Vertebral Column and Thoracic Cage

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Vertebral Column and Thoracic Cage Powered By Docstoc
					      Human Anatomy
A Laboratory Manual and Study Guide




                      By
               Brian K. Hoey MS
               Columbia College
                 Columbia MO


      Used with Permission from the Author




                      22
 Chapter III
Vertebral Column
      and
  Thoracic cage
                                   Vertebral anatomy and
- Vertebral Anatomy                    Thoracic cage
vCervical vertebrae        The human skeleton is comprised of 206
vThoracic Vertebrae        bones.      The skeletal system can be
vLumber Vertebrae          divided into the axial skeleton (80
vSacrum                    bones) and appendicular skeleton (126
vCoccyx                    bones). The axial skeleton is comprised
                           of the skull (and ear ossicles), vertebral
- Thoracic Cage            column, thoracic cage and hyoid bone.
                           In taking a regional approach to
vClavicle                  anatomy, it is logical to examine one
vSternum                   area at a time. Therefore, we will study
vRibs                      the vertebrae, and thoracic cage here and
                           follow in chapter 4 with muscles of the
                           back. In chapter four, we will begin to
                           see how muscles and ligaments attach to
                           the bones we will be studying here. In
                           chapter 8, we will study the skull to
                           complete the axial skeleton and follow in
                           chapter eight with the muscles of the
                           head and neck that attach to the skull.


                      23
                                         Skeletal system
                                           206 Bones
                Axial Skeleton                                  Appendicular Skeleton
Skull and associated bones            29            Pectoral girdle                  4
Vertebral Column                      26            Upper limbs                     60
Thoracic cage                         25            Lower Limbs                     60
                                   80 Bones         Pelvic girdle                    2
                                                                                 126 bones


                                        Bone Markings:

Openings and Depressions: Serve as passageways.


      foramen               a hole
      fissure               a cleft
      fossa                 a small pit or depression
      sulcus                a groove
      meatus                a canal
      sinus                 a cavity

Processes: Are projections.

   Those that form joints:

           head                a large rounded process
           condyle             a large process
           facet/fovea         a smooth, flat process

   Those that serve as points of attachments for muscles, tendons, and ligaments:


           tubercle           a small, rounded process
           tuberosity         a large, rounded, roughened process
           trochanter         a large, blunt, roughened process (only found in femur)
           epicondyle         a roughened process
           crest              a prominent ridge
           line               a less prominent ridge
           spine              a sharp, slender process




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                                   Vertebral Column

The spinal cord is enclosed in a protective boney column termed the vertebral column. The
vertebral column has evolved not only for protection but to provide a place for ligament and
muscle attachment. The vertebral column is made up of individual irregular bones or vertebrae.
Each vertebrae is designed to articulate with the vertebrae above or below and has very specific
points of ligament and muscle attachment that allow the vertebral column to rotate and bend.

The fetal vertebral column is made up of between 33 and 35 vertebrae, several of which fuse to
total 26 in the adult. The vertebral column is divided into five regions:



Cervical   7                       neck                                               C1-C7
Thoracic 12                        chest/rib attachment                               T1-T12
Lumbar     5                       lower back                                         L1-L5
Sacral     5 fused vertebrae       articulates laterally with os coxa (hip joint)     1 sacrum
Coccygeal 3-5 fused vertebrae      articulates inferiorly with sacrum ("tail bone")   1 coccyx


Exercise:Use the skeleton to identify these areas of the vertebral column



Each category of vertebrae contain their own seperate markings that make them unique.
However, typical vertebrae contain (figure 3.1a):

       1. Body- The largest portion of the vertebrae, disc shaped, bears the "weight" of the
                vertebral column, separated by discs.

       2. Vertebral arch - Extends posteriorly from the body and surrounds the spinal cord.
                          The vertebral arch is formed by two structures.

              A. Pedicles (PED-i-kuls) - project posteriorly and form the lateral walls of the
                                         vertebral arch. Each contain a superior and inferior
                                         vertebral notch that when fitted together by successive
                                         vertebrae, form the intervertebral foramina.

