1. “The Human Axial Skeletal System”
Laboratory Exercise
“The Human Axial Skeletal System”

2. Human Skeletal System – Axial
In this exercise, you will identify bones of the axial skeleton, identify the surface markings of individual bones and learn their significance and identify the normal curves of the adult vertebral column.
These terms should be familiar to you: axial or appendicular skeleton, skull, auditory ossicles, hyoid, vertebral column, sternum, ribs, sutures, mandible, the facial and cranial bones, the cavities, vertebral discs, foramina, canal, the vertebrae, cartilage, true or vertebrosternal ribs, false ribs, vertebrochondral ribs, floating or vertebral ribs.
This laboratory exercise correlates with Chapter 7 of your textbook.

3. What procedures are we doing?
Observe the skull bones
Observe the vertebral column
Observe the thorax
Examine different bone markings

4. Resources available…
Anatomy and Physiology Laboratory Study Pages; submenu: Skeletal

5. Laboratory Lecture

6. An insight into learning bones (and anatomy)…
An Introduction to the Skeletal System
An insight into learning bones (and anatomy)…
What is the name of the bone?
What is its location in the body?
What are the bone landmarks and markings?
What is the shape of the bone?
What does the bone articulate with?

7. a quick note about nomenclature…
Bones have structural elements of importance:
Articulations are contacts with other bones (joints)
Landmarks are areas of muscle and ligament attachment (facilitates body movement)
Foramina are openings for nerves, lymphatics and blood vessels to travel through (communication and maintenance)

8. There are 206 bones in the adult human body They are divided into the:
Axial skeleton, these are the bones along the longitudinal axis of the body (80ct., 40%)
Appendicular skeleton, these are the bones of the limbs and the bones that attach the limbs to the axial skeleton (126ct., 60%)

9. Functions of the Axial Skeleton
Supports and protects organs in body cavities
Provides attachment for muscles that
Adjust movements of head, neck, and trunk
Perform respiratory or digestive (mouth/throat) movements
Stabilize or position parts of appendicular skeleton
Joints of the axial skeleton are immovable or permit very little movement

10. An Introduction to the Axial Skeleton
The Axial Skeleton has 80 bones:
The skull has
8 cranial bones
14 facial bones
7 bones are associated with the skull
6 auditory ossicles
1 hyoid bone
The vertebral column
24 vertebrae (singular = vertebra)
1 sacrum (a fused set of bones)
1 coccyx (a fused set of bones)
The thoracic cage
24 ribs
1 sternum

11. SKELETAL SYSTEM
206
APPENDICULAR SKELETON
AXIAL SKELETON 80
(see Figure 8–1) 8
Cranium
Skull 14
Face
Skull and
associated
bones
Auditory
ossicles 29 6
Associated
bones 1
Hyoid 1
Sternum
Thoracic
cage 25 24
Ribs 24
Vertebrae 1
Sacrum 26
Vertebral
column 1
Coccyx
The Axial Skeleton
An anterior view of the entire skeleton, with the axial components highlighted.
The numbers in the boxes indicate the number of bones in the adult skeleton. 11

12. Skull Cervical vertebrae Sternum Thoracic vertebrae Ribs
The Axial Skeleton.
Skull
Cervical vertebrae
Sternum
Thoracic vertebrae
Ribs
Costal cartilages
Lumbar vertebrae
Sacrum
Coccyx
Anterior (left) and posterior (right) views of the axial skeleton. The individual bones associated with the skull are not visible. b

13. The Cranial and Facial Bones of the Skull
FACE 14
CRANIUM 8
ASSOCIATED BONES 7
Maxillary bones 2
Occipital bone 1
Palatine bones 2
Parietal bones 2
Hyoid bone 1
Auditory ossicles
enclosed in
temporal bones
(detailed in
Chapter 17)
Nasal bones 2
Frontal bone 1 6
Inferior nasal
conchae 2
Temporal bones 2
Sphenoid 1
Zygomatic bones 2
Ethmoid 1
Lacrimal bones 2
Vomer 1
Mandible 1 13

14. The Cranial Bones of the Skull
The Cranial Bones are all flat bones with two exceptions, the sphenoid and ethmoid bones
Occipital bone
2 Parietal bones
Frontal bone
2 Temporal bones
Sphenoid
Ethmoid

15. The Facial Bones of the Skull
The Facial Bones (irregular bones) protect and support entrances to the digestive and respiratory tracts
2 Maxillae (maxillary bones)
2 Palatine bones
Smaller facial bones:
2 Nasal bones
Vomer
2 Inferior nasal conchae
2 Lacrimal bones
2 Zygomatic bones
Mandible
Hyoid*
*- denotes smaller bones of the face

