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Biology 233
Human Anatomy and Physiology
Chapter 23 Lecture Outline
RESPIRATORY SYSTEM
respiration – gas exchange (O2 & CO2)
cellular respiration (aerobic respiration)
mitochondria consume O2 to produce ATP (cells need O2)
and produce CO2 as a by-product (cells must get rid of CO2)
STEPS IN RESPIRATION
1) pulmonary ventilation – breathing
inhalation (inspiration) – breathing in; O2 rich air flows into lungs
exhalation (expiration) – breathing out; CO2 rich air flows out of lungs
2) external respiration – exchange occurring in lungs
air in lungs (high in O2)
blood in pulmonary capillaries (high in CO2)
3) internal respiration – exchange occurring in systemic tissues
blood in systemic capillaries (high in O2)
body tissues (high in CO2)
STRUCTURAL DIVISIONS OF THE RESPIRATORY SYSTEM
Upper Respiratory System
nose, pharynx, associated structures
Lower Respiratory System
larynx, trachea, bronchi, lungs
FUNCTIONAL DIVISIONS OF THE RESPIRATORY SYSTEM
Respiratory Portion – site of external respiration
respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
respiratory membrane – very thin membrane between blood and air in
lungs; very large surface area for exchange
Conducting Portion – carries air to the respiratory portion
nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
respiratory mucosa (mucous membrane) – ciliated epithelium and
and connective tissue that secretes mucus
Other Functions of Conducting Portion:
conditions air – filters, warms, moisturizes
olfaction – olfactory epithelium
sound production - communication
protection – respiratory defense system
nose hairs, mucus, cilia, macrophages, tonsils
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ANATOMY OF THE UPPER RESPIRATORY SYSTEM
1) NOSE – functions in conditioning air, olfaction, speech modification
(resonating chamber)
External Nose – filters out inhaled particles
bone and hyaline cartilage framework
anterior – lined by integument
nose hairs filter out large inhaled debris
posterior – lined by mucosa
sticky mucus traps inhaled debris
external nares – nostrils
Nasal Cavity – internal nose
nasal septum divides nasal cavity into right & left halves
posterior – vomer and ethmoid bones
anterior – hyaline cartilage
(deviated septum – displaced laterally)
nasal conchae (turbinates) – stir air, increase surface area
ethmoid – superior and middle conchae
inferior nasal concha
nasal meatuses - 3 tunnels between the 3 conchae
nasal mucosa - pseudostratified ciliated columnar epithelium
with goblet cells
mucus moisturizes air and traps debris
cilia sweep debris down into pharynx
olfactory epithelium
openings to paranasal sinuses – resonating chambers
ethmoid, sphenoid, frontal, & maxillary bones
internal nares – opening from nasal cavity to pharynx
2) PHARYNX (throat) – internal nares to larynx
funnel of bone and muscle
mucosa lines surface
Functions of the Pharynx:
conduction – air to larynx; food & fluids to esophagus
resonating chamber
immunity – tonsils (lymphatic nodules)
3 Divisions of Pharynx:
1) nasopharynx – superior portion; air passageway
soft palate, uvula
pseudostratified ciliated columnar epithelium/goblets
entrance to Eustachian (auditory) tubes
pharyngeal tonsil (adenoids)
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2) oropharynx – middle portion; air, food, fluid passageway
uvula to hyoid bone
fauces – opening from oral cavity
stratified squamous epithelium – protects from abrasion
palatine and lingual tonsils
3) laryngopharynx – inferior portion; air, food, fluid passageway
hyoid to cricoid cartilage of larynx
stratified squamous epithelium – abrasion
anterior opening into larynx
posterior opening into esophagus
ANATOMY OF THE LOWER RESPIRATORY SYSTEM
1) LARYNX (voice box)
cartilage and ligamentous tube between laryngopharynx and trachea
9 CARTILAGES OF LARYNX:
Thyroid Cartilage (Adam’s apple)
superior, anterior wall of hyaline cartilage
thyroid membrane – ligament connected to hyoid
Cricoid Cartilage – ring of hyaline cartilage
inferior, posterior wall
Cuneiform Cartilages (2) – support lateral laryngeal structures
Corniculate Cartilages (2) – apex of arytenoid cartilages
Epiglottis – leaf-shaped elastic cartilage
