Type 2 pneumocyte: The cell responsible for the production and secretion of surfactant (the molecule that reduces the surface tension of pulmonary fluids and contributes to the elastic properties of the lungs).
What is the difference between Type 1 and type 2 pneumocytes?
Type 1 pneumocytes are thin flattened cells that are responsible for the gas exchange between alveoli and capillaries. Type 2 pneumocytes are smaller cells that are cuboidal in shape. They are responsible for the secretion of pulmonary surfactants in order to reduce the surface tension in the alveoli.
What is type 2 pneumocytes of alveoli?
walls are a group called granular pneumocytes (Type II cells), which secrete surfactant, a film of fatty substances believed to contribute to the lowering of alveolar surface tension. Without this coating, the alveoli would collapse and very large forces would be required to re-expand them.
What are type I pneumocytes and what are 2 characteristics?
Type I pneumocytes cover 95% of the internal surface of each alveolus. These cells are thin and squamous, ideal for gas exchange. They share a basement membrane with pulmonary capillary endothelium, forming the air-blood barrier where gas exchange occurs.
What does Type II Pneumocyte damage cause?
Injury to the type II pneumocytes can reduce the production of surfactant, which contributes to the clinical course of worsening atelectasis and gas exchange. The process of epithelial repair is usually inadequate, leading to fibrosis (Zapol et al., 1979a).
What are the functions of type 1 and 2 pneumocytes and the alveolar macrophage?
Typically, type 1 alveolar cells comprise the major gas exchange surface of the alveolus and are integral to the maintenance of the permeability barrier function of the alveolar membrane. Type 2 pneumocytes are the progenitors of type 1 cells and are responsible for surfactant production and homeostasis.
What do type 1 pneumocytes secrete?
The type I cell is responsible for gas exchange and the type II cell synthesizes and secretes surfactant. At birth the lung has no mature alveoli but instead contains approximately 20 million primitive terminal sacs. These sacs are lined by mature alveolar epithelium; they resemble large shallow cups.
Where are type 2 pneumocytes found?
Type II pneumocytes were found to be preferentially located on thick elastic fibers which formed the main structural framework of the alveoli in humans.
Which pneumocytes produce surfactant?
Type II pneumocytes are thicker with a more spherical shape and are responsible for the production and secretion of the pulmonary surfactant.
Can type 2 pneumocytes regenerate?
Type II pneumocytes are known to produce surfactant and regenerate alveolar epithelium after injury.
What is the main role of surfactant?
Function. The main functions of surfactant are as follows: (1) lowering surface tension at the air–liquid interface and thus preventing alveolar collapse at end-expiration, (2) interacting with and subsequent killing of pathogens or preventing their dissemination, and (3) modulating immune responses.
How does surfactant prevent alveolar collapse?
Surfactant is released from the lung cells and spreads across the tissue that surrounds alveoli. This substance lowers surface tension, which keeps the alveoli from collapsing after exhalation and makes breathing easy.
How does surfactant affect pulmonary ventilation?
The surfactant reduces surface tension within all alveoli through hydrophilic and hydrophobic forces. Insufficient pulmonary surfactant in the alveoli can contribute to atelectasis (collapse of part or all of the lung ).
During which phase of fetal pulmonary development do the type II pneumocytes become numerous and begin to produce and store surfactant?
During week 20, lamellar bodies begin to appear in the cytoplasm of the cuboidal type II pneumocytes lining the distal epithelium. Lamellar bodies store pulmonary surfactant, composed of lipids and Surfactant Proteins A-C, before exocytotic release into the alveoli.
