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Chapter 23

Respiratory System

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Respiration

• Ventilation: Movement of air into & out of lungs

• External respiration: Gas exchange b/n air in lungs & blood– Transport of O2 and CO2 in the blood

• Internal respiration: Gas exchange b/n the blood & tissues

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Respiratory System Functions

• Gas exchange: O2 enters blood & CO2 leaves

• Regulation of blood pH: Altered by changing blood CO2 levels

• Voice production: Movement of air past vocal folds makes sound & speech

• Olfaction: Smell occurs when airborne molecules drawn into nasal cavity

• Protection: Against microorganisms by preventing entry & removing them

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Respiratory System Divisions

• Upper tract– Nose, pharynx &

associated structures

• Lower tract– Larynx, trachea,

bronchi, lungs

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Nose and Pharynx

• Nose– External nose– Nasal cavity

• Functions– Passageway for air– Cilia cleans the air– Mucous humidifies

(moistens air inhaled)

– Capillaries warm air– Smell– Along with paranasal

sinuses are resonating chambers for speech

• Pharynx– Common opening for

digestive & respiratory systems

– Three regions• Nasopharynx• Oropharynx• Laryngopharynx

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Larynx

• Functions– Maintain an open passageway for air movement– Epiglottis & vestibular folds prevent swallowed material

from moving into larynx (can move to cover trachea)

– Vocal folds are primary source of sound production

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Structure of Larynx

– AKA voice box

– Thyroid cartilage: AKA Adam’s apple • Protects vocal cords • Moves when you

swallow

– Epiglottis: closes off larynx so food & liquid travel down the esophagus

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Voice Production• False vocal cords:

assist w/ hold breath• True vocal cords:

– Space between them called glottis

– Vibration produces sound

– In combination with tongue, mouth, & nose to produce words

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Concept Check1. Name the functions of the respiratory system.

-Gas exchange; regulation of blood pH; olfaction; protection

2. How is the respiratory system divided? Name the parts of each.

-Upper (Nose, Pharynx, Assoc. Structures); -Lower (Larynx, Trachea, Bronchi, Lungs)

3. Name the accessory structures of the nose, and describe their function.

-Cilia (cleans air); Mucus (moistens air), Capillaries (warms air)

4. The larynx is also known as the…-Voice Box

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Trachea

• Windpipe

• Divides to form– Primary bronchi– Carina: Cough

reflex

Insert Fig 23.5 all but b

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Organs of Respiration• Trachea:

– AKA windpipe

– Smooth muscle supported by C-shaped rings of cartilage

• food can travel down esophagus easier

– Passageway for air from larynx to bronchi

– Lined w/ cilia & mucous

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Tracheobronchial Tree

• Conducting zone– Trachea to terminal bronchioles which is

ciliated for removal of debris– Passageway for air movement– Cartilage holds tube system open & smooth

muscle controls tube diameter

• Respiratory zone– Respiratory bronchioles to alveoli– Site for gas exchange

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Organs of Respiration

• Bronchi:– Left & right

primary bronchi branch off trachea

– Lined w/ cilia

– Supported by cartilage

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Bronchial Tree

Primary bronchi

Secondary bronchi

Tertiary bronchi

bronchioles

Terminal bronchioles

Respiratory bronchioles

Alveolar ducts

Alveolar sacs

alveoli

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Bronchioles and Alveoli

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Alveolus and Respiratory Membrane

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Lungs

• Two lungs: Principal organs of respiration– Right lung: Three lobes– Left lung: Two lobes

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Organs of Respiration

• Alveoli:– Extremely thin-

walled sacs covered w/ capillaries

– CO2 & O2 move by diffusion across the respiratory membrane

– About 300 million alveoli in two lungs

– Size of a tennis court

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Organs of Respiration

• Alveoli:– Surfactant lines the

alveoli to aid diffusion & decrease surface tension

– To prevent the alveoli from collapsing & sticking shut

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Pleura

• Pleural fluid produced by pleural membranes– Acts as lubricant– Helps hold parietal & visceral pleural membranes

together

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Concept Check

1. The trachea is also known as…-Windpipe

1. How is the trachea structured & why?

-C-Shaped rings of cartilage (allows passage of food to move easily)

2. Describe the bronchial tree.

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Ventilation

• Movement of air into and out of lungs

• Air moves from area of higher pressure to area of lower pressure (AKA Diffusion)

• Pressure is inversely related to volume

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Inspiration• Breathing in

• When pressure in the lungs is less than the air pressure in the atmosphere

• Diaphragm— will contract and lower, increasing the size of the thoracic cage

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Inspiration

• Increased volume will decrease the pressure & the lungs will expand

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Expiration• Breathing out

• When the pressure inside the lungs is greater than the pressure in the atmosphere

• Diaphragm— relaxes and rises; decreases the size of the thoracic cage

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Expiration

• Decreased volume will increase pressure & lungs will decrease and push air out

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Internal Respiration

• Exchange of O2 and CO2 between tissue capillaries and tissue cells

• CO2 moves from high concentration in cells to low concentration in blood

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External Respiration

• Conversion of deoxygenated blood to oxygenated blood– Aided by thin

membranes– Large surface area– Narrow capillaries

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Concept Check

1. What is the diffusion?

2. What is the difference between inspiration and expiration?

3. What happens to the diaphragm? Be specific.

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Changing Alveolar Volume

• Lung recoil– Causes alveoli to collapse resulting from

• Elastic recoil and surface tension– Surfactant: Reduces tendency of lungs to

collapse

• Pleural pressure– Negative pressure can cause alveoli to

expand– Pneumothorax is an opening between

pleural cavity & air that causes a loss of pleural pressure

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Compliance• Measure of the ease with which lungs

