Characteristics of Bronchopulmonary Segment

Pleura and Pleural Cavity

• Visceral pleura completely covers the lung and extends into interlobar fissures.
• Pleural cavity is a potential space between visceral and parietal pleura.
• Pleural fluid is a capillary layer of serous fluid that lubricates the pleural surfaces and allows the layers of pleura to slide smoothly over each other during respiration.

Parietal Pleura

• Covers internal surface of thoracic wall, with three main divisions:
  • Costal pleura: covers internal surface of thoracic wall.
  • Mediastinal pleura: covers lateral aspects of mediastinum.
  • Diaphragmatic pleura: covers thoracic surface of diaphragm on each side of the mediastinum.
• Cervical pleura (pleural cupula) extends through the superior thoracic aperture into the root of the neck, forming a cup-shaped dome over the apex of the lung.

Innervation of Parietal Pleura

• Parietal pleura sensitive to pain, temperature, touch, and pressure.
• Costal pleura innervated by intercostal nerves.
• Mediastinal pleura innervated by phrenic nerve.
• Diaphragmatic pleura innervated by phrenic nerve (domes) and lower 6 intercostal nerves (periphery).

Visceral Pleura

• Sensitive to stretch.
• Innervated by pulmonary plexus.

Lines of Pleural Reflection

• Sternal line of pleural reflection.
• Costal line of pleural reflection.
• Vertebral line of pleural reflection.

Recesses

• Costodiaphramatic recess: lowermost part of costal pleura and peripheral diaphragmatic pleura.
• Costomediastinal recess: smaller recesses posterior to the sternum where the costal pleura is in contact with the mediastinal pleura.

Bronchopulmonary Segment

• A subdivision of a lung lobe.
• Pyramidal in shape, apex toward the root of the lung, base at pleural surface.
• Surrounded by connective tissue.
• Has segmental bronchus, segmental artery, lymph vessels, and autonomic nerves.
• Segmental vein lies in the connective tissue between adjacent bronchopulmonary segments.
• A diseased segment can be removed surgically.

Bronchopulmonary Segments of Right and Left Lungs

• Right lung: 10 segments (superior, middle, and inferior lobes).
• Left lung: 10 segments (superior and inferior lobes).

Auscultation Sites

• Apex: medial 1/3 of the clavicle anteriorly and upper part of the supraclavicular region posteriorly.
• Superior lobe of right lung: clavicle to 4th costal cartilage.
• Superior lobe of left lung: clavicle to 6th costal cartilage.
• Middle lobe: 4th-6th ribs in front of the midaxillary line.
• Apical or superior segment of lower lobe: posteriorly in the interval between medial border of scapula and the vertebral spines.
• Basal segment of the lower lobe: posteriorly in the infrascapular region up to 10th rib.

Pulmonary Ligament

• At the root of the lung, the visceral and parietal pleural layers are continuous.
• A double layer of parietal pleura hangs inferiorly from this region.

Lungs

• Each lung lies free in its own pleural cavity, attached to the mediastinum only by the root of the lung and pulmonary ligament.
• Grayish black in adults, pink in children.
• Weight: left lung (550g), right lung (600g).
• The right lung is broader and shorter than the left due to the liver pushing the dome of the diaphragm upwards.
• Lobar divisions: right lung (3 lobes), left lung (2 lobes).
• Fissures: right lung (oblique and horizontal), left lung (oblique).
• Oblique fissure: lateral to T3, 5th rib in the midaxillary line, and 7-8 cm lateral to 6th costal cartilage.
• Horizontal fissure: right 4th intercostal cartilage and rib meet the oblique fissure in the midaxillary line.

Characteristics of Lungs

• Rounded apex.
• Costal, diaphragmatic, and mediastinal surfaces.
• Anterior, inferior, and posterior borders.
• Apex: blunt superior end of the lung ascending above the level of the 1st rib into the neck, covered by cervical pleura.

Surfaces of the Lung

• Costal surface: adjacent to the sternum, costal cartilages, and ribs.
• Diaphragmatic surface: resting on the dome of the diaphragm.
• Mediastinal surface: bears the hilum.