Chapter 23
The Respiratory
System
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Upper respiratory tract
Lower respiratory tract
Respiratory System Anatomy
Structurally, the respiratory system is
divided into upper and lower divisions or
tracts.
The upper respiratory tract
consists of the nose, pharynx
and associated structures.
The lower respiratory tract
consists of the larynx,
trachea, bronchi and
lungs.
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Respiratory System Anatomy
Functionally, the respiratory system is
divided into the conducting zone and the
respiratory zone.
The conducting zone is involved with
bringing air to the site of external
respiration and consists of the nose,
pharynx, larynx, trachea, bronchi,
bronchioles and terminal
bronchioles.
The respiratory zone is the main site of
gas exchange and consists of the
respiratory bronchioles, alveolar
ducts, alveolar sacs, and alveoli.
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Air passing through the respiratory
tract traverses the:
Nasal cavity
Pharynx
Larynx
Trachea
Primary (1o) bronchi
Secondary (2o) bronchi
Tertiary (3o) bronchi
Bronchioles
Alveoli (150 million/lung)
Respiratory System Anatomy
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The external nose is
visible on the face.
It consists of:
a supporting bony
frame- work (frontal
bone, nasal bones,
and maxillae) and a
cartilaginous
framework of hyaline
cartilage
The Nose
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The Nasal cavity
Lies in and posterior to the
external nose
Is divided by a midline
nasal septum
Formed by the
perpedicular plate of
ethmoid, & the vomer
posteriorly and the septal
cartilage anteriorly
It opens posteriorly into the
naso- pharynx
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Three nasal conchae (or
turbinates) protrude medially
from each lateral wall of nasal
cavity
Superior concha
Middle concha
Inferior concha
Increase mucosal surface area & air
turbulence- ensures air contacts
mucosa
Under each nasal concha is an
opening, or meatus, for a duct that
drains secretions of the sinuses and
tears into the nose.
Nasal Cavity- lateral wall
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The Nose
Functions:
Providing an airway for respiration
Moistening and warming & filtering inspired
air
Resonation of sound
Olfaction
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The Paranasal Sinuses• Mucosa-lined, air-filled spaces found in
five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones • Sinuses lighten the skull and help to
warm and moisten the air
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The Paranasal Sinuses
Mucosal secretions flows from the sinuses into nasal cavity
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The Phrynx
The pharynx is a hollow tube that starts
posterior to the internal nares and descends
to the opening of the larynx in the neck.
It is formed by a complex arrangement of
skeletal muscles that assist in deglutition.
It functions as:
o a passageway for air and food
o a resonating chamber
o a housing for the tonsils
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The Pharynx
Nasopharynx
Oropharynx
Laryngopharynx
The pharynx has 3 regions The nasopharynx is separated
from the oropharynx by the hard and soft palate
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Lies posterior to the nasal cavity and superior to the level of the soft palateStrictly an air passageLined with psuedostratified columnar epitheliumCloses during swallowing to prevent food from entering the nasal cavityThe pharyngeal tonsil ( adenoids) lies high on the posterior wall Auditory tubes from middle ears open into the lateral walls
The Nasopharynx
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Cilia in the upper respiratory tract move
mucous and trapped particles down toward the
pharynx.
(Cilia in the lower respiratory tract move them
up toward the larynx.)
Respiratory Lining
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The PharynxThe oropharynx & laryngopharynx are both
common passages for food and air & are lined by
stratified squamous epithelium
The oropharynx lies posterior to the oral cavity
&
opens into the oral cavity via the fauces
The palatine tonsils lie in the lateral walls of the
fauces (those usually taken in a tonsillectomy)
and small lingual tonsil at the base of the
tongue
The laryngopharynx lies posterior to the upright
epiglottis
Leads into the larynx & the esophagus
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The Pharynx
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The Larynx
The larynx, composed of 9 pieces of cartilage,
forms a short passageway connecting the
laryngopharynx with the trachea (the
“windpipe”).
The thyroid cartilage (the large
“Adam’s apple”) and the one below
it (the cricoid cartilage) are
landmarks for making an
emergency airway (called a
cricothyrotomy).Anterior view of the larynx
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The Larynx
9 Cartilages of the larynx
Epiglottis – elastic cartilage that covers the
glottis during swallowing
Thyroid cartilage- hyaline cartilage with a
midline laryngeal prominence (Adam’s apple)
Cricoid cartilage - hyaline cartilage
Three pairs of small arytenoid, corniculate, &
cuneiform cartilages
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The epiglottis is a flap of elastic cartilage
covered with a mucus membrane, attached to
the root of the tongue.
The epiglottis guards the entrance of the
glottis, the opening between the vocal folds.
o For breathing, it is held
anteriorly, then pulled back-
ward to close off the glottic
opening during
swallowing.
