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 1 Head

 2 Articular facets of head

 3 Crest of head

 4 Neck

 5 Body or shaft

 6 Tubercle

 7 Articular facet of tubercle

 8 Angle

 9 Costal groove

10 Crest of body

 11 Scalene tubercle (first rib)

12 Tuberosity of serratus anterior (second rib)

13 Costal cartilage

14 True ribs [I-VII]

15 False ribs [VII-XII]

16 Floating ribs [XI-XII]

Left ribs 1 through 12

Superior view, first rib at top, posterior to right

Rib cage

Anterior view

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body, and a sharp point-like apex named the xiphoid process. A distinct angle forms at the junction of the

manubrium and the body. This angle is called the sternal angle. A horizontal plane extended posteriorly

intersects the disc between the fourth and fi fth thoracic vertebrae and marks the top of the heart in the thoracic

cavity. The lateral margins of the bone are notched for reception of the costal cartilages and clavicles. Its

anterior surface is slightly convex, while the posterior surface is weakly concave. The sternum articulates

with sixteen bones, more articulations than any other bone in the body.

The sternum is the anterior bone of the thoracic wall. It forms from six segmental

elements, or sternebrae, that fuse during development. The bone has the appearance of a sword with a wide handle called the manubrium, a tapering blade or

Sternum

 1 Manubrium

 2 Clavicular notch

 3 Jugular or suprasternal notch

 4 Sternal angle

 5 Body

 6 Xiphoid process

 7 Costal notches

Sternum

Anterior view, superior at top

Sternum

Lateral view, anterior at left

Sternum

Posterior view, superior at top

Sternum

Superior view, posterior at top

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Th e appendicular portion of the

skeleton forms the framework of the limbs. It includes the limb

girdles, or fi xed portion of the appendicular skeleton, and the

series of bones that extend distally from the girdles into the

limb proper, or free portion of the limb. Th e limb girdles,

pectoral and pelvic, help anchor the limb to the axial

skeleton. Th e free portion of each limb consists of a

large proximal element, the humerus and femur,

forming the skeleton of the arm and thigh, respectively. Next in sequence are the ulna and radius of the

forearm, and the fi bula and tibia of the leg. Th e distalmost regions of the limbs are the hand and foot consisting of the short carpal and tarsal bones, respectively,

along with the metacarpals, metatarsals, and phalanges of the digits.

As the tetrapod (land) vertebrates evolved, a

major diff erence emerged between the two

limbs. Th e anterior, or upper limb, evolved as

a steering device, while the posterior, or lower

limb, became the locomotor limb. Accompanying these evolutionary modifi cations in

limb function were important morphological

diff erences. Th e powerful locomotor hind limb

 developed strong attachments to the axial skeleton.

Th e strong iliosacral joint, with its accompanying

ligaments, transfers the powerful forces generated

by the posterior limb to the axial skeleton to propel the

body forward. On the other hand, the anterior limb developed

minimal, weak skeletal attachments between the girdle and axial

skeleton while becoming a more mobile limb.

As you study the skeleton of the limbs in the photos that follow, note the

similarities and diff erences that exist between the bones of the superior and

inferior limb skeletons and think about the functional diff erences mentioned above.

Find more information

about the appendicular

skeleton in

6 Appendicular Skeleton

83

REAL ANATOMY

84

anchored to the axial skeleton by muscles rather than ligaments. The free part of the upper limb consists of

the humerus, radius, ulna, and hand. The humerus forms the skeletal framework for the brachium. Distal to

the brachium is the antebrachium containing the radius and ulna. The distal-most region of the superior limb

is the hand consisting of a wrist region of eight carpal bones, the palm region consisting of fi ve metacarpal

bones, and the fourteen phalanges of the fi ngers and thumb.

Each superior limb consists of 32 bones. The proximal end of the superior limb, the clavicle and scapula, form the pectoral or shoulder girdle.

