The Respiratory System• Supplies O2 to blood

and gets rid of CO2

• Consists of– Nose and nasal cavity– Throat (pharynx)– Voice box (larynx)– Windpipe (trachea)– Bronchial tubes– Lungs

Functions of the Respiratory System

• Cleaning and filtering air

• Ventilation

• Gas exchange

• Gas transport

• Smell

• Speech

Respiratory System Anatomy

• Upper respiratory system (tract)– Nose and nasal cavity– Pharynx = throat

• Lower respiratory system (tract) – Larynx = voicebox– Trachea = windpipe– Bronchi = airways– Lungs

• Refer to locations of infections

Trachea

• Five inches long & one inch in diameter

• Extends from larynx into chest where it divides to form two bronchi(us)

• 16 to 20 incomplete C-shaped cartilage rings

• Lined with pseudostratified epithelium

Trachea---------------

Bronchus--------------------------- --------------Bronchus

Gross Anatomy of Lungs

• Base, apex, cardiac notch• Oblique & horizontal fissure in right lung results in 3 lobes• Oblique fissure only in left lung produces 2 lobes

Lung Lobules• Lung lobules are smaller

compartments within lobes• Consist of

– Terminal bronchiole supplies air to lobule

– Each terminal bronchiole divides into several respiratory bronchioles

– Respiratory bronchioles divide into alveolar ducts

– Alveolar ducts supply air to alveolar (air) sacs

– Each sac composed of two or more smaller alveoli(us)

– Extensive blood supply

---alveolar sac

-------alveolus

---terminal bronchiole

---respiratory bronchiole

alveolar duct---------------------

Details of Respiratory Membrane

• Four tissue layers & two fluid layers make the respiratory membrane.

Respiratory PhysiologyVentilation, Gas Exchange, Gas Transport and Control of Ventilation

Pulmonary (alveolar) Ventilation

• Basic concepts and definitions – Ventilation called negative draft ventilation– Breathing in called inspiration or inhalation– Breathing out called expiration or exhalation– Pressure within the lung called alveolar pressure– Pressure within the pleural cavities called intrapleural

pressure – always less than atmospheric pressure. Keeps lungs attached to chest wall and inflated

Breathing or Pulmonary VentilationQuiet Ventilation - Eupnea

• Air moves into lungs when pressure inside lungs is less than atmospheric pressure– Contraction of diaphragm and rib muscles

(external intercostals) enlarges chest and reduces alveolar pressure to below atmospheric pressure

– Air drafts into lungs – negative draft– inspiration or inhalation

Breathing or Pulmonary Ventilation

• Air moves out of lungs when pressure inside lungs is greater than atmospheric pressure– Diaphragm and rib muscles (ext. Intercostals) relax– Chest gets smaller– Elastic recoil of alveoli creates Alveolar pressure

greater than atmospheric pressure – Air is pushed (squeezed) out of lungs– Expiration or exhalation

Drawing of Ventilation Cycle

Animation of Ventilation

Boyle’s Law and Ventilation

• As size of container increases, pressure inside decreases

• As the size of closed container decreases, pressure inside is increased

Forced Ventilation During Exercise

• Forced inspiration– Require larger decreases in intrapleural and

alveolar pressures– Diaphragm and external rib muscles contract more

forcefully making the chest wider.– Other back muscles become involved – Results in deeper breaths

Forced Ventilation During Exercise

• Forced Expiration– Require larger increases in intrapleural and alveolar

pressures– Diaphragm and external intercostal rib muscles relax– Internal intercostal rib muscles contract compressing

rib cage making the chest narrower.– Abdominal muscles contract compressing abdomen

forcing diaphragm to move up further– Air forced out

Lung Volumes and Capacities

• Volume is one measure of quantity of air

• Capacity is sum of two or more volumes

• Spirometer or respirometer device for measuring volumes and capacities

• Record called spirogram

Lung Volumes and Capacities

• Ventilation rate is number of breaths per minute

• Resting ventilation rate averages12 breaths per minute (Range 12 to 20 breaths / minute)

• Tidal Volume (VT) is amount of air in one breath

• Resting tidal volume is about 500 mL

Lung Volumes and Capacities

• If resting tidal volume (VT) = 500 mL, then

• 350 mL reaches alveoli

• Remaining 150 mL remains in conducting airways above alveoli– Called anatomic dead air– Dead air does not participate in gas exchange

• The 350 mL in alveoli is the only air participating in gas exchange

Lung Volumes and Capacities

• Lung volumes(1) Tidal Volume (Vt) Volume of air in one breath

(2) Inspiratory Reserve Volume (IRV) Volume of air inspired in addition to VT

(3) Expiratory Reserve Volume (ERV) Volume of air expired in addition to VT

(4) Residual Volume (RV) Volume of air that cannot be expired even with maximum forced expiration.

