Skeleton: Axial

1
Skeleton Axial

• Lab 4

2
Classification of Bones

• Human body consists in 206 bones. They are
  divided in two groups
• Axial skeleton (form the long axis of the body)
  includes bones of the skull, vertebral column,
  and rib cage. Functions protecting, supporting
  or carry other body parts.
• Appendicular skeleton bones of the upper and
  lower limbs, shoulder, and hip. Function
  locomotion and manipulation of our enviroment

3
Classification of Bones By Shape
Bones come in many sizes and shapes. For most
part , bones are classified by their shape as
long, short flat and irregular

• Long bones longer than they are wide (e.g.,
  humerus)
• Has a shaft plus two ends

Ex All limb bones except patella and wrist and
ankle bones are long bone
Figure 6.2a
4
Classification of Bones By Shape

• Short bones
• Cube-shaped bones of the wrist and ankle
• Sesamoid bones shaped like a sesame seed that
  form within tendons (e.g., patella). They vary in
  size and number in different individual. Some
  sesamoid bones act to atter the direction of pull
  of a tendon

Figure 6.2b
5
Classification of Bones By Shape

• Flat bones thin, flattened, and a bit curved
  (e.g., sternum, and most skull bones)

Figure 6.2c
6
Classification of Bones By Shape

• Irregular bones bones with complicated shapes
  (e.g., vertebrae and hip bones)

Figure 6.2d
7
Function of Bones

• Support form the framework that supports the
  body and cradles soft organs. Ex Lower limb
• Protection provide a protective case for the
  brain (bones of skull), spinal cord (vertebrae),
  and vital organs (rib cage)
• Movement provide levers for muscles
• Mineral storage bone is a reservoir for
  minerals, especially calcium and phosphorus
• Blood cell formation hematopoiesis occurs
  within the marrow cavities of bones

8
Bone Markings Projections Sites of Muscle and
Ligament Attachment

• Tuberosity rounded projection
• Crest narrow, prominent ridge of bone
• Trochanter large, blunt, irregular surface
• Line narrow ridge of bone

9
Bone Markings Projections Sites of Muscle and
Ligament Attachment

• Tubercle small rounded projection
• Epicondyle raised area above a condyle
• Spine sharp, slender projection
• Process any bony prominence

10
Chemical Composition of Bone Organic

• Bone has both organic and inorganic components.
• Organic components
• 1.-Cells
• Osteoblasts bone-forming cells
• Osteocytes mature bone cells
• Osteoclasts large cells that resorb or break
  down bone matrix
• 2.- Osteoid unmineralized bone matrix composed
  of proteoglycans, glycoproteins, and collagen

11
The Skeleton

• The skeleton (dried up body or mummy)
• It is strong, yet light, and almost perfectly
  adapted for the protective, locomotor and
  manipulative functions it perform
• Composed of bones, cartilages, joints and
  ligaments, accounts for about 20 of body mass.
• The skeleton is divided into Axial and
  Appendicular

12
The Axial Skeleton

• This part of skeleton supports the head, neck and
  trunk and it protects the brain, spinal cord and
  the organs in the thorax
• Eighty bones segregated into three regions
• 1.- Skull
• 2.- Vertebral column
• 3.- Bony thorax

13
The Skull

• The skull, the bodys most complex bony
  structure, is formed by the cranium and facial
  bones
• Cranium protects the brain and is the site of
  attachment for head and neck muscles
• Facial bones
• Supply the framework of the face, the sense
  organs, and the teeth
• Provide openings for the passage of air and food
• Anchor the facial muscles of expression

14
Anatomy of the Cranium

• The cranium can be divided in
• 1.- cranial vault (calvaria)
• 2.- cranial base (floor)
• Eight cranial bones two parietal, two temporal,
  frontal, occipital, sphenoid, and ethmoid
• Cranial bones are thin and remarkably strong for
  their weight

15
Frontal Bone

• Forms the anterior portion of the cranium
• Articulates posteriorly with the parietal bones
  via the coronal suture
• The most anterior part of the frontal bone is the
  vertical frontal squama, commonly called the
  forehead
• Major markings include the supraorbital margins,
  the anterior cranial fossa, and the frontal
  sinuses (internal and lateral to the glabella)

