Lung Cell Biology

Weibel, Ewald R.

doi:10.1002/cphy.cp030102

Cited by 24 publications

(11 citation statements)

References 117 publications

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“…The capillaries, originally loosely spread in the vast mesenchyme, now approach the saccular surfaces forming a denser network closely apposed to the epithelial basement membrane. The saccular epithelium differentiates into the secretory alveolar type-2 cells that begin to produce surfactant, and the thin and vast squamous type-1 cells that form the potential air-blood barrier together with the apposed capillary endothelial cells (382). …”

Section: Origin and Architecture Of The Mammalian Lungmentioning

confidence: 99%

“…For one they are responsible for the formation and maintenance of the fiber system. They also form elements of myofibroblasts, mostly in the form of focal actomyosin bundles that span across the septum from the basement membrane of one epithelial cell to that on the other side thus serving as braces of the interstitial space (382). The support function of these interstitial structures becomes accentuated at the free edge of the septum where a strong alveolar entrance ring made of connective tissue fibers and some smooth muscle cells forms (Fig.…”

Section: Structure-function Correlationsmentioning

confidence: 99%

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Lung Structure and the Intrinsic Challenges of Gas Exchange

Hsia

Hyde

Weibel

2016

Comprehensive Physiology

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Structural and functional complexities of the mammalian lung evolved to meet a unique set of challenges, namely, the provision of efficient delivery of inspired air to all lung units within a confined thoracic space, to build a large gas exchange surface associated with minimal barrier thickness and a microvascular network to accommodate the entire right ventricular cardiac output while withstanding cyclic mechanical stresses that increase several folds from rest to exercise. Intricate regulatory mechanisms at every level ensure that the dynamic capacities of ventilation, perfusion, diffusion, and chemical binding to hemoglobin are commensurate with usual metabolic demands and periodic extreme needs for activity and survival. This article reviews the structural design of mammalian and human lung, its functional challenges, limitations, and potential for adaptation. We discuss (i) the evolutionary origin of alveolar lungs and its advantages and compromises, (ii) structural determinants of alveolar gas exchange, including architecture of conducting bronchovascular trees that converge in gas exchange units, (iii) the challenges of matching ventilation, perfusion, and diffusion and tissue-erythrocyte and thoracopulmonary interactions. The notion of erythrocytes as an integral component of the gas exchanger is emphasized. We further discuss the signals, sources, and limits of structural plasticity of the lung in alveolar hypoxia and following a loss of lung units, and the promise and caveats of interventions aimed at augmenting endogenous adaptive responses. Our objective is to understand how individual components are matched at multiple levels to optimize organ function in the face of physiological demands or pathological constraints.

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Section: Origin and Architecture Of The Mammalian Lungmentioning

confidence: 99%

Section: Structure-function Correlationsmentioning

confidence: 99%

Lung Structure and the Intrinsic Challenges of Gas Exchange

Hsia

Hyde

Weibel

2016

Comprehensive Physiology

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158

137

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“…The ultrastructural morphology of the AMs has been well-documented (e.g. Weibel, 1984Weibel, , 1985. Remarkably heteromorphic, they vary in size from 10 to 40 μm in diameter, constitute 2 to 9% of the pneumocytes, and have an indented (bean = horse shoe-shaped) eccentrically located nucleus (e.g.…”

Section: Pulmonary Surface (Free) Macrophages (Psms)mentioning

confidence: 99%

“…Remarkably heteromorphic, they vary in size from 10 to 40 μm in diameter, constitute 2 to 9% of the pneumocytes, and have an indented (bean = horse shoe-shaped) eccentrically located nucleus (e.g. Sebring and Lehnert, 1992;Weibel, 1984Weibel, , 1985 (Fig. 12).…”

Section: Pulmonary Surface (Free) Macrophages (Psms)mentioning

confidence: 99%

Cellular Defences of the Lung: Comparative Perspectives

Maina¹

2012

Respiratory Diseases

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'Our lungs are highly complex organs that are exquisitely specialized for gas exchange and host defense.' Rawlins (2010) 1. Introduction General considerationsThe most important function of the lung is to acquire molecular oxygen and eliminate carbon dioxide. Except probably for the gastrointestinal system, no other organ in the body interacts with the external environment as constantly and as intimately as the respiratory system. For example, during a 24 hour period, at rest, the human lung is ventilated ~25,000 times with ~20,000 L of air (e.g. Burri, 1985; Brain, 1996), it has a respiratory surface area (RSA) of ~140 m 2 (about the size of a tennis court) which is located in the acini that lie no more than 40 to 50 cm from the external environment (air) (e.g. Weibel, 1984), and the thickness of the blood-gas (tissue) barrier (BGB) (harmonic mean thickness, ht) is 0.62 μm, a value about one-fiftieth of the thickness of a foolscap paper or that of a human head hair (Gehr et al., 1978(Gehr et al., , 1990a. By weight, each day, more than 20 kg of air enters and leaves the human body, a load that far exceeds that of food and water ingested during the same time period (Brain, 1996). Depending on the level of air pollution, different types and quantities of foreign particulates and microbial pathogens are inhaled. While large RSA and thin BGB increase gas exchange, the concomitant downside to these structural properties is that they make the lung a leading portal of entry and therefore attack by pathogenic micro-organisms, damage by allergens and particulates, and injury by noxious gases (e.g. Brain, , 1992Lambrecht et al. 2001;Garn et al., 2006). The inhaled particulates are deposited on the epithelial lining of the conducting airways and that of the peripheral air spaces where they are retained for various durations before they are removed or destroyed (e.g. Geiser et al., 1988; Gehr et al., 1990 a, b). Brain (1996) observed that 'the lung is unique in that the marriage between environment and lung disease is profound. The respiratory system threfore forms a huge challenge to the body's immune integrity (e.g. von Garnier and Nicod, 2009 , 1993;Schwartz, 1994;Brunekreef et al., 1995;Ware, 2000;Pope, 2000;Nemmar et al., 2002;Pope et al., 2002;Suwa et al., 2002;Schulz et al., 2005;Kaufman, 2010;Brook et al., 2010; van den Hooven et al., 2011;Kampfrath et al., 2011 gc.ca/ccdpc-cpcmc/crdmrc/facts_gen_e.html). According to the Canadian Lung Association (CLA), the economic burden of respiratory disease in the Country is ~3 billion ($US) dollars (http://www.bukisa.com/articles/455926_lung-health-occupational-healthincidence#ixzz1I4jwMvBX). Based on net changes in gross domestic product (GDP) growth forecasts, the estimated annual cost of SARS (Sudden Avian Respiratory Syndrome) in Asia exceeds 10 billion dollars ($US) (Lee and McKibbin, 2003;Fan, 2003;McKibbin and Sidorenko, 2006) and according to the World Bank's estimates, an influenza pandemic may result in a loss (expenditure) of 800 billion dollars ($US) (Brahm...

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“…17,21,25,26 Indeed, several IPRL studies have reported airway fluid resorption rates of 27-34 pL/cm 2 /s, 17,21,25,26 or 0.5-0.6 mL/h, assuming an alveolar surface area ¼ 0.5 m 2 in the rat. 27 The process is tightly regulated by apical Na þ channels (ENAC) and basolateral Na þ /K þ -ATPase on alveolar epithelium and, hence, is largely cellular energy-dependent. 17,21,25,26 The fact that this active process for airway fluid resorption in the IPRL can also be inhibited or suppressed by the perturbations used to discern mechanisms for F-PHEA absorption, is an unfortunate characteristic of experiments like these.…”

Section: Macromolecular Absorption and Mechanisms From The Lungmentioning

confidence: 99%