Pulmonary alveolus

alveolialveolarpulmonary alveolialveolustype II pneumocytepneumocytespneumocytealveolar sactype I pneumocytetype II alveolar cells
A pulmonary alveolus (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cup-shaped cavity found in the lung parenchyma where gas exchange takes place.wikipedia
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Gas exchange

pulmonary gas exchangegaseous exchangealveolar gas exchange
A pulmonary alveolus (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cup-shaped cavity found in the lung parenchyma where gas exchange takes place.
However, in most larger organisms, which have a small surface-area to volume ratios, specialised structures with convoluted surfaces such as gills, pulmonary alveoli and spongy mesophyll provide the large area needed for effective gas exchange.

Lung

lungspulmonaryright lung
Lung alveoli are found in the acini at the beginning of the respiratory zone. Alveoli are particular to mammalian lungs.
These divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.

Respiratory tract

airwayupper respiratory tractlower respiratory tract
Lung alveoli are found in the acini at the beginning of the respiratory zone.
Each of these bronchi branches into a secondary (lobar) bronchus that branches into tertiary (segmental) bronchi, that branch into smaller airways called bronchioles that eventually connect with tiny specialized structures called alveoli that function in gas exchange.

Pulmonary surfactant

lung surfactantsurfactantpulmonary surfactants
Type II cells release pulmonary surfactant to lower surface tension. Type II cells in the alveolar wall contain secretory granular organelles known as lamellar bodies that fuse with the cell membranes and secrete pulmonary surfactant.
Pulmonary surfactant is a surface-active lipoprotein complex (phospholipoprotein) formed by type II alveolar cells.

Parenchyma

parenchymallung parenchymaparenchymatous
A pulmonary alveolus (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cup-shaped cavity found in the lung parenchyma where gas exchange takes place.
Lung parenchyma is the substance of the lung outside of the circulation system that is involved with gas exchange and includes the alveoli and respiratory bronchioles,

Pores of Kohn

In the alveolar walls there are interconnecting air passages between the alveoli known as the pores of Kohn.
The pores of Kohn (also known as interalveolar connections) are discrete holes in walls of adjacent alveoli.

Mammal

mammalsMammaliamammalian
Alveoli are particular to mammalian lungs.
Air enters through the oral and nasal cavities, and travels through the larynx, trachea and bronchi, and expands the alveoli.

Alveolar duct

alveolar ducts
They are located sparsely on the respiratory bronchioles, line the walls of the alveolar ducts, and are more numerous in the blind-ended alveolar sacs.
Alveolar ducts are tiny ducts that connect the respiratory bronchioles to alveolar sacs, each of which contains a collection of alveoli (small mucus-lined pouches made of flattened epithelial cells).

Alveolar macrophage

Alveolar macrophagesmacrophages, alveolardust cell
Two types are pneumocytes known as type I and type II cells found in the alveolar wall, and a large phagocytic cell known as an alveolar macrophage that moves about in the lumens of the alveoli, and in the connective tissue between them.
An alveolar macrophage (or dust cell) is a type of macrophage, a professional phagocyte, found in the pulmonary alveoli, near the pneumocytes, but separated from the wall.

Molecular diffusion

concentration gradientdiffusion processesdiffusion
Across the membrane oxygen is diffused into the capillaries and carbon dioxide released from the capillaries into the alveoli to be breathed out.
For example, in the alveoli of mammalian lungs, due to differences in partial pressures across the alveolar-capillary membrane, oxygen diffuses into the blood and carbon dioxide diffuses out.

Lamellar bodies

Lamellar granulesextracellular lipid lamellaemultilamellar bodies
Type II cells in the alveolar wall contain secretory granular organelles known as lamellar bodies that fuse with the cell membranes and secrete pulmonary surfactant.
In cell biology, lamellar bodies (otherwise known as lamellar granules, membrane-coating granules (MCGs), keratinosomes or Odland bodies) are secretory organelles found in type II alveolar cells in the lungs, and in keratinocytes in the skin.

Blood–air barrier

blood-air barrieralveolar capillariesalveolar capillary beds
This also keeps the thickness of the blood-air barrier reduced to a minimum.
It exists to prevent air bubbles from forming in the blood, and from blood entering the alveoli.

Epithelium

epithelialepithelial cellsepithelial cell
These cells are extremely thin sometimes only 25 nm – the electron microscope was needed to prove that all alveoli are lined with epithelium.

Atelectasis

collapsecollapsed lunglung collapse
Insufficient surfactant in the alveoli is one of the causes that can contribute to atelectasis (collapse of part or all of the lung).
It is a condition where the alveoli are deflated down to little or no volume, as distinct from pulmonary consolidation, in which they are filled with liquid.

Pneumonia

bronchopneumoniabronchial pneumoniaNecrotizing pneumonia
Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli.

Pulmonary alveolar proteinosis

alveolar proteinosis
Impaired surfactant regulation can cause an accumulation of surfactant proteins to build up in the alveoli in a condition called pulmonary alveolar proteinosis.
Pulmonary alveolar proteinosis (PAP) is a rare lung disorder characterized by an abnormal accumulation of surfactant-derived lipoprotein compounds within the alveoli of the lung.

Phagocyte

phagocytesphagocytic cellsphagocytic
Two types are pneumocytes known as type I and type II cells found in the alveolar wall, and a large phagocytic cell known as an alveolar macrophage that moves about in the lumens of the alveoli, and in the connective tissue between them.
Macrophages are found throughout the body in almost all tissues and organs (e.g., microglial cells in the brain and alveolar macrophages in the lungs), where they silently lie in wait.

Infant respiratory distress syndrome

respiratory distress syndromehyaline membrane diseaserespiratory distress
However, adequate amounts of surfactant are not secreted until about 35 weeks of gestation – this is the main reason for increased rates of infant respiratory distress syndrome, which drastically reduces at ages above 35 weeks gestation.
Waxlike layers of hyaline membrane line the collapsed alveoli of the lung.

Hypersensitivity pneumonitis

alveolitisExtrinsic allergic alveolitisalveolitis, extrinsic allergic
It is an inflammation of the alveoli (airspaces) within the lung caused by hypersensitivity to inhaled organic dusts.

Bronchiole

bronchiolesbronchialrespiratory bronchiole
They are located sparsely on the respiratory bronchioles, line the walls of the alveolar ducts, and are more numerous in the blind-ended alveolar sacs.
They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start of the respiratory zone delivering air to the gas exchanging units of the alveoli.

Pneumatosis

emphysemaCongenital lobar emphysemaCompensatory emphysema
The spaces are caused by the breakdown of the walls of the alveoli and they replace the spongy lung parenchyma.

Pulmonary edema

pulmonary oedemapulmonary congestionacute pulmonary edema
Pulmonary edema is the build up of fluid in the parenchyma and alveoli usually caused by left ventricular heart failure, or by damage to the lung or its vasculature.
Pulmonary edema is fluid accumulation in the tissue and air spaces of the lungs.

Interstitial lung disease

interstitial pneumonitisinterstitial pneumoniapulmonary fibrosis
Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of lung diseases affecting the interstitium (the tissue and space around the alveoli (air sacs of the lungs).

Respiratory system

respiratoryrespirationrespiratory organs
Gas exchange in the lungs occurs in millions of small air sacs called alveoli in mammals and reptiles, but atria in birds.

Acute respiratory distress syndrome

ARDSacute lung injuryadult respiratory distress syndrome
It is typically provoked by an acute injury to the lungs that results in flooding of the lungs' microscopic air sacs responsible for the exchange of gases such as oxygen and carbon dioxide with capillaries in the lungs.