Thoracic Cavity

Question 1

Mediastinum

Answer 1

Area between the sternum, the 2 pleural cavities, and the vertebral column. Thick but is a movable partition.

plane of Louis (sternal angle - bottom of T4) separates superior mediastinum & inferior mediastinum.

Structures in superior mediastinum:
Arteries:
-right & left subclavian
-right and left common carotid
-brachiocephalic
-aortic arch
Veins:
-brachiocephalic 
-supreme intercostals
-azygos (posterior)
-left superior intercostal 
Nerves:
-vagus nerves
-phrenic nerves
Others:
-oesophagus
-trachea

-Inferior mediastinum:
Anterior mediastinum:
-tissue
-thymus in children ONLY
Middle mediastinum:
-heart 
-tracheal bifurcation 
-phrenic nerves
Posterior mediastinum:
-Arteries: posterior intercostals, thoracic aorta
-Veins: hemiazygos, azygos, accessory hemiazygos.
-Nerves: sympathetic trunks
-other : oesophegus

Question 2

Pleurae

Answer 2

2 layers: meet at root of lung & form pulmonary ligament.

• parietal layer: outer layer, lines the thoracic wall.
• visceral layer: inner layer, covers the lobes of the lung and extends into the fissures.

Pleural cavity between the 2 layers.

Parts of parietal pleura:

• cervical: extends to neck
• costal: ribs and costal cartilages
• mediastinal: mediastinum
• diaphragmatic: diaphragm

Pleural recesses:

• parts of the pleural cavity NOT filled with the lung.
• allow expansion of the lung during forced inspiration
• types: costomediastinal & costodiaphragmatic.

Nerve supply:
-parietal pleura:
intercostal nerves (costal & peripheral diaphragmatic pleura)
Phrenic nerves (mediastinal and central diaphragmatic pleura)

Visceral pleura:
-visceral afferent nerves & autonomic nerves (from pulmonary plexus)

Question 3

lungs

Answer 3

conical in shape.
1) Apex at the upper end 2) Base resting on the diaphragm . 3) Three borders: anterior, posterior . 4) Two surfaces: costal and medial (vertebral and mediastinal).
separated from eachother by mediastinum.

Differences between right and left lungs
Right:
-has 2 fissures and 3 lobes
-anterior border is straight
-larger and heavier
-shorter and broader
Left:
- 1 fissure and 2 lobes
-anterior border is interrupted by cardiac notch
- smaller and lighter
-longer and narrower

Roots of the lung:
formed by structures that enter/ come out of the lung hilum.
1. principal bronchus on left side, and eparterial and hyparterial bronchi on right side
2. Two pulmonary veins, superior and inferior.
3. One pulmonary artery
4. Bronchial arteries, one on right side and two on the left side.
5. Bronchial veins
6. Bronchopulmonary lymph nodes,
7. Ant and post pulmonary plexus of nerves
8. lymphatics of the lungs
9. Areolar tissue

Bronchial tree
•Primary bronchi:
enter the hilum of each lung with pulmonary vessels, lymphatic vessels and nerves
•secondary(lobar) bronchi
branch of primary bronchus.
-left lung: 2 secondary bronchi
-right lung: 3 secondary bronchi
•tertiary(segmental) bronchi
branch of secondary bronchi
-left lung: supplied by 8 tertiary bronchi
-right lung: supplied by 10 tertiary bronchi

blood supply: 2 distinct blood supplies
•pulmonary arteries: carry deoxygenated blood from the pulmonary trunk (anterior to the bronchi)
•Bronchial arteries: supply pulmonary tissues and the bronchial tree with oxygenated blood .

lymphatic drainage:
•Lymph from the superficial lymphatic plexus flows into the bronchopulmonary nodes
•Lymph from the deep plexus flows to the pulmonary nodes and the bronchopulmonary nodes.
•The bronchopulmonary nodes drain into the tracheobronchial nodes, the paratracheal nodes, and finally, the bronchomediastinal trunks

nerve supply: come from the pulmonary plexuses.
•parasympathetic nerves from the vagus nerve
•sympathetic nerves are from the cervical & upper thoracic ganglia.

Question 4

pericardium

Answer 4

2 layers:
•fibrous pericardium
•serous pericardium:
-visceral (inside layer surrounding the heart)
-parietal (outside layer before the fibrous pericardium)
2 layers of the serous pericardium are divided by the pericardial cavity.

vessels:
•pericardiophrenic artery
•pericardiophrenic vein
•phrenic nerve (pain is felt in shoulder)

structures: transverse & oblique pericardial sinus.