GNM 1st Year | Anatomy & Physiology
A clear, exam-focused study guide to the respiratory system, covering the respiratory organs, lungs, breathing, gas exchange and regulation of respiration.
Introduction
The respiratory system is responsible for bringing oxygen into the body and removing carbon dioxide. It works closely with the cardiovascular system to supply oxygen to tissues and remove carbon dioxide produced during cellular metabolism.
For GNM students, understanding the respiratory system is important because breathing, oxygenation and respiratory assessment are central to nursing practice.
What Is the Respiratory System?
The respiratory system is a group of organs and structures that conduct air into and out of the lungs and allow exchange of oxygen and carbon dioxide between the air and blood.
The main processes associated with respiration include:
- Movement of air into and out of the lungs.
- Exchange of oxygen and carbon dioxide between alveoli and blood.
- Transport of respiratory gases by the blood.
- Exchange of gases between blood and body tissues.
Main Parts of the Respiratory System
The respiratory system can be broadly divided into the upper and lower respiratory tracts.
Upper Respiratory Tract
- Nose and nasal cavity
- Paranasal sinuses
- Pharynx
Lower Respiratory Tract
- Larynx
- Trachea
- Bronchi
- Bronchioles
- Lungs
- Alveoli
Nose and Nasal Cavity
The nose is the main entry point for air. The nasal cavity is lined with mucous membrane and contains hairs and other structures that help condition inspired air.
Main functions:
- Provides a passage for air.
- Filters inhaled particles.
- Warms inspired air.
- Humidifies inspired air.
- Contains receptors involved in the sense of smell.
Pharynx
The pharynx is a muscular passage located behind the nose and mouth. It serves as a common passage for the respiratory and digestive systems.
It is divided into:
- Nasopharynx
- Oropharynx
- Laryngopharynx
Larynx
The larynx, commonly called the voice box, connects the pharynx with the trachea. It contains the vocal cords and plays an important role in producing sound.
The epiglottis helps protect the airway during swallowing by helping prevent food and liquid from entering the lower respiratory tract.
Trachea
The trachea, or windpipe, is a tube that carries air from the larynx toward the bronchi.
Its wall contains C-shaped rings of cartilage that help keep the airway open. The lining contains cilia and mucus, which help trap and move inhaled particles toward the pharynx.
Bronchi and Bronchioles
The lower end of the trachea divides into the right and left main bronchi. Each main bronchus enters its corresponding lung and divides repeatedly into smaller airways.
The smaller branches are called bronchioles. Bronchioles ultimately lead toward the respiratory portions of the lungs where gas exchange occurs.
Lungs
The lungs are the main organs of respiration. They are located in the thoracic cavity on either side of the mediastinum.
Right Lung
The right lung is divided into three lobes:
- Superior lobe
- Middle lobe
- Inferior lobe
Left Lung
The left lung is divided into two lobes:
- Superior lobe
- Inferior lobe
The left lung is slightly smaller because the heart occupies space mainly on the left side of the thoracic cavity.
Pleura
The lungs are covered by a thin serous membrane called the pleura.
It has two layers:
- Visceral pleura: Closely covers the surface of the lung.
- Parietal pleura: Lines the inner surface of the thoracic cavity.
Between these layers is the pleural cavity, which contains a small amount of lubricating fluid that reduces friction during breathing.
Alveoli
Alveoli are microscopic air sacs located at the ends of the respiratory passages. They are the main sites of gas exchange between air and blood.
The alveolar walls are very thin and are closely associated with pulmonary capillaries. This arrangement provides a short pathway for oxygen and carbon dioxide to move between the alveolar air and blood.
Alveoli are numerous and provide a large surface area for efficient gas exchange.
Respiratory Membrane
The respiratory membrane is the thin barrier across which oxygen and carbon dioxide diffuse between the alveolar air and pulmonary blood.
Its thin structure helps gases move efficiently down their concentration or partial-pressure gradients.
Mechanics of Breathing
Breathing, or pulmonary ventilation, is the movement of air into and out of the lungs.
It consists mainly of:
- Inspiration
- Expiration
Inspiration
Inspiration is the process of breathing air into the lungs.
During normal inspiration:
- The diaphragm contracts and moves downward.
- The external intercostal muscles contract.
- The volume of the thoracic cavity increases.
- Pressure within the lungs falls relative to atmospheric pressure.
- Air moves into the lungs.
Expiration
Expiration is the process of moving air out of the lungs.
During quiet expiration:
- The diaphragm relaxes and moves upward.
- The thoracic cavity becomes smaller.
