The Cardiovascular System and its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
The heart is located in the center of the thorax as part of the mediastinum, the partition near the middle of the thorax, which contains the heart, large arteries, the great veins, and parts of several other systems (trachea and bronchi of the respiratory system and the esophagus of the digestive system, for example). The heart acts as a pump, using the contractile force of the myocardium to force blood from the left ventricle into the aorta and on to the systemic circulation.
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).
The respiratory system
C. Simon Herrington in Muir's Textbook of Pathology, 2020
The trachea divides into the left and right main bronchi. The right continues in the general direction of the trachea; the left diverges at a greater angle. Thus, aspiration is more common in the right lung, especially the middle and lower lobes. Bronchial cartilage progressively decreases with increasing distance from the trachea. At the terminal bronchiole (sixteenth division), it has disappeared. The airways continue dividing into respiratory bronchioles, alveolar ducts, and finally alveoli (Figure 8.1). The terminal bronchiole is the smallest airway that is lined by bronchial epithelial cells. The terminal bronchiolar walls consist almost entirely of smooth muscle. The small bronchioles, i.e. terminal and those just proximal, play a larger role in determining airflow than the bronchi. This is because they have much more smooth muscle, which constricts easily. As they are small, they are easily occluded, as in bronchial asthma and chronic obstructive pulmonary disease. The respiratory bronchiole bears alveoli.
Nanocrystals based pulmonary inhalation delivery system: advance and challenge
Published in Drug Delivery, 2022
Pengfei Yue, Weicheng Zhou, Guiting Huang, Fangfang Lei, Yingchong Chen, Zhilin Ma, Liru Chen, Ming Yang
The lungs are the organs that contact with the exchange of air between the organism and the outside world. They are divided into two main regions: the conducting airway region and the respiratory region. The airway is a continuous branch from the bronchi to the lungs and consists mainly of bronchi, bronchioles, and terminal bronchioles. As the bronchi continue to branch, the diameter of the tubes becomes smaller, the tube wall becomes thinner, and the structure of the tube wall changes gradually. The annular smooth muscles of the bronchi contract or relax under splanchnic nerves innervation and it is responsible for the regulation of airflow passage into the alveoli. This is the site where the lung tissue completes gas exchange consisting of respiratory bronchioles, alveolar ducts, lung sacs, and alveoli. The respiratory bronchiole is the transitional pipes between the pulmonary airway and the respiratory site. Each respiratory bronchiole branch is divided into 2–3 alveolar ducts. The alveolar sacs are the common opening of several alveoli and are connected to the alveolar ducts. The gut is the main site for the digestion and absorption of nutrients.
The role of the solid state and physical properties of the carrier in adhesive mixtures for lung delivery
Published in Expert Opinion on Drug Delivery, 2018
Andrea Della Bella, Enrico Salomi, Francesca Buttini, Ruggero Bettini
The lung represents an efficient aerodynamic filter which hinders the access and deposition of exogenous agents such as dust in the lower airways. The branched structure of respiratory tract is described by Weibel’s model [6] that distinguishes 23 subsequent bifurcations starting at the trachea (generation 0) and finishing at the alveolar sacs (generation 23) [7]. Two main compartments can be identified: the conducting region (generations 0–16) and the respiratory region (generations 17–23). The conducting airways, whose function is to transport the air from the external environment into the lungs and vice versa, are represented by the trachea that bifurcates into two principal bronchi which in turn branch in bronchioles with a progressively smaller diameter. The respiratory airways start with the respiratory bronchioles and include all the structures that participate in the gas exchange (i.e. alveolar ducts and sacs).
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].
Related Knowledge Centers
- Azygos Vein
- Bronchiole
- Gas Exchange
- Respiratory Tract
- Thoracic Vertebrae
- Trachea
- Lung
- Carina of Trachea
- Root of The Lung
- Sternal Angle