Lungs and Chest Wall Anatomy and Physiology

Comprehensive practice flashcards covering lungs and chest wall anatomy, thoracic cage boundaries, respiratory muscles, pleural cavities, pulmonary/bronchial circulation, nervous system innervation, and airway reflexes.

What are the four primary purposes of using the series of imaginary lines drawn on the chest wall?

They are used to find reference points, identify landmarks on the thorax, identify the location of underlying structures, and describe the location of abnormal physical exam findings.

Which imaginary lines are located on the anterior chest and how are they defined?

The Midsternal Line (divides the thorax into equal halves) and the Left and Right Midclavicular Lines (drawn through the midpoints of the left and right clavicles).

Which three imaginary lines divide the lateral chest wall?

The Midaxillary Line (divides the lateral chest into equal halves), Anterior Axillary Line (situated along the anterolateral chest), and Posterior Axillary Line (situated on the posterolateral chest).

Which imaginary lines divide the posterior chest wall?

The Midspinal Line (divides the posterior chest into equal halves) and the Scapular Lines (parallel to the midspinal line, passing through the scapula on each side).

What three anatomical cavities make up the thorax?

The Left pleural cavity, Right pleural cavity, and Mediastinum.

How are ribs 1 through 7 classified, and how do they attach to the sternum?

They are classified as vertebrosternal (true) ribs and connect directly to the sternum via costal cartilages.

How are ribs 8 through 10 classified, and how do they attach to the sternum?

They are classified as vertebrochondral (false) ribs and connect to the lower sternum via a common cartilage.

How are ribs 11 and 12 classified, and why?

They are classified as floating ribs because they do not connect to the sternum.

What neurovascular structures are located within the costal groove, and what clinical precaution must be taken?

The costal groove on the underside of each rib contains an intercostal artery, vein, and nerve. Needles or chest tubes must always be inserted above the rib to avoid damaging these structures.

What three structures form the sternum?

The Manubrium, Body, and Xiphoid Process.

What is the Angle of Louis, and what key landmark does it represent?

It is the junction of the manubrium and the body of the sternum at the level of the 2nd rib, marking the level of the tracheal carina.

Based on the illustrated mechanical movements of the ribs, how do 'bucket handle' and 'pump handle' movements alter thoracic dimensions during breathing?

Bucket handle movement (A) elevates the lateral shaft of the rib to increase transverse diameter. Pump handle movement (B) elevates the sternum superiorly and anteriorly to increase anterior-posterior diameter.

What are the primary muscles of inspiration during normal quiet breathing?

The Diaphragm, Intercostal muscles, and Scalenes.

What are the primary muscles of normal quiet expiration?

None; normal quiet expiration is a passive process.

Which nerve innervates the diaphragm, and what structural changes occur when the diaphragm contracts?

The phrenic nerve innervates the diaphragm; during inspiration, it contracts and flattens, increasing the vertical diameter of the thorax.

Which muscles act as accessory muscles of inspiration and expiration?

Accessory muscles of inspiration include the Sternomastoids and Pectoralis Major. The primary accessory muscle of expiration is the Rectus abdominis.

What anatomical structures are contained within the mediastinum?

The heart, aorta, esophagus, great veins, trachea, and mainstem bronchi.

What is the hilum of the lung?

The medial entry point of the lungs where the mainstem bronchus, blood vessels, and nerves enter and exit.

How do the anatomical features of the right lung differ from the left lung?

The right lung has 2 fissures, 3 lobes, and is shorter, wider, and heavier. The left lung has 1 fissure, 2 lobes, contains the lingula and cardiac notch, and is longer, narrower, smaller, and lighter.

What are the two layers of the pleural membrane and what do they attach to?

The visceral pleura attaches directly to the surface of the lung, while the parietal pleura attaches to the inner chest wall surface.

What is a pleural effusion, and how does it alter the costophrenic angles on a chest X-ray?

A pleural effusion is fluid accumulation in the pleural space, which settles into the costophrenic angles and blunts their normally sharp appearance on a chest X-ray.

What is the primary function of the pulmonary circulation system?

To bring deoxygenated blood into contact with alveolar gas to perform external respiration (gas exchange).

What is the origin and function of the bronchial circulation?

It arises from the aorta as the bronchial arteries and supplies oxygenated blood to all airway walls.

How does bronchial circulation contribute to a normal anatomical shunt?

A portion of deoxygenated blood leaving airway capillaries drains directly into the pulmonary veins leading to the left atrium, mixing deoxygenated blood with freshly oxygenated blood.

How much fluid is filtered into the pulmonary interstitial space daily, and how is excess fluid handled?

Approximately $30\,dm^3$ ($30\,\text{L}$) is filtered out of blood into the interstitial space and $27\,dm^3$ ($27\,\text{L}$) is reabsorbed; the remaining $3\,dm^3$ ($3\,\text{L}$) of excess fluid is absorbed and filtered by the lymphatic system.

From which spinal spinal nerve roots do the phrenic nerves originate?

They originate from spinal segments $C_3$ to $C_5$ ('C3 through 5, Keep the Diaphragm Alive').

What airway response is mediated by Beta-2 ($\beta_2$) adrenergic receptor stimulation?

Bronchodilation of airway smooth muscle.

What physiological responses are triggered by Acetylcholine (ACh) stimulation of Muscarinic ($M_3$) receptors?

Bronchoconstriction/bronchospasm and increased mucus production from submucosal glands.

What role do Slowly Adapting Stretch Receptors (SARs) play in breathing control?

When stretched during deep inspiration, SARs send inhibitory nerve impulses via the vagus nerve to the brain's respiratory centers to terminate inspiration (Hering-Breuer reflex).

What protective responses are triggered when Rapidly Adapting Receptors (RARs) are stimulated by irritants?

Reflex bronchoconstriction, expiratory narrowing of the larynx, cough, deep inspiration, and mucous secretion.

What are the five sequential steps of an effective cough?

1. Deep inspiration caused by diaphragm contraction; 2. Slight inspiratory pause; 3. Glottis closure by laryngeal muscles; 4. Forceful contraction of abdominal expiratory muscles building high intrapulmonary pressure; 5. Sudden opening of the glottis releasing compressed gas.

Where are J-receptors located, and what clinical conditions stimulate them?

They are C-fiber endings located deep in the lung parenchyma near pulmonary capillaries and alveoli; they are stimulated by alveolar inflammatory processes (e.g., pneumonia) and increased pulmonary capillary pressure/edema (e.g., congestive heart failure).