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{{Short description|A detailed overview of the pulmonary alveolus, its structure, function, and significance in the respiratory system.}}
= Pulmonary Alveolus =


==Pulmonary Alveolus==
[[File:Alveolus_diagram.svg|thumb|right|Diagram of a pulmonary alveolus.]]
The '''pulmonary alveolus''' (plural: alveoli) is a tiny, balloon-shaped structure and is the basic unit of gas exchange in the [[lungs]]. Alveoli are located at the ends of the [[respiratory tree]] and are arranged in clusters throughout the lungs. They are crucial for the process of [[respiration]], allowing for the exchange of [[oxygen]] and [[carbon dioxide]] between the air and the [[bloodstream]].


[[File:Alveolus_diagram.png|thumb|right|Diagram of a pulmonary alveolus showing the capillary network.]]
The '''pulmonary alveolus''' (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cavity found in the [[lung]]s, and is the basic unit of [[respiration]]. The alveoli are the endpoint of the [[respiratory tree]], which includes the [[trachea]], [[bronchi]], and [[bronchioles]].


==Structure==
== Structure ==
Alveoli are microscopic in size, with an average diameter of about 200 to 300 micrometers. Each alveolus is surrounded by a network of [[capillaries]], which are the smallest blood vessels in the body. The walls of the alveoli are extremely thin, consisting of a single layer of [[epithelial cells]] known as type I and type II alveolar cells.


===Type I Alveolar Cells===
[[File:Bronchial_anatomy_with_description.png|thumb|left|Anatomy of the bronchial tree leading to the alveoli.]]
Type I alveolar cells, also known as squamous alveolar cells, cover about 95% of the alveolar surface area. These cells are thin and flat, facilitating the rapid diffusion of gases.


===Type II Alveolar Cells===
The alveoli are tiny, balloon-shaped structures and are the smallest passageway in the respiratory system. They are arranged in clusters throughout the lungs, with each cluster known as an [[alveolar sac]]. The walls of the alveoli are extremely thin, allowing for efficient [[gas exchange]] with the [[capillaries]] that surround them.
Type II alveolar cells, also known as great alveolar cells, are cuboidal in shape and are responsible for the production of [[surfactant]], a substance that reduces surface tension within the alveoli and prevents their collapse during exhalation.


==Function==
=== Alveolar Cells ===
The primary function of the alveoli is to facilitate the exchange of gases. Oxygen from inhaled air diffuses through the walls of the alveoli and enters the blood in the surrounding capillaries. Simultaneously, carbon dioxide from the blood diffuses into the alveoli to be exhaled.


[[File:Alveoli_gas_exchange.png|thumb|left|Illustration of gas exchange in the alveoli.]]
The alveolar walls are composed of two types of cells:


===Gas Exchange===
* '''Type I alveolar cells''': These are thin and flat cells that form the structure of the alveolar wall.
Gas exchange in the alveoli occurs by [[diffusion]], a process driven by the concentration gradients of oxygen and carbon dioxide. The high surface area and thin walls of the alveoli optimize this process, allowing for efficient gas exchange.
* '''Type II alveolar cells''': These cells secrete [[surfactant]], a substance that reduces surface tension and prevents the alveoli from collapsing.


===Role of Surfactant===
== Function ==
Surfactant plays a critical role in maintaining alveolar stability. By reducing surface tension, surfactant prevents the alveoli from collapsing and ensures that they remain open and functional throughout the respiratory cycle.


==Clinical Significance==
[[File:Cross_section_of_an_alveolus_and_capillaries_showing_diffusion_of_gases.svg|thumb|right|Cross-section of an alveolus showing gas exchange.]]
The health and function of the alveoli are vital for effective respiration. Conditions such as [[pneumonia]], [[emphysema]], and [[acute respiratory distress syndrome]] (ARDS) can impair alveolar function and lead to respiratory distress.


