Respiration is necessary for every living being, and there’s a distinct, special organ system working constantly to carry it out. In humans, it is called the respiratory system.

The human body is a complex structure of many organs and organ systems, and the human respiratory system is one of them. The respiratory system functions continuously without a break, as we breathe by inhaling oxygen and exhaling carbon dioxide. Breathing is essential for our survival and effective for the functioning of all our organs. The respiratory system is made up of a complicated collection of organs and tissues that let you breathe. The muscles that propel your lungs are also part of the respiratory system. These parts work together to deliver oxygen throughout the body while also removing waste gasses like carbon dioxide.

The structure of the lungs is created in such a way that it helps the exchange of gasses. The other parts of the respiratory system include the nose, larynx, pharynx, trachea or the windpipe, bronchi, lungs, blood vessels, the airways for the passage of air, and the muscles that support the breathing.

All these parts together form the respiratory tract that starts from the external nostrils and nasal chamber and goes up to the lungs. Warms and moisturizes the air to the appropriate humidity level for your body. Your body's cells are supplied with oxygen. When you exhale, you remove waste gasses from your body, including carbon dioxide. Protects dangerous substances and irritants out of your airways.

• Nose 

We inhale air through our nose which is the first step in the process of respiration. The nose and nasal cavity are the initial segment of the body's airway—the respiratory tract through which air moves—and are the principal external opening for the respiratory system. The nose is a cartilage, bone, muscle, and skin structure on the face that supports and protects the nasal cavity's anterior section. Before being expelled into the environment, air leaving the body through the nose returns moisture and heat to the nasal cavity.

• Larynx

These are two cartilaginous chords, situated at the joining point of the pharynx and trachea.  They are also called the voice box. The laryngopharynx and the trachea are connected by a brief piece of the airway. The larynx is found in the anterior part of the neck, slightly below the hyoid bone and above the trachea. The form of the larynx is determined by various cartilage components. The larynx has specific structures termed vocal folds, which allow the body to produce speaking and singing sounds in addition to cartilage. Vocal folds are mucous membrane folds that vibrate to make vocal sounds. The pitch produced by the vocal folds can be altered by altering the tension and vibration speed of the vocal folds.

• Pharynx

The pharynx is a common path for the passage of both air and food, to their respective organ systems. The pharynx, often known as the throat, is a muscular funnel that runs from the nasal cavity's posterior end to the esophagus and larynx's superior end. The nasopharynx, oropharynx, and laryngopharynx are the three parts of the pharynx. The nasopharynx is the upper part of the pharynx that is located in the back of the nasal cavity. The nasopharynx receives inhaled air from the nasal cavity and transports it to the oropharynx, which is positioned in the back of the oral cavity. At the oropharynx, air inhaled through the mouth cavity enters the pharynx. The epiglottis is a flap of elastic cartilage between the trachea and the esophagus that serves as a switch between the two.

• Trachea

The trachea or the windpipe is like a long tube that takes the inhaled air into the further process. It is divided into left and right bronchi. The trachea, or windpipe, is a 5-inch long tube coated with pseudostratified ciliated columnar epithelium and formed up of C-shaped hyaline cartilage rings. The trachea's primary role is to maintain a free airway for air to enter and exit the lungs. Furthermore, the mucus produced by the epithelium lining the trachea collects dust and other impurities, preventing them from reaching the lungs. Mucus is moved superiorly toward the throat by cilia on the surface of epithelial cells, where it can be eaten and processed in the gastrointestinal system.

• Bronchi

Bronchi are further subdivided into small, finer channels called bronchioles. These bronchioles have balloon or bag-like structures at their ends that are known as alveoli. The airway splits into left and right branches at the inferior end of the trachea, known as the main bronchi. Before branching off into smaller secondary bronchi, the left and right bronchi enter each lung. The secondary bronchi—two in the left lung and three in the right lung—carry air into the lobes of the lungs. Within each lobe, the secondary bronchi branches into several smaller tertiary bronchi. The tertiary bronchi are divided into several smaller bronchioles that travel throughout the lungs. Each bronchiole then differentiates into multiple smaller branches, known as terminal bronchioles, with a diameter of less than a millimeter. Finally, the air is carried to the lungs' alveoli by millions of small terminal bronchioles.

• Lungs

Then there are lungs. The inhaled air is purified, and the oxygen necessary for all the body functioning is passed to various organs through the blood vessels. The exchange of oxygen and carbon dioxide takes place in small bags, alveoli. And the impure air of the carbon dioxide is exhaled out of the body through the same tract. The lungs are a pair of big, spongy organs located in the thorax, above the diaphragm, and lateral to the heart. A pleural membrane surrounds each lung, providing space for it to expand as well as a negative pressure area relative to the rest of the body. As the lungs relax, they passively fill with air thanks to the negative pressure.

• Respiratory Tract

The respiratory tract of the human respiratory system is a series of organs, starting from the external organs and going up to the internal ones. Each of these organs performs a distinct role in the respiratory system function.  