                       1. Intervertebral foramina - formed by superior and inferior vertebral
                                                    notches of successive pedicles, impart a
                                                    passageway for exiting spinal nerves.




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               B. Laminae (LAM-i-ne) - form the posterior wall of the vertebral arch. Laminae
                                       from each side of the vertebrae join to form the
                                       spinous process.

The foramen or hole that is created by the vertebral arches is termed the vertebral foramen. It is
the vertebral foramen that combine to form the vertebral canal which transmits the spinal cord.

The junction between the lamina and the pedicle provides an area for several unique landmarks.
A total of seven (6) processes arise from this junction. One (1) process arises from the joining of
the two laminae.


       1. Spinous process (1)- Arises from the joining of the two laminae and projects
                               posteriorly from the vertebra. (this can be felt as the "bumps"
                               traveling down your back). The spinous process provides an
                               area for ligament and muscle attachment.

       2. Transverse process (2) - Arise laterally from the junction of the lamina with the
                                   pedicle. Transverse processes provide areas for ligament
                                   and muscle attachment.

       3. Articular process (4) - Two (2) inferior and Two (2) superior arise from the junction
                                  of the lamina with the pedicle. Articular processes are
                                  coated with hyline cartalige to form articulating joints with
                                  other vertebrae.




                                     Figure 3.1a A typical vertebrae




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Although vertebrae have the same basic design described above, note that each of the different
types of vertebrae, cervical, thoracic, lumbar, etc. have their own unique markings that impart
specific function to the vertebrae.


1. Cervical vertebrae (7)-

   Cervical vertebrae are different from all other vertebrae in that they contain transverse
   foramina in their transverse processes. These foramina are present to transmit blood vessels
   and spinal nerves to and from the cranium.

   The first two cervical vertebrae, the atlas (C1) and the axis (C2) are unique in that they are
   different from any other vertebrae. The atlas (C1) and the axis (C2) are designed for rotation
   in that the atlas rotates around the axis as in turning the head.

       A. Atlas - First cervical vertebrae (C1):

           1. Anterior arch - anterior wall of the vertebral foramen.

           2. Posterior arch - posterior wall of the vertebral foramen.

           3. Lateral mass - side wall of the vertebral foramen.

                      a. superior articular surface (facet) - homologous to superior articular
                                                              process. This flattened area on
                                                              the atlas articulates with condyles
                                                              of the skull for up and down head
                                                              motion as in indicating "yes".

                      b. inferior articular surface (facet) - homologous to inferior articular
                                                              process. Articulates with the axis
                                                              (C2) below.

       B. Axis (C2) - the second cervical vertebrae includes most of the structures above,
                       however it contains one unique structure which arises superiorly, the dens
                       or odontoid process.

               1. Odontoid process (dens) -        Superior projection articulates with the atlas
                                                   anteriorly inside the vertebral foramen. This
                                                   articulation affords the atlas a means for rotation
                                                   around the odontoid process (dens) as in
                                                   indicating "no".

               Note: The superior and inferior articular surfaces (facets) on the axis simply
                    articulate with the vertebrae above or below respectively.


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      C. Cervical vertebrae 3-6 (C3-C6) - are not as unique as the atlas and axis to afford
                                          themselves separate names. These vertebrae
                                          contain all of the typical features of cervical
                                          vertebrae mentioned above. However one
                                          landmark indicative of these vertebrae is that their
                                          spinous processes are bifid (have two equal lobes
                                          seperated by a median cleft).

      D. Cervical vertebrae 7 (C7) (vertebrae prominens) - Contains a non-bifid and long
                                     spinous process resembling a thoracic vertebrae. The
                                     transverse foramina of the vertebrae prominens are either
                                     reduced or absent. Ligaments attach C7 to the skull
                                     creating a strong articulation among all of the cervical
                                     vertebrae. This articulation can be compared to a string
                                     on a bow. It is this strength that maintains the cervical
                                     curvature and limits the amount of slippage between the
                                     bodies as would happen during "whiplash.”

