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Respiratory System
Dr. Michael P. Gillespie
Functions
 Gas exchange.
 Regulation of blood ph.
 Contains receptors for the sense of smell.
 Filters inspired air.
 Produces sounds.
 Rids the body of some water and heat in expired air.
Gas Exchange
 Cells use oxygen (O2) for metabolic reactions that release
energy from nutrient molecules and produce ATP.
 These reactions release carbon dioxide (CO2).
 The cardiovascular system and the respiratory system
cooperate to supple O2 and eliminate CO2.
Components
 Nose.
 Pharynx (throat).
 Larynx (voice box).
 Trachea (windpipe).
 Bronchi.
 Lungs.
Upper Respiratory System
 Nose.
 Pharynx.
 Associated structures.
Lower Respiratory System
 Larynx.
 Trachea.
 Bronchi.
 Lungs.
Functional Divisions
 Conducting portion.
 Interconnecting cavities and tubes both outside and within the
lungs that filter, warm, moisten air and conduct it into the
lungs.
 Nose, pharynx, larynx, trachea, bronchi, bronchioles, and
terminal bronchioles.
 Respiratory portion.
 Tissues within the lungs where gas exchange occurs.
 Respiratory bronchioles, alveolar ducts, alveolar sacs, and
alveoli.
Otorhinolaryngology
 Diagnosis and treatment of the ears, nose and throat.
Pulmonologist
 Diagnosis and treatment of disease of the lungs.
Nose
 External and internal portions.
External Nose
 Supporting framework of bone and hyaline cartilage covered
with muscle and skin and lined with a mucous membrane.
 Frontal bone, nasal bones, and maxillae form the bony
framework.
External Nose
 The cartilaginous framework consists of the septal
cartilage, lateral nasal cartilages, and alar cartilages.
External Nose
 The two openings are the external nares or nostrils.
 Functions:
 Warming, moistening, and filtering incoming air.
 Detecting olfactory stimuli.
 Modifying speech vibrations as they pass through large, hollow,
resonating chambers.
 Resonance refers to prolonging, amplifying, or modifying a sound by
vibration.
Internal Nose
 A large cavity in the anterior aspect of the skull.
 Lies inferior to the nasal bone and superior to the
mouth.
 The internal nares or choanae provide
communication between the external nose and the
pharynx.
 Ducts from the paranasal sinuses and the nasolacrimal
ducts also open into the internal nose.
Internal Nose
 Lateral walls: ethmoid, maxillae, lacrimal, palatine, and
inferior nasal conchae bones.
 Floor: the hard palate which consists of the palatine bones
and the palatine process of the maxillae.
Internal Nose
 Nasal cavity – the space within the internal nose.
 The anterior portion just inside the nostrils is called the
vestibule.
 The nasal septum divides the cavity into right and left
sides.
 Primarily hyaline cartilage, but also the vomer, and
perpendicular plate.
Air Filtration
 The vestibule is lined by skin containing coarse hairs,
which filter out large dust particles.
 Three shelves are formed by the superior, middle,
and inferior conchae.
 The conchae divide the nasal septum into groove like
passageways called the superior, middle, and
inferior meatuses.
 A mucous membrane lines the cavity and its shelves.
Air Filtration
 The arrangement of the conchae and meatuses increases
surface area in the internal nose. It traps water droplets
during exhalation to prevent dehydration.
 The olfactory receptors line the superior nasal conchae and
adjacent septum (olfactory epithelium).
Air Filtration
 Inspired air is warmed by blood in the capillaries.
 Mucous secreted by goblet cells moistens the air and traps
dust particles.
 Cilia move the mucous and trapped particles towards the
pharynx to be swallowed or spit out.
Rhinoplasty
 “Nose job”.
 The structure of the external nose is altered.
 Often performed for cosmetic reasons.
 Sometimes performed to repair a fractured nose or a
deviated septum.
Pharynx
 The pharynx or throat is a funnel shaped tube about 13 cm
long.
