<unk>  is a condition where pulmonary<unk>  is insufficient for adequate respiration. Surface tension at the liquid-air interphase in the alveoli makes the air sacs prone to collapsing post expiration. This is due to the fact that water molecules in the liquid-air surface of alveoli are more attracted to one another than they are to molecules in the air. For sphere-like structures like alveoli, water molecules line the inner walls of the air sacs and stick tightly together through hydrogen bonds. These intermolecular forces put great restraint on the inner walls of the air sac, tighten the surface all together, and unyielding to stretch for inhalation. Thus, without something to alleviate this surface tension, alveoli can collapse and cannot be filled up again.<unk>  is essential mixture that is released into the air-facing surface of inner walls of air sacs to lessen the strength of surface tension. This mixture inserts itself among water molecules and breaks up hydrogen bonds that hold the tension. Multiple lung diseases, like ISD or RDS, in newborns and late-onsets cases have been linked to<unk>  of<unk><unk> .<unk>  is a mixture of 90% phospholipids and 10% other proteins, produced by epithelial type II cells in the alveolar. This mixture is made and packaged into lysosomally- derived structures called lamellar bodies. Lamellar bodies are then secreted into the liquid-air interphase surface of alveolar through membrane fusion initiated by influx of Ca2+. Released pulmonary<unk>  acts as a protective layer to prevent alveolar from collapsing due to surface tension. Furthermore,<unk> s also contains some innate immune components to defend against pulmonary infections.<unk>  is classified into two types of proteins, hydrophilic proteins that are responsible for innate immune system, and hydrophobic proteins that carry out physical functions of pulmonary<unk> .<unk>  involves mutations or malfunctions of those hydrophobic proteins that lead to ineffective<unk>  layer to protect alveolus integrity. SP-B and SP-C are the two hydrophobic<unk>  proteins that participate in its physical functions; these proteins are encoded by SFTPB and SFTPC genes on chromosomes 2 and 8 respectively. Thus, mutations on these genes produce incomplete or nonfunctioning SP-B and SP-C proteins and lead to lung diseases. Both SP-B and SP-C are synthesized in epithelial type II cells as large precursor proteins (proSP-B and proSP-C) and subsequently cleaved by proteolytic enzymes at both amino and carboxyl termini to produce functional mature proteins. proSP-B and proSP-C are first made in the endoplasmic reticulum of epithelial type II cell, they are then translocated through Golgi apparatus to multivesicular bodies for delivery to lamellar bodies. During this transition, proteolytic processing begins to cleave precursor proteins. Once multivescular body reaches the membrane of lamellar body, both membranes fuse together so that processed proteins can be transported into lamellar body, where last steps of maturation for both SP-B and SP-C occur. When lamellar body is ready to be secreted, exocytosis is initiated through influx of Ca2+, and lamellar membrane fuses with plasma membrane to release<unk>  phospholipid contents into the surface of the cell. SP-B and SP-C are responsible to carry out adsorption of the lipid monolayer at the liquid-air interphase to prevent post expiration atelectasis. Used<unk>  phospholipid materials are taken up into epithelial type II cells by pulmonary macrophages. Another important protein that contributes to outcome of<unk>  is ABCA3, a transmembrane phospholipid transporter in lamellar body. ABCA3 has two ATP binding sites in the cytoplasmic domain to power phospholipid transportation through ATP hydrolysis. ABCA3 is synthesized in endoplasmic reticulum and transported through Golgi apparatus to the membrane of lamellar body. Once inserted into the membrane, ABCA3 can help deliver<unk>  lipids into the lumen of lamellar body, and create tightly packed internal environment of<unk>  lipids and<unk>  proteins. Mutations in ABCA3 cause failure in lamellar body synthesis and result in decreased production of<unk> , along with deficiency of SP-B and SP-C.
Surfactant metabolism dysfunction
Congenital pulmonary airway malformation
Hypoplastic right heart syndrome
Humoral immune deficiency
Vocal cord dysfunction
Anomalous pulmonary venous connection
Hypoplastic left heart syndrome
Upper airway resistance syndrome