1 - Our body needs a constant supply of oxygen to support metabolism - The respiratory system brings oxygen through the airways of the lung into the alveoli, where it diffuses into the blood for transport to the tissues - This process is so vital that difficulty in breathing is experienced as a threat to life itself - Whether death is a real possibility or not, people with respiratory disorders are often very anxious and fearful that they may die, perhaps agonizingly - The respiratory system also has other essential functions: o Expels carbon dioxide (CO 2 ), a metabolic waste product that is transported from the tissues to the lungs for elimination o Filters and humidifies air that enter the lungs o Traps particulate matter in the mucus of the airways and propels it toward the mouth for elimination by coughing or swallowing

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Page 1: 1. ana and physio respi


- Our body needs a constant supply of oxygen to support metabolism- The respiratory system brings oxygen through the airways of the lung into

the alveoli, where it diffuses into the blood for transport to the tissues- This process is so vital that difficulty in breathing is experienced as a threat

to life itself- Whether death is a real possibility or not, people with respiratory disorders

are often very anxious and fearful that they may die, perhaps agonizingly

- The respiratory system also has other essential functions:o Expels carbon dioxide (CO2), a metabolic waste product that is

transported from the tissues to the lungs for eliminationo Filters and humidifies air that enter the lungso Traps particulate matter in the mucus of the airways and propels it

toward the mouth for elimination by coughing or swallowing

UPPER AIRWAYS- The airway are the regions through which air passes on its way to the

exchange areas of the lungs- The upper airways consist of the nasal cavities, pharynx, and larynx

A. NASAL CAVITY- The nose is formed from both bone and cartilage- Each opening of the nose on the face (nostrils or nares) leads to a cavity


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- The vestibule is lined anteriorly with skin and hair that filter foreign objects and prevent them from being inhaled

- The posterior vestibule is lined with a mucous membrane, composed of columnar epithelial cells, and goblet cells that secrete mucus

- The mucous membrane extends throughout the airways, and cilia (hair-like projections) propel mucus to the pharynx for elimination by swallowing or coughing

- The portion of mucous membrane that is located at the top of the nasal cavity, just beneath the cribriform plate of the of the ethmoid bone, is specialized (olfactory) epithelium, which provides the sense of smell

- Along the sides of the vestibule are TURBINATES, mucous membrane-covered projections that contain a very rich blood supply from the internal and external carotid arteries

o They warm and humidify inspired air

- PARANASAL SINUSES, open areas within the skull, are named for the bones in which they lie – frontal, ethmoid, sphenoid, and maxillary

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o Passageways from the paranasal sinuses drain into the nasal cavitieso Nasolacrimal ducts, which drain tears from the surface of the eyes,

also drain into the nasal cavity

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- The mouth is considered part of the upper airway but only because it can be used to deliver air to the lungs when the nose is obstructed or when high volumes of air are needed, such as during exercise

o The mouth does not perform the nasal functions efficiently, especially those of warming, humidifying, and filtering air

B. PHARYNX- The pharynx is a funnel-shaped tube that extends from the nose to the


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- It can be divided into three sections:o NASOPHARYNX

Is located above the margin of the soft palate and receives air from the nasal cavity

From the ear, the Eustachian tubes open into the nasopharynx The pharyngeal tonsils (called adenoids when enlarged) are

located on the posterior wall of the nasopharynx

o OROPHARYNX Serves both respiration and digestion It receives air from the nasopharynx and food from the oral

cavity Palatine (faucial) tonsils are located along the sides of the

posterior mouth, and the lingual tonsils are located at the base of the tongue

o LARYNGOPHARYNX (HYPOPHARYNX) Located below the base of the tongue, is the most inferior

portion of the pharynx It connects to the larynx and serves both respiration and


C. LARYNX- The larynx is commonly called the VOICE BOX

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- It connects the upper (pharynx) and lower (trachea) airways- The larynx lies just anterior to the upper esophagus- Nine cartilages form the larynx:

o Three large unpaired cartilages (epiglottis, thyroid, cricoids)o Three small paired cartilages ( arytenoid, corniculate, cuneiform)

The cartilages are attached to the hyoid bone above and below the trachea by muscles and ligaments, all of which prevent the larynx from collapse during inspiration and swallowing

- The larynx consists of the endolarynx and a surrounding triangle-shaped bone and cartilage

- The endolarynx is formed by two paired folds of tissue, forming the false and the true vocal cords

