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)