The Pharynx

The clean air travels from the nasal passages to the pharynx.

The pharynx is located at the back of the throat. 

The pharynx divides into two tubes:

• Esophagus is the tube that connects the pharynx with the stomach.  It carries food, liquids and saliva from your mouth to the stomach..
• Trachea or windpipe is a bony tube portion of the respiratory tract that connects the larynx with the bronchial parts of the lungs.   Epiglottis is the flap cartilage located at the bottom of the pharynx.  It opens and closes the trachea.  It prevents the food from going to the trachea by closing it during swallowing.  The epiglottis is open to allow the flow of air in the breathing process most of the time.

The Larynx

From the pharynx, the clean air moves down to the larynx.

The Larynx or voice box is located between the pharynx and the trachea. Humans use the larynx to breathe, talk, and swallow.

The larynx contains the vocal cords that vibrate when air passes through them.

The Trachea or Windpipe

The trachea, or windpipe, is a bony tube portion of the respiratory tract that connects the larynx with the bronchial parts of the lungs that about 13 centimeters long.

The inner wall of the trachea is also lined with cilia.  The cilia catch the dust particles that reach the windpipe.  The dust particles are then pushed out and up toward the throat and mouth for expulsion.  This is why one coughs or sneezes just because of the  dirt gets into the upper respiratory tract.  The lower end of the trachea branches into two large tubes called the bronchi.

The Lungs

The Lungs are  the organs of respiration (in-charge for breathing).  The left bronchus leads to the left lung while the right bronchus leads to the right lung.  Each bronchus divides into smaller tubes called bronchial rami.  The bronchial rami branches off further into smaller tubes called bronchial tubes or bronchioles.  At the ends of these bronchioles are the tiny air sacs called alveoli.

The bronchioles and alveoli look like the branches of a tree.  Bronchi is the biggest branches that are covered by cilia and a thin film of mucus.  Dust and pollen are trapped by the mucus before they reach the alveoli.

Each of the lungs has 300 million alveoli.  Alveolus is surrounded by tiny blood vessels called capillaries. These are the smallest of blood vessels that help to distribute oxygenated blood from the arteries to the tissues and to feed deoxygenated blood from the tissues back to the veins. 

The Respiratory Process

Breathing is the process of respiration, by which air is taken into the lungs and carbon dioxide is pushed out of the lungs.

Breathing in is called inhaling (filling your lungs with air), and breathing out is called exhaling (pushing air with carbon dioxide out of the lungs).  

 The lungs are protected by a set of bones called the rib cage.  The rib cage is the set of bones that encloses the heart and lungs.  Diaphragm is located at the lower portion of the chest, it separates the chest from the abdomen.  Both the rib cage and the diaphragm are important in the breathing process.   When you inhale, the ribs move upward and outward while the diaphragm moves downward.   When you exhale, the opposite happens.  The ribs move downward and inward while the diaphragm moves upward.