RESPIRATORY SYSTEM ANATOMY & PHYSIOLOGY

WHY DO WE BREATHE? THINK OF ALL THE

REASONS WHY WE NEED A RESPIRATORY SYSTEM.

RESPIRATION

RESPIRATION In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction.

Breathing (which in organisms with lungs is called ventilation and includes inhalation and exhalation) is a part of physiologic respiration. Thus, in precise usage, the words breathing and ventilation are hyponyms, not synonyms, of respiration; but this prescription is not consistently followed, even by most health care providers, because the term respiratory rate (RR) is a well-established term in health care, even though it would need to be consistently replaced with ventilation rate if the precise usage were to be followed.

RESPIRATION “Respiration” is used several different ways: Cellular respiration is the aerobic breakdown of glucose in the mitochondria to make ATP. Respiratory systems are the organs in animals that exchange gases with the environment. “Respiration” is an everyday term that is often used to mean “breathing.”

RESPIRATION Breathing (pulmonary ventilation). consists of two cyclic phases: inhalation, also called inspiration - draws gases into the lungs. exhalation, also called expiration - forces gases out of the lungs.

FUNCTIONS Respiration includes the following processes:

1. Ventilation or breathing 2. The exchange of oxygen and carbon dioxide between the air in the lungs and blood 3. Transport of oxygen and carbon dioxide in the blood 4. The exchange of oxygen and carbon dioxide between the blood and the tissues.

FUNCTIONS1. supplies the body with oxygen and

disposes of carbon dioxide2. filters inspired air3. produces sound4. contains receptors for smell5. rids the body of some excess water and

heat6. helps regulate blood pH

FUNCTIONS·Oversees gas exchanges (oxygen and carbon dioxide) between the blood and external environment·Exchange of gasses takes place within the lungs in the alveoli(only site of gas exchange, other structures passageways·Passageways to the lungs purify, warm, and humidify the incoming air·Shares responsibility with cardiovascular system

Anatomy of the Respiratory system

· Nose· Pharynx· Larynx· Trachea· Bronchi· Lungs –

alveoli

Upper Respiratory Tract

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NOSE Functions warms, cleanses, humidifies inhaled air detects odors resonating chamber that amplifies the voice

Bony and cartilaginous supports superior half: nasal bones medially and maxillae laterally inferior half: lateral and alar cartilages ala nasi: flared portion shaped by dense CT, forms lateral wall of each nostril

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ANATOMY OF NASAL REGION

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ANATOMY OF NASAL REGION

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NASAL CAVITY Extends from nostrils to posterior nares Vestibule: dilated chamber inside ala nasistratified squamous epithelium, vibrissae (guard hairs)

Nasal septum divides cavity into right and left chambers called nasal fossae

Nasal cavity Nasal septum divides the cavity into

right and left portionsNares – openings of the nose

Nasal conchae extend from walls of nasal cavity

Mucous membrane warms and moistens the air

Cilia help eliminate particles

Paranasal sinuses Air-filled spaces

within the skull bones Open into the nasal

cavity

Reduce the weight of the skull

Equalizes pressure

Gives the voice its certain tone

Skull bones with sinuses include:FrontalSphenoidEthmoidMaxillae bones

UPPER RESPIRATORY TRACT

UPPER RESPIRATORY TRACT

NASAL CAVITY - CONCHAE AND MEATUSES Superior, middle and inferior nasal conchae3 folds of tissue on lateral wall of nasal fossamucous membranes supported by thin scroll-like turbinate bones

Meatusesnarrow air passage beneath each conchaenarrowness and turbulence ensures air contacts mucous membranes

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NASAL CAVITY - MUCOSA

Olfactory mucosa lines roof of nasal fossa Respiratory mucosa lines rest of nasal cavity with ciliated pseudostratified epithelium

Defensive role of mucosamucus (from goblet cells) traps inhaled particlesbacteria destroyed by lysozyme

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NASAL CAVITY - CILIA AND ERECTILE TISSUE Function of cilia of respiratory epitheliumsweep debris-laden mucus into pharynx to be swallowed

Erectile tissue of inferior conchavenous plexus that rhythmically engorges with blood and shifts flow of air from one side of fossa to the other once or twice an hour to prevent drying

