PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky
O Sistema Respiratório
Parte A
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
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22
Sistema Respiratório
 Consiste de zonas condutoras e respiratórias
 Zona respiratória
 Regiões onde há troca gasosa
 Consiste de bronquíolos, ductos alveolares e
alvéolos
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Sistema Respiratório
 Zona condutora
 Condutos rígidos que permite que o ar chege às
zonas de troca gasosa
 Incluem todas as outras estruturas respiratórias
(Nariz, cavidade nasal, faringe, traquéia, etc)
 Músculos respiratórios – diafragma e outros
músculos que promovem a ventilação
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Sistema Respiratório
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Figure 22.1
Principais funções do sistema respiratório
 Oferta de O2 e eliminação do CO2
 Respiração – quatro processos necessários
 Ventilação pulmonar – movimento de ar para
dentro e for a dos pulmões
 Respiração externa – troca gasosa entre os pulmões
e o sangue
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Principais funções do sistema respiratório
 Transporte – transporte de oxigênio e gás carbônico
entre os pulmões e tecidos
 Respiração interna – trocas gasosas entre o sangue e
os tecidos
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Funções do nariz
 A única parte visível do sistema respiratório, e
funciona para:
 Permitir passagem do ar
 Misturar e aquecer o ar
 Filtrar e limpar o ar inspirado
 Servir como caixa de ressonância para a fala
 Função olfatória
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Estrutura do nariz
 Dividido em duas regiões
 Nariz externo, incluindo raiz, ponte, dorso nasal e
ápice
 Cavidade nasal interna
 Filtro – sulco raso vertical
 Narina externas limitadas lateralmente pelas asas do
nariz
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Estruturas do nariz
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Figure 22.2a
Estruturas do nariz
Figure 22.2b
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Cavidade nasal
 Situada posteriormente ao nariz
 Dividida ao meio pelo septo nasal
 Abre-se posteriormente na faringe
 Os ossos etmóide e esfenóide formam o teto
 O pálato mole e duro formam o assoalho
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Cavidade nasal
 Vestíbulo – cavidade nasal superiormente ao nariz
 Pelos – filtram partículas do ar inspirado
 Mucosa olfatória
 Localizados na cavidade nasal superior
 Contém receptores para o cheiro
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Cavidade nasal
 Mucosa respiratória
 Recobre a cavidade nasal
 Possui glândulas que secretam muco contendo
lisosimas e defensinas que destroem bactérias
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Cavidade nasal
Figure 22.3b
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Cavidade nasal
 O ar inspirado é:
 Umidificado pelo vapor de água na cavidade nasal
 Aquecido pelo sangue do rico plexo capilar nasal
 Células mucosas ciliadas removem o muco
contaminado
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Cavidade nasal
 Conchas superior, média e inferior:
 Protusões mediais a partir das paredes laterais
 Aumentam a área de superfície da mucosa
 Produzem turbulência do ar, e auxiliam na filtragem
do ar
 A mucosa sensitiva desencadeia o espirro quando
estimulada por partículas irritantes
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Funções da mucosa nasal e das conchas
 Durante a inalação as conchas e a mucosa
 Filtram, aquecem e umidificam o ar
 Durante a expiração:
 Retêm calor e umidade
 Minimizam perda de calor e água
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Seios para-nasais
 Seios nos ossos que circundam a cavidade nasal
 Auxiliam a aquecer e umidificar o ar
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Faringe
 Tubo muscular esquelético, em forma de funil, que
conecta:
 Com a cavidade nasal com a boca superiormente
 Com a laringe e esôfago inferiormente
 Se extende da base do crânio até o nível da sexta
vértebra cervical
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Faringe
 Dividida em três regiões:
 Nasofaringe
 Orofaringe
 Laringofaringe
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Nasofaringe
 Situada posteriormente à cavidade nasal,
inferiormente ao esfenóide, e superiormente ao
pálato mole
 Funciona apenas com passagem de ar
 Recoberta por epitélio colunar pseudo-estratificado
 Se fecha durante a deglutição para evitar refluxo de
