Copyright © 2010 Pearson Education, Inc. Chapter 7 The Skeleton Part C Shilla Chakrabarty, Ph.D.

Copyright © 2010 Pearson Education, Inc.

Chapter 7

The Skeleton

Part C

Shilla Chakrabarty, Ph.D.


Appendicular Skeleton

Comprised of bones of the limbs and their girdles

• Pectoral girdle consists of clavicle and scapula, and attaches upper limbs to body trunk

Very light and designed to provide great mobility to upper limbs

Only clavicle attaches to axial skeleton; scapula moves freely across thorax, allowing arm to move with it

Socket of pectoral girdle is shallow and poorly reinforced, allowing free movement of humerus

• Pelvic girdle, formed by a pair of hip bones, is sturdy and secures the lower limbs


ClavicleAcromio-clavicularjoint

Scapula

(a)Articulated pectoral girdle

Pectoral Girdle (Shoulder Girdle)

• Formed by clavicles anteriorly and scapulae posteriorly

• Medial end of each clavicle joins sternum anteriorly

• Distal end of each clavicle meets scapula laterally

• Medial borders of scapulae do not join each other or the axial skeleton

• Scapulae attached to thorax and vertebral column only by muscles

• Functions:

Attach upper limbs to axial skeleton

Provide attachment sites for muscles that move upper limbs


Acromial (lateral)end

(b)Right clavicle, superior view

Posterior

Sternal (medial)end

Anterior

Clavicles (Collarbones)• Slender, doubly curved bones, extend horizontally

across superior thorax

• Medial two thirds convex anteriorly; lateral third concave anteriorly

• Flattened acromial (lateral) end articulates with scapula

• Cone-shaped sternal (medial) end articulates with the sternum

• Superior surface smooth; inferior surface ridged and grooved for attachment of ligaments and muscles

• Act as braces to hold scapulae and arms out laterally

• Transmit compression forces from upper limbs to axial skeleton

• Exceptionally sensitive to muscle pull

• Not very strong and easy to fracture

NOTE: Fracture is usually anterior (outward), thus protecting the subclavian artery that serves the upper limb


Acromion

Coracoidprocess

Suprascapular notchSuperior border

Superiorangle

SubscapularfossaMedial border

Inferior angle

Glenoidcavity

Lateral border

(a) Right scapula, anterior aspect

Superiorangle

Medial border

Coracoid processSuprascapular notch

Acromion

Glenoidcavityat lateralangle

Lateral border

Infraspinousfossa

Spine

(b) Right scapula, posterior aspect

Supraspinousfossa

Scapulae (Shoulder Blades)• Situated on dorsal surface of rib cage, between

ribs 2 and 7

• Thin, triangular, flat bones with three borders and three angles

Superior border: shortest, sharpest

Medial border: parallels vertebral column

Lateral border: thick, abuts the armpit and ends superiorly in a small, shallow fossa, the glenoid cavity

Inferior angle moves extensively as arm is raised or lowered

• Anterior surface concave, posterior surface bears a prominent spine

Spine ends laterally in large, roughened triangular projection, the acromion

Acromion articulates with acromial end of clavicle to form acromioclavicular joint

• Coracoid process projects anteriorly from superior scapular border

• anchors biceps muscles

• bounded by suprascapular notch medially and glenoid cavity laterally

• Several large fossae, named according to location, house muscles

Copyright © 2010 Pearson Education, Inc. Figure 7.25c

Coracoidprocess

Glenoidcavity

Acromion

Infraspinousfossa

Spine

(c) Right scapula, lateral aspect

Infraglenoidtubercle

Supraglenoidtubercle

Supraspinous fossa

Subscapularfossa

Inferior angle

Supraspinousfossa

Infraspinousfossa

Subscapularfossa

Posterior Anterior


The Upper Limb

30 bones form skeletal framework of each upper limb

• Arm : Humerus

• Forearm: Radius and ulna

• Hand:

8 carpal bones in the wrist

5 metacarpal bones in the palm

14 phalanges in the fingers


Humerus

• Largest, longest bone of upper limb

• Articulates superiorly with glenoid cavity of scapula

• Articulates inferiorly with radius and ulna


GreatertubercleLessertubercleInter-tubercularsulcus

Lateralsupracondylarridge

Radialfossa

Capitulum

Head ofhumerusAnatomicalneck

Deltoidtuberosity

CoronoidfossaMedialepicondyleTrochlea

(a) Anterior view

Humerus• Largest, longest bone of upper limb

• Articulates superiorly with glenoid cavity of scapula, and inferiorly with radius and ulna

