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RSPT 1207 Cardiopulmonary Anatomy and Physiology
I.
LUNG VOLUMES – There are 4 lung volumes:
 Tidal volume (Vt) – the amount of gas that is inhaled and exhaled on a normal, daily basis. 10% of the total lung capacity
 Inspiratory Reserve volume (IRV) – the maximum volume of air inhaled after a normal inspiration. 50% of TLC
 Expiratory Reserve volume (ERV) – the volume of air that can be exhaled from the end of a normal exhalation. 20% of TLC
 Residual volume (RV) – the volume remaining after a maximal exhalation.
20% of TLC
II.
LUNG CAPACITY – By adding 2 or more of the lung volumes, 4 lung capacities are formed
 Total Lung Capacity (TLC) is the volume of gas in the lung at the end of maximal inhalation. It is the sum of all four volumes:
TLC =
100% =
Vt + IRV + ERV + RV
10% + 50% + 20% + 20%
 Inspiratory Capacity (IC) is the volume of gas found in the lung that can be inhaled from a normal resting end exhalation. It is the sum of Vt and IRV:
IC =
60% =
Vt + IRV
10% + 50%
 Vital Capacity (VC) is the largest volume of gas that can be moved in or out of the lung, represents all the air that can be inhaled and exhaled forcibly leaving only the RV in the lung. It is the sum of the Vt, IRV and ERV:
VC =
80% =
Vt + IRV + ERV
10% 50% 20%
 Functional Residual Capacity (FRC) is the volume of gas that is left in the lung at the end of a normal exhalation. It is the sum of RV and ERV:
FRC =
40%
RV + ERV
20%+ 20%
III.
THE LAYERS OF THE AIRWAYS – Larger airways have thicker walls more layers over a large lumen. As we move more distal and peripherally the airways become smaller and have less layers. The alveoli will only have the innermost layer.

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IV.
SMOOTH MUSCLE
 Differs from skeletal muscle in that it is involuntary, smooth in appearance (not striated) lines visceral and is slow to contract
 The conscience mind has no control over contraction of smooth muscle
 Contraction and relaxation of smooth muscle is slow and responds to stimulation from the autonomic nervous system
 Contraction of smooth muscle generally results in changing the shape of the organ.
 Lines the hollow organs of: o Respiratory Tract o Blood vessels o Iris of the eye o Contraction in the respiratory tract, digestive tract, and blood vessels result in the narrowing of the organs lumen, contraction in the eye results in constriction of the iris
 In the lung tissue smooth muscle is present in the lamina propria
 In the trachea, mainstream bronchi, and lobar bronchi the “C” shaped cartilage minimizes effects of constriction of smooth muscle
 At the level of segmental bronchi, helical shaped cartilage plate oppose the helical-shaped spirals of smooth muscle
 At the level of the bronchioles, no cartilage is present but lamina propria persists with smooth muscle present in clockwise and counterclockwise bands. This is where smooth muscle constriction can constrict a tube distal to an obstruction.
 In the alveoli short muscle strands persists in the alveolar wall or septum.

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V.
LAYERS OF THE TRACHEA and MAINSTEM BRONCHI
 Epithelial layer – Also called the epithelium, has pseudo-stratified columnar ciliated epithelium
 Lamina Propria – Contains loose connective tissue, Structures found include submucosal glands, nerve ending for sympathetic and parasympathetic system, mast cells. Bronchial smooth muscle is located in this layer.
 Cartilage layer – the trachea and mainstem bronchi have the “C” shaped cartilage rings
 Peribronchial Sheath – also called the adventitia. Contains blood vessels, nerves and lymphatic vessels. Fatty tissue also located in this layer to support external walls of large airways.
VI.
LAYERS OF THE LOBAR and SEGMENTAL BRONCHI
 At this level the layer of cartilage turns into cartilage plates
 In the lamina propria layer the smooth muscle becomes helical shaped
 Bronchial smooth muscle constriction is not clinically significant because of the strong outward support of the cartilage plates
VII.
LAYERS OF THE SUBSEGMENTAL BRONCHI
 As these airways become less than 1 mm in diameter, the adventitia and cartilage layer disappear
 The outermost layer of the subsegmental bronchi is the lamina propria
 The epithelial layer and the mucous layer remains
 The smooth muscle continues in helical shapes surrounding the airway
 Smooth muscle constriction at this point can now be felt
VIII.
LAYERS AT THE BRONCHIOLE LEVEL
 The lamina propria continues
 Smooth muscle wraps around the lumen in clockwise and counterclockwise bands
 At this point the lumen can be completely shut by constriction of the smooth muscle, thus the term bronchial asthma