- The slit between the vocal cords forms the glottis

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- The epiglottis, a leaf-shaped structure immediately posterior to the base of the tongue, lies above the larynx

o When food or liquids are swallowed, the epiglottis closes over the larynx, protecting the lower airways from aspiration

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- They thyroid cartilage protrudes in front of the larynx, forming the “Adam’s apple”

- The cricoids cartilage lies just below the thyroid cartilage and is the anatomic site for an artificial opening into the trachea (tracheostomy or cricothyroidotomy)

- The internal portion of the larynx is composed of muscles that assist with swallowing, speaking, and respiration and that contribute to the pitch of the voice

- The blood supply to the larynx is through the branches of the thyroid arteries

- The nerve supply is through the recurrent laryngeal and superior laryngeal nerves

LOWER AIRWAYS- The lower airways or tracheobrochial tree is composed of the trachea, right

and left mainstem bronchi, segmental bronchi, subsegmental bronchi, and terminal bronchioles

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- Smooth muscle, would in overlapping clockwise and counterclockwise helical bands, is found in all of these structures

- This arrangement allows contraction of the smooth muscle to decrease the diameter of the airways, increasing the resistance to air flow

- This muscle is subject to spasm in many airway disorders- The lower airways continue to warm, humidify, and filter inspired air en

route to the lungs

A. TRACHEA- The trachea (windpipe) extends from the larynx to the level of the seventh

thoracic vertebrae, where it divides into two main (primary) bronchi- The point at which the trachea divides is called the CARINA- The trachea is a flexible, muscular, 12-cm long air passage with C-shaped

cartilaginous rings- Along with all other regions of the lower airways it is lined with

pseudostratified columnar epithelium that contains goblet (mucus-secreting) cells and cilia

- Because the cilia beat upward, they tend to carry foreign particles and excessive mucus away from the lungs to the pharynx . (no cilia are present in the alveoli)

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B. BRONCHI AND BRONCHIOLES- The right mainstem bronchus is shorter and wider, extending more

vertically downward, than the left mainstem bronchus- Thus, foreign bodies are more likely to lodge here than in the left mainstem

bronchus- The segmental and subsegmental bronchi are subdivisions of the main

bronchi and spread in an inverted, tree-like formation through each lung- Cartilage surrounds the airway in the bronchi, but the bronchioles (the final

pathway to the alveoli) contain no cartilage and thus can collapse and trap air during active exhalation

- The terminal bronchioles are the last airways of the conducting system- The area from the nose to the terminal bronchioles does not exchange gas

and functions as ANATOMIC DEAD SPACEo The lack of gas exchange means that the first air out of the mouth

during exhalation resembles room air, but the last air out (end-tidal air) resembles alveolar air

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LUNGS AND ALVEOLIA. LUNGS- The lungs lie within the thoracic cavity on either side of the heart- They are cone-shaped, with the apex above the first rib and the base

resting on the diaphragm- Each lung is divided into superior and inferior lobes by an oblique fissure

o The right lung is further divided by a horizontal fissure, which bounds a middle lobe

o The right lung, therefore, has three lobeso The left lobe has only two

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- In addition to these five lobes, which are visible externally, each lung can be subdivided into about 10 smaller units (bronchopulmonary segments)

o Each segment represents the portion of the lungs that is supplied by a specific tertiary bronchus

o These segments are important surgically, because a diseased segment can be resected without the need to remove the entire lobe or lung

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- The two lobes are separated by a space (the mediastinum), where the heart, aorta, vena cava, pulmonary vessels, esophagus, part of the trachea and bronchi, and the thymus gland are located

- The lungs contain gas, blood, thin alveolar walls, and support structures

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- The alveolar walls contain elastic and collagen fibers; these form a three-dimensional, basketlike structure that allows the lung to inflate in all directions

- Branches of the pulmonary artery provide most of the blood supply of the lungs

o The blood is oxygen-poor, but oxygen is supplied by inspired airo The trachea and bronchioles, which are not part of the oxygen

exchange surface, receive oxygen-rich blood from branches of the aorta

B. LUNG VOLUMES- The lungs of an average 19-year old man have a total capacity of about

5900ml- However, a person cannot exhale all the air from the lungs, and about

1200ml of air always remains, no matter how forceful the expirationo This remaining volume (RESIDUAL VOLUME) prevents the collapse of

the lung structures during expiration

- The volume of air that moves in and out with each breath is called the TIDAL VOLUME

o During quiet breathing, tidal volume is about 500mlo When we take a deep breath, the lung is more fully expandedo The amount of extra air inhaled, beyond the tidal volume, is called

the INSPIRATORY RESERVE VOLUME; the extra air that can be exhaled after normal breath is called the EXPIRATORY RESERVE VOLUME

