The lungs are the main component of your respiratory system. The respiratory system works closely with the cardiovascular system to provide your body with vital oxygen. The lungs themselves have many components that work to help attach oxygen to your blood and to release carbon dioxide.
Pleural Cavity and Membrane
The pleural cavity is the name for the space within your chest that houses your lungs. This cavity is lined with two thin pleural membranes. One of the membranes makes a smooth fluid, while the other membrane wraps around each lung. The fluid in between these membranes allows for smooth movement of the lungs as they inflate and deflate during respiration.
Lobes
The lung tissue itself is very soft, spongy and expandable. You have two lungs, one on the left and one on the right that is slightly larger. The lungs are subdivided into lobes, or main areas where the airway (bonchi) branches off. The right lung is composed of three lobes (upper, middle and lower), and the left lung only has two lobes (upper and lower) to make room for the heart.
Airway
Air enters through your nose or mouth and travels down your throat (made up of the oropharynx, epiglottis and larynx) into your trachea. The trachea divides into two tubes, called bronchi, or the primary bronchus on each side. This division happens just above the evel of the heart. The primary bronchus branches into smaller and smaller sections, starting with secondary and tertiary bronchus, to bronchioles and finally to terminal bronchioles that end in tiny round alveoli. According to "The Human Body Book," there are around 30,000 terminal bronchioles in each lung that end in more than 300 million alveoli. The alveoli are air sacs that work with the blood supply to exchange carbon dioxide for oxygen. They are grouped off the bronchioles similarly to groups of grapes off a vine. Within the linings of the lungs are millions of cells called cilia. These cilia beat and move in a wave-like motion to move dirt, debris and germs up into the trachea to be coughed up.
Blood Supply
Within the lungs are blood vessels that take blood directly from the pulmonary artery that branches off the heart. Just like the airway, the artery branches into smaller and smaller segments. The artery turns into arterioles that branch into a capillary network that surrounds the airway sacs (alveoli) by forming a circular grid of vessels around the outside of each individual alveolus. The exchange of oxygen and carbon dioxide happens through the process of simple diffusion (moving from an area of greater concentration to an area of lesser concentration) between the air sac and the blood vessel. Once the carbon dioxide is released and the oxygen attaches to the blood, the blood vessels turn into venules that become larger and turn into the pulmonary vein, which empties directly into the heart, where the oxygenated blood is pumped through the body. This process happens over and over with each breath and heartbeat.
References
- "The Human Body Book;" Steve Parker; 2007
- "Emergency Care and Transport of the Sick and Injured, Ninth Edition;" American Academy of Orthopaedic Surgeons; 2005