- Pressure within the lungs increases relative to atmospheric pressure.
- Air moves out of the lungs.
Role of the Diaphragm
The diaphragm is the major muscle of normal quiet breathing. It is a dome-shaped muscle separating the thoracic and abdominal cavities.
When the diaphragm contracts, it flattens and increases the volume of the thoracic cavity. When it relaxes, it returns toward its dome-shaped position.
Exchange of Gases
Gas exchange occurs mainly in the alveoli.
Exchange of Oxygen
Oxygen from inhaled air moves from the alveoli into the pulmonary capillary blood because of a difference in oxygen partial pressure.
Exchange of Carbon Dioxide
Carbon dioxide moves from the blood into the alveoli and is then removed from the body during expiration.
Gas exchange occurs primarily by diffusion across the respiratory membrane.
Transport of Oxygen
Most oxygen in the blood is transported bound to haemoglobin inside red blood cells. A small amount is dissolved directly in plasma.
Haemoglobin therefore plays an important role in transporting oxygen from the lungs to body tissues.
Transport of Carbon Dioxide
Carbon dioxide is transported in the blood in several forms. Most is transported as bicarbonate ions, while smaller amounts are carried bound to proteins such as haemoglobin or dissolved in plasma.
External and Internal Respiration
External Respiration
External respiration refers to the exchange of oxygen and carbon dioxide between the alveoli and pulmonary capillary blood.
Internal Respiration
Internal respiration refers to the exchange of gases between systemic blood and body tissues.
Regulation of Respiration
Breathing is regulated by respiratory centres in the brainstem. These centres receive information about changes in carbon dioxide, oxygen and blood acidity and adjust breathing accordingly.
Under normal conditions, carbon dioxide levels and the resulting changes in blood pH are important factors influencing ventilation.
Respiratory Rate
Respiratory rate is the number of breaths taken in one minute.
When assessing respiration, a nurse should observe:
- Respiratory rate
- Rhythm
- Depth
- Effort of breathing
- Chest movement
- Presence of abnormal sounds
Changes in respiratory rate or breathing pattern may provide important information about a patient's condition.
Important Respiratory Terms
| Term | Meaning |
|---|---|
| Ventilation | Movement of air into and out of the lungs. |
| Inspiration | Movement of air into the lungs. |
| Expiration | Movement of air out of the lungs. |
| Diffusion | Movement of gases across the respiratory membrane. |
| External respiration | Gas exchange between alveoli and pulmonary blood. |
| Internal respiration | Gas exchange between systemic blood and tissues. |
Clinical and Nursing Relevance
Knowledge of respiratory anatomy and physiology is essential for nursing assessment and patient care.
A nurse may assess respiratory function by observing breathing pattern, respiratory rate, oxygen saturation, chest movement and signs of respiratory distress.
Common clinical symptoms such as breathlessness, cough, wheezing, chest discomfort and abnormal respiratory sounds may require further assessment according to the patient's condition.
Understanding normal respiratory physiology also helps nurses recognise changes in oxygenation and ventilation and communicate important findings to the healthcare team.
Quick Revision
- Main organs: Nose, pharynx, larynx, trachea, bronchi, bronchioles and lungs.
- Functional units: Alveoli are the main sites of gas exchange.
- Right lung: Three lobes.
- Left lung: Two lobes.
- Main muscle of quiet breathing: Diaphragm.
- Inspiration: Air moves into the lungs.
- Expiration: Air moves out of the lungs.
- Oxygen transport: Mainly through haemoglobin.
- Carbon dioxide transport: Mainly as bicarbonate ions.
- Gas exchange: Mainly occurs by diffusion across the respiratory membrane.
Frequently Asked Questions
What is the main function of the respiratory system?
The main function is to bring oxygen into the body and remove carbon dioxide. The respiratory system also contributes to functions such as voice production and regulation of acid-base balance.
Where does gas exchange occur?
Gas exchange occurs mainly across the walls of the alveoli and surrounding pulmonary capillaries.
Which is the main muscle of breathing?
The diaphragm is the main muscle involved in normal quiet breathing.
How many lobes does the right lung have?
The right lung has three lobes: superior, middle and inferior.
How many lobes does the left lung have?
The left lung has two lobes: superior and inferior.
Related GNM Study Resources
After studying this chapter, use the Important Questions on Respiratory System for GNM 1st Year for examination preparation.
You can also test your understanding with the Respiratory System MCQs for GNM 1st Year.
Disclaimer: This article is provided for nursing education and examination preparation. It is not a substitute for professional medical advice, diagnosis or treatment.