& thorax expand– The greater the compliance, the easier it

is for a change in pressure to cause expansion

– A lower-than-normal compliance means the lungs and thorax are harder to expand• Conditions that decrease compliance

– Pulmonary fibrosis– Pulmonary edema– Respiratory distress syndrome

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Pulmonary Volumes• Tidal volume

– Volume of air inspired or expired during a normal inspiration or expiration

• Inspiratory reserve volume– Amount of air inspired forcefully after inspiration of

normal tidal volume

• Expiratory reserve volume– Amount of air forcefully expired after expiration of

normal tidal volume

• Residual volume– Volume of air remaining in respiratory passages and

lungs after the most forceful expiration

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Pulmonary Capacities

• Inspiratory capacity– Tidal volume plus inspiratory reserve volume

• Functional residual capacity– Expiratory reserve volume plus the residual volume

• Vital capacity– Sum of inspiratory reserve volume, tidal volume,

and expiratory reserve volume

• Total lung capacity– Sum of inspiratory and expiratory reserve volumes

plus the tidal volume and residual volume

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Spirometer and Lung Volumes/Capacities

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Minute and Alveolar Ventilation

• Minute ventilation: Total amount of air moved into & out of respiratory system per minute

• Respiratory rate or frequency: Number of breaths taken per minute

• Anatomic dead space: Part of respiratory system where gas exchange does not take place

• Alveolar ventilation: How much air per minute enters the parts of the respiratory system in which gas exchange takes place

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Physical Principles of Gas Exchange

• Partial pressure– The pressure exerted by each type of

gas in a mixture

• Diffusion of gases through liquids– Concentration of a gas in a liquid is

determined by its partial pressure and its solubility coefficient

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Physical Principles of Gas Exchange

• Diffusion of gases through the respiratory membrane– Depends on membrane’s thickness, the diffusion

coefficient of gas, surface areas of membrane, partial pressure of gases in alveoli and blood

• Relationship between ventilation and pulmonary capillary flow– Increased ventilation or increased pulmonary capillary

blood flow increases gas exchange– Physiologic shunt is deoxygenated blood returning from

lungs

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Oxygen & Carbon Dioxide Diffusion Gradients

• Oxygen– Moves from alveoli

into blood. Blood is almost completely saturated with oxygen when it leaves the capillary

– C02 in blood decreases because of mixing with deoxygenated blood

– Oxygen moves from tissue capillaries into the tissues

• Carbon dioxide– Moves from

tissues into tissue capillaries

– Moves from pulmonary capillaries into the alveoli

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Hemoglobin and Oxygen Transport

• Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%)

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Transport of Carbon Dioxide

• Carbon dioxide is transported as bicarbonate ions (70%) in combination with blood proteins (23%) and in solution with plasma (7%)

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Herring-Breuer Reflex

• Limits the degree of inspiration and prevents overinflation of the lungs– Infants

• Reflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungs

– Adults• Reflex important only when tidal volume large as

in exercise

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Ventilation in Exercise• Ventilation increases abruptly

– At onset of exercise– Movement of limbs has strong influence– Learned component– Decreases slightly

• Ventilation increases gradually– After immediate increase, gradual increase

occurs (4-6 minutes)– Anaerobic threshold is highest level of exercise

without causing significant change in blood pH• If exceeded, lactic acid produced by skeletal

muscles

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Disorders• Asthma— spasms of smooth muscle

in the bronchioles

• Lung cancer– Constant irritation produces excess

mucous and puts unnecessary stress on the bronchi

– Alveoli destroyed by WBC’s acting on the irritation

– Structural cells disappear and cancer cells take over

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Disorders

• Emphysema— alveolar walls lose their elasticity– Some alveoli merge and reduce volume– Have to work voluntarily to exhale

• Bronchitis— inflammation of the bronchi– Creates site for infection and increases

mucous

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Disorders

• Pneumonia— infection or inflammation of the alveoli

• Tuberculosis (TB)— bacterial infection that destroys lung tissue and is replaced by non-elastic connective tissue

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Disorders

• Respiratory Distress Syndrome (RDS)– Lack of surfactant makes breathing

difficult – Alveoli are sticking together– Occurs in infants

• Pulmonary Embolism– blood clot obstructs circulation to lung

tissue & tissue dies

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Disorders

• Respiratory Failure– Not enough O2 to maintain metabolism

– Cannot eliminate enough CO2

– Caused by:• Drugs• Stroke• CO poisoning• shock

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Disorders

• Colds and Flu— viral infections

• Sudden Infant Death Syndrome (SIDS)– Crib death– Occurs between 1 week and 12 months– Cause is unknown– Baby stops breathing

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Disorders

• Laryngitis— vocal cords

• Pharyngitis— sore throat

• Rhinitis— lining of the nose

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Effects of Aging

• Vital capacity and maximum minute ventilation decrease

• Residual volume and dead space increase

• Ability to remove mucus from respiratory passageways decreases

• Gas exchange across respiratory membrane is reduced