scholarly journals Alveolar Duct

2020 ◽  
Author(s):  
Keyword(s):  
Alveolar Duct

A model for mechanical structure of the alveolar duct

1982 ◽  
Vol 52 (4) ◽  
pp. 1064-1070 ◽  
Author(s):  
T. A. Wilson ◽  
H. Bachofen
Keyword(s):  
Surface Tension ◽  
Lung Volume ◽  
Published Data ◽  
Scanning Electron Micrographs ◽  
Fiber System ◽  
Lung Capacity ◽  
Alveolar Duct ◽  
Tissue System ◽  
Line Elements ◽  
Air Liquid Interface

The appearance of the microstructure of the lung as revealed in transmission and scanning electron micrographs of perfusion-fixed air- and saline-filled lungs suggests the following model for the structure of the alveolar duct. There are two networks of force-bearing elements. The first is an interdependent part of the peripheral connective tissue system that starts from the pleura and extends into the interlobar and interlobular fissures. At the sublobular level, its geometry is not yet fully clear. This network is extended by changes in lung volume and is insensitive to surface tension. The second network is composed of the line elements that form the rims of the alveolar openings. This network is the terminal part of the axial fiber system that surrounds bronchi, bronchioli, and arteries. The line elements of this network are extended by the outward force of surface tension. The two-dimensional alveolar walls that form the alveoli are negligible mechanical components except as platforms for surface tension at the air-liquid interface. An analysis of the mechanics of this model yields relations among surface area, recoil pressure, lung volume, and surface tension that are consistent with published data for lung volumes below 80% of total lung capacity.

Lengths and topology of alveolar septal borders

1989 ◽  
Vol 67 (5) ◽  
pp. 1930-1940 ◽  
Author(s):  
E. H. Oldmixon ◽  
J. P. Butler ◽  
F. G. Hoppin
Keyword(s):  
Connective Tissue ◽  
Three Dimensional ◽  
Free Standing ◽  
And Topology ◽  
Section Area ◽  
Dimensional Reconstruction ◽  
Alveolar Duct ◽  
Mechanical Linkage ◽  
Alveolar Septa ◽  
Alveolar Parenchyma

To clarify the mechanics of alveolar parenchyma, we undertook a stereological and topological study in perfusion-fixed canine lungs of the borders of alveolar septa. We defined the principal borders as those along which one septum 1) joins two others (J), 2) joins one other at a distinct angle (B), or 3) joins no other structure (E). E and B borders are invariably reinforced with heavy connective tissue cables; J borders are not. Relative net lengths, determined from the number of traces per section area, were J, 45%; E, 19%; and B, 25%. These were remarkably constant over 10 canine lobes (5 animals, 4 volumes). Parenchyma, then, departs from the simple models that comprise only Js and Es. Bs are important; their net length exceeds that of Es. With lobe deflation, E shortened somewhat more than required to maintain geometric similarity, suggesting that the alveolar duct contracted disproportionately. A three-dimensional reconstruction was made from serial sections, and individual border segments were followed through the reconstruction. Typical lengths of individual J, B, and E borders were nearly equal. To characterize how the network of borders were interconnected, we counted the nodes at which they meet by class, e.g., EBE for the meeting of one B, two Es. The most common are JJJJ, 26%; EEEJ, 10%; EBJ, 24%; EBE, 8%; BBJJ, 12%. If parenchyma were constructed only from free-standing entrance rings and septal junctions, only JJJJ and EEEJ would be anticipated. The presence of EBJ, EBE, and BBJJ underscores parenchymal complexity. Only 7% of septa examined were bordered entirely by Js. Connective tissue cables were not confined to the alveolar duct's lumen but often extended to the primary septa at the periphery of the ductal unit. They rarely linked adjacent alveolar ducts; only 1 in 200 cable segments crossed from one duct to another. These observations support the concept that the parenchyma is an elastic network, characterized in part by a serial mechanical linkage from connective tissue cable to septal membrane to cable again.