- Lung volumes are often combined into capacities:o TIDAL LUNG CAPACITY (all four volumes)o VITAL CAPACITY ( all volumes except residual volume), which is the

amount we can ventilateo FUNCTIONAL RESERVE CAPACITY (expiratory reserve plus residual


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o INSPIRATORY CAPACITY ( tidal volume plus inspiratory reserve volume)

These volumes and capacities are frequently altered by disease


- The lung parenchyma, which consists of millions of alveolar units, is the working area of the lung tissue

- At birth, we have about 24 million alveoli; by age 8 years, we have 300 million

- The total working alveolar surface area is approximately 750-860 square feet

- The blood supply flowing toward the alveoli comes from the right ventricle of the heart

- The entire alveolar unit (respiratory zone) is made up of respiratory bronchioles, alveolar ducts, and alveolar sacs

- The alveolar walls are extremely thin, with an almost solid network of interconnecting capillaries

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o Because of the extensiveness of the capillary system, the flow of he blood in the alveolar wall has been described as a “sheet” of flowing blood

- Oxygen and CO2 are exchanged through a respiratory membrane, about 0.2mm thick

- The average diameter of the pulmonary capillary is only about 5μm, but red blood cells (7μm in diameter) must squeeze through, actually touching the capillary wall

- The alveolus comprises two cell types:o Type I PNEUMOCYTES

Which line the alveolus, are thin and incapable of reproduction but are effective in gas exchange

o Type II PNEUMOCYTES Are cuboidal and do not exchange oxygen and CO2 well They produce surfactant and are important in lung injury and


D. THORAX- The bony thorax provides protection for the lungs, heart, and great vessels- The outer shell of the thorax is made up of 12 pairs of ribs- The ribs connect posteriorly to the transverse processes of the thoracic

vertebrae of the spine- Anteriorly, the first seven pairs of ribs are attached to the sternum of

cartilage- The 8th, 9th, and 10th ribs (false ribs) are attached to each other by costal

cartilage- The 11th and 12th ribs (floating ribs) allow full chest expansion because they

are not attached in any way to the sternum

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- Breathing is accomplished by skeletal muscle alteration of the thoracic space

- The diaphragm is the primary muscle of breathing, and serves as the lower boundary of the thorax

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- The diaphragm is a dome-shaped in the relaxed position, with central muscular attachments to the xiphoid process of the sternum and the lower ribs

- Contraction of the diaphragm pulls the muscle downward, increasing the thoracic space and inflating the lungs

- The diaphragm’s nerve supply (phrenic nerve) comes through the spinal cord at the level of the third cervical vertebra

o Thus, spinal injuries at C3 or above can impair ventilationhttp://www.youtube.com/watch?v=hp-gCvW8PRY


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- The pleurae are serous membranes that enclose the lung in a double-walled sac

- The VISCERAL pleura covers the lung and the fissures between the lobes of the lung

- The PARIETAL pleura covers the inside of each hemithorax, the mediastinum, and the top of the diaphragm; it joins the visceral pleura at the HILUS (a notch in the medial surface of the lung), where the mainstem bronchi, pulmonary blood vessels, and nerves enter the lung

- Normally, no space exists between the pleurae; the PLEURAL SPACE is a potential space between the two layers of pleura

- A thin film (only a few milliliters) of serous fluid acts a lubricant in the potential space

- The fluid causes the moist pleural membranes to adhere, creating a pulling force that helps to hold the lungs in an expanded position

o The action of the pleurae is analogous to coupling two sheets of glass with a thin film of water. It is extremely difficult to separate the sheets of glass at right angles, yet they readily slide along each other

- If air or increases amounts of serous fluid, blood, or pus accumulates in the thoracic space, the lungs are compressed and respiratory difficulties follow

- These conditions constitute PNEUMOTHORAX (air in the pleural space) or HEMOTHORAX (blood in the pleural space)

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- The respiratory system enhances gas exchangeo Inspiration brings oxygen-rich air into the alveolio The upper and lower airways filter and humidify inspired airo Gas exchange between the air and the blood occurs in the alveoluso Oxygen diffuses into the blood, and CO2 diffuses from the blood into

the alveolar airo The CO2 enriched air is removed from the body during expiration


