Download The Respiratory System: Chapter 23

The Respiratory System
Chapter 23
Functions of the Respiratory System
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Pulmonary __________ - provides for gas
exchange
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Intake of O2
Elimination of CO2
Helps to __________________
Receptors for _________, _________ inspired
air, _____________ vocal sounds, and
__________ small amounts of water and heat
Gas exchange
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Pulmonary ventilation- breathing
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External respiration- (____________)
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Exchange of gases between alveoli and blood in
pulmonary capillaries across respiratory membrane
Blood gains O2, loses CO2
Internal respiration- (______________)
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Inhalation (_________) & exhalation (___________) of
air between atmosphere and alveoli of lungs
Blood systemic capillaries and tissue cells
Blood loses O2, gains CO2
Cells consume O2  ATP = cellular respiration
Anatomy of the Respiratory System
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_______________ Zone- filter, warm, moisten air
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Nose
Pharynx
Larynx
Trachea
Bronchi & Subdivisions
______________________- gas exchange
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Alveolar ducts, sacs, alveoli
Pleural membrane- 1 for each lung
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Visceral pleura- deep, covers lungs
Parietal pleura- superficial, lines thoracic cavity
Pleural cavity- contains pleural fluid causing:
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Pleurisy/pleuritis = inflammation of pleural mem.
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Reduction of friction
Increases surface tension
Pain due to friction between layers
If persists pleural effusion
Pneumothorax - cavity filled with air
Cells of the alveoli
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Type I cells – ___________________, nearly
continuous w/alveolar lining
Type II cells – _________, fewer, produce surfactant
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Round or cuboidal, free surfaces w/microvilli
Alveolar fluid keeps surface between cells & air moist
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Surfactant – complex mix of phospholipids and lipoproteins
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 surface tension of fluid   tendency of alveoli to collapse
Water–water interface would cause collapse of alveoli & make
walls difficult to separate once collapsed surfactant necessary
____________ – macrophages, remove dust and
other debris in alveolar spaces
Alveolus-capillary
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Together these create – ___________________
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O2 & CO2 easily diffuse back & forth
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These gases will move due to pressure difference
Move from high to low pressure
Consist of 4 layers:
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fig 23.12
Alveolar wall- type I & II alveolar cells, macrophages
Epithelial basement membrane
Capillary basement membrane
Capillary endothelium
Only _____________ thick
Musculature in breathing
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___________- most imp inhalation muscle
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Contraction causes it to flatten  lowering the
dome shape,  vertical diameter of thoracic cavity
Contraction responsible for almost 75% of air that
enters during quiet breathing
Descent of diaphragm inhibited by: advanced
pregnancy, excessive obesity, confining clothing
Musculature in breathing (2)
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_________________-2nd most important- inhalation
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Others- involved in labored inhalation only:
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when contract  elevate rib   diameter of chest cavity
25% air that enters during quiet breathing
sternocleidomastoid
scalenes
pectoralis minor
_________________&________________________
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active only when exhalation is forceful
exercise, playing wind instruments
Pressure and volume
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Prior to inhalation, Patm = Palv
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For air to enter alveoli, Palv must be < Patm
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Done by ↑ lung volume
P inversely proportional to volume (P = 1/V)
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Ideal gas law: PV = nRT, P = nRT/V
Intrapleural P is always subatmospheric
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Thoracic cavity volume ↑, slight Intrapleural P 
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Boyle’s Law
Pleurae adhere to each other, pulled outward as expansion occurs
As lung volume ↑, Palv  & air moves to area of  P
Surface tension & compliance
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________________- fluids exert this
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At all air-water interfaces: water-water attraction >watergas attraction
Must be overcome to expand the alveoli
Surfactant reduces compared to pure water
Respiratory distress syndrome (RDS)- lack of surfactant,
collapse alveoli during exhalation, IRDS in infants
__________________- effort required to stretch
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Elasticity and surface tension
 compliance: 1. scar lung tissue, 2. pulmonary edema, 3.
