Human Physiology: Respiratory Mechanics

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Questions and Answers

What happens to the air pressure in the lungs during inspiration when the thoracic cavity expands?

Air pressure in the lungs decreases. (correct)

Air pressure in the lungs fluctuates drastically.

Air pressure in the lungs increases.

Air pressure in the lungs remains constant.

Which muscle is primarily responsible for increasing the vertical dimension of the thoracic cavity during inspiration?

Sternocleidomastoid

Diaphragm (correct)

Rectus abdominis

Internal intercostal muscles

According to Boyle's Law, what occurs when the volume of the thoracic cavity decreases?

The volume of the lungs increases.

The pressure within the lungs decreases.

The pressure within the lungs increases. (correct)

The volume of gases in the thoracic cavity remains constant.

What is the primary effect of the contraction of the external intercostal muscles during inspiration?

Elevates the ribs and sternum. Signup and view all the answers

What directly causes air to enter the lungs during inspiration?

Decrease in alveolar pressure. Signup and view all the answers

During expiration, which change in the thoracic cavity occurs?

The thoracic cavity decreases in volume. Signup and view all the answers

Which statement regarding gas movement is true?

Gas moves from higher to lower pressure. Signup and view all the answers

What physiological role does the pleural seal play during breathing?

It prevents the lungs from collapsing. Signup and view all the answers

What is the definition of vital capacity (VC)?

The maximum amount of gas that can be expired after a maximum inspiration. Signup and view all the answers

Which lung volume represents the volume of air that cannot be directly measured?

Residual volume Signup and view all the answers

What formula represents the total lung capacity (TLC)?

TLC = VC + Residual volume Signup and view all the answers

Which lung capacity indicates the amount of gas remaining in the lungs after normal tidal expiration?

Functional residual capacity Signup and view all the answers

How is inspiratory capacity defined?

The maximum amount of gas that can be inspired after a normal tidal expiration. Signup and view all the answers

What happens to lung pressure when lung volume increases?

Lung pressure decreases Signup and view all the answers

Which muscles relax during normal expiration?

External intercostal and diaphragm Signup and view all the answers

What is the primary mechanism that leads to air moving out of the lungs?

Decreased lung pressure Signup and view all the answers

In forced breathing, which muscles assist in expiration?

Internal intercostal muscles Signup and view all the answers

Which condition is NOT achieved when breathing through the mouth?

Increasing air pressure gradient Signup and view all the answers

What is the role of mucus in the upper airways?

Traps inhaled particles and organisms Signup and view all the answers

What happens to thoracic cavity volume during expiration?

It decreases Signup and view all the answers

What is the primary function of cilia in the respiratory system?

Transport mucus toward the pharynx Signup and view all the answers

What is the primary role of pulmonary surfactant in the lungs?

Reduce surface tension and decrease the work of breathing Signup and view all the answers

Which factor affects the rate of diffusion in the lungs?

Membrane thickness Signup and view all the answers

What is the role of ventilation in the ventilation-perfusion relationship?

To facilitate gas exchange in the alveoli Signup and view all the answers

What happens to the surface area available for gas exchange in the lungs during emphysema?

It decreases due to loss of alveolar structure Signup and view all the answers

What happens to blood flow when there is a decrease in ventilation in specific alveoli?

Blood flow is diverted to better-ventilated alveoli Signup and view all the answers

Which of the following mechanisms is involved in regulating respiration through changes in arterial PO2?

Action of peripheral chemoreceptors Signup and view all the answers

How is oxygen primarily transported in the blood?

Mainly bound to hemoglobin within red blood cells Signup and view all the answers

Phrenic nerve paralysis primarily affects which aspect of respiration?

Diaphragm functionality Signup and view all the answers

What occurs when CO2 diffuses from the tissues into the blood?

23% combines with deoxyhemoglobin to form carbamino compounds Signup and view all the answers

What is the role of the diffusion barrier in the alveoli?

Impair gas exchange when thickened Signup and view all the answers

What is the average tidal volume for a healthy adult?

500 ml Signup and view all the answers

Which of the following statements regarding the solubility of oxygen is true?

Only 1.5% of O2 dissolves in plasma Signup and view all the answers

Which process occurs when carbon dioxide levels rise significantly in the blood?

Reflex stimulation of ventilation Signup and view all the answers

What is a consequence of pulmonary edema on gas exchange?

Increased thickness of the diffusion barrier Signup and view all the answers

The constriction of pulmonary vessels in response to low oxygen levels primarily diverts blood to which regions?

Better-ventilated alveoli Signup and view all the answers

Which of the following describes the role of the enzyme present in pulmonary vessels during hypoxia?

Facilitates blood flow regulation Signup and view all the answers

What is the impact on airflow if the resistance in the airways increases?

