7-1

The Skeletal System

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Figure 7.1b The Axial Skeleton

Figure 7.1b

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THE AXIAL SKELETON

• The axial skeleton consists of 80 bones in

three regions:

– The skull

– The vertebral column

– The bony thorax

• The axial skeleton supports the head and

trunk and protects important organs.

– Brain

– Heart

– Lungs

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THE SKULL

• The skull is the most complex skeletal

structure consisting of 22 bones.

– The cranium protects the brain

– The facial bones:

• Form the facial features

• Place for special sense organs

• Passages for air and food

• Secure the teeth

• Attachment sites for facial muscles

• With the exception of the mandible, all skull

bones are connected to each other thru

sutures.

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• Consists of the cranium and the bones of the face

– The cranium encloses cranial cavity

– Facial bones surround and protect the entrances to the

respiratory and digestive tracts

• Superficial landmarks include the sutures

– Lambdoid

– Coronal

– Sagittal

– Squamous

The skull

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Figure 7.2 Cranial and Facial

Subdivisions of the Skull

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Figure 7.3 The Adult Skull

Figure 7.3a, b

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Figure 7.3 The Adult Skull

Figure 7.3c

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Figure 7.3 The Adult Skull

Figure 7.3d

****Only

movable joint

on skull bone

is attachment

between

mandible and

cranium.

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• one occipital bone

– foramen magnum

• two parietal bones

• one frontal bone

– frontal sinuses

Focus: The Individual Bones of the

Skull Cranial Bones

• two temporal bones

– auditory ossicles

• one sphenoid

• one ethmoid

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Infant Skull

• Contains cartilaginous soft spots called

fontanelles.

• What function do fontanelles serve?

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The Hyoid Bone

• The hyoid bone is the

“adam’s apple”

• It serves as a point of

attachment for

muscles that perform

the act of swallowing,

or deglutition.

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The Vertebral Column

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The Rib Cage

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Appendicular Skeleton

• Girdles

– Pectoral or shoulder

– Pelvic

• Upper Limbs

– Arm (brachial)

– Forearm (_antebrachium_)

– Wrist (carpal)

– Hand (manual)

• Lower Limbs

– Thigh (femoral)

– Leg (__crural_)

– Foot (pedal)Fig. 7.1

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THE PECTORAL GIRDLE

• The pectoral girdle is formed by the clavicle

and the scapula.

• Only the clavicle actually attaches to the

thorax.

• The scapula “floats” on the back of the ribs.

• The humerus attaches loosely to the sockets

formed by the scapula and clavicle.

– This is good for freedom of movement.

– This is not as good for stability.

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VIEW OF THE PECTORAL

GIRDLE

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Pectoral Girdle• Scapula (2)

– Acromion process

• Forms protective cover

• Attachment for clavicle

• Attachment for muscles

– Coracoid process

• Attachment for muscles

– ____Clavicle___

• Articulates with humerus

• Clavicle (2)

Fig. 7.29

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THE UPPER LIMB

• The upper limb consists of the:

– Arm

– Forearm

– Hand

• The upper limb contains 30 bones.

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VIEW OF THE UPPER LIMB

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Arm• Humerus

– Head

– Tubercles

• Greater and lesser

– Intertubercular groove

– Capitulum

– Trochlea

– Epicondyles

• Attachment of forearm

muscles

Fig. 7.30

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Forearm

• Radius

– Thumb side

– ___radial tuberosity_____ (biceps brachii muscle)

• Ulna

– Little finger side

– Trochlear notch

– Olecranon process

– Radial notchFig. 7.31

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Wrist and Hand

• Wrist

– 8 carpal bones

• Metacarpals: hand

bones

• Phalanges: finger

bones

Fig. 7.32

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THE PELVIC GIRDLE

• The pelvic girdle attaches the lower limbs to

the axial skeleton.

• The attachment of the pelvis to the sacrum

is an incredibly stable and strong

attachment, unlike the pectoral girdle.

• The socket for the femur (acetabulum) is

deep & holds the femur extremely well.

– Less mobile ball & socket joint than the

shoulder.

• Each wing of the pelvic girdle is formed

from a bone called the coxal bone.

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Pelvis

• Coxae: Right and Left

– Ilium- larger

– Ischium- smaller

– Pubis

• _pubic arch or pubic

symphisis______

• Acetabulum

• Obturator foramen

• Sacrum

Fig. 7.35

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Coxa

Fig. 7.36

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FEMALE VS. MALE PELVIS

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Female vs. Male Pelvic Girdle

• What purpose do the differences between

the female and male pelvic girdles serve?

