Thorax: Thoracic Cavity and Vessels

Question 1

List and identify the boundaries of the thorax

Answer 1

1. Cranial/The thoracic inlet: the manubrium, rib 1, and T1
2. Caudal/The thoracic outlet: in short, the diaphragm. In excess, the xiphoid process, last rib, last thoracic vertebrae, and the costal arch
3. Dorsal: the thoracic vertebrae
4. Ventral:the sternum
5. Lateral: the ribs, intercostal muscles, and costal cartilages

Question 2

List the major contents of the thorax

Answer 2

Organs: heart and lungs (the thymus is an honorable mention)
Vessels:aorta, cranial and caudal vena cava, azygous vein
Lymphatics: the thoracic duct which provides lymphatic drainage. (see flashcard on thoracic lymph nodes)
Structures: Esophagus and trachea
Nerves: phrenic nerve, vagus nerve

She didn’t mention all of those lymph nodes in recitation.

Question 3

Explain and name the arrangement of pleura in the thorax

Answer 3

Pleura = lungs
* Costal pleura
* Diaphragmatic pleura
* Mediastinal pleura
* Pericardial pleura

Question 4

Understand the concepts of ‘potential space’ and negative pressure

Answer 4

Potential space is the space that exists between serosal layers where pathology can occur. These spaces also maintain negative pressure in the thoracic cavity.

Question 5

Name the muscles that act in cranial movement of the rib cage for respiration

Answer 5

1. External abdominal oblique
2. External intercostal muscles (inspiration)/ Internal intercostal muscles (expiration)
3. Tranversus thoracis
4. The diaphragm

Question 6

Describe the margins of the thoracic recesses

Answer 6

The recesses are potential spaces that do not include lung tissue.

• Costomediastinal: Between opposing mediastinal + costal pleura
• Costadiaphragmatic: Between opposing costal + diaphragmatic pleura

Question 7

Differentiate true, ‘false’ and floating ribs

Answer 7

• True ribs connect directly to sternum
• False ribs connect to the sternum via cartilage via the costal arch
• Floating ribs do not connect at all

Question 8

List the thoracic lymph nodes

Answer 8

1. trachealbronchial
2. cranial medistinal
3. cranial sternal
   + (in ungulates only)
4. caudal sternal
5. caudal medistinal

Question 9

identify on a radiograph the important structures within the thorax

Answer 9

you cannot see the esophagus on a radiograph

Question 10

Aorta Vessels

Answer 10

The aorta is split up into the
* ascending aorta: R+L coronary arteries
* transverse (aortic arch): gives rise to arteries that supply the head, thorax and forelimbs
* descending aorta (later to become the abdominal aorta): intercostal arteries 4/5-12 and bronchoesophageal artery

Question 11

Vessels off the aortic arch

Answer 11

The first vessels to branch off the aortic arch is the braciocephalic trunk to the right and the left subclavian artery to the left.
The braciocephalic trunk gives rise to the right subclavian and the the R and L common carotid arteries.
Apart from this, the right and left subclavian arteries give rise to the same four branches: the vertebral artery, the costocervical trunk, the superfical cervial artery, and the internal thoracic artery (which runs caudally).