ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
The term MOUTH (or oral cavity) barely requires definition, but it is important to recognize the several different parts in and around the mouth. The PALATE is the roof of the mouth and is divided into the soft palate (at the rear) and the hard palate (at the front). The OROPHARYNX is that part of the mouth between the soft palate and the EPIGLOTTIS. Receptors in the oropharynx are important in signalling information about the foods and fluids present in the mouth to the brain. Behind the oropharynx is the PHARYNX—which is what, in everyday language, one would call the throat. It is obviously involved in the mechanics of swallowing food and water but, unlike the oropharynx, is not involved in detecting the composition of foods and fluids. The pharynx leads to both the TRACHEA (the windpipe) and the OESOPHAGOUS (esophagus in American spelling) The epiglottis is the flap of cartilage that covers the GLOTTIS—which is the opening to the LARYNX and the TRACHEA. The larynx is the upper part of the windpipe and is important in SPEECH PRODUCTION; the trachea connects to the bronchi in the lungs. The epiglottis functions to guard the trachea during swallowing of food, which is of course destined to travel down the oesophagous to the STOMACH.
The respiratory system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
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).
Preclinical Models for Pulmonary Drug Delivery
Anthony J. Hickey, Sandro R.P. da Rocha in Pharmaceutical Inhalation Aerosol Technology, 2019
The trachea, the conducting unit of the airways that links the upper and lower regions of the respiratory tract, is critical for respiration and is one of the few organs that shows a degree of uniformity across all mammals in terms of shape and size, particularly with relation to body size (Pinkerton et al. 2015). At the histological level, the trachea is made up of the mucosal epithelium (comprising ciliated and secretory epithelial cells, goblet cells, and clara or club cells), the submucosa (blood vessels, neurons and secretory glands throughout loose connective tissue), and a cartilaginous layer, trachealis muscle and outer adventitia. Variations between species at this level may impact on model suitability for pulmonary drug delivery studies (Table 30.2). Epithelial thickness, for example, ranges from <25 μm (in rodents) to 50 μm–100 μm (in larger models including human) (Reynolds 2015).
Investigation of airflow at different activity conditions in a realistic model of human upper respiratory tract
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Reza Tabe, Roohollah Rafee, Mohammad Sadegh Valipour, Goodarz Ahmadi
Velocity vectors within the trachea at sections R11 to R15 are presented in Figure 7. Here, the in-plane velocity vectors are shown for inhalation airflow rates of 30, 45, and 60 L/min. It is seen that the airflow pattern in the trachea is influenced by the upstream laryngeal jet. The velocity vectors shown in sections R11 to R15 demonstrate that the airflow pattern experiences significant variation as it crosses the trachea. The velocity vectors in the trachea are similar for three breathing rates studied and exhibit certain vortical structures. For 30 and 45 L/min, the formation of two vortices at R11 and R12 show the appearance of flow recirculation, due to the sudden opening of the passage. When the inspiratory flow rate reaches to 60 L/min, a small vortex near to the right wall, and a larger vortex close to the left wall are observed. At R13, near the right wall, a single vortex is formed, with a counter-clockwise rotation. Interestingly, compared to the 30, and 45 L/min breathing cases, the vortex is weaker for the 60 L/min breathing rate and tends to decay faster. Similar behavior was reported by Kleinstreuer and Zhang (2003) and Corcoran and Chigier (2000). When the airflow moves down the trachea, the secondary flow pattern decreases and becomes quite weak at R14 and R15 sections.
COPD: preclinical models and emerging therapeutic targets
Published in Expert Opinion on Therapeutic Targets, 2019
Esther Barreiro, Xuejie Wang, Jun Tang
Transportation of air to the lungs and from regions of gas exchange takes place through complex structures: nose, larynx, trachea, and the bronchi. In the respiratory tract, several types of cells are found that confer structure and immune protection against microorganisms and toxics. In humans and small and large laboratory animals, the respiratory system is divided into left and right lungs at the bifurcation of the trachea. From a cellular standpoint, it should be mentioned that from the trachea to the midlevel intralobar airways, different cell types have been identified: ciliated, mucous, and basal cells together with submucosal glands. The different cellular types that conform the structure of the lungs play individual roles in the pathophysiology of acute and chronic conditions [10]. Moreover, differences exist in the type of cells and structures among several species. Despite the reported differences, laboratory animals are commonly used within the frame of basic and translational research. They enable scientists to study the pathophysiological mechanisms and biological effects of inhaled environmental particles and noxious gases in the respiratory tract, namely the lungs and bronchi [10].
Influence of silica particles on mucociliary structure and MUC5B expression in airways of C57BL/6 mice
Published in Experimental Lung Research, 2020
Qimei Yu, Guoqing Fu, Hui Lin, Qin Zhao, Yuewei Liu, Yun Zhou, Yuqin Shi, Ling Zhang, Zhenyu Wang, Zhibing Zhang, Lingzhi Qin, Ting Zhou
The airway epithelial cells of trachea are pseudostratified ciliated columnar epithelium, which are composed of three principal cell types ciliated cells, goblet cells and basal cells, all of which are attached to the basal membrane. As shown in Figure 2A, the structure of pseudostratified ciliated columnar epithelium was normal and the cilia were well organized on the surface of airway epithelium mucosa in blank control and NS groups. After exposure to silica particles on day 1, the structure of airway epithelial cells seemed to be normal, but the height of ciliated epithelial cell layer became significantly shorter than that in blank control and NS groups (P < 0.05). On day 7, the structure of pseudostratified ciliated columnar epithelium was obviously damaged by silica particles, showing disorganized cilia and many goblet cells on the surface of airway epithelium. On days 28 and 84 after silica exposure, some cilia on the surface were short or absent, and parts of airway epithelium were differentiated into simple columnar epithelium or flattened epithelial cells. It was shown that silica particles significantly decreased the height of airway ciliated epithelium on day 28 and 84 when compared with blank control and NS groups (P < 0.05, Figure 2B).