Pressure gradient must increase to maintain the airflow rate. Signup and view all the answers

What role does surfactant play in the lungs?

It reduces surface tension and prevents alveoli from collapsing. Signup and view all the answers

During an asthma attack, what primarily causes the increased resistance to airflow?

Constriction of airways due to smooth muscle hypertrophy. Signup and view all the answers

What is the primary function of gas exchange in the respiratory system?

To ensure a constant supply of oxygen and remove carbon dioxide. Signup and view all the answers

Why is blood pressure in the lungs comparatively low?

The net hydraulic pressure is low due to filtered fluid removal. Signup and view all the answers

How does surfactant affect small alveoli compared to larger ones?

It is more effective in small alveoli than large ones. Signup and view all the answers

What happens to the work of breathing if surface tension in the alveoli is high?

It increases due to the tendency of alveoli to collapse. Signup and view all the answers

What is the relationship described by Ohm's law as it applies to respiratory physiology?

Airflow is equal to pressure gradient divided by resistance. Signup and view all the answers

Study Notes

Physiology of the Respiratory System

The respiratory system's main function is gas exchange—getting oxygen into the body and removing carbon dioxide.
Breathing involves the exchange of gases between the atmosphere and blood.
Homeostatic regulation of body pH is a vital function of the respiratory system.
Protection from inhaled pathogens and irritating substances is another protective function of the respiratory system.
Vocalization is a function of the respiratory system.
Cellular respiration is the intracellular process that uses oxygen to produce energy (ATP).
External respiration is the interchange of gases between the environment and the body's cells.

Learning Outlines

The respiratory system's importance is described.
The gas laws are stated.
The ventilation process is explained.
Gas exchange in the lungs and tissues is described.
Gas transport in the blood is described.
The factors that regulate ventilation are identified.
Pulmonary function tests are described.
A proper correlation between the respiratory system and daily life is established.
The magnificence of God's creation is acknowledged.

Breathing—Why Bother?

Exchange of gases between the atmosphere and blood is essential.
Homeostatic regulation of the body's pH is maintained.
Protection from inhaled pathogens and harmful substances is provided.
Vocalization is enabled through the respiratory system.

Two Types of Breathing

Cellular respiration: intracellular process where oxygen and organic molecules convert to carbon dioxide, water, and ATP
External respiration: interchange of gases between the environment and body's cells

External and Internal Respiration

External respiration occurs between inhaled air and the bloodstream, while internal respiration occurs between the blood and body cells.
Oxygen in the air diffuses into the blood.
Carbon dioxide in the blood diffuses out into alveoli.
Oxygen from the blood diffuses into the tissues.
Carbon dioxide from the tissues diffuses into the blood.

The Lungs and Breathing

The pleural space is the area between the lung surface and the thoracic wall.
This area usually contains pleural fluid for lubrication.
The pleural fluid creates a seal-like effect, holding the lungs against the thoracic wall.
The force of the seal ensures that lung expansion and contraction follow thoracic activity.

Mechanics of Breathing

Air movement in and out of the lungs is based on pressure differentials.
Inspiration occurs when pressure within alveoli is lower than atmospheric pressure.
Expiration occurs when alveoli pressure exceeds atmospheric pressure.

Muscle of Breathing

The diaphragm, external intercostals, sternomastoids, and scalenes are inspiratory muscles.
The internal intercostals and abdominals are expiratory muscles.

Mechanics of Breathing—Focus on Diaphragm

At rest, the diaphragm is relaxed.
When the diaphragm contracts, thoracic volume increases.
When the diaphragm relaxes, thoracic volume decreases.

Mechanics of Breathing—Focus on Intercostals

The intercostal muscles move the ribs.
Inspiration—the "pump handle" action increases the anterior-posterior dimension, and the "bucket handle" action increases the lateral dimension of the rib cage.
Expiration—the "pump handle" action decreases the anterior-posterior rib cage dimension, and the "bucket handle" action decreases the lateral rib cage dimension.

Volume and Pressure

Muscle contraction and relaxation change thoracic cavity volume, affecting lung volume and pressure.
Changes in lung volume cause pressure changes, enabling breathing.

Boyle's Law

Boyle's law states that gas volume and pressure are inversely proportional (at constant temperature).
An increasing volume leads to a decrease in pressure.
A decreasing volume leads to an increase in pressure.

Gases Movement

Gases move from areas of high pressure to low pressure.
Solubility of a gas in a liquid is affected by its pressure.

Inspiration

During inspiration, inspiratory muscles contract, increasing thoracic cavity volume and causing lung volume increase.
Lung expansion follows thoracic cavity expansion, allowing air entry.
The diaphragm and external intercostal muscles are critical during inspiration.

