Anatomia Joints

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C H A P T E R

7Anatomy of

Bones and Joints

LearningOutcomesAFTER YOU COMPLETE THIS CHAPTER YOU SHOULD BE ABLE TO:

7.1 General Considerations of Bones 1501. Dene the general anatomical terms for various bone features and

explain the functional signicance of each.

7.2 Axial Skeleton 150

2. List the bones of the braincase and of the face. 3. Describe the locations and functions of the auditory ossicles and

the hyoid bone. 4. Describe the major features of the skull as seen from different

views. 5. Describe the structures and functions of the vertebral column and

individual vertebrae. 6. List the features that characterize different types of vertebrae. 7. Describe the thoracic cage and give the number of true, false, and

floating ribs.

7.3 Appendicular Skeleton 167 8. Describe the bones of the pectoral girdle and upper limb. 9. Describe the bones of the pelvic girdle and lower limb.

7.4 Joints 17710. Dene the term articulationand explain how joints are named

and classied.11. List the general features of a brous joint, describe the three classes

of brous joints, and give examples of each class.12. List the general features of a cartilaginous joint, describe the two

types of cartilaginous joints, and give examples of each class.13. Describe the general features of a synovial joint.14. Dene a bursa and a tendon sheath.15. Describe and give examples of the types of synovial joints.

7.5 Types of Movement 18316. Dene and be able to demonstrate the movements occurring at the

joints of the body.

7.6 Description of Selected Joints 18617. Describe the temporomandibular, shoulder, elbow, hip, knee, and

ankle joints and the foot arches.

7.7 Effects of Aging on the Joints 19118. Discuss the age-related changes that occur in joints.

Photo: Brittle bone disease (see osteogenesis imperfecta, p. 128) is

a genetic disorder that causes an increased risk for broken bones.

Even very young babies, like the one in this photo, can suffer a

greater incidence of bone trauma with even minor falls or bumps.

Knowing someone with brittle bone disease allows us to be more

appreciative of a healthy skeletal system.

Module 5: Skeletal System


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150 Chapter 7150

Introduction

If the body had no skeleton, it would look somewhat like apoorly stuffed rag doll. Without a skeletal system, we wouldhave no framework to help maintain shape and we would

not be able to move normally. Bones of the skeletal system sur-round and protect organs, such as the brain and heart. Humanbones are very strong and can resist tremendous bending andcompression forces without breaking. Nonetheless, each yearnearly 2 million Americans break a bone. Muscles pull on bones to make them move, but movement

would not be possible without joints between the bones. Humanswould resemble statues, were it not for the joints between bonesthat allow bones to move once the muscles have provided the

pull. Machine parts most likely to wear out are those that rubtogether, and they require the most maintenance. Movable jointsare places in the body where the bones rub together, yet we tendto pay little attention to them. Fortunately, our joints are self-maintaining, but damage to or disease of a joint can make move-ment very diffi cult. We realize then how important the movable

joints are for normal function. Te skeletal system includes the bones, cartilage, ligaments,and tendons. o study skeletal gross anatomy, however, dried,prepared bones are used. Tis allows the major features of indi-

vidual bones to be seen clearly without being obstructed by asso-ciated soft tissues, such as muscles, tendons, ligaments, cartilage,nerves, and blood vessels. Te important relationships amongbones and soft tissues should not be ignored, however.

7.1 General Considerationsof BonesTe average adult skeleton has 206 bones (figure 7.1). Although thisis the traditional number, the actual number of bones varies fromperson to person and decreases with age as some bones becomefused. Bones can be categorized as paired or unpaired. A pairedbone is two bones of the same type located on the right and leftsides of the body, whereas an unpaired bone is a bone located onthe midline of the body. For example, the bones of the upper andlower limbs are paired bones, whereas the bones of the vertebralcolumn are unpaired bones. Tere are 86 paired and 34 unpairedbones. Many of the anatomical terms used to describe the features ofbones are listed in table 7.1. Most of these features are based on therelationship between the bones and associated soft tissues. If a bonehas a tubercle (toober-kl, lump) or process (projection), suchstructures usually exist because a ligament or tendon was attached tothat tubercle or process during life. If a bone has a foramen

(f-rmen, pl.foramina,f-rami-n, a hole) in it, that foramen wasoccupied by something, such as a nerve or blood vessel. If a bone hasa condyle(kondl, knuckle), it has a smooth, rounded end, covered

with articular cartilage (see chapter 6), that is part of a joint. Te skeleton is divided into the axial and appendicular skeletons.

1 How many bones are in an average adult skeleton? What are pairedand unpaired bones?

2 How are lumps, projections, and openings in bones related to softtissues?

7.2 Axial SkeletonTe axial skeletonforms the upright axis of the body (see figure 7.1).It is divided into the skull, auditory ossicles, hyoid bone, vertebralcolumn, and thoracic cage, or rib cage. Te axial skeleton protects thebrain, the spinal cord, and the vital organs housed within the thorax.

3 List the parts of the axial skeleton and its functions.

SkullTe bones of the head form the skull,or cranium(krn-um). Te22 bones of the skull are divided into two groups: those of the brain-case and those of the face. Te braincase consists of 8 bones that

Table 7.1 General Anatomical Terms forVarious Features of Bones

Term Description

Body Main part

Head Enlarged, often rounded end

Neck Constriction between head and body

Margin or border Edge

Angle Bend

Ramus Branch off the body beyond the angle

Condyle Smooth, rounded articular surface

Facet Small, flattened articular surface

Ridges

Line or linea Low ridge

Crest or crista Prominent ridge

Spine Very high ridge

Projections

Process Prominent projection

Tubercle Small, rounded bump

Tuberosity or tuber Knob; larger than a tubercle

Trochanter Tuberosities on the proximal femur

Epicondyle Upon a condyle

Openings

Foramen Hole

Canal or meatus Tunnel

Fissure Cleft

Sinus or labyrinth Cavity

Depressions

Fossa General term for a depression

Notch Depression in the margin of a bone

Groove or sulcus Deep, narrow depression


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Ulna

Radius

Carpal bonesMetacarpalbones

Phalanges

Coxalbone

Femur

Patella

Tibia

Fibula

Tarsal bones

Metatarsal bones

Phalanges

Anterior view Posterior view

Axial Skeleton

Skull

Vertebralcolumn

Mandible

Ribs

Sacrum

Coccyx

Appendicular Skeleton

Clavicle

Scapula

Humerus

Axial Skeleton

Skull

Vertebralcolumn

Mandible

Hyoid bone

Sternum

Ribs

Sacrum

Anatomy of Bones and Joints 151

immediately surround and protect the brain. Te bones of the braincaseare the paired parietal and temporal bones and the unpaired frontal,occipital, sphenoid, and ethmoid bones. Te facial bones form thestructure of the face. Te 14 facial bones are the maxilla (2), zygomatic(2), palatine (2), lacrimal (2), nasal (2), inferior nasal concha (2),

mandible (1), and vomer (1) bones. Te frontal and ethmoid bones,which are part of the braincase, also contribute to the face. Te facialbones support the organs of vision, smell, and taste. Tey also provideattachment points for the muscles involved in mastication (mas-ti-kshun, chewing), facial expression, and eye movement. Te jaws

Figure 7.1Complete SkeletonBones of the axial skeleton are listed in the far left- and right-hand columns; bones of the appendicular skeleton are listed in the center. (The skeleton is not shown in

the anatomical position.)


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Superior view

Frontal bone

Inferior temporal line

Superior temporal line

Occipital bone

Coronal suture

Sagittal suture

Lambdoid suture

Parietal bone

152 Chapter 7

(mandible and maxillae) hold the teeth (see chapter 21) and the tem-poral bones hold the auditory ossicles,or ear bones (see chapter 14). Te bones of the skull, except for the mandible, are not easilyseparated from each other. It is convenient to think of the skull, exceptfor the mandible, as a single unit. Te top of the skull is called the

calvaria(kal-vr-), or skullcap. It is usually cut off to reveal the skullsinterior. Selected features of the intact skull are listed in table 7.2.

4 Name the bones of the braincase and the facial bones. Whatfunctions are accomplished by each group of bones?

Superior View of the Skull

Te skull appears quite simple when viewed from above (figure 7.2).Te paired parietal bonesare joined at the midline by the sagittal

suture,and the parietal bones are connected to the frontal bonebythe coronal suture.

Predict 1

Explain the basis for the names sagittaland coronal sutures.

Posterior View of the Skull

Te parietal bones are joined to the occipital boneby the lambdoid(lamdoyd, the shape resembles the Greek letter lambda) suture(figure 7.3). Occasionally, extra small bones called sutural(soochoor-l), or wormian, bonesform along the lambdoid suture.

Figure 7.2 Superior View of the SkullThe names of the bones are in bold.

