Respiratory System: Types of Pressure

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Questions and Answers

What is the purpose of surfactant secreted in alveolar epithelium?

To reduce the expansibility of lungs

To prevent the collapsing tendency produced by surface tension (correct)

To increase surface tension on the alveolar membrane

To stimulate the release of respiratory muscles

What happens to lung compliance when lungs are removed from the thorax?

It decreases

It remains the same

It becomes zero

It doubles (correct)

What is the result of deformities of the thorax on lung compliance?

Compliance increases

Compliance remains the same

Compliance becomes zero

Compliance decreases (correct)

What is the primary function of the respiratory muscles during quiet breathing?

To cause inspiration Signup and view all the answers

What is the effect of emphysema on lung compliance?

Compliance increases Signup and view all the answers

What is the result of old age on lung compliance?

Compliance increases Signup and view all the answers

What is the definition of compliance in the context of lungs?

The change in volume per unit change in respiratory pressure Signup and view all the answers

During quiet breathing, what is the primary process that causes expiration?

Passive elastic recoil of the lungs and chest cage Signup and view all the answers

Which pressure is always negative in the respiratory system?

Intrapleural pressure Signup and view all the answers

What is the main function of intrapleural pressure?

To prevent the lungs from collapsing Signup and view all the answers

What happens to intra-alveolar pressure during inspiration?

It becomes more negative. Signup and view all the answers

Which of the following is NOT a factor that contributes to the collapsing tendency of the lungs?

Negative intrapleural pressure Signup and view all the answers

How is transpulmonary pressure calculated?

Intrapleural pressure + intra-alveolar pressure Signup and view all the answers

What is the role of intra-alveolar pressure in gas exchange?

It creates a pressure gradient that facilitates gas exchange. Signup and view all the answers

What is the primary reason why the lungs are always inflated?

The negative intrapleural pressure. Signup and view all the answers

Which of these statements accurately describes the relationship between intrapleural pressure and intra-alveolar pressure throughout the respiratory cycle?

Intra-alveolar pressure is always higher than intrapleural pressure. Signup and view all the answers

What is airway resistance work primarily related to?

Passage of air through the respiratory tract Signup and view all the answers

What does compliance work specifically address in the context of breathing?

Elastic resistance of lungs and thorax Signup and view all the answers

Physiological dead space includes which of the following?

Non-functioning alveoli and inadequate blood flow areas Signup and view all the answers

What represents the volume of normal dead space in the respiratory system?

150 mL Signup and view all the answers

What effect do respiratory disorders primarily have on dead space?

Increase the volume of dead space Signup and view all the answers

Which method is used to measure dead space in the respiratory system?

Single breath nitrogen washout method Signup and view all the answers

In normal conditions, how does physiological dead space compare to anatomical dead space?

They are typically equal Signup and view all the answers

Which type of resistance is considered non-elastic in the work of breathing?

Viscous resistance Signup and view all the answers

What initiates the cough reflex?

Irritation of the respiratory tract Signup and view all the answers

Which mechanism effectively prevents respiratory issues during swallowing?

Temporary arrest of breathing Signup and view all the answers

What is the primary cause of the sneezing reflex?

Irritation of the nasal mucous membrane Signup and view all the answers

During a cough, what happens to the intrapleural pressure?

It increases above 100 mm Hg Signup and view all the answers

What term describes the temporary halt in respiration while swallowing?

Swallowing apnea Signup and view all the answers

What occurs at the end of a cough reflex?

Sudden opening of the glottis Signup and view all the answers

Study Notes

Pressures in the Thoracic Cavity and Lungs

Two types of pressures are exerted in the thoracic cavity and lungs during respiration: intrapleural pressure and intra-alveolar pressure.
Intrapleural pressure is the pressure existing in the pleural cavity, between the visceral and parietal layers of pleura, and is always negative.
Intrapleural pressure prevents the collapsing tendency of lungs, causes dilation of vena cava and larger veins in the thorax, and keeps the lungs inflated.
Intra-alveolar pressure is the pressure existing in the alveoli of the lungs and becomes negative during inspiration and positive during expiration.
Intra-alveolar pressure causes the flow of air in and out of alveoli and helps in the exchange of gases between alveolar air and blood.

Transpulmonary Pressure

Transpulmonary pressure is the difference between intra-alveolar pressure and intrapleural pressure.

Factors Responsible for Collapsing Tendency of Lungs

Two factors are responsible for the collapsing tendency of lungs: elastic property of lung tissues and surface tension exerted on the surface of the alveolar membrane by the fluid secreted from alveolar epithelium.

Factors that Save Lungs from Collapsing

Two factors save the lungs from collapsing: intrapleural pressure, which is always negative, and surfactant secreted in alveolar epithelium, which decreases surface tension on the alveolar membrane.

Compliance

Compliance is the ability of the lungs and thorax to expand and is defined as the change in volume per unit change in respiratory pressure.
Compliance is a measure of stiffness of lungs, and stiffer the lungs, less is the compliance.
Compliance decreases in pathological conditions such as deformities of thorax, paralysis of respiratory muscles, pleural effusion, fibrosis, and abnormal thorax.
Compliance increases in physiological and pathological conditions such as old age, emphysema, and deformities of thorax.

Work of Breathing

Work of breathing is the energy obtained during inspiration to overcome three types of resistance: airway resistance, elastic resistance of lungs and thorax, and non-elastic viscous resistance.
Airway resistance work is the work done to overcome airway resistance, which increases during bronchiolar constriction.
Compliance work is the energy required to expand lungs and thorax against the elastic force.
Tissue resistance work is the energy required to overcome the viscosity of lung tissues and tissues of thoracic cage.

Dead Space

Dead space is the part of the respiratory tract where gaseous exchange does not take place, and the air present in the dead space is called dead space air.
There are two types of dead space: anatomical dead space and physiological dead space.
Physiological dead space includes anatomical dead space plus two additional volumes: non-functioning alveoli and alveoli that do not receive adequate blood flow.
Under normal conditions, physiological dead space is equal to anatomical dead space, and volume of normal dead space is 150 mL.
Dead space increases in respiratory disorders that affect pulmonary blood flow or alveoli.

Respiratory Protective Reflexes

Respiratory protective reflexes are the reflexes that protect the lungs and air passage from foreign particles.
The respiratory protective reflexes are cough reflex, sneezing reflex, and swallowing reflex (deglutition).
Cough reflex is a protective reflex that occurs because of irritation of the respiratory tract and some other areas, and it begins with deep inspiration followed by forced expiration with closed glottis.
Sneezing reflex is a protective reflex caused by irritation of nasal mucous membrane, and it starts with deep inspiration, followed by forceful expiratory effort with opened glottis.
Swallowing reflex (deglutition) is a respiratory protective reflex that prevents entrance of food particles into the air passage during swallowing, and it involves temporary arrest of respiration called apnea.

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Description

Learn about the two types of pressures exerted in the thoracic cavity and lungs during respiration, including intrapleural and intra-alveolar pressure.