1. The Axial Skeleton Fun Facts About Bones
Bone is made of the same type of minerals as limestone.
Babies are born with 300 bones, but only have 206 by adulthood.
Mice and giraffes have the same number of bones in their neck as a human: 7.
The long horned ram can take a head butt at 25 mph. The human skull will fracture at 5 mph.

2. The Axial and Appendicular Skeleton
About 206 bones
Sesamoid bones range from (2-26)
2 major divisions:
Axial
Appendicular
Everyone has sesamoid bones making up their patella or kneecaps, but whether we have them in other locations varies.
Many animals do without a skeleton of any kind. For example, earthworms, sea worms, and mollusks like octopuses have muscles and complex nervous systems, but have no rigid skeletal elements at all. This is because their bodies have no need to resist gravity. Humans, on the other hand, need to stand upright and walk in opposition to gravity, so our muscles need rigid structural elements to pull upon to produce movement.

3. The Axial Skeleton Head, neck, trunk Skull Hyoid bone Vertebral Column
Thoracic Cage (12 pairs of ribs)
Sternum

4. The Axial Skeleton Fig 7-1
The axial skeleton forms the longitudinal axis of the body.
It consists of 80 bones.
The skull has 8 cranial bones and 14 facial bones.
The bones associated with the skull include 6 auditory ossicles which we’ll put off until Ch 17 and the hyoid bone.
The thoracic cage has 24 ribs and the sternum
Finally the vertebral column has 24 vertebrae + 1 sacrum + 1 coccyx.
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Fig 7-1

5. The Axial Skeleton Functions of the Axial Skeleton
Supports and protects organs in body cavities
Attaches to muscles of
Head, neck, and trunk
Respiration
Appendicular skeleton

6. The Skull The skull protects The skull contains 22 bones The brain
Entrances to respiratory system
Entrance to digestive system
The skull contains 22 bones
8 cranial bones:
Form the braincase or cranium
14 facial bones:
Protect and support entrances to digestive and respiratory tracts
The axial skeleton begins with the skull.

7. The Skull
Fig 7-3
The cranial part of the skull is composed of 8 curved plates of bone that interlock with each other and enclose the brain. The bone beneath your forehead is the frontal bone, while the bone at the back of your skull is the occipital bone. If you cup your hands around your ears, you’ll be outlining the temporal bone. Above them are the right and left parietal bones. The bottom of the brain is supported by a single sphenoid bone, which extends flat plates from the midline that resembles the wings of a butterfly.
The cranial part of the skull is composed of 8 curved plates of bone that interlock with each other
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8. The Skull
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Fig 7-3

9. The Skull 14 bones form the face Fig 7-3d
There are 14 bones in the portion of the skull forming the face. One large bone is the jawbone, or mandible. Nine of them (nasal, lacrimal, palatine, vomer, and inferior nasal conchae) form the structure of the nasal cavity and have a complicated anatomy that can only be viewed by dissecting the skull apart. The remaining 4 bones are the right and left zygomatic bones that form the cheeks and the maxillary bones that form the upper jaw. Your upper teeth are rooted into the maxilla, whereas the lower teeth insert into the mandible.
14 bones form the face
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Fig 7-3d

10. The Skull
Here we can better appreciate 3 of the 9 bones that form the nasal cavity – the vomer and the 2 palatine bones. The palatine bones form the posterior portion of the hard palate.
We can also see the inferior side of the maxillary bones that forms the upper jaw and root the upper teeth.
What’s missing here is the mandible that contains the lower teeth.
We can also appreciate the Foramina through the occipital bone that serves as the openings for nerves and blood vessels.
© 2009 Pearson Education, Inc.
Fig 7-3e

11. The Skull
In red we can see the 8 cranial bones that enclose the brain.
In green, is another good view of the most of the 9 bones that form the nasal cavity – nasal, lacrimal, palatine, vomer, and inferior nasal conchae. The palatine bones form the posterior portion of the hard palate.
In purple, we can some of the remaining 5 bones that form the face including the maxillary bone that forms the upper jaw and root the upper teeth, as well as the mandible that contains the lower teeth.
Fig 7-4

