Anatomy of the respiratory system...

Chapter 22, Respiratory System 1
The Respiratory System

Respiratory System
Figure 22.1

Copyright 2009, John Wiley & Sons, Inc.
Respiratory System Anatomy
 Structurally
 Upper respiratory system
Nose, pharynx and associated structures
 Lower respiratory system
Larynx, trachea, bronchi and lungs

Respiratory System
 Functionally
 Consists of the respiratory and conducting zones
 Respiratory zone
 Site of gas exchange
 Consists of bronchioles, alveolar ducts, and alveoli

Respiratory System
 Conducting zone
 Provides rigid structures for air to reach the sites of
gas exchange
 Includes all other respiratory structures (e.g., nose,
nasal cavity, pharynx, trachea)

 Respiratory muscles – diaphragm and other muscles
that promote ventilation

Structure of the Nose
Figure 22.2a

 The nose is divided into two regions
 The external nose
 The internal nasal cavity

 The external nose, including the root, bridge, dorsum
nasi, and apex
 Philtrum – a shallow vertical groove inferior to the
apex
 The external nares (nostrils) are bounded laterally by
the alae

Figure 22.2b

Nasal Cavity
 Lies in and posterior to the external nose
 Is divided by a midline nasal septum
 Opens posteriorly into the nasal pharynx via internal
nares
 The ethmoid and sphenoid bones form the roof
 The floor is formed by the hard and soft palates

Nasal Cavity
 Vestibule – nasal cavity superior to the nares
 Vibrissae – hairs that filter coarse particles from
inspired air
 Olfactory mucosa
 Lines the superior nasal cavity
 Contains smell receptors

Nasal Cavity
 Respiratory mucosa
 Lines the balance of the nasal cavity
 Glands secrete mucus containing lysozyme and
defensins to help destroy bacteria

Nasal Cavity
Figure 22.3b

Nasal Cavity
 Inspired air is:
 Humidified by the high water content in the nasal
cavity
 Warmed by rich plexuses of capillaries
 Ciliated mucosal cells remove contaminated mucus

Nasal Cavity
 Superior, medial, and inferior conchae:
 Protrude medially from the lateral walls
 Increase mucosal area
 Enhance air turbulence and help filter air
 Sensitive mucosa triggers sneezing when stimulated
by irritating particles

Function of the Nose
 The only externally visible part of the respiratory
system that functions by:
 Providing an airway for respiration
 Moistening (humidifying) and warming the
entering air
 Filtering inspired air and cleaning it of foreign
matter
 Serving as a resonating chamber for speech
 Housing the olfactory receptors

Functions of the Nasal Mucosa and Conchae
 During inhalation the conchae and nasal mucosa:
 Filter, heat, and moisten air
 During exhalation these structures:
 Reclaim heat and moisture
 Minimize heat and moisture loss

Paranasal Sinuses
 Sinuses in bones that surround the nasal cavity
 Sinuses lighten the skull and help to warm and
moisten the air

Pharynx
 Funnel-shaped tube of skeletal muscle that connects
to the:
 Nasal cavity and mouth superiorly
 Larynx and esophagus inferiorly
 Extends from the base of the skull to the level of the
sixth cervical vertebra

Pharynx
 It is divided into three regions
 Nasopharynx
 Oropharynx
 Laryngopharynx

Nasopharynx
 Lies posterior to the nasal cavity, inferior to the
sphenoid, and superior to the level of the soft palate
 Strictly an air passageway
 Lined with pseudostratified columnar epithelium
 Closes during swallowing to prevent food from
entering the nasal cavity
 The pharyngeal tonsil lies high on the posterior wall
 Pharyngotympanic (auditory) tubes open into the
lateral walls

Oropharynx
 Extends inferiorly from the level of the soft palate to
the epiglottis
 Serves as a common passageway for food and air
 The epithelial lining is protective stratified
squamous epithelium
 Palatine tonsils lie in the lateral walls
 Lingual tonsil covers the base of the tongue

Laryngopharynx
 Serves as a common passageway for food and air
 Lies posterior to the upright epiglottis
 Extends to the larynx, where the respiratory and
digestive pathways diverge