- The thorax and diaphragm alter pressures in the thorax to drive air movement

o The movement of air depends on pressure gradients between the atmosphere and the air in the lungs, with air flowing from regions of higher pressure to regions of lower pressure

o On inspiration, the dome of the diaphragm flattens and the rib cage lifts. As thoracic and lung volumes increase, alveolar pressure decreases and air moves into the lungs

- Airway resistance also affects air movement and is affected primarily by the diameter of the airways

o A decreased diameter of the airways due to bronchial muscle contraction or to secretions in the airways increases resistance and decreases the rate of air flow

- During quiet breathing, expiration is usually passive, that is, does not require the use of muscles

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A. VENTILATION- Ventilation, the movement of air in and out of the lungs, involves three

forces:o Compliance properties of the lung and the thorax (chest wall)o Surface tensiono Muscular efforts of inspiratory muscles

COMPLIANCE- Refers to the ease with which the lung expands and indicates the

relationship between the volume and the pressure of the lungs- The lungs are elastic structures that tend to recoil to a volume slightly less

than RESIDUAL VOLUME (the volume of gas remaining to distend the lungs after a full exhalation)

- The force required to distend the lungs is the difference between the alveolar pressure and the intrapleural pressure

- Diseases that cause fibrosis of the lungs result in “stiff” lungs with low compliance

o Stiff lungs require high inspiratory pressures to achieve a set volume of gas

o In contrast, diseases such as emphysema that damage the elastic structure of the alveolar walls result in “floppy” lungs with greater compliance

SURFACE TENSION- Surface tension, the result of the air-liquid interface at each alveolus,

restricts alveolar expansion on inspiration and aids alveolar collapse on expiration

- Surfactant produced by type II cells in the alveolar lining lower surface tension and thus increases compliance and aids ventilation

- A deficiency of surfactant results in stiff lungsis a property of the surface of a liquid that allows it to resist an external force

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MUSCULAR EFFORT- Ventilation also requires muscular effort- For inspiration to occur, the pressure within the lungs (alveolar pressure)

must be less than atmospheric pressure- Contraction of the diaphragm and the external intercostals muscles

enlarges the size of the thorax- The external intercostals muscles pull the ribs upward and forward, thus

increasing the transverse and anteroposterior diameter

- Two accessory muscles of inspirationo Scaleneo Sternocleidomastoid

Elevate the first and second ribs during inspiration to enlarge the upper thorax and stabilize the chest wall

The sternocleidomastoid muscle elevates the sternum The expanding thorax creates a more negative intrapleural

pressure, which expands the lungs When the alveolar pressure becomes lower than the

atmospheric pressure, air flow into the lungs

- During exhalation, the inspiratory muscles relaxo The elastic recoil of the lung tissue, increases alveolar pressure above

atmospheric pressure and causes air to move out of the lungso Air flow stops when the recoil pressure of the lungs balances the

muscular and elastic forces of the chest

- Although expiration is usually passive, forced expiration and coughing employ accessory muscles to decrease the size of the thoracic space and cause expiration

o Contraction of the abdominal muscles forces the diaphragm upward to its dome-shaped position

o Contraction of the internal intercostals muscles pull the ribs inward, thus decreasing the anteroposterior diameter of the chest wall

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WORK OF BREATHING- Respiratory muscle contraction represents a significant metabolic load- Total volume and respiratory rate are adjusted to minimize the workload

on the bodyo For example, clients with obstructive lung disease use slower deeper

breaths to maintain appropriate alveolar ventilationo Clients with restrictive lung disease use frequent, shallow breaths to

maintain alveolar ventilation

B. RESPIRATORY CONTROL- The lungs have no intrinsic control of themselves; instead, they are

controlled by the central nervous system (CNS)

CENTRAL NERVOUS SYSTEM- The MEDULLA has several levels of respiratory centers

o The dorsal respiratory group primarily provides for inspirationo The ventral respiratory group is normally quiet unless increased

ventilation is needed or if active exhalation is performedo The pons has an apneustic center, which contains both expiratory

and inspiratory neuronso The upper pons contains the pneumotaxic center, which fine-tunes

breathing (for example, the pneumotaxic center allows for talking and breathing)

- Output from the respiratory neurons, located in the medulla descends via the ventral and lateral columns of the spinal cord to phrenic motor neurons of the diaphragm and intercostals motor neurons of the intercostals muscles

o The result is rhythmic respiratory movements

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- The cortex also allows voluntary control of breathing (holding our breath or altering the rate or depth of breathing)

