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The Respiratory SystemChapter 23
Functions of the Respiratory System Pulmonary __________ - provides for gas
exchange Intake of O2
Elimination of CO2
Helps to __________________ Receptors for _________, _________ inspired
air, _____________ vocal sounds, and __________ small amounts of water and heat
Gas exchange Pulmonary ventilation- breathing
Inhalation (_________) & exhalation (___________) of air between atmosphere and alveoli of lungs
External respiration- (____________) Exchange of gases between alveoli and blood in
pulmonary capillaries across respiratory membrane Blood gains O2, loses CO2
Internal respiration- (______________) Blood systemic capillaries and tissue cells Blood loses O2, gains CO2
Cells consume O2 ATP = cellular respiration
Anatomy of the Respiratory System _______________ Zone- filter, warm, moisten air
Nose Pharynx Larynx Trachea Bronchi & Subdivisions
______________________- gas exchange Alveolar ducts, sacs, alveoli
Pleural membrane- 1 for each lung Visceral pleura- deep, covers lungs Parietal pleura- superficial, lines thoracic cavity Pleural cavity- contains pleural fluid causing:
Reduction of friction Increases surface tension
Pleurisy/pleuritis = inflammation of pleural mem. Pain due to friction between layers If persists pleural effusion
Pneumothorax - cavity filled with air
Cells of the alveoli Type I cells – ___________________, nearly
continuous w/alveolar lining Type II cells – _________, fewer, produce surfactant
Round or cuboidal, free surfaces w/microvilli Alveolar fluid keeps surface between cells & air moist
Surfactant – complex mix of phospholipids and lipoproteins 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 fig 23.12 Together these create – ___________________
O2 & CO2 easily diffuse back & forth These gases will move due to pressure difference Move from high to low pressure
Consist of 4 layers: Alveolar wall- type I & II alveolar cells, macrophages Epithelial basement membrane Capillary basement membrane Capillary endothelium
Only _____________ thick
Musculature in breathing ___________- most imp inhalation muscle
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) _________________-2nd most important- inhalation
when contract elevate rib diameter of chest cavity 25% air that enters during quiet breathing
Others- involved in labored inhalation only: sternocleidomastoid scalenes pectoralis minor
_________________&________________________ active only when exhalation is forceful exercise, playing wind instruments
Pressure and volume Prior to inhalation, Patm = Palv
For air to enter alveoli, Palv must be < Patm
Done by ↑ lung volume P inversely proportional to volume (P = 1/V)
Boyle’s Law Ideal gas law: PV = nRT, P = nRT/V
Intrapleural P is always subatmospheric Thoracic cavity volume ↑, slight Intrapleural P
Pleurae adhere to each other, pulled outward as expansion occurs
As lung volume ↑, Palv & air moves to area of P
Surface tension & compliance ________________- fluids exert this
At all air-water interfaces: water-water attraction >water-gas 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
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: Pressure difference Resistance
Airflow = (Palv-Patm )/R
Larger diameter of airway, resistance Regulated by smooth muscle contraction (symp NS)
Bronchodilation resistance
Narrow or obstructed airway ↑ resistance Asthma- usually allergic rxn, bronchi smooth muscle spasms COPD- chronic obstructive pulmonary disease
Emphysema or chronic bronchitis
Gas Exchange and Transport Basic Properties of Gases
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 Each gas in a mixture exerts its own pressure
as if there were no other gases present Partial pressure (pp)
Determine the movement of O2 and CO2 between atmosphere and lungs AND blood and body cells
Diffusion from high to low partial pressure > 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 Quantity of gas dissolved in a liquid is
proportional to pp of the gas & its solubility In body fluids: gas tends to stay in solution when:
Partial pressure is great High solubility in water
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: _________________ differences of the gases
Altitude sickness ______________ available for gas exchange
Emphysema causes alveolar disintegration __________________
Pulmonary edema slows gas exchange Molecular weight and solubility of the gases
MW usually faster diffusion, but solubility changes that
Hemoglobin and oxygen 1.5% is dissolved O2
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 ↑ the PO2 , more O2 binds Hb
Hb completely Hb-O2 then: fully saturated
> PO2, more O2 will bind Hb Affinity affects binding
Dissociation curves Shift right = less affinity, shift left = more affinity
Factors affecting Hb affinity for O2 As acidity ↑ Hb affinity for O2
Acidity increases the ability to unload O2 Bohr effect- more H2 the more O2 unloaded from Hb
PCO2 ↑ has same effect as ↑ acidity Acidity related to PCO2 : CO2 is converted to carbonic acid
which BECOMES: H+ & bicarbonate ions ↑ temperature ↑ O2 release from Hb
Same effect as ↑ acidity, CO2, BPG BPG- bisphosphoglycerate Hb affinity for O2
Forms when glycolysis is occuring
Fetal hemoglobin Hb-F has higher affinity for O2 than Hb-A
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 CO binds Hb 200x more strongly than O2
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 Speeds up separation of CO from Hb
Carbon Dioxide Transport Dissolved CO2 – 9%, diffuse into alveolar air Carbamino compounds – 13%, Hb is a protein
most CO2 moving this way is Hb bound 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 fig 23.24 As blood picks up CO2, HCO3- accum in RBC
Some HCO3- moves to plasma
In exchange, Cl- moves into RBC = chloride shift Maintain electical balance between plasma & cytosol
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
At lungs, rxns reverse and CO2 is exhaled
Control of Respiration _______________- widely dispersed neurons
Medullary rhythmicity area Pneumotaxic area in pons Apneustic area in pons
*The respiratory center is regulated by: Cortical influences Chemoreceptor regulation Proprioceptors, inflation reflex
Medullary Rhythmicity Area Controls basic rhythm of respiration
Inspiratory area: generates basic rhythm 2 sec impulse to external intercostals & diaphragm Muscles contract, inhalation occurs Relaxation and passive elastic recoil
Expiratory area: inactive during quiet breathing During forceful breathing contraction of internal
intercostals and abs Decrease size of cavity forceful expiration
Pons-- Pneumotaxic & apneustic areas _____________- coordinate transition between
inhalation & exhalation upper pons Transmits inhibitory impulses inspiratory area
Turn off lungs before too full of air Can over ride the apneustic
_________________- also coordinates Lower pons Stimulatory impulse to inspiratory area
Results in long, deep inhalation
Regulation of Respiratory Center Cerebral cortex resp center can alter breathing
or refuse to breath for short time Build up of CO2 and H+ limits that ↑ PCO2 or H+ strongly stim. inspiratory center
Chemoreceptors: monitor H+, CO2 and O2 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
Proprioceptors- exercise rate & depth ↑ Inflation reflex- stretched during overinflation
Baro or stretch receptors in bronchi, bronchioles Limbic system- excite ↑ rate and depth Temperature ↑ rate See table 23.2 on 883
Lung volumes fig. 23.17 Tidal volume Inspiratory reserve volume Expiratory reserve volume vital capacity Residual volume Total lung capacity IRV= VC –(TV+ERV)
Smoking Nicotine restricts airflow CO binds Hb & reduces O2 carrying capacity ↑ mucous restricted airflow Impair and destroy cilia Destruction of elastic fibersemphysema
Collapse bronchioles & trap air after exhale
terms 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)