Chapter 22: Respiratory system Flashcards
Respiration:
◼️supplying body with O2 for cellular respiration; dispose of CO2, a waste product of cellular respiration
◼️it’s four processes involve both respiratory and circulatory systems
◼️also functions in olfaction and speech
Respiratory major function:
Respiration
How many processes does the respiratory system have?
Four
What are the four processes of respiration?
◼️pulmonary ventilation(breathing)
◼️external respiration
◼️transport
◼️internal respiration
Which two of the four processes is in the respiratory system?
◼️pulmonary ventilation (breathing )
◼️external respiration
Which two of the four respiratory processes are in the circulatory system?
◼️transport
◼️internal respiration
What is pulmonary ventilation?
Movement of air into and out of lungs
What is External respiration?
O2 and CO2 exchange between lungs and blood
What is the transport process?
O2 and CO2 in blood
What is the internal respiration process?
O2 and CO2 exchange between systemic blood vessels and tissues
Major organs of respiration system?
◼️nose, nasal cavity , para nasal sinuses ◼️pharynx ◼️larynx ◼️trachea ◼️bronchi and their branches ◼️lungs and alveoli
Respiratory zone:
◼️site of gas exchange
◼️microscopic structures : respiratory bronchioles , alveolar ducts, and alveoli
Conducting zone:
◼️conduits to gas exchange sites
◼️includes all other respiratory structures: cleanses, warms, humidifies air
The ____ and other respiratory muscles promote ventilation ?
Diaphragm
The nose functions :
◼️provides an airway for respiration. ◼️moistens and warm entering air ◼️filters cleans inspired air ◼️serves as resonating chamber for speech ◼️houses olfactory receptors
What are the two regions of the nose?
◼️external nose
◼️nasal cavity
What is the external nose?
◼️root, bridge, dorsum nasi, and apex
▪️philtrum - shallow vertical groove inferior to apex
▪️nostrils(nares) - bounded laterally by alae
Nasal cavity:
◼️within and posterior to external nose
▪️divided by midline nasal septum
▪️posterior nasal apertures (choanae) open into nasoparynx
▪️roof-ethmoid and sphenoid bones
▪️floor-hard (bone) ad soft palates (muscle)
Nasal vestibule:
Nasal cavity superior to nostrils
▪️vibrissae(hairs) filter coarse particles from inspires air
The rest of the nasal cavity is lined with two mucous membranes:
◼️olfactory mucosa
◼️respiratory mucosa
What does the olfactory mucosa contain?
Olfactory epithelium
What does the respiratory mucosa contain?
◼️pseudostratified ciliated columnar epithelium
◼️mucous and serous secretions contain lysozyme and defensins
◼️cilia move contaminated mucus posteriorly to the throat
◼️inspired air warmed by plexuses of capillaries and veins
◼️sensory nerve endings trigger sneezing
Nasal conchae:
Superior, middle, and inferior
◼️protrude edible from lateral walls
◼️increase mucosal area
◼️enhance air turbulence
Nasal meatus:
Groove inferior to each concha
During inhalation, conchae and nasal mucosa do what?
◼️filter
◼️heat
◼️moisten air
During exhalation , conchae and nasal mucosa do what?
Reclaim heat and moisture
Where are the paranasal sinuses located?
◼️frontal
◼️sphenoid
◼️ethmoid
◼️maxillary
What do the paranasal sinuses do?
◼️lighten skull
◼️secrete mucus
◼️help warm & moisten air
Rhinitis:
◼️inflammation of nasal mucosa
◼️nasal mucosa continuous with mucosa of respiratory tract ➡️ spreads from nose➡️ throat ➡️ chest
◼️spreads to tear ducts and paranasal sinuses causing
▪️blocked sinus passageways ➡️air absorbed ➡️vacuum ➡️sinus headache
Pharynx:
◼️muscular tube from base of skull to C6
▪️connects nasal cavity and mouth to larynx and esophagus
▪️composed of skeletal muscles
Three regions of pharynx ?
◼️nasopharynx
◼️oropharynx
◼️laryngopharynx
What is the nasopharynx?
Air passageway posterior to nasal cavity
Nasoparynx lining?
Pseudostratified columnar epithelium
What closes the nasoparynx during swallowing ?
Soft palate and uvula
Which tonsils are on posterior wall of nasopharynx?
Pharyngeal tonsil
Where is the pharyngotympanic located?
In the nasopharynx open into lateral walls
What is the pharyngotympanic ?
Tubes drain and equalize pressure in middle ear
What is the oropharynx?
Passageway of food and air from level of soft palate to epiglottis
What three structures are in the oropharynx?
◼️isthmus of Fauces
◼️palatine tonsils
◼️lingual tonsils
What type of lining does the oropharynx have?