Lung Volumes and Capacities

• Lung Capacities:

(1) Inspiratory Capacity (IC) = Vt + IRV

(2) Functional Residual Capacity:

(FRC) = RV + ERV

(3) Vital Capacity (VC) = Vt + IRV + ERV

(4) Total Lung Capacity (TLC) = VC + RV

Lung Volumes and Capacities

– FEV1 stands for forced expiratory volume in one second

• Percentage of vital capacity expired in 1 second

• Should be 75% or higher

• If not, may indicate chronic obstructive pulmonary disease such as chronic bronchitis or emphysema

Spirogram

Gas exchange

• In lungs – External respiration– Diffusion of O2 from alveolar air into blood

– Diffusion of CO2 from the blood into alveolar air

• In tissues – Internal respiration – Diffusion of O2 from blood into tissues

– Diffusion of CO2 from tissues into blood

• Diffusion across the extremely thin respiratory membrane from higher to lower concentrations of gases

Gas Exchange Diagram

O2

O2

CO2

CO2O2

CO2

Oxygenated BloodAlveolus

Tissues

O2

O2

CO2

CO2

O2

CO2Deoxygenated Blood

External Respiration Internal Respiration

Measurements of Gas Concentrations

• Dalton’s Law of Partial Pressure– In a mixture of gasses, the total pressure is

equal to the sum of pressures contributed by each individual gas

– These individual pressures are partial pressures

– Symbol for the partial pressure of a gas is Pg

where g stands for the specific gas

Measurements of Gas Concentrations

• Partial pressures– Our atmosphere is mixture of nitrogen, oxygen,

argon, carbon dioxide and other trace gasses– Total pressure of our atmosphere is essentially

equal to PN2 + PO2 + PAr + PCO2

Measurements of Gas Concentrations

• Partial pressures– Since Oxygen (O2) = 21% of our atmosphere,

its PO2 = 0.21 x 760 = 159 mm Hg

– Since CO2 = 0.04% of our atmosphere, its

PCO2 = 0.0004 x 760 = 0.3 mm Hg

– O2 and CO2 are the most important respiratory

gases, so their partial pressures are used in our discussion of gas exchange

Partial Pressures and Gas Exchange

• Partial pressure of O2 and CO2 in oxygenated blood

– PaO2 is symbol for partial pressure of oxygen in oxygenated (arterial ) blood and is about 95 mm Hg

– PaCO2 is symbol for partial pressure of carbon dioxide in oxygenated (arterial) blood and is about 40 mm Hg

Partial Pressures and Gas Exchange

• Partial pressure of O2 and CO2 in deoxygenated venous blood

– PvO2 is symbol for partial pressure of oxygen in deoxygenated (venous) blood and is about 40 mm Hg

– PvCO2 is symbol for partial pressure of carbon dioxide in oxygenated (venous) blood and is about 45 mm Hg

Gas Exchange Diagram

O2

O2

CO2

CO2

PaO2=95 mm Hg

PaCO2=40 mm Hg

Oxygenated BloodAlveolus

Tissues

O2

O2

CO2

CO2

PvO2=40 mm HgPvCO2=45 mm Hg

Deoxygenated Blood

External Respiration Internal Respiration

Henry’s Law and Gas Exchange

• More oxygen in the air, results in more oxygen in the blood

• Formally stated– The amount of gas that will dissolve in a liquid

is proportional to:- (1) Partial pressure of the gas

(2) Solubility of the gas in the liquid (3) Temperature of the liquid

Gas TransportGas Pickup and Delivery

Oxygen Transport

• 98.5% of O2 carried by iron of hemoglobin

• Only 1.5% dissolves in plasma

• Hemoglobin (Hb) picks-up oxygen in lungs and delivers it to tissues– Becomes oxyhemoglobin (Hb-O2) when picks-up O2

– Becomes deoxyhemoglobin (Hb-H) when O2

delivered

Hemoglobin Molecule

•Each Hb molecule has four heme groups, and each heme contains an iron atom (Fe++)

•Iron has affinity for O2

•This affinity greater in lungs than in tissues.

