Respiration

What is Respiration?

Respiration is the chemical process of releasing energy by breaking down glucose for carrying out life processes.

Respiration in Human Beings

• Every cell in the human body needs a constant supply of oxygen to survive. 
• The lungs and airways of the Respiratory system deliver this oxygen and also expel waste carbon dioxide.
• We take in air through the mouth and nose into the lungs. 
• Oxygen from the air seeps through the lung membranes into the bloodstream where it is carried to all the body’s cells. 
• These cells burn oxygen to make energy, in a process called cellular respiration. This process causes cells to release another gas -carbon dioxide. This is carried back in the blood to the lungs to be exhaled.

Also Check – Importance Of Respiration

4 Major Stages of Respiration

In Humans (as in most other animals) there are Four major Stages of Respiration :

1. Breathing
2. Gaseous transport
3. Tissue Respiration
4. Cellular Respiration

1. Breathing

This is a physical process in which the atmospheric air is taken in and forced out of the oxygen-absorbing organs, the lungs.

2. Gaseous Transport

The oxygen absorbed by the blood in the lungs is carried by the RBCs as oxyhaemoglobin throughout the body by means of arteries. The carbon dioxide from the tissues is transported to the lungs by the blood by means of veins in two ways:

• As bicarbonates dissolved in plasma.
• In combination with the hemoglobin of RBCs as carbamino-hemoglobin.

3. Tissue Respiration

The terminal blood vessels, i.e., the capillaries deliver the oxygen to the body cells or tissues where oxygen diffuses through their thin walls and in a similar way, the capillaries pick up the carbon dioxide released by them.

4. Cellular Respiration

The complex chemical changes which occur inside the cell to release energy from glucose.

Human Respiratory Organs and their Functions 

In Human Beings many organs take part in the process of respiration. We call them organs of the Respiratory System.

The parts of the Human Respiratory System and their respective functions are as follows

Nose/ Nostrils

• The external part of the nose bears two nostrils separated by a cartilaginous septum.
• The hairs present in the nostrils prevent large particles from entering the system. 
• The two nostrils open into a pair of nasal chambers. 

3 Important Functions of Inner lining of the Nasal Chambers

The Inner lining of the Nasal Chambers performs three functions

1. It warms the air as it passes over.
2. It adds moisture to the air.
3. Its mucous secretion entraps harmful particles.

The Pharynx

Also Check- Mechanism of gaseous exchange in Human Beings.

• The nasal chambers open at the back into a wide cavity, the pharynx, situated at the back of the mouth.
• It is a common passage for air and food.
• It leads into an air tube, the trachea (windpipe) and a food tube (esophagus) located dorsally behind the trachea. When not in use, the food tube is partially collapsed as it has soft walls.
• The entrance to the trachea is guarded by a flap called Epiglottis which closes it at the time of swallowing food.
• Incomplete closure of epiglottis during swallowing causes cough.

The Larynx

• The larynx or the voice-box  is a hollow cartilaginous structure located at the start of the Windpipe.
• You can feel it with your fingers in the front part of your neck. When you swallow something, this part rises and falls.
• The larynx contains two ligamentous folds called vocal cords. Air expelled forcibly through the vocal cords vibrates them producing sound.
• By adjusting the distance between the two cords and their tension by means of attached muscles, a range of sounds can be produced.

The Trachea

• The trachea is a tube which is commonly known as windpipe.
• The air passes from the pharynx and goes into the trachea. Incomplete rings of cartilage keeps track open allowing the passage of air to the lungs.
• Trachea doesn’t collapse even when there is no air in it because it has supported by rings of soft bones called cartilage.

The Bronchi

The trachea runs down the neck and divides into two smaller tubes called bronchi at its lower end after entering the thoracic cavity. The two bronchi are connected to the two lungs. The singular of bronchi is bronchus.

The Bronchioles

Each bronchus divides in the lungs to form a large number of smaller tubes called bronchioles. Each bronchiole finally terminates into  many tiny air sacs at their ends. 

The Alveoli

• The pouch like air sacs at the end of the smallest bronchioles are called alveoli.
• A large number of alveoli increases the surface area for the exchange of gases.
• The walls of alveoli are very thin and they are surrounded by very thin blood capillaries.
• It is in the alveoli that oxygen is taken into the body and carbon dioxide is eliminated.
• There are millions of alveoli in the lungs. Human alveolar surface when spread can cover area of 80 square meters.

Also Check – Compare the Functioning of Alveoli in the Lungs and Nephrons in the Kidneys with respect to their Structure and Functioning

Protective inner lining of respiratory passage.

• The entire inner lining of the larynx, trachea, bronchi and bronchioles is formed of ciliated
• epithelium. During lifetime the cilia are constantly in motion driving any fluid (mucus) that is on them and also any particles that may have come in with the air towards the mouth.

Ribs

These are 12 pairs of bones that form a cage in the thoracic region.Lungs and heart a safer place. Movement of intercostal muscles attached to ribs help in breathing.

The Lungs

• The Lungs are a pair of spongy and elastic organs formed by the air sacs, their connecting bronchioles, blood vessels, etc.
• These are primary organs for respiration, which are located on the two sides of heart. This transport O2 from the atmosphere into the blood and release CO2 from blood to atmosphere. They are enclosed by the protective membrane called pleura.
• The two lungs are roughly cone-shaped, tapering at the top and broad at the bottom. 
• The left lung has two lobes and the right lung has three.
• The left lung is slightly smaller to accommodate the heart in between.

Also Check- Differentiate Between Aerobic and Anaerobic Respiration

Membranous coverings of the Lungs.

• Each lung is covered by two membranes, the inner pleura and outer pleura with a watery fluid in the pleural cavity found between the two membranes.
• This arrangement provides lubrication for free movement of the expanding and contracting lungs.
• The lungs occupy the greater part of the thoracic cavity. They are located close to the inner surface of the thoracic wall and their lower bases closely rest on the diaphragm.

Diaphragm

• The diaphragm is a sheet of muscles below the lungs. It helps in breathing in and breathing out.
• Diaphragm is the partition between the thorax and the abdomen and forms the base of chest cavity.
• When we breathe in air, the diaphragm and muscles attached to the ribs contract due to which of the chest cavity expands. The expansion movement of the chest increase the volume inside the chest cavity.
  

Also Check – Role of Respiratory Pigment in Respiration

Blood Supply to the Lungs

• The right auricle pumps all the deoxygenated blood received in it from the body into the right ventricle, which in turn, pumps it into the lungs through the main pulmonary artery.
• The pulmonary artery, soon after its emergence, divides into two branches entering their respective lungs.
• Inside the lungs, they divide and redivide several times to ultimately form capillaries around the air sacs. 
• Veins arising from these capillaries join and rejoin to form two main pulmonary veins from each lung which pour the oxygenated blood into the left auricle of the heart.