12. The Skull
Some special features within some of the bones of the cranial cavity.
Fig 7-4

13. The Skull Superficial Facial Bones (for muscle attachment)
Maxillae = maxillary bones
Lacrimal
Nasal
Zygomatic
Mandible
Deep Facial Bones
1. Separate the oral and nasal cavities
2. Form the nasal septum
Palatine bones
Inferior nasal conchae
Vomer

14. The Skull Sinuses Sutures
Cavities that decrease the weight of the skull
Lined with mucous membranes
Protect the entrances of the respiratory system
Sutures
The immovable joints of the skull
The four major sutures
Lambdoid suture
Coronal suture
Sagittal suture
Squamous suture

15. The Skull __________________ Suture Between occipital & parietal bones
May contain sutural (Wormian) bones
Between frontal & parietal bones
The calvaria (skullcap)
Consists of occipital, parietal, and frontal bones
Between the parietal bones
From lambdoid suture to coronal suture
Fig 7-3

16. The Skull ___________________ Sutures
During development, the skull organizes around the developing brain as both the brain and skull grow rapidly. Fontanelles, which are non-ossified areas b/n cranial bones allow for the skull and brain growth.
The premature closing of one or more fontanelles is called craniostenosis.
___________________ Sutures
Form boundaries between temporal bones and parietal bones
Fig 7-3

17. The Cranial Bones of the Skull
Occipital bone
Parietal bones
Frontal bone
Temporal bones
Sphenoid
Ethmoid
Let’s go through the 8 cranial bones in more detail.

18. The Cranial Bones of the Skull
The _________________ Bone
Functions of the occipital bone
Forms the posterior and inferior surfaces of the cranium
Articulations of the occipital bone
Parietal bones
Temporal bones
Sphenoid (underneath)
First cervical vertebra (atlas)
Marks of the occipital bone
External occipital protuberance (bulge)
External occipital crest (prominent ridge):
to attach ligaments

19. The Cranial Bones of the Skull
The Occipital Bone
Marks of the occipital bone
Occipital ________: articulate with neck
Inferior and superior nuchal lines: attachment site of muscles and ligaments
Foramina of the occipital bone
____________________: connects cranial and spinal cavities
Jugular foramen: for jugular vein
_________________________: for hypoglossal nerves
Hypoglossal nerves (CN 11) provide motor control to muscles of the tongue.
Fig 7-5

20. The Cranial Bones of the Skull
The ___________________ Bones
Functions of the parietal bones
Forms part of the superior and lateral surfaces of the cranium
Articulations of the parietal bones
Other parietal bone
Occipital bone
Temporal bone
Frontal bone
Sphenoid

21. The Cranial Bones of the Skull
The Parietal Bones
Marks of the parietal bones
Superior and inferior temporal lines:
to attach temporalis muscle
Grooves for cranial blood vessels
Fig 7-5

22. The Cranial Bones of the Skull
The __________________ bone
Functions of the frontal bone
Forms the anterior cranium and upper eye sockets
Contains frontal sinuses
Cavities lined with mucous membranes that protect the entrances of the respiratory system
Articulations of the frontal Bone
Parietal bone
Maxilla
Metopic suture
Ethmoid
Lacrimal bone
Zygomatic bone
Sphenoid
Nasal bone

23. The Cranial Bones of the Skull
The Frontal Bone
Marks of the frontal bone
Frontal squama (forehead)
Supra-orbital margin (protects eye)
_________________(for tear ducts)
Frontal sinuses
Foramina of the frontal bone
Supra-orbital foramen:
for blood vessels of eyebrows, eyelids, and frontal sinuses
Supra-orbital notch:
an incomplete supra-orbital foramen
Fig 7-6

24. The Cranial Bones of the Skull
The Temporal Bones
Functions of the temporal bones
Part of lateral walls of cranium and zygomatic arches
Articulate with mandible
Surround and protect inner ear
Attach muscles of jaws and head
Articulations of the temporal bones
Zygomatic bone
Sphenoid
Parietal bone
Occipital bone
Mandible
Fig 7-7