This girdle of bones provides a broad base of support that is primarily

Upper Limb

Left upper limb

Anterior view Left upper limb

Posterior view

 1 Scapula

 2 Clavicle

 3 Humerus

 4 Ulna

 5 Radius

 6 Carpals

 7 Metacarpals

 8 Phalanges

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of the axial skeleton. The large triangular scapula presents an extensive surface area for muscle attachment

and a large lateral fossa that articulates with the humerus of the free part of the upper limb. Except for the weak

joint formed between the clavicle and the sternum, the pectoral girdle is essentially unattached by ligaments or

joints to the axial skeleton. This was paramount in the evolutionary role of this limb as a steering device and

shock absorber during locomotion.

The pectoral, or shoulder, girdle consisting of the scapula and the

clavicle forms the base of the upper limb skeleton. The rod-like

clavicle forms a horizontal strut that links the scapula to the sternum

Pectoral Girdle

 1 Scapula

 2 Clavicle

Left pectoral girdle

Superior view

Left pectoral girdle

Lateral view

1

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86

lateral or acromial end is concave anteriorly. This is one of the more variable bones of the skeleton. It is

typically smooth and straight in females and rougher and more curved in males. The bone forms the ventral

strut of the pectoral girdle that props the shoulder joint away from the rib cage. It is subcutaneous and easily

palpable throughout its length. This combination of features makes it susceptible to fracture from falls onto

the limb. The clavicle articulates with the three bones — the scapula, sternum, and fi rst rib.

The clavicle has an S-shaped appearance that can range from an almost straight,

shallow S-curve shape to a deeper, more prominent S-curve shape. The curve at

the medial or sternal end of the bone is concave posteriorly, while the curve at the

Clavicle

 1 Sternal end

 2 Sternal facet

 3 Impression for costoclavicular ligament

 4 Shaft or body

 5 Subclavian groove

 6 Acromial end

 7 Acromial facet

 8 Tuberosity for coracoclavicular ligament

 9 Conoid tubercle

10 Trapezoid line

Left clavicle

Superior view, lateral to right

Left clavicle

Inferior view, lateral to right

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1

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Left clavicle

Anterior view, lateral to right

Left clavicle

Posterior view, lateral to left

Left clavicle

Lateral view, anterior to left Left clavicle

Medial view, anterior to right

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ferior, and lateral) and is typically a very thin plate of bone. Its lateral angle is conspicuous as it forms the glenoid fossa, or shoulder socket that articulates with the head of the humerus. Its three prominent projections are

the anterior projecting coracoid process, the posterior projecting ridge called the spine, and the fl at laterally

projecting acromion, which forms the lateral expansion of the spine. The scapula articulates with two bones — the

clavicle and the humerus.

The scapula is a fl at, triangular bone with three prominent projections. The fl attened

triangular portion of the bone, the body, spans from the second to the seventh rib and

consists of three borders (superior, lateral, and medial) and three angles (superior, inScapula

 1 Subscapular fossa

 2 Spine

 3 Deltoid tubercle

 4 Supraspinous fossa

 5 Infraspinous fossa

 6 Acromion

 7 Clavicular facet

 8 Acromial angle

 9 Medial border

10 Lateral border

Left scapula

Anterior view, lateral to right Left scapula

Lateral view, anterior to right

 11 Superior border

12 Suprascapular notch

13 Inferior angle

14 Superior angle

15 Glenoid cavity

16 Supraglenoid tubercle

17 Infraglenoid tubercle

18 Neck

19 Coracoid process

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Left scapula

Superior view, lateral to left

Left scapula

Posterior view, Lateral to left

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anterior to posterior. The ends consist of a spongy core of bone covered with a thin lamina of compact bone.

The shaft is a cylinder of thick compact bone surrounding a large medullary cavity. The humerus articulates

with three bones — the scapula, ulna, and radius.