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IX.
THE TERMINAL BRONCHIOLES
 As the bronchioles branch into smaller and smaller generations, the lamina propria begins to thin
 Ciliated cells become simple cuboidal cells
 Mucous glands are gone when the lamina propria disappears
 Goblet cells remain
 Two structures are found only at the level of the terminal bronchioles o Canals of Lambert – Passageways for air between terminal bronchi and alveoli. Provides collateral flow for ventilation distal to an obstruction.
They are not affected by smooth must contraction o Clara cells – Single secretory cells that bulge into the lumen of the terminal bronchioles. What is secreted is unknown; some speculate that they might secrete enzymes to detoxify from inhaled substances.
X.
THE RESPIRATORY ZONE
 Terminal Respiratory Unit –(TRU) term used to collectively call the airways distal to the terminal bronchioles; also call the primary lobule or acinus o Consists of 2-4 generations of respiratory bronchioles o Respiratory bronchioles branch into 3-5 alveolar ducts o Each alveolar duct contains 10-16 alveoli o Each alveolar duct terminates to a blind end which is an alveolar sac that is a cluster of 16-20 alveoli
 Shares bulk transfer of gas as well as diffusion of gas molecules
 Begins as terminal bronchioles feed into the respiratory bronchioles
XI.
RESPIRATORY BRONCHIOLES
 Distal to each terminal bronchiole is a respiratory bronchiole
 Contains simple cuboidal cells, no goblet cells present
 All have alveolar buds where gas diffusion can occur
 Total number of alveoli found as alveolar buds is minimal
XII.
ALVEOLAR DUCTS
 A collection of alveoli that contain an opening on the proximal and distal end
 It is as long as it is wide
 Contain about 50% of all lung’s alveoli, but only responsible for about 35% of gas exchange
XIII.
ALVEOLAR SAC
 An alveolar duct will terminate in a cluster of 16-20 alveoli
 Called a “sac” because it has a blind end
 Contains the other 50% of the lung’s total alveoli
 Accounts for about 65% of gas diffusion
 There is much more surface area in the alveolar sac
 Each of the 16-20 alveoli found in the sac contain common walls for gas diffusion

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XIV.
ALVEOLI
 There are 300 million alveoli in the adult lung
 Because of the common walls between each alveoli, there is a large collective surface area available for gas exchange
 The individual alveolus is tetrahedron in shape, which is a very stable geometric shape.
 The alveolus because of its shape has the tendency to stay open
 Walls of the alveoli are called septa
 Capillaries cover the external surface of the septum so that there is little space between the air in alveoli and blood in the capillary
XV.
PORES OF KAHN
 These are occasional openings in the septum between adjacent alveoli.
 Provide an interalveolar collateral flow, similar function to the Canals of
Lambert
 Number and size of pores vary from person to person
XVI.
PNEUMOCYTES
 The alveolus is made of two types of pneumocytes: o Type I Pneumocytes
 Formed by simple squamous epithelium cells and are flat and thin
 Make up 80-95% of surface area of an alveolus
 These are the walls where gas diffuse
 Capable of expanding a contracting without damage o Type II Pneumocytes
 Formed of glandular epithelium that from the corners
 Make up 5% of surface area of an alveolus
 Secrete pulmonary surfactant and may also secrete enzymes to help clean alveoli
 May be involved in the replacement of Type I Pneumocytes because they tend to multiply in cases of injury
XVII.
ALVEOLAR MACROPHAGES
 Macrophage – Mobile immune cell, third type of alveolar cell
 Found throughout the mucous membranes and just under the skin
 In the respiratory tract, macrophages roam through the alveoli through pores and canals
 Engulfs and eats foreign particles like bacteria or inorganic dust
 Specialized WBC derived from the monocyte that enters the respiratory tract via blood stream.

