The Plan Introduction – general concepts Anatomy Mechanics – moving air into the lungs –Structures, pressure changes Gas Exchange – moving air from the lungs to blood and tissues –Moving O 2 in and CO 2 out of tissues Control mechanisms –Local –CNS 1

Readings - Respiratory McKinley, O’Loughlin, and Bidle, Anatomy and Physiology An integrative Approach, p Mechanics ;

Objectives Describe briefly the embryological origin of lungs. Explain the pleural sac and intrapleural pressure. Describe the mechanics of breathing including the structures used to elicit quiet and forced breathing. Describe the concept of pulmonary ventilation. Describe the parameters used to measure pulmonary performance. Describe Boyle’s law, intrapulmonary pressure, respiratory minute volume, alveolar dead space, tidal volume, and alveolar ventilation. 3

4 Mechanics of breathing Respiratory system III: Mechanics of breathing How do you breathe? 1.Structures involved -embryonic development of the lung -muscles, bones and elastic fibers 2. Pulmonary ventilation - changing volumes and changing pressures 3. Physiology of pulmonary performance - how much work can you lungs really do? - what is the full lung capacity?

5 Early development of the Lungs Pharynx Lung bud

6 Tracheo-esophageal septum Lateral view Anterior view

7 Demonstration: As the lung bud grows, it enters a sac and it is surrounded by 2 layers of that sac (membranes) but the lungs remain outside the sac – a pattern similar to development of the heart pericardial sac. The membranes forms the visceral and parietal pleura

8 Branching of secondary bronchi: 17X in utero and 6X postnatally = 8.4 million bronchioles per lobe. Newborn lung has only 6-15% of the adult complement of alveoli. Full complement of alveoli is developed by about 2 years after birth. Microvascular development continues between 2 – 5 years after birth.

9 Anatomy of the lungs Parietal pleura Visceral pleura

10 The pleural sacs (they’re in the thoracic cavity) Parietal pleura attached to the thoracic cavity; secretes fluid Visceral pleura attached to the lung; resorbs fluid Negative pressure in the pleural space Elastic fibers in lung recoil (push out) All keep the lung inflated & facilitate lung movement Pleural effusion (increase in fluid) and dehydration are pathological

11 Pulmonary Ventilation The Intrapleural Pressure –Pressure in space between parietal and visceral pleura (see red line) –Pleural fluid (minimal volume) –Averages - 4 mm Hg –Maximum of -18 mm Hg –Remains below atmospheric pressure (P atm ) = 760mm Hg throughout respiratory cycle –Intrapulmonary pressure or pressure in resting alveoli = 760mm Hg

Pneumothorax (traumatic) –there are other types Symptoms –sudden, sharp chest pain; 1 side or other, but not in the center –SOB –feeling of tightness in your chest –rapid heart rate –(hole in your chest) –needle/tube decompression until lung is re-inflated –seal hole 12 Air (atmospheric) enters pleural space – between your lungs and chest wall – pressure changes

13 Lungs can not move by themselves heart right lung left lung anterior Spinal column Copyright 2009 Pearson Education Inc. publishing as Pearson Benjamin Cummings - not much space to expand - parietal pleura attached to thoracic wall

14 Lung in a bottle

15 Diaphragm Diaphragmatic surface

16 Introduction to External Respiration The Processes of External Respiration (air from the atmosphere to cells undergoing metabolism, ie muscles, etc.) –Pulmonary ventilation (breathing) bringing air into the lungs from the environment –Gas exchange across alveolar membranes lung air space to capillaries to RBC cytoplasm –Transport of O 2 and CO 2 : movement via RBCs in alveolar capillaries movement via RBCs in capillary beds systemically and to target tissues (muscle, etc.) –Gas exchange from systemic capillaries RBC cytoplasm in systemic capillaries to interstitium/cells

17 Pulmonary Ventilation Requires movement of rib cage by respiratory muscles The Mechanics of Breathing –Inhalation Always active – requires skeletal muscle contraction –Exhalation Passive or active The Respiratory Muscles –Most important are: The diaphragm External intercostal muscles of the ribs Accessory respiratory muscles: –activated when respiration increases significantly

Inhalation, Exhalation and the Thoracic cavity 18

19 Pulmonary Ventilation: quiet vs forced The Mechanics of Breathing Quiet Inhalation –Active – diaphragm and external intercostal muscles Quiet Exhalation –Passive (allow muscle groups to relax) Forced inhalation (active) –the diaphragm –external intercostal muscles –accessory respiratory muscles: activated when respiration increases significantly Forced exhalation (active) –accessory respiratory muscles: activated when respiration increases significantly