Spontaneous epistaxis (nosebleed)most common site is inferior concha

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REGIONS OF PHARYNX

Structures of the Pharynx

· Auditory tubes enter the nasopharynx

· Tonsils of the pharynx·Pharyngeal tonsil (adenoids) in the nasopharynx

·Palatine tonsils in the oropharynx

·Lingual tonsils at the base of the tongue

PHARYNX Nasopharynx (pseudostratified epithelium) posterior to choanae, dorsal to soft palate receives auditory tubes and contains pharyngeal tonsil 90 downward turn traps large particles (>10m)

Oropharynx (stratified squamous epithelium) space between soft palate and root of tongue, inferiorly as far as hyoid bone, contains palatine and lingual tonsils

Laryngopharynx (stratified squamous) hyoid bone to level of cricoid cartilage

Larynx (Voice Box)

· Routes air and food into proper channels

· Plays a role in speech· Made of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (epiglottis)

Structures of the Larynx

· Thyroid cartilage·Largest hyaline cartilage·Protrudes anteriorly (Adam’s apple)

· Epiglottis·Superior opening of the larynx·Routes food to the larynx and air toward the trachea

Structures of the Larynx

· Vocal cords (vocal folds)·Vibrate with expelled air to create sound (speech)

· Glottis – opening between vocal cords

LARYNX Glottis – vocal cords and opening between Epiglottis flap of tissue that guards glottis, directs food and drink to esophagus

Infant larynx higher in throat, forms a continuous airway from nasal cavity that allows breathing while swallowing

by age 2, more muscular tongue, forces larynx down

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VIEWS OF LARYNX

NINE CARTILAGES OF LARYNX Epiglottic cartilage - most superior Thyroid cartilage – largest; laryngeal prominence Cricoid cartilage - connects larynx to trachea Arytenoid cartilages (2) - posterior to thyroid cartilage Corniculate cartilages (2) - attached to arytenoid cartilages like a pair of little horns Cuneiform cartilages (2) - support soft tissue between arytenoids and epiglottis

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WALLS OF LARYNX Interior wall has 2 folds on each side, from thyroid to arytenoid cartilages vestibular folds: superior pair, close glottis during swallowing vocal cords: produce sound

Intrinsic muscles - rotate corniculate and arytenoid cartilagesadducts (tightens: high pitch sound) or abducts (loosens: low pitch sound) vocal cords

Extrinsic muscles - connect larynx to hyoid bone, elevate larynx during swallowing

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ACTION OF VOCAL CORDS

TRACHEA Rigid tube 4.5 in. long and 2.5 in. diameter, anterior to esophagus Supported by 16 to 20 C-shaped cartilaginous ringsopening in rings faces posteriorly towards esophagustrachealis spans opening in rings, adjusts airflow by expanding or contracting

Larynx and trachea lined with ciliated pseudostratified epithelium which functions as mucociliary escalator

Trachea (Windpipe)· Connects larynx with bronchi· Lined with ciliated mucosa

·Beat continuously in the opposite direction of incoming air

·Expel mucus loaded with dust and other debris away from lungs

· Walls are reinforced with C-shaped hyaline cartilage

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LOWER RESPIRATORY TRACT

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LUNGS - SURFACE ANATOMY

Lungs· Occupy most of the thoracic

cavity·Apex is near the clavicle (superior portion)·Base rests on the diaphragm (inferior portion)

·Each lung is divided into lobes by fissures·Left lung – two lobes·Right lung – three lobes

Lungs

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LUNG TISSUE

Coverings of the Lungs

· Pulmonary (visceral) pleura covers the lung surface

· Parietal pleura lines the walls of the thoracic cavity

· Pleural fluid fills the area between layers of pleura to allow gliding

Respiratory Tree Divisions

· Primary bronchi· Secondary bronchi· Tertiary bronchi· Bronchioli· Terminal bronchioli

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BRONCHIAL TREE Primary bronchi (C-shaped rings)from trachea; after 2-3 cm enter hilum of lungsright bronchus slightly wider and more vertical (aspiration)

Secondary (lobar) bronchi (overlapping plates)one secondary bronchus for each lobe of lung

Tertiary (segmental) bronchi (overlapping plates)10 right, 8 leftbronchopulmonary segment: portion of lung supplied by each

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BRONCHIAL TREE Bronchioles (lack cartilage) layer of smooth musclepulmonary lobule

portion ventilated by one bronchioledivides into 50 - 80 terminal bronchioles

ciliated; end of conducting divisionrespiratory bronchioles

divide into 2-10 alveolar ducts; end in alveolar sacs

Alveoli - bud from respiratory bronchioles, alveolar ducts and alveolar sacsmain site for gas exchange

