ( ) following the bone name indicates the total number of such bones in the mSella turcicaBody of sphenoid(a) Superior viewBody of ePterygoidprocess(b) Posterior viewFigure 9.4 The sphenoid bone.Watch a video of the Sphenoid Bone Study Area Pre-Lab Videos
The Axial SkeletonTable 9.1B127The Axial Skeleton: Cranial Bones and Important Bone MarkingsCranial boneSphenoid bone (1)Figures 9.1, 9.2, 9.3,9.4, 9.7, and 9.10Important markingsDescriptionN/ABat-shaped bone that is described as the keystone bone of the cranium because itarticulates with all other cranial bones.Greater wingsProject laterally from the sphenoid body, forming parts of the middle cranial fossa andthe orbits.Pterygoid processesProject inferiorly from the greater wings; attachment site for chewing muscles(pterygoid muscles).Superior orbital fissures Slits in the orbits providing passage of cranial nerves that control eye movements(III, IV, VI, and the ophthalmic division of V).Sella turcica“Turkish saddle” located on the superior surface of the body; the seat of the saddle,called the hypophyseal fossa, holds the pituitary gland.Lesser wingsForm part of the floor of the anterior cranial fossa and part of the orbit.Optic canalsOpenings in the base of the lesser wings; cranial nerve II (optic nerve) passes throughto serve the eye.Foramen rotundumOpenings located in the medial part of the greater wing; a branch of cranial nerve V(maxillary division) passes through.Foramen ovaleOpenings located posterolateral to the foramen rotundum; a branch of cranial nerve V(mandibular division) passes through.Foramen spinosumOpenings located posterolateral to the foramen spinosum; provides passageway for themiddle meningeal artery.Crista galliOrbitalplateLeftlateralmassEthmoidalair cellsPerpendicularplateMiddlenasal conchaFigure 9.5 The ethmoid bone. Anterior view. The superior nasal conchaeare located posteriorly and are therefore not visible in the anterior view.Table 9.1CWatch a video of the Ethmoid Bone Study Area Pre-Lab VideosThe Axial Skeleton: Cranial Bones and Important Bone MarkingsCranial boneEthmoid (1)Figures 9.1, 9.3, 9.5,9.7, and 9.10Important markingsDescriptionN/AContributes to the anterior cranial fossa; forms part of the nasal septum and thenasal cavity; contributes to the medial wall of the orbit.Crista galli“Rooster’s comb”; a superior projection that attaches to the dura mater, helping tosecure the brain within the skull.Cribriform platesLocated lateral to the crista galli; form a portion of the roof of the nasal cavity andthe floor of the anterior cranial fossa.(Table continues on page 128.)9
Table 9.1CThe Axial Skeleton: Cranial Bones and Important Bone MarkingsCranial boneEthmoid (1)(continued)Important markingsDescriptionCribriform foraminaTiny holes in the cribriform plates that allow for the passage of filaments of cranialnerve I (olfactory nerve).Perpendicular plateInferior projection that forms the superior portion of the nasal septum.Lateral massesFlank the perpendicular plate on each side and are filled with sinuses calledethmoidal air cells.Orbital platesLateral surface of the lateral masses that contribute to the medial wall of the orbits.Superior and middle nasalconchaeExtend medially from the lateral masses; act as turbinates to improve airflowthrough the nasal cavity.the skull bottom. Internally, the cranial base has three distinctdepressions: the anterior, middle, and posterior cranial fossae (see Figure 9.3). The brain sits in these fossae, completelyenclosed by the cranial vault. Overall, the brain occupies thecranial cavity.Figure 9.6 Posteriorview of the skull.Sagittal sutureParietal boneSuturalboneMajor Sutures9(continued)The four largest sutures are located where the parietal bonesarticulate with each other and where the parietal bones articulate with other cranial bones:r Sagittal suture: Occurs where the left and right parietalbones meet superiorly in the midline of the cranium (Figure 9.6).r Coronal suture: Running in the frontal plane, occursanteriorly where the parietal bones meet the frontal bone(Figure 9.1).r Squamous suture: Occurs where each parietal bonemeets the temporal bone, on each lateral aspect of the skull(Figure 9.1).r Lambdoid suture: Occurs where the parietal bones meetthe occipital bone posteriorly (Figure OccipitalcondyleInferiornuchallineFacial BonesOf the 14 bones composing the face, 12 are paired. Only themandible and vomer are single bones. An additional bone,Table 9.2the hyoid bone, although not a facial bone, is considered herebecause of its location.The Axial Skeleton: Facial Bones and Important Bone Markings (Figures 9.1, 9.7, 9.9, and 9.10,with additional figures listed for specific bones)Facial boneImportant markingsDescriptionNasal (2)N/ASmall rectangular bones forming the bridge of the nose.Lacrimal (2)N/AEach forms part of the medial orbit in between the maxilla and ethmoid bone.Lacrimal fossaHouses the lacrimal sac, which helps to drain tears from the nasal cavity.Zygomatic (2)(also Figure 9.2)N/ACommonly called the cheekbones; each forms part of the lateral orbitInferior nasal concha (2)N/AInferior turbinate; each forms part of the lateral walls of the nasal cavities;improves the airflow through the nasal cavityPalatine (2)(also Figure 9.2)N/AForms the posterior hard palate, a small part of the nasal cavity, and part of theorbit.Horizontal plateForms the posterior portion of the hard palate.Median palatine sutureMedian fusion point of the horizontal plates of the palatine bones.Vomer (1)N/AThin, blade-shaped bone that forms the inferior nasal septum.Maxilla (2)(also Figures 9.2 and 9.8)N/AKeystone facial bones because they articulate with all other facial bones except themandible; form the upper jaw and parts of the hard palate, orbits, and nasal cavity.Frontal processForms part of the lateral aspect of the bridge of the nose.Infraorbital foramenOpening under the orbit that forms a passageway for the infraorbital artery and nerve.