20 Accessory Muscles for Respiration: Inspiration Expiration

21 Review Inhalation –Active contraction of diaphragm and external intercostal muscles ~ quiet breathing –increases size of thoracic cavity (increases volume of rib cage and lungs) –Forced inspiration requires: diaphragm and external intercostals and 5 accessory muscles Exhalation –Passive relaxation of diaphragm and external intercostal muscles ~ quiet breathing –decreases size of thoracic cavity –Forced exhalation requires 4 accessory muscles

22 Basic principles of Pulmonary ventilation Lungs do not move independently –muscle movement alone does not allow one to breathe (lifting weights; running, etc.) –Movement of specific muscles is required Contraction and relaxation of muscles associated with the chest cause changes in the volume of the thoracic cavity and lung volume Changes in volume causes change in pressure Gas (air) will flow from a higher pressure into a lower pressure or down a concentration gradient.Gas (air) will flow from a higher pressure into a lower pressure or down a concentration gradient.

23 Decrease volume, pressure rises Increase volume, pressure falls Normal conditions – a container with molecules of gas decrease volume increase volume

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Area B decreases in volume and increases in pressure. Air moves from area B into area A Area B increases in volume and decreases in pressure. Air moves from area A into area B Pressure A = Pressure B No net movement of air (b) Pressure gradients Area B Area A Volume B Airflow Volume BDecreased pressure B Area B Increased pressure B Area B Volume and Pressure changes in the lungs

25 Pulmonary Ventilation Boyle recognized relationship between pressure and volume : P = 1/V –In a contained gas External pressure forces molecules closer together – volume decreases Movement of gas molecules exerts pressure on container – pressure increases Boyle’s Law (1662) – predicts the result of introducing a change in volume or pressure to the initial state of a fixed quantity of gas – commonly written PV = k (constant) –Defines the relationship between gas pressure and volume: –In the same container... p 1 V 1 = p 2 V 2 Example: Volume = 2 so P =1/2 (0.5) Volume = 10.. P = 1/10 (0.1)

Boyle’s gas law: Relationship of Volume and Pressure –At a constant temperature, the pressure (P) or a gas decreases if the volume (V) of the container increases, and vice versa –P 1 and V 1 represent the initial conditions and P 2 and V 2 the changed conditions –P 1 V 1 = P 2 V 2 –Inverse relationship between gas pressure and volume Figure 23.21a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Boyle’s Law Pressure decreases as volume increases Pressure increases as volume decreases Decreased volume Increased pressure Decreased pressure Increased volume

27 Pulmonary Ventilation A Respiratory Cycle consists of: –one inspiration (inhalation) & –one expiration (exhalation) Pressure and Airflow to the Lungs –Air flows from area of higher pressure to area of lower pressure –Changes in the volume of thoracic cavity With expansion or contraction of diaphragm & rib cage –Causes changes in volume that create changes in pressure Atmospheric pressure (P atm ) = 760mm Hg at sea level

Atmosphere Atmospheric pressure (760 mm Hg) Pleural cavity (intrapleural pressure) = 756mm Hg Alveolar volume of lungs (intrapulmonary pressure) = 760mm Hg (c) Volumes and pressures with breathing (at the end of an expiration) 760 mm Hg 756 mm Hg Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Intrapulmonary pressure during the resting phase – (no breathing)

3 4 Intrapulmonary pressure = atmospheric pressure Quiet expiration atm = 760 mm Hg 754 mm Hg (Intrapleural pressure) 760 mm Hg Intrapulmonary pressure becomes greater than atmospheric pressure; air flows out Air flows out (~500 mL per quiet breath) Pleural cavity volume decreases intrapleural pressure increases Alveolar volume decreases intrapulmonary pressure increases 761 mm Hg 756 mm Hg atm = 760 mm Hg 1 2 Intrapulmonary pressure = atmospheric pressure Quiet inspiration atm = 760 mm Hg 756 mm Hg (Intrapleural pressure) 760 mm Hg (Intrapulmonary pressure) Diaphragm Intrapulmonary pressure becomes less than atmospheric pressure; air flows in Air flows in (~500 mL per quiet breath) Pleural cavity volume increases Intrapleural pressure decreases Alveolar volume increases Intrapulmonary pressure decreases 759 mm Hg 754 mm Hg atm = 760 mm Hg No breathing: - atmospheric pressure equals intrapulmonary pressure ie 760mm Hg - intrapleural pressure is below 760mm Hg with Inhalation: - Alveolar volume increases - Alveolar pressure decreases - intrapulmonary pressure drops to 759mm Hg - intrapleural pressure drops to 754mm Hg Diaphragm Diaphragm contracted