Bronchioles

· Smallest branches of the bronchi

Bronchioles

· All but the smallest branches have reinforcing cartilage

Bronchioles

· Terminal bronchioles end in alveoli

Respiratory Zone

· Structures· Respiratory bronchioli· Alveolar duct· Alveoli

· Site of gas exchange

Alveoli· Structure of alveoli

· Alveolar duct· Alveolar sac· Alveolus· Gas exchange

ALVEOLUS

Fig. 22.11b and c

ALVEOLAR BLOOD SUPPLY

Gas Exchange· Gas crosses the respiratory

membrane by diffusion·Oxygen enters the blood·Carbon dioxide enters the alveoli

· Macrophages add protection· Surfactant coats gas-exposed

alveolar surfaces

FACTORS AFFECTING GAS EXCHANGE

Concentration gradients of gasesPO

2 = 104 in alveolar air versus 40 in blood

PCO2 = 46 in blood arriving versus 40 in

alveolar air Gas solubilityCO2 20 times as soluble as O2

O2 has conc. gradient, CO2 has solubility

FACTORS AFFECTING GAS EXCHANGE

Membrane thickness - only 0.5 m thick Membrane surface area - 100 ml blood in alveolar capillaries, spread over 70 m2

Ventilation-perfusion coupling - areas of good ventilation need good perfusion (vasodilation)

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CONCENTRATION GRADIENTS OF GASES

AMBIENT PRESSURE AND CONCENTRATION GRADIENTS

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PERFUSION ADJUSTMENTS

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VENTILATION ADJUSTMENTS

Events of Respiration· Pulmonary ventilation – moving air in and out of the lungs

· External respiration – gas exchange between pulmonary blood and alveoli

Events of Respiration· Respiratory gas transport – transport of oxygen and carbon dioxide via the bloodstream

· Internal respiration – gas exchange between blood and tissue cells in systemic capillaries

Mechanics of Breathing

(Pulmonary Ventilation)· Completely mechanical

process· Depends on volume changes

in the thoracic cavity· Volume changes lead to

pressure changes, which lead to the flow of gases to equalize pressure

Mechanics of Breathing (Pulmonary Ventilation)

· Two phases·Inspiration – flow of air into lung

·Expiration – air leaving lung

Inspiration· Diaphragm and intercostal muscles contract

· The size of the thoracic cavity increases

· External air is pulled into the lungs due to an increase in intrapulmonary volume

Inspiration

Exhalation· Largely a passive process which depends on natural lung elasticity

· As muscles relax, air is pushed out of the lungs

· Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage

Exhalation

Nonrespiratory Air Movements· Can be caused by reflexes or

voluntary actions· Examples

·Cough and sneeze – clears lungs of debris

·Laughing·Crying·Yawn·Hiccup

Respiratory Volumes and Capacities· Normal breathing moves about 500

ml of air with each breath (tidal volume [TV])

· Many factors that affect respiratory capacity·A person’s size·Sex·Age·Physical condition

· Residual volume of air – after exhalation, about 1200 ml of air remains in the lungs

Respiratory Volumes and Capacities· Inspiratory reserve volume (IRV)

·Amount of air that can be taken in forcibly over the tidal volume

·Usually between 2100 and 3200 ml· Expiratory reserve volume (ERV)

·Amount of air that can be forcibly exhaled

·Approximately 1200 ml

Respiratory Volumes and Capacities·Residual volume

·Air remaining in lung after expiration

·About 1200 ml

Respiratory Volumes and Capacities

Slide 13.28

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· Vital capacity· The total amount of exchangeable air· Vital capacity = TV + IRV + ERV· Dead space volume

· Air that remains in conducting zone and never reaches alveoli

· About 150 ml

Respiratory Volumes and Capacities· Functional volume

·Air that actually reaches the respiratory zone

·Usually about 350 ml· Respiratory capacities are

measured with a spirometer

Respiratory Capacities

RESPIRATORY VOLUMES Different volumes of air move in and out of lungs with different intensities of breathing

Measured to assess health of respiratory system

RESPIRATORY VOLUMES (CONT.)

Amount of air that moves in or out of the lungs during a normal breath

Amount of air that can be forcefully inhaled following a normal inhalation

Amount of air that can be forcefully exhaled following a normal exhalation

Tidal Volume

InspiratoryReserve Volume

ExpiratoryReserve Volume

RESPIRATORY VOLUMES (CONT.)