25. The Cranial Bones of the Skull
Marks of the Temporal Bones
Squamous part: borders the squamous suture
Mandibular fossa (depression): articulates with the mandible
___________________ process (projection or bump)
Inferior to the squamous portion
Articulates with temporal process of zygomatic bone
Forms zygomatic arch (cheekbone)
______________________ (canal): ends at tympanic membrane
Mastoid process
For muscle attachment

26. The Cranial Bones of the Skull
Functions of the Sphenoid
Part of the floor of the cranium
Unites cranial and facial bones
Strengthens sides of the skull
Contains sphenoidal sinuses
Articulations of the Sphenoid
Ethmoid
Frontal bone
Occipital bone
Parietal bone
Temporal bone
Palatine bones
Zygomatic bones
Maxillae
Vomer
The bottom of the brain is supported by a single sphenoid bone, which extends flat plates from the midline that resembles the wings of a butterfly.

27. The Cranial Bones of the Skull
Aside from making the floor of the cranium and strengthening the sides, the sphenoid bone also has many other functions with its many foramina.
The optical canals will allow passage for the optic nerves, the superior orbital fissure not viewed here for the blood vessels and nerves of the orbit, the foramen rotundum and ovale for blood vessels and nerves of the face, and the foramen spinosum for blood vessels and nerves of the jaw.
Greater wing forms part of the cranial floor
Hypophyseal fossa of the sella turcica holds the ____________
Foramens hold blood vessels & nerves of the face and jaws
Fig 7-8

28. The Cranial Bones of the Skull
Functions of the ethmoid
Forms anteromedial floor of the cranium
Roof of the nasal cavity
Part of the nasal septum and medial orbital wall
Contains ethmoidal air cells (network of sinuses)
If you get punched in the nose, this is the bone most likely to fracture.
Fig 7-4

29. The Cranial Bones of the Skull
Articulations of the Ethmoid
Frontal bone
Sphenoid
Maxillary bones
Nasal bone
Lacrimal bone
Palatine bone
Inferior nasal conchae
Vomer
The Ethmoid articulates with the frontal and sphenoid bones of the skull, the maxillary bones (upper jaw) of the face, and all of the nasal bones that form the nasal cavity except the zygomatic bones.

30. The Cranial Bones of the Skull
Parts of the Ethmoid
The _______________ plate
Floor of the cranium
Roof of the nasal cavity
Contains crista galli
The 2 lateral masses
Superior and middle nasal conchae
The perpendicular plate
Part of the nasal septum
__________________ foramina
In the cribriform plate
For olfactory nerves
Fig 7-9

31. The Facial Bones of the Skull
Maxillae (2 maxillary bones - upper jaw)
Palatine bones (2, posterior portion of hard palate)
Nasal bones (2, support bridge of nose & connect to cartilage)
Vomer (1, forms inferior portion of the bony nasal septum)
Inferior nasal conchae (2)
1. Creates air turbulance in nasal cavity to warm and humidify inhaled air
2. increases epithelial surface area
Zygomatic bones (2, lateral wall of the orbit and cheeks)
Lacrimal bones (2, medial wall of the orbit)
Mandible (1, lower jaw)
14 facial bones protect and support entrances to digestive and respiratory tracts.
9 of which form the structure of the nasal cavity, which we said has a complicated anatomy that can only be viewed by dissecting the skull apart.
The exception maybe being the palatine bones which we said form the posterior portion of the hard palate.
Lacrimal bones are the smallest of the facial bones.
The remaining bones are the maxillary bones that form the upper jaw, the zygomatic bones that form the cheeks, and the mandible or jawbone where the lower teeth insert.
There are additional pictures of these in your textbook.

