1. The Skeletal System: The Axial Skeleton
Chapter 7
The Skeletal System: The Axial Skeleton

2. Axial and Appendicular Skeleton
Fig. 7.1, Pg 200
Axial Skeleton
80 bones
lie along longitudinal axis
skull, hyoid, vertebrae, ribs, sternum, ear auditory ossicles
(blue color)
Appendicular Skeleton
126 bones
upper and lower limbs
pelvic and pectoral girdles
(yellow color)
Total = 206 bones

4. Types of Bones 5 basic types of bones: long  compact
short s  spongy except surface
flat  plates of compact enclosing spongy
irregular  variable
sesamoid  develop in tendons or ligaments (patella)
Sutural bones  in joint between skull bones

5. BONE SURFACE MARKINGS There are two major types of surface markings.
Depressions and openings participate in joints or allow the passage of soft tissue.
Processes are projections or outgrowths that either help form joints or serve as attachment points for connective tissue.
BONE SURFACE MARKINGS

6. The Skull
The skull, composed of 22 bones, consists of the 8 cranial bones (cranium) and the 14 facial bones (face).
General Features
The skull forms the large cranial cavity and smaller cavities, including the nasal cavity and orbits (eye sockets).
Certain skull bones contain mucous membrane lined cavities called paranasal sinuses.
The only moveable bone of the skull, other than the ear ossicles within the temporal bones, is the mandible.
Immovable joints called sutures hold the skull bones together.
8 Cranial bones
protect brain and house ear ossicles
muscle attachment for jaw, neck and facial muscles
14 Facial bones
protect delicate sense organs -- smell, taste, vision
support entrances to digestive and respiratory systems
Fig. 7.4, Pg 204

7. Cranial and Facial bones: functions
Fig. 7.4, Pg 204; Fig. 7.5, Pg 205
They protect the brain.
Their inner surfaces attach to membranes that stabilize the positions of the brain, blood vessels, and nerves.
The outer surfaces of cranial bones provide large areas of attachment for muscles that move the various parts of the head.
Facial bones form the framework of the face and protect and provide support for the nerves and blood vessels in that area.
Cranial and facial bones together protect and support the special sense organs.

8. The 8 Cranial Bones Frontal Parietal (2) Temporal (2) Occipital
Fig. 7.4, Pg 204; Fig. 7.5, Pg 205
Frontal
Parietal (2)
Temporal (2)
Occipital
Sphenoid
Ethmoid

9. Frontal Bone (1) Forehead, roof of orbits, and anterior cranial floor
Fig. 7.3, Pg 203
Forehead, roof of orbits, and anterior cranial floor
Supraorbital margin and frontal sinus
Frontal squama- forehead- (scale like plate)

10. Parietal, Temporal and Occipital Bones
Fig. 7.4, Pg 204; Fig. 7.5, Pg 205
Parietal (2)
sides and roof of cranial cavity
Temporal(2)
temporal squama
zygomatic process forms part of arch with zygomatic bone
Mandibula fossa-articulates with mandible
external auditory meatus
mastoid process
styloid process
Occipital(1)
foramen magnum
occipital condyles
external occipital protuberance attachment for ligamentum nuchae
superior and inferior nuchal lines

11. Sphenoid Bone Articulates with all the other cranial bones
Fig. 7.7, Pg 207; Fig. 7.8, Pg 208
Articulates with all the other cranial bones
Body is a cube-like portion holding sphenoid sinuses
Greater and lesser wings
Sphenoidal sinuses empty into nasal cavity
Pterygoid processes at the base of the skull are attachment sites for jaw muscles
Sella turcica holds pituitary gland
Optic foramen

12. Ethmoid Bone
Figure 7.9, pg.210
The ethmoid bone( light, spongy bone) forms part of the anterior portion of the cranial floor, the medial wall of the orbits, the superior portion of the nasal septum, and most of the superior side walls of the nasal cavity. It is a major superior supporting structure of the nasal cavity.
Crista galli attaches to the membranes that cover the brain
Lateral masses contain ethmoid sinuses
Perpendicular plate is upper part of nasal septum
Superior and middle nasal concha or turbinates ~ filters and warms air

