(slides 25-33) | Breathing, Pulmonary Ventilation, and Volume Pressure changes

The exchange of gases between the atmosphere, blood, and cells is a combination of how many processes, what are they?

Three

• Pulmonary Ventilation (breathing)

• External Respiration

• Internal Respiration

What breathing process is being described:

• Inhalation

• Exhalation

Pulmonary ventilation (breathing)

What breathing process is being described:

• Exchange of gas between blood, alveoli and external environment

External Respiration

What breathing process is being described:

• Exchange of gas between blood and tissue cells

Internal respiration

The cardiovascular system assists the respiratory system by?

Transporting Gases

What breathing process occurs during pulmonary circulation?

External respiration

What breathing process occurs during systemic circulation?

Internal Respiration

How does pulmonary ventilation relate to the pulmonary and systemic circulations?

• Inhalation brings fresh air into the alveoli.

• Exhalation removes CO₂‑rich air.

What is the first muscle that initiates breathing?

Diaphragm

What are the mechanic of breathing?

Involve several integrated aspects

▪ Specific actions of skeletal muscles of breathing

▪ Dimensional (volume) changes within the thoracic cavity

▪ Pressure changes resulting from volume changes

▪ Pressure gradients

▪ Volumes and pressures associated with breathing

Due to the contraction of skeletal muscles, what happens?

The expansions of the thoracic cavity

• means volume change

When volume in the thoracic cavity changes, what else changes?

The pressure inside thoracic cavity also changes

• creates a pressure gradient

What creates a pressure gradient in the thoracic cavity?

By changing the volume of the thoracic cavity, which changes the pressure

What are the two major steps of pulmonary ventilation?

• Inspiration (inhalation)

• Expiration (exhalation)

What do inspiration and expiration depend on?

Differences in pressure between the atmosphere and the lungs

Air only moves when?

There is a pressure gradient

What happens to the thoracic cavity during inspiration?

It expands

Inspiration and expiration occur due to the?

Expansion and contraction of the thoracic cavity, respectively.

What do the external intercostal muscles and diaphragm do during inspiration?

They contract

What happens to the thoracic cavity during expiration?

It reduces.

What do the external intercostal muscles and diaphragm do during expiration?

They relax

What is the parietal pleura attached to?

Walls of the thoracic cavity

What is the visceral pleura attached to?

The surface of the lungs

What keeps the visceral and parietal pleura together?

Pleural fluid surface tension

What is the pleural cavity?

The thin fluid-filled space between the visceral and parietal pleura

Why do the lungs follow the chest wall during breathing?

Because pleural fluid keeps the pleural layers stuck together, so movement of the parietal pleura pulls the visceral pleura and lungs

What is the one thing we have to remember about the visceral and parietal pleuras?

They are always together

• so they always passively move together

What happens to the pleura when the thoracic cavity moves?

The pleura move with it

• because the parietal pleura is attached to the walls of the thoracic cavity and when the parietal pleura moves, the visceral one does

Pressure changes that drive inhalation and exhalation are governed, in part, by?

Boyle’s law.

What best described Boyle’s law?

The pressure of a gas (in a closed container at const. temp.) is inversely proportional to its volume

• As volume increases, pressure decreases

• As volume decreases, pressure increases

In Boyle’s law, as volume increases, pressure?

Decreases

In Boyle’s law, as volume decreases, pressure?

Increases

What is created by the movement of gas molecules?

Pressure

In a pressure-gradient, air always goes from?

High to low pressure

• diffusion

What muscles are used in quiet breathing?

• Diaphragm

• External Intercostal Muscles

During inspiration, why does air go into lungs?

The volume of the thoracic cavity is increased due to the contraction of skeletal muscles.

• this causes a decrease to the pressure inside the thoracic cavity (to the point its lower than the atmospheric pressure) and air always follow pressure gradient

During expiration, why does air go into lungs?

The volume of the thoracic cavity is reduced due to the relaxation of the skeletal muscles.

• this causes an increase in pressure in the thoracic cavity (to the point its higher than the atmospheric pressure) and air follows pressure gradient

What are the two different ways we breath?

• Forced Breathing

• Quiet Breathing

What muscles are used during forced inspiration?

• Sternocleidomastoid

• Scalenes

• Serratus Posterior superior

• Pectoralis minor

• Erector Spinae

What muscles are used during forced expiration?

• Transverus Thoracis

• Serratus posterior inferior

• Internal intercostal

• External oblique

• Transversus abdominis

What three pressures does pulmonary ventilation depends

on?

• Atmospheric pressure (Patm)

• Intra-alveolar pressure/ Intrapulmonary pressure (Palv)

• Intrapleural pressure (Pip)

What is atmospheric pressure (Patm)?