 It starts at the internal nares and extends to the cricoid
cartilage (the most inferior cartilage of the larynx).
Pharynx
 Its wall is composed of skeletal muscles and it is lined with a
mucous membrane.
Pharynx
 Functions:
 Passageway for air and food.
 Resonating chamber for speech sounds.
 Houses the tonsils (participate in immune responses).
 Anatomical regions:
 Nasopharynx.
 Oropharynx.
 Laryngopharynx.
Nasopharynx
 The nasopharynx is the superior portion of the pharynx.
 Extends from the posterior nasal cavity to the soft palate.
 5 openings in its wall:
 2 internal nares.
 Eustachian tubes (a.K.A. Auditory or pharyngotympanic).
 Opening into the oropharynx.
Nasopharynx
 Pharyngeal tonsils.
 The nasopharynx is lined with pseudostratified ciliated
columnar epithelium, which moves mucous down towards
the inferior part of the pharynx.
 The eustachian tubes help to equalize air pressure between
the pharynx and middle ear.
Oropharynx
 The intermediate portion of the pharynx.
 Extends from the soft palate to the hyoid bone.
 One opening – the fauces (throat), the opening from the
mouth.
 Common passageway for air, food, and drink.
 Lined with nonkeratinized stratified squamous epithelium to
withstand abrasion from food particles.
 Palatine and lingual tonsils are found here.
Laryngopharynx
 Inferior portion of the pharynx.
 Otherwise known as the hypopharynx.
 Opens to the esophagus posteriorly and the larynx anteriorly.
 Both a respiratory and a digestive pathway.
 Lined with nonkeratinzed stratified squamous epithelium.
Larynx
 Voice box.
 A short passageway that connects the laryngopharynx with
the trachea.
 Lies in the midline of the neck anterior to the 4th through 6th
cervical vertebrae.
Larynx
 Composed of 9 pieces of cartilage.
 Thyroid cartilage (Adam’s apple).
Larynx
 Epiglottis – a large leaf shaped piece of elastic cartilage.
 During swallowing, the epiglottis closes off the glottis (vocal
cords) and prevents food from entering the larynx and airways
inferior to it. It shunts food to the esophagus.
Larynx
 Cricoid cartilage.
 A ring of cartilage that forms the inferior wall of the larynx.
 This cartilage serves as the landmark for making an emergency
airway (tracheostomy).
Voice Production
 The mucous membrane of the larynx forms two pairs of
folds.
 Ventricular folds (false vocal cords) – superior.
 Vocal folds (true vocal cords) – inferior.
 If air is directed against the vocal folds they vibrate and
produce sounds (phonation).
Voice Production
 The greater the pressure of the air, the louder the sound.
 Pitch is controlled by tension on the vocal folds. If they
are pulled taught, the pitch raises. Decreasing muscular
tension results in lower sounds.
 Vocal folds are usually thicker and longer in males than
in females resulting in a lower pitch.
Laryngitis & Cancer Of The Larynx
 Laryngitis is an inflammation of the larynx.
 It is often caused by a respiratory infection or irritants such
as cigarettes or smoke.
Laryngitis & Cancer Of The Larynx
 Chronic inflammation in long term smokers can cause a
permanent hoarseness.
 Cancer of the larynx is found almost exclusively in smokers.
 Treatment consists of radiation therapy and / or surgery.
Trachea
 The trachea (windpipe) is a tubular passageway for air that is
about 12 cm long and 2.5 cm in diameter.
Trachea
 It is anterior to the esophagus and extends from the larynx to
the superior border of the 5th thoracic vertebra where it
branches to form bronchi.
Trachea
 Layers:
 Mucosa.
 Pseudostratified ciliated columnar epithelium and goblet cells.
 Submucosa.
 Hyaline cartilage.
 16 – 20 incomplete, horizontal rings that resemble the letter C.
