respiratory system consists of the lungs and tubes associated with the
lungs. It is located in the thorax or chest. The thorax is surrounded by
the ribs. The diaphragm forms the base of the thorax.
Contractions of the diaphragm and the intercostals
muscle change the size of the thorax and, thus, cause air to move in and
out of the lungs.
The main job of the respiratory system is to get oxygen into
the body and get waste gases out of the body. It is the function of the
respiratory system to transport gases to and from the circulatory system.
of the Respiratory System
THE HUMAN RESPIRATORY
SYSTEM CONSISTS OF THE NOSE, NASAL CAVITY, PHARYNX, LARYNX, TRACHEA, SMALLER
CONDUCTING PASSAGEWAYS (BRONCHI AND BRONCHIOLES), AND LUNGS.
Nose or Nasal Cavity
As air passes
through the nasal cavities it is warmed and humidified, so that air that
reaches the lungs is warmed and moist.
The Nasal airways are lined with cilia and kept moist by mucous
secretions. The combination of cilia and mucous helps to filter out solid
particles from the air an Warm and moisten the air, which prevents damage to
the delicate tissues that form the Respiratory System. The moisture in the nose
helps to heat and humidify the air, increasing the amount of water vapour the
air entering the lungs contains. This helps to keep the air entering the nose
from drying out the lungs and other parts of our respiratory system. When air
enters the respiratory system through the mouth, much less filtering is
done. It is generally better to take in air through the nose.
To review: he nose does the following:1.
Filters the air by
the hairs and mucous in the nose
2. Moistens the air
Warms the airThe
The pharynx is also called the throat.
As we saw in the digestive system, the epiglottis closes off the trachea
when we swallow. Below the epiglottis is the larynx or voice
box. This contains 2 vocal cords, which vibrate when air passes by
them. With our tongue and lips we convert these vibrations into speech.
The area at the top of the trachea, which contains the larynx, is called
trachea or windpipe is made of muscle and elastic fibres with
rings of cartilage. The cartilage prevents the tubes of the trachea from
collapsing. The trachea is divided or branched into bronchi and
then into smaller bronchioles. The bronchioles branch off into alveoli.
The alveoli will be discussed later.
tubes are lined with mucous-secreting cells and tiny hairs called cilia.
The mucous traps bacteria, dust and viruses. The cilia beat and create an
upward current. This moves the mucous up and into the oesophagus. Here it goes
to the stomach. When we clear our throats we force the mucous away from our
vocal cords. This is often called coughing. It is used to get rid of irritants
and excess mucous from our respiratory system.
The lungs are spongy structure where the
exchange of gases takes place. Each lung is surrounded by a pair of pleural
membranes. Between the membranes is pleural fluid, which reduces
friction while breathing. The bronchi are divided into about a million
bronchioles. The ends of the bronchioles are hollow air sacs called alveoli.
There are over 700 million alveoli in the lungs. This greatly increases the
surface area through which gas exchange occurs. Surrounding the alveoli are capillaries.
The lungs give up their oxygen to the capillaries through the alveoli.
Likewise, carbon dioxide is taken from the capillaries and into the alveoli.
Body cells use the
inhaled oxygen gotten from the alveoli of the lungs. In turn, they produce
carbon dioxide and water, which is taken to the alveoli and then exhaled. These
exchanges occur as a result of diffusion. In each case the materials move from
an area of high concentration to an area of lower concentration.
Here, the blood flows from the heart to
the lungs. Here the blood flows from the lungs to the body cells.
The alveoli take in the water and the carbon dioxide The body cells take in the oxygen and give off the and
give off the oxygen.