Table 7.2 Processes and Other Features of the Skull

Bone on WhichFeature Feature Is Found Description

External Features

Alveolar process Mandible, maxilla Ridges on the mandible and maxilla containing the teeth

Coronoid process Mandible Attachment point for the temporalis muscle

Horizontal plate Palatine The posterior third of the hard palate

Mandibular condyle Mandible Region where the mandible articulates with the temporal bone

Mandibular fossa Temporal Depression where the mandible articulates with the skull

Mastoid process Temporal Enlargement posterior to the ear; attachment site for several muscles that move the head

Nuchal lines Occipital Attachment points for several posterior neck muscles

Occipital condyle Occipital Point of articulation between the skull and the vertebral columnPalatine process Maxilla Anterior two-thirds of the hard palate

Pterygoid hamulus Sphenoid Hooked process on the inferior end of the medial pterygoid plate, around which the tendon of

one palatine muscle passes; an important dental landmark

Pterygoid plates Sphenoid Bony plates on the inferior aspect of the sphenoid bone; the lateral pterygoid plate is the site of

(medial and lateral) attachment for two muscles of mastication (chewing)

Styloid process Temporal Attachment site for three muscles (to the tongue, pharynx, and hyoid bone) and some ligaments

Temporal lines Parietal Where the temporalis muscle, which closes the jaw, attaches

Internal Features

Crista galli Ethmoid Process in the anterior part of the cranial vault to which one of the connective tissue coveringsof the brain (dura mater) connects

Petrous portion Temporal Thick, interior part of temporal bone containing the middle and inner ears and the auditory ossicles

Sella turcica Sphenoid Bony structure resembling a saddle in which the pituitary gland is located

An external occipital protuberanceis present on the posterior sur-face of the occipital bone. It can be felt through the scalp at the baseof the head and varies considerably in size from person to person.Te external occipital protuberance is the site of attachment of the


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Parietal bone

Occipital bone

Superior nuchal line

Temporal bone(mastoid process)

Occipitomastoid suture

Zygomatic arch

Lambdoid suture

External occipitalprotuberance

Inferior nuchal line

Occipital condyle

Mandible

Sagittal suture

Posterior view

Superior temporal line

Coronal suture

Inferior temporal line

Parietal bone

Temporal bone

Occipital bone

Squamoussuture

Lambdoid suture

Mandibular condyle

External acoustic meatus

Styloid process

Zygomatic processof temporal bone

Temporal processof zygomatic bone

Zygomatic arch

Angle of mandible

Frontal bone

Supraorbital foramen

Supraorbital margin

Sphenoid bone (greater wing)

Nasal bone

Lacrimal bone

Zygomatic bone

Maxilla

Mandible

Lateral view

Nasolacrimal canal

Infraorbital foramen

Coronoid process

of mandible

Mandibular ramusMental foramen

Alveolar processes

Mastoid process

Occipitomastoid suture

Body of mandible


ligamentum nuchae(nook, nape of neck), an elastic ligament thatextends down the neck and helps keep the head erect by pulling onthe occipital region of the skull. Nuchal lines are a set of smallridges that extend laterally from the protuberance and are the pointsof attachment for several neck muscles.

Lateral View of the Skull

Te parietal bone and the temporal bone form a large part of the side ofthe head (figure 7.4). Te term temporalmeans related to time, and thetemporal bone is so named because the hair of the temples is often thefirst to turn white, indicating the passage of time. Te squamoussuturejoins the parietal and temporal bones. A prominent feature of thetemporal bone is a large hole, the external acoustic meatus,or auditorymeatus(m-tus, passageway or tunnel), which transmits sound waves

toward the eardrum. Just posterior and inferior to the external auditorymeatus is a large inferior projection, the mastoid(mastoyd, resemblinga breast) process.Te process can be seen and felt as a prominent lump

just posterior to the ear. Te process is not solid bone but is filled withcavities called mastoid air cells,which are connected to the middle ear.Neck muscles involved in rotation of the head attach to the mastoidprocess. Te superior and inferior temporal linesarch across the lateral

Figure 7.3 Posterior View of the SkullThe names of the bones are in bold.

Figure 7.4 Right Lateral View of the SkullThe names of the bones are in bold.


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Frontal bone

Supraorbital margin

Zygomatic arch

Nasal bone

Maxilla

Zygomatic bone

Mastoid process

Angle of mandible

Mandible

Superior orbital fissure


Optic canal

Coronal suture

Inferior orbital fissure


Mental foramen

Mental protuberance

Nasal cavity

Middle nasal concha

Sphenoid bone

Frontal bone

Parietal bone

Mandible

Orbit

Temporal bone

Nasal bone

Lacrimal bone

Zygomatic bone

Perpendicular plateof ethmoid bone

Vomer

Inferior nasal concha

Maxilla

Nasalseptum

Frontal view

154 Chapter 7

Figure 7.5 Lateral View of Bony Landmarks on the FaceThe names of the bones are in bold.

surface of the parietal bone. Tey are attachment points of the tempora-lis muscle, one of the muscles of mastication. Te lateral surface of the greater wing of the sphenoid(sfnoyd, wedge-shaped) boneis anterior to the temporal bone (seefigure 7.4). Although appearing to be two bones, one on each side of

the skull, the sphenoid bone is actually a single bone that extendscompletely across the skull. Anterior to the sphenoid bone is thezygomatic(zg-matik, a bar or yoke) bone,or cheekbone, whichcan be easily seen and felt on the face (figure 7.5). Te zygomatic arch,which consists of joined processes from

the temporal and zygomatic bones, forms a bridge across the side ofthe skull (see figure 7.4). Te zygomatic arch is easily felt on the sideof the face, and the muscles on each side of the arch can be felt as the

jaws are opened and closed. Te maxilla(mak-sil), or upper jaw, is anterior to the zygomaticbone. Te mandible, or lower jaw, is inferior to the maxilla (seefigure 7.4). Te mandible consists of two main parts: the bodyand theramus(branch). Te body and ramus join at the angle of the man-dible. Te superior end of the ramus has a mandibular condyle,

which articulates with the temporal bone, allowing movement of themandible. Te coronoid(kro-noyd, shaped like a crows beak) pro-cessis the attachment site of the temporalis muscle to the mandible.Te maxillae and mandible have alveolar(al-v-lr) processeswithsockets for the attachment of the teeth.

Anterior View of the Skull

Te major bones seen from the anterior view are the frontal bone(forehead), the zygomatic bones (cheekbones), the maxillae, and themandible (figure 7.6). Te teeth, which are very prominent in this

Figure 7.6 Anterior View of the SkullThe names of the bones are in bold.


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Zygomatic bone

Maxilla

Mandible

Frontal bone

Mental

protuberance

Nasal bone

Superior orbital fissure

Sphenoidbone

Palatine bone

Zygomaticbone


Infraorbital groove


Maxilla

Opening tonasolacrimal canal

Lacrimal bone

Ethmoid bone

Posterior and anteriorethmoidal foramina

Optic canal

Frontal bone


Anterior view

Lesser wingGreater wing


Figure 7.7 Anterior View of Bony Landmarks on the FaceThe names of the bones are in bold.

Deviated Nasal Septum

The nasal septum usually is located in the median plane until a

person is 7 years old. Thereafter, it tends to deviate, or bulge slightly

to one side. The septum can also deviate abnormally at birth or, morecommonly, as a result of injury. Deviations can be severe enough to

block one side of the nasal passage and interfere with normal

breathing. The repair of severe deviations requires surgery.

largest of these are the superiorand inferior orbital fissures.Teyprovide openings through which nerves and blood vessels commu-nicate with the orbit or pass to the face. Te optic nerve, for thesense of vision, passes from the eye through the optic canal andenters the cranial cavity. Te nasolacrimal(n-z-lakri-ml, nasus,

nose+

lacrima, tear) canalpasses from the orbit into the nasal cav-ity. It contains a duct that carries tears from the eyes to the nasalcavity (see chapter 14). Te nasal cavity is divided into right and left halves by a nasalseptum(septum, wall) (see figure 7.6; figure 7.9). Te bony part ofthe nasal septum consists primarily of the vomer (vmer, shapedlike a plowshare) inferiorly and the perpendicular plateof the eth-moid (ethmoyd, sieve-shaped) bone superiorly. Te anterior partof the nasal septum is formed by hyaline cartilage called septal car-tilage(see figure 7.9a). Te external part of the nose has some bone

but is mostly hyaline cartilage (see figure 7.9b), which is absent inthe dried skeleton.

view, are discussed in chapter 24. Many bones of the face can be eas-ily felt through the skin of the face (figure 7.7). wo prominent cavities of the skull are the orbits and the nasalcavity (see figure 7.6). Te orbitsare so named because of the rota-tion of the eyes within them. Te bones of the orbits (figure 7.8)

provide protection for the eyes and attachment points for the mus-cles moving the eyes. Te major portion of each eyeball is within theorbit, and the portion of the eye visible from the outside is relativelysmall. Each orbit contains blood vessels, nerves, and fat, as well as theeyeball and the muscles that move it. Te orbit has several openings through which structures com-municate between the orbit and other cavities (see figure 7.8). Te

Figure 7.8 Bones of the Right OrbitThe names of the bones are in bold.


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Frontal bone

Frontal sinus

Nasal bone

Lateral nasal cartilage

Greater alar cartilage

Lateral incisorPalatine process of maxilla

Horizontal plate

Inferior nasal concha

Vertical plate

Medial pterygoid plate

phenoid bone

Sphenoidal sinus

Middle nasal concha

Superior nasal concha

Olfactory recess

Lacrimal bone

Maxilla

Part ofethmoid bone

Hard palate

Palatine bone

Frontal bone

Frontal sinus

Nasal bone

Perpendicular plate

f ethmoid boneSeptal cartilage

Vomer

Greater alar cartilage

nteriornasal spine

Nasalsep um

tene

ss

Central incisor

phenoid bone

phenoidal sinus

lfactory foramina

ribriform plate

rista galli

(a) Medial view

(b) Medial view

156 Chapter 7

Predict 2

A direct blow to the nose may result in a broken nose. Using gures 7.6 and

7.9, list the bones most likely to be broken.

