The Respiratory System
Fun Facts
• The highest recorded "sneeze speed" is
165 km per hour.
• The surface area of the lungs is roughly
the same size as a tennis court.
• The capillaries in the lungs would extend
1,600 kilometers if placed end to end.
• We lose half a liter of water a day through
breathing. This is the water vapor we see
when we breathe onto glass.
Functions
2 Basic Functions:
• 1. Air distribution
• 2. Gas exchange
• Supplies body w/ O2
• removes CO2
• O2/CO2 levels maintained homeostatically
Additional functions
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3. Filters, warms and humidifies air
4. Sound production
5. Olfaction
6. Homeostasis of gases, ph of blood
Structures
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Nose
Pharynx
Larynx
Trachea
Bronchi
“Upside-down tree” –Bronchioles
Lungs - Alveoli
Upper Resp Tract
Lower Resp Tract
1. Resp Mucosa
• Membrane that lines most of the air
distributing tubes of resp tract
• Covered w/ mucous that cleanses, warms
and humidifies inspired air. More than 125
ml of resp mucous produced daily
• Covered w/ cilia that move debris out of
resp tract, away from lungs
NOSE
• Made of bone and cartilage
• External nares: nostrils: hair filters dust,
blood vessels under surface warm air,
mucous humidifies it
• Div by nasal septum (vomer and ethmoid
bones)
• R&L nasal cavities: lined w/ nasal mucosa
(ciliated epithelium)
NOSE
• Olfactory receptors: nerve endings
responsible for olfaction (smell). They
detect vaporized chemicals that have
been inhaled **Sense organ
• Functions: warm and humidify inhaled air;
• Lacrimal sacs: tear ducts that drain into
nasal cavities
PARANASAL SINUSES
• #4: frontal, maxillary, ethmoidal and
sphenoidal
• Frontal and maxillary are largest
• Functions: lightens the weight of the skull,
assists w/ sound and mucous production
for resp tract
• Lined w/ ciliated epithelial tissue
• Mucous produced drains into nasal cavity
• Sinusitis
PHARYNX
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Muscular tube w/ resp & digestive function
@ 5 inches long
Divided into 3 sections:
1. Nasopharynx: directly behind nasal
cavity for passage of air only; connects to
middle ear by eustachian tubes
• 2. Oropharynx: behind mouth
• 3. Layrngopharynx: lowest segment; opens
ant. into larynx & post into esophagus
• Function: food and air passageway
T0NSILS
• Masses of lymph tissue embedded in
mucous membrane
• of pharynx
LARYNX
• Voice box
• Located between the pharynx and the
trachea
• 2-inch-long, tube-shaped organ in the
neck.
• 9 pieces of cartilage bound by muscle and
ligaments. Largest is thyroid cartilage
(adams apple), lowest is cricoid cartilage
• Functions:
• 1. Air passageway between pharynx and
trachea
• 2. Sound production: vocal cords, two
bands of muscle, form a "V" inside the
larynx. These tighten up and move closer
together. Air from the lungs is forced
between them & makes them vibrate,
produces the sound of our voice. The
tongue, lips, teeth form this sound into
words.
• Glottis: space between cords
LARYNX
• Epiglottis: flap of cartilage that protects the
trachea from food entry
• The esophagus is just behind the trachea
and larynx. The openings of the
esophagus and the larynx are close
together. When we swallow, this flap
moves down over the larynx to keep food
out of trachea
TRACHEA
• 12 cm (5 in)Tube-like portion of resp tract that
connects the larynx with the bronchial tree
16-20 “C” shaped rings of cartilage that are
stacked w/ little soft tiss in between
• Open section of the C allows faces esophagus &
allows for expansion of esophagus when food is
swallowed
• Strong tiss to prevent collapse during inspiration
Upper Resp Disorders
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Rhinitis
Pharyngitis
Laryngitis
Deviated septum
Epistaxsis
Sinusitis
Tonsilitis
• Common cold: caused by over 200
viruses. Spread by direct contact and in air
droplets. Often leads to secondary
infection
• Influenza: flu involving upper and lower
resp tracts. Cause: virus and often leads
to secondary infection that can be life
threatening to young children and elderly
TRACHEA
