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Anatomy and physiology of Respiratory system

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Respiration

The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary history. In land animals the respiratory surface is internalized as linings of the lungs. Gas exchange in the lungs occurs in millions of small air sacs called alveoli in mammals and reptiles, but atria in birds. These microscopic air sacs have a very rich blood supply, thus bringing the air into close contact with the blood. These air sacs communicate with the external environment via a system of airways, or hollow tubes, of which the largest is the trachea, which branches in the middle of the chest into the two main bronchi. These enter the lungs where they branch into progressively narrower secondary and tertiary bronchi that branch into numerous smaller tubes, the bronchioles. In birds the bronchioles are termed parabronchi. It is the bronchioles, or parabronchi that generally open into the microscopic alveoli in mammals and atria in birds. Air has to be pumped from the environment into the alveoli or atria by the process of breathing which involves the muscles of respiration.In most fish, and a number of other aquatic animals (both vertebrates and invertebrates) the respiratory system consists of gills, which are either partially or completely external organs, bathed in the watery environment. This water flows over the gills by a variety of active or passive means. Gas exchange takes place in the gills which consist of thin or very flat filaments and lammelae which expose a very large surface area of highly vascularized tissue to the water.
Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants includes anatomical features such as stomata, that are found in various parts of the plant.
Human respiratory System
We cannot do without oxygen for even a little while, as we can without food or water.As cells use oxygen, they give off carbon dioxide, a waste product the body must get rid of. They also generate dangerous free radicals, the inescapable by-products of living in a world full of oxygen. But let’s get to the topic, the respiratory system.
The major function of the respiratory system is to supply the body with oxygen and dispose of carbon dioxide. To accomplish this function, the two processes inspiration and expiration , collectively called respiration, must happen. Inspiration is simply the intake of oxygen and expiration is the expell of carbon dioxide.
Parts of the Human Respiratory System
Your respiratory system includes your:

Nose and nasal cavity
Sinuses
Mouth
Throat (pharynx)
Voice box (larynx)
Windpipe (trachea)
Diaphragm
Lungs
Bronchial tubes/bronchi
Bronchioles
Air sacs (alveoli)
Capillaries

How do we breath?
Bow Do We Breathe?reathing starts when you inhale air into your nose or mouth. It travels down the back of your throat and into your windpipe, which is divided into air passages called bronchial tubes.
For your lungs to perform their best, these airways need to be open.  They should be free from inflammation or swelling and extra mucus.
As the bronchial tubes pass through your lungs, they divide into smaller air passages called bronchioles. The bronchioles end in tiny balloon-like air sacs called alveoli. Your body has about 600 million alveoli.
The alveoli are surrounded by a mesh of tiny blood vessels called capillaries. Here, oxygen from inhale air passes into your blood.
As the bronchial tubes pass through your lungs, they divide into smaller air passages called bronchioles. The bronchioles end in tiny balloon-like air sacs called alveoli. Your body has about 600 million alveoli.