Te lateral wall of the nasal cavity has three bony shelves, the nasalconchae (konk, resembling a conch shell) (see figure 7.9b). Teinferior nasal concha is a separate bone, and the middle and superiornasal conchae are projections from the ethmoid bone. Te conchaeand the nasal septum increase the surface area in the nasal cavity,

which promotes the moistening and warming of inhaled air and theremoval of particles from the air by overlying mucous membranes. Several of the bones associated with the nasal cavity have large,air-filled cavities within them called the paranasal sinuses, which

Figure 7.9 Bones of the Nasal CavityThe names of the bones are in bold. (a) Nasal septum as seen from the left nasal cavity. (b) Right lateral nasal wall as seen from inside the nasal cavity with the nasal

septum removed.

open into the nasal cavity (figure 7.10). Te sinuses decrease theweight of the skull and act as resonating chambers during voice pro-duction. Compare a normal voice with the voice of a person who hasa cold and whose sinuses are stopped up. Te paranasal sinuses arenamed for the bones in which they are located and include the paired

frontal, sphenoidal,and maxillary sinuses.Te ethmoidal sinusesconsist of 3 large to 18 small air-filled cavities on each side and are alsocalled ethmoid air cells. Te air cells interconnect to form the eth-moidal labyrinth.

Inferior View of the Skull

Seen from below with the mandible removed, the base of the skull iscomplex, with a number of foramina and specialized surfaces (figure 7.11and table 7.3). Te prominent foramen magnum,through which the


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Frontal sinus

Ethmoidal sinuses

Sphenoidal sinus

Maxillary sinus

Anterior palatine foramen

Zygomatic bone

Posterior palatine foramen


Lateral pterygoid plate

Medial pterygoid plate

Greater wing

Foramen ovale

Foramen spinosum

External acoustic meatus

Jugular foramen

Occipital condyle

Incisive fossa

Maxilla

Hardpalate

Palatine processof maxillary bone

Horizontal pl

ate of palatine bone

Vomer

Pterygoid hamulus

Temporal processof zygomatic bone

Zygomatic processof temporal bone

Zygomatic arch

Foramen lacerumStyloid process

Mandibular fossa

Carotid canal (posteroinferior opening)Stylomastoid foramen

Mastoid process

Temporal bone

Occipital bone

Inferior nuchal line

Superior nuchal line

Foramen magnum

External occipital protuberance

Sphenoidbone

Inferior view


spinal cord and brain are connected, is located in the occipital bone.Te occipital condyles,located next to the foramen magnum, articu-

late with the vertebral column, allowing movement of the skull. Te major entry and exit points for blood vessels that supply thebrain can be seen from this view. Blood is carried to the brain by theinternal carotid arteries, which pass through the carotid(ka-rotid,put to sleep) canals,and the vertebral arteries, which pass through

Figure 7.11 Inferior View of the SkullThe names of the bones are in bold. The mandible has

been removed.

Figure 7.10Paranasal Sinuses(a) Anterior view. (b) Lateral view.

(a) (b)

the foramen magnum. Most blood leaves the brain through theinternal jugular veins, which exit through the jugular foramina

located lateral to the occipital condyles. wo long, pointed styloid (stloyd, stylus- or pen-shaped)processesproject from the inferior surface of the temporal bone (seefigures 7.4 and 7.11). Muscles involved in movement of the tongue,hyoid bone, and pharynx attach to each process. Te mandibular


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158 Chapter 7

fossa, where the mandibular condyle articulates with the skull, isanterior to the mastoid process.

Te posterior opening of the nasal cavity is bounded on eachside by the vertical bony plates of the sphenoid bone: the medialpterygoid (teri-goyd, wing-shaped) platesand the lateral pterygoidplates.Muscles that help move the mandible attach to the lateralpterygoid plates (see chapter 9). Te vomer forms most of theposterior portion of the nasal septum. Te hard palate,or bony palate,forms the floor of the nasal cavity.Sutures join four bones to form the hard palate; the palatine processes ofthe two maxillary bones form the anterior two-thirds of the palate, and

the horizontal plates of the two palatine bones form the posterior one-third of the palate. Te tissues of the soft palate extend posteriorly fromthe hard palate. Te hard and soft palates separate the nasal cavity fromthe mouth, enabling humans to chew and breathe at the same time.

Table 7.3 Skull Foramina, Fissures, and Canals

Opening Bone Containing the Opening Structures Passing Through Openings

Carotid canal Temporal Carotid artery and carotid sympathetic nerve plexus

External acoustic meatus Temporal Sound waves en route to the eardrum

Foramen lacerum Between temporal, occipital, The foramen is lled with cartilage during life; the carotid

and sphenoid canal and pterygoid canal cross its superior part but do not

actually pass through it

Foramen magnum Occipital Spinal cord, accessory nerves, and vertebral arteries

Foramen ovale Sphenoid Mandibular division of trigeminal nerve

Foramen rotundum Sphenoid Maxillary division of trigeminal nerve

Foramen spinosum Sphenoid Middle meningeal artery

Hypoglossal canal Occipital Hypoglossal nerve

Incisive fossa Between maxillae Nasopalatine nerve

Inferior orbital ssure Between sphenoid and maxilla Infraorbital nerve and blood vessels and zygomatic nerve

Infraorbital foramen Maxilla Infraorbital nerve

Internal acoustic meatus Temporal Facial nerve and vestibulocochlear nerve

Jugular foramen Between temporal and occipital Internal jugular vein, glossopharyngeal nerve, vagus nerve, and

accessory nerve

Mandibular foramen Mandible Inferior alveolar nerve to the mandibular teeth

Mental foramen Mandible Mental nerve

Nasolacrimal canal Between lacrimal and maxilla Nasolacrimal (tear) duct

Olfactory foramina Ethmoid Olfactory nerves

Optic canal Sphenoid Optic nerve and ophthalmic artery

Stylomastoid foramen Temporal Facial nerve

Superior orbital ssures Sphenoid Oculomotor nerve, trochlear nerve, ophthalmic division of

trigeminal nerve, abducent nerve, and ophthalmic veins

Supraorbital foramen or notch Frontal Supraorbital nerve and vessels

Interior of the Cranial Cavity

Te cranial cavityis the cavity in the skull occupied by the brain.When the floor of the cranial cavity is viewed from above with thecalvaria cut away (figure 7.12), it can be divided into anterior,middle, andposterior cranial fossae,which are formed as the devel-oping skull conforms to the shape of the brain. Te crista galli(krist gl, roosters comb) of the ethmoidbone is a prominent ridge located in the center of the anteriorfossa. It is a point of attachment for one of the meninges (me-ninjz), a thick connective tissue membrane that supports andprotects the brain (see chapter 11). On each side of the crista galli

are the cribriform (kribri-frm, sievelike) platesof the ethmoidbone. Te olfactory nerves extend from the cranial cavity into theroof of the nasal cavity through sievelike perforations in the crib-riform plate called olfactory foramina(see chapter 14). Te sphenoid bone extends from one side of the skull to theother. Te center of the sphenoid bone is modified into a structureresembling a saddle, the sella turcica(sel tursi-k, urkish saddle),

which is occupied by the pituitary gland in life. Te petrous(rocky) partof the temporal bone is a thick, bony

ridge lateral to the foramen magnum. It is hollow and contains themiddle and inner ears. Te auditory ossicles are located in the middleear. An internal carotid artery enters the external opening of each carotidcanal (see figure 7.11) and passes through the carotid canal, whichruns anteromedially within the petrous part of the temporal bone.

Cleft Lip or Palate

During development, the facial bones sometimes fail to fuse with

one another. A cleft lipresults if the maxillae do not form normally, and

a cleft palateoccurs when the palatine processes of the maxillae donot fuse with one another. A cleft palate produces an opening between

the nasal and oral cavities, making it diffi cult to eat or drink or to speak

distinctly. A cleft lip and cleft palate may also occur in the same person.


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Anterior cranial fossa

Lesser wing

Greater wingSphenoidbone

Squamous portion

Petrous portion

Temporal

bone

Foramen rotundum

Carotid canal(foramen lacerum is inferior)

Middle cranial fossa

Internal acoustic meatus

Foramen magnum

Parietal bone

Frontal sinuses

Crista galli

Cribriform plate

Ethmoidbone

Frontal bone

Optic canal

Sella turcica

Foramen ovaleForamen spinosum

Jugular foramen

Hypoglossal canal

Posterior cranial fossa

Occipital bone

Olfactory foramina

Superior view


A thin plate of bone separates the carotid canal from the middle ear,making it possible for a person to hear his or her own heartbeatfor example, when frightened or after running. Most of the foramina seen in the interior view of the skull, suchas the foramen magnum and optic canals, can also be seen externally.

A few foramina, such as the internal acoustic meatus,do not opento the outside. Te vestibulocochlear nerve for hearing and balancepasses through the internal acoustic meatus and connects to the innerear within the temporal bone.

5 Name the major sutures separating the frontal, parietal, occipital, andtemporal bones.

6 Name the parts of the bones that connect the skull to the vertebralcolumn and that connect the mandible to the temporal bone.

7 Describe the bones and cartilage found in the nasal septum.

8 What is a sinus? What are the functions of sinuses? Give the location ofthe paranasal sinuses. Where else in the skull are there air-lled spaces?

9 Name the bones that form the hard palate. What is the function ofthe hard palate?

10 Through what foramen does the brainstem connect to the spinal cord?Name the foramina that contain nerves for the senses of vision (opticnerve), smell (olfactory nerves), and hearing (vestibulocochlear nerve).

11 Name the foramina through which the major blood vessels enter andexit the skull.

12 List the places where the following muscles attach to the skull: neckmuscles, throat muscles, muscles of mastication, muscles of facialexpression, and muscles that move the eyeballs.

Figure 7.12 Floor of the Cranial CavityThe names of the bones are in bold. The roof of the skull has been removed, and the floor is seen from a superior view.

Hyoid BoneTe hyoid bone (figure 7.13), which is unpaired, is often listed

among the facial bones because it has a developmental origin in com-mon with the bones of the face. It is not, however, part of the adultskull. Te hyoid bone has no direct bony attachment to the skull.Instead, muscles and ligaments attach it to the skull, so the hyoidfloats in the superior aspect of the neck just below the mandible.Te hyoid bone provides an attachment point for some tonguemuscles, and it is an attachment point for important neck musclesthat elevate the larynx during speech or swallowing.