• Lined w/ mucosa that is ciliated epithelial
tissue
• Cilia help sweep debris toward pharynx
• Function: air passage to lungs
• Complete obstruction: 5th cause of
accidental death in US. Tx: Heimlich
Maneuver
• Branches into R & L primary bronchi that
enter lungs
BRONCHIAL TREE
• Trachea branches into R&L primary
bronchi which divide into smaller
secondary bronchi in each lung
• Bronchi divide into bronchioles which
subdivide into alveolar ducts then alveolar
sacs then alveoli in the lungs
LUNGS
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Large paired organs of thoracic cavity
Function: gas exchange
R lung has 3 lobes (sup, mid, inferior);
L has 2 (sup, inferior)
Apex: superior portion, under clavicle
Base: inferior section, rests on diaphragm
Hilus: indentation on medial surface of each lung
where primary bronchus, pulmonary artery and
veins enter each lung
ALVEOLI
• Functional unit of the lung
• Millions in each lung surrounded by
capillary network
• Walls made of simple squamous epithelial
tissue; elastic connective tissue between
clusters necessary for exhalation
• Each is lined with thin layer of tissue fl
necessary for diffusion of gases
• Surfactant: lipoprotein that lines the
alveolus; decreases surface tension and
prevents collapse of alveoli during
respiration
• Function of bronchus to alveoli: air
distribution and gas exchange
• Movement of gases between alveolus and
capillaries occurs by diffusion
PLEURAL MEMBRANES
• AKA: respiratory membrane
• Thin barrier between blood in capillaries
and air in alveoli
• Allows for diffusion of gasses due to the
thinness of this membrane
PLEURA
• Covers outer surface of lungs and inner
surface of rib cage
• Function: reduce friction between lungs
and chest wall
• Parietal pleura: lines walls of thoracic
cavity
• Visceral pleura: covers lungs
• Interpleural space: between these,
contains serous fluid to reduce friction
Lower Resp Tract Disorders
• Pleurisy: inflammation of parietal pleura
• Atelactasis: collapse of the lung; different
causes
• Pneumothorax: air in pleural space;
caused by rib fx or can be spontaneous
• Hemothorax: blood in pleural space
• Tx: chest tube to allow lung to re-expand
Respiratory Distress
• RDS: Respiratory Distress Syndrome:
inability of alveoli to inflate
• Infant RDS: lack of surfactant in premature
infants. AKA: Hyaline membrane disease
• Adult RDS: due to irritant (chemical,
smoke, vomit) that causes edema of
alveoli
Respiration
• Exchange of O2 & CO2 between a living
organism and the environment
• External: movement of air in and out of
lungs to allow for exchange of gases
between lungs and capillaries
• Internal: Exchange of gases between
capillaries and cells of the body
• Cellular: use of O2 by cells for metabolism
Mechanics of Breathing
• Pulmonary ventilation: involuntary
muscular work and a change of air
pressure in thoracic cavity. Occurs in 2
stages:
• Inspiration: moves air into lungs; active
• Expiration: moves air out; passive
• Resp muscles: diaphragm and intercostals
Inspiration
• Thoracic cavity enlarges allowing air to enter
• Motor impulse from medulla to resp muscles
• Diaphragm contracts and flattens; ^ thoracic
cavity size
• External intercostals contract & pull ribs up and
out; ^ thoracic cavity size from front to back/side
to side
• ^ size = decreased pressure in thoracic cavity
the result air entry into lungs.
Expiration
• Impulse stops, muscles relax
• Thoracic cavity returns to smaller size which ^
pressure, lungs recoil and decrease in size
forcing air out (passive)
• Forceful expiration: expiratory muscles the
internal intercostals/abdominal muscles contract
to further decrease size of thoracic cavity
• ^ air press in thoracic cavity result air flows out
of lungs
O2-CO2 Exchange
1. O2 concentration ^ in alveoli, low in
capillaries.
2. CO2 is reverse low in alveoli ^ in
capillaries
Gases move by diffusion: move from high to
low press gradient which is passive
transport mechanism
Gas exchange in Lungs
• AKA external respiration
• O2 moves out of alveolar air into blood
and combines w/ Hgb in lung capillaries to
form oxyhemoglobin.