2. Thoracic vertebrae (12) -

   Thoracic vertebrae are characterized by a long pointed spinous process that projects
   downward. These vertebrae are equipped with facets that articulate with each of the twelve
   (12) ribs (figure 3.1b).




                               Figure 3.1b Thoracic vertebra attached to rib
                                             (superior view)


      A. Facet for the head of the rib - Found on the body. The Facet for the head of the rib
                                         in actuality is created by the union of the vertebrae
                                         above with the vertebrae below. As such, the
                                         markings found on the body of the thoracic vertebrae
                                         are termed demifacets. There then exists a superior
                                         demifacet and an inferior demifacet.




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      B. Facet for the tubercle (TOO-ber-kul) of the rib - Found on the transverse process.
                                                           often called the transverse costal
                                                           facet.

3. Lumbar vertebrae (5) -

   The largest of the vertebrae. Large body bears most of the weight. Spinous processes are
   broad, blunt or rounded and pointed posteriorly for massive back muscle attachment. The
   superior articular processes are directed medially instead of superiorly and the inferior
   articular processes are directed laterally not inferiorly for greater support and less mobility.

4. Sacrum (1) -

   The sacrum is composed of five fused vertebrae. Its broad structure provides an attachment
   for many massive muscles of the thigh as well as attaches the axial skeleton to the pelvic
   girdle via paired articulations.

   The sacrum itself has many unique bone markings.

      A. Transverse lines - Areas where vertebrae have fused together.

      B. Anterior (pelvic) sacral foramina - Transmit blood vessels and nerves and are
                                             continuous with posterior (dorsal) sacral
                                             foramina.

      C. Posterior (dorsal) sacral foramina - Transmit blood vessels and nerves and are
                                              continuous with anterior (pelvic) sacral
                                              foramina.

      D. Median sacral crest - Spinous processes of fused vertebrae. Point of muscle
                               attachment.

      E. Lateral sacral crest - Transverse processes of fused vertebrae. Point of muscle
                                 attachment.

      F. Auricular (o-rik-ya-ler) surface - Articulates with the ilium of the os coxa.

      G. Sacral canal - Continuation of vertebral canal (vertebral foramen of fused vertebrae).

      H. Sacral promontory - Anterior, superior projecting border.

      I. Sacral hiatus (hi-a'tes) - Inferior entrance to the sacral canal. Bordered by the sacral
                                    cornu, which are projections caused by the laminae of S5 and
                                    S6 failure to meet.



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5. Coccyx - (KOK-siks) ("tail bone") 3-5 fused vertebrae. Vertebrae usually do not completely
                       fuse until age 26. Coccyx usually completely fuses with sacrum in
                       elderly people.




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                                      Sternum and Ribs

The anatomy of the thorax consists of the sternum and ribs. Most of the ribs are attached to the
sternum via costal cartilage. The ribs articulate with the thoracic vertebrae posteriorly to
complete the thoracic cage. The thoracic cage serves two functions, the first of which being
protection. The thoracic cage protects such organs as the lungs, heart and thymus gland.
Secondly, the thoracic cage serves as an attachment point for muscles of respiration, the vertebral
column and of the pectoral girdle and upper extremity. The thoracic cage is made up of

1. Sternum - (breastbone) flat bone consisting of three parts:

   A. Manubrium (ma-NOO-bre-um)- Quadrangular, superior portion. Articulates directly
                                 with the clavicle and the costal cartilage of the first pair
                                 of ribs.

       1. Clavicular notches - Articular surfaces on the superior, lateral portion of the
                               manubrium. Articulate with the clavicles.

       2. Jugular (suprasternal) notch - Depression on the superior surface of the manubrium
                                         between the clavicular notches.