Larynx

Larynx
 Short passageway connecting
laryngopharynx with trachea
 Composed of 9 pieces of cartilage
Thyroid cartilage or Adam’s apple
Cricoid cartilage hallmark for
tracheotomy

 Epiglottis closes off glottis during swallowing
 Glottis – pair of folds of mucous membranes,
vocal folds (true vocal cords, and rima
glottidis (space)
 Cilia in upper respiratory tract move mucous
and trapped particles down toward pharynx
 Cilia in lower respiratory tract move them up
toward pharynx

Larynx (Voice Box)
 Attaches to the hyoid bone and opens into the
laryngopharynx superiorly
 Continuous with the trachea posteriorly

Framework of the Larynx
Figure 22.4a, b

Structures of Voice Production
 Mucous membrane of larynx forms
 Ventricular folds (false vocal cords) – superior pair
 Function in holding breath against pressure in
thoracic cavity
 Vocal folds (true vocal cords) – inferior pair
 Muscle contraction pulls elastic ligaments which
stretch vocal folds out into airway
 Vibrate and produce sound with air
 Folds can move apart or together, elongate or
shorten, tighter or looser

 Androgens make folds thicker and longer – slower vibration and
lower pitch

Movements of Vocal Cords
Figure 22.5

Framework of the Larynx
 Cartilages (hyaline) of the larynx
 Shield-shaped anterosuperior thyroid cartilage with
a midline laryngeal prominence (Adam’s apple)
 Signet ring–shaped anteroinferior cricoid cartilage
 Three pairs of small arytenoid, cuneiform, and
corniculate cartilages
 Epiglottis – elastic cartilage that covers the laryngeal
inlet during swallowing

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

Vocal Ligaments
 False vocal cords
 Mucosal folds superior to the true vocal cords
 Have no part in sound production

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

Movements of Vocal Cords
Figure 22.5

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

Functions
 The three functions of the larynx are:
 To provide a patent airway
 To act as a switching mechanism to route air and
food into the proper channels
 To function in voice production

Trachea
 Flexible and mobile tube extending from the larynx
into the mediastinum
 Extends from larynx to superior border of T5
 Divides into right and left primary bronchi

Trachea
 4 layers
 Mucosa
 Submucosa
 Hyaline cartilage
 Adventitia

Layers
 Mucosa – made up of goblet cells and ciliated
epithelium
 Submucosa – connective tissue deep to the mucosa
 Hyaline cartilage -16-20 C-shaped rings of hyaline
cartilage
 Open part faces esophagus
 Adventitia – outermost layer

Trachea
Figure 22.6a

Location of Trachea

The Trachea or Windpipe (cont’d.)
 Supporting cartilage: stack of Cs
 Cough reflex stimulated by foreign object
 Tracheostomy done if object cannot be expelled
 Usually done between second and third tracheal
cartilages
 Can be closed when object removed

Bronchi
 Right and left primary bronchus goes to right
and left lungs
 Carina – internal ridge
Most sensitive area for triggering cough
reflex
 Divide to form bronchial tree
Secondary lobar bronchi (one for each
lobe), tertiary (segmental) bronchi,
bronchioles, terminal bronchioles

Structural changes with branching
Mucous membrane changes
Incomplete rings become plates and then
disappear
As cartilage decreases, smooth muscle
increases
Sympathetic ANS – relaxation/ dilation
Parasympathetic ANS – contraction/
constriction

Bronchi
 The carina of the last tracheal cartilage marks the
end of the trachea and the beginning of the right and
left bronchi
 Bronchi subdivide into secondary bronchi, each
supplying a lobe of the lungs
 Air passages undergo 23 orders of branching in the
lungs

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

Bronchioles
 Consist of cuboidal epithelium
 Have a complete layer of circular smooth muscle
 Lack cartilage support and mucus-producing cells

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

Pleura
 Each lung enclosed by double-layered pleural
membrane
 Parietal pleura – lines wall of thoracic cavity
 Visceral pleura – covers lungs themselves
 Pleural cavity is space between layers
 Pleural fluid reduces friction, produces surface
tension (stick together)

Pleurae
 Thin, double-layered serosa
 Parietal pleura
 Covers the thoracic wall and superior face of the
diaphragm
 Continues around heart and between lungs

