Download The Axial Skeleton

The Axial Skeleton
• Forms the longitudinal axis of the body
• Divided into three parts
– Skull
– Vertebral column
– Bony thorax
Cranium
Skull
Facial bones
Clavicle
Thoracic cage
(ribs and
sternum)
Scapula
Sternum
Rib
Humerus
Vertebral
column
Vertebra
Radius
Ulna
Sacrum
Carpals
Phalanges
Metacarpals
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
Phalanges
(a) Anterior view
Figure 5.8a
Cranium
Bones of
pectoral
girdle
Clavicle
Scapula
Upper
limb
Rib
Humerus
Vertebra
Radius
Ulna
Carpals
Bones
of
pelvic
girdle
Phalanges
Metacarpals
Femur
Lower
limb
Tibia
Fibula
(b) Posterior view
Figure 5.8b
The Skull
• Two sets of bones
– Cranium
– Facial bones
• Bones are joined by sutures
• Only the mandible is attached by a freely
movable joint
Coronal suture
Frontal bone
Parietal bone
Sphenoid bone
Temporal bone
Ethmoid bone
Lambdoid
suture
Lacrimal bone
Squamous suture
Nasal bone
Occipital bone
Zygomatic bone
Zygomatic process
Maxilla
External acoustic meatus
Mastoid process
Styloid process
Mandibular ramus
Alveolar
processes
Mandible (body)
Mental foramen
Figure 5.9
Frontal bone
Sphenoid
bone
Cribriform plate
Crista galli
Ethmoid
bone
Optic canal
Sella turcica
Foramen ovale
Temporal bone
Jugular foramen
Internal
acoustic meatus
Parietal bone
Occipital bone
Foramen magnum
Figure 5.10
Hard
palate
Maxilla
(palatine process)
Palatine bone
Zygomatic bone
Temporal bone
(zygomatic process)
Maxilla
Sphenoid bone
(greater wing)
Foramen ovale
Vomer
Mandibular fossa
Carotid canal
Styloid process
Mastoid process
Temporal bone
Jugular foramen
Occipital condyle
Parietal bone
Foramen magnum
Occipital bone
Figure 5.11
Coronal suture
Frontal bone
Parietal bone
Nasal bone
Superior orbital fissure
Sphenoid bone
Ethmoid bone
Lacrimal bone
Optic canal
Temporal bone
Zygomatic bone
Middle nasal concha
of ethmoid bone
Maxilla
Inferior nasal concha
Vomer
Mandible
Alveolar processes
Figure 5.12
Paranasal Sinuses
• Hollow portions of bones surrounding the
nasal cavity
• Functions of paranasal sinuses
– Lighten the skull
– Give resonance and amplification to voice
Frontal sinus
Ethmoid sinus
Sphenoidal sinus
Maxillary sinus
(a) Anterior view
Figure 5.13a
Frontal sinus
Ethmoid sinus
Sphenoidal sinus
Maxillary sinus
(b) Medial view
Figure 5.13b
The Hyoid Bone
• The only bone that does not articulate with
another bone
• Serves as a moveable base for the tongue
• Aids in swallowing and speech
Greater horn
Lesser horn
Body
Figure 5.14
The Fetal Skull
• The fetal skull is large compared to the infant’s
total body length
– Fetal skull is 1/4 body length compared to adult
skull which is 1/8 body length
• Fontanels—fibrous membranes connecting
the cranial bones
– Allow skull compression during birth
– Allow the brain to grow during later pregnancy
and infancy
– Convert to bone within 24 months after birth
Frontal bone
Anterior
fontanel
Parietal
bone
Posterior fontanel
Occipital
bone
(a)
Figure 5.15a
Parietal bone
Posterior
fontanel
Occipital
bone
Mastoid
fontanel
Anterior fontanel
Sphenoidal
fontanel
Frontal
bone
Temporal bone
(b)
Figure 5.15b
The Vertebral Column
• Each vertebrae is given a name according to
its location
– There are 24 single vertebral bones separated by
intervertebral discs
