CHAPTER 23
The Respiratory System
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Breathing and Respiration
 Respiration is the exchange of gases
between the atmosphere, blood, and cells
 The combination of 3 processes is
required for respiration to occur
 Ventilation (breathing)
 External (pulmonary) respiration
 Internal (tissue) respiration
 The cardiovascular system assists the
respiratory system by transporting gases
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Structures of the Respiratory System
Structurally, the components of the
respiratory system are divided into 2 parts:
1. Upper respiratory system
2. Lower respiratory system
Functionally, the components of the
respiratory system are divided into 2 zones:
1. Conducting zone
2. Respiratory zone
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Structures of the Respiratory System
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Respiratory System Anatomy
 The upper respiratory system consists of
the nose, pharynx, and associated
structures
 The lower respiratory system consists of
the larynx, trachea, bronchi, and lungs
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Overview: Nose, Pharynx, Larynx, and
Trachea
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Cartilaginous Framework of the Nose
The external
portion of the
nose is made of
cartilage and
skin and is lined
with mucous
membrane
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Internal Anatomy of the Nose
The bony framework of the nose is formed
by the frontal, nasal, and maxillary bones
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Nose
The nose is the only part of the respiratory system that is visible
externally and is the route for air entry into the respiratory system.
Air is drawn in via the nostrils or external nares and enters the large
nasal cavity, which is divided into two by the nasal septum.
The nasal cavity is partitioned from the oral cavity directly below it by
the palate.
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Nose
Like the rest of the respiratory tract, the nose is lined with mucosal
epithelium (stratified squamous and pseudostratified ciliated columnar)
It also contains glands that secrete a thick, sticky mucus that helps to
moisten the tract.
Just below the surface of the epithelium is a rich network of blood
vessels that warm the nasal cavities.
Nosebleeds are fairly common because the blood vessels are so
superficial.
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Nose
The nerve endings responsible for smell (olfaction) are found in the
nasal mucosa at the back of the nasal cavities.
Any obstruction of the nasal passages and surrounding sinuses, for
example caused by oedema of the tissues produced by the common
cold, will affect these nerve endings.
Typically the symptoms of an upper respiratory tract infection, or ‘head
cold’ involve the airways above the trachea.
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Paranasal sinuses
Four cavities - the paranasal sinuses - surround and drain into the nasal cavity.
Their mucosal lining is continuous with that of the nose and this means that
sinus infections (sinusitis) are common during a cold when the nasal mucosa is
inflamed.
The hollow sinuses
•
help lighten the skull
•
act as a resonating chamber for sounds,
•
help to produce mucus for the respiratory tract.
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Nasal Conchae and Meatuses
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Nasal Conchae
Three shell-like structures, the conchae or turbinates, protrude into each side of the nasal
cavity and increase the surface area over which air flows on its way to the lungs
As air is drawn in, the turbinates cause it to swirl around within the nasal cavity and this is
useful in a number of ways:
-
It allows extra time for the incoming air to be warmed and humidified,
-
The swirling action forces the air into frequent contact with the nasal mucosa and
large foreign particles become trapped;
-
The eddy currents that are created then carry olfactory stimuli to the olfactory
receptors in the nose, allowing us to smell.
-
Warmed, humidified air passes from the nasal cavities through the internal nares into
the pharynx, a structure shared by the respiratory and digestive systems.
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Pharynx
The pharynx functions as a passageway for
air and food, provides a resonating chamber
for speech sounds, and houses the tonsils,
which participate in immunological reactions
against foreign invaders
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Pharynx
The mucosal epithelium (stratified squamous) in the oropharynx is thicker than
elsewhere in the respiratory tract as it has to protect the tissues from any
abrasive and chemical trauma caused by food.
Two eustachian or auditory tubes connect the middle ears with the
nasopharynx and allow pressure in the middle and outer ear to equalise. The
mucosal lining of the nasopharynx, eustachian tubes and middle ear is
continuous and middle ear infections can occur when the nasopharynx is
inflamed.
The oropharynx can be entered from the mouth as well as from the
nasopharynx, while the lower portion, the laryngopharynx, divides into the
oesophagus which carries food to the stomach and the larynx through which
air passes to the lungs.
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Tonsils
Masses of lymphoid tissue that act as a line of defense
Adenoids – single tonsil located posteriorly in the nasopharynx
Palatine tonsils – paired; located posteriorly in the orophayrnx
Lingual tonsils – pair of tonsils under the tongue
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Larynx
The larynx (voice box) is a
passageway that connects the
pharynx and trachea
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Larynx
The larynx contains vocal folds, which produce sound when they
vibrate. Pseusdostratified ciliated columnar epithelium
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Trachea
The trachea extends from the larynx to the primary bronchi, 16 – 20 Cshaped rings of cartilage keep it open. Lined by pseusdostratified
ciliated columnar epithelium
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Bronchi
At the superior border of the 5th thoracic vertebrae,
the trachea branches into a right primary bronchus
which enters the right lung and a left primary
bronchus which enters the left lung
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Bronchi
Upon entering the lungs,
the primary bronchi
further divide to form
smaller and smaller
diameter branches
 The terminal bronchioles
are the end of the
conducting zone
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Lungs
The lungs are paired organs in the thoracic
cavity
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Lungs
The lungs are enclosed and protected by the
pleural membrane
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Lobes and Fissures of the Lungs
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Alveoli
 When the conducting zone
ends at the terminal
bronchioles where the
epithelium has changed
gradually from
psuedostratifed ciliated
columnar epithelium to simple
cuboidal epthelium.
 The terminal brochioles end in
the respiratory brochioles,
which are lined by simple
squamous epithelium, and the
respiratory zone begins
 The respiratory zone
terminates at the alveoli, the
“air sacs” found within the
lungs
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Alveoli in a Lobule of a Lung
Alveoli are sac-like structures
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Alveolus
There are 2 kinds of alveolar cells, Type I
and Type II
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Respiratory Membrane
The respiratory membrane is composed of:
1. A layer of type I and type II alveolar cells and
associated alveolar macrophages that
constitutes the alveolar wall
2. The capillary endothelium
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Blood Supply to the Lungs
 Blood enters the lungs via the pulmonary
arteries (pulmonary circulation) and the
bronchial arteries (systemic circulation)
 Blood exits the lungs via the pulmonary
veins and the bronchial veins
 Ventilation-perfusion coupling
 Vasoconstriction in response to hypoxia diverts
blood from poorly ventilated areas to well
ventilated areas
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Pulmonary Ventilation
In pulmonary ventilation, air flows between
the atmosphere and the alveoli of the lungs
because of alternating pressure differences
created by contraction and relaxation of
respiratory muscles
 Inhalation
 Exhalation
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.