13. 14 Facial Bones Nasal (2) Maxillae (2) Zygomatic (2)
Fig. 7.3, Pg 203
Nasal (2) Maxillae (2) Zygomatic (2)
Mandible (1) Lacrimal (2) Palatine (2)
Inferior nasal conchae (2) Vomer (1)

14. Palatine (2),Vomer (1) and Nasal Septum
L-shaped : one end is back part of hard palate, posterior part of nasal septum
Vomer
posterior part of nasal septum
Nasal Septum
divides nasal cavity into left and right sides. Formed by vomer, perpendicular plate of ethmoid and septal cartilage

15. part of medial wall of orbit Smallest bone of the face
Fig. 7.3, Pg 203
FRONTAL BONES
Nasal bones(2)
Lacrimal bones(2)
part of medial wall of orbit
Smallest bone of the face
lacrimal fossa houses lacrimal sac
Inferior nasal concha or turbinate (2)
(not part of ethmoid)
Zygomatic Bones(2)
cheekbones
lateral wall of orbit along with sphenoid
part of zygomatic arch along with part of temporal
Maxillary bones (2)
paired upper jaw bone
articulate with every facial bone (except the mandible)
floor of orbit, floor of nasal cavity and most of the hard palate
maxillary sinus
alveolar processes hold upper teeth

16. Mandible (Jaw Bone) Only moveable skull bone Body, angle and rami
Fig. 7.10, Pg 212
Only moveable skull bone
Body, angle and rami
Condylar and coronoid processes
Alveolar processes for lower teeth
Mandibular and mental foramen

17. Bones of the Orbit
Fig. 7.12, Pg 213
The orbits contain the eyeballs and associated structures and are formed by seven bones of the skull.
Roof is frontal and sphenoid
Lateral wall is zygomatic and sphenoid
Floor is maxilla, zygomatic and sphenoid
Medial wall is maxilla, lacrimal, ethmoid and sphenoid
Orbital fissures and optic foramen

18. Foramina (opening) of the Skull
Fig. 7.8, Pg 208
foramen magnum
optic foramen
mandibular foramen
carotid canal
stylomastoid foramen

19. Sutures
Fig. 7.4, Pg 204; Fig. 7.6, Pg 207
Sutures are immovable joints found only between skull bones and hold skull bones together.

20. Paranasal Sinuses
Fig. 7.13, Pg 215;
Paranasal sinuses are cavities in bones of the skull that communicate with the nasal cavity.
They are lined by mucous membranes and also serve to lighten the skull and serve as resonating chambers for speech.
Cranial bones containing the sinuses are the frontal, sphenoid, ethmoid, and maxillae.

21. Fontanels of the Skull at Birth.
Fig. 7.14, Pg 216
Fontanels are dense connective tissue membrane-filled spaces (soft spots) between the cranial bones of fetuses and infants. They remain unossified at birth but close early in a child’s life.
Fontanels have two major functions.
They enable the fetal skull to modify its size and shape as it passes through the birth canal.
They permit rapid growth of the brain during infancy.

22. Hyoid Bone U-shaped single bone
Fig. 7.15, Pg 217
U-shaped single bone
Does not articulate with any other bone of the body
Suspended by ligaments and muscles from skull
Supports the tongue and provides attachment for tongue, neck and pharyngeal muscles

23. Vertebral Column Backbone or spine made up of 26 vertebrae
Fig. 7.16, Pg 218
Backbone or spine made up of 26 vertebrae
Five vertebral regions
cervical vertebrae (7) in the neck
thoracic vertebrae (12) in the thorax
lumbar vertebrae (5) in the low back region
sacrum (5-fused)
coccyx (4-fused)

24. Intervertebral Discs Located between adjacent vertebrae
Fig, 7.16d, pg 218
Located between adjacent vertebrae
absorbs vertical shock
Permit various movements of the vertebral column
Fibrocartilagenous ring with a pulpy center

25. Herniated (Slipped) Disc
Fig. 7.24, Pg 229
Protrusion of the nucleus pulposus
Most commonly in lumbar region
Pressure on spinal nerves causes pain
Surgical removal of disc after laminectomy