• Seven cervical vertebrae are in the neck
• Twelve thoracic vertebrae are in the chest region
• Five lumbar vertebrae are associated with the lower
back
The Vertebral Column
• Nine vertebrae fuse to form two composite
bones
– Sacrum
– Coccyx
Anterior
1st cervical
vertebra (atlas)
2nd cervical
vertebra (axis)
1st thoracic
vertebra
Transverse
process
Spinous
process
Intervertebral
disc
Posterior
Cervical curvature
(concave)
7 vertebrae,
C1 – C7
Thoracic curvature
(convex)
12 vertebrae,
T1 – T12
Intervertebral
foramen
1st lumbar
vertebra
Lumbar curvature
(concave)
5 vertebrae,
L1 – L5
Sacral curvature
(convex)
5 fused vertebrae
Coccyx
4 fused vertebrae
Figure 5.16
The Vertebral Column
• Primary curvatures are the spinal curvatures
of the thoracic and sacral regions
– Present from birth
– Form a C-shaped curvature as in newborns
• Secondary curvatures are the spinal
curvatures of the cervical and lumbar regions
– Develop after birth
– Form an S-shaped curvature as in adults
Figure 5.17
Figure 5.18
A Typical Vertebrae
• Body
• Vertebral arch
– Pedicle
– Lamina
•
•
•
•
Vertebral foramen
Transverse processes
Spinous process
Superior and inferior articular processes
Posterior
Vertebral
arch
Lamina
Transverse
process
Spinous
process
Superior
articular
process
and
facet
Pedicle
Vertebral
foramen
Body
Anterior
Figure 5.19
(a) ATLAS AND AXIS
Transverse
process
Posterior
arch
Anterior
arch
Superior view of atlas (C1)
Transverse
process
Dens
Body
Spinous
process
Facet on
superior
articular
process
Superior view of axis (C2)
Figure 5.20a
(b) TYPICAL CERVICAL VERTEBRAE
Facet on superior
articular process
Spinous
process
Vertebral
foramen
Transverse
process
Superior view
Superior
articular
process
Spinous
process
Body
Transverse
process
Facet on inferior
articular process
Right lateral view
Figure 5.20b
(c) THORACIC VERTEBRAE
Spinous process
Transverse
process
Vertebral
foramen
Facet
for rib
Facet on
superior
articular
process
Body
Superior view
Facet on
superior
articular
process
Facet on
transverse
process
Body
Spinous
process
Costal facet
for rib
Right lateral view
Figure 5.20c
(d) LUMBAR VERTEBRAE
Spinous process
Vertebral
foramen
Transverse
process
Facet on
superior
articular
process
Body
Superior view
Superior
articular
process
Spinous
process
Body
Facet on inferior
articular process
Right lateral view
Figure 5.20d
Sacrum and Coccyx
• Sacrum
– Formed by the fusion of five vertebrae
• Coccyx
– Formed from the fusion of three to five vertebrae
– “Tailbone,” or remnant of a tail that other
vertebrates have
Ala
Sacral
canal
Superior Auricular
articular surface
process
Body
Sacrum
Coccyx
Median
sacral
crest
Posterior
sacral
foramina
Sacral
hiatus
Figure 5.21
The Bony Thorax
• Forms a cage to protect major organs
• Consists of three parts
– Sternum
– Ribs
• True ribs (pairs 1–7)
• False ribs (pairs 8–12)
• Floating ribs (pairs 11–12)
– Thoracic vertebrae
T1 vertebra
Jugular notch
Clavicular notch
Manubrium
Sternal angle
Body
Xiphisternal
joint
Xiphoid
process
True
ribs
(1 –7)
Sternum
False
ribs
(8–12)
L1
Vertebra
(a)
Floating
ribs (11, 12)
Intercostal
spaces
Costal cartilage
Figure 5.22a
T2
T3
T4
Jugular
notch
Sternal
angle
Heart
T9
Xiphisternal
joint
(b)
Figure 5.22b
The Appendicular Skeleton
