7 The Respiratory System 2.pptx

Introduction to the Respiratory System

• The focus of the study is on the Respiratory System

• Important concepts include:

  • Breathing

  • Pulmonary ventilation

  • External & internal respiration

  • Control of breathing

  • Relevant laws: Boyle’s, Dalton’s, Henry’s

  • Haldane effect

  • Gas transport & exchange (O2 vs CO2)

  • Hemoglobin (Hb) association & dissociation

Importance of Proper Note-taking Practices

• Recordings should be treated like a lecture; complete viewing in real-time is recommended.

• Google Slides/Docs are set to "View Only"; make a copy to take notes.

• Avoid trying to capture every detail; focus on understanding major concepts.

Pressure Basics in the Respiratory System

Types of Pressure

1. Atmospheric Pressure (Patm):

   • The pressure of the surrounding atmosphere.

   • Constant at 1 atm = 760 mm Hg at sea level.

2. Intra-alveolar Pressure (Palv):

   • Pressure within the alveoli of the lungs.

3. Intrapleural Pressure (Pip):

   • Pressure in the pleural cavity, which is always negative compared to Patm and Palv to prevent alveoli collapse.

4. Transpulmonary Pressure:

   • Difference between Pip and Palv, determining lung size.

Principles of Breathing

• Breathing requires a pressure gradient: air moves from high pressure to low pressure.

• Inspiration: Air entering lungs requires a lower Palv than Patm.

• Expiration: Air exiting lungs requires a higher Palv than Patm.

Boyle’s Law and Its Application

Boyle’s Law Principles

• Gas volume varies inversely with pressure at a constant temperature.

• When breathing:

  • Air moves from high to low-pressure areas.

  • Altering thoracic cavity size using muscles affects Palv.

Influence of Atmospheric and Alveolar Pressures

• Volume changes in thoracic cavity create pressure changes within the lungs.

• Altering thoracic volume causes:

  • Inspiration: Palv < Patm (pressure gradient created)

  • Expiration: Palv > Patm (pressure released)

Factors Affecting Ventilation

Physical Factors

• Diaphragm and Accessory Muscles: Contraction/relaxation drive ventilation.

• Airway Resistance: Depend on the diameter of the airways.

  • Factors include:

    • Bronchodilation (increased diameter) vs. bronchoconstriction (decreased diameter)

• Surface Tension: Affects lung expansion and is reduced by pulmonary surfactant.

• Thoracic Wall Compliance: Reflects ability to stretch under pressure: decreased compliance makes breathing harder.

• Elastic Recoil: Returns lungs to resting size after inhaling.

Pulmonary Ventilation Mechanics

• Processes: Pulmonary ventilation consists of one cycle of inspiration and expiration.

1. Inspiration:

   • Requires contraction of diaphragm and external intercostals to enlarge thoracic cavity.

2. Expiration:

   • Relaxation of diaphragm and external intercostals with lung recoil reduces thoracic cavity size.

Quiet and Forced Breathing

Quiet Breathing (Eupnea)

• When Palv = Patm, airflow ceases.

• During quiet breathing, pressure changes regulate airflow without cognitive effort.

Forced Breathing (Hyperpnea)

• Active breathing requiring additional muscle engagement, such as during exercise.

• Forced Expiration: Involves diaphragm and internal intercostals to expel more air.

• Forced Inspiration: Involves several muscles to significantly expand thoracic cavity.

Ventilation Control Centers

• Breathing is controlled by various inputs like:

  • Chemoreceptors: Monitor blood gases.

  • Hypothalamus: Responds to emotional states.

  • Stretch Receptors: Prevent lung over-inflation.

• Brain Regions: Medulla and pons coordinate a rhythmic breathing pattern.

Gas Exchange Principles

External vs. Internal Respiration

• External Respiration: Gas exchange occurs in pulmonary capillaries and alveoli (O2 in, CO2 out).

• Internal Respiration: Gas exchange occurs in systemic capillaries and body cells (O2 out, CO2 in).

Partial Pressure of Gases

• Defined as the pressure exerted by gas in a mixture.

• Influenced by the gas's concentration and total mixture pressure.

• Gases move down their own partial pressure gradients.

• Dalton’s Law: Each gas in a mixture moves according to its pressure gradient.

Hemoglobin and Gas Transport

O2 Transport

1. In plasma: Only 0.3 ml/100 ml dissolved (1.5%).

2. In whole blood: 20 ml/100 ml transported by hemoglobin.

3. Oxygen affinity affects binding and release:

   • Oxygen-Hemoglobin Dissociation Curve: Describes how O2 saturation varies with pO2.

   • Fetus has fetal hemoglobin with higher O2 affinity for lower pO2 environments.

Factors Affecting O2-Hb Dissociation

• Bohr Effect: Lower pH increases O2 dissociation.

• Temperature: Increased temperature promotes dissociation.

Carbon Dioxide Transport

Mechanisms of CO2 Transport

1. Dissolved CO2: 10% in plasma.

2. Bicarbonate Buffering System: 70%, crucial in maintaining pH balance.

3. Carbaminohemoglobin: 20% binds CO2 to hemoglobin.

Haldane Effect

• CO2 affinity to hemoglobin is influenced by O2 levels:

  • High pO2 leads to lower CO2 binding.

  • Low pO2 leads to higher CO2 loading into blood.