The Axial SkeletonTable 9.2129(continued)Facial boneMaxilla (2) (continued)Mandible (1)(also Figures 9.2 and 9.8)Important markingsDescriptionPalatine processForms the anterior hard palate; meet anteriorly in the intermaxillary suture(Note: Seen in inferior view).Zygomatic processArticulation process for zygomatic bone.Alveolar processInferior margin of the maxilla; contains sockets in which the teeth lieN/AThe lower jawbone, which articulates with the temporal bone to form the onlyfreely movable joints in the skull (the temporomandibular joint).Condylar processesArticulate with the mandibular fossae of the temporal bones.Coronoid processes“Crown-shaped” portion of the ramus for muscle attachment.Mandibular notchesSeparate the condylar process and the coronoid process.BodyHorizontal portion that forms the chin.RamusVertical extension of the body.Mandibular anglesPosterior points where the ramus meets the body.Mental foraminaPaired openings on the body (lateral to the midline); transmit blood vessels andnerves to the lower lip and skin of the chin.Alveolar processSuperior margin of the mandible; contains sockets in which the teeth lie.Mandibular foraminaLocated on the medial surface of each ramus; passageway for the nerveinvolved in tooth sensation. (Dentists inject anesthetic into this foramen beforeworking on the lower teeth.)Frontal boneParietal boneGlabellaFrontonasal sutureSquamous partof frontal boneSupraorbital foramen(notch)Nasal boneSupraorbital marginSphenoid bone(greater wing)Superior orbitalfissureTemporal boneOptic canalEthmoid boneInferior orbitalfissureLacrimal boneZygomatic boneMiddle nasal conchaPerpendicular plateInfraorbital foramenMaxillaEthmoidboneInferior nasal sFigure 9.7 Anterior view of the skull.Watch a video of the Facial Bones Study Area Pre-Lab Videos9
130Exercise 9TemporomandibularjointArticulateswith frontalboneFrontalprocessOrbital surface9Mandibular fossaof temporal boneCoronoidprocessMandibular notchCondylarprocessMandibular ofmandibleMentalforamenMandibularangle(b) Mandible, right lateral view(a) Maxilla, right lateral viewFigure 9.8 Detailed anatomy of the maxilla and mandible.Roof of orbitBody of mandibleSupraorbital notchWatch videos of the Maxilla and Mandible Study Area Pre-Lab VideosSuperiororbital fissureOptic canal! Lesser wing ofsphenoid bone! Orbital plate offrontal boneMedial wall! Sphenoid bodyLateral wall of orbit! Orbital plateof ethmoid bone! Zygomatic processof frontal bone! Frontal processof maxilla! Greater wing ofsphenoid bone! Lacrimal bone! Orbital surface ofzygomatic boneNasal boneInferior orbital fissureFloor of orbitInfraorbital groove! Orbital process ofpalatine boneZygomatic bone! Orbital surface ofmaxillary boneInfraorbitalforamenFigure 9.9 Bones that form the orbit. Seven skull bones form the orbit, the bonycavity that surrounds the eye. They are frontal, sphenoid, ethmoid, lacrimal, maxilla,palatine, and zygomatic.! Zygomatic bone
The Axial Skeleton131Parietal boneFrontal boneSphenoid boneEthmoid boneNasal bonesTemporal boneZygomatic bone9MaxillaMandibleFigure 9.10 Frontal viewof the Beauchene skull.Group ChallengeOdd Bone OutEach of the following sets contains four bones. One of thelisted bones does not share a characteristic that the otherthree do. Work in groups of three, and discuss the characteristics of the bones in each group. On a separate pieceof paper, one student will record the characteristics of eachbone. For each set of bones, discuss the possible candidatesfor the “odd bone out” and which characteristic it lacks, basedon your notes. Once your group has
Lab PhysioEx A&PFlix Practice quizzes, Histology Atlas, eText, Videos, and more! Pre-Lab Quiz 1. The axial skeleton can be divided into the skull, the vertebral column, and the: a. thoracic cage c. hip bones b. femur d. humerus 2. Eight bones make up the , which encloses and protects the brain. a. cranium b. face c. skull 3.
The appendicular skeleton refers to the parts of the skeleton that are attached to the axial skeleton. It includes the pectoral girdle, the pelvic girdle, and the bones of the arms and legs The Axial Skeleton The axial skeleton is the main, longitudinal part of the skeleton. It consis
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EXERCISE 10 - THE SKELETON When studying the skeletal system, the bones are often sorted into two broad categories: the axial skeleton and the appendicular skeleton. This lab focuses on the axial skeleton, which consists of the bones that form the axis of the body. The axial skeleton includes bones in the skull, vertebrae, and thoracic cage, as .
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Patella Areas of the skeleton Area of the skeleton Bones Axial Skeleton Is the main core or axis of the skeleton: Cranium Sternum Ribs Vertebral Column Appendicular Skeleton Contains bones that are attached to the axial skeleton Limps Shoulder girdle (
