IB TOPIC 6.4 GAS EXCHANGE

Transcription

1 IB TOPIC 6.4 GAS EXCHANGE

2 CARDIOPULMONARY SYSTEM

3 CARDIOPULMONARY SYSTEM Branch from the pulmonary artery (oxygen-poor blood) Branch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Pharynx Left lung Larynx Alveoli 50 µm Esophagus Trachea 50 µm Right lung Bronchus Bronchiole Diaphragm Heart SEM Colorized SEM

4 GAS EXCHANGE TERMS TO KNOW ventilation alveoli capillaries partial pressure compare: ventilation, gas exchange, cellular respiration 6.4.U1 ventilation maintains concentration gradients of O2 & CO2 between air in alveolar sacs and blood flowing through adjacent capillaries

5 A CLOSER LOOK PARTIAL PRESSURES

6 LUNG CAPACITY What is your vital capacity?

7 GAS EXCHANGE - CELL SPECIALIZATION TERMS TO KNOW pneumocyte surfactant adhesion surface tension hydrophyllic 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

8 CLOSER LOOK: PULMONARY SURFACTANT 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

9 GAS EXCHANGE - STRUCTURE AND FUNCTION TERMS TO KNOW 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

10 BREATHING USES DIFFERENT MUSCLES FOR INSPIRATION AND EXPIRATION

11 GAS EXCHANGE - STRUCTURE AND FUNCTION TERMS TO KNOW 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

12 GAS EXCHANGE - STRUCTURE AND FUNCTION TERMS TO KNOW 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 (6pack) internal intercostals

13 GAS EXCHANGE - DISORDERS IRDS: Infant Respiratory Distress Syndrome insufficient surfactant production during last part of gestation incidence: 50% of infants born at weeks, 25% at weeks #1 cause of death of premature birth infants treated with breathing tube + surfactant (synthetic or from animal)

14 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)

15 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

16 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:

17 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

18 CHALLENGES C AN YOU SKETC H: Dissociation curves for: fetal Hb? Llama Hb? myoglobin? Hb at higher temp?

19 HYPERVENTILATION WHY DO PEOPLE GET LIGHTHEADED? Normally: approx. 10% of air exchanged w/ ea. breath hyperventilation exchanges more gas with air, Normally: if high CO2 in blood, low O2 thus: less CO2 in body and less in blood and blood vessels in brain dilated (why?) If low CO2 (eg. hyperventilation) then b.v. constricted. result: less O2, fainting

20 GAS EXCHANGE - DISORDERS TERMS TO KNOW 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

21 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