• Smooth, hemispheric head fits into glenoid cavity of scapula, allowing arm to hang freely on the side

• Slight constriction immediately inferior to head is the anatomical neck

• Lateral greater tubercle and medial lesser tubercle, separated by inter-tubercular sulcus are sites of attachment for rotator cuff muscles

• Inter-tubercular sulcus guides tendon of biceps muscle to its attachment point at rim of glenoid cavity

• Surgical neck distal to tubercles is most frequently fractured part of humerus

• V-shaped deltoid tuberosity in middle of shaft is attachment site for deltoid muscle of shoulder

• Distal end has two condyles : medial trochlea (for articulation with ulna) and lateral capitulum (for articulation with radius)

• The condyle pair is flanked by epicondyles to which muscles attach

• Ulnar nerve runs behind medial epicondyle and causes painful, tingling sensation when funny bone is hit

• Anterior coronoid fossa and posterior olecranon fossa allow corresponding process of ulna to move freely when elbow is flexed and extended.

• Small radial fossa, lateral to coronoid fossa, receives head of radius when elbow is flexed


Radialnotch ofthe ulna

OlecranonprocessTrochlearnotchCoronoidprocess Proximalradioulnarjoint

Distal radioulnarjoint

Styloid processof radius

Radius

Neck ofradius

Head ofradius

Ulnar notchof the radiusHead of ulna

Styloidprocess of ulna

Interosseousmembrane

Ulna

Head

Neck

Radialtuberosity

Radius

Styloidprocessof radius

(a) Anterior view (b) Posterior view

Bones of Forearm (Antebrachium)• Proximal ends of radius and ulna articulate with humerus; distal ends

form joints with bones of the wrist

• Radius (lateral) and ulna (medial) articulate with each other proximally and distally at radio-ulnar joints

• Radius and ulna connected along their entire length by flat flexible ligament, the interosseus membrane

Ulna

• Medial bone in forearm, slightly longer than radius

• Cup-shaped proximal end bears the olecranon (elbow) and coronoid processes, separated by the trochanter notch

• Forms the major portion of the elbow joint with humerus

• Distally, ulnar shaft narrows and ends in a knob-like head

• Medial to head is a styloid process from which a ligament runs to the wrist

• Ulnar head separated from bones of wrist by a disc of fibrocartilage which plays little or no role in hand movement

Radius

• Lateral bone in forearm, thin at proximal end and wide distally

• Head (flat and shaped like a nail head) articulates with capitulum of humerus and with radial notch of ulna

• Rough radial tuberosity inferior to head anchors biceps muscle of the arm

• Medial ulnar notch articulates with ulna; lateral styloid process anchors ligaments that run to the wrist.

• Interosseous membrane connects the radius and ulna along their entire length

• Major forearm bone contributing to wrist joint


(c) Proximal portion of ulna, lateral view

Olecranon process

Trochlear notch

Coronoid process

Radial notch

View

(d) Distal ends of the radius and ulna at the wrist

Ulnar notch of radius

Headof ulna

Styloidprocess

Articulationfor scaphoid

Articulationfor lunate

Styloidprocess

View

Coronoidfossa

Radius

Radialtuberosity

Head ofradius

Capitulum

Trochlea

(c) Anterior view at the elbow region

Humerus

Medialepicondyle

Coronoidprocess of ulna

UlnaRadial notch

Olecranonfossa

Ulna

Olecranonprocess

Medialepicondyle

(d) Posterior view of extended elbow

Humerus

Lateralepicondyle

Head

RadiusNeck


Hand: CarpusConsists of eight bones in two

rows closely united by ligaments

Proximal row

• Scaphoid, lunate, triquetrum, and pisiform proximally

Distal row

• Trapezium, trapezoid, capitate, and hamate distally

Only scaphoid and lunate articulate with radius to form wrist joint

Overuse and inflammation of tendons in this region causes carpal tunnel syndrome


Hand: Metacarpus and Phalanges

Metacarpus

• Five metacarpal bones (#1 to #5) form the palm

Phalanges

• Each finger (digit), except the thumb, has three phalanges—distal, middle, and proximal

• Fingers are numbered 1–5, beginning with the thumb (pollex)