Microscopic vs. macroscopic deformation of the pulmonary alveolar duct

1992 ◽  
Vol 72 (4) ◽  
pp. 1348-1354 ◽  
Author(s):  
D. Yager ◽  
H. Feldman ◽  
Y. C. Fung
Keyword(s):  
Human Lung ◽  
Lung Parenchyma ◽  
Stretch Ratio ◽  
Area Ratio ◽  
Force Balance ◽  
Load Carrying ◽  
Macroscopic Deformation ◽  
Alveolar Duct ◽  
Deformed State ◽  
Length And Area

The stretch of the perimeters of alveolar ducts was measured at the surface of saline-filled specimens of human and dog lung parenchyma that were stretched biaxially. The microscopic stretch of these ducts was measured at several levels of isotropic biaxial macroscopic stretch of the parenchyma with stretch ratio (lambda x = lambda y) in the range of 1.20–1.40, which roughly corresponds to tidal breathing in humans and dogs. Alveolar walls were found to be load-carrying elements in the saline-filled lung, as seen by their straightness at all levels of stretch. Quantitatively, let l, A, L, and S denote, respectively, the duct perimeter length and area and the parenchymal target perimeter and area in the deformed state and lo, Ao, Lo, and So the corresponding variables in the undeformed state. The microscopic stretch ratio of the ducts (l/lo) was found to be approximately 4% larger than the macroscopic stretch ratio (L/Lo) in human lung and approximately 10% larger in dog lung. The microscopic area ratio of the ducts (A/Ao) was found to be approximately 10% larger than the macroscopic area ratio (S/So) in human lung and approximately 22% larger in dog lung. Ducts within human parenchyma were seen to be about twice as stiff as ducts within dog parenchyma over the range of macroscopic stretch studied. This correlates with the volume fractions of collagen and elastin being higher in the human lung than in dog lung. The observed nonuniformity in strain field at the microstructural level suggests the need to include a force balance between alveolar ducts and septal walls when modeling the mechanics of saline-filled parenchyma.

Gas mixing in a model of the pulmonary acinus with asymmetrical alveolar ducts

1982 ◽  
Vol 52 (3) ◽  
pp. 624-633 ◽  
Author(s):  
C. Bowes ◽  
G. Cumming ◽  
K. Horsfield ◽  
J. Loughhead ◽  
S. Preston
Keyword(s):  
Molecular Diffusion ◽  
Dimensional Change ◽  
Normal Subjects ◽  
Mixing Efficiency ◽  
Gas Mixing ◽  
Alveolar Plateau ◽  
Pulmonary Acinus ◽  
Simple Boundary ◽  
Alveolar Duct ◽  
Asymmetrical Model

An asymmetrical model of the human pulmonary acinus is described, in which elements of volume are represented by nodes joined by conductors permitting convective flow and molecular diffusion. The method of analysis permits simultaneous convection, diffusion, and dimensional change in any direction and requires only simple boundary conditions. Inspiration of O2 into a resident gas of 79% N2 followed by expiration was simulated at two flows. On expiration the slope of the alveolar plateau was 1.7%, and the alveolar N2 mixing efficiency was 97.0%. A symmetrical but otherwise similar model gave a slope of zero and a mixing efficiency of 99.9%. The patterns of gas concentration within the asymmetrical acinus during the respiratory cycle confirm and extend previous observations on the interactions between simultaneous convection and diffusion in asymmetrical structures (16, 21, 22). Even though these in combination within alveolar duct asymmetry can account for the slope of the alveolar plateau, they are insufficient to account for the failure of complete gas mixing found in normal subjects.

scholarly journals Imaging alveolar-duct geometry during expiration via 3He lung morphometry

2011 ◽  
Vol 110 (5) ◽  
pp. 1448-1454 ◽  
Author(s):  
A. J. Hajari ◽  
D. A. Yablonskiy ◽  
J. D. Quirk ◽  
A. L. Sukstanskii ◽  
R. A. Pierce ◽  
...  
Keyword(s):  
Bonferroni Correction ◽  
The Past ◽  
Lung Physiology ◽  
Imaging Results ◽  
Duct Geometry ◽  
Alveolar Duct ◽  
The Subject ◽  
Lung Morphometry ◽  
Non Destructive

Acinar geometry has been the subject of several morphological and imaging studies in the past; however, surprisingly little is known about how the acinar microstructure changes when the lung inflates or deflates. Lung morphometry with hyperpolarized 3He diffusion MRI allows non-destructive evaluation of lung microstructure and acinar geometry, which has important applications in understanding basic lung physiology and disease. In this study, we have measured the alveolar and acinar duct sizes at physiologically relevant volumes by 3He lung morphometry in six normal, excised, and unfixed canine lungs. Our results imply that, during a 37% decrease in lung volume, the acinar duct radius decreases by 19%, whereas the alveolar depth increases by 9% ( P < 0.0001 and P < 0.05, respectively via paired t-tests with a Bonferroni correction). A comparison to serial sections under the microscope validates the imaging results and opens the door to in vivo human studies of lung acinar geometry and physiology during respiration using 3He lung morphometry.

