Post on 01-Mar-2021
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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