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XVIII.
INTERSTITIUM or INTERSTITIAL SPACE
 The interstitium of any part of the body is the loose connective tissue that is found between cells
 The alveolar sac and alveolar ducts are suspended in a gel like matrix of loose connective tissue with collagen fibers
 The gel keeps the alveoli from over distending by exerting some pressure on the alveoli
 There is clinical significance when the interstitial space swells
 The interstitium can be “loose” or “tight” depending on how close the cells are to one another
 The interstitial space can increase 3 times before the alveolar inflation is effected.
XIX.
PULMONARY CAPILLARY BED – A network of pulmonary capillaries cover the external surface of the alveolar bud in the respiratory bronchiole of each alveolus in the ducts and sac
XX.
SURFACE TENSION
 The force that exists at the interface between a liquid and a gas
 When like molecules are surrounded by the same molecules they are attracted to each other, and will move at random in all directions
 When air and liquid molecules come in contact with each other freedom of movement is affected.
 Interface is the point where air and water molecules come together
 Cohesive Force - The interface is an area of great opposing forces because the air molecules are moving toward air molecules and the liquid does the same
 SUFACE TENSION – is the result of that inter of a liquid and gas secondary to the cohesive forces.
 Can be measured in units of work (force) required to tear a 1 cm hole in the surface (Dynes/cm).
 The cells of the alveoli is made up of mostly water (90-93%), the surface tension of the alveoli is that of water.

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From: Des Jardins, Terrry. Cardiopulmonary Anatomy & Physiology: Essential of Respiratory Care , 2008.
 With pulmonary surfactant, a person would create a negative intrathoracic pressure of -2 to -5 cmH2O pressure.
 In the absence of surfactant, the same person would require -80 cmH2O to fill the alveoli. The WOB would be too high, a person could not survive.
XXI.
LaPLACE’S LAW OF SURFACE TENSION
 Discovered a mathematical relationship between the size of a bubble and the surface tension of that droplet
 The pressure needed to inflate the droplet is directly related to 4 times the surface tension of the liquid which formed the bubble
 Distending pressure needed to enlarge the droplet was inversely related to the size of the bubble
 Formula:
ST = Surface tension r = radius of droplet
P = pressure required to distend
P
ST r
 When the law is applied to the inflation of the alveoli, the pressure required to inflate an alveoli is directly proportional to 4x the surface tension and inversely proportional to the radius of the alveoli.
 As the alveoli’s radius decreases on expiration, the pressure required to inflate the deflated alveoli must be increased. Based on LaPlace’s law, at some point the alveoli could not be reinflated.
 If the surface tension were altered, the pressure would be altered.
 Pulmonary Surfactant decreases surface tension.
XXII.
PULMONARY SURFACTANT and INFLATION OF ALVEOLI
 A Phospholipid liquid that is secreted by the Type II pneumocytes.
 Lines the internal surface of the alveoli

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 The surfactant molecule has a water soluble end and an oil soluble end, it moves along the surface of the water-covered cell, oil soluble end is in the air and water soluble end is close to the cell
 Presence of surfactant at the alveolar gas liquid interface causes surface tension to decrease in proportion to the ratio of surfactant to alveolar surface area
 Deflated alveoli have a lower surface area because the walls are not stretched out, as alveoli inflates the surface are increases
 The ratio of surfactant to surface area of inflated alveoli is less than that of the ratio of the surfactant to surface area of deflated alveoli; this is because the surface area changed while the number of surfactant molecules in the lung stayed the same
From: Des Jardins, Terrry. Cardiopulmonary Anatomy & Physiology: Essential of Respiratory Care , 2008.
 If the surface tension decreases in proportion to the ratio of the surfactant to surface area, then the surface tension of the deflated alveoli is less than the surface tension of inflated alveoli
 Smaller alveoli have less surface tension , reducing the pressure required to inflate it
 Now the smaller alveoli is somewhat comparable to the larger alveoli, essentially the force that is needed to inflate both sizes of alveoli remains the same from the standpoint of surface tension all alveoli are equal
XXIII.
THE ALVEOLI and COMPLIANCE
 The pressure required to inflate the alveoli can be used to calculate the compliance of the lung.
 A more stiff lung will require more pressure to get the volume into it
 The normal lung has a compliance of about 80-100 cc/cmH2O pressure.
 A person that creates a driving pressure of 5 cmH2O pressure in a normal lung will produce 400 cc (5 x80) to 500 cc (5x100) of Vt.

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 The formula for lung compliance:
Volume change / Pressure change
V
P
Calculate the following:
V = 500, P = 10 C =
V = 500, P = 20 C =
V = 500, P = 50 C =
 As compliance rises, it takes less pressure to get 500 cc of volume into the lung
 As pressure to inflate rises, compliance drops