===Pneumonia===
The primary function of the alveoli is to exchange oxygen and carbon dioxide molecules to and from the bloodstream. This process is known as [[gas exchange]]. Oxygen from the inhaled air diffuses through the walls of the alveoli and into the blood in the capillaries, while carbon dioxide from the blood diffuses into the alveoli to be exhaled.
Pneumonia is an infection that inflames the air sacs in one or both lungs, which may fill with fluid or pus, leading to impaired gas exchange.


===Emphysema===
== Gas Exchange Process ==
Emphysema is a chronic condition characterized by the destruction of alveolar walls, resulting in reduced surface area for gas exchange and difficulty breathing.


===Acute Respiratory Distress Syndrome===
[[File:Gas_exchange_in_the_aveolus.svg|thumb|left|Diagram showing gas exchange in the alveolus.]]
ARDS is a severe condition characterized by widespread inflammation in the lungs, leading to fluid accumulation in the alveoli and impaired oxygenation.


==Related Pages==
Gas exchange occurs by [[diffusion]], a process driven by the concentration gradients of the gases. Oxygen, which is more concentrated in the alveoli than in the blood, diffuses into the blood, while carbon dioxide, which is more concentrated in the blood, diffuses into the alveoli.
 
== Clinical Significance ==
 
[[File:Cryptococcosis_of_lung_in_patient_with_AIDS._Mucicarmine_stain_962_lores.jpg|thumb|right|Cryptococcosis infection in the lung.]]
 
Diseases affecting the alveoli can severely impact respiratory function. Conditions such as [[pneumonia]], [[emphysema]], and [[pulmonary fibrosis]] can damage the alveoli, leading to impaired gas exchange. Infections like [[cryptococcosis]] can also affect the alveoli, particularly in immunocompromised individuals.
 
== Related Pages ==
 
* [[Lung]]
* [[Respiratory system]]
* [[Respiratory system]]
* [[Lung]]
* [[Gas exchange]]
* [[Gas exchange]]
* [[Surfactant]]
* [[Surfactant]]
* [[Capillary]]


[[Category:Respiratory system]]
[[Category:Respiratory system]]
[[Category:Anatomy]]
[[Category:Anatomy]]

Revision as of 14:17, 21 February 2025

Pulmonary Alveolus

Diagram of a pulmonary alveolus.

The pulmonary alveolus (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cavity found in the lungs, and is the basic unit of respiration. The alveoli are the endpoint of the respiratory tree, which includes the trachea, bronchi, and bronchioles.

Structure

Anatomy of the bronchial tree leading to the alveoli.

The alveoli are tiny, balloon-shaped structures and are the smallest passageway in the respiratory system. They are arranged in clusters throughout the lungs, with each cluster known as an alveolar sac. The walls of the alveoli are extremely thin, allowing for efficient gas exchange with the capillaries that surround them.

Alveolar Cells

The alveolar walls are composed of two types of cells:

  • Type I alveolar cells: These are thin and flat cells that form the structure of the alveolar wall.
  • Type II alveolar cells: These cells secrete surfactant, a substance that reduces surface tension and prevents the alveoli from collapsing.

Function

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Cross-section of an alveolus showing gas exchange.

The primary function of the alveoli is to exchange oxygen and carbon dioxide molecules to and from the bloodstream. This process is known as gas exchange. Oxygen from the inhaled air diffuses through the walls of the alveoli and into the blood in the capillaries, while carbon dioxide from the blood diffuses into the alveoli to be exhaled.

Gas Exchange Process

Error creating thumbnail:
Diagram showing gas exchange in the alveolus.

Gas exchange occurs by diffusion, a process driven by the concentration gradients of the gases. Oxygen, which is more concentrated in the alveoli than in the blood, diffuses into the blood, while carbon dioxide, which is more concentrated in the blood, diffuses into the alveoli.

Clinical Significance

Error creating thumbnail:
Cryptococcosis infection in the lung.

Diseases affecting the alveoli can severely impact respiratory function. Conditions such as pneumonia, emphysema, and pulmonary fibrosis can damage the alveoli, leading to impaired gas exchange. Infections like cryptococcosis can also affect the alveoli, particularly in immunocompromised individuals.

Related Pages

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