The Larynx
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The Larynx
The mucous membrane of the larynx forms two
pairs of folds:
The superior pair are the Ventricular folds ( false
vocal cords) -also called vestibular folds
The space between the ventricular folds is the
rima vestibuli
The inferior pair are the vocal folds ( true vocal
cords)
The space between the vocal folds ( true vocal
cords) is the rima glottidis
True vocal cords & the opening between them form the
glottis
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The Larynx
The functions of the larynx are:
To provide an airway
To route air and food into the proper channels
To function in voice production- True vocal cords
vibrate to produce sound as air passes
False vocal cords have no part in sound production;
help close glottis during swallowing
Valsalva’s maneuver- by closing the glottis the
larynx is closed during certain abdominal
straining conditions to prevent exhalation
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Upper respiratory tract
Lower respiratory tract
Lower Respiratory Tract
As air passes from the laryngopharynx into the
larynx, it leaves the upper respiratory tract
and enters the lower respiratory tract.
Air passing through the
respiratory tract
Nasal cavity
Pharynx
Larynx
Trachea
Primary bronchi
Secondary bronchi
Tertiary bronchi
Bronchioles
Alveoli (150
million/lung)
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The Trachea
The trachea is a semi-rigid pipe made of semi-
circular cartilaginous rings, and located
anterior to the esophagus.
It is about 12 cm long and extends inferior to
larynx into the mediastinum
At the level of carina ( an internal ridge of last
tracheal cartiage) it divides into right and left
primary (1o, “mainstem”) bronchi.
It is composed of 4 layers: the mucosa ( lined
by ciliated respiratory epithelium),
submucosa, hyaline cartilage, and
adventitia
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The tracheal cartilage rings are incomplete
posteriorly, facing the esophagus.
Esophageal masses can press into this soft
part of the trachea and make it difficult
to breath, or even
totally obstruct
the airway.
The Trachea
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The Bronchi
The right and left primary (1o or “mainstem”)
bronchi emerge from the inferior trachea to go
to the lungs
Right primary bronchus is more vertical
compared to left primary bronchus
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The BronchiPrimary bronchi- subdivide into:Secondary bronchi (lobar bronchi), each supplying a lobe of the lungs –two on the left side and three on the right
Subdivide into tertiary bronchi (segmental bronchi)- each supplies one bronchopulmonary segmentThere are upto 10 bronchopulmonary segments in each lung
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Air passages undergo 23 orders of branchingsBronchioles- smaller than 1mm in diameter- lack cartilageBronchioles divide into terminal bronchioles
A branch of the terminal bronchioles supplies air to a lobule
Terminal bronchioles branch into respiratory bronchioles which now have alveoliRespiratory bronchioles lead to the alveolar ducts which have alveoli
The respiratory bronchioles, alveolar ducts and alveoli form the 'respiratory zone'
Bronchioles
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Pulmonary
lobule:
Wrapped in
elastic
C.T., each
pulmonary
lobule contains a
lymphatic vessel,
an
arteriole, a
venule
and a branch of
terminal
bronchiole.
Lung lobule
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The bronchi and bronchioles go through
structural changes as they branch and become
smaller.
The mucous membrane changes
The cartilaginous rings become more sparse,
and eventually disappear altogether.
As cartilage decreases, smooth muscle
(under the control of the Autonomic Nervous
System) increases.
o Sympathetic stimulation causes airway
dilation, while parasympathetic
stimulation causes airway constriction.
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All the branches from the trachea to the
terminal bronchioles are conducting
airways – they do not
participate in gas
exchange.
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Alveoli
Alveoli are the cup-
shaped outpouchings
which participate in gas
exchange
Alveoli make up a large
surface area (750
ft2).
They are lined chiefly by
type I alveolar cells,
simple squamous
epithelium)which allow
for exchange of gases with
the pulmonary capillaries.
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Alveoli
Type II cells in the alveoli
secrete a
substance called surfactant
that prevents collapse of the
alveoli
Alveoli macrophages (also
called “dust cells”) engulf and
remove pathogens & debris
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Respiratory MembraneThe Respiratory membrane across which diffusion of gases occurs is composed of:
Alveolar lining epitheliumCapillary endotheliumTheir fused basement membranes
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Blood Supply to the Lungs
The lungs receive blood via two sets of
arteries
Pulmonary arteries carry deoxygenated
blood from the right heart to the lungs for
oxygenation
Bronchial arteries branch from the aorta
and deliver oxygenated blood to the lungs
primarily perfusing the muscular walls of
the bronchi and bronchioles ( not the
alveoli)
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The lungs are divided into lobes by fissures.
The right lung is divided by the oblique
fissure and the horizontal fissure into 3
lobes .
The left lung is divided into
2 lobes by the oblique fissure.
Each lobe receives it own 2o
bronchus that branches into
3o segmental bronchi (which
continue to further divide).
The Lungs
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The apex of the lung is superior, and extends
slightly above the clavicles. The base of the
lungs rests on the diaphragm.
The cardiac notch –
in the left lung (the
indentation for the
heart)
• The medial mediastinal surface
has the hilus –
an indentation
Respiratory System Anatomy
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The lungs are separated from each other by
the heart and other structures in the
mediastinum.
Each lung is enclosed by a double-layered
pleural membrane.
The parietal pleura line the
walls of the thoracic cavity.
The visceral pleura adhere
tightly to the surface of
the lungs themselves.
Respiratory System Anatomy
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Respiratory System Anatomy
On each side of the thorax, a pleural cavity is
formed.
The pleural cavity contains pleural fluid -
reduces friction
The pleura, adherent to the chest wall and to
the lung, produces a mechanical coupling for
the two layers to move together.
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