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The Skeleton

Consists of bones, cartilage, joints, and ligamentsComposed of 206 named bones grouped into two divisions

Axial skeleton (80 bones)Appendicular skeleton (126 bones)

Bone Markings

Bone markings may be:Elevations and ProjectionsProcesses that provide attachment for tendons and ligamentsProcesses that help form joints (articulations)Depressions and openings for passage of nerves and blood vessels

The Axial Skeleton

Formed from 80 named bonesConsists of skull, vertebral column, and bony thorax

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The Skull

Formed by cranial and facial bonesThe cranium serves to:

Enclose brainProvide attachment sites for some head and neckmuscles

Facial bones serve to:Form framework of the faceForm cavities for the sense organs of sight, taste, and smellProvide openings for the passageof air and foodHold the teethAnchor muscles of the face

Figure 7.2a

Overview of Skull Geography

The skull contains approximately 85 named openings

Foramina, canals, and fissuresProvide openings for important structures

Spinal cordBlood vessels serving the brain12 pairs of cranial nerves

Overview of Skull Geography

Facial bones form anterior aspectCranium is divided into cranial vault and the baseInternally, prominent bony ridges divide skull intodistinct fossae cranial vault

base

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Overview of Skull Geography

The skull contains smaller cavitiesMiddle and inner ear cavities – in lateral aspect of cranial baseNasal cavity – lies in and posterior to the noseOrbits – house the eyeballsAir-filled sinuses – occur in several bones around the nasal cavity

Cranial Bones

Formed from eight large bonesPaired bones include

Temporal bonesParietal bones

Unpaired bones includeFrontal boneOccipital boneSphenoid boneEthmoid bone

Sutures

Four sutures of the craniumCoronal suture – runs in the coronal plane

Located where parietal bones meet the frontal bone

Squamous suture – occurs where each parietal bone meets a temporal bone inferiorlySagittal suture – occurs where right and left parietal bones meet superiorlyLambdoid suture – occurs where the parietal bones meet the occipital bone posteriorly

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Facial Bones

Unpaired bonesMandible and vomer

Paired bonesMaxillae, zygomatics, nasals, lacrimals, palatines, and inferior nasal conchae

Special Parts of the Skull

OrbitsNasal cavityParanasal sinusesHyoid bone

Orbits

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Nasal Cavity

Nasal Septum

Figure 7.9b

Paranasal Sinuses

Air-filled sinuses are located within Frontal boneEthmoid boneSphenoid boneMaxillary bones

Lined with mucous membraneServe to lighten the skull

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Paranasal Sinuses

Figure 7.11a, b

Figure 7.12

The Hyoid Bone

Lies inferior to the mandibleThe only bone with no direct articulation with any other boneActs as a movable base for the tongue

The Vertebral Column Formed from 26 bones in the adultTransmits weight of trunk to the lower limbsSurrounds and protects the spinal cordWith vertebral curves, acts as shock absorberServes as attachment sites for muscles of the neck and backHeld in place by ligaments

Anterior and posterior longitudinal ligaments Ligamentum flavum Supraspinus and interspinous ligaments

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Intervertebral Discs

Cushion-like pads between vertebraeAct as shock absorbersCompose about 25% of height of vertebral columnComposed of nucleus pulposus and annulus fibrosis

Intervertebral Discs

Nucleus pulposus The gelatinous inner sphere of intervertebral discEnables spine to absorb compressive stresses

Annulus fibrosisAn outer collar of ligaments and fibrocartilage Contains the nucleus pulposusFunctions to bind vertebrae together, resist tension on the spine, and absorb compressive forces

Ligaments and Intervertebral Discs

Figure 7.14a

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Ligaments and Intervertebral Discs

Figure 7.14b, c

Regions and Normal Curvatures

Vertebral column is about 70 cm (28 inches) Vertebral column is divided into five major regions

Cervical vertebrae – 7 vertebrae of the neck regionThoracic vertebrae – 12 vertebrae of the thoracic regionLumbar vertebrae – 5 vertebrae of the lower backSacrum – inferior to lumbar vertebrae – articulates with coxal bonesCoccyx – most inferior region of the vertebral column

Regions and Normal Curvatures

Four distinct curvatures give vertebral column an S-shape

Cervical and lumbar curvatures–concave posteriorlyThoracic and sacral curvatures –convex posteriorly

Curvatures increase the resilience of the spine

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General Structure of Vertebrae

Regions Vertebral Characteristics

Specific regions of the spine perform specific functionsTypes of movement that occur between vertebrae

Flexion and extensionLateral flexionRotation in the long axis

Cervical Vertebrae Seven cervical vertebrae (C1 – C7) – smallest and lightest vertebraeC3 – C7 are typical cervical vertebrae

Body is wider laterallySpinous processes are short and bifid (except C7)Vertebral foramen are large and triangularTransverse processes contain transverse foraminaSuperior articular facets face superoposteriorly

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Cervical Vertebrae

The Atlas

C1 is termed the atlasLacks a body and spinous processSupports the skull

Superior articular facets receive the occipital condyles

Allows flexion and extension of neck Nodding the head “yes”

