Pulmonary Surfactant Introduction Pulmonary surfactant is a surface-active organic complex of phospholipids and proteins. It reduces surface tension, prevents alveoli collapse after expiration, and makes respiration easy and smooth. Surfactant is crucial for life as it prevent atelectasis. About’ totalphysiology.com.’ This article is part of my mission to provide trustworthy, recent health information to support the general public, patients, and professionals globally. Here, you will find human Physiology and health-related topics. This article is intended for all learners and medical care providers. This activity aims for learners to better apply the latest scientific knowledge. Upon completing the article, you will have increased knowledge regar...
Pulmonary Surfactant
Introduction
Pulmonary surfactant is a surface-active organic complex of phospholipids and proteins. It reduces surface tension, prevents alveoli collapse after expiration, and makes respiration easy and smooth. Surfactant is crucial for life as it prevent atelectasis.
About’ totalphysiology.com.’
This article is part of my mission to
provide trustworthy, recent health information to support the general public,
patients, and professionals globally.
Here, you will find human Physiology and
health-related topics.
This article is intended
for all learners and medical care providers.
This
activity aims for learners to better apply the latest scientific knowledge.
Upon completing the article, you
will have increased knowledge regarding the subject and use it with great
confidence.
Keywords
Dipalmitoyl phosphotidyl choline (DPPC)| Surfactant proteins are SP-A, SP-B, SP-C, and SP-D|Apolipoprotein| Pneumocyte II|Club cells|Survanta | Pumactant (ALEF)| ARDS|IRDS|intractable respiratory failure|progressive interstitial pneumonitis
Composition of Surfactant
Surfactant consists of
1.About 40% DPPC (dipalmitoyl
phosphotidyl choline)
2. About 40% of other
phospholipids
3.10% cholesterol
4. The remaining 10% is
'surfactant protein.' Half of this 10% is a plasma protein; Apolipoprotein forms the rest.
5. Traces of other substances.
The surfactant proteins are SP-A,
SP-B, SP-C, and SP-D. Each performs specific functions and works synergistically
to keep the interface rich in surfactants during inspiration and contractions.
Surfactant is secreted from
1. Pneumocyte II-secrete a significant portion of surfactant, and
2. Club cells secrete a small
amount of surfactant.
During the 20th week of gestation,
alveolar sacs develop, and surfactant appears in their cytoplasm. As the infant
grows, surfactant formation also increases. As the infant develops, so does
the surfactant formation.
The average concentration of surfactant
A full-term baby has an alveoli
storage pool of surfactant of about 100 mg/kg of body weight, while preterm
infants have only 4 to 5 mg/kg.
Causes of surfactant deficiency in newborn
1. Maternal factors- maternal diabetes
2. Fetal factors-mutation in genes
forming dysfunctional surfactant.
3. Premature birth.
4. Deficiency may occur at a later
age due to certain pulmonary infections, pollution, and cigarette smoking.
Half-life:
The half-life of Surfactant is five to ten minutes.
Metabolism:
Surfactant is broken down by pulmonary macrophages and reabsorbed into the
lamellar structure of pneumocytes II.
About 90% of DPPC is absorbed from
the alveolar space and transported into Pneumocytes II. This transportation is
due to 'Clathrin-dependent endocytosis.'
Pulmonary (alveoli) macrophages
digest the remaining 10 % DPPC.
Functions:
1. Reduces surface tension in alveoli.2. Increases pulmonary compliance
3. Prevents
collapse of the alveoli
4. Prevents
the development of atelectasis at the end of expiration.
5. It
helps all alveoli to expand at the same rate.
6. Opens
collapsed alveoli.
7. It regulates inflammatory responses.
8. Regulates
adaptive immunity.
9. Provides
innate immunity.
10. It reduces fluid accumulation in
the alveolar spaces and keeps the airway dry.
Artificial Surfactants
Artificial surfactants, such as
Survanta and Pumactant (ALEF), are available in the market. WHO included these
drugs on the list of essential medicines.
Artificial Surfactants are given
to infants within one to two hours after birth who present with respiratory
distress syndrome. For infants born with respiratory distress syndrome,
synthetic surfactants are provided within one to two hours after birth
Diseases due to lack of Surfactant:
Reduced Surfactant causes
IRDS (Infant respiratory distress
syndrome) affects infants, and ARDS (Adult respiratory distress syndrome)
affects adults.
Causes
intractable respiratory failure.
Causes progressive interstitial
pneumonitis.
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Internal links
https://blog.totalphysiology.com/2025/02/tidal-volume-explained-respiratory.html
https://blog.totalphysiology.com/2025/01/vital-capacity-respiratory-system.html
https://blog.totalphysiology.com/2021/07/pleura.html
External links
https://en.wikipedia.org
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