Stratified squamous epithelium
Isthmus of Fauces:
Opening to oral cavity
Palatine tonsils :
In lateral walls of Fauces
Lingual tonsils:
On posterior surface of tongue
Laryngopharynx:
Passageway for food and air
Where is the laryngopharynx located?
Posterior to upright epiglottis
The laryngopharynx extends to what?
To larynx where continuous with esophagus
What type of tissue lines the laryngopharynx ?
Stratified squamous epithelium
Larynx:
Attaches to hyoid bone, opens into laryngopharynx , continuous with trachea
Functions of larynx?
◼️provides patent airway
◼️routes air and food into proper chambers
◼️voice production
▪️houses vocal folds
What are the nine cartilages f the larynx ?
All are hyaline cartilage except epiglottis:
▪️thyroid cartilage with laryngeal prominence(Adam’s apple)
▪️ring-shaped cricoid cartilage
▪️paired arytenoid, cuneiform, and corniculate cartilage
▪️epiglottis-ELASTIC CARTILAGE ; covers laryngeal inlet during swallowing ; covered in taste bud containing mucosa
▪️
▪️
▪️
▪️
Vocal ligaments in larynx are located where?
Deep to laryngeal mucosa
What do vocal ligaments do?
◼️attach arytenoid cartilages to thyroid cartilages
◼️contain elastic fibers
◼️form core of vocal folds (true vocal cords)
▪️glottis- opening between vocal folds
▪️folds vibrate to produce sound as air rushes up from lungs
What are vestibular folds( false vocal cords)?
◼️superior to vocal folds
◼️no part on sound production
◼️help to close glottis during swallowing
Epithelium of larynx:
◼️superior portion : stratified squamous epithelium
◼️inferior to vocal folds: pseudostratified ciliated columnar epithelium
Voice production:
◼️speech-intermittent release of expired air while opening and closing glottis
How is voice production pitch determined?
By length and tension of vocal cords
What does voice production loudness depend on?
Upon force of air
What chambers amplify and enhance sound quality?
◼️pharynx
◼️oral
◼️nasal
◼️sinus cavities
Sound is shaped into language by what?
Muscles of ▪️pharynx ▪️tongue ▪️soft palate ▪️lips
The larynx may act as ___ to prevent air passage?
Sphincter
Valsalva’s maneuver:
◼️glottis closes to prevent exhalation
◼️abdominal muscles contract
◼️intra-abdominal pressure rises
◼️helps to empty rectum or stabilizes trunk during heavy lifting
What is the trachea?
Windpipe- from larynx into mediastinum
What three layers compose the trachea?
◼️mucosa
◼️sub mucosa
◼️adventitia
Mucosa of trachea:
Ciliated pseudostratified epithelium with goblet cells
Submucosa of trachea:
Connective tissue with seromucous glands
Adventitia of trachea:
Outermost layer made of connective tissue ; encases C-shaped rings of hyaline cartilage
Trachealis:
◼️connects posterior parts of cartilage rings
◼️contracts during coughing to expel mucus
Carina:
◼️spar of cartilage on last, expanded tracheal cartilage
◼️point where trachea branches into two main bronchi
Bronchi and subdivisions:
◼️air passages undergo 23 orders of branching ➡️ bronchial (respiratory ) tree
◼️from tips of bronchial tree ➡️ conducting zone structures ➡️ respiratory zone structures
Conducting zone structures :
◼️trachea ➡️ right and left main(primary ) bronchi
◼️each main bronchus enters Hilum of one lung
-right main bronchus wider, shorter, more vertical than left
◼️each main bronchus branches into lobar (secondary) bronchi (three on right, two on left)
-each lobar bronchus supplies one lobe
Each lobar bronchus branches into what?
Segmental (tertiary ) bronchi
- segmental bronchi divide repeatedly
◼️branches become smaller and smaller :
-bronchioles = less than 1mm in diameter
-terminal bronchioles = smallest -less than 0.5 diameter
In conducting zone, from bronchi through bronchioles, structural changes occur :
◼️cartilage rings become irregular plates; in bronchioles elastic fibers replace cartilage
◼️epithelium chambers from pseudostratified columnar to cuboidal ; cilia and goblet cells become sparse
◼️relative punt of smooth muscle increases ➡️ allows constriction
Respiratory zone:
Begins as terminal bronchioles ➡️ respiratory bronchioles ➡️ alveolar ducts ➡️ alveolar ducts
Alveolar sacs contain what?
Clusters of alveoli
▪️~300 million alveoli make up most of lung volume
▪️sites of gas exchange
Respiratory membrane:
◼️alveolar and capillary walls and their fused basement membranes:
-~0.5 um thick; gas exchange across membrane by simple diffusion
◼️alveolar walls (single layer of squamous epithelium –type I alveolar cells )
◼️scattered cuboidal type II alveolar cells secrete cuboidal surfactant and anti microbial proteins
Alveoli is surrounded by what?