The Atlas

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The Axis

Has a body and spinous processDens (odontoid process) projects superiorly

Formed from fusion of the body of the atlas with the axisActs as a pivot for rotation of the atlas and skullParticipates in rotating the head from side to side

Shaking the head to indicate “no”

Thoracic Vertebrae (T1 – T12)

All articulate with ribsHave heart-shaped bodies from the superior viewEach side of the body bears demifacts for articulation with ribs

T1 has a full facet for the first ribT10 – T12 only have a single facet

Thoracic Vertebrae

Spinous processes are long and point inferiorlyVertebral foramen are circularTransverse processes articulate with tubercles of ribsSuperior articular facets point posteriorlyInferior articular processes point anteriorly

Allows rotation and prevents flexion and extension

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Lumbar Vertebrae (L1 – L5)Bodies are thick and robustTransverse processes are thin and taperedSpinous processes are thick, blunt, and point posteriorlyVertebral foramina are triangularSuperior and inferior articular facets directly mediallyAllows flexion and extension – rotation prevented

Sacrum (S1 – S5)

Shapes the posterior wall of pelvisFormed from 5 fused vertebraeSuperior surface articulates with L5

Inferiorly articulates with coccyxSacral promontory – where the first sacral vertebrae bulges into pelvic cavityCenter of gravity is 1 cm posterior to sacral promontory

SacrumSacral foramina

Ventral foramina – passage for ventral rami of sacral spinal nervesDorsal foramina – passage for dorsal rami of sacral spinal nerves

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Coccyx

Is the "tailbone" Formed from 3-5 fused vertebraeOffers only slight support to pelvic organs

Bony Thorax

Forms the framework of the chestComponents of the bony thorax

Thoracic vertebrae – posteriorlyRibs – laterally Sternum and costal cartilage – anteriorly

Protects thoracic organsSupports shoulder girdle and upper limbsProvides attachment sites for muscles

The Bony Thorax

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The Bony Thorax

Figure 7.19b

Sternum

Formed from 3 sectionsManubrium – superior section

Articulates with medial end of clavicles

Body – bulk of sternumSides are notched at articulations for costal cartilage of ribs 2-7

Xiphoid process – inferior end of sternumOssifies around age 40

Sternum

Anatomical landmarksJugular notch – central indentation at superior border of the manubriumSternal angle – a horizontal ridge where the manubrium joins the body

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Ribs

All ribs attach to vertebral column posteriorlyTrue ribs - superior seven pairs of ribs

True because? They attach to sternum by their own costal cartilage

False ribs – inferior five pairs of ribs

False because? They attach via inferior true rib costal cartilage, or not at all…. As in

Floating ribs… no attachment anteriorly

Ribs

Figure 7.20a

Disorders of the Axial Skeleton

Abnormal spinal curvaturesScoliosis – an abnormal lateral curvatureKyphosis – an exaggerated thoracic curvatureLordosis – an accentuated lumbar curvature – "swayback"

Stenosis of the lumbar spine – a narrowing of the vertebral canal

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Bones, Part 2:The Appendicular

Skeleton

The Appendicular Skeleton

Pectoral girdle attaches the upper limbs to the trunk (axial skeleton)Pelvic girdle attaches the lower limbs to the trunk (axial skeleton)Upper and lower limbs share the same structural plan, however function is different . . .

sometimes

The Pectoral Girdle

Consists of the clavicle and the scapulaPectoral girdles do not quite encircle the body completely

The medial ends of the clavicles articulate with the manubrium and first ribLaterally – the ends of the clavicles join the scapulaeScapulae do not join each other or the axial skeleton

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The Pectoral Girdle

Provides attachment for many muscles that move the upper limbGirdle is very light and upper limbs are mobile

Only clavicle articulates with the axial skeletonSocket of the shoulder joint (glenoid cavity) is shallow

Good for flexibility – bad for stability

Superficial musculature

deep musculature

ClaviclesStructurally:

Extend horizontally across the superior thoraxSternal end articulates with the manubriumAcromial end articulates with scapula

Functionally:Provide attachment for muscles Hold the scapulae and arms laterallyTransmit compression forces from the upper limbs to the axial skeleton

Scapulae

Lie on the dorsal surface of the rib cageLocated between ribs 2-7Have three borders

Superior, medial (vertebral), and lateral (axillary)Have three angles

Lateral, superior, and inferiorHas pronounced spine which divides the posterior surface into a

supraspinous fossa & an infraspinous fossa

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Structures of the Scapula

Structures of the Scapula

Figure 8.2c

The Upper Limb

30 bones form each upper limbGrouped into bones of the:

ArmForearmHand

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Arm

Region of the upper limb between the shoulder and elbowHumerus – the only bone of the arm

Longest and strongest bone of the upper limbArticulates with the scapula at the shoulderArticulates with the radius and ulna at the elbow

Structures of the Humerus of the Right Arm

Forearm

Formed from the radius and ulnaProximal ends articulate with the humerusDistal ends articulate with carpalsRadius and ulna articulate with each other

