The respiratory system

The respiratory system I
Functional Anatomy
Respiratory Stems
• The organs of the
respiratory system
include the nose,
pharynx, trachea, bronchi
and their smaller
branches, and the lungs,
which contain the alveoli
or terminal air sacs
• Consists of an upper
respiratory tract (nose to
larynx) and a lower
respiratory tract ( trachea
onwards) .
Conducting Zone
Conducting zone
– Respiratory passages that
carry air to the site of gas
– Filters, humidifies and
warms air
– includes the nose, nasal
cavity, pharynx, larynx,
trachea, and progressively
smaller airways, from the
primary bronchi to the
terminal bronchioles
Respiratory Zone
Respiratory zone
–Site of gas exchange
–Composed of
• Respiratory
• Alveolar ducts
• Alveolar sacs
The Nose
• It is the only externally visible part of the
respiratory system
• During breathing, air enters the nose by
passing through the external nares, or nostrils
• The interior of the nose consists of the nasal
cavity, divided by a midline nasal septum
The Nose
• The olfactory receptors for
the sense of smell are
located in the mucosa in
the slit like superior part of
the nasal cavity, just
beneath the ethmoid bone
• The rest of the mucosa
lining the nasal cavity
called respiratory mucosa,
rests on a rich network of
thin-walled veins which
warms the air as it flows
Mucosa lining function
• Moistens the air and traps incoming bacteria
and other foreign debris
• The ciliated cells of the nasal mucosa (Cillia)
create a gentle current that moves
contaminated mucus posteriorly towards the
throat, where it is swallowed and digested by
stomach juices
• The lateral walls of the nasal
cavity are uneven owing to
the 3 mucosa covered
projections or lobes called
• This greatly increases the
surface area of the mucosa
exposed to air
• It also increases the air
turbulence in the nasal cavity,
prevent particles from
reaching the lungs
• The nasal cavity is
separated from the oral
cavity below by a
partition, the palate
• Anteriorly, where the
palate is supported by
bone, is the hard palate
• The unsupported
posterior part is the soft
Paranasal sinuses
• It is located in the frontal, sphenoid,
ethmoid and maxillary bones
• They produce mucus, which drains into the
nasal cavities
• It is a muscular
passageway about 13 cm
• Commonly called the
throat, the pharynx
serves as a common
passageway for food and
• Air enters the superior
portion, the
nasopharynx, from the
nasal cavity anteriorly
and then descends
through the oropharynx
and laryngopharynx to
enter the larynx below
• Clusters of lymphatic tissue
called tonsils are also found
in the pharynx:
- The pharyngeal tonsils,
often called adenoids, are
located high in the
- The palatine tonsils are in
the oropharynx at the end
of the soft palate
- The lingual tonsils are at
the base of the tongue
• The larynx, or voice box,
routes air and food into
the proper channels
and plays a role in
• Located inferior to the
pharynx, it is formed by
8 rigid hyaline cartilages
and a spoon shaped
flap of elastic cartilage,
the epiglottis
• The epiglottis protects the
superior opening of the
- When we are not swallowing,
the epiglottis does not
restrict the passage of air into
the lower respiratory
- When we swallow food or
fluids, the larynx is pulled
upward and the epiglottis
tips, forming a lid over the
opening of the larynx
Vocal Cords
• Part of the mucous
membrane of the
larynx forms a pair of
folds, called the
vocal folds, or true
vocal cords, which
vibrate with expelled
• Air entering the trachea,
or windpipe from the
larynx travels down its
length to the level of the
fifth thoracic vertebra,
which is approximately
• The trachea is lined with
ciliated mucosa: they
propel mucus away from
the lungs to the throat
where it can be
swallowed or spat out
Primary Bronchi
• The right and left primary
bronchi are formed by
the division of the
• The right primary
bronchus, which is wider,
shorter, and straighter
than the left, is the more
common site for an
inhaled foreign object to
become lodged
• The paired lungs are fairly
large organs
• The narrow superior
portion of each lung, the
apex, is located just deep to
the clavicle
• The broad lung area resting
on the diaphragm is the
• Each lung is divided into
lobes, the left lung has two
lobes and the right lung has
• The surface of each lung is covered with a
visceral membrane called the pulmonary
pleura, and the wall of the thoracic cavity are
lined by the parietal pleura
• The parietal pleura produces a slippery
secretion, plural fluid, which allows the lungs to
glide easily over the thorax wall during
• After the primary
bronchi enter the
lungs, they subdivide
into smaller and
smaller branches,
finally ending in the
smallest of the
passageways, the
• It is the only site of gas
• There are millions of
the clustered alveoli,
which resemble
bunches of grapes, and
they make you the bulk
of the lungs
The respiratory Membrane
• The walls of the alveoli are composed largely of a single, thin
layer of squamous epithelial cells
• The external surfaces of the alveoli are covered with a web of
pulmonary capillaries
• The gas exchanges occur by simple diffusion through the
respiratory membrane