 surfactant, 4. impede expansion (ex- muscle paralysis)
Rate of airflow depends on:
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Pressure difference
Resistance
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Airflow = (Palv-Patm )/R
Larger diameter of airway,  resistance
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Regulated by smooth muscle contraction (symp NS)
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Bronchodilation   resistance
Narrow or obstructed airway  ↑ resistance
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Asthma- usually allergic rxn, bronchi smooth muscle spasms
COPD- chronic obstructive pulmonary disease
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Emphysema or chronic bronchitis
Gas Exchange and Transport
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Basic Properties of Gases
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Dalton’s Law
Henry’s Law
Gas Exchange Between the blood and lungs
Gas Exchange Between the blood and tissues
Oxygen transport
Carbon dioxide transport
Dalton’s Law
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Each gas in a mixture exerts its own pressure
as if there were no other gases present
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Partial pressure (pp)
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Determine the movement of O2 and CO2 between
atmosphere and lungs AND blood and body cells
Diffusion from high to low partial pressure
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> difference in partial pressure  faster the diffusion
Total pressure is the sum of partial pressures
Explains which way O2 and CO2 move from
place to place in the body
Henry’s Law
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Quantity of gas dissolved in a liquid is
proportional to pp of the gas & its solubility
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In body fluids: gas tends to stay in solution when:
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Partial pressure is great
High solubility in water
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CO2 is 24X more soluble than O2  more CO2 dissolved in
plasma
N2 is majority of air BUT very little dissolves in plasma
Hyperbaric oxygenation- use of pressure to cause
more O2 to dissolve in blood
Gas exchange depends upon:
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_________________ differences of the gases
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______________ available for gas exchange
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Emphysema causes alveolar disintegration
__________________
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Altitude sickness
Pulmonary edema slows gas exchange
Molecular weight and solubility of the gases
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 MW usually faster diffusion, but solubility changes that
Hemoglobin and oxygen
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1.5% is dissolved O2
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O2 does not dissolve easily in water
Only this 1.5% can diffuse from blood tissue
98.5% blood O2 is bound to Hb in RBC
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↑ the PO2 , more O2 binds Hb
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Hb completely  Hb-O2 then: fully saturated
> PO2, more O2 will bind Hb
Affinity affects binding
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Dissociation curves
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Shift right = less affinity, shift left = more affinity
Factors affecting Hb affinity for O2
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As acidity ↑ Hb affinity for O2 
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Acidity increases the ability to unload O2
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PCO2 ↑ has same effect as ↑ acidity
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Acidity related to PCO2 : CO2 is converted to carbonic
acid which BECOMES: H+ & bicarbonate ions
↑ temperature  ↑ O2 release from Hb
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Bohr effect- more H2 the more O2 unloaded from Hb
Same effect as ↑ acidity, CO2, BPG
BPG- bisphosphoglycerate  Hb affinity for O2
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Forms when glycolysis is occuring
Fetal hemoglobin
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Hb-F has higher affinity for O2 than Hb-A
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 BPG in metabolically active fetus causes Hb to
 affinity for O2 and release it
Hb-F curve is shifted to the left of Hb-A curve
O2 readily transferred to fetal blood from the
maternal blood in the placenta
Carbon Monoxide poisoning
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CO binds Hb 200x more strongly than O2
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More CO binding reduces O2 carrying capacity
Red lips and muscosa due to Hb bound to CO
Possible to save victim by administering pure
oxygen
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Speeds up separation of CO from Hb
Carbon Dioxide Transport
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Dissolved CO2 – 9%, diffuse into alveolar air
Carbamino compounds – 13%, Hb is a protein
 most CO2 moving this way is Hb bound
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Formation of Hb-CO2 depends on PCO2
Bicarbonate ions – 78%, CO2 diffuses into
systemic capillaries  RBC, rxn w/H2O in
presence carbonic anhydrase  carbonic acid
Bicarbonate ions
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As blood picks up CO2, HCO3- accum in
RBC
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Some HCO3- moves to plasma
In exchange, Cl- moves into RBC = chloride shift
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fig 23.24
Maintain electical balance between plasma & cytosol
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3At lungs, rxns reverse and CO2 is exhaled
Control of Respiration
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_______________- widely dispersed neurons
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Medullary rhythmicity area
Pneumotaxic area in pons
Apneustic area in pons
*The respiratory center is regulated by:
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Cortical influences
Chemoreceptor regulation
Proprioceptors, inflation reflex
Medullary Rhythmicity Area
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Controls basic rhythm of respiration
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Inspiratory area: generates basic rhythm
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2 sec impulse to external intercostals & diaphragm
Muscles contract, inhalation occurs
Relaxation and passive elastic recoil
Expiratory area: inactive during quiet breathing
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During forceful breathing  contraction of internal
intercostals and abs
Decrease size of cavity
forceful expiration
Pons-- Pneumotaxic & apneustic areas
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_____________- coordinate transition between
inhalation & exhalation
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upper pons
Transmits inhibitory impulses inspiratory area
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Turn off lungs before too full of air
Can over ride the apneustic
_________________- also coordinates
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Lower pons
Stimulatory impulse to inspiratory area
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Results in long, deep inhalation
Regulation of Respiratory Center
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Cerebral cortex  resp center  can alter breathing
or refuse to breath for short time
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Chemoreceptors: monitor H+, CO2 and O2
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Build up of CO2 and H+ limits that
↑ PCO2 or H+ strongly stim. inspiratory center
Central: in CNS
Peripheral: in aortic bodies & carotid bodies
Vagal stretch receptors- if overinflation of lungs,
vagus nerve communicates with inspiratory and
apneustic areas, inhibits inspiration (inflation reflex)
More about ventilation rate & depth
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Proprioceptors- exercise  rate & depth ↑
Inflation reflex- stretched during overinflation
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Baro or stretch receptors in bronchi, bronchioles
Limbic system- excite ↑ rate and depth
Temperature  ↑ rate
See table 23.2 on 883
Lung volumes
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Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
vital capacity
Residual volume
Total lung capacity
IRV= VC –(TV+ERV)
fig. 23.17
Smoking
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Nicotine restricts airflow
CO binds Hb & reduces O2 carrying capacity
↑ mucous  restricted airflow
Impair and destroy cilia
Destruction of elastic fibersemphysema
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Collapse bronchioles & trap air after exhale
terms
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Apnea- temporary cessation of breathing
Eupnea- normal quiet breathing
Dyspnea- shortness of breath; painful, labored
Hypernea- abnormally deep or rapid breathing
Cyanosis- blue/purple due to ↑ deoxy-Hb
Hypoxia-  O2 at tissue level (4 types, p882)
Hypercapnia- ↑ in arterial PCO2 above 40
mmHg (aka hypercarbia)