At the proximal and distal radioulnar joints

Interconnected by a ligament – the interosseous membraneIn anatomical position, the radius is lateral and the ulna is medial

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Details of Arm and Forearm

Figure 8.5a

Ulna

Main bone responsible for forming the elbow joint with the humerusHinge joint allows forearm to bend on armDistal end is separated from carpals by fibrocartilagePlays little to no role in hand movement

Radius

Superior surface of the head of the radius articulates with the capitulum Medially – the head of the radius articulates with the radial notch of the ulnaContributes heavily to the wrist joint

Distal radius articulates with carpal bones When radius moves, the hand moves with it

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Radius and Ulna

Figure 8.4a-c

Hand

Includes the following bonesCarpus – wrist Metacarpals – palm Phalanges – fingers

Carpus

Forms the true wrist – the proximal region of the handGliding movements occur between carpalsComposed of eight marble-sized bones

Carpal bones arranged in two irregular rowsProximal row from lateral to medial

Scaphoid, lunate, triquetral (triquetrium), and pisiformDistal row from lateral to medial

Trapezium, trapezoid, capitate, and hamateAcronym: SLTPTTCH (Some Lovers Try Positions That They Can’t Handle)

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Bones of the Hand

Metacarpals & Phalanges

Five metacarpals radiate distally from the wristMetacarpals form the palm

Numbered 1–5, beginning with the pollex (thumb)Articulate proximally with the distal row of carpalsArticulate distally with the proximal phalanges

PhalangesNumbered 1–5, beginning with the pollex (thumb)

Except for the thumb, each finger has three phalangesProximal, middle, and distal

Pelvic GirdleAttaches lower limbs to the spineSupports visceral organsAttaches to the axial skeleton by strong ligaments Acetabulum is a deep cup that holds the head of the femur

Lower limbs have less freedom of movement Are more stable than the arm

Consists of paired hip bones (coxal bones)Hip bones unite anteriorly with each otherArticulates posteriorly with the sacrum

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Bony Pelvis

A deep, basin-like structureFormed by coxal bones, sacrum, and coccyx

Coxal Bones

Consist of three separate bones in childhoodIlium, ischium, and pubis

Bones fuse – retain separate names to regions of the coxal bonesAcetabulum – deep hemispherical socket on lateral pelvic surface

Lateral and Medial Views of the Hip Bone

Figure 8.7b, c

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True and False Pelves

Bony pelvis is divided into two regionsFalse (greater) pelvis – bounded by alae of the iliac bonesTrue (lesser) pelvis –inferior to pelvic brim

Forms a bowl containing the pelvic organs

Female & Male Pelvis

Major differences between the male and female pelvisFemale pelvis is adapted for childbearing

Pelvis is lighter, wider, and shallower than in the maleProvides more room in the true pelvis

Male pelvis is adapted for heavy load handlingAcetabulum are larger and widerCoxae bones are thicker

ShapeFemale pelvis is tilted forward to a greater degree than the male pelvisFemale pelvis has a round pelvic inlet, while the male pelvic inlet is more heartshaped

Female and Male Pelves

Table 8.2

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Female and Male Pelves

The Lower Limb

Carries the entire weight of the erect bodyBones of lower limb are thicker and stronger than those of upper limbDivided into three segments

Thigh - femurLeg – tibia & fibulaFoot – tarsals, metatarsals, phalanges

Thigh

The region of the lower limb between the hip and the kneeFemur – the single bone of the thigh

Longest and strongest bone of the bodyBall-shaped head articulates with the acetabulum

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Patella

Triangular sesamoid boneImbedded in the tendon that secures the quadriceps musclesProtects the knee anteriorlyImproves leverage of the thigh muscles across the knee

LegRefers to the region of the lower limb between the knee and the ankleComposed of the tibia and fibula

Tibia – more massive – medial bone of the leg

Receives weight of the body from the femur

Fibula – stick-like – lateral bone of the leg

Stabilizes the legInterosseous membrane –connects the tibia and fibula

The Foot

Foot is composed of:Tarsus, metatarsus, and the phalanges

Important functionsSupports body weightActs as a lever to propel body forward when walkingSegmentation makes foot pliable and adapted to uneven ground

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Tarsus

Makes up the posterior half of the footContains seven bones called tarsals

Talus, Calcaneous, Navicular, Cuboid, First, Second and Third CuneiformAcronym: TCNCCCC

The Crazy Nurse Can’t Count Children Correctly

Body weight is primarily borne by the talus and calcaneus

Metatarsus & Phalanges

Consists of five small long bones called metatarsalsNumbered 1–5 beginning with the hallux (great toe)First metatarsal supports body weight14 phalanges of the toes

Smaller and less nimble than those of the fingersStructure and arrangement are similar to phalanges of fingersExcept for the great toe, each toe has three phalanges

Proximal, middle, and distal

Arches of the Foot

Foot has three important arches

Medial and lateral longitudinal archTransverse arch

Arches are maintained by: Interlocking shapes of tarsalsLigaments and tendons

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Disorders of the Appendicular Skeleton

Bone fracturesBone spursHip dysplasia – head of the femur slips out of acetabulumClubfoot – soles of the feet turn medially