7
The Skeleton: Part C
Appendicular Skeleton
• Bones of the limbs and their girdles
– Pectoral girdle attaches the upper limbs to the
body trunk
– Pelvic girdle secures the lower limbs
Pectoral Girdle (Shoulder Girdle)
• Very light and has a high degree of mobility due to the
openness of the shoulder joint and the free movement of
the scapula across the thorax
• Attaches the upper limbs to the axial skeleton
• Provides attachment sites for muscles that move the
upper limbs
• Consists of clavicles and the scapulae
– Clavicle: joins the sternum anteriorly
– Scapula: attached to the posterior thorax and vertebrae via
muscular attachments
PLAY
A&P Flix™: Bones of the pectoral girdle
Acromioclavicular
joint
Clavicle
Scapula
(a) Articulated pectoral girdle
Figure 7.24a
Clavicles (Collarbones)
• Extend horizontally across the thorax
• Flattened acromial (lateral) end articulates
with the scapula
• Cone-shaped sternal (medial) end articulates
with the sternum
• Act as braces to hold the scapulae and arms
out laterally
Sternal (medial)
end
Posterior
Anterior
Acromial (lateral)
end
(b) Right clavicle, superior view
Figure 7.24b
Scapulae
(Shoulder
Blades)
Thin, flat bones
•
• Articulating with the humerus via the glenoid
cavity and the clavicle via the acromion
• Situated on the dorsal surface of rib cage,
between ribs 2 and 7
• Flat and triangular, with three borders and
three angles
• Seven large fossae, named according to
location
Acromion
Suprascapular notch
Superior border
Coracoid
process
Glenoid
cavity
Lateral border
Superior
angle
Subscapular
fossa
Medial border
(a) Right scapula, anterior aspect
Inferior angle
Figure 7.25a
Suprascapular notch
Coracoid process
Superior
angle
Supraspinous
fossa
Spine
Infraspinous
fossa
Acromion
Glenoid
cavity
at lateral
angle
Medial border
Lateral border
(b) Right scapula, posterior aspect
Figure 7.25b
Acromion
Supraspinous fossa
Supraglenoid
tubercle
Coracoid
process
Supraspinous
fossa
Infraspinous
fossa
Posterior
Spine
Glenoid
cavity
Infraspinous
fossa
Infraglenoid
tubercle
Subscapular
fossa
Subscapular
fossa
Anterior
(c) Right scapula, lateral aspect
Inferior angle
Figure 7.25c
The Upper Limb
• 30 bones form the skeletal framework of each upper limb
– Arm
• Humerus
• Extends from shoulder to elbow
– Forearm
• Radius and ulna
• Between the elbow and wrist
– 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 at the shoulder
• Articulates inferiorly with radius and ulna at
the elbow
Greater
tubercle
Lesser
tubercle
Intertubercular
sulcus
Head of
humerus
Anatomical
neck
Deltoid
tuberosity
Lateral
supracondylar
ridge
Radial
fossa
Capitulum
(a) Anterior view
Coronoid
fossa
Medial
epicondyle
Trochlea
Figure 7.26a
Bones of the Forearm
• Ulna
– Medial bone in forearm
– Forms the major portion of the elbow joint with the humerus
– Articulates with the radius laterally at the proximal end
– Articulates with the bones of the wrist via a cartilage disc at the distal
end
• Radius
– Lateral bone in forearm
– Flattened radial head articulates with capitulum of humerus and with
radial notch of ulna (medially & proximally)
– articulates with the carpals of the wrist and the ulna medially at the
distal end
– Interosseous membrane connects the radius and ulna along their
entire length
Radial
notch of
the ulna
Head
Neck
Radial
tuberosity
Olecranon
process
Trochlear
notch
Coronoid
process
Proximal
radioulnar
joint
Interosseous
membrane
Ulna
Head of
radius
Neck of
radius
Radius
Ulnar notch
Radius
of the radius
Head of ulna
Styloid
Styloid
process of ulna
process
Distal radioulnar
Styloid process
of radius
joint
of radius
(a) Anterior view
(b) Posterior view
Figure 7.27a-b
Olecranon process
Trochlear notch
View
Coronoid process
Radial notch
(c) Proximal portion of ulna,
lateral view
Ulnar notch of radius
Articulation
for lunate
Articulation
for scaphoid
Styloid
process
View
Styloid
Head
of ulna process
(d) Distal ends of the radius and
ulna at the wrist
Figure 7.27c-d
Humerus
Capitulum
Coronoid
fossa
Medial
epicondyle
Trochlea
Coronoid
process of
ulna
Radial notch
Ulna
(c) Anterior view at the elbow region
Head of
radius
Radial
tuberosity
Radius
Humerus
Olecranon
process