26. Normal Curves of the Vertebral Column
Primary curves
Thoracic (anteriorly concave curve) and sacral (anteriorly concave curve) are formed during fetal development
Secondary curves
cervical (anteriorly convex curve) if formed when infant raises head at ~4 months
lumbar (anteriorly convex curve) forms when infant sits up and begins to walk at ~1 year

27. Typical Vertebrae (Thoracic)
Fig. 7.17, Pg 219
Body
weight bearing
Vertebral arch
pedicles
laminae
Vertebral foramen
Seven processes
2 transverse
1 spinous
4 articular
Vertebral notches

28. Intervertebral Foramen and Spinal Canal
Fig. 7.17, Pg 219
The spinal canal is all of the vertebral foramen together
Intervertebral foramen are two vertebral notches together

29. Seven Cervical Vertebrae
Atlas and Axis (C1-C2)
Seven Cervical Vertebrae
Pg 217
Atlas- ring of bone, superior facets for occipital condyles
supports the skull .
nodding movement at atlanto-occipital joint signifies “yes”
Axis - dens or odontoid process is body of atlas
- side-to-side rotation of the head
- pivotal movement at atlanto-axial joint signifies “no”

30. Typical Cervical Vertebrae (C3-C7)
Fig. 7.18, Pg 220
Smaller bodies but larger spinal canal
Transverse processes
shorter, with transverse foramen for vertebral artery
Bifid spinous processes on C2 to C6
The seventh called the vertebra prominens is somewhat different

31. 12 Thoracic Vertebrae (T1-T12)
Fig. 7.19, Pg 222
12 Thoracic Vertebrae (T1-T12)
Larger and stronger bodies
Longer transverse and spinous processes (projects inferiorly-T1-T10)
Facets or demifacets on body for head of rib
Facets on transverse processes (T1-T10) for tubercle of rib
Pg 223

32. 5 Lumbar Vertebrae Strongest and largest
Fig. 7.20, Pg 225
Strongest and largest
Short thick spinous (projects posteriorly) and transverse processes
back musculature

33. Sacrum and Coccyx Sacrum
Fig. 7.21, Pg 225
Sacrum
Union of 5 vertebrae (S1 - S5) by ~30 years of age
median sacral crest was spinous processes
sacral ala is fused transverse processes
Sacral canal ends at sacral hiatus
Coccyx
Union of 4 vertebrae (Co1 - Co4) by ~30 years of age

35. Thorax The term thorax refers to the entire chest.
Fig. 7.22, Pg 227
The term thorax refers to the entire chest.
The skeletal part of the thorax (a bony cage) consists of the sternum, costal cartilages, ribs, and the bodies of the thoracic vertebrae.
The thoracic cage encloses and protects the organs in the thoracic and superior abdominal cavities. It also provides support for the bones of the shoulder girdle and upper limbs.

36. Sternum Three parts Manubrium 1st and 2nd ribs clavicular notch Body
Fig.7.22 , Pg 227
Three parts
Manubrium
1st and 2nd ribs
clavicular notch
Body
costal cartilages of 2-10 ribs
Xiphoid
ossifies by
~40 years of age.

37. Thorax Bony cage flattened from front to back Sternum (breastbone)
Fig.7.22, Pg 227
Bony cage flattened from front to back
Sternum (breastbone)
Ribs
1-7 are true ribs (vertebrosternal)
8-12 are false ribs (vertebrochondral)
11-12 are floating
Costal cartilages
Bodies of the thoracic vertebrae.

38. The 12 pairs of ribs give structural support to the sides of the thoracic cavity
The first 7 pairs of ribs (increase in size) are called true ribs; the remaining five pairs, false ribs (with the last two false ribs called floating ribs).
Head and tubercle articulate with facets
Body with costal groove containing nerve and blood vessels
Intercostal spaces contain intercostal muscles
Rib fractures are the most common types of chest injuries.
Fig.7.23, Pg 228

39. Rib Articulation Tubercle articulates with transverse process
Fig.7.23c, Pg 228
Tubercle articulates with transverse process
Head articulates with vertebral bodies