Fine elastic fibers and pulmonary capillaries
Alveolar pores:
Connect to adjacent alveoli.
▪️they equalize air pressure throughout lung
Alveolar macrophages:
Keep alveolar surfaces sterile
▪️2 million dead macrophages/hour carried by cilia➡️throat➡️swallowed
Lungs occupy the what?
Thoracic cavity except mediastinum
The roots of the lungs is:
The site of vascular and bronchial attachment to mediastinum
The lungs costal surface is:
Anterior, lateral, and posterior surfaces
Lungs are composed primarily of what?
Primarily of alveoli
The lungs balance :
Stroma- elastic connective tissue ➡️elasticity
The apex of the lungs :
Superior tip, deep to clavicle
The base of the lungs:
Inferior surface ; rests on diaphragm
The Hilum of the lungs:
On mediastinal surface; site for entry/exit of blood vessels, and nerves
The left lung is smaller than the right. True or false?
True
Cardiac notch:
Con cavity for heart
The right lung:
Superior , middle, inferior lobes separated by oblique and horizontal fissures
Bronchopulmonary segments:
(10 right , 8-10 left) separated by connective tissue septa
▪️ if diseased can be individually removed
Lobules:
Smallest subdivisions visible to naked eye; served by bronchioles and their branches
Pulmonary circulation:
(Low pressure, high volume)
Pulmonary arteries:
Deliver systemic venous blood to lungs for oxygenation
▪️branch profusely, feed into pulmonary capillary networks
Pulmonary veins :
Carry oxygenated blood from respiratory zones to heart
The lung capillary epithelium contains ____ to act on substances in blood?
Enzymes
Ex: angiotensin-converting enzyme- activates blood pressure hormone
What do Bronchial arteries do?
Provide oxygenated blood to lung tissue
Bronchial arteries:
▪️arise from aorta and enter lungs at Hilum
▪️part of systemic circulation (high pressure, low volume)
▪️supply all lung tissue except alveoli
▪️bronchial veins anastomose with pulmonary veins (pulmonary veins carry most venous blood back to heart)
What is pleurae?
Thin, double layered serosa; divides thoracic cavity into two pleural compartments and mediastinum
Parietal pleurae:
On thoracic wall, superior face of diaphragm, around heart, between lungs
Visceral pleurae:
On external surface of lungs
Pleural fluid:
Fills slit like pleural cavity
-Provides lubrication and surface tension ➡️assists in expansion and recoil
Pulmonary ventilation consists of two phases:
◼️inspiration -gases flow into lungs
◼️expiration- gases exit lungs
Atmospheric pressure:
◼️pressure exerted by air surrounding body
◼️760 mm Hg at sea level = 1 atmosphere
Respiratory pressures described relative to P ATM:
◼️negative respiratory pressure- less than P ATM
◼️positive respiratory pressure -greater than P ATM
◼️zero respiratory pressure = P ATM
Intrapulmonary pressure(intra-alveolar) P pul:
◼️pressure in alveoli
◼️fluctuations with breathing
◼️always eventually equalizes with P ATM
Intrapleural pressure(Pip):
◼️pressure in pleural cavity
◼️fluctuates with breathing
◼️always NEGATIVE pressure
◼️fluid level must be minimal
▪️pumped out by lymphatics
▪️if accumulates ➡️ positive Pip pressure ➡️ lung collapseNegative Pip caused by opposing forces:
◼️two inward forces promote lung collapse
▪️elastic recoil of lungs decreases lung size
▪️surface tension of alveolar fluid reduces alveolar size
◼️one outward force tends to enlarge lungs
▪️elasticity of chest wall pulls thorax outward
Pressure relationships:
◼if Pip = Ppul or Patm ➡️➡️lung collapse
Ppul - Pip = transpulmonary pressure :
◼️keeps airways open
◼️greater trans pulmonary pressure ➡️larger lungs
Atelectasis(lung collapse):
◼️plugged bronchioles = collapse of alveoli
◼️pneumothorax : air in pleural cavity
▪️from either wound in pariet or rupture of visceral pleura
▪️treated by removing air with chest tubes; pleurae heal ➡️lung reinflates
Pulmonary ventilation :
◼️inspiration and expiration
◼️mechanical processes that depend on volume changes in thoracic cavity :
▪️volume changes➡️pressure changes
▪️pressure changes ➡️gases flow to equalize pressure
Boyle’s Law :
◼️relationship between pressure and volume of a gas
▪️gases fill container; if container size reduced ➡️increased pressure
◼️pressure (P) varies inversely with volume (V) :
P1V1= P2V2
Inspiration:
◼️active processes:
▪️inspiration muscles (diaphragm and external intercostals) contract
▪️thoracic volume increases ➡️intra pulmonary pressure drops (to -1mm Hg)
▪️lungs stretched and intra pulmonary volume increases
▪️air flows into lungs, down its pressure gradient until Ppul= Patm
Forced inspiration:
Vigorous excerise, COPD➡️ ACCESSORY MUSCLES (scalene a, sternoccleidomastoid, pectorals minor)➡️ further increase in thoracic cage size
Quiet expiration normally passive process:
◼Inspiratory muscles relax
◼️thoracic cavity volume decreases
◼️elastic lungs recoils and intra pulmonary volume decreases ➡️pressure increases (Ppul rises to +1 mmHg) ➡️
◼️air flows out of lungs down its pressure gradient until Ppul= 0
Forced expiration- active process uses abdominal (oblique and transverse) and internal intercostal muscles. True or false ?