• This bond is unstable so when bld passes
thru tiss capillaries w/ low O2 concentrates
it breaks and releases O2 to diffuse from
RBC into tissue cell
• CO2 diffuses in opp direction (into RBC)
• Some binds w/ Hgb to form
carbaminohemoglobin
• Most CO2 is carried in plasma in the form
of bicarbonate ion. It combines w/ H2O to
form carbonic acid (H2CO3) which will
disassociate to form H and HCO3 (bicarb)
• In lungs, CO2 will dissociate from bicarb
and carbamino to diffuse out of bld into
alveolar air
Gas Exchange in Tissues
• AKA internal respiration
• Tissue capillaries: site for breakdown of
oxyhemoglobin
• O2 then moves out of cap and into cells of
the tissue
• O2 necessary for metabolic activity/cell
respiration
• O2-CO2 move by diffusion: O2 moves
from cap bld to cells in tiss; CO2 does
reverse
• CO2 leaves tiss cells and enters
capillaries where
bicarb/carbaminohemoglobin forms to
transport it to the lungs
Volumes of Air Exchanged
• Normal inspiration takes in @ 500ml of air
• Tidal volume: amt of normal
inspiration/expiration
• Vital Capacity: largest amt that can be
inspired/expired in 1 breath (@ 4800 ml in
young adult)
• Expiratory Reserve: amt of air forcibly
exhaled after tidal volume (@ 10001200ml)
• Inspiratory Reserve: amt of air forcibly
inhaled
• VC = TV + IRV + ERV
• Residual volume: air that remains in the
lungs after forcible expiration (@ 1200ml)
• VC = TV + IRV + ERV
• Total Lung Capacity = VC + resid vol
(5700-6200ml)
Regulation of Respiration
• Nervous and chemical regulation allow the
body to adapt to changing demands for O2
Nervous Sys Regulation
• Resp control centers in medulla and pons:
send impulses to the muscles of
respiration based on input from receptors
throughout the body
• O2, CO2, ph of bld, amt of stretch in lung
tissue send messages to medulla to adapt
respiratory rate
• 2 most important control centers are
insp/exp centers of medulla
• Inspiratory center in medulla automatically
generates impulse to produce resp rate @
12-18 breaths per minute
• Impulse from medulla to nerves to resp
muscles to stimulate contraction result =
inhalation
• Lungs inflate causing stretch which
generates impulse to medulla to depress
inspiratory center & stimulate expiratory ctr
which will decrease # impulses to resp
muscles result = exhalation
• Chemoreceptors: specialized cells in
carotid/aortic bodies that respond to varying gas
and ph levels to modify respiratory rate
• Pulmonary stretch receptors: in airway/alveoli:
stimulated when tidal vol is reached and inhibit
inspiratory center – prevents overinflation
• Cerebral cortex: limited/voluntary control of
breathing
Chemical Regulation
• Chemoreceptors located in carotids and
aorta detect changes in ph, O2 and CO2
levels of blood
• Decreased ph due to ^^ CO2 causes
acidosis
• Medulla will respond by ^^ resp rate to
exhale more CO2 and ^^ O2 levels to
decrease acidity of blood
Breathing Terms
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Eupnea: normal breathing
Hyperventilation: rapid/deep
Hypoventilation: slow/shallow
Dyspnea: difficult
Orthopnea: dyspnea relieved in upright
position
• Apnea: no respirations
• Cheyne-Stokes: cycles of
hyperventilation/dyspnea + apnea
• Hypoxia: Insufficient O2 to tissue
• Respiratory arrest: failure to resume
breathing after period of apnea
More Respiratory Disorders
• Bronchitis: URI
• s/s: non-prod then prod cough
• Tx: antibiotics (often this is a secondary
inf)
• Pneumonia: acute lung infec/inflamm,
airway blocked w/ exudate (thick fl). Strept
is common cause
• s/s: fever, malaise, h/a, cough, chest pain
• Aspiration pneumonia, bronchial, lobar
• Tx: antibiotics, mechanical ventilation if
resp distress is severe
• TB: chronic contageous (airborne) lung inf.
Caused by mycobacterium tuberculosis
• s/s: fatigue, pleurisy, wt loss, fever,
dyspnea
• Tx: long term antibiotics
• Pleural Effusion: excess fluid in pleural
space; often caused by infection, heart
failure or CA
TB
Pleural effusion
Obstructive Disorders
• COPD: progressive, often irreversible
obstruction of airflow
• Includes: chronic bronchitis (chronic
inflammation usually c/b smoking),
emphysema (chronic bronchitis causing
rupture of alveoli), asthma (spasm of
smooth muscle tissue in smaller bronchial
air passages)
• Tx: primarily symptomatic
Lung CA
• Malignancy of pulmonary tissue that can
metastasize
• s/s: none until well advanced; smokers
cough, wt loss, hoarseness
• Tx: lobectomy, pneumonectomy, chemo,
radiation
• One of the most common type of CA
Chemical Imbalance
• Resp acidosis: CO2 accumulation due to
decreased resp rate (excess H ions cause
decreased ph) ^ H = Acidosis when Ph
starts drifting below 7.47
• Resp alkalosis: Low CO2 blood levels due
to ^ resp rate eg. hyperventilation
decreased H= Alkalosis when Ph starts ^^
above 7.47