Parts of lower respiratory tract
When a human being inhales, air travels down the trachea, through the bronchial tubes, and into the lungs. The entire tract is protected by the rib cage, spinal cord and sternum bone.
The term lower respiratory tract refers to the portions of the respiratory system from the trachea to the lungs. The lower respiratory tract consists of:
- The trachea (wind pipe)
- The two bronchial tubes (one to each lung)
- The bronchioles and the lungs.
The larynx is not just our voice box; it also serves as protection for our trachea. The larynx has a flap called the epiglottis which prevents food and water from entering our lungs when we breathe. If the epiglottis does not close when swallowing food or water, there is an involuntary reaction to cough. The larynx also has cilia. The trachea consists of cartilage and is the largest tube in the respiratory system. At the bottom of the tube, it branches off into two individual tubes, called the bronchial tubes, or bronchi. The bronchial tubes then branch off into smaller sections inside the lungs, called bronchioles. These bronchioles hold the air sacs in the lungs called the alveoli. The lungs are the biggest organ in the lower respiratory tract. The diaphragm is the main muscle involved for the lungs to breathe and is the largest muscle. There are smaller muscles in between our rib cage that help the lungs expand and contract.
When a human being inhales, air travels down the trachea, through the bronchial tubes and into the lungs. The entire tract is protected by the rib cage, spinal cord and sternum bone. In the lungs, oxygen from the inhaled air is transferred into the blood and circulated throughout the body. Carbon dioxide (CO2) is transferred from returning blood back into gaseous form in the lungs and exhaled through the lower respiratory tract and then the upper, to complete the process of breathing.