13 Where is the hyoid bone located and what does it do?

Vertebral ColumnTe vertebral (verto, to turn) column,or backbone, is the centralaxis of the skeleton, extending from the base of the skull to slightlypast the end of the pelvis (see figure 7.1). Te vertebral column per-forms five major functions: (1) It supports the weight of the head andtrunk, (2) it protects the spinal cord, (3) it allows spinal nerves to exit

the spinal cord, (4) it provides a site for muscle attachment, and(5) it permits movement of the head and trunk. Te vertebral column usually consists of 26 individual bones,grouped into five regions (figure 7.14). Seven cervical (serv-kal,neck)vertebrae, 12 thoracic(th-rasik, chest)vertebrae,5 lumbar


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Greatercornu

Lessercornu

Body

Greatercornu

Lessercornu

Body

Anterior view

Lateral view(from the left side)

Hyoid bone

Cervicalregion(concaveposteriorly)

Thoracicregion(convex

posteriorly)

Lumbarregion(concaveposteriorly)

Sacral andcoccygealregions(convexposteriorly)

First cervical vertebra(atlas)

Second cervical vertebra(axis)

Seventh cervical vertebra

First thoracic vertebra

Intervertebral disk

Intervertebral foramina

Twelfth thoracic vertebra

First lumbar vertebra

Body

Transverse process

Spinous process

Fifth lumbar vertebra

Sacrum

Coccyx

Sacral promontory

Lateral view

160 Chapter 7

(lumbar, loin)vertebrae,1sacral(skrl, sacred) bone,and 1 coccygeal(kok-sij-l, shaped like a cuckoos bill) bonemake up the vertebralcolumn. Te cervical vertebrae are designated C, thoracic ,lumbar L, sacral S, and coccygeal CO. A number after the let-ter indicates the number of the vertebra, from superior to inferior,

within each vertebral region. Te developing embryo has 33 or 34vertebrae, but the 5 sacral vertebrae fuse to form 1 bone, and the 4or 5 coccygeal bones usually fuse to form 1 bone. Te five regions of the adult vertebral column have four majorcurvatures (see figure 7.14). Te primary thoracic and sacral curvesappear during embryonic development and reflect the C-shapedcurve of the embryo and fetus within the uterus. When the infantraises its head in the first few months after birth, a secondary curve,

which is concave posteriorly, develops in the neck. Later, when theinfant learns to sit and then walk, the lumbar portion of the columnalso becomes concave posteriorly.

Figure 7.13Hyoid Bone

Figure 7.14 Complete Vertebral Column Viewed from theLeft Side

Viewed from the back, the vertebral column has four curvatures. The cervical

and lumbar curvatures are concave posteriorly (curve in) and the thoracic and

sacral curvatures are convex posteriorly (curve out).

Abnormal Spinal Curvatures

Lordosis (lordosis, hollow back) is an exaggeration of the con-

cave curve of the lumbar region, resulting in a swayback condition.

Kyphosis (k -fosis, hump back) is an exaggeration of the convex

curve of the thoracic region, resulting in a hunchback condition.Scoliosis(skole-osis) is an abnormal lateral and rotational curvature

of the vertebral column, which is often accompanied by secondary

abnormal curvatures, such as kyphosis.

14 What are the functions of the vertebral column?

15 Name and give the number of the bones forming the vertebral column.

16 Describe the four major curvatures of the vertebral column and howthey develop.


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General Plan of the Vertebrae

Each vertebra consists of a body, an arch, and various processes. Teweight-bearing portion of the vertebra is the body(table 7.4a). Tevertebral arch projects posteriorly from the body. Each vertebralarch consists of two pedicles(ped-klz, feet), which are attached to

the body, and two laminae (lami-n, thin plates), which extendfrom the transverse processes to the spinous process. Te vertebralarch and the posterior part of the body surround a large openingcalled the vertebral foramen. Te vertebral foramina of adjacentvertebrae combine to form the vertebral canal (table 7.4b), which

Table 7.4 General Structure of a Vertebra

Feature Description

Body Disk-shaped; usually the largest part with flat surfaces directed superiorly and inferiorly; forms the anterior wall of the

vertebral foramen; intervertebral disks are located between the bodies

Vertebral foramen Hole in each vertebra through which the spinal cord passes; adjacent vertebral foramina form the vertebral canal

Vertebral arch Forms the lateral and posterior walls of the vertebral foramen; possesses several processes and articular surfaces

Pedicle Foot of the arch with one on each side; forms the lateral walls of the vertebral foramen

Lamina Posterior part of the arch; forms the posterior wall of the vertebral foramen

Transverse process Process projecting laterally from the junction of the lamina and pedicle; a site of muscle attachment

Spinous process Process projecting posteriorly at the point where the two laminae join; a site of muscle attachment; strengthens the vertebral

column and allows for movement

Articular processes Superior and inferior projections containing articular facets where vertebrae articulate with each other; strengthen the

vertebral column and allow for movement

Intervertebral notches Form intervertebral foramina between two adjacent vertebrae through which spinal nerves exit the vertebral canal

Superiorarticular

process

Transverseprocess

Vertebralforamen

Body

Pedicle

Lamina

Vertebralarch

Spinousprocess

Superior view

Part ofvertebralcanal

Body

(cut)

Vertebralforamina

Spinousprocess(cut)

Lateral view,sagittal section

Superiorarticularfacet

Intervertebraldisk

Transverse process

Inferior articularprocess ofsuperior vertebra

Superior articularprocess of inferiorvertebra

Spinous processes

PosteriorAnterior

Pedicle

Superior articular process

Body

Inferior intervertebralnotch of superiorvertebra Intervertebra

foramenSuperior intervertebralnotch of inferiorvertebra

PosteriorAnterior

Space forintervertebraldisk

(d)

(a) (b)

(c)

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Spinous process ofseventh cervicalvertebra

Lumbar spinousprocesses

Superior borderof scapula

Scapula

Medial borderof scapula

Inferior angleof scapula

Spine of scapula

162 Chapter 7

contains the spinal cord and cauda equina, which is a collection ofspinal nerves (see chapter 11). Te vertebral arches and bodies pro-tect the spinal cord and cauda equina. A transverse processextends laterally from each side of the archbetween the lamina and pedicle, and a single spinous processis pres-ent at the junction between the two laminae (see table 7.4a). Tespinous processes can be seen and felt as a series of lumps down themidline of the back (figure 7.15). Te transverse and spinous pro-cesses are attachment sites for muscles moving the vertebral column. Support and movement of the vertebral column are made pos-sible by the articular processes. Each vertebra has two superiorandtwo inferior articular processes,with the superior processes of onevertebra articulating with the inferior processes of the next superiorvertebra (table 7.4c). Overlap of these processes helps hold the verte-brae together. Each articular process has a smooth articular facet

(faset, little face), which allows movement between the processes(see table 7.4a). Spinal nerves exit the vertebral canal through the intervertebralforamina(see table 7.4dand figure 7.14). Each intervertebral fora-men is formed by intervertebral notchesin the pedicles of adjacentvertebrae.

Spina Bifida

Sometimes vertebral laminae partly or completely fail to fuse (or

even fail to form) during fetal development, resulting in a condition

called spina bida (sp na bifi-da, split spine). This defect is most

common in the lumbar region. If the defect is severe and involves

the spinal cord (gure A), it may interfere with normal nerve function

below the point of the defect.

Dura mater

Posterior

Superior view

Enlarged fluid-filled space

Body of firstlumbar vertebra

Spinal cord

Cauda equina

Backmuscles

Incompletevertebral arch

Skin of back

Figure ASpina Bifida

17 What is the weight-bearing part of a vertebra?

18 Describe the structures forming the vertebral foramen and thevertebral canal. What structures are found within them?

19 What are the functions of the transverse and spinous processes?

20 Describe how superior and inferior articular processes help supportand allow movement of the vertebral column.

21 Where do spinal nerves exit the vertebral column?

Figure 7.15 Surface View of the Back Showing theScapula and Vertebral Spinous Processes

Intervertebral Disks

Intervertebral disks are pads of fibrocartilage located between thebodies of adjacent vertebrae (figure 7.16). Tey act as shock absorbersbetween the vertebral bodies and allow the vertebral column to bend.

Te intervertebral disks consist of an external annulus fibrosus(an-lus f-brsus, fibrous ring) and an internal, gelatinous nucleus pulpo-sus (pul-psus, pulp). Te disk becomes more compressed withincreasing age so that the distance between vertebrae and therefore theoverall height of the individual decreases. Te annulus fibrosus alsobecomes weaker with age and more susceptible to herniation.

Herniated, or Ruptured, Intervertebral Disk

A herniated,or ruptured, disk results from the breakage or bal-looning of the annulus brosus with a partial or complete release of

the nucleus pulposus (gure B). The herniated part of the disk may

push against and compress the spinal cord, cauda equina, or spinal

nerves, compromising their normal function and producing pain.

Herniation of the inferior lumbar intervertebral disks is most common,

but herniation of the inferior cervical disks is almost as common.

Transverse process

Spinous process

Superior view

Compressedspinal nerve root inintervertebral foramen

Herniatedportion of disk

Annulus fibrosus

Nucleus pulposus Intervertebraldisk

Spinal cordin vertebralcanal

Figure BHerniated DiskPart of the annulus brosus has been removed to reveal the nucleus

pulposus in the center of the disk and in the intervertebral foramen.