• Bases of metacarpals articulate with carpals proximally; bulbous heads articulate with proximal phalanges of fingers

• Thumb has no middle phalanx

Copyright © 2010 Pearson Education, Inc. Figure 7.28a-b

• Trapezoid• Trapezium

• Scaphoid

Phalanges

Carpals

Radius

• Proximal• Middle• Distal

• Triquetrum• Lunate

• Capitate• Hamate

• Pisiform

Metacarpals

Carpals

(b) Posterior view of left hand

Ulna

• Base• Shaft• Head

• Trapezoid• Trapezium

• Scaphoid

Carpals

(a) Anterior view of left hand

Radius

Sesamoidbones


Pelvic (Hip) Girdle

• Two hip bones (each also called coxal bone or os coxae)

• Attach lower limbs to axial skeleton with strong ligaments

• Transmit weight of upper body to lower limbs

• Support visceral organs of pelvis

• Secured to axial skeleton by very strong ligaments

• Unlike shallow glenoid cavity of scapula, sockets of pelvic girdle are deep and cuplike to firmly secure head of femur in place

• Lacks mobility of pectoral girdle, but is far more stable


Coxalbone(os coxaeor hip bone)

llium

Sacroiliacjoint

Iliac fossa

Pubicbone

Ischium

Sacrum

Base of sacrum

Sacralpromontory

Pelvic brim

Acetabulum

Pubic crestPubic symphysis

Iliac crest

Coccyx

Pubic arch

Anterior inferioriliac spine

Anteriorsuperior iliac spine

Pubic tubercle

Pelvic (Hip) Girdle• Each hip bone consists of three fused bones: ilium, ischium, and pubis

• Together with the sacrum and the coccyx, these bones form the bony pelvis

• Deep hemispherical socket on lateral surface of pelvis is acetabulum, and receives head of femur at hip joint


Hip Bone

• Three regions

1. Ilium

• Superior region of the coxal bone

• Auricular surface articulates with the sacrum (sacroiliac joint)

2. Ischium

• Posteroinferior part of hip bone

3. Pubis

• Anterior portion of hip bone

• Midline pubic symphysis joint

IliumAla

Anterior gluteallinePosterior gluteal linePosteriorsuperioriIiac spine

Greater sciaticnotch

Posterior inferioriliac spine

Ischial bodyIschial spineLesser sciatic notch

Ischialtuberosity

Ischium

Ischial ramus Obturator foramen

Inferiorgluteal line

Acetabulum

Pubic body

Iliac crest

Anteriorsuperioriliac spine

Anterior inferioriliac spine

Pubis

Inferior ramusof pubis

(a) Lateral view, right hip bone


Comparison of Male and Female Pelves

• Female pelvis

• Adapted for childbearing

• True pelvis (inferior to pelvic brim) defines birth canal

• Cavity of the true pelvis is broad, shallow, and has greater capacity

• Male pelvis

• Tilted less forward

• Adapted for support of male’s heavier build and stronger muscles

• Cavity of true pelvis is narrow and deep


Comparison of Male and Female Pelves

Characteristic Female Male

Bone thickness Lighter, thinner, and smoother

Heavier, thicker, and more prominent markings

Pubic arch/angle 80˚– 90˚ 50˚– 60˚

Acetabula Small; farther apart Large; closer together

Sacrum Wider, shorter; sacral curvature is accentuated

Narrow, longer; sacral promontory more ventral

Coccyx More movable; straighter Less movable; curves ventrally


The Lower Limb

• Carries the weight of the body

• Subjected to exceptional forces

• Three segments of the lower limb

• Thigh: femur

• Leg: tibia and fibula

• Foot: 7 tarsal bones in the ankle, 5 metatarsal bones in the metatarsus, and 14 phalanges in the toes


Neck Foveacapitis

Greatertrochanter

Inter-trochantericcrest

Head

Intertrochantericline

Lesser trochanter

Gluteal tuberosity

Linea aspera

Lateralcondyle

LateralepicondyleIntercondylar fossa

Medial andlateral supra-condylar lines

Medial condyle

Medialepicondyle

Adductortubercle

Anterior view Posterior view(b) Femur (thigh bone)

Lateral epicondyle

Patellar surface

Posterior

Facet formedialcondyleof femur

Facet for lateralcondyle of femur

Surface forpatellarligament

ApexAnterior

(a) Patella (kneecap)