Expiration

Expiration involves relaxation of inspiratory muscles, decreasing thoracic cavity volume and reducing lung volume.
Elastic recoil in lung tissue and the abdominal muscles support expiration.

Process of Expiration

During expiration, the diaphragm relaxes and the chest wall recoils—reducing the volume within the thoracic cavity.
Lung volume decrease causes an increase in pressure inside the lungs, expelling air.
Inspiration muscles are relaxed, which allows expiration to occur.

Determinants of Airway Resistance

Upper airways are more involved than simple passageways for warmed and humidified air.
Foreign materials are filtered.
Cilia remove mucus from the airways.
The secretion of watery mucus is functional for trapping harmful substances.
Mucus removal is crucial.

Blood Flow Rate and Pressure in Lungs

Blood flow rate in lungs is high—compared to other tissues.
Pressure in the lung is low.
The low pressure is due to low hydraulic pressure.
Lymphatic system removes excess fluid.

Ohm's Law

Ohm's law illustrates the relationship among airflow, pressure gradient, and resistance in lung function.
Flow is the quotient of the pressure gradient and resistance.

Clinical Relevant: Asthma

During asthma exacerbations, airways narrow due to smooth muscle constriction and inflammation.
This increased resistance requires more effort from the patient to move air into the alveoli.
Increased resistance leads to turbulent airflow, characteristic of asthma's wheezing.

Gas Exchange

Gas exchange is the process of moving oxygen between the bloodstream and lungs.
Gas movement is vital for maintaining a constant oxygen supply to the tissues and removing carbon dioxide.

What is It?

The process of gas exchange involves oxygen uptake and carbon dioxide removal through the bloodstream and lungs.

Gas Exchange in Alveoli and Cells

Gas exchange in the alveoli and cells is influenced by partial pressure differences.

Oxygen Transport in the Blood

Oxygen circulates in the blood (mostly within red blood cells) and dissolves in plasma.
Hemoglobin (Hb) is a vital component for carrying oxygen.

Carbon Dioxide Transport

Carbon dioxide moves from tissues to the lungs through the bloodstream.
Various processes enable carbon dioxide to be transported from tissues to lungs, such as dissolving in plasma, associating with hemoglobin and converting to bicarbonate (HCO3).

Ventilation-Perfusion Matching

Ventilation-perfusion matching is crucial for optimal gas exchange.
A match between ventilation and perfusion ensures an adequate supply and removal of oxygen and carbon dioxide.
Ventilation and perfusion ratios aid in the identification of conditions causing ventilation and perfusion differences.

Local Control of Ventilation and Perfusion

Ventilation and perfusion are controlled and coordinated locally to maintain adequate gas exchange.
Partial pressure of gases (oxygen and carbon dioxide) in tissues regulates ventilation and perfusion.

Regulation of Respiration

Breathing control centers, located in the medulla and pons of the brain.
Nerve signals from chemical receptors and stretch receptors in the body tissues and aorta guide respiration.
Respiration occurs in response to oxygen and carbon dioxide levels in the body.
Control centers are responsible for coordination of respiratory activity.

Control of Breathing

The medulla oblongata is the respiratory control center.
The pons is involved in the smooth transition between inspiration and expiration.
CO₂ levels in the cerebrospinal fluid (CSF) signal the brain for adjustments to breathing rate.
Breathing rate is also adjusted to changes in oxygen (O₂) levels in the body's cells.
Other factors, including emotions and psychological conditions, can impact breathing.

Phrenic Nerve Paralysis

Phrenic nerve paralysis affects breathing by affecting the diaphragm's function.
This condition is due to damage to the phrenic nerve.
Common causes of phrenic nerve paralysis include injuries and surgical complications.

Pulmonary Function Test

Spirometry is used to measure air volume during breathing cycles.
Lung volumes (tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume) are described and defined.
Lung capacities (vital capacity and total lung capacity) are identified and their definitions are provided.

Variations in Lung Volume

Variations in lung volumes and capacities are described.

Lung Capacities

Lung capacities represent the sum of multiple lung volumes.
Vital capacity is the maximum volume of air that can be breathed in and out during a respiratory cycle.
Total lung capacity represents the overall volume of air within the respiratory system.
Lung capacities are involved in assessing lung function.

Swimming & Lung Capacity

Swimming increases lung capacity and delivers more oxygen to the body.

End of Lecture

The lecture concludes with a thank-you acknowledgment.

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Description

Test your knowledge on the mechanics of breathing in human physiology. This quiz covers concepts such as lung pressure changes, muscle functions during inspiration and expiration, and the role of Boyle's Law. Challenge yourself with questions related to the respiratory system and gas movement.