Part 2 - Chapter 22: COMPLETE Respiratory System - Learning Objectives

State the functions of the respiratory system and name and briefly describe the organs of this system.

Respiration refers to breathing (ventilation) of the lungs.

Principal organs: Nose, pharynx, trachea, bronchi, lungs.

Functions:

Gas exchange: O2 + CO2 exchanged between blood and air.

Communication: speech and other vocalizations.

Olfaction: Sense of smell.

Acid-Base Balance: Influences pH off body fluids by eliminating CO2

Blood pressure regulation: Helping in synthesis of angiotensin II

Blood and lymph flow: Breathing creates pressure gradients between thorax and abdomen to promote flow of lymph and blood.

Platelet production: More than half of platelets are made by megakaryocytes in lungs (not in bone marrow)

Blood filtration: Lungs filter small clots

Expulsion of abdominal contents: Breath-holding assists in urination. defecation, and childbirth

Trace the flow of air from the nose to the pulmonary alveoli.

Air flows from the nose → pharynx → larynx → trachea → main bronchi → bronchial tree (secondary bronchi, bronchioles, terminal bronchioles) → respiratory bronchioles → alveolar ducts → alveolar sacs → pulmonary alveoli.

Explain how pressure gradients account for the flow of air in and out of the lungs and how they are produced.

Pressure gradients drive airflow into and out of the lungs. During inspiration, increased lung volume lowers intrapulmonary pressure, drawing air in. During expiration, decreased lung volume raises intrapulmonary pressure, pushing air out. These changes in volume and pressure are produced by the diaphragm and rib movements, governed by Boyle’s Law.

Identify the sources of resistance to airflow and discuss their relevance to respiration.

Resistance to airflow is primarily influenced by bronchiole diameter (controlled by bronchodilation and bronchoconstriction) and pulmonary compliance (affected by lung stiffness and surface tension). These factors are critical for maintaining efficient respiration and gas exchange.

Define partial pressure and discuss its relationship to a gas mixture such as air.

Partial pressure is the pressure exerted by a single gas in a mixture.

• In a gas mixture like air, the total atmospheric pressure is the sum of the partial pressures of all the gases present (Dalton’s Law). Each gas contributes to the total pressure based on its concentration in the mixture.

Contrast the composition of inspired and alveolar air.

Inspired Air:

• Dry: 0–4% water vapor.

• High Oxygen: 20.9% O₂.

• Low Carbon Dioxide: 0.04% CO₂.

Alveolar Air:

• Humid: 10× more water vapor than inspired air.

• Lower Oxygen: About 65% of inspired air’s O₂.

• Higher Carbon Dioxide: 130× more CO₂ than inspired air.

Why the Difference?

• Air gets humidified, mixes with residual air ( amount of air remaining in lungs after forceful exhalation, which cannot be expelled), and exchanges gases with blood in the lungs.

Discuss how partial pressure affects gas transport by the blood.

1. Gas Exchange:

   • Gases move from high partial pressure to low partial pressure.

     • O₂: Moves from alveoli (high PO₂) to blood (low pCO₂).

     • CO₂: Moves from blood (high pCO₂₂) to alveoli (low pCO₂₂).

2. Oxygen Transport:

   • 98.5% binds to hemoglobin.

   • 1.5% dissolves in plasma.

   • Hemoglobin releases O₂ to tissues with low pCO₂₂.

3. Carbon Dioxide Transport:

   • 90% as bicarbonate ions.

   • 5% bound to proteins.

   • 5% dissolved in plasma.

   • CO₂ released into alveoli where PCO₂ is low.

4. Tissue Needs:

   • Hemoglobin adjusts O₂ unloading based on PO₂ and PCO₂:

     • Low PO₂ in tissues → more O₂ released.

     • High PCO₂ in tissues → more CO₂ picked up.

Describe the mechanisms of transporting O2 and CO2.

Mechanisms of Transporting O₂:

1. Hemoglobin Binding:

   • 98.5% of O₂ binds to hemoglobin in red blood cells.

   • Forms oxyhemoglobin (HbO₂).

