The lungs are the major organs of the respiratory system and are responsible for performing gas exchange. The lungs are paired and separated into lobes; The left lung consists of two lobes, whereas the right lung consists of three lobes. Blood circulation is very important, as blood is required to transport oxygen from the lungs to other tissues throughout the body. The function of the pulmonary circulation is to aid in gas exchange. The pulmonary artery provides deoxygenated blood to the capillaries that form respiratory membranes with the alveoli, and the pulmonary veins return newly oxygenated blood to the heart for further transport throughout the body. The lungs are innervated by the parasympathetic and sympathetic nervous systems, which coordinate the bronchodilation and bronchoconstriction of the airways. The lungs are enclosed by the pleura, a membrane that is composed of visceral and parietal pleural layers. The space between these two layers is called the pleural cavity. The mesothelial cells of the pleural membrane create pleural fluid, which serves as both a lubricant (to reduce friction during breathing) and as an adhesive to adhere the lungs to the thoracic wall (to facilitate movement of the lungs during ventilation).
bronchoconstriction
decrease in the size of the bronchiole due to contraction of the muscular wall
bronchodilation
increase in the size of the bronchiole due to contraction of the muscular wall
cardiac notch
indentation on the surface of the left lung that allows space for the heart
hilum
concave structure on the mediastinal surface of the lungs where blood vessels, lymphatic vessels, nerves, and a bronchus enter the lung
lung
organ of the respiratory system that performs gas exchange
parietal pleura
outermost layer of the pleura that connects to the thoracic wall, mediastinum, and diaphragm
pleural cavity
space between the visceral and parietal pleurae
pleural fluid
substance that acts as a lubricant for the visceral and parietal layers of the pleura during the movement of breathing
pulmonary artery
artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli
pulmonary plexus
network of autonomic nervous system fibers found near the hilum of the lung
visceral pleura
innermost layer of the pleura that is superficial to the lungs and extends into the lung fissures
1. Which of the following structures separates the lung into lobes?
A) mediastinum
B) fissure
C) root
D) pleura
B
2. A section of the lung that receives its own tertiary bronchus is called the ________.
A) bronchopulmonary segment
B) pulmonary lobule
C) interpulmonary segment
D) respiratory segment
A
3. The ________ circulation picks up oxygen for cellular use and drops off carbon dioxide for removal from the body.
A) pulmonary
B) interlobular
C) respiratory
D) bronchial
C
4. The pleura that surrounds the lungs consists of two layers, the ________.
A) visceral and parietal pleurae.
B) mediastinum and parietal pleurae.
C) visceral and mediastinum pleurae.
D) none of the above
A
1. Compare and contrast the right and left lungs.
The right and left lungs differ in size and shape to accommodate other organs that encroach on the thoracic region. The right lung consists of three lobes and is shorter than the left lung, due to the position of the liver underneath it. The left lung consist of two lobes and is longer and narrower than the right lung. The left lung has a concave region on the mediastinal surface called the cardiac notch that allows space for the heart.
2. Why are the pleurae not damaged during normal breathing?
There is a cavity, called the pleural cavity, between the parietal and visceral layers of the pleura. Mesothelial cells produce and secrete pleural fluid into the pleural cavity that acts as a lubricant. Therefore, as you breathe, the pleural fluid prevents the two layers of the pleura from rubbing against each other and causing damage due to friction.