16. Frontal*, Sphenoid*, Ethmoid*, Zygomatic, Maxillae, Lacrimal, Palatine
Cranial and Nasal Bones compose comprise the Orbital and Nasal Complexes
Orbital Complex
The orbital complex is formed by the following cranial* and facial bones…
Frontal*, Sphenoid*, Ethmoid*, Zygomatic, Maxillae, Lacrimal, Palatine 16

17. Frontal*, Ethmoid, Nasal, Palatine, Maxillae, Sphenoid
Nasal Complex
Nasal bones and paranasal sinuses compose the nasal complex
Paranasal sinuses have air cells; they reduce nasal bone weight
Paranasal sinuses also increase surface area for mucus secretion; this traps particulates (mucociliary escalator) and warms incoming air
The nasal complex is formed by the following cranial* and facial bones…
Frontal*, Ethmoid, Nasal, Palatine, Maxillae, Sphenoid

18. Fontanelles and Sutures
Fusion is not complete in the infant skull
There are two frontal bones, four occipital bones and several sphenoidal and temporal elements
Fontanelles are non-ossified areas of fibrous connective tissue between the cranial bones of the infant skull
They provide flexibility for the fetal skull as it goes through the birth canal
Allow for growth of the baby’s brain
Within 24 months after birth, the fontanelles ossify and form permanent sutures (bone)

19. The Adult Skull 19

20. Sutures: immovable joints of the skull
Coronal Suture: between the frontal and parietal bones
Lambdoid Suture: between the occipital and parietal bones
Sagittal Suture: between the two parietal bones
Squamous Suture: between the temporal and parietal bones (not shown in figure)

21. The Vertebral Column
The vertebral column (spine) protects the spinal cord. It also supports the head and the body
There are 26 irregular bones in the adult (33 in newborn)
24 vertebrae, the sacrum, and the coccyx (tailbone)
Why are there 33 irregular bones in a newborn?
There are 5 vertebral regions
Cervical (C1-7)
Thoracic (T1-12)
Lumbar (C1-5)
Sacral
Coccygeal

22. Vertebral Curves
An infant has two spinal curves (newborns are “C shaped”); adults have four curves in the spine!
Thoracic and Sacral Curves
Are called primary curves (they are present during fetal development)
They are also referred to as accommodation curves (accommodate internal organs)
Lumbar and Cervical Curves
Are called secondary curves (appear after birth)
They are also referred to as compensation curves (shift body weight for upright posture)

23. 2’ 1’ 2’ 1’ Spinal Curves Vertebral Regions The Vertebral Column 23
Primary curves develop
before birth; secondary
curves develop after birth.
Regions are defined
by anatomical
characteristics of
individual vertebrae.
The cervical curve, a
secondary curve, develops as
the infant learns to balance the
weight of the head on the
vertebrae of the neck. 2’
Cervical
(7 vertebrae)
The thoracic curve, a
primary curve,
accommodates the
thoracic organs. 1’
Thoracic
(12 vertebrae)
The lumbar curve, a
secondary curve, balances
the weight of the trunk over
the lower limbs; it develops
with the ability to stand. 2’
Lumbar
(5 vertebrae)
The sacral curve, a
primary curve,
accommodates the
abdominopelvic organs. 1’
Sacral
Coccygeal 23

24. Abnormal spinal curvatures
Scoliosis
(crooked back)
Kyphosis
(humpback)
Lordosis
(swayback)

25. Vertebral Anatomy Vertebrae have three anatomical distinctions:
The vertebral body, or centrum, transfers weight along the spine
The vertebral arch is the posterior margin of the vertebral foramen
The articular processes are lateral projections between the laminae (roof) and the pedicles (walls)

26. Spinous process: formed by fusion of the laminae, project posteriorly, for the attachment of muscles.
Transverse processes: lateral projections from the junction of the pedicles and laminae; attachment of muscles or ribs.
Superior and inferior articular facets: flat surfaces on the upper and lower surfaces for articulation with vertebra just above or just below.

