Lung Anatomy and Physiology

Lung Anatomy and Physiology

• The left lung has two lobes, and the right lung has three lobes.
• The visceral pleura is the inner layer that surrounds the lung.
• The trachea splits into left and right primary bronchi at the carina.
• Gas exchange in the lungs occurs in the alveolar sacs.
• The pulmonary artery delivers unoxygenated blood to the lungs.
• The right and left bronchi, pulmonary artery and vein enter the lungs at the hilum.
• During inspiration, the diaphragm contracts downward to create a negative pressure in the chest.
• During gas exchange, carbon dioxide is transported across the capillary membrane to be exhaled while oxygen is transported across the capillary membrane to attach to red blood cells.
• The lower respiratory system consists of the trachea, carina, bronchioles, and alveoli.
• Inhaled oxygen travels down the trachea, into the right and left bronchus, then into the segmental bronchi, which branch into lobar bronchi, and finally into the alveoli.
• The parietal pleura covers the inner aspect of the thoracic cavity.
• The visceral pleura tightly adheres to the outer surface of the lungs and deep in the fissures.
• The parietal pleura is sensitive to pressure, pain, and temperature, and is innervated by the phrenic and intercostal nerves.
• The visceral pleura is not sensitive to pain, temperature, or touch, and is innervated by the autonomic nervous system.
• The pleural cavity is a potential space between the parietal and visceral pleura, containing a small volume of serous fluid.
• Pleural fluid functions to lubricate the surfaces of the pleurae for smooth movement and to create surface tension to help maintain the lungs’ expansion.
• The inferior border of the right lung extends to the 6th rib at the midclavicular line, the 8th rib at the mid-axillary line, and the 10th rib at the scapular line.
• The inferior border of the right pleura extends to the 6th rib at the midclavicular line, the 8th rib at the mid-axillary line, and the 10th rib at the scapular line.
• The inferior border of the left lung extends to the 6th rib at the midclavicular line, the 8th rib at the mid-axillary line, and the 10th rib at the scapular line.
• The inferior border of the left pleura extends to the 6th rib at the midclavicular line, the 8th rib at the mid-axillary line, and the 10th rib at the scapular line.
• The thoracic cavity is classified into a medial area (mediastinum) containing the heart and other structures, and lateral spaces containing the lungs and pleura.
• The lungs are the organs of respiration, bringing inspired air into close contact with oxygen-poor blood in the pulmonary capillaries to oxygenate blood.
• The lungs lie either side of the mediastinum within the thoracic cavity.
• Each lung is surrounded by a pleural cavity, formed by the visceral and parietal pleura.
• The lungs are suspended from the mediastinum by the lung root, a collection of structures entering and leaving the lungs.
• The medial surfaces of both lungs lie in close proximity to several mediastinal structures.
• The right lung has three lobes: superior, middle, and inferior.
• The left lung has two lobes: superior and inferior.

Pleurisy

• Pleurisy causes a pleural friction rub, which sounds like creaking leather or squeaking shoes on wet surfaces.
• The pleural friction rub is a valuable diagnostic clue for pleural inflammation.

Bronchial Asthma

• Normal airways are clear and open, with average wall thickness and normal muscle contraction
• An asthma attack can cause bronchospasm, inflammation, and mucus production.
• Bronchospasm causes the muscles around the airways to constrict, narrowing the airways.
• Inflammation causes the lining epithelium of the airways to become swollen, making inspiration and expiration difficult.
• Mucus production during an asthma attack can further close the airways.
• Asthma can cause wheezing due to narrowed airways.