• Composed of 126 bones
– Limbs (appendages)
– Pectoral girdle
– Pelvic girdle
Cranium
Skull
Facial bones
Clavicle
Thoracic cage
(ribs and
sternum)
Scapula
Sternum
Rib
Humerus
Vertebral
column
Vertebra
Radius
Ulna
Sacrum
Carpals
Phalanges
Metacarpals
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
Phalanges
(a) Anterior view
Figure 5.8a
Cranium
Bones of
pectoral
girdle
Clavicle
Scapula
Upper
limb
Rib
Humerus
Vertebra
Radius
Ulna
Carpals
Bones
of
pelvic
girdle
Phalanges
Metacarpals
Femur
Lower
limb
Tibia
Fibula
(b) Posterior view
Figure 5.8b
The Pectoral (Shoulder) Girdle
• Composed of two bones
– Clavicle—collarbone
• Articulates with the sternum medially and with the
scapula laterally
– Scapula—shoulder blade
• Articulates with the clavicle at the acromioclavicular
joint
• Articulates with the arm bone at the glenoid cavity
• These bones allow the upper limb to have
exceptionally free movement
Acromioclavicular Clavicle
joint
Scapula
(a) Articulated right shoulder (pectoral) girdle
showing the relationship to bones of the
thorax and sternum
Figure 5.23a
Posterior
Sternal (medial)
end
Acromial (lateral)
end
Anterior
Superior view
Acromial end
Sternal end
Anterior
Posterior
Inferior view
(b) Right clavicle, superior and inferior views
Figure 5.23b
Suprascapular notch
Coracoid process
Superior
angle
Acromion
Glenoid cavity
at lateral angle
Spine
Medial
border
Lateral border
(c) Right scapula, posterior aspect
Figure 5.23c
Acromion
Coracoid
process
Suprascapular notch
Superior border
Superior
angle
Glenoid
cavity
Lateral
(axillary)
border
Medial
(vertebral)
border
Inferior angle
(d) Right scapula, anterior aspect
Figure 5.23d
Bones of the Upper Limbs
• Humerus
– Forms the arm
– Single bone
– Proximal end articulation
• Head articulates with the glenoid cavity of the scapula
– Distal end articulation
• Trochlea and capitulum articulate with the bones of the
forearm
Greater
tubercle
Lesser
tubercle
Head of
humerus
Anatomical neck
Intertubercular
sulcus
Deltoid
tuberosity
Radial
fossa
Coronoid
fossa
Capitulum
(a)
Medial
epicondyle
Trochlea
Figure 5.24a
Head of
humerus
Anatomical
neck
Surgical
neck
Radial
groove
Deltoid
tuberosity
Medial
epicondyle
Olecranon
fossa
Trochlea
Lateral
epicondyle
(b)
Figure 5.24b
Bones of the Upper Limbs
• The forearm has two bones
– Ulna—medial bone in anatomical position
• Proximal end articulation
– Coronoid process and olecranon articulate with the humerus
– Radius—lateral bone in anatomical position
• Proximal end articulation
– Head articulates with the capitulum of the humerus
Trochlear notch
Olecranon
Head
Neck
Radial
tuberosity
Coronoid
process
Proximal
radioulnar
joint
Radius
Ulna
Interosseous
membrane
Ulnar styloid
process
Radial
styloid
process
(c)
Distal
radioulnar
joint
Figure 5.24c
Bones of the Upper Limbs
• Hand
– Carpals—wrist
• Eight bones arranged in two rows of four bones in each
hand
– Metacarpals—palm
• Five per hand
– Phalanges—fingers and thumb
• Fourteen phalanges in each hand
• In each finger, there are three bones
• In the thumb, there are only two bones
Distal
Phalanges
(fingers)
Middle
Proximal
Metacarpals
(palm)
4
3
2
5
1
Trapezium
Hamate
Trapezoid
Carpals Pisiform
(wrist) Triquetrum
Scaphoid
Capitate
Lunate
Ulna
Radius
Figure 5.25