The respiratory system plays a vital role in the body by providing oxygen, as well as excreting carbon dioxide. The three major parts of the respiratory system are the airways, the lungs, and the muscles of respiration.
The airways (nose, mouth, pharynx, larynx etc.) allow air to enter the body and into the lungs. The lungs work to pass oxygen into the body, whilst removing carbon dioxide from the body.
The muscles of respiration, such as the diaphragm, work in unison to pump air into and out of the lungs whilst breathing.
Organs of Respiratory System
Nose and Nasal Cavity
- The nose is the primary opening for the respiratory system, made of bone, muscle, and cartilage.
- The nasal cavity is a cavity within nose filled with mucus membranes and hairs.
- Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity.
- Maxillary sinuses are located under the eyes
- Frontal sinuses are above the eyes.
- Ethmoidal sinuses are between the eyes.
- Sphenoidal sinuses are behind the eyes.
- Function : The nose is used to inhale air into the body. The nasal cavity warms the air as it enters, acting as filtration and purifying the air by removing any dust, pollen, and other contaminants, before it passed to the inner body.
Mouth
- Also called the oral cavity, the mouth is the secondary exterior opening for the respiratory system.
- Function : Inhaling air through the mouth allows more inhalation, as the oral cavity is far larger than the nasal cavity. The oral cavity has no hairs or filtering techniques, meaning the air you inhale does not undergo the filtration process.
Pharynx
- Also called the throat, the pharynx is a funnel of muscle that extends from the respiratory openings to the esophagus and larynx.
- Function : Air that is inhaled enters the pharynx, where it descends into the larynx via a diversion from the epiglottis. The epiglottis ensures that air can pass into the trachea, and that food enters the esophagus.
Larynx
- Also known as the voice box, the larynx is situated below the pharynx, in the anterior portion of the neck.
- Function : Aside from allowing us the ability of speech, the larynx also acts as a defense mechanism. If any food passes into the esophagus when swallowing, the larynx produces a strong cough reflex.
Trachea
- Also known as the wind pipe, the trachea is a tube made of cartilage rings that are lined with pseudostratified ciliated columnar epithelium.
- Function : The main respiratory function of the trachea is to provide a clear and unhindered airway for air to enter and exit the lungs. Inside the trachea, small hairs reside upon the inner walls. These hairs catch dust and other contaminants from inhaled air, which are later expelled via coughing.
Bronchi
- The bronchi are two tubes stemming off of the end of the trachea. Each tube is connected to a lung.
- Function : The bronchi connect the wind pipe to the lungs, allowing air from external respiratory openings to pass efficiently into the lungs. Once in the lungs, the bronchi begin to branch out into secondary, smaller bronchi, coined tertiary bronchi.
Bronchioles
- Tertiary bronchi divide to even smaller, narrower tubes known as bronchioles.
- Function : Bronchioles lead to alveolar sacs, which are sacs containing alveoli.
Alveoli
- Alveoli are hollow, individual cavities that are found within alveolar sacs.
- Function : Alveoli have extremely thin walls, which allows the exchange of oxygen and carbon dioxide to take place within the lungs. There are estimated to be three million alveoli in the average lung.
Diaphragm
- The diaphragm is an important muscle of respiration which is situated beneath the lungs.
- Function : The diaphragm contracts to expand the space inside the thoracic cavity, whilst moving a few inches inferiorly into the abdominal cavity. Whilst this is happening, the intercostal muscles also contract, which moves the rip cage up and out. The contractions force air into the lungs, by creating a negative pressure through expansion.
Lungs
- The lungs are a pair of large, spongy organs found in the thorax lateral to the heart and superior to the diaphragm.
- Each lung is surrounded by a pleural membrane that provides the lung with space to expand as well as a negative pressure space relative to the body’s exterior.
- The negative pressure allows the lungs to passively fill with air as they relax. The left and right lungs are slightly different in size and shape due to the heart pointing to the left side of the body. The left lung is therefore slightly smaller than the right lung and is made up of 2 lobes while the right lung has 3 lobes.
- Function : Oxygen enters lungs as part of the air that breathe. It goes to the blood vessels deep in our lungs and then on to all parts of our body. As body uses oxygen, it makes a waste product called carbon dioxide.
Physiology of Respiration
Inhalation is usually an active movement. The contraction of the diaphragm muscles cause a pressure variation, which is equal to the pressures caused by elastic, resistive and inertial components of the respiratory system. In contrast, expiration is usually a passive process.
Tidal volume. During inspiration, the diaphragm and external intercostal muscles contract, increasing the volume of the thoracic cavity. This causes the intrapleural pressure to become more negative, which increases the transpulmonary pressure, causing the lungs to expand.
The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside. This action is also known as external respiration. When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity.
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