Oxygen Saturation

– Hb molecule saturated when its iron binds four O2 molecules

– Hb unsaturated if iron has no O2 molecules

– Percent saturation refers to how many irons of the Hb molecules have O2

– Arterial blood has the higher percent saturation

Loading and Unloading

• Pick-up of O2 in lungs called loading

• Delivery of O2 to tissues called unloading

Factors in O2 Loading and Unloading

(1) PO2 main factor in O2 loading and unloading

– Higher Po2 in lungs favors loading

• In lung capillaries Po2 is high and O2 binds to Hb

– Lower PO2 in tissues favors unloading

• In tissue capillaries PO2 is low and Hb-O2 releases O2

• In resting person, nearly 25% of O2 unloaded

Other Factors in Loading and Unloading

(2) Acid• Lower pH of tissues capillaries favors unloading

– Hemoglobin has less affinity for O2 at lower pH– Bohr Effect

• Higher pH of lungs capillaries favors loading– Hb has higher affinity for O2 at higher pH

Other Factors continued

(3) PCo2

– Higher PCo2 of tissue capillaries favors unloading– Related to pH as follows:

• Carbon dioxide + water carbonic acid or• CO2 + H2O H2CO3 H+ + HCO3

-

• CO2 forms acid when dissolved in water

(4) Temperature– Higher temperature of tissues favors unloading– Lower temperature of lungs favors loading

Other Factors continued

(5) BPG (2,3 bisphosphoglycerate) – When BPG binds to hemoglobin in tissue

capillaries, Hemoglobin loosens its grip on O2

– More O2 released into tissues

– Higher metabolic rate, higher altitude and certain hormones increase BPG formation

Oxygen Transport Diagram

O2

Hb-O2

Hb-H

Oxyhemoglobin Alveolus

Tissues

O2

Hb-H

Deoxyhemoglobin

External Respiration Internal Respiration

Hb-O2

Hb-O2

Hb-HAerobic Cell Respiration

Loading

•Higher Po2

•Higher pH

•Lower Temp

UnLoading

•Lower Po2

•Lower pH

•Higher Temp

BPG

Fetal Hemoglobin & Oxygen Affinity

• Differs from adult hemoglobin in structure & affinity for binding O2

• Maternal blood in placenta has less O2 than normal oxygenated blood

• When Po2 is low, fetal hemoglobin can still bind enough O2

Carbon Monoxide Poisoning

• CO from car exhaust & tobacco smoke

• Binds to iron on the Hb heme group 250 times more strongly than O2

• CO poisoning

• Treat by administering pure O2

CO2 Transport

(1) 7% dissolves in plasma

(2) 23% becomes Hb-CO2 carbaminohemoglobin

(3) 70% converted to bicarbonate (HCO3

-

and most bicarbonate transported in plasma as sodium bicarbonate

70% Converted to bicarbonate

Control of Ventilation• Medullary rhythmicity Neurons in the

Medulla Oblongata• Inspiratory Area

– Controls basic rhythm of respiration– Inspiration for 2 seconds, expiration for 3– Autorhythmic cells active for 2 seconds then inactive

• Expiratory Area– Inactive during most quiet breathing only active

during forced ventilation

Control of Ventilation

• Neurons in the Pons coordinate transition between inhalation and exhalation– Apneustic area stimulates inhalation resulting

in prolonged inhalation– Pneumotaxic area inhibits inspiration before

lungs can become over-inflated

Respiratory Centers

Factors Affecting Breathing

(1) CO2

– Hypercapnia (increase in CO2) excites chemoreceptors in carotid arteries, aorta and medulla oblongata and breathing rate increases

(2) O2

– Hypoxia (decrease in O2) such as at high altitude causes imcreased breathing rate

Factors Affecting Breathing

(3) Proprioceptors– Muscle contraction and joint movement

increase during exercise – Increased stimulation of proprioceptors quickly

increases breathing rate– Happens as soon as you start to exercise

Factors Affecting Breathing

(4) Inflation (Hering-Breuer) Reflex– As lungs over-inflate, stretch receptors become

excited– Increase in nerve impulses to pons and medulla

inhibits apneustic and inspiratory area– Inhalation stops before lungs can be damaged

(5) Conscious Control: Intentional breathing

Clinical Terms

• Apnea: No breathing

 

• Hyperventilation: Rapid breathing

• Hypoventilation: Slow breathing

• Orthopnea: Labored breathing when lying

down flat and is relieved by sitting up.

Clinical Terms

• Dyspnea: painful breathing

• Chronic obstructive pulmonary diseases (COPD's)

• Emphysema

• Chronic bronchitis

Clinical Terms

• Tuberculosis

• Pneumonia

 

• Lung cancer