Chapter 13 The Respiratory System

Biology 110

Tri-County Technical College

Pendleton, SC

System Essentials

Supply cells with oxygen

Pick up carbon dioxide from the body

Eliminate carbon dioxide from the body

Organs of respiratory system include: Nose, pharynx, larynx, trachea, bronchi and its branches, and the alveoli of the lungs

Respiratory System Visual

A nose for this…or that

Only externally visible part of systemAir enters nose through external nares (nostrils)Interior consists of nasal cavity divided by midline nasal septumOlfactory receptors in mucosa in superior part of cavity just below ethmoid bone

Nose, cont.

Rest of mucosa lining called respiratory mucosa rests on network of thin-walled veins that warms air flowing pastMucosa moistens inhaled air & traps

incoming debris

Ciliated cells move contaminated mucus posteriorly toward throat (pharynx) swallowed & digested by stomach acid

Nose, cont.Three mucosa-covered lobes called nasal conchae increase surface area exposed to air Also increase turbulence in nasal cavity

Nasal cavity separated from oral cavity by partition called the palate

Anterior palate supported by hard bone = hard palate

Posterior palate is unsupported by bone = soft palate

Paranasal SinusesNasal cavity surrounded by paranasal sinuses located in frontal, sphenoid, ethmoid, and maxillary bones Lighten the skull Resonance chambers for speech Produce mucus that drains into nasal cavity

Nasal mucosa continuous throughout RT Nasal infections can spread throughout mucosa

Sinusitis difficult to treat & can cause marked change in voice quality

Paranasal Sinuses Visual

PharynxMuscular passageway for food and air commonly called throatNaso-; Oro-; and laryngopharynxAir enters superior portion (naso) from nasal cavity anteriorlyAir descends through oropharynx and laryngopharynx to enter larynx belowFood from mouth travels with air through oro- and laryngopharynx but directed posteriorly to esophagus instead of entering larynx

Pharynx, cont.

Auditory tubes that drain middle ear open into nasopharynxotitis media (ear infection) may follow sore throat/pharyngeal infectionsClusters of lymphatic tissue called tonsils found in pharynxPharyngeal: (adenoids) located high in nasoPalatine: oropharynx at end of soft palateLingual: at base of tongue

Respiratory Visual

Larynx and Associated Structures

Larynx (voicebox) routes air/food into proper channels and plays role in speech

Formed by 8 rigid hyaline cartilages and elastic cartilage called epiglottis

Largest of hyaline cartilages is THYROID cartilage (Adam’s apple)

Epiglottis protects superior opening of larynx

Larynx, cont.

Not swallowing, epiglottis does not restrict passage of air into respiratory passages

Swallowing, larynx pulls forward and epiglottis tips forming lid over opening of larynx

Routes food/drink into esophagus posteriorly

Cough reflexunconscious person

Larynx, cont.

Part of mucous membrane of larynx forms pair of folds called vocal folds (true vocal cords) which vibrate with expelled airAllows speechSlitlike passages between folds called glottisLarynx leads to trachea (windpipe)

Trachea

Extends from larynx to level of 5th thoracic vertebra (~ midchest)

Lined with ciliated mucosa

Walls reinforced with C-shaped rings of hyaline cartilage

Open parts of rings abut esophagus and allow it to expand anteriorly when one swallows

Trachea, cont.

Solid portions support walls and keep it patent (or open) in spite of pressure changes during breathing

Tracheal obstructions are LIFE-threatening

Heimlich maneuver can unclog trachea It works or my side would be gone…for good

Sometimes emergency trachesostomy is required

Bronchi DivisionsTrachea divides into right and left primary bronchi

Each primary bronchi plunges into medial depression (the hilus-depressed area where vessels enter/leave an organ) of lung

Right pulmonary bronchus is wider, shorter, and straighter than left

Smaller subdivisons of primary bronchi within lung deliver air to alveoli

Bronchi Visual

Lungs and more…

Occupy most of thoracic cavity except for mediastinum (houses heart, great blood vessels, bronchi, esophagus, thymus, and trachea)

Narrow superior portion is APEX; located just deep to clavicle

Broad area resting on diaphragm is BASE

Each lung divided into LOBES by fissures

Left lung = 2 lobes; right lung = 3 lobes

Lungs, cont.Surface covered by visceral (pulmonary) pleura and walls of thoracic cavity lined by parietal pleura

Membranes produce pleural fluid which allows lungs to glide easily over thorax wall during breathing Also causes 2 pleural layers to cling together

Glide easily but resist being pulling apart Absolutely essential for normal breathing

Lungs, cont.

PLEURISY (inflammation of pleura) can be caused by decreased secretion of pleural fluid Surfaces become dry and roughfriction and

stabbing pain with each breath Another kind of pleurisy results in excess fluid and

pressure on the lungs

Primary bronchisecondary & tertiary bronchibronchiolesterminal bronchioles (conducing zone structures)respiratory zone structures

Lungs, cont.RZ structures include respiratory bronchiolesalveolar ductsalveolar sacsalveoli and is ONLY site of gas exchange

Exchange of GasesAlveoli composed largely of single layer of layer of squamous epithelial cells

External surface of alveoli covered with cobweb of pulmonary capillaries

Alveolar and capillary walls construct respiratory membrane (air-blood barrier)

Blood flowing on one side; air on the other

Gases diffuse across air-blood barrier by simple diffusion

Gas Exchange, cont.Surface area of lungs = size of racquetball court (70-80 sq. meters)

Macrophages (dust cells) wander in and out of alveoli to pick up bacteria/debris

Cuboidal epithelial cells scattered throughout alveolar walls secrete surfactant (lipid that coats gas-exchange alveolar surfaces and is important in lung function