alimento para a cavidade nasal
 Contêm amígdalas faringianas na parede posterior
 Contêm as aberturas das tubas auditivas nas paredes
laterais
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Orofaringe
 Se extende inferiormente do pálato mole até a
epiglote
 Abre-se para a cavidade oral por um arco chamado
de fauces
 Serve como via aérea e digestiva
 Recoberta por epitélio escamoso estratificado
 Contém amígdalas palatinas nas paredes laterais das
fauces
 Amígdalas linguais cobrem a base da língua
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Laringofaringe
 Serve como passagem para o ar e alimento
 Localizada posteriormente à epiglote
 Extende-se para a laringe, onde as vias respiratória e
digestiva divergem
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Laringe (Caixa vocal)
 Se liga no osso hióide e se abre na laringofaringe
superiormente
 Continua com a traqueia
 Há três funções:
 Passagem do ar
 Impede que o alimente penetre na traquéia
 Produção da voz
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Sustentação da laringe
 Cargilagem (hialina) da laringe
 Cartilagem tireóide anterior, com uma
proeminência mediana (Pomo de Adão)
 Cartilagem cricóide ântero-inferior
 Três pares de pequenas cargilagens, aritenóide,
cuneiforme e corniculadas
 Epiglote – cartilagem elástica que recobre a laringe
durante a deglutição
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Framework of the Larynx
Figure 22.4a, b
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Vocal Ligaments
 Attach the arytenoid cartilages to the thyroid
cartilage
 Composed of elastic fibers that form mucosal folds
called true vocal cords
 The medial opening between them is the glottis
 They vibrate to produce sound as air rushes up from
the lungs
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Vocal Ligaments
 False vocal cords
 Mucosal folds superior to the true vocal cords
 Have no part in sound production
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Vocal Production
 Speech – intermittent release of expired air while
opening and closing the glottis
 Pitch – determined by the length and tension of the
vocal cords
 Loudness – depends upon the force at which the air
rushes across the vocal cords
 The pharynx resonates, amplifies, and enhances
sound quality
 Sound is “shaped” into language by action of the
pharynx, tongue, soft palate, and lips
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Movements of Vocal Cords
Figure 22.5
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Sphincter Functions of the Larynx
 The larynx is closed during coughing, sneezing, and
Valsalva’s maneuver
 Valsalva’s maneuver
 Air is temporarily held in the lower respiratory tract
by closing the glottis
 Causes intra-abdominal pressure to rise when
abdominal muscles contract
 Helps to empty the rectum
 Acts as a splint to stabilize the trunk when lifting
heavy loads
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Trachea
 Flexible and mobile tube extending from the larynx
into the mediastinum
 Composed of three layers
 Mucosa – made up of goblet cells and ciliated
epithelium
 Submucosa – connective tissue deep to the mucosa
 Adventitia – outermost layer made of C-shaped
rings of hyaline cartilage
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Trachea
Figure 22.6a
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Conducting Zone: Bronchi
 The carina of the last tracheal cartilage marks the
end of the trachea and the beginning of the right and
left bronchi
 Air reaching the bronchi is:
 Warm and cleansed of impurities
 Saturated with water vapor
 Bronchi subdivide into secondary bronchi, each
supplying a lobe of the lungs
 Air passages undergo 23 orders of branching in the
lungs
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Conducting Zone: Bronchial Tree
 Tissue walls of bronchi mimic that of the trachea
 As conducting tubes become smaller, structural
changes occur
 Cartilage support structures change
 Epithelium types change
 Amount of smooth muscle increases
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Conducting Zone: Bronchial Tree
 Bronchioles
 Consist of cuboidal epithelium
 Have a complete layer of circular smooth muscle
 Lack cartilage support and mucus-producing cells
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Respiratory Zone
 Defined by the presence of alveoli; begins as
terminal bronchioles feed into respiratory
bronchioles
 Respiratory bronchioles lead to alveolar ducts, then
