Thoracic Wall, Breast, and Lungs

In which direction do the fibers of each of the layers extend?

Fibers of the External Intercostal muscles extend caudally and medially, while the fibers of the Internal Intercostal muscles extend cranially and laterally.

What is a pneumothorax? What is a hemothorax?

A pneumothorax is the entry of air into the pleural cavity while a hemothorax is the entry of blood into the pleural cavity.

What structure(s) innervate the intercostal muscles?

All of the intercostal muscles are innervated by the Intercostal nerves

Which component of the neurovascular bundle is least protected? What is the clinical implication?

As intercostal nerves are at the bottom of the group, they are the least protected by the costal groove. As such, they are the most likely to receive trauma of the three structures.

If breast mobility is reduced, what does this indicate?

As retromammary space provides breast mobility, reduction in this mobility could suggest abnormalities such as tumor growth.

What is a bronchopulmonary segment (BPS)? How many BPS's are found in each lung? What is the clinical implication of BPSs?

Bronchopulmonary segments are the largest subdivision of the lung lobes, independently supplied by tertiary bronchus and thus surgically respectable. There are typically about ten segments in the right lung and eight to ten segment in the left lung.

In which breast quadrant do tumors most frequently occur?

Due to additional breast tissue, tumors occur most frequently in the superolateral quadrant of the breast.

What is the role of suspensory ligaments in advanced tumorigenesis of the breast?

In advanced tumorigenesis of breast, since the suspensory ligaments remain tight in spite of breast tumor growth, the breast appear to be dimpled with presence of cancer.

Discuss lymphatic drainage of the breast.

Lymphatic drainage of the breast follows three paths. Lateral breast lymph drains into the pectoral lymph nodes and then into axillary lymph nodes. Medial breast lymph drains into the parasternal lymph nodes. Inferior breast lymph drains deeply into abdominal lymph nodes.

What is a pleural recess? Name two pleural recesses. Cite a clinical implication of these recesses.

Pleural recesses are areas of the pulmonary cavities that the lungs do not fully occupy during respiration and pleura are in contact; as such, these recesses are often where fluids or air accumulate in the pulmonary cavities. ▪ Costodiaphragmatic Recesses - Present at base of lungs above the diaphragm where lungs do not fully extend down. Site of potential fluid collection. ▪ Costomediastinal Recess - Space present due to cardiac notch of the left lung.

From what vessel do the posterior intercostal arteries arise? From which vessel do their anterior counterparts arise?

Posterior intercostal arteries arise from the thoracic aorta while anterior intercostal arteries arise from the internal thoracic arteries.

What is the relationship between bronchi and pulmonary arteries? What is the relationship between bronchi and pulmonary veins?

Pulmonary arteries travel from heart to bronchi carrying low-oxygen blood that becomes oxygenated. Pulmonary veins then carry this oxygen-rich blood from bronchi back to heart to be sent to rest of body.

What is the axillary tail of the mammary gland?

The Axillary Tail of the mammary gland is an extension of breast tissue up into the axilla, from the superolateral quadrant.

Discuss vascular supply of the breast.

The blood supply to the breast is provided medially by the Medial Mammary arteries, which derive from the Internal Thoracic artery, and laterally by the Lateral Mammary arteries, which derive from the Lateral Thoracic artery.

What vessels supply lung tissue with oxygenated blood?

The bronchial arteries supply oxygenated blood to the lung tissue and visceral pleura, as opposed to the other arteries that supply low-oxygen blood.

In what order is each intercostal neurovascular bundle arranged? What is the relationship with the structure of the rib?

The contents of the intercostal neurovascular bundle travel with intercostal vein most superiorly, intercostal artery, and intercostal nerve most inferiorly. This bundle travels beneath the costal groove of rib.

What are the 3 muscle groups that form the deepest layer of the thoracic wall muscles?

The deepest layer of the thoracic wall musculature is formed by the Innermost Intercostal muscles, Subcostal muscles, and Transversus Thoracic muscles.

What is the fascial layer found between the intercostal muscles and the pleura?

The endothoracic fascia separates the intercostal muscles and inner thoracic cavity from the pleural cavity within.

Explain the role of negative pressure during inspiration.

The expansion of the thoracic cavity due to diaphragm and accessory muscles causes a negative pressure to building in thoracic cavity. This negative pressure draws air down into lungs, thus serving as the cause of inspiration.

