Laboratory Syllabus

Thoracic Cavity & Mediastinum
 


Objectives:
Upon completion of this session, the student will be able to:

1. To study the thoracic cage, which is formed by the sternum, the ribs and the thoracic vertebrae.
2. To study the thoracic cavity, and define its contents.
3. To understand the concept of the mediastinum, and define its divisions & their contents.
4. To study the great vessels and to learn their relationships to each other and to the other structures in
     the superior mediastinum.
5. Defiine the pericardial cavity


Summary of Dissection Procedure
Shearer's Manual of Hunam Dissection - Thorax p.95-98; Mediastinum& Pericardium p.102-109

1. Clean and study the external, internal and innermost intercostal muscles of the thorax.
2. Identfy an intercostal neurovascular bundle.
3. Define the thoracic cavity.
4. Open the anterior thoracic wall as described (p. 98).
5. Define the mediastinum.
6. Clean and study the great vessels of the superior mediastinum.
7. Open the pericardial sac and study the pericardial membranes..
8. Explore the pericardial cavity and its recesses.


Materials to be learned:

1. Surface Anatomy

a. Identify on a skeleton and where possible on the cadaver,
             1. the jugular notch
             2. the clavicle
             3. the sternal angle about 5 cm below the jugular notch
             4. the second intercostal space below the second rib.
       The second rib articulates with the sternum at the angle via the second costal cartilage.
             5. the mid-clavicular line
             6. the midsternal line
             7. the xiphoid process
             8. the costal arch
             9. and the trachea above the jugular notch
b. Cardiac surface projections
            1. Outline the heart over the chest wall   (see Essential Cliniical Anatomy pp. 104)

Where on the chest wall are the heart valves located and where are the heart sounds are best heard by auscultation?


2. Osteology
a. Review the sternum and its three parts.
b. Study the 12 ribs.
Each rib has a head, neck, and shaft. The first seven ribs are connected to the sternum via their costal cartilages and are called true ribs. The remaining five ribs are called false ribs, and the eighth, ninth and tenth join the costal cartilages immediately above. The eleventh and twelfth ribs are free and are called floating ribs.
c. Study the typical thoracic vertebrae and their method of articulation with the heads of the ribs.

3. Musculature
a. external intercostal muscles & membrane
           11 pairs - inferoanteriorly from rib above to rib below
b. internal intercostal muscles & membrane
           11 pairs - inferoposteriorly from rib above to rib below
c. innermost intercostal muscle
d. transversus thoracis muscle
                   What is the function of the intercostal muscles?

4. Arteries and Nerves
a. Internal thoracic (mammary) artery
             a. musculophrenic artery
             b. superior epigastric artery
b. intercostal arteries and veins
             a. anterior - from where?
             b. posterior - from where?
What is the relationship of the intercostal veins to the azygos vein?
c. intercostal nerves - 12 pairs
             a. T1 to T11 are intercostal
             b. T12 is subcostal
What is the relationship of an intercostal vein, artery, and nerve?

5. Thoracic cavity
a. superior and inferior thoracic apertures
b. contents
           1. two pleural sacs, each enclosing a lung
           2. the mediastinum

6. Mediastinum
a. Subdivisions          How are the subdivisions of the mediastinum structured?
             a. superior
             b. anterior and posterior
             c. middle - content?
b. Superior Mediastinum
1.  thymus
2.  superior vena cava
            right and left brachiocephalic veins
                  internal jugular veins
                  subclavian veins
3. ascending, arch and descending aorta
              brachiocephalic artery (not paired)
              common carotid arteries
              subclavian arteries
4. pulmonary trunks
              ligamentum (ductus) arteriosus
     What is the fetal significance of the ductus arteriosus?
5. nerves
           a. phrenic nerves (C4)
           b. vagus nerves             
           c. autonomics (sympathetic & parasympathetic)
                     cardiac & pulmonary plexuses
          d. recurrent laryngeal nerves -Why are they recurrent?
7. Pericardium
a. The pericardium surrounds the heart and proximal portion of the great vessels.
    This fibroserous sac is composed of two layers:
                 (1) parietal pericardium
                          a. an outer fibrous layer
                          b. an inner serous layer
                  (2) visceral pericardium
                          a. reflected onto the heart and great vessels

b. Pericardial reflections
                  (1) the oblique sinus - posterior to the heart
                  (2) the transverse sinus - posterior to the ascending aorta and pulmonary trunk

c. Arteries of the pericardium
                  (1) pericardiophrenic  From where does this artery arise?
                  (2) musculophrenic branches to the base of the heart

          What is pericarditis?               Cardiac tamponade?

List of Items to Identify