True
Three physical factors influencing pulmonary ventilation:
◼️airway resistance
◼️alveolar surface tension
◼️lung compliance
Airway resistance:
◼️friction- major non elastic source of resistance to gas flow; occurs in airways
◼️relationship between flow (F) pressure (P ) and resistance (R) is:
F=
Airway resistance is usually insignificant :
◼️large airway diameters in first part of conducting zone
◼️progressive branching of airways as get smaller, increasing greatest in medium-sized bronchi
◼️resistance disappears at terminal bronchioles where diffusion drives gas movement
As airway resistance rises, breathing movements become more what?
Strenuous
Severe constriction or obstruction of bronchioles:
◼️can prevent life sustaining ventilation
◼️can occur during acute asthma attacks; stops ventilation
Epinephrine dilates bronchioles , reduces what ?
Air resistance
Surface tension:
◼️attracts liquid molecules to one another at gas-liquid interface
◼️resisted any force that tends to increase surface area of liquid
◼️water-high tension; coats alveolar walls➡️ reduces them to smallest size
Lung compliance :
◼️measure of change in lung volume that occurs with given change in trans pulmonary pressure
◼️higher lung compliance ➡️easier to expand lungs
◼️normally high due to :
-distensibility of lung tissue
-surfactant , which decreases alveolar surface tension
Lung compliance is diminished by:
◼️non elastic scar tissue replacing lung tissue (fibrosis)
◼️reduced production of surfactant
◼️decreased flexibility of thoracic cage
Total respiratory compliance is also influenced by compliance of the thoracic wall which is decrease by:
◼️deformities of thorax
◼️ossification of costal cartilage
◼️paralysis of intercostal muscles
Used to assess respiratory status:
◼️tidal volume (TV)
◼️Inspiratory reserve volume(IRV)
◼️exploratory reserve volume(ERV)
◼️residual volume (RV)
Respiratory capacities:
◼️Inspiratory capacity (IC)
◼️functional residual capacity (FRC)
◼️vital capacity (VC)
◼️total lung capacity (TLC)
Anatomical dead space:
◼️no contribution to gas exchange
◼️air remaining in passageways ; ~150 ml
Alveolar dead space:
Non functional alveoli Due to collapse or obstruction
Total dead space:
Sum of anatomical and alveolar dead space
Spirometer:
Instrument for measuring respiratory volumes and capacities.
Spirometer can distinguish between :
▪️obstructive pulmonary disease
▪️restrictive disorders
Obstructive pulmonary disease:
Increased airway resistance (ex: bronchitis )
◼️TLC ,FRC ,RV may increase
Restrictive disorders:
Reduced TLC due to disease or fibrosis
◼️VC, TLC ,RV decline
To measure RATE of gas movement :
◼️forced vital capacity (FVC)
◼️forced exploratory volume (FEV)
Forced vital capacity:
Gas forcibly expelled after taking deep breath
Forced exploratory volume :
Amount of gas expelled during one specific time intervals or FVC
Minute ventilation:
Total amount if gas flow into or out of respiratory tract in one minute:
▪️normal at rest = ~6 L/min
▪️normal with excerise = up to 200L/min
▪️only rough estimate of respiratory efficiency
Alveolar ventilation:
◼️good indicator of effective ventilation
◼️alveolar ventilation rate (AVR) - flow of gases into and out of alveoli during a particular time
◼️dead space normally constant
◼️rapid, shallow breathing decreases AVR
Non respiratory air movements:
◼️May modify normal respiratory rhythm
◼️most result from reflex action; some voluntary
◼️examples include: cough, sneeze, crying, laughing, hiccups, and yawns
Gas exchange between blood, lungs, and tissues : external respiration:
Diffusion of gases in lungs
Gas exchange between blood, lungs, and tissues : internal respiration:
Diffusion of gases at body tissues
Gas exchange between blood, lungs, and tissues : external/internal respiration both involve ?