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Vertebral body

Nucleuspulposus

Annulusfibrosus

Intervertebralforamen

Intervertebraldisk

(a)Lateral view

(b)Superior view

Nucleus

pulposus

Annulusfibrosus


22 What is the function of the intervertebral disks? Name the two partsof the disk.

Regional Differences in Vertebrae

Te vertebrae of each region of the vertebral column have specificcharacteristics that tend to blend at the boundaries between regions

(figure 7.17 and table 7.5). Te cervical vertebrae all have a trans-verse foramenin each transverse process through which the vertebralarteries extend toward the head. Te first cervical vertebra is called the atlas (see figure 7.17a)because it holds up the head, just as Atlas in classical mythology held upthe world. Te atlas has no body, but it has large superior articular facets

where it articulates with the occipital condyles on the base of the skull.Tis joint allows the head to move in a yes motion or to tilt from sideto side. Te second cervical vertebra is called the axis(see figure 7.17b)

because it has a projection around which the atlas rotates to produce ano motion of the head. Te projection is called the dens(denz, tooth-shaped) or odontoid(-dontoyd, tooth-shaped), process. Te atlas does not have a spinous process (see figure 7.17a). Tespinous process of most cervical vertebrae end in two parts and are

Figure 7.16Intervertebral Disk

called bifid(bfid, split) spinous processes(see figure 7.17band c).Te spinous process of the seventh cervical vertebra is not bifid; it isoften quite pronounced and often can be seen and felt as a lumpbetween the shoulders (see figure 7.15) called thevertebra prominens.

Although the vertebra prominens usually marks the division betweenthe cervical and thoracic vertebrae, sometimes it is part of the sixthcervical vertebra or the first thoracic vertebra. Te thoracic vertebrae (see figure 7.14; figure 7.17d) haveattachment sites for the ribs. Te first 10 thoracic vertebrae havearticular facets on their transverse processes, where they articulate withthe tubercles of the ribs. Additional articular facets are on the superiorand inferior margins of the body where the heads of the ribs articulate(see Ribs and Costal Cartilages, p. 165). Toracic vertebrae havelong, thin spinous processes, which are directed inferiorly. Te lumbar vertebrae(see figure 7.14; figure 7.17e) have large,

thick bodies and heavy, rectangular transverse and spinous pro-cesses. Te superior articular facets face medially, and the inferiorarticular facets face laterally. When the superior articular surface ofone lumbar vertebra joins the inferior articulating surface of anotherlumbar vertebra, the arrangement tends to lock adjacent lumbarvertebrae together, giving the lumbar part of the vertebral columnmore stability and limiting rotation of the lumbar vertebrae. Tearticular facets in other regions of the vertebral column have a moreopen position, allowing for more movement but less stability.

Predict 3

Cervical vertebrae have small bodies, whereas lumbar vertebrae have large

bodies. Explain.

Te five sacral(skrl)vertebrae(see figure 7.14; figure 7.18)are fused into a single bone called the sacrum(skrum). Althoughthe margins of the sacral bodies unite after the twentieth year, theinterior of the sacrum is not ossified until midlife. Te transverseprocesses fuse to form the lateral parts of the sacrum. Te superiorlateral part of the sacrum forms wing-shaped areas called the alae(l, wings). Much of the lateral surfaces of the sacrum are ear-shaped auricular surfaces, which join the sacrum to the pelvicbones. Te spinous processes of the first four sacral vertebrae partiallyfuse to form projections, called the median sacral crest.Te spinousprocess of the fifth sacral vertebra does not form, thereby leaving asacral hiatus(h-tus), or gap, which exposes the sacral canal. Te

vertebral canal within the sacrum is called the sacral canal. Tesacral hiatus is used to gain entry into the sacral canal to administeranesthetic injectionsfor example, just before childbirth. Te ante-rior edge of the body of the first sacral vertebra bulges to form thesacral promontory,a landmark that separates the abdominal cavityfrom the pelvic cavity. Te sacral promontory can be felt during avaginal examination, and it is used as a reference point during mea-surement to determine if the pelvic openings are large enough toallow for normal vaginal delivery of a baby.

Te coccyx(koksiks, shaped like a cuckoos bill), or tailbone,usually consists of four more or less fused vertebrae (see figure 7.18).

Te vertebrae of the coccyx do not have the typical structure of mostother vertebrae. Tey consist of extremely reduced vertebral bodies,

without the foramina or processes, usually fused into a single bone.

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Posterior arch

Superior articularfacet

Spinous process(bifid)

Transverseprocess

Transverseforamen

Vertebral foramen

Dens(articulateswith atlas)

Body

(b)Axis (second cervical vertebra), superior view

Posterior arch

Superior articularfacet (articulateswith occipital condyle)

Facet for dens

Transverseprocess

Transverseforamen

Vertebral foramen

Anterior arch

(a)Atlas (first cervical vertebra), superior view


Spinous process(bifid)

Transverseprocess

Transverseforamen

Vertebral foramen

Body

Pedicle

Lamina

(c)Fifth cervical vertebra, superior view

Spinous process

Transverseprocess

Vertebral foramen

Pedicle

Lamina


Articular facetfor tubercle of rib

Superior articularfacet for ribhead

(d)Thoracic vertebra, superior view

Body


Spinous process

Transverseprocess

Vertebral foramenPedicle

Lamina

Body

(e)Lumbar vertebra, superior view

164 Chapter 7

Figure 7.17 Regional Differences in VertebraePosterior is shown at the top of each illustration.

Table 7.5 Comparison of Vertebral Regions

Feature Cervical Thoracic Lumbar

Body Absent in C1, small in others Medium-sized with articular facets for ribs Large

Transverse process Transverse foramen Articular facets for ribs, except T11 and T12 Square

Spinous process Absent in C1, bid in others, except C7 Long, angled inferiorly Square

Articular facets Face superior/inferior Face obliquely Face medial/lateral

Body Body

Spinousprocess Spinous

process

Spinousprocess

Transverseprocess Transverse

process

Superiorarticularprocess

TransverseprocessBody

Inferiorarticularfacet

Inferiorarticularfacet

Superior articular facetFacets for ribarticulation

Transverseforamen



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Ala

Sacral canal

Auricularsurface(articulateswith coxal bone)

Posteriorsacralforamina

Median sacralcrest

Sacral hiatus

Superiorarticular facet(articulateswith fifthlumbarvertebra)

Coccyx

Coccyx

Anteriorsacralforamina

Sacralpromontory

Ala

(a) Anterior view

(b) Posterior view

y

Te coccyx is easily broken in a fall in which a person sits down hardon a solid surface. Also, a mothers coccyx may be fractured duringchildbirth.

23 Describe the characteristics that distinguish the different typesof vertebrae.

24 Describe the movements of the head produced by the atlas and axis.

Predict 4

Which bone is the loneliest bone in the body?

Figure 7.18 Sacrum

Thoracic CageTe thoracic cage,or rib cage,protects the vital organs within thethorax and forms a semirigid chamber that can increase and decreasein volume during breathing. It consists of the thoracic vertebrae, theribs with their associated costal (rib) cartilages, and the sternum

(figure 7.19a).

Ribs and Costal Cartilages

Tere are 12 pairs of ribs,which are numbered 1 through 12, start-ing with the most superior rib. All of the ribs articulate posteriorly

with the thoracic vertebrae. Costal cartilagesattach many of the ribsanteriorly to the sternum. Movement of the ribs relative to the verte-brae and the flexibility of the costal cartilages allow the thoracic cageto change shape during breathing.

Te ribs are classified by their anterior attachments as true orfalse ribs. Te true ribsattach directly through their costal cartilagesto the sternum. Te superior seven pairs of ribs are true ribs. Tefalse ribsdo not attach to the sternum. Te inferior five pairs of ribsare false ribs. On each side, the three superior false ribs are joined bya common cartilage to the costal cartilage of the seventh true rib,

which in turn is attached to the sternum. Te two inferior pairs offalse ribs are also called floating ribsbecause they do not attach tothe sternum. Most ribs have two points of articulation with the thoracic verte-brae (figure 7.19band c). First, the headarticulates with the bodies oftwo adjacent vertebrae and the intervertebral disk between them. Tehead of each rib articulates with the inferior articular facet of the supe-rior vertebra and the superior articular facet of the inferior vertebra.Second, the tuberclearticulates with the transverse process of the infe-rior vertebra. Te neckis between the head and tubercle, and the body,or shaft, is the main part of the rib. Te angleof the rib is located justlateral to the tubercle and is the point of greatest curvature.

Rib Defects

Aseparated ribis a dislocation between a rib and its costal carti-

lage. As a result of the dislocation, the rib can move, override adjacent

ribs, and cause pain. Separation of the tenth rib is the most common.

The angle is the weakest part of the rib and may be fractured in

a crushing accident, such as an automobile accident. Broken rib ends

can damage internal organs, such as the lungs, spleen, liver, and

diaphragm.

Sternum

Te sternum,or breastbone, has three parts (see figure 7.19a): themanubrium(m-noobr-um, handle), the body,and the xiphoid(zifoyd, sword) process.Te sternum resembles a sword, with themanubrium forming the handle, the body forming the blade, and thexiphoid process forming the tip. At the superior end of the sternum,

a depression, called the jugular notch,is located between the endsof the clavicles where they articulate with the manubrium of thesternum. Te jugular notch can easily be found at the base of theneck (figure 7.20). A slight ridge, called the sternal angle,can be feltat the junction of the manubrium and the body of the sternum.

