Intercostal veins

Anterior branches of the intercostal veins drain to the internal thoracic and musculophrenic veins.

Posterior branches drain to the azygos system of veins.

Table EI1-2-1. The Four Stages of Lung Development

Stage

Characteristics

Glandular (weeks 5-17)

Respiration is not possible j Premature fetuses cannot survive

Canalicular (weeks 13-25)

Respiration is not possible Premature fetuses rarely survive

Terminal sac (weeks 24-birth)

Type I and type II pneumocytes are present Respiration is possible

Premature fetuses born between weeks 25 and 28 can

survive with intensive care

Alveolar (birth-8 years)

Note: Lung development continues after birth

_

Respiratory bronchioles, terminal sacs, alveolar ducts, and alveoli increase in number

Chest radiograph is more dense in children

Clinical Correlate

Respiratory Distress Syndrome

Respiratory distress syndrome is caused by a deficiency of surfactant (composed of phosphatidylcholine [mainly dipalmitoyl lecithin] and proteins). This condition can be associated with premature infants, infants of diabetic mothers, and prolonged intrauterine asphyxia. Thyroxine and Cortisol treatment increase the production of surfactant.

Hyaline Membrane Disease Surfactant deficiency may lead to hyaline membrane disease whereby repeated gasping inhalations damage the alveolar lining. Hyaline membrane disease is characterized histologically by collapsed alveoli (atelectasis) and eosinophilic (pink) fluid covering the alveoli,

PLEURA AND PLEURAL CAVITY

Parietal pleura lines the inner surface of the thoracic cavity; visceral pleura follows the contours of the lung itself (Figure III-2-4).

Costo mediastinal recess

Costodiaphragmatic recess

Figure 111-2—4- Lungs and Pleura

Costodiaphragmatic recess

Figure 111-2—4- Lungs and Pleura

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