 The open part of each ring faces the esophagus and allows slight
expansion of the esophagus into the trachea during swallowing.
 The solid C shaped ring prevents collapse of the trachea.
 Adventitia.
 Areolar connective tissue that joins the trachea to the surrounding tissues.
Tracheostomy & Intubation
 Several conditions can block airflow:
 A crushing injury to the chest.
 Inflammation of the mucous membrane causing swelling.
 Vomit or another foreign object may be aspirated into it.
 If the obstruction is superior to the larynx, a tracheostomy
may be performed.
Tracheostomy & Intubation
 A tracheostomy is an operation to make an opening into
the trachea.
 Intubation involves inserting a tube into the mouth or
nose and passing it inferiorly through the larynx or
trachea. The tube pushes any flexible obstruction out of
the way. Mucous can be suctioned through the tube and
the lumen provides a passageway for air.
Bronchi
 The trachea divides into a right primary bronchus and a
left primary bronchus at the superior border of T5.
 Carina – the ridge where the trachea branches into the
right and left bronchi. The mucous membrane is the
most sensitive here and triggers the cough reflex.
 Upon entering the lungs, the primary bronchi divide
into secondary (lobar) bronchi – one for each lobe of the
lung. 3 on the right and 2 on the left.
Bronchi
 They then branch to tertiary (segmental) bronchi and
eventually bronchioles.
 Terminal bronchioles are the smallest branch.
 This branching is referred to as the bronchial tree.
Bronchial Control
 The amount of cartilage decreases as we move down the
bronchial tree and the amount of smooth muscle increases.
 With no supporting cartilage, muscle spasms can close of the
airways as in an asthma attack.
Bronchial Control
 Sympathetic nerve stimulation causes relaxation of the
smooth muscles of the bronchioles through release of
epinephrine and norepinephrine.
 The parasympathetic division of the ANS and mediators of
allergic reactions such as histamine cause contraction of
bronchiolar smooth muscle.
Lungs
 Trauma to the chest which causes one lung to collapse may
not affect the other as they are in two distinct chambers.
 There are two layers of the pleural membrane:
 Visceral pleura and parietal pleura.
 The pleural cavity is the space between these membranes and is
filled with serous fluid.
Lungs
 Pleurisy or pleuritis is an inflammation of the pleural
membrane.
 Pleural effusion is an accumulation of fluid in the pleural
space due to persistence of inflammation.
Surface Anatomy Of The Lungs
 Base.
 Apex.
 Costal surface.
 Mediastinal (medial) surface.
 Hilus.
 Root.
 Cardiac notch.
Lobes, Fissures, & Lobules
 The lungs are divided into lobes by fissures.
 Each lung has an oblique fissure. The right lung also has
a horizontal fissure.
 The left lung has a superior and an inferior lobe. The
right lung has these as well as a middle lobe.
 Each lobe receives its own secondary (lobar) bronchus.
Lobes, Fissures, & Lobules
 Superior, middle, and inferior bronchi on the right and
superior and inferior bronchi on the left.
 The tertiary (segmental) bronchi arise from the lobar
bronchi and supply a bronchopulmonary segment.
Lobes, Fissures, & Lobules
 Terminal bronchioles are called respiratory bronchioles.
 Respiratory bronchioles are subdivided into alveolar ducts.
 There are about 25 orders or branching from the trachea to
the alveolar ducts.
Alveoli
 The alveoli and alveolar sacs surround the opening of the
alveolar ducts.
 An alveolus is a cup-shaped outpouching lined by simple
squamous epithelium.
Alveoli
 An alveolar sac consists of 2 or more alveoli that share a
common opening.
 Type I and type II alveolar cells line the alveolar wall
along with alveolar macrophages (dust cells).
 Type II alveolar cells secrete alveolar fluid with
surfactant. Surfactant lowers the surface tension of the
alveolar fluid and prevents the alveoli from collapsing.
Respiratory Membrane
 The alveolar walls and capillary walls form the
respiratory membrane.