glottis – opening into larynx
vocal folds (cords) – folds in mucosa bordering glottis
during swallowing
extrinsic muscles attached to thyroid and cricoid cartilages
elevate the larynx
epiglottis folds down to cover glottis
keeps food and fluids out of trachea
Arytenoid Cartilages (2) – hyaline cartilages attached to cricoid by pivot
joints
vocal folds attached to arytenoid cartilages
vibrate to produce sounds
intrinsic muscles move arytenoids and alter pitch
close to protect airways or hold breath
vestibular folds – superior to vocal folds; protect vocal folds
cough reflex – stimulated by liquid or solid in larynx
Epithelium of Larynx:
superior to vocal folds – stratified squamous
inferior to vocal folds – pseudostratified ciliated columnar/goblets
cilia sweep debris up into pharynx
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2) TRACHEA (windpipe) – tube of hyaline cartilage and ligaments
extends from larynx to primary bronchi
Histology of Trachea
1) mucosa – pseudostratified ciliated columnar epithelium/goblets
cilia sweep debris up to pharynx
2) submucosa – areolar connective tissue with mucous glands
3) hyaline cartilage
15-20 C-shaped tracheal cartilages
trachealis muscle – smooth muscle completes ring posteriorly
adjusts diameter of trachea (ANS)
elastic fibers – allow esophagus to compress trachea
when swallowing
3) BRONCHI – 3 divisions (respiratory tree)
1) Primary (main stem) Bronchi – right & left to lungs
tracheal bifurcation – splits in 2
carina – internal ridge between primary bronchi
very sensitive to cough reflex
right primary bronchus – straighter, wider & shorter than left
more prone to aspiration (breathing in debris)
2) Secondary (lobar) Bronchi – to lung lobes
right lung – 3 lobar bronchi
left lung – 2 lobar bronchi
3) Tertiary (segmental) Bronchi – 10 in each lung
bronchopulmonary segments
Histology of Bronchi
pseudostratified ciliated columnar epithelium/goblets
C-shaped cartilages (largest bronchi)  cartilage plates
4) BRONCHIOLES – branches of tertiary bronchi (respiratory tree)
branch many times
terminal bronchioles – end of conducting portion
respiratory bronchioles – beginning of respiratory portion
histology changes as bronchi get smaller:
epithelial cells get shorter and lose cilia & goblet cells
amount of cartilage decreases
smooth muscle in walls increases
terminal bronchioles – simple cuboidal epithelium
respiratory bronchioles – become simple squamous
ANS regulates diameter of airways
sympathetic – bronchodilation increases airflow
parasympathetic – bronchoconstriction decreases airflow
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asthma – bronchoconstriction (especially in bronchioles) makes
breathing difficult
stimulated by allergies (histamine) or parasympathetic division
5) ALVEOLAR STRUCTURES
alveolar ducts – final branches of respiratory tree
(25 orders of branching)
alveolar sacs – common opening for 2 or more alveoli
alveoli – main site for external respiration (300 million)
surrounded by capillaries
Histology of Alveolus
respiratory membrane – site of gas exchange
very thin (.5 micrometers); large surface area (70 meters2)
layers:
1) alveolar wall – simple squamous epithelium
2) basement membranes (2) – contain elastic fibers
3) endothelium of capillaries – simple squamous epithelium
alveolar cells
type I – simple squamous epithelium; site of gas exchange
type II (septal cells) – cuboidal cells; secretory
surfactant – oily secretion (lipids and proteins)
lubricates and protects alveolar cells
lipids reduce surface tension (attraction of
water molecules for each other)
prevents alveoli collapsing
alveolar macrophages
6) LUNGS
Thoracic Cavity – divided by mediastinum into 2 pleural cavities
pleural membranes – serous membranes
parietal pleura – lines cavity
visceral pleura – lines lungs
pleural cavities – contain pleural fluid (lubricates lungs)
pleural effusion – excess fluid accumulation
thoracocentesis – drain pleural fluid through a needle
inserted below 7th rib
pleuritis – inflammation of pleural membranes
causes friction and pain
Gross Anatomy of Lungs
base – broad end near diaphragm
apex – pointed end under clavicle
hilus – entry point for bronchi, nerves, blood & lymph vessels
fissures divide lungs into lobes