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Articular facetsforbody of vertebrae

Articular facet fortransverse processof vertebra

Angle

Neck

Tubercle

Head

BodySternal end

(b) Inferior view

Clavicle

Jugular notch

Seventh cervical vertebra

First thoracic vertebra

True ribs

Costalcartilage

False ribs(812)

Manubrium

Body

Xiphoid process

Sternum

Floating ribs

1

2

3

4

5

6

7

8

9

10

11

12 L1

T12

Sternalangle

(a) Anterior view

(c) Lateral view

Head of rib setagainst the inferiorarticular facetof the superior

vertebra

Head of rib setagainst the superiorarticular facetof the inferiorvertebra

Tubercle of ribset against thearticular faceton the transverse

processof theinferior vertebra

Angle of rib

Body of rib

Jugular notch

Clavicle

Acromial end of clavicle

Sternum

Acromion

Figure 7.20 Surface Anatomy Showing Bones of theUpper Thorax

Clinical Importance of the Sternum

The sternal angle is important clinically because the second rib is

found lateral to it and can be used as a starting point for counting

the other ribs. Counting ribs is important because they are land-

marks used to locate structures in the thorax, such as areas of the

heart. The sternum often is used as a site for taking red bone marrow

samples because it is readily accessible. Because the xiphoid processof the sternum is attached only at its superior end, it may be broken

during cardiopulmonary resuscitation (CPR) and then may lacerate

the underlying liver.

Figure 7.19Thoracic Cage(a) Entire thoracic cage as seen from an anterior view. ( b) Typical rib, inferior view.

(c) Photograph of two thoracic vertebrae and the proximal end of a rib, as seen from

the left side, showing the relationship between the vertebra and the head and tubercle

of the rib.



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Right upper limb

Right half ofpectoral girdle

Phalanges

Anterior view

Metacarpalb

ones

Clavicle

Scapula

Humerus

Radius

Ulna

Carpal bones

25 What are the functions of the thoracic (rib) cage? Distinguish amongtrue, false, and floating ribs, and give the number of each type.

26 Describe the articulation of the ribs with thoracic vertebrae.

27 Describe the parts of the sternum. What structures attach to thesternum?

7.3 Appendicular SkeletonTe appendicular skeleton (see figure 7.1) consists of the bones of theupperand lower limbsand the girdlesby which they are attachedto the body. Te termgirdlemeans a belt or a zone and refers to thetwo zones, pectoral and pelvic, where the limbs are attached to thebody. Te pectoral girdle attaches the upper limbs to the body andallows considerable movement of the upper limbs. Tis freedom of

movement allows the hands to be placed in a wide range of positionsto accomplish their functions. Te pelvic girdle attaches the lowerlimbs to the body, providing support while allowing movement. Tepelvic girdle is stronger and attached much more firmly to the bodythan is the pectoral girdle, and the lower limb bones in general arethicker and longer than those of the upper limb.

Pectoral GirdleTe pectoral (pekto-rl) girdle, or shoulder girdle, consists of

two scapulae (skap-l), or shoulder blades, and two clavicles(klavi-klz, key), or collarbones (see figure 7.1). Each humerus(arm bone) attaches to a scapula, which is connected by a clavicleto the sternum (figure 7.21). Te scapula is a flat, triangular bone(figure 7.22) that can easily be seen and felt in a living person (seefigure 7.15). Te glenoid(glenoyd) cavityis a depression where thehumerus connects to the scapula. Te scapula has three fossae wheremuscles extending to the arm are attached. Te scapular spine,

which runs across the posterior surface of the scapula, separates two

of these fossae. Te supraspinous fossais superior to the spine andthe infraspinous fossais inferior to it. Te subscapular fossais onthe anterior surface of the scapula. Te acromion (-krm-on,akron,tip + omos,shoulder) is an extension of the spine forming thepoint of the shoulder. Te acromion forms a protective cover for theshoulder joint and is the attachment site for the clavicle and some ofthe shoulder muscles. Te coracoid(kr-koyd, crows beak) pro-cesscurves below the clavicle and provides attachment for arm andchest muscles. Te clavicle is a long bone with a slight sigmoid (S-shaped) curve(figure 7.23) and is easily seen and felt in the living human (see figure7.20). Te acromial (lateral) end of the clavicle articulates withthe acromion of the scapula, and the sternal (medial) endarticulates

with the manubrium of the sternum. Te pectoral girdles only attach-ment to the axial skeleton is at the sternum. Mobility of the upperlimb is enhanced by movement of the scapula, which is possiblebecause the clavicle can move relative to the sternum. For example,feel the movement of the clavicle when shrugging the shoulders.

28 Name the bones that make up the pectoral girdle. Describe theirfunctions.

29 What are the functions of the acromion and the coracoid process ofthe scapula?

Figure 7.21 Bones of the Pectoral Girdle and Upper Limb

Predict 5

How does a broken clavicle change the position of the upper limb?

Upper LimbTe upper limb consists of the bones of the arm, forearm, wrist, andhand (see figure 7.21).

Arm

Te arm is the part of the upper limb from the shoulder to the elbow. It

contains only one bone, the humerus(figure 7.24). Te humeral headarticulates with the glenoid cavity of the scapula. Te anatomical neck,around the head of the humerus, is where connective tissue holding theshoulder joint together attaches. Te surgical neckis so named becauseit is a common fracture site that often requires surgical repair. If itbecomes necessary to remove the humeral head because of disease orinjury, it is removed down to the surgical neck. Te greater tubercleandthe lesser tubercleare sites of muscle attachment. Te intertuberculargroove,or bicipital(b-sipi-tl) groove, between the tubercles contains

one tendon of the biceps brachii muscle. Te deltoid tuberosity islocated on the lateral surface of the humerus a little more than a third ofthe way along its length and is the attachment site for the deltoid muscle. Condyles on the distal end of the humerus articulate with thetwo forearm bones. Te capitulum (k-pit-lum, head-shaped) is

168 Chapter 7


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Body of clavicle

Acromial (lateral)end

Sternal (medial)end

Superior view

Figure 7.22Right Scapula

Figure 7.23Right Clavicle

Acromion

Supraglenoid tubercle

Glenoid cavity

Lateral border

Coracoid process

Scapular notch

Superior borderSuperior angle

Subscapularfossa

Medial border

Inferior angle

Spine

Supraspinousfossa

Coracoid process

Acromion

Glenoid cavity

Infraglenoid tubercle

Infraspinousfossa

Lateral border

(a)Anterior view

Infraglenoidtubercle

(b)Posterior view

very rounded and articulates with the radius. Te trochlea(trokl-,

spool) somewhat resembles a spool or pulley and articulates with theulna. Proximal to the capitulum and the trochlea are the medialandlateral epicondyles,which are points of muscle attachment for themuscles of the forearm. Tey can be found as bony protuberancesproximal to the elbow (figure 7.25).

Forearm

Te forearm has two bones (figure 7.26). Te ulnais on the medial(little finger) side of the forearm, whereas the radiusis on the lateral

(thumb) side of the forearm. Te proximal end of the ulna has a C-shaped articular surfacecalled the trochlear notch, or semilunar notch, that fits over thetrochlea of the humerus, forming most of the elbow joint. Te trochlearnotch is bounded by two processes. Te olecranon(-lekr-non, the

point of the elbow) is the posterior process forming the tip of the elbow(see figure 7.25). It can easily be felt and is commonly referred to as theelbow. Posterior arm muscles attach to the olecranon. Te smaller,anterior process is the coronoid(kro-noyd, crows beak) process. Te proximal end of the radius is the head.It is concave andarticulates with the capitulum of the humerus. Movements of theradial head relative to the capitulum and of the trochlear notchrelative to the trochlea allow the elbow to bend and straighten. Telateral surfaces of the radial head form a smooth cylinder where theradius rotates against the radial notchof the ulna. As the forearmsupinates and pronates (see ypes of Movements, p. 183), theproximal end of the ulna stays in place and the radius rotates.

Predict 6

Explain the functions of the olecranon, coronoid, and radial fossae on the distal

humerus (see gure 7.24).

Just distal to the elbow joint, the radial tuberosity and theulnar tuberosityare attachment sites for arm muscles. Te distal end of the ulna has a small head,which articulates

with both the radius and the carpal (wrist) bones (see figure 7.26).Te head can be seen as a prominent lump on the posterior, medial

(ulnar) side of the distal forearm (see figure 7.25). Te distal end ofthe radius, which articulates with the ulna and the carpal bones, issomewhat broadened. Te ulna and radius have small styloid(stloyd, shaped like a stylus or writing instrument) processes to

which ligaments of the wrist are attached.



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Head

Anatomicalneck

Lessertubercle

Surgicalneck

Radialgroove

Olecranonfossa

Greatertubercle

Intertuberculargroove

Deltoidtuberosity

Lateralsupracondylarridge

Radialfossa

Lateralepicondyle

Capitulum

Trochlea

Coronoidfossa

Medialsupracondylarridge

Medialepicondyle

Trochlea

Lateralepicondyle

(b) Posterior view(a) Anterior view

Figure 7.24Right Humerus

Wrist

Te wrist is a relatively short region between the forearm and hand; itis composed of eight carpal(karpl) bonesarranged into two rows of

four each (figure 7.27). Te proximal row of carpal bones, lateral tomedial, includes the scaphoid (skafoyd, boat-shaped), lunate(loont, moon-shaped), triquetrum (tr-kwtrum, tr-kwetrum,three-cornered), and pisiform(pisi-frm, pea-shaped). Te distal rowof carpal bones, from medial to lateral, includes the hamate(hamt,hook), capitate(kapi-tt, head), trapezoid(trape-zoyd, a four-sidedgeometric form with two parallel sides), and trapezium(tra-pz-um,a four-sided geometric form with no two sides parallel). A number ofmnemonics have been developed to help students remember the carpal

bones. Te following mnemonic allows students to remember them inorder from lateral to medial for the proximal row (top) and frommedial to lateral (by the thumb) for the distal row: So Long op Part,Here Comes he humbthat is Scaphoid, Lunate, riquetrum,Pisiform, Hamate, Capitate, rapezoid, and rapezium.

