Respiratory System
Respiratory System Structures
Nasal cavity - Your nose is divided into the external nose and the internal nasal cavity.
When you breathe in, air enters the cavity by passing through the nostrils. HAirs within the
cavity filter out dust, pollen and other foreign particles before the air passes into the two
passages of the nasal cavity. Here the air is warmed and moistened before it passes into the
nasopharynx. A sticky mucous layer traps smaller foreign particles, which tiny hairs called
cilia transport to the pharynx to be swallowed.
Epiglottis - A small flap of cartilage at the back of the tongue, the epiglottis closes the top of
the trachea when you swallow to ensure food and drink pass into your lungs.
Pharynx - The funnel-shaped pharynx connects the nasal cavity and mouth to the larynx
and oesophagus. Commonly called the throat, the pharynx is a small tube that measures
approximately 10-13cm from the base of the skull to the level of the sixth cervical vertebra.
The muscular pharynx wall is composed of skeletal muscles throughout its length. It is a
passageway for food and air, so special adaptations are required to prevent choking when
food or liquid is swallowed.
Larynx - The larynx or voice has rigid walls of muscle and cartilage, contains the vocal cords
and connects the pharynx to the trachea. It extends for about 5cm from the level of the third
to sixth vertebra.
Trachea - The trachea or windpipe denotes the start of the lower respiratory tract. It is about
12cm long 2cm in diameter. It contains rings of cartilage to prevent it from collapsing and is
very flexible. It travels down the neck in front of the oesophagus and branches into the right
and left bronchi.
Bronchus - The right and left bronchi are formed by the division of the trachea. They carry
air into the lungs. The right bronchus is shorter and wider than the left and is more common
for objects to become lodged. By the time inhaled air reaches the bronchi, it is warm so that
most impurities are clear as it is saturated with water vapour. Once inside the lungs, each
bronchus subdivides into lobar bronchi. Three are located on the right and two on the left.
They branch into segmental bronchi, which divides again into smaller and smaller bronchi.
Overall, there are approximately 23 orders of branching bronchial airways in the lungs. This
is due to the branching patterns, the bronchial network within the lungs is often called the
bronchial tree.
Bronchioles - Bronchioles are small airways that extend from the bronchi. They are about
1mm in diameter and are the first airway branches of the respiratory system that do not
contain cartilage. Bronchioles end in clusters of thin walled air sacs, known as alveoli.
Lungs - The paired right and left lung occupy most of the thoracic cavity and extend down to
the diaphragm. They hang suspended in the right and left pleural cavities straddling the
heart. The left lung is smaller than the right.
Respiratory System Structures
Nasal cavity - Your nose is divided into the external nose and the internal nasal cavity.
When you breathe in, air enters the cavity by passing through the nostrils. HAirs within the
cavity filter out dust, pollen and other foreign particles before the air passes into the two
passages of the nasal cavity. Here the air is warmed and moistened before it passes into the
nasopharynx. A sticky mucous layer traps smaller foreign particles, which tiny hairs called
cilia transport to the pharynx to be swallowed.
Epiglottis - A small flap of cartilage at the back of the tongue, the epiglottis closes the top of
the trachea when you swallow to ensure food and drink pass into your lungs.
Pharynx - The funnel-shaped pharynx connects the nasal cavity and mouth to the larynx
and oesophagus. Commonly called the throat, the pharynx is a small tube that measures
approximately 10-13cm from the base of the skull to the level of the sixth cervical vertebra.
The muscular pharynx wall is composed of skeletal muscles throughout its length. It is a
passageway for food and air, so special adaptations are required to prevent choking when
food or liquid is swallowed.
Larynx - The larynx or voice has rigid walls of muscle and cartilage, contains the vocal cords
and connects the pharynx to the trachea. It extends for about 5cm from the level of the third
to sixth vertebra.
Trachea - The trachea or windpipe denotes the start of the lower respiratory tract. It is about
12cm long 2cm in diameter. It contains rings of cartilage to prevent it from collapsing and is
very flexible. It travels down the neck in front of the oesophagus and branches into the right
and left bronchi.
Bronchus - The right and left bronchi are formed by the division of the trachea. They carry
air into the lungs. The right bronchus is shorter and wider than the left and is more common
for objects to become lodged. By the time inhaled air reaches the bronchi, it is warm so that
most impurities are clear as it is saturated with water vapour. Once inside the lungs, each
bronchus subdivides into lobar bronchi. Three are located on the right and two on the left.
They branch into segmental bronchi, which divides again into smaller and smaller bronchi.
Overall, there are approximately 23 orders of branching bronchial airways in the lungs. This
is due to the branching patterns, the bronchial network within the lungs is often called the
bronchial tree.
Bronchioles - Bronchioles are small airways that extend from the bronchi. They are about
1mm in diameter and are the first airway branches of the respiratory system that do not
contain cartilage. Bronchioles end in clusters of thin walled air sacs, known as alveoli.
Lungs - The paired right and left lung occupy most of the thoracic cavity and extend down to
the diaphragm. They hang suspended in the right and left pleural cavities straddling the
heart. The left lung is smaller than the right.
