He Pulmonary parenchyma Is the portion of the lung involved in the Hematosis Or gas transfer. This includes alveoli, alveolar conduits, and Respiratory bronchioles .
Some definitions also include other structures and tissues within the lung parenchyma.
The lungs are organs with a complex internal structure that evolved to provide the body's gas exchange needs.
The pulmonary anatomy can be divided into two segments: the upper airway, which includes the supraglottic, infraglottic and glottic regions; And the lower airway, which includes the trachea and bronchi.
Pulmonary anatomy also includes the pulmonary parenchyma, which performs part of the conduction system but is primarily involved in the exchange of gases at an alveolar level.
In turn, the lung parenchyma is subdivided into several lobes and segments. Primarily, the pulmonary parenchyma comprises a large number of thin alveolar walls forming a large surface. This serves to maintain the correct gas exchange.
The alveoli are kept open by transpulmonary pressure, which is balanced by tissue forces and alveolar forces.
In this way, the efficiency of gas exchange is inextricably related to three fundamental characteristics of the lung: parenchyma architecture, prestressing and mechanical properties of the parenchyma.
You may be interested Pulmonary Breathing: Features, Process, Phases and Anatomy .
The pulmonary parenchyma and its structure
Alveoli
The alveoli are minimal empty air sacs which comprise the basic unit of respiration.
The alveoli are found within the lung parenchyma and at the ends of the respiratory tree, distributed around the sacs and alveolar ducts.
Each alveolus measures approximately 0.2 mm in diameter. There are about 300 million to 1 million alveoli in the human lungs, covering an area of about 70 square meters.
The walls of the alveoli are composed of collagen and elastic fibers that facilitate expansion during inspiration and return to their original shape during expiration.
There are numerous capillaries within the walls of the alveoli where gas exchange occurs. Kohn's pores are also located inside the walls.
The alveoli contain two major types of epithelial cells. The most abundant type, Pneumocytes type I (95%), are squamous cells in which gas exchange occurs.
The remaining 5%, formed of Pneumocytes type II, are granular cells that secrete surfactant. Surfactant is a lipoprotein with a high phospholipid content that reduces surface tension.
This process is necessary as it increases lung compaction, prevents atelectasis and aids in recruitment in the collapsed airways.
Alveolar macrophages are also located in the alveoli. When wrapped, they protect the alveoli from any foreign material, including bacteria, dust and carbon particles.
Bronchioles
Bronchioles are the routes through which air passes through the nose or mouth into the alveoli of the lungs; In these branches there are no cartilages or glands in their sub mucosa.
The bronchioles are branches of the bronchi and are part of the conductive area of the respiratory system.
The bronchioles are divided into smaller terminal bronchioles, which are also in the conducting zone so that they then divide into smaller respiratory bronchioles that mark the beginning of the respiratory region.
The bronchioles measure approximately 1 mm in diameter and their walls consist of cubic cilia epithelium and a layer of soft muscle. The bronchioles are divided into smaller bronchioles, called terminals, which measure 0.5 mm in diameter.
In turn, the terminal bronchioles are divided into respiratory bronchioles that divide into alveolar ducts. The terminal bronchioles mark the end of the conductive division of airflow into the respiratory system.
In turn, respiratory bronchioles involve the onset of respiratory division where hematosis occurs. The diameter of the bronchioles plays an important impact on the airflow. The bronchioles change in diameter to increase or reduce airflow.
A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors that decrease airflow.
- Terminal bronchioles
It is the most distal segment of the conducting zone; Branches to the smaller bronchioles. Each of the terminal bronchioles is divided to form respiratory bronchioles containing a small number of alveoli.
The terminal bronchioles are covered with cubic epithelium; Which contains cells secreting protein. These secretions help keep the air in the smaller bronchioles.
These secreted proteins also help the bronchioles expand during inspiration and not collapse during expiration.
- Respiratory bronchioles
Respiratory bronchioles are the narrowest airways in the lungs. The bronchus is divided many times until it evolves in the bronchioles. Bronchioles carry air to the exchange surfaces of the lungs.
They are interrupted by alveoli which are outer layers with thin walls. The alveolar ducts are distal continuations of the respiratory bronchioles.
Alveolar ducts
The alveolar ducts are small ducts that connect the respiratory bronchioles with the alveolar sacs; Each contains a collection of alveoli.
These structures are tiny ducts of the branches of the airways that fill the lungs. Each lung contains approximately 1.5 to 2 million of them. These tubules are divided into two or three alveolar sacs at the distal termination.
These ducts are formed from the confluent openings of several alveoli. The distal ends of the alveolar ducts are atria which then terminate in alveolar sacs.
In human anatomy, respiratory bronchioles exist in close proximity to the alveolar ducts. The epithelial lining consists of soft muscle knots covered by simple cuboidal cells. The soft muscle contracts under parasympathetic innervation and relaxes under sympathetic innervation.
References
- Lung anatomy (2016). Retrieved from emedicine.medscape.com.
- Alveoli. Retrieved from radiopaedia.org.
- Bronchiole. Retrieved from wikipedia.org.
- Bronchioles. Retrieved from radiopaedia.org.
- Lung Parenchymal Mechanics (2014). Retrieved from ncbi.nlm.nih.gov.
- Alveolar duct. Retrieved from wikipedia.org.
- Lung parenchyma. Retrieved from radiopaedia.org.