RESPIRATION COMPLETE NURSING NOTES | EXAM-READY SUMMARY | A+
RATED | 2026/2027 | UNIVERSITY/COLLEGE
1. INTRODUCTION TO RESPIRATION
Definition
Respiration is the process by which the body obtains oxygen (O₂), removes carbon dioxide
(CO₂), and uses oxygen to release energy from nutrients.
Two Main Meanings
Type Meaning
External respiration Exchange of O₂ and CO₂ between alveoli and blood
Internal respiration Exchange of O₂ and CO₂ between blood and body tissues
Cellular respiration Cells use oxygen to produce energy (ATP)
Simple Flowchart
Air → Nose/Mouth → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
→ Blood
O₂: Alveoli → Blood → Tissues
CO₂: Tissues → Blood → Alveoli → Exhaled
2. RESPIRATORY SYSTEM
Major Structures
Structure Main Function
Nose/nasal cavity Filters, warms and moistens air
Pharynx Passage for air
Larynx Maintains airway and produces voice
Trachea Conducts air to bronchi
Bronchi Carry air into each lung
Bronchioles Smaller air passages
,Structure Main Function
Alveoli Site of gas exchange
Lungs Main organs of respiration
Diaphragm Major muscle of breathing
Intercostal muscles Assist chest expansion and contraction
Mnemonic: “N P L T B B A L D”
Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli → Lungs →
Diaphragm
3. MECHANICS OF BREATHING
Inspiration
During inspiration:
• Diaphragm contracts and moves downward.
• External intercostal muscles contract.
• Thoracic cavity volume increases.
• Pressure inside the lungs decreases.
• Air moves into the lungs.
Flowchart
Diaphragm contracts → Thoracic volume ↑ → Lung pressure ↓ → Air enters
Expiration
During normal expiration:
• Diaphragm relaxes and moves upward.
• Thoracic volume decreases.
• Lung pressure increases.
• Air moves out.
Flowchart
Diaphragm relaxes → Thoracic volume ↓ → Lung pressure ↑ → Air leaves
, 4. GAS EXCHANGE
Gas exchange occurs mainly in the alveoli.
Oxygen
• Oxygen concentration is higher in alveolar air.
• O₂ diffuses across the alveolar-capillary membrane.
• O₂ enters the blood.
• Hemoglobin carries most oxygen.
Carbon Dioxide
• CO₂ concentration is higher in venous blood.
• CO₂ diffuses into the alveoli.
• It is removed during expiration.
Important Concept
Gas exchange occurs by diffusion, moving gases from an area of higher partial pressure to an
area of lower partial pressure.
5. SURFACTANT
Surfactant is a substance produced by type II alveolar cells.
Functions
• Reduces surface tension inside alveoli.
• Prevents alveolar collapse.
• Makes lung expansion easier.
• Improves respiratory efficiency.
Exam Tip
Surfactant = prevents alveolar collapse.
6. CONTROL OF RESPIRATION
RATED | 2026/2027 | UNIVERSITY/COLLEGE
1. INTRODUCTION TO RESPIRATION
Definition
Respiration is the process by which the body obtains oxygen (O₂), removes carbon dioxide
(CO₂), and uses oxygen to release energy from nutrients.
Two Main Meanings
Type Meaning
External respiration Exchange of O₂ and CO₂ between alveoli and blood
Internal respiration Exchange of O₂ and CO₂ between blood and body tissues
Cellular respiration Cells use oxygen to produce energy (ATP)
Simple Flowchart
Air → Nose/Mouth → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
→ Blood
O₂: Alveoli → Blood → Tissues
CO₂: Tissues → Blood → Alveoli → Exhaled
2. RESPIRATORY SYSTEM
Major Structures
Structure Main Function
Nose/nasal cavity Filters, warms and moistens air
Pharynx Passage for air
Larynx Maintains airway and produces voice
Trachea Conducts air to bronchi
Bronchi Carry air into each lung
Bronchioles Smaller air passages
,Structure Main Function
Alveoli Site of gas exchange
Lungs Main organs of respiration
Diaphragm Major muscle of breathing
Intercostal muscles Assist chest expansion and contraction
Mnemonic: “N P L T B B A L D”
Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli → Lungs →
Diaphragm
3. MECHANICS OF BREATHING
Inspiration
During inspiration:
• Diaphragm contracts and moves downward.
• External intercostal muscles contract.
• Thoracic cavity volume increases.
• Pressure inside the lungs decreases.
• Air moves into the lungs.
Flowchart
Diaphragm contracts → Thoracic volume ↑ → Lung pressure ↓ → Air enters
Expiration
During normal expiration:
• Diaphragm relaxes and moves upward.
• Thoracic volume decreases.
• Lung pressure increases.
• Air moves out.
Flowchart
Diaphragm relaxes → Thoracic volume ↓ → Lung pressure ↑ → Air leaves
, 4. GAS EXCHANGE
Gas exchange occurs mainly in the alveoli.
Oxygen
• Oxygen concentration is higher in alveolar air.
• O₂ diffuses across the alveolar-capillary membrane.
• O₂ enters the blood.
• Hemoglobin carries most oxygen.
Carbon Dioxide
• CO₂ concentration is higher in venous blood.
• CO₂ diffuses into the alveoli.
• It is removed during expiration.
Important Concept
Gas exchange occurs by diffusion, moving gases from an area of higher partial pressure to an
area of lower partial pressure.
5. SURFACTANT
Surfactant is a substance produced by type II alveolar cells.
Functions
• Reduces surface tension inside alveoli.
• Prevents alveolar collapse.
• Makes lung expansion easier.
• Improves respiratory efficiency.
Exam Tip
Surfactant = prevents alveolar collapse.
6. CONTROL OF RESPIRATION