Amount of air that can be forcefully exhaled after the deepest inhalation possible

Volume of air that always remains in the lungs even after a forceful exhalation

The total amount of air the lungs can hold

Residual Volume

Total LungCapacity

Vital Capacity

Respiratory Sounds

· Sounds are monitored with a stethoscope

· Bronchial sounds – produced by air rushing through trachea and bronchi

· Vesicular breathing sounds – soft sounds of air filling alveoli

THE TRANSPORT OF OXYGEN AND CARBON DIOXIDE IN THE BLOOD

Most of the oxygen binds to hemoglobin Oxyhemoglobin Bright red in color

Some oxygen remains dissolved in plasma

If CO2 combines with hemoglobin at O2 sites, it forms carboxyhemoglobin

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OXYGEN TRANSPORT Concentration in arterial blood20 ml/dl98.5% bound to hemoglobin1.5% dissolved

Binding to hemoglobineach heme group of 4 globin chains may bind O2 oxyhemoglobin (HbO2 )deoxyhemoglobin (HHb)

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OXYGEN TRANSPORT Oxyhemoglobin dissociation curverelationship between hemoglobin saturation and PO

2 is not a simple linear one

after binding with O2, hemoglobin changes shape to facilitate further uptake (positive feedback cycle)

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OXYHEMOGLOBIN DISSOCIATION CURVE

THE TRANSPORT OF OXYGEN AND CARBON DIOXIDE IN THE BLOOD Carbon dioxide gets into the bloodstreamReacts with water in plasma and forms carbonic acidCarbonic acid ionizes and releases hydrogen and bicarbonate ionsBicarbonate ions attach to hemoglobin Exhaled as waste product in the lungs

Gas Transport in the Blood

· Carbon dioxide transport in the blood·Most is transported in the plasma as bicarbonate ion (HCO3

–)·A small amount is carried inside red blood cells on hemoglobin, but at different binding sites than those of oxygen

Neural Regulation of Respiration· Activity of respiratory muscles is

transmitted to the brain by the phrenic and intercostal nerves

· Neural centers that control rate and depth are located in the medulla

· The pons appears to smooth out respiratory rate

· Normal respiratory rate (eupnea) is 12–15 respirations per minute

· Hypernia is increased respiratory rate often due to extra oxygen needs

Neural Regulation of Respiration

Factors Influencing Respiratory Rate and Depth

· Physical factors· Increased body temperature·Exercise·Talking·Coughing

· Volition (conscious control)· Emotional factors

Factors Influencing Respiratory Rate and Depth

· Chemical factors·Carbon dioxide levels

·Level of carbon dioxide in the blood is the main regulatory chemical for respiration

· Increased carbon dioxide increases respiration

·Changes in carbon dioxide act directly on the medulla oblongata

Factors Influencing Respiratory Rate and

Depth· Chemical factors (continued)·Oxygen levels

·Changes in oxygen concentration in the blood are detected by chemoreceptors in the aorta and carotid artery

· Information is sent to the medulla oblongata

SYSTEMIC GAS EXCHANGE CO2 loading carbonic anhydrase in RBC catalyzes

CO2 + H2O H2CO3 HCO3- + H+

chloride shiftkeeps reaction proceeding, exchanges HCO3

- for Cl- (H+ binds to hemoglobin)

O2 unloading H+ binding to HbO2 its affinity for O2

Hb arrives 97% saturated, leaves 75% saturated - venous reserve

utilization coefficient amount of oxygen Hb has released 22%

CHLORIDE SHIFT High C02 levels in tissues causes the

reaction C02 + H2O H2C03 H+ + HC03

- to shift right in RBCs Results in high H+ & HC03

- levels in RBCs H+ is buffered by proteins HC03

- diffuses down concentration & charge gradient into blood causing RBC to become more + So Cl- moves into RBC (chloride shift)

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CHLORIDE SHIFT

Fig 16.38

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REVERSE CHLORIDE SHIFT In lungs, C02 + H2O H2C03 H+ + HC03

-, moves to left as C02 is breathed out Binding of 02 to Hb decreases its affinity for H+H+ combines with HC03

-

& more C02 is formed Cl- diffuses down concentration & charge gradient out of RBC (reverse chloride shift)

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SYSTEMIC GAS EXCHANGE

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ALVEOLAR GAS EXCHANGE REVISITED Reactions are reverse of systemic gas exchange CO2 unloading as Hb loads O2 its affinity for H+ decreases, H+ dissociates from Hb and bind with HCO3