Figure 23.22a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Intrapulmonary pressure = atmospheric pressure Quiet expirationQuiet inspiration atm = 760 mm Hg atm = 760 mm Hg 754 mm Hg (Intrapleural pressure) 756 mm Hg (Intrapleural pressure) 760 mm Hg (Intrapulmonary pressure) Diaphragm 760 mm Hg Intrapulmonary pressure becomes greater than atmospheric pressure; air flows out Intrapulmonary pressure becomes less than atmospheric pressure; air flows in Air flows out (~500 mL per quiet breath) Pleural cavity volume decreases intrapleural pressure increases Alveolar volume decreases intrapulmonary pressure increases 761 mm Hg 756 mm Hg atm = 760 mm Hg Air flows in (~500 mL per quiet breath) Pleural cavity volume increases Intrapleural pressure decreases Alveolar volume increases Intrapulmonary pressure decreases 759 mm Hg 754 mm Hg atm = 760 mm Hg (a) Diaphragm contracted Diaphragm relaxed

31 I breath = ~ 500 ml termed Tidal volume: approx 12-16/ min Intrapulmonary pressure changes are minimal; inhalation = 759mm Hg exhalation = 761mm Hg

32 Factors for Pulmonary Ventilation Compliance –An indicator of expandability (distensibility) – how easily the lungs expand and contract – depends mostly on elastic fibers –Low compliance requires greater force (fibrosis, excess fluid) –High compliance requires less force (emphysema) Factors That Affect Compliance –Connective tissue structure of the lungs (fibrosis, emphysema) –Level of surfactant production (RDS) –Mobility of the thoracic cage (cracked rib, etc.) Elastic Rebound –When inhalation muscles relax Elastic components of lungs recoil Returning lungs and alveoli to original position

33 Pulmonary Ventilation

34 Pulmonary Ventilation The Intrapulmonary Pressure –Also called intra-alveolar pressure Intra = within = Pressure within the alveoli –Is relative to P atm (atmospheric pressure = 760mm Hg) –In relaxed breathing, the difference between P atm and intrapulmonary pressure is small about -1 mm Hg on inhalation = 759mm Hg or +1 mm Hg on exhalation = 761mm Hg – Maximum straining, a dangerous activity, can change the limits of the range from -30 mm Hg to +100 mm Hg

35 Modes of Breathing Quiet Breathing (eupnea) –Involves active inhalation and passive exhalation –Diaphragmatic breathing or deep breathing –Costal breathing or shallow breathing Forced Breathing (hyperpnea) –Involves active inhalation and exhalation –Assisted by accessory muscles –Maximum levels occur in exhaustion Apnea (consider sleep apnea) –No movement of muscles of respiration and volume of the lung remains unchanged Respiratory movements are classified by pattern of muscle activity into:

36 Measurements of Pulmonary performance

Pulmonary Performance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lung volume (mL) 0 Total lung capacity Vital capacity Functional residual capacity Residual volume Expiratory reserve volume Inspiratory capacity Inspiratory reserve volume Tidal volume Inspiration Expiration

Pulmonary Performance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lung volume (mL) 0 Total lung capacity Vital capacity Functional residual capacity Residual volume Expiratory reserve volume Inspiratory capacity Tidal volume Inspiratory reserve volume

39 Respiratory Rates and Volumes Respiratory system adapts to changing oxygen demands by varying: –The number of breaths per minute (respiratory rate = f ; 12-16) –The volume of air moved per breath (tidal volume; 500ml) = V T The Respiratory Minute Volume = V E – Amount of air moved per minute –Is calculated by: f x V T = V E respiratory rate (per minute)  tidal volume Anatomic Dead Space = V D –Only a part of respiratory minute volume reaches alveolar exchange surfaces –Volume of air remaining in conducting passages is anatomic dead space

40 Alveolar Ventilation = V A Amount of air reaching alveoli each minute –Remember dead space (air already in lung) Calculated as: respiratory rate  (tidal volume - anatomic dead space) V A = f x (V T - V D )

Pulmonary Performance 41

42 Definitions Tidal volume (resting) –amount of air one can move in or out of lungs in single respiratory cycle (resting conditions) Inspiratory reserve volume (IRV) –amount of air one can take in over and above tidal volume Expiratory reserve volume (ERV) –amount of air one can voluntarily expel after completed normal respiratory cycle. Residual volume –amount of air remaining in lungs after maximal exhalation (1200 males; 1100 females) –Minimal volume – amt air left if lungs collapsed Inspiratory capacity –tidal volume + inspiratory reserve volume Vital capacity –Maximum amt of air one can take into or out of lungs during forced exhalation and inhalation Total lung capacity –Total volume of lungs = vital capacity and residual capacity (avg = 6000ml males; 4200ml females

43 Mechanics of breathing How do you breathe? 1. Structures involved - muscles, bones and elastic fibers 2. Pulmonary ventilation - changing volumes and changing pressures 3. Pulmonary performance - how much work can you lungs really do? - what is the full lung capacity?

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