REFLEX CONTROL- The cough reflex is neural reflex stimulated by mechanical stimuli

- Inhaled irritants and mucus (mechanical stimulus) excite rapidly adapting pulmonary stretch receptors concentrated in the region of the carina and the large bronchi

In anatomy, the carina is a cartilaginous ridge within the trachea that runs anteroposteriorly between the two primary bronchi at the site of the tracheal bifurcation at the lower end of the trachea (usually at the level of the 4th to 5th thoracic vertebrae, which is in line with theAngle of Louis).The mucous membrane of the carina is the most sensitive area of the trachea and larynx for triggering a cough reflex. Widening and distortion of the carina is a serious sign because it usually indicates carcinoma of the lymph nodes around the region where the trachea divides.

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- The stimulation of the receptors results in high-velocity expiratory gas flow (cough)

PERIPHERAL CONTROL- Peripheral control of respiration is due to the sensing of partial pressure of

oxygen (PO2) and of partial pressure of CO2 (PCO2) in the blood- In the blood, CO2 is an acid

o An increase in PCO2 causes acidosis, or a fall in pHo Receptors that are responsive to changes in oxygen, CO2, and pH are

located in the brain in structures adjacent to blood vessels

- Arterial blood oxygen and CO2 pressures are sensed by receptors in the carotid body and the aortic body

- The carotid body receptors are located close to the carotid sinus, and the aortic bodies are located near the aortic arch

- Chemoreceptors are also located on the brain side of the blood-brain barrier2

o These receptors respond only to PCO2 (or pH)

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o An elevated PCO2 in arterial blood is the normal stimulus to increase ventilation

o Low levels of partial pressure of oxygen in arterial blood (PaCO2) can stimulate ventilation, but only when PO2 drops below 70mmHg

C. GAS EXCHANGE AND TRANSPORT- Exchange of gases occurs between air and blood in the respiratory

membrane- Respiration is the exchange of oxygen and CO2 at the alveolar-capillary level

(external respiration) and at the tissue-cellular level (internal respiration)- During respiration, body tissues are supplied with oxygen for metabolism

and CO2 is released- Each gas exerts a pressure (partial pressure) as if it were the only gas

present- When a liquid is exposed to a gas, gas enters the liquid in proportion to the

individual pressures

- PO2 in the alveoli is about 104mmHg, and PCO2 is about 40mmHgo Venous blood has a PO2 of 40mmHg and a PCO2 of about 45mmHg

- These differences in concentration result in the movement of oxygen into the pulmonary capillary bloodstream and of CO2 out of the pulmonary capillary bed into the alveoli


- After diffusing into the pulmonary capillaries, oxygen is transported throughout the body by the circulatory system

- The oxygen is dissolved in the plasma (3%) or bound in the ferrous iron-containing protein hemoglobin (97%)

- The combination of hemoglobin and oxygen forms oxyhemoglobin, which greatly increases the oxygen content of the blood above that dissolved in plasma

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- Carbon monoxide (CO) and other chemicals impair the ability of hemoglobin to transport oxygen in the blood

E. CARBON DIOXIDE TRANSPORT- CO2, the waste product of tissue metabolism, is carried by the blood in the

following ways:o Combined with water as carbonic acid (70%)o Coupled with hemoglobin (23%)o Dissolved in plasma (7%)

- Red blood cells contain the enzyme carbonic anhydrase, which rapidly breaks down CO2 into hydrogen ions and bicarbonate ions

- When venous blood enters the lungs for gas exchange, this reaction reverses, forming CO2, which is then exhaled


- The relationship between VENTILATION (air flow) and PERFUSION (blood flow) determines the efficiency of gas exchange

- Low ventilation/perfusion (V/Q) ratios and high V/Q ratios both result in low oxygen delivery to the body

- The ventilation-perfusion balance differs from the top to the base of the lung

- Blood flow (to a lesser extent) ventilation are greater in the more dependent lung segments at the base of the lung

- Consequently, the base of the lung has the lowest V/Q ratio, and the apex of the lung has the highest V/Q ratio