       3. Sternal angle - Junction between the manubrium and body.

   B. Body - attaches to the inferior surface of the manubrium at the sternal angle and extends
             caudally along the midline. The body provides an attachment point for the
             individual costal cartilages of rib pairs 2-7. Rib pairs 8-10 attach to the body via a
             single shared pair of costal cartilages.

   C. Xiphoid (ZI-foyd) process - inferior, smallest part of the sternum. Provides a muscle
                                  attachment for the diaphragm and rectus abdominis muscles.

2. Ribs (12 pairs) - Ten (10 ) of which attach to the sternum via costal cartilage. The inferior
                     two (2) pairs of ribs do not articulate with the sternum or costal cartilage and
                     are considered floating ribs. The parts of a typical rib include:

       A. Body - shaft, main part of the rib

       B. Head - posterior projection. Contains facets that allow for the attachment of the rib to
                the thoracic vertebrae.

               1. Superior facet - Articulates with the demifacet on the superior vertebrae.
               2. Inferior facet - Articulates with the demifacet on the inferior vertebrae.




                                                 30
       C. Neck - Constricted area after the head. Positioned anterior, lateral to the head when
                  attached to the sternum.

       D. Tubercle (TOO-ber-kul). Elevation below the neck. Articular part articulates with
                                  the facet for the tubercle of the rib on the transverse
                                  processes of the thoracic vertebrae. Also contains a
                                  nonarticular part for ligament attachment.

       E. Costal groove - Depression on the inner surface of the rib. Provides a pathway for
                          intercostal vessels and nerves.

There exists three (3) types of ribs, each of which contain the basic structures illustrated above.
The twelve (12) rib pairs are categorized into groups based on their sternal attachment.

       1. True ribs (vertebrosternal)- Attach directly to the sternum by their own costal
                                       cartilage. True ribs include rib pairs 1-7.

       2. False ribs (vertebrochondral) - Do not attach directly to the sternum by their own
                                          costal cartilage. Rib pairs 8-10 fuse with the costal
                                          cartilage of the rib above, creating a single attachment
                                          to the sternum.

                      Floating ribs (vertebral) – Rib pairs 11-12 have no attachment to the
                       sternum. Floating ribs are in fact free at their anterior ends.




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Objectives:

1. Locate a typical vertebrae and find the following structures:


    pedicles                   transverse processes            superior articular process         laminae
    vertebral foramen          body                            spinous process                    vertebral arch


   Label these structures on figure 3.2

2. Locate two (2) successive vertebrae, place them one on top of the other and notice the
   intervertebral foramina.

   Label these structures on figure 3.3

3. Locate the atlas (C1) and find the following structures:

    anterior arch                 superior articular surface         transverse processes
    posterior arch                inferior articular surface         transverse foramen
    vertebral foramen             lateral mass


   Label these structures on figure 3.4

4. Locate the axis (C2) and find the following structures:

     odontoid process (dens)           superior articular surface               transverse processes
     body                              inferior articular surface               transverse foramen
     vertebral foramen                 lateral mass


   Label these structures on figure 3.5

5. Locate a cervical vertebra (C3 - C6). Notice the bifid spinous process. Find the following
   structures:

    pedicles            transverse processes          superior articular process            vertebral notch
    laminae             transverse foramen            inferior articular process            vertebral foramen
    body                spinous process (bifid)       vertebral arch



   Label these structures on figure 3.6

6. Locate C7 vertebrae prominens. Notice the non-bifid spinous process and its resemblance to
   a thoracic vertebrae.




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7. Locate a thoracic vertebra and find the following structures:

     pedicles                            transverse processes            superior articular process          vertebral notch
     laminae                             spinous process                 inferior articular process          vertebral foramen
     body                                vertebral arch                  superior demifacet                  inferior demifacet
     facet for the head of the rib                                       facet for the tubercle of the rib

   Label these structures on figure 3.7 and 3.3

8. Locate two successive thoracic vertebrae. Place the two vertebrae one on top of the other and
   notice how the demifacets align to form the facet for the head of the rib. Place a the head of
   a rib here, articulate the tubercle of the rib with the transverse process. Notice how the rib
   points downward. Observe this on the articulated skeleton.