Where does the intercostal neurovascular bundle run?

The intercostal neurovascular bundle runs between the Internal and Innermost Intercostal muscle layers, along the costal grooves of overlying ribs.

What causes the visceral pleura to adhere to the parietal pleura?

The lubricating layer of serous pleural fluid between the visceral and parietal pleura allows the two layers to adhere to one another, ensuring proper lung expansion.

Be able to label a diagram of the anatomical surface features of the lungs

The lung has an anterior, posterior, and inferior border. The right lung has a superior, middle, and inferior lobe, along with an oblique and horizontal fissure. The left lung just has a superior and inferior lobe separated by an oblique fissure. The root of the lung contains pulmonary arteries, pulmonary veins, and primary bronchus all surrounded by the hilum, and above the pulmonary ligament.

What does a main (primary) bronchus supply? What does a secondary bronchus supply? What does a tertiary bronchus supply?

The main bronchus supplies each lung. The secondary bronchus derives from the main bronchus and supplies the lobes of the lung. The tertiary bronchus branches off the secondary bronchus and supplies a bronchopulmonary segment.

What are the various divisions of the parietal pleura? How does the innervation of parietal pleura differ from visceral? Where is parietal pleura continuous with visceral pleura?

The parietal pleura is divided into four regional components: the costal, diaphragmatic, mediastinal, and cervical pleura. The parietal and visceral pleura are only continuous around the hilum of each lung. The parietal pleura is innervated by the intercostal and phrenic nerves with high sensitivity to pain and temperature, while the visceral pleura is innervated by the pulmonary plexus with limited sensitivity.

Name the muscles of the thoracic wall that anchor to the thoracic cage to act as accessory muscles of respiration.

The pectoralis major, pectoralis minor, and serratus anterior muscles act as accessory muscles in respiration as they elevate ribs to expand thoracic cavity during inspiration.

What is the pulmonary ligament?

The pulmonary ligament is not a true ligament, but rather a continuity between the parietal and visceral pleura at the root of the lung, that secures the lung and provides a potential space for lung expansion.

Between which two fascial planes is the retromammary space located? What is the significance of this space? What is this space used for in cosmetic surgery?

The retromammary space is located between the pectoral fascia and the superficial fascia, that allows for the breast to move somewhat freely. This is also the space where breast implantation occurs.

Which main bronchus is explored first when objects are aspirated? Why?

The right main bronchus is the primary site where aspirated foreign objects become lodged, as the right main bronchus is wider, shorter, and runs more vertically than the left main bronchus.

Discuss innervation of the breast.

The sensory innervation of the breast is provided by anterior and lateral cutaneous branches of the Intercostal nerves, along with minor contribution from Supraclavicular nerves.

What is the function of the serratus posterior superior and inferior?

The serratus posterior superior helps elevate the ribs, while the serratus posterior inferior helps depress the ribs.

From here the lymph passes to what other groups located long the bronchus and trachea?

The superficial and deep lymphatics of the lung drain into the bronchopulmonary lymph nodes, then into the tracheobronchial lymph nodes, then into the bronchomediastinal lymph nodes, and finally into the right lymphatic duct or thoracic duct.

To what nodes do the superficial and deep lymphatics of the lung drain? Where are these nodes located?

The superficial subpleural lymphatic plexus drains the lung and visceral pleura. The deep bronchopulmonary lymphatic plexus drains the root of the lung.

What is the suprapleural membrane? What serous membrane lines each compartment of the thoracic cavity?

The suprapleural membrane is an extension of the endothoracic fascia that completes the thoracic cavity at superior thoracic aperture. The serous membrane surrounding each compartment of the thoracic cavity is the parietal pleura.

What is the function of the suspensory ligaments?

The suspensory ligaments function to attach and support the breast to the dermis and surrounding fascia.

What are the boundaries of the thoracic inlet and the thoracic outlet?

The thoracic outlet, or superior thoracic aperture, is bounded by the T1 vertebrae, 1st ribs and costal cartilages, and superior manubrium The thoracic inlet, or inferior thoracic aperture, is bounded by the T12 vertebrae, 11th and 12th ribs and costal cartilages, and xiphisternal joint.

List the muscles that are found within the intercostal space - from superficial to deep.

There are five types of muscles that span the intercostal space: External Intercostal muscles, Internal Intercostal muscles, Innermost Intercostal muscles, along with Subcostal muscles and Transversus Thoracic muscles.