Anatomy and Physiology of Respiratory System | A Complete Guide

The respiratory system is one of the 11 organ systems of the body.

It is responsible for the life and energy in our body.

It is under involuntary control in our bodies.

We breathe in air rich in oxygen by the process called inspiration and breathe out air rich in CO2 by a process called as expiration.

The respiratory system helps in the safe exchange of gases from the outer atmosphere to inside the body.

The physiology of the respiratory system of the human body is not a problematic one mostly, but it is a delicate one and if neglected or hampered in early life, it can reduce the life span and quality of life drastically.

The disorders of the respiratory system are many but are not fatal on an instant basis. They can be reduced or treated by proper medical care.

See the difference between anatomy vs. physiology.

Anatomy and Physiology of Respiratory System | Main Parts

The respiratory system parts consist of

  1. Nose
  2. Pharynx
  3. Larynx
  4. Trachea
  5. Two bronchi
  6. Two lungs (inside them alveoli).

Anatomy and Physiology of Respiratory System | labelled Diagram

1. Nose: This is the starting point of the pulmonary system and exposed to the external environment. It partly made of cartilaginous bone and skull bone. It is the entrance and also the exit for air into the body.

It has odor glands in the nostril’s walls. Also, there is a small tuft of hair inside to entrap any dust particles passing along with air.

2. Pharynx: This is present immediately after the nose. It is a common channel for both the digestive system and the respiratory system. It is divided into three parts as nasopharynx, oropharynx, and also laryngopharynx.

3. Larynx: This is the tract of the respiratory system in the throat. It is responsible for sound and is made of cartilage.

4.Trachea: This is a longer part of the track and is made of circles of cartilaginous bones with a capacity to contract and relax. This trachea divides into two bronchi before entry into the lungs.

5. Bronchi:  These are two of them as the right and left, and each enters into the respective lung. Bronchi further divide into smaller branches as bronchioles which almost extend into alveoli of lungs.

6. Lungs: These are important organs of the respiratory system. Here, the actual process of respiration occurs. They are large sac-like structures (balloon-like). There are two in number with one on the left side and others on the right of thorax or chest. They are very thin layered and a bit transparent. Their walls have many passing tiny blood vessels. They are very delicate to sharp objects and get punctured easily on an injury. Inside these lungs, there are small sacs called alveoli which are involved in the exchange of gases between blood and air.

Cilia: This tiny bristle-like structure on the surface of the respiratory tract is helping in the movement of dust and phlegm from inside to out of the track. They move in one specific direction only. In older people and people with inflammation, the cilia activity is low and hence phlegm accumulates a lot in their respiratory tract.

Anatomy and Physiology of Respiratory System

Phlegm: Phlegm is a mucous secretion in the respiratory tract aimed to keep the tract moist and remove any dust particles entered into tract by flowing towards the nose. This movement of phlegm is helped by cilia on the surface of the tract. But profuse secretion and accumulation of mucus can be havoc to patients.

Functions of Respiratory organs:

Nose: Being the first passage of the respiratory system, the nose performs vital functions.

It warms up the air, filters and even moistens it.

Warming: When air enters the nose, the mucous wall in the nose gets in contact. Due to the high blood supply to this layer, the air gets warmed.

Cleaning and filtering: The air might have bacteria and dust particles. These are trapped in the nose. Hair in the nose traps large particles while the moist mucosa traps bacteria and small dust particles.

Moistening: When air travels over the mucous layer, the moisture present saturates the air with water vapor.

Besides the above, the nose acts as a sense of smell.

Pharynx: This is a tube of approximately 14 centimeters long. It starts from the base of the skull and ends at the level of the 6th cervical vertebra (neck region) It is divided into three parts are nasopharynx, oropharynx, and laryngopharynx.


1. It helps in the passage of air and food.

2. Warms and humidifies air.

3. Protection against microbes by producing antigens from tonsils.

4. In the production of speech, it helps to resonate sound coming out from the larynx.

Physiology of respiratory system

  • Gaseous exchange: Helps in the intake of oxygen (O2) into the blood from the atmosphere and leaves out CO2.Anatomy and Physiology of Respiratory System-gaseous exchange
  • Metabolism: Some drugs and substances get metabolized in the lungs due to heavy O2 content.
  • Excretory in function: Lungs help in excretion of gaseous or volatile substances like Ammonia (NH3), Alcohol, etc. Hence, when one drinks alcohol, its odor is detected in the breath. So, breath analyzers are used to test drivers.

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