each lobe is supplied by a secondary (lobar) bronchus
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right lung – 3 lobes
superior, middle, inferior
left lung – 2 lobes
superior, inferior
lobes subdivided into bronchopulmonary segments
10 in each lung (usually fuse in left lung)
each supplied by one tertiary bronchus, artery and vein
bronchopulmonary segments subdivided into many lobules
each supplied by one terminal bronchiole, arteriole, venule
BLOOD SUPPLY TO LUNGS
Pulmonary Circuit (branches follow respiratory tree)
right & left pulmonary arteries (deoxygenated)
pulmonary capillaries surround alveoli
2 right & 2 left pulmonary veins (oxygenated)
Ventilation – Perfusion Coupling
hypoxia (low O2) in lung tissues causes vasoconstriction
diverts blood to lung regions with good oxygenation
(opposite effect occurs in other body tissues)
Systemic Circuit
bronchial arteries – branches of aorta
supply walls of bronchi and larger bronchioles
bronchial veins – branches of azygous vein
(most blood returns via pulmonary veins)
PULMONARY PHYSIOLOGY
PULMONARY VENTILATION
air flows from high pressure to low pressure
air pressure is due to movement of air molecules
760 mmHg at sea level (1 atmosphere)
Boyle’s Law – air pressure varies inversely with volume
increase volume of container = air pressure decreases
decrease volume of container = air pressure increases
(ventilation occurs due to changing size of thoracic cavity)
Regions of Pressure
1) atmospheric pressure – air pressure around body
2) alveolar pressure – air pressure inside lungs
3) intrapleural pressure – air pressure in pleural cavity
slightly less than alveolar pressure (partial vacuum)
due to elasticity of lung tissue
visceral pleura adheres to parietal pleura
surface tension due to pleural fluid
(suction cup effect)
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Inhalation – occurs when alveolar pressure < atmospheric pressure
1) size of thoracic cavity increases – active process
diaphragm contracts – flattens to increase height of cavity
external intercostal muscles contract – lift ribs
increases diameter of cavity
2) volume of pleural cavity increases = intrapleural pressure decreases
3) lungs adhere to thoracic wall, stretch and expand
lung volume increases = alveolar pressure decreases
4) air flows into lungs until alveolar pressure = atmospheric pressure
quiet inhalation – diaphragm flattens 1cm
2 mmHg pressure difference / ½ liter of air
forced inhalation – diaphragm flattens 10cm, accessory muscles help
elevate ribs
30 mmHg pressure difference / 2-3 liters of air
Exhalation – occurs when alveolar pressure > atmospheric pressure
1) size of thoracic cavity decreases
diaphragm relaxes – rounds upward
external intercostals relax – ribs drop
2) pleural cavity & lungs decrease in volume
(elastic rebound of lung tissue & chest aids in decreasing volume)
alveolar pressure increases above atmospheric pressure
3) air flows out of lungs until alveolar pressure = atmospheric pressure
quiet exhalation is passive (muscles relax)
forced exhalation – active
internal intercostal muscles – pull ribs down
abdominal muscles – pull ribs down & compress abdominal cavity
abdominal organs push diaphragm up
Factors Affecting Pulmonary Ventilation:
airway resistance – friction of air molecules on airways
regulated by diameter of airways
obstructive disorders – decrease diameter of airways
COPD (chronic obstructive pulmonary disease), asthma,
bronchitis
compliance – ability of thorax and lungs to stretch and expand
restrictive disorders – prevent expansion of thorax or lungs
less elasticity of tissues – fibrosis, inflammation
pneumonia – infection of lungs
physical compression
pleural effusion – fluid in pleural cavity
pneumothorax – air in pleural cavity
skeletal or muscular disorders
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increased surface tension in alveoli
deficiency of surfactant
pulmonary edema – fluid in lungs
Breathing Patterns
eupnea – normal, quiet breathing
dyspnea – difficult breathing
costal breathing – shallow expansions of chest
due to external intercostals
diaphragmatic breathing – deep abdominal breathing
due to contraction of diaphragm
apnea – absence of breathing
MEASURING VENTILATION