-

CO2 + H2O H2CO3 HCO3- + H+

reverse chloride shiftHCO3

- diffuses back into RBC in exchange for Cl-,

free CO2 generated diffuses into alveolus to be exhaled

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ALVEOLAR GAS EXCHANGE

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FACTORS AFFECT O2 UNLOADING Active tissues need oxygen!ambient PO

2: active tissue has PO

2 ; O2 is released

temperature: active tissue has temp; O2 is releasedBohr effect: active tissue has CO2, which lowers pH (muscle burn); O2 is released

bisphosphoglycerate (BPG): RBC’s produce BPG which binds to Hb; O2 is released body temp (fever), TH, GH, testosterone, and epinephrine all raise BPG and cause O2

unloading ( metabolic rate requires oxygen)

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OXYGEN DISSOCIATION AND TEMPERATURE

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OXYGEN DISSOCIATION AND PH

Bohr effect: release of O2 in response to low pH

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Haldane effect low level of HbO2 (as in active tissue) enables blood to transport more CO2 HbO2 does not bind CO2 as well as deoxyhemoglobin (HHb) HHb binds more H+ than HbO2

as H+ is removed this shifts the CO2 + H2O HCO3

- + H+

reaction to the right

FACTORS AFFECTING CO2 LOADING

ACID-BASE BALANCE IN BLOOD

Blood pH is maintained within narrow pH range by lungs & kidneys (normal = 7.4) Most important buffer in blood is bicarbonateH20 + C02 H2C03 H+ + HC03

-

Excess H+ is buffered by HC03-

Kidney's role is to excrete H+ into urine

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2 major classes of acids in body:A volatile acid can be converted to a gas E.g. C02 in bicarbonate buffer system can be breathed outH20 + C02 H2C03 H+ + HC03

- All other acids are nonvolatile & cannot leave bloodE.g. lactic acid, fatty acids, ketone bodies

ACID-BASE BALANCE IN BLOOD CONTINUED

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Acidosis is when pH < 7.35; alkalosis is pH > 7.45 Respiratory acidosis caused by hypoventilation Causes rise in blood C02 & thus carbonic acid

Respiratory alkalosis caused by hyperventilationResults in too little C02

ACID-BASE BALANCE IN BLOOD CONTINUED

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Metabolic acidosis results from excess of nonvolatile acidsE.g. excess ketone bodies in diabetes or loss of HC03

- (for buffering) in diarrhea Metabolic alkalosis caused by too much HC03

- or too little nonvolatile acids (e.g. from vomiting out stomach acid)

ACID-BASE BALANCE IN BLOOD CONTINUED

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Normal pH is obtained when ratio of HCO3- to

C02 is 20 : 1 Henderson-Hasselbalch equation uses C02 & HCO3

- levels to calculate pH: pH = 6.1 + log = [HCO3

-] [0.03PC02]

ACID-BASE BALANCE IN BLOOD CONTINUED

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RESPIRATORY ACID-BASE BALANCE Ventilation usually adjusted to metabolic rate to maintain normal CO2 levels With hypoventilation not enough CO2 is breathed out in lungsAcidity builds, causing respiratory acidosis With hyperventilation too much CO2 is breathed out in lungsAcidity drops, causing respiratory alkalosis

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VENTILATION DURING EXERCISE

During exercise, arterial PO2, PCO2, & pH remain fairly constant

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VENTILATION DURING EXERCISE During exercise, breathing becomes deeper & more

rapid, delivering much more air to lungs (hyperpnea) 2 mechanisms have been proposed to underlie this

increase: With neurogenic mechanism, sensory activity from

exercising muscles stimulates ventilation; and/or motor activity from cerebral cortex stimulates CNS respiratory centers

With humoral mechanism, either PC02 & pH may be different at chemoreceptors than in arteries

Or there may be cyclic variations in their values that cannot be detected by blood samples

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Developmental Aspects of the Respiratory System

· Lungs are filled with fluid in the fetus

· Lungs are not fully inflated with air until two weeks after birth

· Surfactant that lowers alveolar surface tension is not present until late in fetal development and may not be present in premature babies

Aging Effects· Elasticity of lungs decreases· Vital capacity decreases· Blood oxygen levels decrease· Stimulating effects of carbon

dioxide decreases· More risks of respiratory tract

infection

Respiratory Rate Changes Throughout Life

· Newborns – 40 to 80 respirations per minute

· Infants – 30 respirations per minute

· Age 5 – 25 respirations per minute

· Adults – 12 to 18 respirations per minute

· Rate often increases somewhat with old age