The respiratory system function is a very important metabolic process in our body that plays a crucial role in all living beings. 

• Inhalation and Exhalation:

It begins by breathing and ends by exhalation, that’s the simplest explanation. But during and after these two acts, several processes are going on endlessly in our bodies.

• Exchange of Gasses Between Lungs and Bloodstream:

The oxygen is exchanged for carbon dioxide and is pumped through the bloodstream. Hundreds of millions of small sacs called alveoli are used to carry out the breathing process. The oxygen inhaled by the alveoli diffuses into the pulmonary capillaries that surround them. It attaches to hemoglobin molecules in red blood cells and then circulates around the body.

• Exchange of Gasses Between Bloodstream and Body Tissues

The oxygen-carrying blood releases oxygen into body tissues, through the walls of capillaries. Internal respiration, another important function of the respiratory system, transports oxygen to cells and eliminates waste carbon dioxide. Red blood cells transport oxygen received from the lungs around the body via the vasculature in this respiratory process. When oxygenated blood enters the small capillaries, red blood cells release oxygen. It diffuses into body tissues through capillary walls. Carbon dioxide diffuses from the tissues into red blood cells and plasma in the meantime. Deoxygenated blood carries the carbon dioxide back to the lungs.

• The Vibration of the Vocal Cords

The larynx muscles move when we speak, creating sound and vibration. The same process happens during the exhalation also.

• Olfaction or Smelling

When we inhale air, the chemicals present in the air activate the receptors of the nervous system on the cilia, and we can identify the smell. The sense of smell, or olfaction, is another particular sense that is affected by chemical stimuli. In the superior nasal cavity, the olfactory receptor neurons are integrated into a small area of the nasal epithelium.

Respiration in humans is divided into two types –

1. The External Respiration 

The exchange of gasses between the air in the alveoli and the blood in the capillaries that border the alveolar walls is known as external respiration. The partial pressure of oxygen in the air that enters the lungs from the atmosphere is higher than the partial pressure of carbon dioxide in the blood in the capillaries. The gasses diffuse passively through the simple squamous epithelium lining of the alveoli due to the difference in partial pressures. The passage of oxygen from the air into the blood and carbon dioxide from the blood into the air is the end consequence of external respiration. After then, the oxygen may be carried to the body's tissues, while the carbon dioxide is exhaled and discharged into the atmosphere.

2. Internal Respiration 

It involves the exchange of gasses between the blood and cells in the body. Lungs are the largest organ in the respiratory system. The exchange of gasses between the blood in capillaries and the body's tissues is known as internal respiration. Capillary blood has a higher oxygen partial pressure and a lower carbon dioxide partial pressure than the tissues through which it travels. Gasses diffuse through the endothelial lining of capillaries along pressure gradients from high to low pressure due to the difference in partial pressures. The diffusion of oxygen into the tissues and the diffusion of carbon dioxide into the blood are the end results of internal respiration.

It is evident that something is obstructing our ability to exchange carbon dioxide for oxygen. Allergies, asthma, pneumonia, and lung cancer are just a few of the health issues that can cause respiratory problems. Infection (bacterial or viral), environmental exposure (pollution or cigarette smoke, for example), genetic inheritance, or a mix of variables are among the causes of these problems. We don't seek medical help till the problem has progressed because the onset is so slow. Symptoms may appear gradually, as in the case of alpha-1 antitrypsin deficiency (A1AD), and are frequently misunderstood or underdiagnosed. A1AD genetic risk can be detected through DNA health testing.

• Asthma: Your airways are congested, and you're producing an excessive amount of mucus.

• Bronchiectasis: Bronchial walls get thicker as a result of inflammation and infection.

• COPD (chronic obstructive pulmonary disease): A lung illness that affects millions of people (COPD). Over time, this long-term ailment deteriorates. Bronchitis and emphysema are two of the most common conditions.

• Pneumonia: Inflammation of the alveoli is caused by infection. It's possible that they'll become clogged with pus or fluid.

• Tuberculosis: This deadly infection is brought on by a bacterium. It most commonly affects your lungs, but it can also impact your kidneys, spine, or brain.

• Lung Cancer: Cancer of the lungs A tumour formed when cells in the lungs alter and expand. This is frequently the result of smoking or inhaling other substances.

• Cystic Fibrosis: Cystic fibrosis is a disease characterised by the presence of cysts in the lungs This condition develops over time and is caused by a genetic issue. It leads to recurrent lung infections.

• Pleural Effusion: Pleural effusion is a condition in which fluid accumulates in the lungs Between the tissues that line your lungs and chest, too much fluid accumulates.

• Idiopathic Pulmonary Fibrosis: Idiopathic pulmonary fibrosis is a condition in which the tissue of your lungs gets damaged and unable to function properly.

• Sarcoidosis: Granulomas are small clusters of inflamed cells that grow in the lungs and lymph nodes.