Respiratory System Organs And Functions – Conductive Portion And Respiratory Portion – Inspiration And Expiration

→ Summary

• The respiratory system is a system related to the uptake of oxygen and release of carbon dioxide to the environment.
• The respiratory system can be divided into two parts: a conducting part and a respiratory part.
• The nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles are part of the conducting portion.
• The respiratory bronchioles, alveolar ducts and alveoli are part of the respiratory portion.
• In the respiratory portion, gas exchange occurs, that is, oxygen taken from the external environment is made available to the blood, and carbon dioxide enters the respiratory system to perform the opposite path to oxygen and be eliminated to the environment.
• Breathing happens thanks to two breathing movements: inspiration and expiration.
• Respiration is dependent on the respiratory center in the medulla.

→ Organs of the respiratory system

 Respiratory System Organs And Functions: The organs of the respiratory system are: nasal passages, pharynx (nasopharynx), larynx, trachea, bronchi, bronchioles, alveoli and lungs . Here’s a little more about each of these important bodies:

• Nasal cavities : the first place through which air passes. In them it is possible to observe three regions: the vestibule, the respiratory area and the olfactory area. The vestibule is the anterior and dilated part of the nostrils, which communicates with the outside environment. The respiratory region corresponds to most of the nasal cavities. Finally, we have the olfactory area that corresponds to the upper part of the nasal cavities, which is rich in olfactory chemoreceptors.
• Pharynx : is a musculomembranous organ common to the digestive and respiratory systems. The part of the respiratory system is called the nasopharynx, while the digestive part is called the oropharynx. The nasopharynx is located posterior to the nasal cavity.
• Larynx : it is a tube about 5 cm long that has an irregular shape and acts ensuring the connection between the pharynx and the trachea. In the larynx, it is possible to perceive the so-called epiglottis, which is nothing more than a prolongation that extends from this organ towards the pharynx and prevents food from entering the respiratory system. In addition to the epiglottis , we find in the larynx the presence of the so-called vocal folds, which are responsible for the production of sound.
• Trachea : It is a tube formed by hyaline cartilages in the shape of a C, just after the larynx. The trachea branches giving rise to two bronchi, called primary bronchi.
• Bronchi : are branches of the trachea, which penetrate each one into a lung, through the hilum region. These bronchi, called the primary or main bronchi, enter the lungs and branch into three bronchi in the right lung and two in the left lung. These bronchi, called secondary or lobar, ramify giving rise to tertiary or segmental bronchi, which ramify giving rise to bronchioles.
• Bronchioles : they are branches of the bronchi, have a diameter of about 1 mm and do not have cartilage. These also branch, forming the terminal bronchioles and, later, the respiratory bronchioles. The respiratory bronchioles mark the transition to the respiratory part and open into the so-called alveolar duct.
• Pulmonary alveoli : they are structures that form part of the last portion of the bronchial tree and are located at the end of the alveolar ducts. They are similar to small pouches, have a thin epithelial wall and are the place where gas exchange takes place. Generally, the alveoli are organized into groups called the alveolar sac.
• Lungs : are cone-shaped organs that have a spongy consistency and have most of their parenchyma formed by the alveoli, with an estimated presence of about 300 million alveoli in the lungs. Each lung is lined with a membrane called the pleura. A child’s lung is usually pink in color, while an adult’s lung may have a darker color due to increased exposure to dust and soot.                                                                                 

The lungs have their parenchyma formed mainly by alveoli.

→ Conductive portion and respiratory portion

 Respiratory System Organs And Functions: We can divide the respiratory system into two parts: the conductive and the respiratory.

• Conducting portion : it is formed by the nasal passages, nasopharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles. As the name implies, this portion allows the entry and exit of air, but its function does not end there, it is in this part that the air is clean, humidified and heated.
• Respiratory portion : it is formed by the respiratory bronchioles, alveolar ducts and alveoli, which are the parts responsible for the occurrence of gas exchange. It is in this portion that the inspired oxygen will pass into the blood and the carbon dioxide present in the blood will pass into the respiratory system.

→ How does the respiratory system work?

The respiratory system works by ensuring the entry and exit of air from our body . Air initially enters through the nasal passages where it is moistened, heated and filtered. It then proceeds to the pharynx, later to the larynx and trachea. The trachea branches into two bronchi giving access to the lungs. Air then travels from the bronchi to the bronchioles and finally reaches the pulmonary alveoli.

Gas exchange takes place in the pulmonary alveoli.

Gas exchange occurs in the alveoli, a process also called hematosis. The oxygen present in the air that reaches the alveoli dissolves in the layer that covers this structure and diffuses through the epithelium to the capillaries located around the alveoli. In the opposite direction, the diffusion of carbon dioxide occurs.

→ Control of breathing in humans

 Respiratory System Organs And Functions: Humans have neurons in the medulla region that ensure the regulation of breathing . The medulla senses changes in the pH of the surrounding tissue fluid and triggers responses that warrant changes in respiratory rhythm.

When the levels of carbon dioxide increase in the blood and cerebrospinal fluid, there is a drop in pH. This is due to the fact that the carbon dioxide present in these places can react with water and trigger the formation of carbonic acid (H ₂ CO ₃ ). This can dissociate into bicarbonate ion (HCO ₃ ^– ) and hydrogen ions (H ⁺ ). The increase in hydrogen ions causes the pH to drop.

The medulla then senses these changes, and signals are sent to the intercostal muscles and diaphragm to increase the intensity and rate of respiration. When the pH returns to normal, there is a reduction in respiratory rate and intensity.

It is worth noting that changes in the level of oxygen in the blood trigger few effects in the bulb. However, when levels are too low, the respiration rate increases.

→ Inspiration and expiration

Breathing is achieved thanks to the performance of two breathing movements: inspiration and expiration.

Respiratory movements ensure the entry and exit of air.

• Inspiration: ensures the entry of air into the respiratory system. In this process, the diaphragm and intercostal muscles contract, leading to an expansion of the rib cage and a decrease in the pressure inside.
• Expiration: when air leaves the respiratory system. In this process, the thoracic muscles relax, as well as the diaphragm, leading to a reduction in the rib cage and an increase in internal pressure.
  

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