16
Skull Anterior View
Figure 7.2a
17
Skull Posterior View
Figure 7.2b
18
Parietal Bones and Major Associated Sutures

• They are curved, rectangular bones. Form most of
  the superior and lateral aspects of the skull

Figure 7.3a
19
Occipital Bone and Its Major Markings

• It articulates anteriorly with the paired
  parietal and temporal bones via the lambdoid and
  occipitomastoid sutures.
• It also joins with the sphenoid bone in the
  cranial floor via a plate called the pharingeal
  tubercule.
• Forms most of skulls posterior wall and base
• Major markings include the posterior cranial
  fossa, foramen magnum, occipital condyles, and
  the hypoglossal canal

Figure 7.2b
20
Temporal Bones

• Between the styloid and mastoid processes exist
  the stylomastoid foramen that allow cranial nerve
  VII to leave the skull.
• The mastoid region of the temporal bone exhibits
  the conspicuous mastoid process, an anchoring
  site for some neck muscles

Figure 7.5
21
Sphenoid Bone
Figure 7.6a, b
22
Ethmoid Bone
Allow the olfatory nerves to pass from the smell
receptors in the nasal cavites to the brain
Figure 7.7
23
Mandible and Its Markings
Figure 7.8a
24
Maxillary Bone
The anterior nasal spine allows the infraorbital
nerve and artery to reach the face
Figure 7.8b
25
Vertebral Column Ribs
26
Vertebral Column

• Formed from 26 irregular bones (vertebrae)
  connected in such a way that a flexible curved
  structure results
• Cervical vertebrae 7 bones of the neck
• Thoracic vertebrae 12 bones of the torso
• Lumbar vertebrae 5 bones of the lower back
• Sacrum bone inferior to the lumbar vertebrae
  that articulates with the hip bones

27
Vertebral Column
Figure 7.13
28
Vertebral Column Curvatures

• Posteriorly concave curvatures cervical and
  lumbar
• Posteriorly convex curvatures thoracic and
  sacral
• Abnormal spine curvatures include scoliosis
  (abnormal lateral curve), kyphosis (hunchback),
  and lordosis (swayback)

29
Vertebral Column Ligaments

• Anterior and posterior longitudinal ligaments
  continuous bands down the front and back of the
  spine from the neck to the sacrum
• Short ligaments connect adjoining vertebrae
  together

30
Vertebral Column Ligaments
Figure 7.14a
31
Vertebral Column Intervertebral Discs

• Cushionlike pad composed of two parts
• Nucleus pulposus inner gelatinous nucleus that
  gives the disc its elasticity and compressibility
• Annulus fibrosus surrounds the nucleus pulposus
  with a collar composed of collagen and
  fibrocartilage

32
Vertebral Column Intervertebral Discs
Figure 7.14b
33
General Structure of Vertebrae

• Body or centrum disc-shaped, weight-bearing
  region
• Vertebral arch composed of pedicles and laminae
  that, along with the centrum, enclose the
  vertebral foramen
• Vertebral foramina make up the vertebral canal
  through which the spinal cord passes

34
General Structure of Vertebrae

• Spinous processes project posteriorly, and
  transverse processes project laterally
• Superior and inferior articular processes
  protrude superiorly and inferiorly from the
  pedicle-lamina junctions
• Intervertebral foramina lateral openings formed
  from notched areas on the superior and inferior
  borders of adjacent pedicles

35
General Structure of Vertebrae
Figure 7.15
36
Cervical Vertebrae

• Seven vertebrae (C1-C7) are the smallest,
  lightest vertebrae
• C3-C7 are distinguished with an oval body, short
  spinous processes, and large, triangular
  vertebral foramina
• Each transverse process contains a transverse
  foramen

37
Cervical Vertebrae
Table 7.2
38
Cervical Vertebrae The Atlas (C1)

• The atlas has no body and no spinous process
• It consists of anterior and posterior arches, and
  two lateral masses
• The superior surfaces of lateral masses
  articulate with the occipital condyles