◼️physical properties if gases
◼️composition of alveolar gas
Dalton’s Law of Partial Pressures :
◼️total pressure exerted by mixture of gases = sum of pressure extorted by each gas
◼️partial pressure:
▪️pressure exerted by each gas mixture
▪️directly proportion to its percentage in mixture
Henry’s Law:
◼️gas mixtures in contact with liquid:
▪️each gas dissolves in proportion to its partial pressure
▪️at equilibrium , partial pressures in two phases will be equal
▪️amount of each gas that will dissolve depends on:
-solubility -CO2 20 times more soluble in water than O2 ; little N2 dissolves in water
-temperature- as temperature rises, solubility decreases
-
Alveoli contain more CO2 and water vapor than atmospheric air:
◼️gas exchange in lungs
◼humidification of air
◼️mixing of alveolar gas with each breath
External respiration:
◼️exchange of of O2 and CO2 across respiratory membrane
◼️influenced by :
▪️thickness and surface area of respiratory membrane
▪️partial pressure gradients and gas solubilities
▪️ventilation-perfusion coupling
Thickness of respiratory membranes :
◼️0.5 to 1 u m thick
◼️large total surface area (40 minutes that of skin) for gas exchange
Respiratory membranes thicken if lungs become waterlogged and edematous➡️
Gas exchange inadequate
Reduced surface area in emphysema (walls of adjacent alveoli break down) , rumors, inflammation, mucus. True or false?
True
Steel partial pressure gradient for O2 in lungs :
◼️venous blood Po2 = 40 mm Hg
◼️alveolar Po2 = 104 mmHg
▪️drives oxygen flow to blood
▪️equilibrium reached across respiratory membrane in ~ .25 seconds, about 1/3 time a red bold cell in pulmonary capillary ➡️adequate oxygenation even if blood flow increases 3X
Parties pressure gradient for CO2 in lungs less steep:
◼️venous blood Pco2 = 45 mm Hg
◼️alveolar Pco2 = 40 mmHg
◼️though gradient not as steep, CO2 diffuse in equal amounts with oxygen :
▪️CO2 20 times more soluble in plasma than oxygen
Perfusion is :
Blood flow reaching alveoli
Ventilation is:
Amount of GAS reaching alveoli
Ventilation and perfusion matched (coupled) for efficient gas exchange :
◼️never balanced for all alveoli due to:
▪️regional variations due to effect of gravity on blood and air flow
▪️some alveolar ducts plugged with mucus
Perfusion:
Changes in Po2 in alveoli cause changes in diameters of Arterioles :
▪️where alveolar O2 is high, Arterioles dilate
▪️where alveolar O2 is low, Arterioles constrict
▪️directs most blood where alveolar oxygen high
Changes in Pco2 in alveoli cause changes in diameters of bronchioles :
◼️where alveolar CO2 is high, bronchioles dilate
◼️where alveolar CO2 is low, bronchioles constrict
◼️allows elimination of CO2 more rapidly
Internal respiration:
◼️capillary gas exchange in body tissues
◼️partial pressures and diffusion gradients reversed compared to external respiration :
▪️tissue Po2 always lower than in systemic arterial blood➡️oxygen from blood tissues
▪️CO2 ➡️from tissues to blood
▪️venous blood Po2 40 mmHg and Pco2 45 mmHg
▪️
Transports of respiratory gases by blood:
◼️oxygen transport
◼️Carson dioxide transport
O2 (oxygen) transport:
◼️molecular O2 carried on blood:
▪️1.5 % dissolved in plasma
▪️98.5% loosely bound to each Fe of myoglobin (Hb) in RBCs
4 O2 per Hb
Oxyhemoglobin :(HbO2)
Hemoglobin-O2 combination
Reduced hemoglobin (deoxyhemoglobin) (HHb)-
Hemoglobin that has released O2
Loading and unloading of O2 facilitated by change in shape of Hb:
◼️As O2 binds, Hb affinity for O2 increases
◼️as O2 is released, Hb affinity for O2 decreases
◼️fully saturated: 100% if all four heme groups carry O2
◼️partially saturated when one to three hemes carry O2
Rate of loading and unloading of O2 regulated to ensure adequate oxygen delivery to cells:
◼️Po2 ◼️temperature ◼️blood pH ◼️Pco2 ◼️concentration- of BPG- produced by RBCs during glycolysis ; levels rise when oxygen levels chronically low
Influence of Po2 on hemoglobin saturation:
◼️oxygen-hemoglobin dissociation curve
◼️hemoglobin saturation plotted against Po2 not linear; S-shaped curve
▪️binding and release of O2 influenced by Po2
