Air taken in through the nose provides the body with much needed oxygen.
Animals, as well as plants and other organisms, must breathe to survive. Plants breathe through openings in their leaves, called stomata, which release oxygen and pull in carbon dioxide. Animals have a different system for breathing, called the respiratory system.
Moving Oxygen
The respiratory system in animals consists of a series of organs that work in sequence to move air, containing oxygen, from the environment to the lungs. The organs involved include the nose, pharynx, trachea and lungs. From the lungs, oxygen is dispersed through the blood to the rest of the body. Cells all over the body use oxygen for their own respiratory processes.
The Nose
In the nose, air from the environment is pulled in where it is warmed and moistened. Bone structures in the nose form cavities where air circulates. Hair and cilia (hairlike projections) in these cavities filter dust and other particles from the air, purifying it for the rest of the body. Once purified, the nasal chambers open, and the air is released into the pharynx.
The Pharynx
The pharynx, a cavity in the back of the mouth also know as the throat, contains two tubes referred to as Eustachian tubes. These connect the pharynx to the middle ear, equalizing the air pressure. Tonsils are also located in the pharynx, along with adenoids. These structures filter microorganisms from the air before it passes into the trachea.
The Trachea
The trachea, also called the windpipe, is the connecting tube between the pharynx and the lungs. Between 16 and 20 open, C-shaped cartilage rings keep the trachea open and maintain its form. A flap called the epiglottis covers a small opening called the glottis, at the top of the trachea. This flap keeps food from traveling down the trachea when an animal is eating but opens when the animal is breathing.
The larynx, or voice box, is located in the trachea. The cartilage flaps that make up the larynx produce sound when vibrated by exhaling air.
At the bottom of the trachea, two bronchial tubes (bronchi) extend down. These tubes then branch out into smaller bronchial tubes (bronchioles). The combination is called a bronchial tree and ends with small air sacs called alveoli. The lungs are made up of around 300 million of these small sacs.
The Lungs
The alveoli in the lungs are surrounded by capillaries, through which red blood cells pass and collect oxygen from the alveoli. Carbon dioxide, produced during cellular respiration, is passed from the red blood cells and plasma to the capillaries. When an animal breathes, the carbon dioxide moves from the capillaries to the alveoli.
When the lungs expand during inhalation, the air pressure in them is reduced, drawing air into the alveoli.
Breathing is a passive activity, meaning animals do not make a conscious effort to breathe. Instead it is controlled by the amount of carbon dioxide in the blood, which regulates nerve impulses in the chest cavity. When carbon dioxide levels in the blood are high, nerve impulses increase, causing the rib cage and lungs to expand and draw in air.
Tags: carbon dioxide, alveoli lungs, blood cells, bronchial tubes, from environment, lungs expand, nerve impulses