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Respiratory Tract
Published in George W. Casarett, Radiation Histopathology: Volume II, 2019
The primary bronchi branch into secondary bronchi, and these into bronchioles, then terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli (Figure 1A). The mucous membrane of the bronchi is continuous with that of the trachea and is of the same type (Figure 1B). The pseudostratified ciliated columnar epithelium rests on a basement membrane separating it from the lamina propria. Small cuboidal cells are found on the basement membrane in the epithelium of the trachea, bronchi, and their branches, and are usually the cells which divide when required to replace the more specialized cells which are lost. The turnover time of bronchial epithelium is relatively long.
Respiratory disorders
Published in Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize, Developmental and Adapted Physical Education, 2019
Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize
Air enters through the nasal cavity from the nose and/or mouth (which warms, filters, and humidifies the air) and then empties into the pharynx and trachea, or windpipe, before entering the lungs. The air enters the lungs through the primary bronchi, which branch into additional smaller passageways called bronchioles, and finally enters into the alveoli, the tiny balloon-like air sacs in which oxygen and carbon dioxide are exchanged.
The respiratory system
Published in Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella, Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella
Air is carried to and from the lungs by the trachea, which extends toward the lungs from the larynx. The trachea divides into the right and left primary (main) bronchi. These primary bronchi each supply a lung. The primary bronchi branch and form the secondary, or lobar, bronchi; one for each lobe of lung. The left lung consists of two lobes and the right lung has three lobes. The lobar bronchi branch and form the tertiary, or segmental, bronchi; one for each of the functional segments within the lobes. These bronchi continue to branch and move outward toward the periphery of the lungs. The smallest airways without alveoli are the terminal bronchioles. Taken all together, the airways from the trachea through and including the terminal bronchioles are referred to as the conducting airways. This region, which consists of the first 16 generations of airways, contains no alveoli. Therefore, there is no gas exchange in this area. Consequently, it is also referred to as anatomical dead space. The volume of the anatomical dead space is approximately 150 mL (or about 1 mL per pound of ideal body weight).
Simulation of respiratory tract lining fluid for in vitro dissolution study
Published in Expert Opinion on Drug Delivery, 2021
Rakesh Bastola, Paul M. Young, Shyamal C. Das
The respiratory system consists of mouth and nose, pharynx, larynx, trachea, bronchi, bronchioles and alveoli [9]. The pharynx is approximately 12–15 cm in length and it is divided into nasopharynx, oropharynx and laryngopharynx [10]. The larynx works as a sphincter and transmits air from oropharynx and nasopharynx to the trachea [11]. The trachea is divided into the left and right primary bronchi. Each bronchus is divided into secondary bronchi, which are further divided into many tertiary bronchi. Branching of tertiary bronchi gives many tiny bronchioles which finally, lead to terminal and respiratory bronchioles. Respiratory bronchioles are further divided into alveolar ducts which end at the alveoli (alveolar sacs) [11]. There are more than 300 million alveoli in the lungs. Each alveolus is lined with pulmonary capillaries, which forms a massive network that includes more than 280 billion capillaries with a surface area of around 70 m2 [12].
Endogenous lung stem cells for lung regeneration
Published in Expert Opinion on Biological Therapy, 2019
The luminal surface of the entire airway tract is lined by a continuous epithelial layer, which, in addition to facilitating airflow, functions as a physical barrier to the external environment and serves vital functions in mucosal immunity, microbial defense and mucociliary clearance [36]. Based on structure and function, mammalian airways can be conceptually divided into upper and lower regions, which vary in relative distribution, abundance, and type of epithelial cells. The upper cartilaginous airways (i.e. trachea and primary bronchi) are the first line of defence against everything we inhale; hence, the epithelium is mostly composed of mucus-secreting goblet cells and ciliated cells, which are central to respiratory host defence. Invagination of upper airway epithelium also forms submucosal glands, which harbor ciliated cells, goblet cells, and serous cells, which secrete electrolytes, antioxidants and antimicrobial peptides [37]. The lower conducting airways (i.e. bronchioles), which are largely composed of secretory cells and ciliated cells, facilitate airflow distribution to the alveoli, thereby aiding in the essential process of breathing.
Recent insights into human bronchial proteomics – how are we progressing and what is next?
Published in Expert Review of Proteomics, 2018
Heng Wee Tan, Yan-Ming Xu, Dan-Dan Wu, Andy T. Y. Lau
Human beings are air-breathing vertebrates vitally dependent on oxygen (O2) for survival. We inhale O2 and exhale carbon dioxide (CO2) via a rather complex set of respiratory system involving several anatomically distinct body structures and organs [1]. The human respiratory system consists of three main regions: the extrathoracic, tracheobronchial, and alveolar regions. As illustrated in Figure 1, the left and right primary bronchi are located in the tracheobronchial region. Each of the primary bronchi is further branching into smaller units, namely the bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, and clusters of tiny air-filled sacs, the alveoli. These units are the main components of the human lung. Typical adult human lungs have about 250–750 million alveoli, depending on the size and volume of the lungs [2]. The alveoli are surrounded by a fine network of capillaries where the passive exchange of O2 and CO2 between the external air and the blood occurs via diffusion.