32. The Facial Bones of the Skull
The Hyoid Bone
Functions of the hyoid bone
Supports the ______
Attaches muscles of the larynx, pharynx, and tongue
The hyoid bone is unusual because it doesn’t contact another bone.
Fig 7-12

33. The Orbital Complex Fig 7-13 The frontal bone forms the roof.
The maxilla forms the floor.
The maxillary, lacrimal, and ethmoid bones form the orbital rim and medial wall.
Fig 7-13

34. The Vertebral Column The spine or vertebral column
Protects the spinal cord
Supports the head and body
26 bones
24 vertebrae, the sacrum, and the coccyx
The vertebral column forms the next portion of the axial skeleton.
Fig 7-16

35. The Vertebral Column Vertebrae The neck The upper back (T1-T12)
C1 (superior) to C7 (inferior)
C1 articulates with the skull
The upper back (T1-T12)
12 __________________ vertebrae
Each articulates with one or more pair of ribs
The lower back (L1-L5)
5 ___________________ vertebrae
L5 articulates with the sacrum
Humans and most other mammals have 7 bones in the neck (cervical vertebrae), 12 bones in the thorax (thoracic vertebrae), and 5 bones in the lower back (lumbar vertebrae). The vertebrae are numbered by region from top to bottom so that C1 is the most superior vertebrae and it articulates with the skull. The cervical vertebrae are then numbered C1-C7. The thoracic from T1-T12. Each of these will articulate with one or more pair of ribs. And the lower back is made up of L1-L5. L5 will articulate with the sacrum. A good anatomist can easily distinguish which region of the body a vertebral bone comes from, because they have different structures to fulfill different tasks.

36. The Vertebral Column The Sacrum (S) and Coccyx (Co)
The fifth lumbar vertebra articulates with the ____________________
The sacrum articulates with the ____________________

37. The Vertebral Column Structure of a Vertebra
The vertebral body (________)
Transfers weight along the spine
Intravertebral discs provide flexibility and protection
The vertebral arch
Vertebral foramen encloses the _______________________
The articular processes
Lateral projections between laminae and pedicles
The vertebral column is composed of individual vertebral bones that vary considerably in shape and function. All vertebrae have 2 main parts: a hollow, dorsal neural arch, the vertebral canal, that encloses the spinal cord, and a sturdy, solid, ventral spool-shaped centrum. The weight of the body is supported by the vertebral centra, which are stacked up upon each other to form a flexible column. This column is flexible because pliable intravertebral discs form cushions between each vertebral bone.
The third and more variable part you see are the articular processes.
Fig 7-18

38. The Vertebral Column Intervertebral discs are pads of cartilage that
Here we see a stack of vertebrae coming together with the superior articular facets coming in contact with the inferior articular facets of the vertebrae above them.
Notice that separating the vertebrae are intervertebral discs.
These are pads of fibrous cartilage that (1) separate the vertebral bodies, (2) absorb shock, and (3) provide flexibility.
Intervertebral discs are pads of cartilage that
(1) separate the ________________________
(2) absorb shock
(3) provide flexibility
Fig 7-18

39. Vertebral Regions Distinctive features:
Cervical vertebrae are distinctive because they possess small holes on each side of the centrum. These holes are for the passage up the neck of vertebral arteries that supply blood to the brain.
They also all have a small vertebral body because they only have to support the head.
The small vertebral body make cervical vertebrae more delicate and likely to have dislocations or fractures than the other vertebrae.
In contrast to the small bodies, they have large vertebral foramen because they allow passage of the largest part of the spinal cord.
They also have prominent dorsal spinous processes; the largest one is on the cervical vertebra number 7 (C7), which is responsible for the bump you can feel on the back of your neck. This is where we’ll transition to the thoracic vertebrae.
Distinctive features:
_____________________ for passage of vertebral arteries to brain.
Prominent dorsal spinous processes
___________ vertebral body (only have to support the head)
Large vertebral ________ (passage of largest part of spinal cord)
Fig 7-19

40. Vertebral Regions The Cervical Vertebrae Atlas (_________)
Articulates with occipital condyles of skull
Has no body or spinous process (the others do)
Has a large, round foramen within anterior and posterior arches
Because joints between all the bones of the vertebral column are flexible, you can rotate your shoulders forwards and backwards a bit. Your head, however, can be rotated from side to side much more dramatically than your shoulders. What accounts for this unusual freedom of rotation of the skull? The rotation of the skull is due to the first 2 cervical vertebrae. The first one is in direct contact with the skull and is called the atlas, after the Greek god who held the earth in his arms. This bone has a normal neural arch that encloses the spinal cord; however, the centrum for this bone is missing. So the spinal canal in this area is enclosed by a roof of bone and a floor formed only by a tough ligament that spans the middle of the atlas, which looks like a hollow circle divided in two by the ligament. The second cervical vertebrae is called the axis. It supports the atlas. It has a more normal appearance, except for an addition to its centrum. The upper face of the C2 centrum has a large spike or dens, which projects upwards from it. This dens of the axis fits into the ventral opening of the atlas above it. When you turn your head, the atlas freely rotates around the dens, allowing this easy movement. Fish and amphibians don’t have these special features and can’t rotate their heads as freely as mammals or reptiles.
Fig 7-19

