pulmones

Pulmones are the paired organs of respiration in humans and many other vertebrates. In humans, the two lungs occupy most of the thoracic cavity, protected by the rib cage and encased by a double-layered serous membrane called the pleura. The lungs are divided into lobes: the right lung has three lobes—superior, middle, and inferior—separated by the horizontal and oblique fissures; the left lung has two lobes—superior and inferior—separated by the oblique fissure.

Air enters through the trachea, which branches into the right and left main bronchi and further into progressively smaller bronchioles. The distal airways terminate in alveolar sacs composed of alveoli, where gas exchange occurs across the alveolar–capillary membrane. The alveolar epithelium and capillary endothelium form a very thin barrier that allows diffusion of oxygen into the blood and removal of carbon dioxide from it. The pleurae and pleural fluid reduce friction during breathing.

Physiology and circulation: The lungs receive deoxygenated blood from the right ventricle via the pulmonary arteries; this pulmonary circulation is separate from the bronchial circulation that nourishes lung tissue. Oxygenated blood returns to the left atrium through the pulmonary veins. Ventilation is driven by respiratory muscles, mainly the diaphragm and intercostal muscles, under autonomic and higher-center control. Parasympathetic input tends to constrict airways, while sympathetic input promotes bronchodilation.

Development and clinical context: Lungs develop from foregut endoderm and surrounding mesenchyme; alveolar formation continues after birth. Pulmones may be affected by infectious diseases such as pneumonia, chronic obstructive pulmonary disease, asthma, pulmonary embolism, lung cancer, and pleural effusion, which can impair gas exchange. Imaging studies such as chest radiographs and computed tomography are commonly used to assess pulmones.