- The V/Q balance is controlled at both the airway and vascular levels

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o Hypoxia resulting from underventilation of the alveolar region, causes vasoconstriction, which redirects blood to well-ventilated alveoli

o CO2 in the airways dilates the airway smooth muscleo Poorly perfused alveoli have low CO2 levels, and the resultant airway

constriction directs ventilation to better-perfused alveoli

G. REGULATION OF ACID-BASE BALANCE- The lungs, through gas exchange, have a key role in regulating the acid-base

balance of the body- Pulmonary disorders that change the CO2 level in the blood cause either

respiratory acidemia or respiratory alkalemia- Insufficiency ventilation causes HYPERCAPNIA, a respiratory academia

caused by retention of excessive amounts of CO2

- Hyperventilation, conversely, causes HYPOCAPNIA, a respiratory alkalemia due to the low amounts of CO2 in the blood

- The effectiveness of ventilation is best measured by the PCO2 in the arterial blood (PaCO2)

o Because the respiratory system is normally set to maintain a PaCO2 between 35 and 45mmHg at sea level, a PaCO2 above this range represents HYPOVENTILATION

o Anesthetic agents, sedatives, and narcotics all tend to increase the resting PaCO2

H. REACTION TO INJURY- Any injury to the lung affects the barrier between the atmosphere and the

bloodstreamo This barrier, which lies within the alveolar septum, is made up of

epithelial (types I and II pneumocytes) and vascular endothelial cellso Injury resulting from airborne or blood-borne agents may increase

vascular permeability and cause pulmonary edemao Inflammatory cells (neutrophils) arrive soon after acute injury

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o Then the proportion of lymphocytes, monocytes, and macrophages increases

- The basic lung repair processes include lymphatic drainage of excess fluid and phagocytic removal of protein and debris

o This action generally restores lung function and structureo More severe injury requires endothelial and epithelial cell

regeneration and proliferation of interstitial cells (fibroblasts)o Type II cells that are generated for defense eventually differentiate

into thin type I cells, which permit gas exchange


o Because the nose has a larger surface-volume ratio and a much more tortuous pathway for airflow than the mouth, particle deposition and conditioning of the air are more efficient when we breathe through the nose

Larger particles (˃10mm) are generally trapped; smaller particles (<1mm) may readily enter the lower airways

- There are four clearance mechanisms of the lower airways and alveoli:o Cough (first five to eight bronchial generations)o Mucociliary system (to terminal bronchioles)o Macrophages ( alveoli and respiratory bronchioles)o Lymphatics ( alveoli and interstitium)

- The cough, an automatic procedure reflex used to clear the trachea, occurs most rapidly in the clearing process

- If the swallowing reflex is delayed or absent, a cough may be stimulated to avoid aspiration of particle into the lower airways

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J. DEFENSE BY THE RESPIRATORY EPITHELIUM- Unlike the upper and lower airways, the alveoli lack a mucous layer to trap

foreign particles and cilia to propel them to the pharynx for elimination- The alveolar lining is made up of flat, membranous pneumocytes (type I

cells) and rounded granular (type II) cells- The type II cells are resistant to injury ad cover most of the alveolar surface

after resistant to injury and cover most of the alveolar surface after exposure to infectious agents

- Alveolar macrophages, derived from blood monocytes are active phagocytes that remove dead cells and protein and that synthesize and secrete substances that regulate the immune system

o They leave the lung by the mucociliary system or the lymphatic system

K. DEFENSE BY IMMUNOLOGIC MECHANISMS- The systemic immune system responds to the lung during inflammatory

processes by mobilizing blood neutrophils and monocytes- Recruited thymus-dependent (T) and thymus-independent (B) lymphocytes

contribute to local cell-mediated immune reactions and the production of specific antibodies within the alveoli

- Cell-mediated immunity is a key determinant in resistance to organisms such as Mycobacterium tuberculosis and Pneumocystis carinii

- Immune mechanisms are generally a host defense function- However, hypersensitivity immune reactions lead to tissue injury and are

responsible for clinical conditions such as asthma, granuloma formation, and lung transplant rejection

EFFECTS OF AGING- Most of the changes that occur with aging affect the lower airway- Movement of the cilia in the upper airway slows and becomes less effective- This change predisposes older clients to a greater number of respiratory


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- Lung structure also changes with age- The lung become rounder as a result of increased anteroposterior

diameter, circumference, area, and height of the lung- The proportion of the lung formed by alveolar duct air increases, and

alveolar air decreases- Loss of alveolar wall tissue and its elastic tissue fibers is seen- The result is a deterioration of lung function- The air spaces enlarge, although this is not referred to as emphysema

because it is not a result of disease- These changes may be due to environmental pollutants rather than to

aging alone- Environmental or occupational pollutants, in addition to normal aging

process, may be a component in the decline of lung function