 Exchange of O2 and CO2 takes place here.
 The respiratory membrane is very thin, which allows for
rapid diffusion of gases.
 The lungs contain an estimated 300 million alveoli,
providing a surface area of about 70m2 for the exchange
of gases.
Nebulization
 Nebulization is a treatment that administers medication
in the form of droplets suspended in air to the
respiratory tract.
 The patient inhales the medication as a fine mist.
 Various drugs are used. Some relax the smooth muscles
of the respiratory tract, some reduce the thickness of
mucous, and antibiotics are used.
Blood Supply To The Lungs
 Deoxygenated blood passes from the right ventricle into the
pulmonary trunk, which divides into a left and right
pulmonary artery.
 Four pulmonary veins return oxygenated blood to the left
atrium.
Blood Supply To The Lungs
 Pulmonary blood vessels constrict in the presence of hypoxia
(low O2) unlike blood vessels elsewhere in the body. This
shunts blood from poorly ventilated areas of the lung to wellventilated regions.
 This is known as ventilation-perfusion coupling
because the perfusion (blood flow) matches the ventilation
(air flow) to an area.
Blood Supply To The Lungs
 Bronchial arteries, which branch from the aorta, deliver
oxygenated blood to the lungs.
 This blood peruses the walls of the bronchi and bronchioles.
Pulmonary Ventilation
 Respiration (gas exchange) occurs in 3 steps:
 Pulmonary ventilation (breathing) – the mechanical flow of air
into (inhalation) and out of (exhalation) the lungs.
 External respiration – the exchange of gases between the air
spaces of the lungs and the blood in the capillaries.
 Internal respiration – the exchange of gases between the blood
in systemic capillaries and tissue cells.
 Pulmonary ventilation (breathing) is the process by
which gases flow between the atmosphere and the lung
alveoli.
Inspiration & Expiration
Pressure Changes During
Pulmonary Ventilation
 Air moves into the lungs when air pressure in the atmosphere
is greater than air pressure in the lungs.
 Air moves out of the lungs when the pressure inside the lungs
is greater than the pressure in the atmosphere.
Inhalation
 Breathing in is called inhalation (inspiration).
 Increasing the volume of the lungs causes inhalation.
 Contraction of the diaphragm and the external intercostals
expands the lungs.
Boyles Law
 The pressure of a gas in a closed container is inversely
proportional to the volume of the container.
 If the size of a closed container increases, the pressure inside
the container decreases.
 If the size of a closed container decreases, the pressure inside
the container increases.
Muscles Of Inhalation
 The most important muscle of inhalation is the diaphragm.
 The next most important muscles in inhalation are the
external intercostals.
Exhalation
 Breathing out is called exhalation (expiration).
 Elastic recoil of the chest wall and lungs causes exhalation.
 Recoil of the elastic fibers that were stretched during
inhalation.
 The inward pull from surface tension of the film of alveolar
fluid.
Active Exhalation
 Exhalation becomes active only during forceful breathing
such as when playing a wind instrument or during exercise.
 The muscle of exhalation then contract.
 Abdominals.
 Internal intercostals.
Factors Affecting Pulmonary
Ventilation
 Surface tension of alveolar fluid. A deficiency in surfactant in
premature infants causes respiratory distress syndrome.
Factors Affecting Pulmonary
Ventilation
 Compliance of lungs refers to how much effort is
required to stretch the lungs.
 Decreased compliance results from scar tissue (TB), excess fluid
(pulmonary edema), a deficiency in surfactant, or paralysis of
muscles of inspiration.
 Airway resistance – any condition that narrows or
obstructs airways increases resistance.
 Chronic obstructive pulmonary disorders (COPD) such as
asthma, emphysema, or bronchitis increase airway resistance.
Breathing Patterns
 Eupnea – a normal pattern of quiet breathing.
 Costal breathing – shallow (chest) breathing. An upward
and outward movement of the chest due to contraction
of the external intercostal muscles.