The humerus is the skeletal element of the brachium and it is the largest bone of

the upper limb. It has a long cylindrical shaft that expands at the proximal and

distal ends. The proximal end is rounded, while the distal end is fl attened from

Humerus

 1 Head

 2 Anatomical neck

 3 Surgical neck

 4 Greater tubercle

 5 Lesser tubercle

 6 Intertubercular sulcus or groove

 7 Crest of greater tubercle

 8 Crest of lesser tubercle

 9 Shaft or body

10 Groove for radial nerve

 11 Medial supracondylar ridge

12 Deltoid tuberosity

13 Capitulum

14 Trochlea

15 Olecranon fossa

16 Coronoid fossa

17 Radial fossa

18 Medial epicondyle

19 Groove for ulnar nerve

20 Lateral epicondyle

Left humerus

Anterior view, lateral to right

Left humerus

Posterior view, lateral to left

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Left humerus

Lateral view, anterior to left

Left humerus

Medial view, anterior to right

Left humerus

Superior view, lateral to left

Left humerus

Inferior view, lateral to right

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The ulna is the medial and longer bone of the antebrachium. It is thick and notched at its proximal end where it is a major contributor to the elbow joint. From the notched proximal end it

tapers to a thin shaft that ends distally as a small rounded head. The ulna articulates with two

bones— the humerus and the radius.

Ulna

 1 Olecranon

 2 Coronoid process

 3 Ulnar tuberosity

 4 Radial notch

 5 Trochlear notch

 6 Shaft or body

 7 Interosseous border

 8 Anterior border

 9 Posterior border

10 Supinator crest

 11 Head

12 Articular circumference

13 Ulnar styloid process

Left ulna

Posterior view, lateral to left

Left ulna

Anterior view, lateral to right

1

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Left ulna

Lateral view, anterior to left

Left ulna

Medial view, anterior to right

Left ulna

Superior view, lateral to left

Left ulna

Inferior view, lateral to right

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bone. The distal end is concave anteriorly and convex and grooved posteriorly. The ridge-like borders of the

shaft give it a triangular shape in cross section. The radius articulates with four bones — the humerus, ulna,

scaphoid, and lunate.

The radius is the lateral, slender, rod-like bone of the antebrachium. The rod-like shaft

expands at both ends. The proximal end forms a wheel-like head with a proximal concavity, while the distal end expands from medial to lateral to form the widest part of the

Radius

 1 Head

 2 Articular facet

 3 Articular circumference

 4 Neck

 5 Shaft or body

 6 Radial tuberosity

 7 Pronator tuberosity

 8 Interosseous border

 9 Anterior border

10 Posterior border

 11 Radial styloid process

12 Suprastyloid crest

13 Dorsal tubercle

14 Groove for extensor muscle tendons

15 Ulnar notch

16 Carpal articular surface

Left radius

Anterior view, lateral to right

Left radius

Posterior view, lateral to left

3

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Left radius

Lateral view, anterior to left

Left radius

Medial view, anterior to right

Left radius

Superior view, lateral to left

Left radius

Inferior view, lateral to right

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and a proximal row. Distal to the carpus are the fi ve digital rays. Each digit, called a fi nger of which there are

four, consists of a metatarsal bone and three phalanges. The remaining digit, the thumb or pollex, has a metatarsal bone and only two phalanges. The photos of the hands below and on the opposing page are positioned

as if you were looking at your own hand.