to terminal clusters of alveolar sacs composed of
alveoli
 Approximately 300 million alveoli:
 Account for most of the lungs’ volume
 Provide tremendous surface area for gas exchange
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Respiratory Zone
Figure 22.8a
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Respiratory Zone
Figure 22.8b
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Respiratory Membrane
 This air-blood barrier is composed of:
 Alveolar and capillary walls
 Their fused basal laminas
 Alveolar walls:
 Are a single layer of type I epithelial cells
 Permit gas exchange by simple diffusion
 Secrete angiotensin converting enzyme (ACE)
 Type II cells secrete surfactant
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Alveoli
 Surrounded by fine elastic fibers
 Contain open pores that:
 Connect adjacent alveoli
 Allow air pressure throughout the lung to be
equalized
 House macrophages that keep alveolar surfaces
sterile
PLAY
InterActive Physiology®:
Respiratory System: Anatomy Review: Respiratory Structures
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Respiratory Membrane
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Figure 22.9b
Respiratory Membrane
Figure 22.9.c, d
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Gross Anatomy of the Lungs
 Lungs occupy all of the thoracic cavity except the
mediastinum
 Root – site of vascular and bronchial attachments
 Costal surface – anterior, lateral, and posterior
surfaces in contact with the ribs
 Apex – narrow superior tip
 Base – inferior surface that rests on the diaphragm
 Hilus – indentation that contains pulmonary and
systemic blood vessels
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Lungs
 Cardiac notch (impression) – cavity that
accommodates the heart
 Left lung – separated into upper and lower lobes by
the oblique fissure
 Right lung – separated into three lobes by the
oblique and horizontal fissures
 There are 10 bronchopulmonary segments in each
lung
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Blood Supply to Lungs
 Lungs are perfused by two circulations: pulmonary
and bronchial
 Pulmonary arteries – supply systemic venous blood
to be oxygenated
 Branch profusely, along with bronchi
 Ultimately feed into the pulmonary capillary
network surrounding the alveoli
 Pulmonary veins – carry oxygenated blood from
respiratory zones to the heart
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Blood Supply to Lungs
 Bronchial arteries – provide systemic blood to the
lung tissue
 Arise from aorta and enter the lungs at the hilus
 Supply all lung tissue except the alveoli
 Bronchial veins anastomose with pulmonary veins
 Pulmonary veins carry most venous blood back to
the heart
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Pleurae
 Thin, double-layered serosa
 Parietal pleura
 Covers the thoracic wall and superior face of the
diaphragm
 Continues around heart and between lungs
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Pleurae
 Visceral, or pulmonary, pleura
 Covers the external lung surface
 Divides the thoracic cavity into three chambers
 The central mediastinum
 Two lateral compartments, each containing a
lung
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Breathing
 Breathing, or pulmonary ventilation, consists of two
phases
 Inspiration – air flows into the lungs
 Expiration – gases exit the lungs
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Pressure Relationships in the Thoracic Cavity
 Respiratory pressure is always described relative to
atmospheric pressure
 Atmospheric pressure (Patm)
 Pressure exerted by the air surrounding the body
 Negative respiratory pressure is less than Patm
 Positive respiratory pressure is greater than Patm
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Pressure Relationships in the Thoracic Cavity
 Intrapulmonary pressure (Ppul) – pressure within the
alveoli
 Intrapleural pressure (Pip) – pressure within the
pleural cavity
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Pressure Relationships
 Intrapulmonary pressure and intrapleural pressure
fluctuate with the phases of breathing
 Intrapulmonary pressure always eventually
equalizes itself with atmospheric pressure
 Intrapleural pressure is always less than
intrapulmonary pressure and atmospheric pressure
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Pressure Relationships
 Two forces act to pull the lungs away from the
thoracic wall, promoting lung collapse
 Elasticity of lungs causes them to assume smallest
possible size