41. Vertebral Regions Thoracic vertebrae (T1–T12) Have heart-shaped bodies
________bodies than in C1–C7
Smaller vertebral _________ than in C1–C7
Long, slender spinous processes
Dorsolateral surfaces of body have costal facets:
Which articulate with heads of ribs
Remember a facet is a smooth flat articular surface.
Thoracic vertebrae possess stout transverse processes that attach to and buttress the 12 ribs that join to the vertebral column. Ribs attach to the thoracic vertebrae by articulating with the transverse processes of the vertebrae, curve around to the ventral side of the body, and terminate on the breastbone, or sternum.
Fig 7-20

42. Vertebral Regions Thoracic vertebrae (T1–T12) Ribs at T1–T10
Contact costal and transverse costal facets
T1–T8 articulate with two pairs of ribs
At superior and inferior costal facets
T9–T11 articulate with one pair of ribs
T10–T12 transition to lumbar vertebrae
The thoracic vertebrae can be distinguished from other vertebrae by the presence of these facets for the articulation of ribs.
The other distinctive features of the thoracic vertebrae are the heart-shaped bodies, and the long spinous processes.
Fig 7-20

43. Vertebral Regions Lumbar vertebrae (L1–L5) ___________ vertebrae
Thicker bodies than T1–T12
Transverse processes
Slender
Project dorsolaterally
Spinous process:
Short, heavy
For attachment of lower back muscles
Fig 7-21

44. Vertebral Regions Lumbar vertebrae (L1–L5) Oval-shaped bodies
No costal or transverse costal facets (Why?)
Triangular vertebral foramen
Superior articular processes
Face up and in
Inferior articular processes
Face down and out
Larger _______ (supporting weight of upper skeleton)
Lumbar vertebrae are larger and have larger centra, which are needed to support all the weight of the upper skeleton.
The are the most massive, the widest and least mobile of the vertebrae.
Ruptured intervertebral discs are more common here because the lumbar vertebrae carry so much weight.
Fig 7-21

45. Vertebral Regions Not in new edition of textbook.
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46. Vertebral Regions
© 2009 Pearson Education, Inc.

47. Vertebral Regions
© 2009 Pearson Education, Inc.

48. The Vertebral Column Figure 7–17 Abnormal Curvatures of the Spine.
One common problem with the vertebral column is scoliosis. In scoliosis, the spine, as seen from the dorsal surface, develops an s-shaped curve rather than forming a straight line from pelvis to neck. About 2% of the population will develop scoliosis, which may sometimes require surgery to straighten the spine. There is a tendency to inherit this condition. Recently, a gene called CHD7 that affects the function of homeotic proteins has been found to contribute to the development of scoliosis. (Homeotic proteins are DNA-binding proteins expressed in stripes along the body during embryogenesis and force the cells that they control to become structures appropriate for that segment). This has got to be a future target for RNAi therapeutics.

49. Vertebral Regions The __________________
Is curved, more in males than in females
Protects reproductive, urinary, and digestive organs
Attaches
The axial skeleton to pelvic girdle of appendicular skeleton
Broad muscles that move the thigh
The adult sacrum
Consists of five fused sacral vertebrae
Fuses between puberty and ages 25–30
Leaving transverse lines

50. Vertebral Regions The __________________
Attaches ligaments and a constricting muscle of the anus
Mature coccyx
Consists of three to five fused coccygeal vertebrae
So unlike the other vertebrae the vertebrae of both the sacum and coccyx are fused.
Fig 7-21

