RESPIRATORY SYSTEM

Respiratory System

Anatomy of the Respiratory System
What is respiration?

Respiration is the act of breathing:

inhaling (inspiration) - taking in oxygen
exhaling (expiration) - giving off carbon dioxide
What makes up the respiratory system?
The respiratory system is made up of the organs involved in breathing and consists of the:

nose
pharynx
larynx
trachea
bronchi
lungs
The upper respiratory tract includes the:

nose
nasal cavity
ethmoidal air cells
frontal sinuses
maxillary sinus
larynx
trachea
The lower respiratory tract includes the:

lungs
bronchi
alveoli
What do lungs do?
The lungs take in oxygen, which all cells throughout the body need to live and carry out their normal functions. The lungs also get rid of carbon dioxide, a waste product of the body's cells.

The lungs are a pair of cone-shaped organs made up of spongy, pinkish-gray tissue. They take up most of the space in the chest, or the thorax (the part of the body between the base of the neck and diaphragm).

The lungs are inside in a membrane called the pleura.

The lungs are separated from each other by the mediastinum, an area that contains the following:

heart and its large vessels
trachea (windpipe)
esophagus
thymus
lymph nodes
The right lung has three sections, called lobes. The left lung has two lobes. When you breathe, the air:

enters the body through the nose or the mouth


travels down the throat through the larynx (voice box) and trachea (windpipe)


goes into the lungs through tubes called main-stem bronchi

one main-stem bronchus leads to the right lung and one to the left lung


in the lungs, the main-stem bronchi divide into smaller bronchi


and then into even smaller tubes called bronchioles


bronchioles end in tiny air sacs called alveoli


Every minute we breathe, we take in 13 pints of air! That is we breathe about 6.15 liters of air every minute.
We breathe about 9 to 20 times every minute. Through every breath, we breathe in about half a liter of air.
We inhale and exhale air about 22,000 times per day and in the process, transport about 300 cubic feet of air (which is about 8.5 cubic meters of air)!
Human breathing mechanism is called tidal breathing, as air comes out the same way it goes in.
We exhale about half a liter of water vapor in a whole day.
Breathing is initiated by the diaphragm, which is a stretchable muscle under the lungs. When it contracts, the volume of the chest cavity rises and the air pressure drops. That is what enables the high pressure air outside, to enter the lungs and makes them expand like balloons.
When the diaphragm expands, lungs are emptied of air and we exhale it outside.
When air passes through the nose and into the nasal passage called the windpipe, it gets filtered, moistened and heated.

Breathing Mechanism


Humans breathe by flattening and contracting the diagram for inhalation and relaxing the diaphragm for exhalation. Intercostal muscles assist breathing.

In humans the chest cavity, or thorax, is separated from the abdominal cavity by a dome shaped muscle called the diaphragm.

Two lungs are enclosed within the thorax, which is supported by the ribs, and they are connected to the mouth and nose by the trachea. In an adult the trachea is about 11 cm long and 2.5 cm in diameter. It is supported by several horseshoe-shaped sections of cartilage that prevent the trachea collapsing and closing the airway.

Inhalation
On inhalation the diaphragm contracts and becomes flatter as it is lowered. In addition, the lower ribs swing upwards and outwards as the external intercostal muscles contract. These movements increase the volume of the thorax and the pressure within it falls to below atmospheric pressure. Consequently, air rushes into the lungs to fill this partial vacuum.

Exhalation
Relaxation of the external intercostals and the diaphragm allow a set of opposing muscles, the internal intercostal muscles, to return the thorax to its previous size. As the thorax diminishes in size air is expelled from the lungs. All English speech sounds are composed using exhaled air from the lungs, i.e. using a pulmonic air stream.