The hand is a composite structure consisting of 27 bones. The proximal end of the hand is the carpus or wrist. The carpal bones are

eight in number and are arranged in two rows of four, a distal row

Hand Skeleton

Left hand

Anterior view, lateral to left

1 2

3

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6 7

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97

 1 Scaphoid

 2 Lunate

 3 Triquetrum

 4 Pisiform

 5 Trapezium

 6 Trapezoid

 7 Capitate

 8 Hamate

 9 Metacarpal I

10 Metacarpal II

 11 Metacarpal III

12 Metacarpal IV

13 Metacarpal V

14 Proximal phalanx

15 Middle phalanx

16 Distal phalanx

Left hand

Posterior view, lateral to right

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Carpal Bones The eight carpal bones form the proximal end

of the hand skeleton. The main features of this

complex little series of bones are the numerLeft trapezium

Anterior view, lateral to left

Left trapezoid

Anterior view, lateral to left

Left capitate

Anterior view, lateral to left

Left hamate

Anterior view, lateral to left

Left scaphoid

Anterior view, lateral to left

Left pisiform

Anterior view, lateral to left Left triquetrum

Anterior view, lateral to left

Left lunate

Anterior view, lateral to left

ous articular surfaces they form with one another and with the metacarpal and antebrachial bones. The carpal bones form two rows of four bones each. The two largest

bones of the proximal row, the scaphoid and the lunate, articulate with the distal end

of the radius. The row of distal bones form the skeletal foundation for the fi ngers and

articulate with the metacarpal bones of the fi ngers and thumb. The anterior surface of

the carpal bones forms the fl oor of the carpal tunnel that supports the major digital

fl exor tendons that enter the hand.

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27

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Trapezium

 1 Tubercle of trapezium

 2 Articular surface with scaphoid

 3 Articular surface with trapezoid

 4 Articular surface with first metacarpal

 5 Articular surface with second metacarpal

Trapezoid

 6 Articular surface with scaphoid

 7 Articular surface with trapezium

 8 Articular surface with capitate

 9 Articular surface with first metacarpal

Capitate

10 Articular surface with scaphoid

 11 Articular surface with lunate

12 Articular surface with trapezoid

13 Articular surface with hamate

14 Articular surface with second metacarpal

15 Articular surface with third metacarpal

16 Articular surface with fourth metacarpal

Hamate

17 Hook of hamate or hamulus

18 Articular surface with lunate

19 Articular surface with triquetrum

20 Articular surface with fourth metacarpal

21 Articular surface with fifth metacarpal

Scaphoid

22 Scaphoid tubercle

23 Articular surface with radius

24 Articular surface with trapezium

25 Articular surface with trapezoid

26 Articular surface with capitate

27 Articular surface with lunate

Lunate

28 Articular surface with radius

29 Articular surface with scaphoid

30 Articular surface with capitate

31 Articular surface with hamate

32 Articular surface with triquetrum

Triquetrum

33 Articular surface with lunate

34 Articular surface with pisiform

35 Articular surface with hamate

Pisiform

36 Articular surface with triquetrum

Left trapezium

Posterior view, lateral to right

Left trapezoid

Posterior view, lateral to right Left capitate

Posterior view, lateral to right

Left hamate

Posterior view, lateral to right

Left scaphoid

Posterior view, lateral to right

Left lunate

Posterior view, lateral to right Left triquetrum

Posterior view, lateral to right

Left pisiform

Posterior view, lateral to right

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24 25

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30 36

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100

The fi ve digital rays of the hand consist of a series of four bones, except in the thumb

where there are only three bones, that decrease in length from proximal to distal. Forming the skeleton of the palmar region of the hand are the stout metacarpal bones. Note

their saddle-like bases and rounded heads. The anterior-posterior fl attened phalanges

project into the proper portion of the fi ngers and thumb from the metacarpal bones.

Metacarpals and Phalanges

Left metacarpal bones, numbered I to V from lateral to medial

Anterior view, thumb to left

Left phalanges

Anterior view, thumb to left

1

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101

 1 Base of metacarpal

 2 Shaft or body of metacarpal

 3 Head of metacarpal

 4 Styloid process of third metacarpal

Left phalanges

Posterior view, thumb to right

 5 Base of phalanx

 6 Shaft or body of phalanx

 7 Head of phalanx

 8 Trochlea of phalanx

 9 Tuberosity of distal phalanx

Left metacarpal bones, numbered I to V from lateral to medial

Posterior view, thumb to right

1

1

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102

the most obvious are those that increase the diameter of the pelvic outlet. For example, note the wider pubic

angle (1) and greater sciatic notch (2) of the female pelvis.