Olecranon
fossa
Lateral
epicondyle
Medial
epicondyle
Head
Ulna
Neck
Radius
(d) Posterior view of extended elbow
Figure 7.26c-d
Hand:
(wrist)
• Eight short
bonesCarpus
in two irregular
rows (4
bones each)
– 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
Hand: Metacarpus and Phalanges
• Metacarpus (palm)
– Five small, long metacarpal bones (#1 to #5) form the palm
– articulates with the carpals proximally and the proximal
phalanges distally
• Phalanges
– 14 phalanges of the fingers
– Each finger (digit), except the thumb, has three
phalanges—distal, middle, and proximal
– Fingers are numbered 1–5, beginning with the thumb
(pollex)
– Thumb has no middle phalanx
Phalanges
• Distal
• Middle
• Proximal
Sesamoid
bones
Carpals
• Trapezium
• Trapezoid
• Scaphoid
Radius
(a) Anterior view of left hand
Metacarpals
• Head
• Shaft
• Base
Carpals
• Hamate
• Capitate
• Pisiform
• Triquetrum
• Lunate
Ulna
Carpals
• Trapezium
• Trapezoid
• Scaphoid
Radius
(b) Posterior view of left hand
Figure 7.28a-b
•
Pelvic
(Hip)
Girdle
Two hip bones (each also called coxal bone or
os coxae)
– Attach the lower limbs to the axial skeleton with
strong ligaments
– Transmit weight of upper body to lower limbs
– Support pelvic organs
• 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
Base of sacrum
Iliac fossa
Coxal
bone
llium
(os coxae
or hip
Pubic
bone)
bone
Iliac crest
Sacroiliac
joint
Anterior
superior
iliac spine
Sacral
promontory
Sacrum
Coccyx
Anterior inferior
iliac spine
Pelvic brim
Acetabulum
Pubic tubercle
Pubic crest
Pubic symphysis
Ischium
Pubic arch
PLAY
Animation: Rotatable pelvis
Figure 7.29
•
Three regions
Hip Bone
1. Ilium
• Superior region of the coxal bone
• Auricular surface articulates with the sacrum (sacroiliac
joint)
• Articulates with the ischium and pubis anteriorly
2. Ischium
• Posteroinferior part of hip bone (coxa)
3. Pubis
• Anterior portion of hip bone (coxae.)
• Joined by a fibrocartilage disc, forming the midline
pubic symphysis joint
Anterior gluteal
Ilium
line
Ala
Posterior
Iliac crest
gluteal line
Posterior
Anterior
superior
superior
iIiac spine
iliac spine
Posterior inferior
Inferior
iliac spine
gluteal line
Greater sciatic
Anterior inferior
notch
iliac spine
Ischial body
Acetabulum
Ischial spine
Pubic body
Lesser sciatic
notch
Pubis
Ischium
Inferior ramus
Ischial
of pubis
tuberosity
Obturator foramen
Ischial ramus
(a) Lateral view, right hip bone
Figure 7.30a
Ilium
Iliac crest
Iliac fossa
Posterior
superior
iliac spine
Posterior
inferior
iliac spine
Auricular
surface
Greater sciatic notch
Ischial spine
Lesser sciatic notch
Obturator
foramen
Ischium
Anterior
superior
iliac spine
Anterior inferior
Body of
iliac spine
the ilium
Arcuate line
Superior ramus
of pubis
Pubic tubercle
Articular surface
of pubis (at pubic
symphysis)
Ischial ramus
Inferior ramus
of pubis
(b) Medial view, right hip bone
Figure 7.30b
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
– tends to be wider, shallower, lighter, and rounder
than the male pelvis
Comparison of Male and Female
Pelves
• Male pelvis
– Tilted less forward
– Adapted for support of male’s heavier build and stronger
muscles
– Consists of
• False pelvis: part of the abdomen and helps support
the viscera
• True pelvis: completely surrounded by bone and
contains the pelvic organs; 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
Table 7.4
Table 7.4
Table 7.4
The Lower Limb
• Carries the weight of the body
• Subjected to exceptional forces
• Three segments of the lower limb
– Thigh: femur, hip to knee
– Leg: tibia and fibula, knee to ankle
– Foot: 7 tarsal bones in the ankle, 5 metatarsal
bones in the metatarsus, and 14 phalanges in the
toes
• Femur
Femur & Patella
– Largest and strongest bone in the body
– Articulates proximally with the acetabulum of the
hip via a ball-like head and distally with the tibia
and patella at the lateral and medial condyles
• Patella (kneecap)
– triangular sesamoid bone
– articulates with the femur at the patellar surface
Neck
Fovea
capitis
Greater
trochanter
Head
Intertrochanteric
crest
Lesser trochanter
Intertrochanteric
line
Gluteal tuberosity
Linea aspera
Apex
Anterior
Facet for
medial
condyle