Pressure of the atmosphere

• 760mmHg

• 0mmHg

What is Intra-alveolar pressure/ Intrapulmonary pressure (Palv)?

Air pressure within Alveoli/lungs

• 760mmHg

• 0mmHg

What is Intrapleural pressure (Pip)?

Pressure within the Pleural Cavity

• 756mmHg

• Area between two serous membranes

• -4mmHg

What is transpulmonary pressure?

The difference between the Intra-alveolar pressure/ Intrapulmonary pressure (Palv) and Intrapleural pressure (Pip)

• 4mmHg

• 760mmHg - 756mmHg

In order for lungs to inflate the outside pressure (intrapleural pressure (Pip))?

Must be lower than inside (intra‑alveolar pressure (Palv))

• So that it does not crush the alveoli inside

At rest, atmospheric pressure and intra‑alveolar pressure are?

The same

• 760mmHg

Why is it important that the intraplueral pressure is lower than the intra-alveolar pressure?

Because that pressure difference is what keeps the lungs expanded instead of collapsing.

Is this during inhalation, exhalation, or at rest:

• Atmospheric pressure = Alveolar pressure

At rest

Where does a pressure-gradient occur?

During inspiration and expiration

Is this during inhalation, exhalation, or at rest:

• Atmospheric pressure > Alveolar pressure

• Diaphragm contracts → moves downward

• The thoracic cavity expands

• The lungs expand because the pleura follow the chest wall

• lung volume increases

Inhalation

Is this during inhalation, exhalation, or at rest:

• Atmospheric pressure < Alveolar pressure

• Diaphragm relaxes → moves upward

• Thoracic cavity gets smaller

• Lungs recoil inward

• lung volume decreases

Exhalation

Lungs are passive during breathing, because?

Of the adhesive nature of the pleural fluid

• which allows the lungs to be pulled outward when the thoracic wall moves during inspiration.

During pulmonary ventilation does us breathing do anything to the lungs?

No, only the thoracic cavity

• lungs only follow passively because of the adhesive nature of the pleural fluid

What is the presence of air or gas in the cavity between the lungs and the chest wall causes the collapse of the lung?

• Air enters chest and lungs collapses

• Damage to either pleura (Visceral or Parietal)

Pneumothorax

• Intrapleural pressure becomes higher than Intra-alveolar pressure/ Intrapulmonary pressure

• Pip: -4mmHg → Pip: 0mmHg

What gives lungs the ability to recoil?

• Elastic fibers in lung tissue

• Alveolar surface tension

What can help re-inflate lungs during Pneumothorax?

Chest tube

• If it is tiny, the body has mechanisms to heal the hole within two week

Inspiratory muscles consume energy to overcome what three factors that hinder air passage and pulmonary ventilation?

• Airway resistance

• Alveolar surface tension

• Lung complianceWhat is airway resistance?

What is airway resistance?

Resistance to airflow in the bronchi and bronchioles

• remember air must move through tubes (bronchi, bronchioles).

• If those tubes narrow, resistance increases.

• Higher resistance = harder to move air = more work for the diaphragm.

• think asthma

If bronchi and bronchiole tubes are narrow, air way resistance?

Increases

• harder to move air through

• more work for diaphragm

What is alveolar surface tension?

The inward‑pulling force created by water molecules lining the alveoli

• Inside every alveolus is a thin film of water.

• Water molecules are strongly attracted to each other (adhesion)

Why is alveolar surface tension a big problem?

The inward‑pulling force created by water molecules lining the alveoli will cause the alveoli to shrink and collapse

• if alveoli collapse, breathing becomes difficult

What solves alveolar surface tension and prevents the collapse of the alveoli?

Surfactant molecules created by Type ll alveolar cells

• It sits between water molecules and reduces their attraction, which lowers surface tension.

• Allows alveoli to stay open

• Makes lungs inflate more

• Work of breathing decrases

What happens to alveoli without surfactant?

High surface tension causes them to collapse

• harder to breath

What happens to alveoli with surfactant?

Surface tension decreases and alveoli stay open

• easier to breath

What is lung compliance?

The ease with which the lungs expand

• expansibility

• due to the elastic fibers within organ

High lung compliance means what?

Lungs expand easily

Low lung compliance means what?

Lungs are stiff and hard to inflate

What conditions reduce lung compliance?

• Pulmonary edema

  • fluid collection in the lungs

• fibrosis

• pneumonia

• TBD

What happens when airway resistance, surface tension, or stiffness increases?

Breathing becomes harder and requires more muscular effort