Gas Exchange Visual

Events of Respiration

Pulmonary ventilation (breathing)External respiration (gas exchange between pulmonary blood and alveoli)Respiratory gas transport (gas must be transported to/from lungs and tissue cells via bloodstreamInternal respiration (gas exchange between blood and tissue cells at systemic capillaries

Mechanics of Breathing

Pulmonary ventilation depends on volume changes in thoracic cavityVolume changes lead to pressure changes flow of gases to equalize the pressureGas always fills its container Volume of container related to pressure of gas

Inspiration = gas flowing into lungsExpiration = gas flowing out of lungs

Mechanics of Inspiration

Diaphragm & external intercostal muscles contractSize of thorax increaseslungs adhere tightly to thorax wallsstretched to new, larger size of thoraxLung volume increases producing partial vacuum (pressure less than atmospheric pressure) Air rushes in to fill space—inspiration is always an active process

Mechanics Visual

Mechanics of Expiration

Usually passive process that essentially reverse of inspirationActive expiration (forced)—internal intercostals activated and contracted to depress rib cage and abdominal muscles contract to help FORCE air from lungsAsthma (spasms of bronchioles) or chronic

bronchitis/pneumonia can narrow respiratory passageways

Mechanics, cont.

Actelectasis (lung collapse) renders lung useless for ventilationair enters pleural space through chest

wound or rupture of visceral pleural (allows air to enter pleural space from respiratory tract)

Pneumothorax is term given presence of air in intrapleural space (disrupts fluid bond between pleura)

Mechanics, cont.

RESPIRATORY SOUNDS:Bronchial sounds produced by air rushing through large respiratory passageways such as trachea and bronchiVesicular breathing sounds occur as air fills alveoliSoft and resemble muffled breeze

Modified Respiratory Movements

Situations other than breathing move air in and out of respiratory system

Most “nonrespiratory air movements” are result of reflex activity

Cough, sneeze, crying, laughing, hiccups, yawn, sighing….

External Respiration

Actual exchange of gases between alveoli and blood (pulmonary gas exchange)Oxygen leaves alveolus and enters blood capillaryCarbon dioxide leaves blood capillary and enters alveolusOccurs by simple diffusion (movement occurs toward area of lower [ ] of diffusing substance)

Gas TransportVery small amount of O2 dissolved in bloodMost transported as oxyhemoglobin Hb + O2 HbO2

Most CO2 transported as bicarbonate ion 20-30% carried inside RBCs bound to hemoglobin (at different site than oxygen)Very small amount transported in plasma

CO2 + H2OH2CO3H+ + HCO3-

For carbon dioxide to diffuse out of blood into alveoli, reaction must be reversed

Gas Exchange Visual

Internal Respiration

Gas exchange process that occurs between systemic capillaries and tissue cellsCarbon dioxide leaves tissues and enters bloodOxygen leaves blood and enters tissuesAll gas exchanges made according to the laws of diffusion

Respiration ControlsActivity of respiratory muscles, diaphragm, and external intercostals regulated by brain impulses carried by phrenic and intercostal nervesRespiratory rhythm and depth control center located in medulla and ponsMedulla contains self-exciting inspiratory and expiratory centers Sets the rhythm of breathing

Controls, cont.Pons contains apneustic and pneumotaxic centers Smooth out basic rhythms of inspiration and expiration

Work to maintain ~ 12-15 respirations/min.EUPNEA= normal breathing rateInspiratory center active = inspireExpiratory center active = expireApneustic center in pons=keeps inspiratory center goingPneumontaxic center in pons=limits length of inspiration and promotes expiration

Rate/Depth Breathing FactorsPHYSICAL such as walking, coughing, and exercise >body temp can > rate of breathing

CONSCIOUS such as singing, swallowing, or holding breath while swimming voluntary control limited then involuntary takes

over

EMOTIONAL such as fright, surprise, or “other”

Factors, cont.CHEMICAL most important rate and depth factors CO2 and O2 levels in blood

Increased levels of CO2 and decreased blood pH MOST important stimuli leading to increase in rate/depth of breathing

Changes in CO2 [ ] in blood act directly on medulla centers

Changes in O2 [ ] in blood detected by chemoreceptors in AORTIC ARCH and CAROTID body in carotid artery

Factors, cont.Chemoreceptors send impulses to medulla when blood O2 levels are dropping

<s in O2 levels ONLY important when they are dangerously LOW Increases rate/depth of breathing

Hypoventilation=accumulation of CO2 in blood and >ed blood acidity

Hyperventilation=CO2 removed from blood and <ed blood acidityAcidosis or alkalosis can result

Respiratory Related TermsApena is cessation of breathing caused by hyperventilationDyspnea is labored or difficult breathingEmphysema=alveoli enlarge as walls of adjacent chambers break through; chronic inflammation promotes fibrosis of lungs Requires lots of energy to exhale

Chronic bronchitis=mucosa of lower respiratory passages become severely inflamed and produces extra mucus

Terms, cont.

Chronic bronchitis impairs ventilation and gas exchange and increases risk of lung infections

Pneumonitis=inflammation of alveoli of the lungs resulting in them becoming clogged with mucus and/or fluids

Volumes and CapacitiesTidal volume (TV) is amount of air moved in and out of lungs with each breath (500 ml)Inspiratory Reserve Volume (IRV) is amount of air that can be forcibly taken in over tidal volume (2100-3200 ml)Expiratory Reserve Volume (ERV) is amount of air that can be forcibly exhaled after tidal expiration (1200 ml)

Volumes, cont.

Residual Volume (RV) is amount of air left in lungs that cannot be voluntarily expelled

Vital Capacity (VC) is sum of TV + IRV + ERV Total amount of exchangeable air about 4800 ml in healthy young males

Dead space volume is air that remains in conducting zone

Volume Visual