Influence of Po2 on hemoglobin saturation : In arterial blood:
◼️Po2 = 100 mmHg
◼️contains 20 ml oxygen per 100 ml blood (20 vol%)
◼️Hb is 98% saturated
◼️further increases in Po2 (ex: breathing deeaply) produce minimal increase in O2 binding
Influence of Po2 on hemoglobin saturation : in venous blood:
◼️Po2 = 40mmHg
◼️contains 15 vol % oxygen
◼️Hb is 85% saturated
◼️venous reserve : oxygen remaining in venous blood
Other factors influencing hemoglobin saturation :
◼️increases in temperature , H+ , Pco2, and BPG:
▪️modify structure of hemoglobin ; decrease its affinity for O2
▪️occur in systemic capillaries
▪️enhance O2 unloading from blood
▪️shift O2- hemoglobin dissociation curve to right
◼️decreases in these factors shift curve to left :
▪️decreases oxygen unloading from blood
Factors that increase release of O2 by hemoglobin:
◼️as cells metabolize glucose and use O2:
▪️Pco2 and H+ increase in capillary blood ➡️
▪️declining blood pH and increasing Pco2 ➡️
-Bohr effect: Hb-O2 bond weakens➡️oxygen unloading where needed most
▪️heat production increases ➡️directly and indirectly decreases Hb affinity for O2➡️increased oxygen unloading to active tissues
Hypoxia :
Inadequate O2 delivery to tissues ➡️cyanosis
Anemic hypoxia :
Too few RBC ; abnormal or too little Hb
Ischemic hypoxia :
Impaired / blocked circulation
Histotoxic hypoxia:
Cells unable to use O2 , as in metabolic poisons
Hypoxemic hypoxia :
Abnormal ventilation ; pulmonary disease
Carbon monoxide poisoning :
Especially from fire; 200X greater affinity for Hb than oxygen
CO2 transport:
◼️CO2 transported in blood in three forms:
▪️7 to 10% dissolved in plasma
▪️20% bound to glob in of hemoglobin
▪️70% transported as bicarbonate ions (HCO3-) in plasma
Transport and exchange of CO2:
◼️CO2 combines with water to form carbonic acid (H2CO23) which quickly dissociates
◼️occurs primarily in RBCs where carbonic anhydrase reversibly and rapidly catalyzes reaction
Transport and exchange of CO2 : in systemic capillaries:
◼️HCO3- Quickly diffuses from RBCs Into plasma :
▪️chloride shift occurs : outrush of HCO3- from RBCs balanced as Cl- moves into RBCs from plasma
Transport and exchange of CO2 : on pulmonary capillaries:
◼️HCO3- moves into RBCs (while Cl- moves out) ; binds with H+ to form H2CO3
◼️H2CO3 split by carbonic anhydrase into CO2 and water
◼️CO2 diffuses into alveoli
Haldane effect: amount of CO2 transported affected by Po2:
▪️reduced hemoglobin (less oxygen saturation ) forms carbonaminohemoglobin and buffers H+ more easily ➡️
▪️lowers Po2 and hemoglobin saturation with O2; more CO2 carried in blood
◼️encourages CO2 exchange in tissues and lungs
Haldane effect : at tissues as more CO2 enters blood :
◼️more oxygen dissociates from hemoglobin (Bohr effect)
◼️as Hbo2 releases O2, it more readily forms binds with CO2 to form carbaminohemoglobin
Carbonic acid-bicarbonate buffer system:
Resists change a in blood pH
▪️if H+ in blood rises, excess H+ is removed by combining with HCO3- ➡️H2CO3
▪️if H+ concentration begins to drop, H2CO3 dissociates , releasing H+
▪️HCO3- is alkaline reserve of carbonic acid-bicarbonate buffer system
Influence of CO2 on blood pH:
Changes in respiratory rate and depth affect blood pH:
◼️slow, shallow breathing➡️increased CO2 in blood➡️ drop in pH
◼️rapid, deep breathing ➡️decreased CO2 in blood➡️ rise in pH
◼️changes in ventilation can adjust pH when disturbed by metabolic factors
Control of respiration:
◼️involves higher brain centers, chemoreceptors , and other reflexes
◼️neural controls
What are the neural controls of respiration?
◼️neurons in reticular formation of medulla and pons
◼️clustered neurons in medulla important :
▪️ventral respiratory group
▪️dorsal respiratory group
Ventral respiratory group (VRG) :
Rhythm:
Generating and integrative center.
-sets eupnea (12-15 breaths/ min) —normal respiratory rate and rhythm
Ventral respiratory group (VRG) :
Inspiratory neurons excite Inspiratory muscles via ___ and ___?
Via phrenic (diaphragm) And Intercostal nerves (external intercostals)
Ventral respiratory group (VRG) :
Exploratory neurons inhibit ___?