Femur: Longest And Strongest Bone In The Body• Articulates proximally with acetabulum, and posteriorly with tibia and patella


Medial condyle

Articular surface

Tibial tuberosity

Interosseous membrane

Anterior border

Tibia

Medial malleolus

Intercondylar eminence

Proximal tibiofibularjoint

Distal tibiofibularjoint

Lateral malleolus

Lateral condyle

Fibula

Head

(a) Anterior view

Bones of the Leg

Tibia

• Medial leg bone

• Receives the weight of the body from the femur and transmits it to the foot

Fibula

• Not weight bearing; no articulation with femur

• Site of muscle attachment

• Connected to tibia by interosseous membrane

• Articulates with tibia via proximal and distal tibiofibular joints


Medial condyle

Articular surface oflateral condyle

Articular surfaceof medial condyle

Articular surface

Interosseousmembrane

Tibia Fibula

Head of fibula

Medial malleolusLateral malleolus

(b) Posterior view

Bones of the Leg


FootTarsals

•Seven tarsal bones form the posterior half of the foot

•Talus transfers most of the weight from the tibia to the calcaneus

•Other tarsal bones: cuboid, navicular, and the medial, intermediate, and lateral cuneiforms

Metatarsals

• Five metatarsal bones (#1 to #5)

• Enlarged head of metatarsal 1 forms the “ball of the foot”

Phalanges

• The 14 bones of the toes

• Each digit (except the hallux) has three phalanges

• Hallux has no middle phalanx

Medialcuneiform

Phalanges

Metatarsals

TarsalsNavicular

Intermediatecuneiform

Talus

Calcaneus(a) Superior view

Cuboid

Lateralcuneiform

Proximal

54321

MiddleDistal

Trochleaof talus


Facet formedialmalleolus

Calcanealtuberosity(b) Medial view

Intermediatecuneiform Sustentac-

ulum tali(talar shelf)

Talus

Navicular

First metatarsal

Medialcuneiform

Calcaneus

Foot


Arches of the Foot

• Arches are maintained by interlocking foot bones, ligaments, and tendons

• Arches allow the foot to bear weight

• Three arches

• Lateral longitudinal

• Medial longitudinal

• Transverse


Medial longitudinalarch

Transverse arch

Laterallongitudinal arch

(a) Lateral aspect of right foot

Arches of the Foot• Arches are maintained by interlocking foot bones, ligaments, and tendons

• Arches allow the foot to bear weight

• Three arches

Lateral longitudinal

Medial longitudinal

Transverse


Developmental Aspects: Fetal Skull

• Infant skull has more bones than the adult skull

• Skull bones such as the mandible and frontal bones are unfused

• At birth, skull bones are connected by fontanelles

• Fontanelles: Unossified remnants of fibrous membranes between fetal skull bones

Four fontanelles :

Anterior, posterior, mastoid, and sphenoid

Copyright © 2010 Pearson Education, Inc. Figure 7.35

Frontal bone

Ossificationcenter

Occipital bone(a) Superior view

Posterior fontanelle

Parietal bone

Anteriorfontanelle

Frontal suture

(b) Lateral view

Posteriorfontanelle Mastoidfontanelle

Parietal bone

Ossificationcenter

Occipital bone

Temporal bone(squamous portion)

Frontal bone

Sphenoidalfontanelle


Developmental Aspects: Growth Rates

• At birth, the cranium is huge relative to the face

• At 9 months of age, cranium is ½ adult size

• Mandible and maxilla are foreshortened but lengthen with age

• The arms and legs grow at a faster rate than the head and trunk, leading to adult proportions


Developmental Aspects: Spinal Curvature

• Thoracic and sacral curvatures are obvious at birth

These primary curvatures give the spine a C shape

Convex posteriorly


Developmental Aspects: Spinal Curvature

• Secondary curvatures

Cervical and lumbar—convex anteriorly

Appear as child develops (e.g., lifts head, learns to walk)


Developmental Aspects: Old Age

• Intervertebral discs become thin, less hydrated, and less elastic

• Risk of disc herniation increases

• Loss of stature by several centimeters is common by age 55

• Costal cartilages ossify, causing the thorax to become rigid

• All bones lose mass

Copyright © 2010 Pearson Education, Inc. Chapter 7 The Skeleton Part C Shilla Chakrabarty, Ph.D.

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