The characteristic features of the female pelvis are related to the

role of the female pelvis in childbirth. While there are numerous diagnostic features that help distinguish a female pelvis, some of

Pelvis - Female

Female pelvis

Posterior view, superior to top

Female pelvis

Superior view, anterior to bottom

Female pelvis

Inferior view, anterior to bottom

Female pelvis

Lateral view, anterior to left

Female pelvis

Anterior view, superior to top

1

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103

The male pelvis tends to have a more narrow profi le than the pelvis of the female.

Compare the diameter of the outlet, the angle of the pubic arch, and the width of the

greater sciatic notch with those of the female pelvis. Also, note the stout, thick ishiopubic ramus (3) of the male compared to the slender ischiopubic ramus of the female

pelvis.

Pelvis - Male

Male pelvis

Anterior view, superior to top

Male pelvis

Posterior view, superior to top

Male pelvis

Superior view, anterior to bottom Male pelvis

Inferior view, anterior to bottom

Male pelvis

Lateral view, anterior to left

1

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104

hip bone. The os coxae is fi rmly anchored to the sacrum via strong ligaments and a synovial joint. Distal to

the girdle is the free part of the lower limb. The bony framework of the thigh is the femur with the sesamoid

patella at its distal end. Distal to the femur, the tibia and fi bula form the skeleton of the crus or leg. The distalmost region of the inferior limb is the foot consisting of seven tarsal bones, fi ve metatarsal bones, and fourteen phalanges.

Each inferior appendage consists of 31 bones. The broad base of

the inferior limb is the pelvic girdle. This girdle is the strong fusion of

three bones, the ilium, ischium, and pubis, to form the os coxae or

Inferior Limb

 1 Os coxae or hip bone

 2 Femur

 3 Patella

 4 Tibia

 5 Fibula

 6 Tarsal bones

 7 Metatarsal bones

 8 Phalanges

Left lower limb

Anterior view, lateral to right Left lower limb

Posterior view, lateral to left

1 1

2 2

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4 4

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6 7

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105

and transfers the forces of locomotion from the inferior limb to the vertebral column. Each os coxae articulates with

three bones — the femur, sacrum, and opposite os coxae. The photo on this page depicts the three bones of the os

coxae — the ilium (green), the ischium (blue), and the pubis (red). Landmarks that are shared by the bones are

depicted on this image. The following two pages show all the landmarks of the individual bones of the os coxae.

Each os coxae forms from three separate bony elements that fuse during development

at their site of union within the acetabulum. The three bony elements are the ilium, ischium, and pubis. This strong girdle of bone unites the inferior limb to the axial skeleton

Os Coxae

Left os coxae showing individual bones

Lateral view, anterior to left

 1 Acetabulum

 2 Acetabular notch

 3 Lunate surface

 4 Ischiopubic ramus

 5 Obturator foramen

 6 Greater sciatic notch

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106

Os Coxae Ilium

 1 Body of ilium

 2 Supra-acetabular groove

 3 Ala or wing

 4 Arcuate line

 5 Iliac crest

 6 Outer lip of crest

 7 Intermediate zone of crest

 8 Inner lip of crest

 9 Tuberculum of crest

10 Anterior superior iliac spine

 11 Anterior inferior iliac spine

12 Posterior superior iliac spine

13 Posterior inferior iliac spine

14 Iliac fossa

15 Anterior gluteal line

16 Posterior gluteal line

17 Inferior gluteal line

18 Auricular surface

19 Iliac tuberosity

Left os coxae

Anterior view, lateral to right

Left os coxae

Posterior view, lateral to right

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