2. Dissolved in Plasma:

   • 1.5% of O₂ dissolves directly in plasma.

Mechanisms of Transporting CO₂:

1. Bicarbonate Ions (HCO₃⁻):

   • 90% of CO₂ is converted to bicarbonate ions in the blood.

   • CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻.

2. Bound to Proteins:

   • 5% of CO₂ binds to proteins (e.g., carbaminohemoglobin).

3. Dissolved in Plasma:

   • 5% of CO₂ dissolves directly in plasma.

Exchange in Tissues:

• O₂:

  • Released from hemoglobin in areas with low PO₂ (e.g., active tissues).

• CO₂:

  • Picked up by blood in areas with high PCO₂ (e.g., tissues producing CO₂).

Exchange in Alveoli:

• O₂:

  • Moves from alveoli (high PO₂) to blood (low PO₂).

• CO₂:

  • Moves from blood (high PCO₂) to alveoli (low PCO₂).

Summary:

• O₂ is transported mainly by binding to hemoglobin (98.5%) and partially dissolved in plasma (1.5%).

• CO₂ is transported as bicarbonate ions (90%), bound to proteins (5%), and dissolved in plasma (5%).

• Gas exchange occurs based on partial pressure gradients in tissues and alveoli

Describe the factors that govern gas exchange in the lungs and systemic capillaries.

1. Partial Pressure Gradients:

   • Gases move from high to low partial pressure.

     • Lungs: O₂ → alveoli to blood; CO₂ → blood to alveoli.

     • Tissues: O₂ → blood to tissues; CO₂ → tissues to blood.

2. Solubility of Gases:

   • CO₂ is 20× more soluble than O₂.

3. Membrane Surface Area:

   • Large surface area (70 m²) for gas exchange.

   • Reduced by diseases (e.g., emphysema, tuberculosis).

4. Membrane Thickness:

   • Thin membrane (0.5 μm) allows fast diffusion.

   • Thickening (e.g., pulmonary edema) slows exchange.

5. Ventilation-Perfusion Coupling:

   • Matches airflow and blood flow.

     • Pulmonary vessels: Constrict in poorly ventilated areas.

     • Bronchi: Dilate in well-perfused areas.

Summary:

Gas exchange depends on pressure gradients, solubility, surface area, membrane thickness, and ventilation-perfusion coupling.

Explain how gas exchange is adjusted to the metabolic needs of different tissues.

Hemoglobin Unloads O₂:

• Releases O₂ based on:

  • Low PO₂ in active tissues.

  • High temperature in active tissues.

  • Low pH (from CO₂ buildup) → Bohr Effect.

  • BPG (binds to Hb, promotes O₂ release).

1. CO₂ Transport:

   • Active tissues produce more CO₂:

     • 90% as bicarbonate ions.

     • 5% bound to proteins.

     • 5% dissolved in plasma.

2. Ventilation-Perfusion Coupling:

   • Matches blood flow and airflow:

     • Well-perfused tissues → bronchodilation.

     • Poorly ventilated areas → vasoconstriction.

Gas exchange adjusts to tissue needs via hemoglobin O₂ unloading, CO₂ transport, and ventilation-perfusion coupling.

Describe the chronic obstructive pulmonary diseases and lung cancer.

Chronic Obstructive Pulmonary Diseases (COPD):

1. Chronic Bronchitis:

   • Inflammation, excess mucus, chronic cough.

   • Symptoms: Hypoxemia, cyanosis.

2. Emphysema:

   • Alveolar destruction, air trapping, barrel chest.

   • Symptoms: Severe shortness of breath.

Lung Cancer:

• Causes: Smoking (85–90%), air pollution, irritants.

• Types:

  1. Squamous-Cell Carcinoma: Most common.

  2. Adenocarcinoma: Peripheral lung tissue.

  3. Small-Cell Carcinoma: Most aggressive.

• Symptoms: Coughing blood, chest pain, weight loss.

• Prognosis: Poor (7% survive 5 years).

Summary:

• COPD: Chronic bronchitis and emphysema impair breathing.

• Lung Cancer: Smoking-linked, aggressive, poor survival.