Radius Fractures

The radius is the most commonly fractured bone in people over

50 years old. It is often fractured as the result of a fall on an out-

stretched hand, which results in posterior displacement of the hand.

Typically, there is a complete transverse fracture of the radius 2.5 cm

proximal to the wrist. The fracture is often comminuted or impacted.

Such a fracture is called a Colles fracture.

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Olecranon

Head

Neck

Radial tuberosity

Radius

Styloid process

(b) Anterior view (c) Lateral view of ulna

Trochlear (semilunar) notch

Radial notch of ulna

Coronoid processRadial notch of ulna

Interosseousridges Ulna

Head

Styloid process

Ulnar tuberosity

Ulnar notch of radius

Radial notchof ulna

Head ofradius

Olecranon

Coronoidprocess

Trochlear(semilunar)notch

(a) Proximal view

Viewin (a)

Figure 7.25 Surface Anatomy Showing Bones of the Pectoral Girdle and Upper Limb

Heads ofmetacarpal bones

(knuckles)

Olecranon

Lateral epicondyle

Head of ulna Acromion

Medial borderof scapula

Olecranon

Medialepicondyle

Figure 7.26 Right Ulna and Radius



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LunateScaphoid

Triquetrum

Pisiform

Carpal bones(proximalrow)

Radius

Proximal

phalanxof thumb

Proximal

phalanxof finger

Middle phalanxof finger

Distal phalanxof finger

Anterior view

Ulna

Trapezoid

Trapezium

CapitateHamate

Digits

Metacarpals

Distal

phalanx

of thumb

Carpal bones(distal row)

1

23 4

5

Coxalbone

Sacrum

Femur

Patella

Right lower limb

Right half ofpelvic girdle

Tibia

Fibula

Phalanges

Anterior view

Tarsal bones

Metatarsal bones

Figure 7.27 Bones of the Right Wrist and Hand

Carpal Tunnel Syndrome

The bones and ligaments on the anterior side of the wrist form a

carpal tunnel, which does not have much give. Tendons and

nerves pass from the forearm through the carpal tunnel to the hand.

Fluid and connective tissue can accumulate in the carpal tunnel as a

result of inflammation associated with overuse or trauma. The

inflammation can also cause the tendons in the carpal tunnel to

enlarge. The accumulated fluid and enlarged tendons can apply

pressure to a major nerve passing through the tunnel. The pressure

on this nerve causes carpal tunnel syndrome, the symptoms of

which are tingling, burning, and numbness in the hand

Hand

Five metacarpal(met-karpl, after the carpals) bonesare attached

to the carpal bones and constitute the bony framework of the hand (seefigure 7.27). Tey are numbered 1 through 5, starting with the mostlateral metacarpal, at the base of the thumb. Te distal ends of themetacarpal bones help form the knuckles of the hand (see figure 7.25). Te five digitsof each hand include one thumb and four fingers.Te digits are also numbered 1 through 5, starting from the thumb.Each digit consists of small long bones called phalanges (f-lanjz,sing. phalanx, a line or wedge of soldiers holding their spears, tipsoutward, in front of them). Te thumb has two phalanges, calledproximal and distal. Each finger has three phalanges designatedproximal, middle, and distal. One or two sesamoid (ses-moyd,resembling a sesame seed) bones(not shown in figure 7.27) often formnear the junction between the proximal phalanx and the metacarpal ofthe thumb. Sesamoid bones are small bones located within some ten-dons, increasing their mechanical advantage where they cross joints.

30 Distinguish between the anatomical and surgical necks of the humerus.

31 Name the important sites of muscle attachment on the humerus.

32 Give the points of articulation between the scapula, humerus, radius,ulna, and wrist bones.

33 What is the function of the radial and ulnar tuberosities?

Of the styloid processes?34 Name the part of the ulna commonly referred to as the elbow.

35 List the eight carpal bones.

36 What bones form the hand? The knuckles?

37 Name the phalanges in a thumb and in a nger.

Predict 7 Explain why a dried, articulated skeleton appears to have much longer ngers

than are seen in a hand with the soft tissue intact.

Pelvic GirdleTe pelvic girdle is the place of attachment for the lower limbs, itsupports the weight of the body, and it protects internal organs(figure 7.28). Te right and left coxal(koksul) bones,os coxae, orhipbones, join each other anteriorly and the sacrumposteriorly toform a ring of bone called the pelvic girdle. Te pelvis (pelvis,basin) includes the pelvic girdle and the coccyx (figure 7.29). Because

the pelvic girdle is a complete bony ring, it provides more stable sup-port but less mobility than the incomplete ring of the pectoral girdle.In addition, the pelvis in a woman protects a developing fetus andforms a passageway through which the fetus passes during delivery.

Figure 7.28 Bones of the Pelvic Girdle and Lower Limb

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Anterosuperior view

Ischium

Pubis

Ilium

Sacrum

Coxal

bone

Sacroiliac joint

Anterior superioriliac spine

Acetabulum

Coccyx

Iliac crest

Obturatorforamen

Subpubic angle

Symphysis pubis

Sacral promontory

Figure 7.29 Pelvis

Each coxal bone is formed by three bones fused to one anotherto form a single bone (see figure 7.29). Te ilium(il-um, groin) isthe superior, the ischium (isk-um, hip) is inferior and posterior,and the pubis(pbis, genital hair) is inferior and anterior. Te coxalbones join anteriorly at the symphysis(simfi-sis, a coming together)pubis, or pubic symphysis. Posteriorly, each coxal bone joins the

sacrum at the sacroiliac joint. A fossa called the acetabulum(as-e-tab-lum, a shallow vinegarcupa common household item in ancient times) is located on thelateral surface of each coxal bone (figure 7.30a). In a child, the jointsbetween the ilium, ischium, and pubis can be seen. Te bones fusetogether in some locations by the seventh or eighth year. Completefusion within the acetabulum occurs between the sixteenth andeighteenth years. Te acetabulum is the point of articulation of thelower limb with the pelvic girdle. Te articular, lunate surfaceof the

acetabulum is crescent-shaped and occupies only the superior andlateral aspects of the fossa (figure 7.30b). Inferior to the acetabulum isthe large obturator(obtoo-r-tor, to occlude or close up) foramen.In life, the obturator foramen is almost completely closed off by aconnective tissue membrane, which separates the pelvic cavity frommore superficial structures. Despite its large size, only a few smallblood vessels and nerves pass through the obturator foramen. Te superior portion of the ilium is called the iliac crest (seefigure 7.30b; figure 7.30c). Te crest ends anteriorly as the anterior

superior iliac spine and posteriorly as the posterior superior iliacspine.Te crest and anterior spine can be felt and even seen in thinindividuals (figure 7.31). Te anterior superior iliac spine is an impor-tant anatomical landmark used, for example, to find the correct loca-tion for giving gluteal injections into the hip. A dimple overlies theposterior superior iliac spine just superior to the buttocks.

Gluteal Injections

The large gluteal (hip) muscles (see chapter 9) are a common site

for intramuscular injections. Gluteal injections are made in the

superolateral region of the hip (gure C) so as to avoid a large nerve

(the sciatic nerve) (see chapter 11) located more posteriorly. Thelandmarks for such an injection are the anterior superior iliac spine

and the tubercle of the iliac crest, which lies about one-third of the

way along the iliac crest from anterior to posterior.

Figure C Gluteal Injection Site

Posterior superioriliac spine

Tubercle of iliac crest Site of safe areafor injection

Anterior superioriliac spine



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Acetabulum

Ischium

Ilium

Cartilage inyoung pelvis

Pubis

Obturator

foramen

Iliac crest

Posteriorsuperioriliac spine

Posterior inferioriliac spine

Greater sciaticnotch

Ischial spine

Ischium

Lesser sciaticnotch

Ischial tuberosity

Ischial ramus

Obturator foramen

Symphysis pubis

Inferior pubic ramus

Acetabulum

Pelvic brim

Acetabular notch

Lunatesurface

Anterior inferioriliac spine

Anterior superior

iliac spine

Ilium

Superior pubic ramus

Iliac fossaAuricular surface(articulateswith sacrum)

Posterior superioriliac spine

Posterior inferioriliac spine

Greater sciaticnotch

Ischium

Ischial spine

Ischial ramus

Lesser sciaticnotch

(a)Lateral view

(b)Lateral view (c)Medial view

Pubis

Pubic tubercle

Tubercle of iliaccrest

Figure 7.30Coxal Bone(a) Right coxal bone of a young adolescent. The ilium, ischium, and pubis (in bold) form the incompletely ossied coxal bone. They are joined near the center of the

acetabulum by cartilage. (b) Right coxal bone of an adult, lateral view. (c) Right coxal bone of an adult, medial view. The ilium ( green), ischium (gold), and pubis (purple)fuse together to form a single bone.

Inferior to the anterior superior iliac spine is the anterior infe-rior iliac spine(see figure 7.30). Te anterior iliac spines are attach-ment sites for anterior thigh muscles. Inferior to the superiorposterior iliac spine are the posterior inferior iliac spine, ischialspine,and ischial tuberosity.Te posterior iliac spines and ischialtuberosity are attachment sites for ligaments anchoring the coxalbone to the sacrum. Te auricular surfaceof the ilium (see figure7.30c) joins the auricular surface of the sacrum (see figure 7.18) toform the sacroiliac joint. Te ischial tuberosity is also an attachmentsite for posterior thigh muscles, and it is the part of the coxal boneon which a person sits.