 Surface tension of alveolar fluid draws alveoli to
their smallest possible size
 Opposing force – elasticity of the chest wall pulls
the thorax outward to enlarge the lungs
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Pressure Relationships
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Figure 22.12
Lung Collapse
 Caused by equalization of the intrapleural pressure
with the intrapulmonary pressure
 Transpulmonary pressure keeps the airways open
 Transpulmonary pressure – difference between the
intrapulmonary and intrapleural pressures
(Ppul – Pip)
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Pulmonary Ventilation
 A mechanical process that depends on volume
changes in the thoracic cavity
 Volume changes lead to pressure changes, which
lead to the flow of gases to equalize pressure
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Boyle’s Law
 Boyle’s law – the relationship between the pressure
and volume of gases
P 1 V1 = P 2 V2
 P = pressure of a gas in mm Hg
 V = volume of a gas in cubic millimeters
 Subscripts 1 and 2 represent the initial and resulting
conditions, respectively
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Inspiration
 The diaphragm and external intercostal muscles
(inspiratory muscles) contract and the rib cage rises
 The lungs are stretched and intrapulmonary volume
increases
 Intrapulmonary pressure drops below atmospheric
pressure (1 mm Hg)
 Air flows into the lungs, down its pressure gradient,
until intrapleural pressure = atmospheric pressure
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Inspiration
Figure 22.13.1
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Expiration
 Inspiratory muscles relax and the rib cage descends
due to gravity
 Thoracic cavity volume decreases
 Elastic lungs recoil passively and intrapulmonary
volume decreases
 Intrapulmonary pressure rises above atmospheric
pressure (+1 mm Hg)
 Gases flow out of the lungs down the pressure
gradient until intrapulmonary pressure is 0
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Expiration
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Figure 22.13.2
Physical Factors Influencing Ventilation:
Airway Resistance
 Friction is the major nonelastic source of resistance
to airflow
 The relationship between flow (F), pressure (P), and
resistance (R) is:
P
F=
R
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Physical Factors Influencing Ventilation:
Airway Resistance
 The amount of gas flowing into and out of the
alveoli is directly proportional to P, the pressure
gradient between the atmosphere and the alveoli
 Gas flow is inversely proportional to resistance with
the greatest resistance being in the medium-sized
bronchi
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Airway Resistance
 As airway resistance rises, breathing movements
become more strenuous
 Severely constricted or obstructed bronchioles:
 Can prevent life-sustaining ventilation
 Can occur during acute asthma attacks which stops
ventilation
 Epinephrine release via the sympathetic nervous
system dilates bronchioles and reduces air resistance
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Alveolar Surface Tension
 Surface tension – the attraction of liquid molecules
to one another at a liquid-gas interface
 The liquid coating the alveolar surface is always
acting to reduce the alveoli to the smallest possible
size
 Surfactant, a detergent-like complex, reduces
surface tension and helps keep the alveoli from
collapsing
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Lung Compliance
 The ease with which lungs can be expanded
 Specifically, the measure of the change in lung
volume that occurs with a given change in
transpulmonary pressure
 Determined by two main factors
 Distensibility of the lung tissue and surrounding
thoracic cage
 Surface tension of the alveoli
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Factors That Diminish Lung Compliance
 Scar tissue or fibrosis that reduces the natural
resilience of the lungs
 Blockage of the smaller respiratory passages with
mucus or fluid
 Reduced production of surfactant
 Decreased flexibility of the thoracic cage or its
decreased ability to expand
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Factors That Diminish Lung Compliance
 Examples include:
 Deformities of thorax
 Ossification of the costal cartilage
 Paralysis of intercostal muscles
PLAY
InterActive Physiology®:
Respiratory System: Pulmonary Ventilation
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