Inspiratory neurons
Dorsal respiratory group (DRG):
◼️near root of cranial nerve IX
◼️integrates input from peripheral stretch and chemoreceptors ; sends information ➡️ VRG
Pontine respiratory centers:
◼️influence and modify activity of VRG
◼️smooth out transition between inspiration and expiration and vice versa
◼️transmit impulses to VRG➡️modify and fine-tune breathing rhythms during vocalization, sleep, exercise
Generation of the respiratory system:
◼️not well understood
◼️one hypophysis :
▪️pacemaker neurons with intrinsic rhythmicity
◼️most widely accepted hypothesis
▪️reciprocal inhibition of two sets of interconnected pacemaker neurons in medulla that generates rhythm
Factors influencing breathing rate and depth:
◼️depth determined by how actively respiratory center stimulates respiratory muscles
◼️rate determined by how long Inspiratory center active
◼️both modified in response to changing body demands:
▪️most important are changing levels of CO2 , O2, and H+
▪️sensed by central and peripher chemoreceptors
Chemical factors : influence of Pco2 ( most potent; most closely controlled) :
◼️of blood Pco2 levels rise (hypercapnia) CO2 accumulates in brain➡️
◼️CO2 in brain hydrated ➡️carbonic acid➡️dissociates, releasing H+➡️ pH drops
◼️H+ stimulates central chemoreceptors of brain stem
◼️chemoreceptors synapse with respiratory regulatory centers➡️increased depth and rate of breathing ➡️lower blood Pco2➡️ pH rises
Hyperventilation:
◼️increased depth and rate of breathing that exceeds body’s need to remove Co2
▪️➡️decreased blood CO2 levels (hypocapnia)
▪️➡️cerebral vasoconstriction and cerebral ischemia
➡️dizziness , fainting
Apnea:
Breathing cessation; may be due to abnormally low Pco2
Chemical factors: influence of Po2:
◼️peripheral chemoreceptors in aortic and carotid bodies– arterial O2 level sensors
▪️when excited, cause respiratory center to increase ventilation
◼️declining Po2, normally slight effect on ventilation :
▪️huge O2 reservoir bound to Hb
▪️requires substantial drop in arterial Po2 (to 60 mm Hg) to stimulate increased ventilation
Chemical factors: influence of arterial pH:
◼️can modify respiratory rate and rhythm even if CO2 and O2 levels normal
◼️mediated by peripheral chemoreceptors
◼️decreased pH may reflect
▪️CO2 retention; accumulation of lactic acid; excess ketone bodies
◼️respiratory system controls attempt to raise pH by increasing respiratory rate and depth
Summary of chemical factors:
◼️rising CO2 levels most powerful respiratory stimulant
◼️normally blood Po2 affects breathing by indirectly by influencing peripheral chemoreceptors sensitivity to changes in Pco2
When arterial Po2 falls below 60mm Hg, it becomes major stimulus for ___?
Respiration (via peripheral chemoreceptors )
Changes in arterial pH resulting from Co2 retention or metabolic factors act indirectly through __?
Peripheral chemoreceptors
Hypothalamic controls:
◼️act through limbic system to modify rate and depth of respiration (ex:breath holding that occurs in anger or gasping with pain)
◼️rise in body temperature increases respiratory rate
Cortical controls:
Direct signals from cerebral motor cortex that bypass medullary controls
(Ex: voluntary breath holding. Brain stem reinstates breathing when blood CO2 critical)
Pulmonary irritant reflexes:
◼️receptors on bronchioles respond to irritants :
▪️communicate with respiratory centers via Vagal nerve afferents
◼️promote reflective constriction of air passages
◼️same irritant ➡️cough in trachea or bronchi ; sneeze in nasal cavity
Hering-Breuer Reflex (inflation reflex):
◼️stretch receptors in pleurae and airways stimulated by lung inflation
▪️inhibitory signals to medullary respiration centers end inhalation and allow expiration
▪️acts as protective response more than normal regulatory mechanism
Respiratory adjustments geared to both __ and __?
Intensity
And
Duration if exercise
Hyperpnea:
◼️increased ventilation (10 to 20 fold) in response to metabolic needs
What 3 factors remain constant during exercise?
◼️Pco2
◼️Po2
◼️pH
3 neural factors cause increase in ventilation as exercise begins:
◼️psychological stimuli: anticipation of exercise
◼️simultaneous cortical motor activation of skeletal muscles and respiratory centers
◼️excitatory impulses to respiratory centers from proprioceptora in moving muscles , tendons, joints
Respiratory adjustments: exercise:
◼️ventilation declines suddenly as exercise ends because the three neural factors shut off
◼️gradual decline to baseline because of decline in CO2 flow after exercise ends
◼️exercise ➡️anaerobic respiration➡️lactic acid
▪️not from poor respiratory function; from insufficient cardiac output or skeletal muscle inability to increase oxygen uptake
High altitude :
◼️quick travel to altitudes above 2400 meters (8000 feet) may ➡️symptoms of acute mountain sickness (AMS)
▪️atmospheric pressure and Po2 levels lower
▪️headaches, shortness of breath, dizziness , nausea
▪️in severe cases, lethal cerebral and pulmonary edema
Acclimatization:
◼️respiratory and hematopoietic adjustments to long-term move to high altitude
▪️chemoreceptors become more responsive to Pco2 when Po2 declines
▪️substantial decline in Po2 directly stimulates peripheral chemoreceptors
▪️result – minute ventilation increases and stabilizes in few days to 2-3 L/min higher than at sea level
Acclimatization to high altitude is always __ than normal Hb saturation levels?