spirometer – measures volume of air inhaled or exhaled
tidal volume – volume of 1 breath
500 ml at rest
anatomic dead space – conducting portion
no gas exchange; 30% of tidal volume
70% of tidal volume reaches respiratory portion
minute ventilation – volume inhaled/minute
tidal volume X respiratory rate (12 breaths/min at rest)
alveolar ventilation rate
volume/minute that reaches respiratory portion
70% of minute ventilation
(alveolar ventilation can be increased by increasing tidal volume
or respiratory rate)
inspiratory reserve volume (3100 ml)
additional air inhaled during forced inhalation
inspiratory capacity (3600 ml)
tidal volume + inspiratory reserve volume
expiratory reserve volume (1200 ml)
additional air exhaled during forced exhalation
residual volume (1200 ml)
air in lungs after forced exhalation (cannot be exhaled)
functional residual capacity (2400 ml)
air in lungs after quiet exhalation
expiratory reserve + residual volume
vital capacity (4800 ml)
maximum volume you can forcefully inhale after forced exhalation
expiratory reserve + tidal volume + inspiratory reserve
total lung capacity (6000 ml)
vital capacity + residual volume
forced expiratory volume in 1 sec (FEV1.0)
volume exhaled in 1 sec with maximal effort following
a maximal inhalation
reduced by obstructive disorders
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RESPIRATION – EXCHANGE OF O2 & CO2
ATMOSPHERIC GAS
gas
nitrogen
oxygen
carbon dioxide
water vapor
others
atmospheric pressure = 760mmHg
% of atmosphere
partial pressure
78.6
597.4 mmHg
20.9
158 mmHg
0.04
0.3 mmHg
0.4
3.0 mmHg
0.06
0.5 mmHg
Dalton’s Law – each gas exerts its own pressure proportional to its concentration
partial pressure – pressure exerted by one gas in a mixture of gases
high concentration = high partial pressure
Henry’s Law – quantity of gas that will dissolve in a liquid is proportional to its
partial pressure
high partial pressure = more gas in solution
amount of a gas in solution also depends on the gas’s solubility
(ability to dissolve depends on molecular structure)
O2 – moderately soluble in body fluids
CO2 – 24X more soluble than O2
N2 – very little solubility in body fluids
Examples:
CO2 – very soluble, but low partial pressure in air
soda – high CO2 concentration added under pressure
N2 – very little normally dissolves in blood
scuba diving – pressurized air delivery = more N2 dissolves
decompression sickness
high altitude – lower atmospheric pressure
lower partial pressures of all gases
EXTERNAL (PULMONARY) RESPIRATION
deoxygenated blood becomes oxygenated
diffusion occurs across respiratory membrane
1) air in alveoli (high PO2 / low PCO2)
2) plasma in pulmonary capillaries (low PO2 / high PCO2)
INTERNAL (TISSUE) RESPIRATION
oxygenated blood becomes deoxygenated
oxygen diffuses into tissues through capillary endothelium
1) plasma in systemic capillaries (high PO2 / low PCO2)
2) interstitial fluid in tissues (low PO2 / high PCO2)
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OXYGEN TRANSPORT IN BLOOD
1) free O2 (dissolved in plasma) – 1.5%
only free O2 can be exchanged by diffusion
2) bound to hemoglobin (Hb) – 98.5%
oxyhemoglobin – bound to O2 (up to 4 molecules)
Hb saturation – percentage of O2-binding sites occupied
deoxyhemoglobin – no bound O2
FACTORS AFFECTING HEMOGLOBIN’S AFFINITY FOR O2
(oxygen-hemoglobin dissociation curve)
1) partial pressure of O2 (main factor)
> PO2 = more O2 saturation
alveolar air (100mmHg) – 97.5% saturation in blood leaving lungs
tissues (40mmHg at rest) – 75% saturation in blood leaving tissues
pressure is lower in active tissue
2) pH (Bohr effect)
lower pH (more H+ = acidic) = less O2 saturation
H+ binds to Hb and inhibits O2 binding
(metabolically active cells produce more acids)
3) partial pressure of CO2
>CO2 (binds Hb) = less O2 saturation
dissolved CO2 converted to carbonic acid
increases acidity = less O2 saturation
(metabolically active cells produce CO2)
reversible – low CO2 = increased pH = more O2 saturation (in lungs)
4) BPG (2,3-bis-phosphoglycerate) – from RBCs
>BPG (binds Hb) = less O2 saturation
(increases during increased metabolism – thyroxine, GH, epinephrine)
5) temperature
increased temp = less O2 saturation
(metabolically active cells produce heat)