 Diaphragmatic breathing – deep (abdominal) breathing
consisting of outward movement of the abdomen from
contraction and descent of the diaphragm.
Modified Respiratory Movements
 Coughing
 Sneezing
 Sighing
 Yawning
Modified Respiratory Movements
 Sobbing
 Crying
 Laughing
 Hiccuping
 Valsalva maneuver
Lung Volumes & Capacities
 Tidal volume (VT)– the volume of one breath.
 Minute ventilation (MV) is the volume of inhaled and
exhaled air in one minute. It is determined by
multiplying the respiratory rate by the tidal volume.
 A spirometer or respirometer are utilized to measure the
volume of air used.
 A spirogram is the record of this volume.
Lung Volumes & Capacities
 Typically, about 70% of the tidal volume reaches the
respiratory portion of the respiratory system. The remaining
airways are known as the anatomic dead space.
 By inhaling deeply, you can take in additional air
(inspiratory reserve volume).
Lung Volumes & Capacities
 The expiratory reserve volume is the additional air from
a forced exhale.
 Even after a forced breath, some air remains. This is the
residual volume.
Lung Volumes & Capacities
 The inspiratory capacity is the sum of the tidal
volume and the inspiratory reserve volume.
 The functional residual capacity is the sum of
residual volume and expiratory reserve volume.
 Vital capacity is the sum of inspiratory reserve
volume, tidal volume, and expiratory reserve volume.
 Total lung capacity is the sum of vital capacity and
residual volume.
External Respiration
 External respiration or pulmonary gas exchange is the
diffusion of O2 from air in the alveoli of the lungs to
blood in pulmonary capillaries and the diffusion of CO2
in the opposite direction.
 External respiration converts deoxygenated blood
coming from the right side of the heart into oxygenated
blood that returns to the left side of the heart.
 External respiration occurs only in the lungs.
Internal Respiration
 Internal respiration or systemic gas exchange is the exchange
of CO2 and O2 between the systemic capillaries and tissue
cells.
 Internal respiration occurs in tissues throughout the body.
Oxygen Transport
 Oxygen does not dissolve easily in water.
 Most of the blood O2 is bound to hemoglobin.
 Oxygen and hemoglobin bind in an easily reversible reaction
to form oxyhemoglobin.
Carbon Monoxide Poisoning
 Carbon monoxide CO is a colorless and odorless gas found in
exhaust fumes from automobiles, gas furnaces, space heaters,
and tobacco smoke.
 CO binds to hemoglobin about 200 times as strong as O2 and
uses up the available hemoglobin molecules.
Carbon Monoxide Poisoning
 Bright, cherry red color of the lips is a sign.
 Administering pure oxygen speeds up the dissociation of CO
from hemoglobin and can save a persons life.
Respiratory Center
 The respiratory center in the brain stem controls the
basic rhythm of respiration.
 3 areas:
 Medullary rhythmicity area – controls the basic rhythm.
 Inspiratory and expiratory areas.
 Pneumotaxic area – impulses turn off the inspiratory area
before the lungs become too full.
 Apneustic area – activates the inspiratory center and prolongs
inspiration.
Chemoreceptor Regulation
 Chemoreceptors regulate the levels of O2 and CO2.
 Central chemoreceptors are located in the medulla
oblongata.
 Peripheral chemoreceptors are located in the aortic bodies
and carotid bodies.
Hypoxia
 A deficiency of O2 at the tissue level.
 4 types:
 Hypoxic hypoxia – low PO2 in arterial blood from high altitude,
airway obstruction or fluid in the lungs.
 Anemic hypoxia – too little hemoglobin due to hemorrhage,
anemia, CO poisoning.
 Ischemic hypoxia – blood flow to a tissue is reduced.
 Histotoxic hypoxia – tissues cannot use O2 properly due to
some toxic agent (I.E. Cyanide poisoning).
Influences On Respiration
 See page 840 in text.