51. Vertebral Regions Ilium Ischial bone Pubis Acetabulum
Ishial tuberosity
Pubis
Acetabulum
The axial skeleton ends here. The sacrum is a triangle-shaped mass of bone that arises from the fusion of 5 sacral vertebrae. It is connected on each side by ligaments to fan-shaped bones of the pelvis called the iliac bones. This arrangement is ingenious, since a great load on the sacrum wedges it harder into the pelvis and causes the iliac bones to move closer together for better load-bearing. The iliac bones are joined to two other pelvic bones. The ischial bones on each side have downward-projecting, rounded processes called ishial tuberosities (these are what we sit on). More ventrally, the pubic bones of each side come together to form the front of the pelvic basin. The bones of the thighs insert into a cup-shaped depression, the acetabulum (ass-ah-tab-u-lum), that transmits forces from the six pelvic bones to the two thigh bones.

52. The Thoracic Cage The skeleton of the chest The Rib Cage
Supports the thoracic cavity
Consists of:
thoracic vertebrae
ribs
sternum (breastbone)
The Rib Cage
Formed of ribs and sternum
Ribs 1–7 (true ribs) They are connected to the sternum by costal cartilages
Ribs 8–12 (false ribs) They do not attach directly to the sternum
We can see that ribs 8-10 fuse together and merge with cartilage before reaching the sterum
We can also see that ribs only connect to the vertebrae and back muscles. They do not connect with the sternum.
Fig 7-23a

53. The Thoracic Cage Functions of the Thoracic Cage
Protects organs of the thoracic cavity
Heart, lungs, and thymus
Attaches muscles
For respiration
Of the vertebral column
Of the pectoral girdle
Of the upper limbs
Fig 7-23b

54. The Thoracic Cage Ribs Are mobile Can absorb shock Functions of ribs
Rib movements (breathing):
affect width and depth of thoracic cage
changing its volume
Fig 7-24c

55. The Thoracic Cage Ribs 1–7 (true ribs) Ribs 8–12 (false ribs)
Vertebrosternal ribs
Connected to the sternum by __________ cartilages
Ribs 8–12 (false ribs)
Do not attach directly to the sternum
_________________________ribs (ribs 8–10)
Fuse together
Merge with cartilage before reaching the sternum
___________________ or vertebral ribs (ribs 11–12)
Connect only to the vertebrae and back muscles
Have no connection with the sternum
Ribs 1–7 (true ribs) They are connected to the sternum by costal cartilages. Costal is Latin for rib.
Ribs 8–12 (false ribs) They do not attach directly to the sternum
We can see that ribs 8-10 fuse together and merge with cartilage before reaching the sterum
We can also see that ribs only connect to the vertebrae and back muscles. They do not connect with the sternum.

56. The Thoracic Cage Structures of the Ribs The head (capitulum) The neck
At the vertebral end of the rib
Has superior and inferior articular facets
The neck
The short area between the head and the tubercle

57. The Thoracic Cage Structures of the Ribs The tubercle (tuberculum)
A small dorsal elevation
Has an auricular facet that contacts the facet of its thoracic vertebra (at T1–T10 only)
The tubercular body (shaft)
Attaches muscles of the pectoral girdle and trunk
Attaches to the intercostal muscles that move the ribs

58. The Thoracic Cage
Let’s talk about some structures of the ribs.
Notice the head is at the vertebral end of the rib and it has superior and inferior articular facets.
The neck is the short area between the head and the tubercle (the small rounded projection where a tendon or ligament can attach).
The tubercle has a facet that contacts the facet of its thoracic vertebra in T1-10.
The body or shaft attaches muscles of the pectoral girdle and trunk and the muscles that move the ribs.
Fig 7-24

59. The Thoracic Cage The sternum A flat bone
In the midline of the thoracic wall
Three parts of the sternum
The __________
The sternal body
The xiphoid process
Mah-new-bree-um
The sternum doesn’t completely fuse or ossify until about age 25 and the xiphoid process is the last part to fuse.
The xiphoid process is also the easiest to break which can cause injury to nearby organs, so position those hands correctly while doing CPR.
- articulates with the clavicles & 1st ribs
- attaches to costal cartilages of ribs 2-7
- attaches to diaphragm and rectus abdominis muscles