6) fetal hemoglobin – different structure
higher affinity for O2 than adult Hb
7) carbon monoxide (CO)
binds to O2 binding sites on Hb = less O2 saturation
CO has 200X the affinity of O2
CARBON DIOXIDE TRANSPORT IN BLOOD
1) free CO2 (dissolved) – 7%
2) carbamino compound – 23% (bound to proteins)
carbaminohemoglobin – reversibly binds to globin portion of Hb
high PCO2 (tissues) - increases formation
low PCO2 (lungs) - CO2 released and diffuses out of blood
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3) bicarbonate ions – 70%
carbonic anhydrase – enzyme in RBCs catalyzes reaction
CO2 + H2O <-----------> H2CO3 <--------------> H+ + HCO3- (reversible)
carbonic acid
bicarbonate ion
H+ binds to Hb
chloride shift – HCO3- pumped into plasma in exchange for ClSUMMARY OF GAS EXCHANGE
External Respiration – lungs
pulmonary capillaries
hemoglobin – low O2 saturation
binds CO2 and H+
plasma – contains HCO3- and free CO2
alveolar air – high O2 and low CO2
free CO2 diffuses out of blood / O2 diffuses in
low CO2 pressure causes dissociation of CO2 and H+ from Hb
O2 binds to hemoglobin
H+ + HCO3- form CO2 which diffuses out of blood
(bicarbonate is used to buffer acids formed in body)
Internal Respiration – tissues
systemic capillaries
hemoglobin – high O2 saturation
plasma – low CO2
interstitial fluid – low O2 and high CO2
O2 dissociates from Hb and diffuses into tissues
CO2 diffuses from tissues into blood
CO2 in RBCs converted to HCO3- and H+
CO2 and H+ bind to deoxyhemoglobin
(hemoglobin also helps buffer acids in body)
CONTROL OF RESPIRATION
oxygen demands vary with metabolic activity
at rest – 200ml O2 / min
exercise – 15-20X higher demand
increasing O2 demand
cardiovascular changes – increased tissue perfusion
respiratory changes – increased ventilation (rate and volume)
LOCAL REGULATION – regulated by levels of O2 and CO2 in lung tissue
ventilation – perfusion coupling
< PO2 (hypoxia) = decreased perfusion
bronchiolar resistance
> PCO2 = bronchodilation
< PCO2 = bronchoconstriction
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CNS REGULATION – RESPIRATORY CENTERS
1) Respiratory Rhythmicity Centers – medulla oblongata
regulates contraction of respiratory muscles
dorsal inspiratory center – regulates quiet breathing
stimulates diaphragm and external intercostals for 2 sec.
(phrenic and intercostal nerves) = inhalation
no stimulation for 3 sec. = exhalation
ventral respiratory group – functions during forced breathing
regulates accessory muscles of inhalation and exhalation
2) Apneustic & Pneumotaxic Centers – pons
regulate rate and depth of breathing in response to ANS and higher brain
apneustic center – stimulates dorsal inspiratory center
pneumotaxic center – inhibits apneustic center
RESPIRATORY REFLEXES – ANS
Chemoreceptor Reflexes – triggered by levels of CO2, H+, O2
central chemoreceptors – medulla oblongata
detect H+ and CO2 levels in CSF
peripheral chemoreceptors – detect CO2, O2 and H+ levels in blood
aortic bodies (aortic arch) – vagus nerve (CN X)
carotid bodies (carotid sinus) – glossopharyngeal nerve (CN IX)
hypercapnia (high CO2) – main stimulus for respirations
also causes acidosis (more H+) – stimulates respirations
hypoxia (low O2) – lesser stimulus for respirations
(severe hypoxia depresses all brain functions)
hyperventilation – ventilation exceeding needs of tissues
hypocapnia – low CO2, may cause fainting
hypoventilation – ventilation inadequate to meet needs of tissues
Baroreceptor Reflexes – triggered by changes in blood pressure
low BP stimulates respirations
high BP inhibits respirations
Other Influences on Respirations
stretch reflexes – stretch receptors in bronchioles and alveoli
prevent overinflation or underinflation of the lungs
protective reflexes – irritation of airways stimulate sneezing & coughing
proprioceptive inputs – exercise stimulates respirations
temperature, pain
Cerebrocortical Regulation
allows limited voluntary control of breathing
holding breath, speaking, whistling, etc.
cortex has synapses with respiratory rhythmicity centers, apneustic center, and
respiratory motor neurons
buildup of CO2 and H+ eventually stimulate inspiratory area and override
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