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THE LOWER LIMB

• The bones of the lower limb must support

the weight of the entire body, thus, these are

the largest and heaviest of the bones.

• The lower limb consists of:

– The thigh

– The leg

– The foot

• The lower limb is formed by 30 bones.

– 1 patella

– -1 tarsal vs carpal

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Thigh

• Femur

– Head

– Neck

– Trochanters

• Greater and lesser

– Condyles

• Medial and lateral

– Epicondyles

• Medial and lateral

• _____Patella_____ or kneecap

Fig. 7.39

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Leg

• Tibia

– Larger and supports

most of weight

– Tibial tuberosity

– Medial malleolus

• Fibula

– Articulates with tibia

not femur

– Lateral malleolus

Fig. 7.41

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Foot

• Tarsals (7)

– _Talus___

(ankle bone)

– _Calcaneus__

(heel)

• Metatarsals:

foot bones

• Phalanges: toe

bones

Fig. 7.43

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Points to Remember

• Appendicular skeleton includes bones of upper and lower limbs and pectoral and pelvic girdles

• Pectoral girdle and upper limb held in place largely by muscles

• Pelvic girdle has strong articulation with sacrum to help support weight of body

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Practice Question 1

Each of the following bones contributes to

forming the orbit except the

A. ethmoid bone.

B. nasal bone.

C. lacrimal bone.

D. sphenoid bone.

E. frontal bone.

******

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Practice Question 2

Each of the following bones is part of the

pelvic girdle except the

A. femur.

B. ischium.

C. pubis.

D. ilium.

E. coxa.

*****

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Practice Question 3

In the true female pelvis, as compared to the true male pelvis,

A. the bones are heavier and thicker with prominent markings.

B. the distance between the anterior superior iliac spines is greater.

C. the ischium, ilium, and pubis remain unfused in adulthood.

D. the angle formed at the junction of the pubic bones is narrow.

E. the dimensions of the pelvic outlets are smaller.

*****

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Practice Question 4

The eleventh and twelfth ribs are called floating ribs

because they lack

A. a posterior attachment to thoracic vertebrae.

B. an anterior attachment to lumbar vertebrae.

C. an vertebral attachment anteriorly.

D. an anterior attachment to the sternum.

E. an vertebral attachment posteriorly.

*****

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Practice Question 5

The bones of the forearm include the

A. humerus.

B. fibula.

C. radius.

D. tibia.

E. femur.

*****

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Practice Question 6

The medial bulge at your ankle is a projection

from the

A. femur.

B. fibula.

C. calcaneus.

D. talus.

E. tibia. *****

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Practice Question 7

Which of the following is not a part of the

axial division of the skeletal system?

A. Vertebral column

B. Hyoid bone

C. Skull

D. Auditory ossicles

E. Pectoral girdle *****

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Practice Question 8

At its distal end the femur articulates with

the

A. fibia

B. tibia.

C. acetabulum.

D. tibia and fibula.

*****

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Practice Question 9

A common injury in the winter are falls in which someone hits the back of their head on the ice. What bone is most likely to be involved in this type of fall?

A. Zygomatic

B. Frontal

C. Temporal

D. Occipital *****

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Practice Question 10

• As you proceed from the head down the

vertebral column, the vertebrae become

larger and heavier.

True

False

*****

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Practice Question 11

• Damage to the temporal bone would most

likely affect the sense of hearing.

True

False

*****

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Practice Question 12

• Differences in the skeleton of males and

females can best be seen in the

characteristics of the pelvis.

True

False

*****

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Practice Question 13

• Ribs that have no connection to the sternum

are called the false ribs.

True

False *****

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Practice Question 14

• The axial skeleton includes the bones of the

upper and lower extremities and the

girdles.

True

False *****

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Practice Question 15

• The bones of the forearm are also called

antebrachium.

True

False*****

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Practice Question 16

• The sacrum is composed of 5 fused

vertebrae.

True

False*****

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Practice Question 17

• At its proximal end the humerus articulates

with the ulna and radius.

True

False *****

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Practice Question 18

• An injury to the lateral side of your ankle

would involve the tibia.

True

False *****

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Practice Question 19

The clavicle is part of the axial skeleton.

True

False *****