Te greater sciatic notchis superior to the ischial spine and thelesser sciatic notch is inferior to it (see figure 7.30). Nerves andblood vessels pass through the sciatic notches. Te pelvis is divided into the false pelvisand the true pelvisbyan imaginary plane passing from the sacral promontory to the pubiccrest. Te pelvic brim is the bony boundary of this plane (figure7.32). Te false pelvis, which is the expanded part of the pelvis supe-rior to the pelvic brim, is also the inferior part of the abdominalcavity (see figure 1.15). Te true pelvis is inferior to the pelvic brimand is completely surrounded by bone. Te pelvic inletis the supe-rior opening of the true pelvis formed by the pelvic brim. Te pelvic

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Iliac crest

Anterior

superioriliac spine

Anterior inferioriliac spine(rarely visible)

Greatertrochanter

Sacralpromontory

Subpubic angle

Subpubic angle

Pelvicbrim

Pelvic

inlet(reddashed

line)Symphysispubis

Pelvicoutlet(blue

dashedline)

Male

Female

(a) Anterosuperior view

(b) Anterosuperior view

Symphysispubis

Ischialspine

Coccyx

Figure 7.31 Surface Anatomy Showing an AnterolateralView of the Coxal Bone and Femur

Figure 7.32 Comparison of the Male and Female Pelvis(a) Male. The pelvic inlet (red dashed line) and outlet (blue dashed line) are small,

and the subpubic angle is less than 90 degrees. ( b) Female. The pelvic inlet (red

dashed line) and outlet (blue dashed line) are larger, and the subpubic angle is90 degrees or greater.

outletis the inferior opening of the true pelvis bordered by the infe-rior margin of the pubis, the ischial spines, the ischial tuberosities,and the coccyx. In life, muscles of the pelvic diaphragm span thepelvic outlet (see chapter 9). Te pelvic cavityis the space betweenthe pelvic inlet and the pelvic diaphragm.

Comparison of the Male and Female Pelvis

Te male pelvis usually is more massive than the female pelvis as aresult of the greater weight and size of the male, but the female pelvisis broader and has a larger, more rounded pelvic inlet and outlet (seefigure 7.32), consistent with the need to allow a fetus to pass throughthese openings in the female pelvis during delivery. If the pelvic outletis too small for normal delivery, it can be accomplished by cesareansection,which is the surgical removal of the fetus through the abdom-inal wall. able 7.6 lists additional differences between the male andfemale pelvis.

38 Dene the pelvic girdle. What bones fuse to form each coxal bone?Where and with what bones does each coxal bone articulate?

39 Name the important sites of muscle and ligament attachment on thepelvis.

40 Distinguish between the true pelvis and the false pelvis.

41 Describe the differences between a male and a female pelvis.

Lower LimbTe lower limb consists of the bones of the thigh, leg, ankle, and foot(see figure 7.28).

Thigh

Te thigh is the region between the hip and the knee. Te thigh, likethe arm, contains a single bone, called the femur(figure 7.33). Teheadof the femur articulates with the acetabulum of the coxal bone,and the neckof the femur connects the head to the body(shaft) ofthe femur. Te greater trochanter (tr-kanter, runner) and thelesser trochanterare attachment sites for muscles that fasten the hipto the thigh. Te greater trochanter and its attached muscles form abulge that can be seen as the widest part of the hips (see figure 7.31).Te pectineal line, gluteal tuberosity, and the linea aspera are

Table 7.6 Differences Between the Male andFemale Pelvis (See Figure 7.32)

Area Description

General In females, somewhat lighter in weight and wider

laterally but shorter superiorly to inferiorly andless funnel-shaped; less obvious muscle

attachment points in females than in males

Sacrum Broader in females, with the inferior part directed

more posteriorly; the sacral promontory does

not project as far anteriorly in females

Pelvic inlet Heart-shaped in males; oval in females

Pelvic outlet Broader and more shallow in females

Subpubic angle Less than 90 degrees in males;

90 degrees or more in females

Ilium More shallow and flared laterally in females

Ischial spines Farther apart in females

Ischial tuberosities Turned laterally in females and medially in males

Head



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Head

Neck

Greater trochanter

Lateral epicondyle

Lateral condyle

Body (shaft) of femur

Head

Neck

Medialepicondyle

Adductor tubercle

Greater trochanter

Lateral epicondyle

Medialcondyle

Patellar groove

Intertrochanteric line Intertrochanteric crest

Pectineal line

Gluteal tuberosity

Linea aspera

Intercondylar fossa

Lesser trochanter

Foveacapitis

(a) Anterior view (b) Posterior view

other muscle attachment sites. Te distal end of the femur hasmedialand lateral condylesthat articulate with the tibia (leg bone).Located proximally to the condyles are the medialand lateral epi-condyles,important sites of ligament attachment. Te epicondylescan be felt just proximal to the knee joint (figure 7.34). An adductortubercle, to which muscles attach, is located just proximal to themedial epicondyle.

Figure 7.33Right Femur

CASE STUDY | Fracture of the Femoral NeckAn 85-year-old woman who lived alone was found lying on her

kitchen floor by her daughter, who had come to check on her

mother. The woman could not rise, even with help, and when she

tried she experienced extreme pain in her right hip. Her daughter

immediately dialed 911, and paramedics took her mother to

the hospital.

The elderly womans hip was x-rayed in the emergency room,

and it was determined that she had a fracture of the right femoral

neck. A femoral neck fracture is commonly, but incorrectly, called a

broken hip. Two days later, she received a partial hip replacement in

which the head and neck of the femur, but not the acetabulum, were

replaced. In falls involving femoral neck fracture, it is not always clear

whether the fall caused the femoral neck to fracture or whether a

fracture of the femoral neck caused the fall. Femoral neck fractures

are among the most common injuries resulting in morbidity (dis-

ease) and mortality (death) in older adults. Four percent of women

over age 85 experience femoral neck fractures each year. Only about

25% of victims fully recover from the injury. Despite treatment with

anticoagulants and antibiotics, about 5% of patients with femoral

neck fractures develop deep vein thrombosis (blood clot) and about

5% develop wound infections, either of which can be life-threatening.

Hospital mortality is 1%7% among patients with femoral neck frac-

tures, and nearly 20% of femoral neck fracture victims die within

3 months of the fracture.

Predict 8

The risk of fracture of the femoral neck increases dramatically with age,

and 81% of victims are women. The average age of those who suffer such

an injury is 82. Why is the femoral neck so commonly injured? (Hint:See g-

ure 7.1.) Why are elderly women most commonly affected?

CalcaneusMedial epicondyle of femur

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Lateral malleolus

Patella

Tibial tuberosity

Anterior crest of tibia

Medial malleolus

Head of fibula

CalcaneusMedial epicondyle of femur

Lateral epicondyle of femur

Anteriorsurface

Medialfacet

Posteriorsurface

Lateralfacet

(a) Anterior view

(b) Posterior view

Lateralcondyle

Head

Intercondylareminence

Medialcondyle

Tibialtuberosity

Tibia

Anteriorcrest

Fibula

Lateralmalleolus

Distalarticulationof tibia andfibula

Medialmalleolus

Anterior view

Proximalarticulationof tibia and fibula

Te patella (figure 7.35), or kneecap, articulates with the patel-lar grooveof the femur (see figure 7.33). It is a large sesamoid bonelocated within the tendon of the quadriceps femoris muscle group,

which is the major muscle group of the anterior thigh. Te patellaholds the tendon away from the distal end of the femur and thereforechanges the angle of the tendon between the quadriceps femorismuscle and the tibia, where the tendon attaches. Tis change in angleincreases the force that can be applied from the muscle to the tibia.

As a result of this increase in applied force, less muscle contractionforce is required to move the tibia.

Leg

Te leg is the part of the lower limb between the knee and the ankle.Like the forearm, it consists of two bones: the larger tibia(tib-), orshinbone, and the smaller fibula(fib-l, resembling a clasp or buckle)(figure 7.36). Te rounded condyles of the femur rest on the flat medialandlateral condyleson the proximal end of the tibia. Body weight istransmitted from the femur through the tibia to the ankle.

Figure 7.34 Surface Anatomy Showing Bones of the Lower Limb

Figure 7.35Right Patella

Figure 7.36 Right Tibia and Fibula

Te intercondylar eminenceis a ridge between the condyles. Atibial tuberosity,which is the attachment point for the quadricepsfemoris muscle group, can easily be seen and felt just inferior to thepatella (see figure 7.35). Te anterior crestforms a sharp edge on theshin. Te distal end of the tibia is enlarged to form the medial mal-leolus (ma-l-lus, mallet-shaped), which helps form the medialside of the ankle joint.


Te fibula does not articulate with the femur but has a small proxi- Te metatarsal bones and phalanges of the foot are arranged in


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pmal headwhere it articulates with the tibia. Te distal end of the fibulais also slightly enlarged as the lateral malleolusto create the lateral wallof the ankle joint. Te lateral and medial malleoli can be felt and seen asprominent lumps on both sides of the ankle (see figure 7.35).

FootTe proximal portion of the foot consists of seven tarsal(tarsl, thesole of the foot) bones(figure 7.37). Te tarsal bones are the talus(tlus, ankle bone), calcaneus(kal-kn-us, heel), cuboid(kboyd,cube-shaped), and navicular (n-viky-lr, boat-shaped) bones andthe medial, intermediate, and lateral cuneiforms (kn-i-frmz,

wedge-shaped). A mnemonic for the distal row of bones is MILCthat is, Medial, Intermediate, and Lateral cuneiforms and the Cuboid.Te mnemonic for the proximal three bones is No Tanks Cow

that is, Navicular, alus, and Calcaneus. Te talus articulates with the tibia and fibula to form the ankle

joint. It is an unusual bone in that no muscles attach to it. Te calcaneusforms the heel and is the attachment point for the large calf muscles.

Fractures of the Malleoli

Turning the plantar surface of the foot outward so that it faces later-

ally is called eversion. Forceful eversion of the foot, such as

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