GAS EXCHANGEIB TOPIC 6.4

CARDIOPULMONARY SYSTEM

CARDIOPULMONARY SYSTEM

Branch from the pulmonary vein (oxygen-rich blood)

Terminal bronchiole

Branch from the pulmonaryartery(oxygen-poor blood)

Alveoli

Colorized SEMSEM

50 µ

m

50 µ

m

Heart

Left lung

Nasal cavity

Pharynx

Larynx

Diaphragm

Bronchiole

Bronchus

Right lung

Trachea

Esophagus

TERMS TO KNOW

GAS EXCHANGE

• ventilation • alveoli • capillaries • partial

pressure

• 6.4.U1 ventilation maintains concentration gradients of O2 & CO2 between air in alveolar sacs and blood flowing through adjacent capillaries

• compare: • ventilation, gas exchange, cellular respiration

PARTIAL PRESSURESA CLOSER LOOK

LUNG CAPACITY

• What is your vital capacity?

TERMS TO KNOW

GAS EXCHANGE - CELL SPECIALIZATION

• pneumocyte

• surfactant

• adhesion

• surface tension

• 6.4.U2 Type 1 pneumocytes are thin alveolar cells that are adapted to carry out gas exchange

• 6.4.U3 Type 2 pneumocytes secrete a surfactant solution: • keeps surface moist • prevents internal adhesion of alveolus

PULMONARY SURFACTANT

CLOSER LOOK:

• Phospholipoprotein produced by Type 2 pneumocytes

• it facilitates hydrophyllic adsorption in water on alveolar surface

• hydrophobic region orients towards air

• reduces surface tension, easing inflation and resisting collapse of alveolus

TERMS TO KNOW

GAS EXCHANGE - STRUCTURE AND FUNCTION

• trachea • bronchi • bronchioles

• 6.4.U4 Air is carried to the lungs in the trachea and bronchi and then to the alveoli in the bronchioles

USES DIFFERENT MUSCLES FOR INSPIRATION AND

EXPIRATION

BREATHING

TERMS TO KNOW

GAS EXCHANGE - STRUCTURE AND FUNCTION

• thorax • inspiration • expiration • intercostal

muscles • diaphragm • antagonistic

muscles

• 6.4.U5 Muscle contractions cause pressure changes inside the thorax that force air in and out of lungs to ventilate them

• 6.4.U6 Different muscles are required for inspiration and expiration because muscles only do work when they contract

TERMS TO KNOW

GAS EXCHANGE - STRUCTURE AND FUNCTION

• inspiration • expiration • intercostal

muscles • diaphragm • antagonistic

muscles

• 6.4.A3 Ventilation uses antagonistic muscle groups• Principal muscles of inspiration:

• diaphragm (flattens and moves down) • external intercostals (move rib cage up and out) • neck muscles (pull up)

• Principal muscles of expiration: • abdominal wall

(e.g. rectus abdominis (6-pack)

• internal intercostals

GAS EXCHANGE - DISORDERS• IRDS: Infant Respiratory Distress Syndrome

• insufficient surfactant production during last part of gestation

• incidence: 50% of infants born at 26-28 weeks, 25% at 30-31 weeks

• #1 cause of death of premature birth infants • treated with breathing tube + surfactant (synthetic

or from animal)

O2 DISSOCIATION CURVES• D.6.U1 Oxygen dissociation curves show hemoglobin’s affinity for Oxygen

• RBCs have hemoglobin (Hb) • Hb = 4 polypeptide chains, ea. w/ a

heme group carrying Iron (Fe) • ea. heme group reversibly binds to one

O2 molecule • As each O2 binds, Hb affinity for the next

O2 increases •thus high affinity for O2 in lungs

(=loading) •thus low affinity for O2 in muscles

(=unloading)

TRANSPORT OF CO2• CO2 is carried in plasma and by Hb • CO2 in the RBCs is turned into carbonic acid

• most CO2 is carried in RBC • Hb buffers the pH by absorbing H+ ions

O2 DISSOCIATION CURVES• D.6.U5 Chemoreceptors are sensitive to blood pH•CO2 in plasma may combine with H2O to form carbonic acid (H2CO3)

•Chemoreceptors (in medulla) detect pH and trigger body responses to keep homeostasis • lungs: change respiratory rate • kidneys: control reabsorption/excretion of

bicarbonate (HCO3) •blood pH is buffered by plasma proteins • normal range: 7.35 - 7.45

O2 DISSOCIATION CURVES• D.6.U4 The Bohr shift explains the increased unloading of O2 in respiring tissues•increased respiration makes more CO2 •what happens to pH in RBC? •lower pH decreases Hb affinity for O2

CAN YOU SKETCH:

CHALLENGES

• Dissociation curves for:

• fetal Hb?

• Llama Hb?

• myoglobin?

• Hb at higher temp?

WHY DO PEOPLE GET LIGHTHEADED?

HYPERVENTILATION

• Normally: approx. 10% of air exchanged w/ ea. breath

• hyperventilation exchanges more gas with air,

• thus: less CO2 in body and less in blood

• Normally: if high CO2 in blood, low O2

• and blood vessels in brain dilated (why?)

• If low CO2 (eg. hyperventilation) then b.v. constricted.

• result: less O2, fainting

TERMS TO KNOW

GAS EXCHANGE - DISORDERS

• cancer • metastasis

• 6.4.A1 Causes and consequences of lung cancer • abnormal growth of lung tissue

• tumors may metastasize • initial causes include:

• smoking • asbestos • air pollution • genetics

GAS EXCHANGE - DISORDERS• 6.4.A3 Causes and consequences of emphysema

• alveolar walls lose elasticity • alveoli enlarge; effect on surface area?

• decreases • holes may develop between alveoli • major cause: smoking

• phagocytes brought to lungs • enzyme elastase breaks down walls