The Skeleton
Part A
Human Anatomy & Physiology, Sixth Edition
7
The Axial Skeleton
 Eighty bones segregated into three regions
 Skull
 Vertebral column
 Bony thorax
The Skull
 The skull
 Cranium
 Eight cranial bones –
 2 parietal, 2 temporal, frontal, occipital, sphenoid, and
ethmoid
 Facial bones
 Fourteen bones
 2 maxillae, 2 zygomatics, 2 nasals, 2 lacrimals, 2 palatines,
and 2 inferior conchae
 mandible and vomer are unpaired
Skull: Anterior View
Figure 7.2a
Skull: Lateral View
Figure 7.3a
Skull: Posterior View
Figure 7.2b
Inferior Portion of the Skull
Figure 7.4a
Paranasal Sinuses
Figure 7.11
Vertebral Column
 26 irregular bones
 7 Cervical vertebrae
 12 Thoracic vertebrae
 5 Lumbar vertebrae
 Sacrum – 5 fused bones
 Coccyx – 4 fused bones
Vertebral Column: Ligaments
 Anterior (ventral) and posterior (dorsal) longitudinal ligaments
 Short ligaments connect adjoining vertebrae together
General Structure of Vertebrae
Figure 7.15
Vertebral Column: Intervertebral Discs
 Nucleus pulposus – inner gelatinous
region
 Annulus fibrosus – collar of collagen and
fibrocartilage
Cervical Vertebrae: The Atlas (C1)
Figure 7.16a, b
Cervical Vertebrae: The Axis (C2)
Figure 7.16c
Cervical Vertebrae
Figure 7.17a
Sacrum and Coccyx: Posterior (dorsal) View
Figure 7.18b
Thorax (Thoracic Cage)
 The thoracic cage
 Dorsal - thoracic vertebrae
 Laterally - ribs
 Ventral - sternum and costal cartilages
 Functions
 Protective cage around the heart,
lungs, and great blood vessels
 Supports the pectoral girdle and upper limbs
 Attachment sites for neck, back, chest, and shoulder muscles
 Intercostal muscles lift and depress the thorax for breathing
Thorax: Sternum
 Fusion of three bones
 manubrium,
 sternal body,
 xiphoid process
Thorax: Ribs
 12 pairs
 All attached dorsally to the
thoracic vertebrae
 Vertebrosternal ribs –attach
to sternum via costal
cartilages – “true ribs”
 Vertebrochondral ribs attach to costal cartilage of
rib 7 – “false ribs”
 Vertebral ribs - no ventral
attachment – “floating
ribs”
Pectoral Girdle (Shoulders)
Figure 7.22a
Scapulae (Shoulder Blades)
Figure 7.22d, e
The Upper Limb
 The proximal arm (brachium), distal arm (forearm;
antebrachium), and hand (manus)
 Thirty-seven bones
Humerus of the Proximal Arm
Figure 7.23
Radia and Ulna of the Distal Arm (Forearm)
Figure 7.24
Manus (Hand)
14
5
8
Figure 7.26a
Pelvic Girdle (Hips)
 Os coxae - coxal bones
 Coxal bone is fusion of 3 bones – ilium, ischium, pubis
 Os coxae, sacrum and coccyx, form the bony pelvis
Os coxa: Lateral View
Obturator
foramen
Comparison of Male and Female Pelvic Structure
 Female pelvis
 Tilted forward, adapted for
childbearing
 Pubic arch obtuse angle
 Cavity of the true pelvis is
broad, shallow,
 Male pelvis
 Less tilted forward
 Pubic arch acute angle
 Cavity of true pelvis is narrow
and deep
The Lower Limb
 the thigh (proximal), leg (distal), and foot
Femur
Figure 7.28b
Tibia and Fibula
Figure 7.29
Foot
14
5
7
Figure 7.31b, c
Developmental Aspects: Fetal Skull
 At birth, fetal skull
bones are incomplete
and connected by
fontanels
 Fontanels
 Unossified remnants
of fibrous membranes
between bones
 anterior,
 posterior
 mastoid
 sphenoid
Figure 7.33
Developmental Aspects: Growth Rates
 At birth, the cranium is
huge relative to the face
 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
Figure 7.34