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Some Physical Factors that can Influence Pulmonary Ventilation? list

There are three main factors that can influence the pulmonary ventilation.
Airway Resistance or friction (drag) encountered in the respiratory passageways.
Alveolar Surface Tension
Lung Compliance

airway resistance : def

Airway Resistance or friction (drag) encountered in the respiratory passageways.
The first is airway resistance which is the major non-elastic source of resistance or drag that is encountered in the respiratory passageways.

resistance n gas flow

As resistance in the air passageways increases, gas flow decreases.

resistance in the respiratory tree is determined by

The resistance in the respiratory tree is determined mainly by the diameters of the air-conducting tubes;
the greater the airway diameter the lower the resistance to air flow and vice versa.

normal healthy lung resistant is insignificant: why

In a normal, healthy lung, airway resistance is insignificant because the airway diameters are huge in the proximal part of the conducting zone relative to the low density or viscosity of air.
As the respiratory tree branches, the diameters of the airways get progressively smaller.
However, there are so many branches and tiny bronchioles that if one were to consider the entire cross-sectional diameter of all these passageways, the surface area is huge.

The resistance is greatest

The resistance is greatest in the medium sized bronchi.

terminal bronchioles n air flow

At the terminal bronchioles, air flow ceases and diffusion takes over beginning with the respiratory bronchioles.

first part of respiratory system

Recall that the respiratory bronchioles have alveoli in their walls and
thus represent the first part of the gaseous exchange portion of the respiratory system.

alveolar surface tension: intro

The second factor to consider is alveolar surface tension.
At any gas-liquid boundary, the molecules of the liquid are more strongly attracted to each other than to the gas molecules.

alveolar surface tension: explain

We've already discussed the cohesive properties of water that tend to make the walls of the alveoli stick to each other if it wasn't for surfactant.
Recall that surfactant is synthesized and secreted by the type II alveolar or septal cells which reside in the alveolar walls.
Surfactant is a complex of lipids which coat the inside of the respiratory membrane in the alveolus.
This detergent-like coating decreases resistance in the alveoli and prevents their collapse.

lung compliance: def

The third factor is lung compliance.
As you saw with the sheep pluck demonstration,
healthy lungs are extremely expandable or stretchy.
This ability to distend is called lung compliance.

Lung compliance is determined by

Lung compliance is determined by two factors;
how distensible the lungs are and the alveolar surface tension.

Lung compliance n ventilation

The more distensible the lungs and the lower the surface tension,
the greater the lung compliance and this favors efficient ventilation.

eupnea: def

Normal, quiet respiratory rate and rhythm is called eupnea from the Greek Eu = true or well, and pnoia meaning breath.

eupnea: inhalation %

During quite breathing, inhalation involves the active contraction of the diaphragm which accounts for 75% of quiet breathing, and
contraction of the external intercostals which are responsible for the remaining 25%.

subtypes of epnea based on

There are two subtypes of epnea based on the degree to which these inspiratory muscles contribute to expansion of the thoracic cavity.

subtypes of epnea: list

diaphragmatic breathing
costal breathing

diaphragmatic breathing

Diaphragmatic or deep breathing occurs during minimal activity and involves only the diaphragm.

costal breathing

Costal breathing is typically shallow breathing and involves the external intercostal muscles moving the walls of the thoracic cavity.

eg of costal breathing

For example, pregnant women rely on costal breathing because the growing fetus is restricting movement of the diaphragm.

clinical eg of costal breathing

Sometimes costal breathing is relied upon because of pathological conditions affecting other organ systems such as abdominal tumors or build up of ascites (peritoneal) fluid.

Both types of breathing

Both types of breathing can occur under normal conditions and can be quiet.

In eupnea expiration/exhalation is

In eupnea expiration/exhalation is passive due to the elastic recoil of the lungs—
no muscle contraction is required to exhale during normal breathing.

Exceptions to the "Breathing Rule"

Before we discuss difficulty breathing and pulmonary diseases, let's look at a couple of common situations in which muscular effort is required for inhalation beyond the use of the diaphragm and external intercostals, and when normal passive exhalation is inadequate.

Exceptions to the "Breathing Rule" eg

Normal situations such as exercise and pregnancy

when exercising

We all know that during exercise the respiratory rate increases,
but it is also important to increase the size of the thorax to facilitate taking deeper breaths in order to support cellular demand for oxygen by mainly the skeletal muscles.

accessory inspiratory muscles.

There are several muscles that assist in these respiratory efforts.
They are collectively referred to as accessory inspiratory muscles.

main accessory muscles" list

The main accessory muscles include the sternocleidomastoid muscles, the scalenes and the pectoralis minor.

Forced Expiration: Other muscles fn

Other muscles that attach to the rib cage either directly or indirectly and can increase its volume can also play a role.
Expiration (which is normally passive) is also aided by accessory muscles of expiration

Forced Expiration: muscles: list

the internal intercostals and
the abdominal muscles.

Forced Expiration: muscles: fn

They work to force the rib cage to get smaller.

eg forced expiration

Similarly, pregnant women may need to employ these same muscles to help them breath.

Other muscles that can play a role in forced inhalation

Other muscles that can play a role in forced inhalation include the serratus anterior, pectoralis major & minor, upper trapezius, latissimus dorsi, erector spinae (thoracic), iliocostalis lumborum, quadratus lumborum, serratus posterior superior and inferior, levatores costarum, transversus thoracis, subclavius.

Other muscles of forced exhalation include

Other muscles of forced exhalation include the transversus thoracis muscle as well as the internal intercostals, rectus abdominus, internal and external obliques, and transversus abdominus which function to forcefully decrease the size of the rib cage.

Dyspnea symptom

Sometimes respiration is difficult due to underlying disease conditions.
Dyspnea or difficulty breathing feels like an uncomfortable shortness of breath.

Dyspnea underlysing cause symptom

Dyspnea can be a symptom of many pulmonary or cardiovascular diseases, certain infectious diseases, tumors, immobilization of the diaphragm, pulmonary emboli (clots), pulmonary hypertension, asthma, pneumonia, emphysema, and many more.

Dyspnea: cats" list

In general, pulmonary disorders resulting in dyspnea can be divided into two major categories:
Obstructive disorders
restrictive disorders

Obstructive disorders

Obstructive disorders are those conditions leading to an increased resistance to air flow through the respiratory passageways, and
Resistance to air flow through respiratory passageways.
Exhalation is more difficult than inhalation

illnesses related to obstructive disorders

Asthma, emphysema, cystic fibrosis, bronchitis, COPD

restrictive disorders: symptoms

restrictive disorders in which the volume of the thoracic cage is prevented from fully distending.
Total lung capacity declines

restrictive disorders: related diseases

Arthritis (ribs and vertebrae); ossification of the costal cartilages.
Paralysis or paresis of respiratory muscles
Injury, broken ribs
Muscular dystrophy and Myasthenia gravis
Multiple sclerosis
Polio
Kyphosis
Obesity

In either case,

In either case, breathing in or out is difficult and requires the use of some of the accessory respiratory muscles.

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