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

Relationship of the Pleural Membranes
to Lungs

Lungs
 Separated from each other by the heart and other
structures in the mediastinum
 Cardiac notch – heart makes left lung 10% smaller than
right

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

Gross Anatomy of Lungs
 Base, apex (cupula), costal surface, cardiac notch
 Oblique & horizontal fissure in right lung results in 3 lobes
 Oblique fissure only in left lung produces 2 lobes

Mediastinal Surface of Lungs
 Blood vessels & airways enter lungs at hilus
 Forms root of lungs
 Covered with pleura (parietal becomes visceral)

Anatomy of Lungs
 Lobes – each lung divides by 1 or 2 fissures
 Each lobe receives it own secondary (lobar) bronchus that branch
into tertiary (segmental) bronchi
 Lobules wrapped in elastic connective tissue and contains a
lymphatic vessel, arteriole, venule and branch from terminal
bronchiole
 Terminal bronchioles branch into respiratory bronchioles
which divide into alveolar ducts
 About 25 orders of branching

Microscopic Anatomy of Lobule of
Lungs

Respiratory Zone
 Begins as terminal bronchioles feed into respiratory
bronchioles and then to alveoli
 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

Alveoli
 Cup-shaped outpouching
 Alveolar sac – 2 or more alveoli sharing a common
opening

Alveolar cells
 2 types of alveolar epithelial cells
Type I alveolar cells –
 Form nearly continuous lining,
 More numerous than type II,
 Main site of gas exchange
Type II alveolar cells (septal cells) –
 Free surfaces contain microvilli,
 Secrete alveolar fluid
 Surfactant reduces tendency to collapseChapter 22, Respiratory System 67

Respiratory Zone
Figure 22.8a

Respiratory Zone
Figure 22.8b

Alveolus
 Respiratory membrane
 Alveolar wall – type I and type II alveolar cells
 Epithelial basement membrane
 Capillary basement membrane
 Capillary endothelium
 Very thin – only 0.5 µm thick to allow rapid diffusion of gases

Components of Alveolus

Respiratory Membrane
Figure 22.9.c, d

 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)

Figure 22.9b

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

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

Figure 22.24
Control of Respiration:
Medullary Respiratory Centers

 Pons centers:
 Influence and modify activity of the medullary
centers
 Smooth out inspiration and expiration transitions
and vice versa
Control of Respiration:
Pons Respiratory Centers

Pulmonary Function Tests
 Spirometer – an instrument used to evaluate
respiratory function

 Total ventilation – total amount of gas flow into or
out of the respiratory tract in one minute
 Forced vital capacity (FVC) – gas forcibly expelled
after taking a deep breath
 Forced expiratory volume (FEV) – the amount of
gas expelled during specific time intervals of the
FVC

 Increases in TLC, FRC, and RV may occur as a
result of obstructive disease
 Reduction in VC, TLC, FRC, and RV result from
restrictive disease

 Hyperventilation – increased depth and rate of
breathing that:
 Quickly flushes carbon dioxide from the blood
 Occurs in response to hypercapnia
Depth and Rate of Breathing: PCO2

 Hypoventilation – slow and shallow breathing due to
abnormally low PCO2 levels
 Apnea (breathing cessation) may occur until PCO2
levels rise
Depth and Rate of Breathing: PCO2

Applied
anatomy

Pneumothorax
 Pleural cavities are sealed
cavities not open to the
outside
 Injuries to the chest wall
that let air enter the
intrapleural space
 causes a pneumothorax
 collapsed lung on same
side as injury

 Exemplified by chronic bronchitis
 Patients have a history of:
 Smoking
 Dyspnea
 Coughing and frequent pulmonary infections
Chronic Obstructive Pulmonary Disease
(COPD)

Chronic Obstructive Pulmonary Disease

 Characterized by dyspnea, wheezing, and chest
tightness
 Active inflammation of the airways precedes
bronchospasms
 Airways thickened with inflammatory exudates
magnify the effect of bronchospasms
Asthma

 Infectious disease caused by the bacterium
Mycobacterium tuberculosis
 Symptoms include fever, night sweats, weight loss, a
racking cough, and splitting headache
 Treatment entails a 12-month course of antibiotics
Tuberculosis

 90% of all patients with lung cancer were smokers
Lung Cancer

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