Lungs

Overview of the Lungs

  • The lungs are located in the thoracic cavity and occupy most of this space except for the mediastinum, which is the central compartment.

Heart and Lung Positioning

  • The mediastinum houses the heart, and the left lung accommodates a space known as the cardiac notch.

  • The primary bronchi divide into right and left at the trachea:

    • Right primary bronchi descends at a less acute angle compared to the left.

    • This difference in angle is due to the heart's positioning towards the left side.

  • Clinical Implication: Inhaled foreign objects are more likely to lodge in the right lung because the angle is more direct for passage.

Lobes of the Lungs

  • Right Lung has three lobes:

    • Superior Lobe

    • Middle Lobe

    • Inferior Lobe

  • Left Lung has two lobes:

    • Superior Lobe

    • Inferior Lobe

Divisions of Lobes

  • Right Lung Lobes:

    • Horizontal Fissure divides the superior and middle lobes.

    • Oblique Fissure divides the middle and inferior lobes.

  • Left Lung:

    • Oblique Fissure divides the superior and inferior lobes.

Lung Anatomy Visualization

  • The apex is the top part of the lung, and the base is the lower part.

  • The inferior lobe primarily occupies the posterior surface of each lung, while superior and middle lobes dominate the anterior surface.

Stethoscope Placement in Clinical Examination

  • Doctors typically use a stethoscope on the posterior (back) side of the lungs:

    • This is because the inferior lobes, crucial for breathing at rest, occupy the posterior aspect, making it more effective for listening to breath sounds.

Bronchopulmonary Segments

  • Each lobe further divides into bronchopulmonary segments:

    • There are about 10 segments in the right lung and 8-10 in the left lung.

    • These segments are separated by tissue septa, allowing isolation of infections (one can be removed without affecting others).

Lung Composition and Blood Supply

  • The lung structure consists predominantly of alveoli, connective tissues, and elastic tissue.

  • Blood Supply:

    • Pulmonary Circulation:

      • Pulmonary Arteries transport deoxygenated blood to the lungs for gas exchange.

      • Pulmonary Veins carry oxygenated blood back to the heart.

    • Bronchial Circulation:

      • Supplies the lung tissue itself from the bronchial arteries (arising from the aorta).

      • Accompanied by bronchial veins, which handle deoxygenated blood.