Absence of Stellate Ganglion Influence on Alveolar-Duct Constriction1

1980 ◽  
Vol 121 (3) ◽  
pp. 603-605 ◽  
Author(s):  
Daniel J. Crittenden ◽  
David L. Beckman
Keyword(s):  
Stellate Ganglion ◽  
Alveolar Duct

Flow visualization in the expanding and contracting pulmonary alveolar duct

2019 ◽  
Vol 2019.32 (0) ◽  
pp. 2E12
Author(s):  
Naoki KAMIYA ◽  
Daichi FUKUSHIMA ◽  
Gaku TANAKA ◽  
Toshihiro SERA
Keyword(s):  
Flow Visualization ◽  
Alveolar Duct

scholarly journals Remodeling of alveolar septa after murine pneumonectomy

2015 ◽  
Vol 308 (12) ◽  
pp. L1237-L1244 ◽  
Author(s):  
Alexandra B. Ysasi ◽  
Willi L. Wagner ◽  
Robert D. Bennett ◽  
Maximilian Ackermann ◽  
Cristian D. Valenzuela ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Compensatory Growth ◽  
Lower Surface ◽  
Diameter Ratio ◽  
Temporal Association ◽  
Vascular Casting ◽  
Alveolar Duct ◽  
Synchrotron Imaging ◽  
Early Phases ◽  
Alveolar Septa

In most mammals, removing one lung (pneumonectomy) results in the compensatory growth of the remaining lung. In mice, stereological observations have demonstrated an increase in the number of mature alveoli; however, anatomic evidence of the early phases of alveolar growth has remained elusive. To identify changes in the lung microstructure associated with neoalveolarization, we used tissue histology, electron microscopy, and synchrotron imaging to examine the configuration of the alveolar duct after murine pneumonectomy. Systematic histological examination of the cardiac lobe demonstrated no change in the relative frequency of dihedral angle components (Ends, Bends, and Junctions) ( P > 0.05), but a significant decrease in the length of a subset of septal ends (“E”). Septal retraction, observed in 20–30% of the alveolar ducts, was maximal on day 3 after pneumonectomy ( P < 0.01) and returned to baseline levels within 3 wk. Consistent with septal retraction, the postpneumonectomy alveolar duct diameter ratio (Dout:Din) was significantly lower 3 days after pneumonectomy compared to all controls except for the detergent-treated lung ( P < 0.001). To identify clumped capillaries predicted by septal retraction, vascular casting, analyzed by both scanning electron microscopy and synchrotron imaging, demonstrated matted capillaries that were most prominent 3 days after pneumonectomy. Numerical simulations suggested that septal retraction could reflect increased surface tension within the alveolar duct, resulting in a new equilibrium at a higher total energy and lower surface area. The spatial and temporal association of these microstructural changes with postpneumonectomy lung growth suggests that these changes represent an early phase of alveolar duct remodeling.

Alveoli increase in number but not size from birth to adulthood in rhesus monkeys

2007 ◽  
Vol 293 (3) ◽  
pp. L570-L579 ◽  
Author(s):  
Dallas M. Hyde ◽  
Shelley A. Blozis ◽  
Mark V. Avdalovic ◽  
Lei F. Putney ◽  
Rachel Dettorre ◽  
...  
Keyword(s):  
Lung Volume ◽  
Rhesus Monkeys ◽  
Developmental Stages ◽  
Lung Parenchyma ◽  
Rate Of Change ◽  
Alveolar Volume ◽  
Lung Volumes ◽  
Male And Female ◽  
Female Rhesus ◽  
Alveolar Duct

Postnatal developmental stages of lung parenchyma in rhesus monkeys is about one-third that of humans. Alveoli in humans are reported to be formed up to 8 yr of age. We used design-based stereological methods to estimate the number of alveoli ( Nalv) in male and female rhesus monkeys over the first 7 yr of life. Twenty-six rhesus monkeys (13 males ranging in age from 4 to 1,920 days and lung volumes from 41.7 to 602 cm3, 13 females ranging in age from 22 to 2,675 days and lung volumes from 43.5 to 380 cm3) were necropsied and lungs fixed, isotropically oriented, fractionated, sampled, embedded, and sectioned for alveolar counting. Parenchymal, alveolar, alveolar duct core air, and interalveolar septal tissue volumes increased rapidly during the first 2 yr with slowed growth from 2 to 7 yr. The rate of change was greater in males than females. Nalv also showed consistent growth throughout the study, with increases in Nalv best predicted by increases in lung volume. However, mean alveolar volume showed little relationship with age, lung volume, or body weight but was larger in females and showed a greater size distribution than in males. Alveoli increase in number but not volume throughout postnatal development in rhesus monkeys.

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