of femur
Facet for lateral
condyle of femur
Lateral
condyle
Medial and
lateral supracondylar lines
Surface for
patellar
Posterior
ligament
(a) Patella (kneecap)
Intercondylar fossa
Lateral
epicondyle
Medial condyle
Adductor
tubercle
Medial
epicondyle
Lateral epicondyle
Patellar surface
Anterior view
Posterior view
(b) Femur (thigh bone)
Figure 7.31
Bones of the Leg
• Tibia
– Medial leg bone
– Receives the weight of the body from the femur and transmits it to the
foot
– Proximally: medial and lateral condyles articulate with the femur
– Distally: medial malleolus, an inferior projection on the medial aspect
articulates with the talus
• Fibula
– No articulation with femur
– Sticklike, non-weight-bearing bone
– Expanded ends that articulate proximally with the tibia via the head
and distally via the lateral malleolus with the lateral aspects of the
tibia (proximal and distal tibiofibular joints)
– Site of muscle attachment
– Connected to tibia by interosseous membrane
Lateral condyle
Intercondylar eminence
Head
Medial condyle
Proximal tibiofibular
joint
Tibial tuberosity
Interosseous membrane
Anterior border
Fibula
Tibia
Distal tibiofibular
joint
Articular surface
Lateral malleolus
Medial malleolus
(a) Anterior view
Figure 7.32a
Articular surface
of medial condyle
Articular surface of
lateral condyle
Medial condyle
Head of fibula
Interosseous
membrane
Tibia
Fibula
Articular surface
Medial malleolus
Lateral malleolus
(b) Posterior view
Figure 7.32b
Foot: Tarsals (Tarsus)
• 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
• Foot:
Metatarsals:
and Phalanges
– Five small, long metatarsal bones (#1 medial to #5
lateral)
– 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 (great toe) has no middle phalanx
Distal
Middle
Proximal
1
Medial
cuneiform
Intermediate
cuneiform
Navicular
Talus
Trochlea
of talus
(a) Superior view
2
3
4
5
Phalanges
Metatarsals
Lateral
cuneiform
Cuboid
Tarsals
Calcaneus
Figure 7.33a
Intermediate
cuneiform
First metatarsal
Talus Facet for
medial
Navicular
malleolus
Sustentaculum tali
(talar shelf)
Calcaneus
Medial
cuneiform
(b) Medial view
PLAY
Calcaneal
tuberosity
Animation: Rotatable bones of the foot
Figure 7.33b
Arches of the Foot
• Arches are maintained by interlocking foot
bones, ligaments, and tendons during muscle
activity
• Arches allow the foot to bear weight
• Three arches
– Lateral longitudinal
– Medial longitudinal
– Transverse
Medial longitudinal
arch
Transverse arch
Lateral
longitudinal arch
(a) Lateral aspect of right foot
Figure 7.34a
Fetal
Skull
•Developmental
Membrane bones ofAspects:
the skull begin
to ossify
late in the second month of development
• 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
Frontal bone
Ossification
center
Posterior fontanelle
(a) Superior view
Parietal bone
Ossification
center
Posterior
fontanelle
Mastoid
fontanelle
(b) Lateral view
Frontal suture
Anterior
fontanelle
Parietal bone
Occipital bone
Frontal bone
Sphenoidal
fontanelle
Temporal bone
(squamous portion)
Occipital bone
Figure 7.35
•
•
•
•
•
•
•
•
Developmental Aspects: Growth
At birth, the cranium is huge relative to the face, several bones are still
unfused, head and trunk areRates
roughly 1-1/2 times the length of the
lower limbs
At 9 months of age, cranium is ½ adult size (rapid brain growth)
By age 8–9, the cranium has reached almost adult proportions
Between ages 6–13, the jaws, cheekbones, and nose become more
prominent, due to expansion of the nose, paranasal sinuses, and
development of permanent teeth.
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
By age 10, the head and trunk are about the same length as the lower
limbs.
During puberty, the female pelvis widens and the male skeleton
becomes more robust.
Developmental Aspects: Spinal
Curvature
• Primary curvatures
– Thoracic and sacral curvatures
– Obvious at birth
– Give the spine a C shape
– Convex posteriorly
Figure 7.37
Developmental Aspects: Spinal
Curvature
• Secondary curvatures
– Cervical and lumbar—convex anteriorly
– Appear as child develops (e.g., lifts head, learns to
walk)
– Result from reshaping the intervertebral discs
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