Lower than normal.
-less O2 available
Decline in blood O2 stimulates ___ to accelerate production of EPO?
Kidneys
RBC numbers ___ to provide long-term compensation?
Increase slowly
Chronic obstructive pulmonary disease:
◼️exemplified by chronic bronchitis and emphysema
◼️irreversible decrease on ability to force air out of lungs
◼️other common features:
▪️history of smoking in 80% of patients
▪️dyspnea: labored breathing “air hunger”
▪️coughing and frequent pulmonary infections
▪️most develop respiratory failure (hypo ventilation) accompanied by respiratory acidosis, hypoxemia
Emphysema:
◼️permanent enlargement of alveoli; destruction of alveolar walls ; decreased lung elasticity ➡️
▪️accessory muscles necessary for breathing
-exhaustion from energy usage
▪️hyperinflation➡️flattened diaphragm ➡️reduced ventilation efficiency
▪️damaged pulmonary capillaries➡️enlarged right ventricle
Chronic bronchitis:
◼️inhaled irritants➡️chronic excessive mucus ➡️
◼️inflamed and fibrosis lower respiratory passageways➡️
◼️obstructed airways➡️
◼️impaired lung ventilation and gas exchange ➡️
◼️frequent pulmonary infections
COPD symptoms:
◼️strength of innate respiratory drive ➡️different symptoms in patients
▪️”pink” buffers -thin bear normal blood gases
▪️”blue” buffers - stocky , hypoxic
COPD treatment :
Treated with : ▪️bronchodilators ▪️corticosteroids ▪️oxygen ▪️sometimes surgery
Asthma -reversible COPD:
◼️characterized by coughing, dyspnea, wheezing, and chest tightness
◼️active inflammation of airways precedes bronchospasms
◼️airway inflammation is immune response caused by release of interleukins, production of IgE , and recruitment of inflammatory cells
◼️airways thickened with inflammatory exudate magnify effect of bronchspasms
Tuberculosis(TB):
◼️infectious disease caused by bacterium Mycobacterium tuberculosis
◼️symptoms: fever, night sweats, weight loss, racking cough , coughing up blood
◼️treatment -12 month course of antibiotics
▪️are antibiotic resistant strains
Lung cancer:
◼️leading cause of cancer deaths in North America ◼️90% of all cases result of smoking ◼️three most common types: ▪️adenocarcinoma ▪️squamous cell carcinoma ▪️small cell carcinoma
Adenocarcinoma:
(40% of cases)
Originates in peripheral lung areas -bronchi glands, alveolar cells
Squamous cell carcinoma:
(20-40% of cases)
In bronchial epithelium
Small Cell carcinoma:
(20% of cases)
Contains lymphocyte-like cells that originate in primary bronchi and subsequently meta size
___ scan better than chest X ray?
Helical CT scan
Of no metastasis __?
Then surgery to remove diseased lung tissue
If metastasis__?
Radiation and chemotherapy
New therapies for lung cancer:
◼️antibodies target growth factors required by Timor ; or deliver toxic agents to tumor
◼️cancer vaccines to stimulate immune system
◼️gene therapy to replace defective genes
Which structures develop first?
Upper respiratory structures
Olfactory placodes:
Invaginate into olfactory pits (> nasal cavities ) by fourth week
Laryngotracheal bud:
Present by 5th week
Mucosae of bronchi and lung alveoli present by what week?
8th week
By what week can a premature baby breathe on its own?
28th
How does gas exchange take place in fetus?
Via placenta
Cystic fibrosis:
◼️most common lethal genetic disease in North America
◼️abnormal viscous mucus clogs passageways ➡️bacterial infections
▪️affects lungs , pancreatic ducts, reproductive ducts
◼️cause abnormal gene for Cl- membrane channel
Treatment for cystic fibrosis :
◼️mucus - dissolving drugs ; manipulation to loosen mucus ; antibiotics
◼️research into:
▪️introducing normal genes
▪️prodding different protein➡️ Cl- channel
▪️feeding patients abnormal protein from ER to ➡️Cl- channels
▪️inhaling hypertonic saline to thin mucus
At birth , respiratory centers activated __ and __ ?
◼️alveoli inflate
◼️lungs begin to function
Respiratory rate highest in __?
Newborns and slows until adulthood
Lungs continue to mature and more alveoli formed until ___?
Young adulthood
Respiratory efficiency decreases in __ ?
Old age