27. Intervertebral foramen
Intervertebral discs
Absorb shock and allow for a strong joint and flexibility between the vertebrae
With aging, the disc becomes stiff and compressed. This results in decreased height and loss of flexibility
Intervertebral foramen
Are a pair of lateral openings formed between the adjoining vertebrae (sup. and inf. articular facets)
They are a conduit for nerves

28. The Vertebral Regions There are five regions of the vertebral column
Cervical (C7)  C1, C2, C7 are important!
Thoracic (T12)  they all look like a giraffe’s head!
Lumbar (L5)  big and bulky, bear body frame weight
Sacral (S1)  sacral fuses with coccygeal
Coccygeal (Co1)
IMPORTANT!: Vertebrae of each region have characteristics that are determined by functions (structure fits function!). Because of this, vertebrae will look slightly different depending on where they are from. Here are some highlights…

29. C1 – the “Atlas” C2 – the “Axis”
The “atlas” supports the weight of the skull
It has no true body or spinous process (compare to C2); it looks like a ring
Superior articular facets articulate with the occipital condyles of the occipital bone at the atlantooccipital joint (AOJ), which allows for nodding of the head
C2 – the “Axis”
Has a tooth like projection at the body (dens or odontoid process). It forms a pivot point with C1 that allows for the rotation of the head (transverse ligament of C1 holds it in)
In children, fusion of C1 and C2 is incomplete: impact or severe shaking can cause dislocation of the dens and severe damage to spinal cord.
This also causes damage to the spinal cord in a “whiplash” injury
AOJ
AOJ
AOJ
AOJ

30. C7 – the “vertebrae prominens”
C7 transitions from the cervical to the thoracic region. (In general, the last vertebra of one region strongly resembles the first vertebra of the next region)
It has a long, larger spinous process (not a bifid) with a broad tubercle; this forms the bump on the lower back of the neck
The ligamentum nuchae extends from C7 to the external occipital protuberance of the skull (this is an elastic ligament)

31. If you spin a thoracic vertebra around (and look at them posteriorly)…
Thoracic Vertebrae
If you spin a thoracic vertebra around (and look at them posteriorly)… 31

32. …thoracic vertebrae sorta’ look like a giraffe!
(don’t believe me; get a thoracic vertebrae and see for yourself)

33. Regional Differences in Vertebral Structure and Function
Cervical Vertebrae
Really big foramen!
Lotta’ nerves up top!
Lumbar vertebrae are big and bulky (they support body weight)! 33

34. 5 sacral vertebrae are completely fused by 25-30 years of age
4 coccygeal vertebrae are completely fused by years of age
They fuse together to form 1 bone. Crazy stuff!
sacral canal 34

35. 7-8 The Thoracic Cage The thoracic cage functions to:
Protect organs of the thoracic cavity
Heart, lungs, and thymus
Provide sites for muscle attachment
For respiration (intercostals)
For maintenance of position of the vertebral column
For movements of the pectoral girdle and the upper limbs

36. The thoracic cage links bodies of every thoracic vertebrae (from the spinal column) with the rib cage (includes ribs & sternum). [12 Thoracic vertebrae; thus, 12 ribs…]
The head of the rib attaches to the demifacet on the body of the vertebrae
The tubercle of the rib attaches to the transverse costal facet on the transverse process of the vertebrae

37. So what about ribs #11 and #12?
the sternum
The sternum is a flat bone found in the midline of the thoracic wall (breastbone); it has three parts…
The manubrium articulates with the clavicles and the cartilages of the first rib pair
The sternal body attaches to costal cartilages of ribs 2–7 and indirectly attaches to ribs The body completes fusion at about age 25
The xiphoid process does not articulate with the ribs; it attaches to the diaphragm and rectus abdominis muscle (breathing)
It is composed of hyaline cartilage that does not ossify until late aduthood
It is a palpable landmark for CPR and is often fractured during improper administration of CPR
So what about ribs #11 and #12?

38. the ribs (costae)
The ribs are 12 pairs of long, curved, flat bones (5% of the population has 13 ribs!)
They all extend from the bodies of the thoracic vertebrae
Intercostal skeletal muscles occupy the intercostal spaces (the spaces between the ribs). This, in part, facilitates the inspiration and expiration of air (respiration)
Ribs are divided into two types, depending whether they are directly, indirectly or not attached to the sternum. Huh?
True ribs (1-7)
False ribs (8-10, 11-12)

39. False ribs (8-12) attach indirectly or not at all to the sternum
True ribs (vertebrosternal ribs, 1-7) are connected to the sternum by separate costal cartilages
False ribs (8-12) attach indirectly or not at all to the sternum
Ribs 8-10 (vertebrochondral ribs) attach to the sternum indirectly; their costal cartilage fuses together and attaches to the costal cartilage of rib 7
Ribs are the floating ribs because they do not attach to the sternum; their anterior end is free

40. 40