39
Cervical Vertebrae The Atlas (C1)
Figure 7.16a, b
40
Cervical Vertebrae The Axis (C2)

• The axis has a body, spine, and vertebral arches
  as do other cervical vertebrae
• Unique to the axis is the dens, or odontoid
  process, which projects superiorly from the body
  and is cradled in the anterior arch of the atlas
• The dens is a pivot for the rotation of the atlas

41
Cervical Vertebrae The Axis (C2)
Figure 7.16c
42
Cervical Vertebrae The Atlas (C2)
Figure 7.17a
43
Thoracic Vertebrae

• There are twelve vertebrae (T1-T12) all of which
  articulate with ribs
• Major markings include two facets and two
  demifacets on the heart-shaped body, the circular
  vertebral foramen, transverse processes, and a
  long spinous process
• The location of the articulate facets prevents
  flexion and extension, but allows rotation of
  this area of the spine

44
Thoracic Vertebrae
Figure 7.17b
45
Lumbar Vertebrae

• The five lumbar vertebrae (L1-L5) are located in
  the small of the back and have an enhanced
  weight-bearing function
• They have short, thick pedicles and laminae, flat
  hatchet-shaped spinous processes, and a
  triangular-shaped vertebral foramen
• Orientation of articular facets locks the lumbar
  vertebrae together to provide stability

46
Lumbar Vertebrae
Figure 7.17c
47
Sacrum

• Sacrum
• Consists of five fused vertebrae (S1-S5), which
  shape the posterior wall of the pelvis
• It articulates with L5 superiorly, and with the
  auricular surfaces of the hip bones
• Major markings include the sacral promontory,
  transverse lines, alae, dorsal sacral foramina,
  sacral canal, and sacral hiatus

48
Coccyx

• Coccyx (Tailbone)
• The coccyx is made up of four (in some cases
  three to five) fused vertebrae that articulate
  superiorly with the sacrum

49
Sacrum and Coccyx Anterior View
Figure 7.18a
50
Characteristics of Cervical,Thoracic and Lumbar
Vertebrae
51
Homeostatic Imbalance

• Herniated (prolapsed) disc.
• Severe or sudden physical trauma to the spine,
  may result in hernation of one or more discs. A
  herniated disc (slipped disc) usually involves
  rupture of the annulus fibrosus followed by
  protrusion of the spongy nucleus pulposus through
  the annulus (Fig 7.14). If the protrusion presses
  on the spinal cord or on spinal nerves exiting
  from the cord, numbness or excruciating pay
  result.
• Treatments moderated exercise, massage, heat
  ther. and painkillers if this fail? surgery

52
Bony Thorax (Thoracic Cage)

• The thoracic cage is composed of the thoracic
  vertebrae dorsally, the ribs laterally, and the
  sternum and costal cartilages anteriorly
• Functions
• Forms a protective cage around the heart, lungs,
  and great blood vessels
• Supports the shoulder girdles and upper limbs
• Provides attachment for many neck, back, chest,
  and shoulder muscles
• Uses intercostal muscles to lift and depress the
  thorax during breathing

53
Bony Thorax (Thoracic Cage)
Figure 7.19b
54
Sternum (Breastbone)

• A dagger-shaped, flat bone that lies in the
  anterior midline of the thorax
• Results from the fusion of three bones the
  superior manubrium, the body, and the inferior
  xiphoid process
• Anatomical landmarks include the jugular
  (suprasternal) notch, the sternal angle, and the
  xiphisternal joint

55
Ribs

• There are twelve pair of ribs forming the flaring
  sides of the thoracic cage
• All ribs attach posteriorly to the thoracic
  vertebrae
• The superior 7 pair (true, or vertebrosternal
  ribs) attach directly to the sternum via costal
  cartilages
• Ribs 8-10 (false, or vertebrocondral ribs) attach
  indirectly to the sternum via costal cartilage
• Ribs 11-12 (floating, or vertebral ribs) have no
  anterior attachment

56
Ribs
Figure 7.19a
57
Structure of a Typical True Rib

• Bowed, flat bone consisting of a head, neck,
  tubercle, and shaft

Figure 7.20