9. Locate a lumbar vertebra and find the following structures:

     pedicles           transverse processes              superior articular process        vertebral notch
     laminae            vertebral arch                    inferior articular process        vertebral foramen
     body               spinous process

   Notice the massive size of the vertebrae, the broad spinous process, the positioning of the
   articular surfaces and the reduced vertebral foramen.

   Label these structures on figure 3.8

10. Locate a sacrum and find the following structures:

   posterior (dorsal) sacral foramen              median sacral crest             transverse lines
   anterior (pelvic) sacral foramen               lateral sacral crest            auricular surface
   sacral promontory                              sacral canal                    sacral hiatus
   coccyx

   Label these structures on figure 3.9

11. Locate a sternum and find the following structures:

    manubrium           body         xiphoid          clavicular notches             jugular notch           sternal angle

   Label these structures on figure 3.10

   Notice the attachment point for the first pair of ribs and clavicle. Observe the individual
   costal cartilages for each of the first seven (7) rib pairs. Notice that rib pairs 8-10 share costal
   cartilage and that there is no costal cartilage for rib pairs 11 and 12.

   Label the true, false, and floating ribs on figure 3.10

12. Locate a rib and find the following structures:
     head        neck      tubercle       angle       body         superior facet         inferior facet      costal groove



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Questions:

1.    A spinous process is created by the union of two ____________.

2     There are ____ cervical vertebrae
      There are ____ thoracic vertebrae
      There are ____ lumbar vertebrae

3.    The sacrum is created by the fusion of ___ vertebrae.

4.    Cervical vertebrae 3-6 are unique in that their spinous processes are ___________.

5.    The first cervical vertebrae is termed the ___________.

6.    C7 is also known as __________________________.

7.    The first pair of ribs attach to the sternum at the ________________.

8.    The _________ vertebrae form the thoracic cage with the ribs

9.    The diaphragm muscle attaches to the ____________ of the sternum.

10. The largest of the vertebrae are the _____________ vertebrae.

Matching:

11.   transverse foramina                                     a.   3-5 fused vertebrae
12.   axis                                                    b.   manubrium
13.   jugular notch                                           c.   dens
14.   pedicle                                                 d.   cervical vertebrae
15.   coccyx                                                  e.   vertebral notch

Short answer:

16. Define true rib.


17. Define false rib.


18. Define floating rib.




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Figure 3.2 A typical vertebrae superior view




Figure 3.3 Two successive thoracic vertebrae




                    35
Figure 3.4a atlas superior view                                    Figure 3.4b atlas inferior view




Figure 3.5a axis superior view                                     Figure 3.5b axis inferior view




                                  Figure 3.5c axis anterior view




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                                    Figure 3.6 cervical vertebrae superior view




Figure 3.7b Thoracic vertebrae superior view                          Figure 3.7b Thoracic vertebrae lateral view




                                                        37
Figure 3.8a lumbar vertebrae superior view                       Figure 3.8b lumbar vertebrae lateral view




                                      Figure 3.10 the thoracic cage




                                                   38
                            Figure 3.9 the sacrum and coccyx




Figure 3.9a sacrum posterior view



                                                               Figure 3.9b sacrum lateral view




                                                                Figure 3.9d coccyx lateral view




Figure 3.9c sacrum anterior view




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                         Vertebral Column and Thoracic cage
                    1

                    2

                                                         3

                                                    4

                                5         6                       7




                    8

                                                    9        10




                                11            12




                    13




                                14


Across
2. C7
5. make up lateral wall of vertebrae
8. number of cervicle vertebrae
9. ___ on rib articulates with transverse process
12. clavicle articulates with
13. made up of five fused vertebrae
14. diaphragm inserts on ______
Down
1. posterior projection on vertebrae
3. ___ are the largest of the vertebrae
4. last two ribs
6. superior projection on C2
7. number of lumbar vertebrae
10. structures that make up spinous process
11. tail bone



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