A) deliver oxygen and eliminate carbon dioxide
B) assist in buffering blood pH
II. Respiration
A) exchange of gases (oxygen/carbon dioxide) from atmosphere || blood || tissues
1) pulmonary ventilation - "breathing"; inspiration & expiration
2) external respiration -
a) pulmonary air || blood gas exchange
i) blood gains oxygen, loses carbon dioxide
3) internal respiration -
a) capillary blood || tissues
i) blood loses oxygen, gains carbon dioxide
B) cellular respiration
1) aerobic metabolism for ATP production
III. Respiratory System Anatomy
A) Upper Respiratory Tract (URT)
1) paranasal structures
a) external nares
b) nasal cavity and septum
c) nasal conchae
d) nasal meatuses
e) olfactory epithelium
f) paranasal sinuses
g) ciliated pseudostratified epithelium
2) pharynx
a) internal nares
b) auditory tubes
c) oropharynx
d) laryngopharynx
B) Lower Respiratory Tract (LRT)
1) layrnx
a) thyroid & cricoid cartilage
b) vocal box
c) hyoid
2) trachea
a) "C" rings of cartilage
b) carina
i) receptors sensitive to irritants
ii) initiates cough reflex
c) bronchi
3) lungs (right lung = three lobes; left lung = two lobes)
a) pleural membranes
b) bronchi
c) bronchioles
d) terminal bronchioles
e) smooth muscles within bronchiole walls
i) parasympathetic NS activates (using histamine) bronchiole smooth muscle (constriction)
ii) sympathetic NS inhibits (using epinephrine) bronchiole smooth muscle (dilation)
f) alveolar ducts
g) alveolar sacs
h) alveoli
i) simple squamous lining
ii) septal cells - produce surfactant
iii) macrophage (Kuppfer cells) - remove alveolar irritants, debris
iv) entire alveolar surface area = 750 sqft
v) alveolar surface area site of external respiration
IV. Pulmonary Ventilation
A) Inspiration
1) Boyle's Law: air pressure in closed space inversely correlated with volume
a) increase volume == decrease pressure; decrease volume == increase pressure
2) differences in air pressure between air and lungs drives movement of air into/out of lungs
3) normal inspiration is an ACTIVE process
4) inspiratory muscles involved:
a) diaphragm (75% normal inspiratory action)
i) activated by phrenic nerve
ii) contraction causes diaphram to "flatten"
iii) a 1cm drop in the diaphram decreases pulmonary air pressure 1-3mmHg
iv) this drop in pulmonary air pressure causes approx 0.5L air to move into lungs
b) external intercostals (25% normal inspiratory action)
i) activated by intercostal nerves
c) accessory muscles can also enhance inspiration
i) sternocleidomastoid and scalenes
5) normal breathing ("eupnea") consists of moving approx 0.5L (tidal volume) into/out of lungs
6) not all air inspired actually enters lung
a) anatomic "dead space" (approx 150ml) includes URT and trachea & bronchi
b) ONLY air within alveoli (approx 350ml) can exchange gases
B) Expiration
1) expiration is a passive process
2) relaxation of diaphragm and external intercostals
a) ribs are depressed and diaphragm curves upwards
3) expiration can become active process by contraction of abdominals and internal intercostals
4) major factors driving expiration:
a) elastic recoil of lungs
b) surface tension of alveolar fluid (lessened by surfactant)
5) these factors create high "compliance"
a) compliance refers to ease of lung expansion
b) low compliance from pulmonary scarring, edema, surfactant deficiency (especially in premature babies)
c) compliance too high in emphysema
C) Intrapleural pressure
1) pleural cavity pressure MUST stay approx 4mmHg LESS than intrapulmonary pressure
2) any condition that equalizes intrapleural and intrapulmonary pressures causes immediate lung collapse
a) chest trauma may rupture visceral plura leading to atelectasis ("collapsed lung")
b) collapsed lung is useless for ventilation - can not inspire
c) "pneumothorax" refers to air in intrapleural space, will prevent lung ventilation
d) each lung is in a completely separate pleural cavity, so pneumothorax of one lung does not affect the other
D) Breathing patterns/deficits
1) eupnea - normal breathing pattern (11-15 bpm)
2) dyspnea - painful difficult breathing
3) hypoxia - decrease oxygen delivery to tissues
4) hypercapnia - increase carbon dioxide levels in blood
V. Gas Exchange (external & internal respiration)
A) CO2 and O2 gas exchange
1) Dalton's Law: (concerns pressure of specific gases in mixtures)
a) pressure of specific gas in a mixture determined by % of that gas in the mixture
i) [total atm. pressure] x [gas %] = partial pressure of that gas
b) 760mmHg x 21%O2 = Po2(160mmHg)
c) 760mmHg x 0.04%CO2 = Pco2(0.3mmHg)
d) 760mmHg x 78.6%N2 = Pn2(597mmHg)
e) ** it is the partial pressure of each gas that determines "direction" of diffusion of each gas **
B) Partial Pressures of blood gases
1) atmosphere: Po2=160mmHg, Pco2=0.3mmHg
2) alveolar air: Po2=105mmHg, Pco2=40mmHg
3) oxygenated blood: Po2=100mmHg, Pco2=40mmHg
4) tissues: Po2=40mmHg, Pco2=45mmHg
5) deoxygenated blood: Po2=40mmHg, Pco2=45mmHg
6) ** why less P02 in alveoli than atmosphere
C)Rate of gas diffusion dependant on:
1) partial pressure
a) at sea level, alveolar Po2=160mmHg
b) at 10,000 ft, alveolar Po2=110mmHg
c) at 20,000 ft, alveolar Po2=73mmHg
d) at 50,000 ft, alveolar Po2=18mmHg
2) surface area in lung
a) normally approx. 750sqft
3) diffusion membrane thickness
a) normally appprox. 0.5um, increases with edema, mucus accumulation
4) solubility of gases
D) Henry's Law (concerns factors affecting gas solubility)
1) amount of gas dissolved in liquid depends on partial pressure AND solubility coefficient
2) explains why N2 (Pn2=597mmHg) diffuses very poorly into our blood (low solubility)
3) ** if total pressure increases, Pn2 will increase = increase amount dissolved in blood
4) scuba divers underwater have more N2 in blood because of increased deep sea pressure
a) rapid surfacing causes this dissolved N2 to "bubble out" of blood (like opening can of soda)
b) decompression sickness ("bends") can cause air embolisms to form in blood
E) O2 and CO2 in blood
1) 1.5% O2 dissolved in blood
2) 98.5% O2 carried by hemoglobin (Hb-O2)
a) Hb can carry up to four molecules of O2 (four = saturation)
b) Po2 determines Hb saturation
c) also pH, temperature and Pco2 affects Hb-O2 binding
d) ** review O2-hemoglobin dissociation curves for Po2, Pco2, pH & temp.
e) "Bohr effect" describes oxygen unloading (dissociation) where low pH exists
i) enhances oxygen delivery in tissues with increased metabolism
3) 7% CO2 dissolved in blood
4) 23% CO2 bound by Hb
5) 70% CO2 in form of HCO3-
