The Respiratory System

The Respiratory SystemChapter 13Organs of the Respiratory SystemNosePharynxLarynxTracheaBronchiLungsalveoliOrgans of the Respiratory SystemFigure 13.1

Functions of the Respiratory SystemGas exchanges between the blood and external environment Occurs in the alveoli of the lungsPassageways to the lungs conduct, purify, humidify, and warm the incoming airThe NoseOnly externally visible part of the respiratory systemAir enters the nose through the external nostrils (nares)Interior of the nose consists of a nasal cavity divided by a nasal septumUpper Respiratory TractFigure 13.2

Anatomy of the Nasal CavityOlfactory receptors are located in the mucosa on the superior surfaceThe rest of the cavity is lined with respiratory mucosa thatMoisten airTrap incoming foreign particlesIn cold weather, cilia become sluggish and mucus tends to accumulateAnatomy of the Nasal CavityLateral walls have projections called conchaeIncrease surface areaIncrease air turbulence within the nasal cavity deflects foreign particles mucus-coated surfaces so they cant enter lungsThe nasal cavity is separated from the oral cavity by the palateAnterior hard palate (bone)Posterior soft palate (muscle)Cleft PalateBones of hard palate do not fuse properly difficulty inbreathingchewingspeaking

Cleft PalateCauses, incidence, and risk factorsgenetics, drugs, viruses, or other toxins can all cause such birth defectsmay occur along with other syndromes or birth defectsrisk factors include a family history of cleft lip or palate and other birth defect; ~ 1/ 2,500 peopleSymptoms 1of these conditions @birthsmall notch in the lipcomplete split in the lip that goes all the way to the base of the noseone or both sides of the roof of the mouthmay go the full length of the palate

Paranasal SinusesCavities within bones surrounding the nasal cavity are called sinusesSinuses are located in the following bonesFrontal boneSphenoid boneEthmoid boneMaxillary boneParanasal SinusesLighten skullAct as resonance chambers for speechProduce mucus drains nasal cavitysuctioning effect from nose blowing will drain sinusesNasolacrimal ducts drain nasal cavity alsoParanasal Sinuses

Sinuses are not fully developed until after age twelve. When people speak of sinus infections, they are most frequently referring to the maxillary and frontal sinuses.Upper Respiratory TractParanasal SinusesFigure 13.2

SinusitisWhen the sinus openings become blocked or too much mucus builds up, bacteria and other germs can grow more easily.Sinusitis can occur from one of these conditions:cilia in the sinuses - help move mucus out - do not work properlycolds and allergies: too much mucus , blockage of sinus openingsdeviated nasal septum, nasal bone spur, or nasal polyps may block the opening of the sinuses.Sinusitis can be:acute -- symptoms last up to 4 weeks; caused by bacterial infection in sinuses that results from URIsub-acute -- symptoms last 4 - 12 weekschronic -- symptoms last 3 months or longer; long-term swelling/inflammation of the sinuses; caused by bacteria/fungusSinusitis

Pharynx (Throat)Muscular passage from nasal cavity to larynx (~13 cm.)Three regions of the pharynxNasopharynxsuperior region behind nasal cavityOropharynxmiddle region behind mouthLaryngopharynxinferior region attached to larynxThe oropharynx and laryngopharynx are common passageways for air and foodStructures of the PharynxPharyngotympanic tubes open into the nasopharynxTonsils of the pharynxPharyngeal tonsil (adenoids) are located in the nasopharynxPalatine tonsils are located in the oropharynxLingual tonsils are found at the base of the tongueUpper Respiratory Tract: Pharynx

Figure 13.2TonsillitisCauses, incidence, and risk factorsstrep throat tonsils may become so overwhelmed by bacterial/viral infection that they swell and become inflamedinfection may also be present in throat and areas around it, causing inflammation of pharynx

Otitis MediaEustachian tube runs from middle ear back of throatdrains fluid that is normally made in the middle earwhen blocked, fluid can build upbacteria/viruses multiply infection (acute otitis media)Chronic ear infection may be caused by an acute ear infection that does not clear completely, or repeated ear infectionsfluid in middle ear may become very thicksometimes, tympanic membrane may stick to bones in middle ear

Larynx (Voice Box)Inferior to pharynxRoutes air and food into proper channelsPlays a role in speechMade of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (epiglottis)Structures of the LarynxThyroid cartilagelargest of the hyaline cartilagesprotrudes anteriorly (Adams apple)Epiglottisprotects superior opening of larynxroutes food to esophagus, air toward tracheawhen swallowing, epiglottis rises and forms lid over the opening of the larynxcough reflex is activated when anything other than air enters trachea; doesnt work when unconsciousStructures of the LarynxVocal folds (true vocal cords)Vibrate with expelled air to create sound (speech)Glottisopening between vocal cordsSpasmodic dysphoniaIn the past, thought to be caused by psychological problemNow - problem in brain/nervous systemvocal cord muscles spasm, causing the vocal cords to get too close or too far apart while people with the condition are using their voiceUsually occurs ages 30 51Women more likely to be affected than men

Upper Respiratory Tract: LarynxFigure 13.2

Trachea (Windpipe)4 tube - connects larynx w/bronchiReinforced w/C-shaped hyaline cartilage Lined w/ciliated mucosaBeat continuously in opposite direction of incoming airExpel mucus loaded w/dust & other debris away from lungsHyaline cartilage ringsOpen part @ back allows expansion of esophagusSolid part @front supports trachea walls patent (open) despite pressure changes associated w/breathingHeimlich maneuver

Heimlich maneuverIf repeated attempts do not free airway, emergency cut in windpipe (tracheostomy or cricothyrotomy) may be necessaryHuge amounts of mucus form due to tracheal irritation must be suctioned

Trachea (Windpipe)Figure 13.3a

Trachea (Windpipe)Figure 13.3b

SmokingInhibits ciliary action; ultimately destroys ciliaCoughing is only method of preventing mucus from accumulating in lungsSmokers should avoid cough suppressantsMain (Primary) BronchiFormed by division of the tracheaEnters the lung at the hilum (medial depression)Right bronchus is wider, shorter, and straighter than left (more common site for object to become lodged)Bronchi subdivide into smaller and smaller branches* Air entering bronchi is warm, clean dampMain BronchiFigure 13.1

Main BronchiFigure 13.4b

LungsOccupy most of the thoracic cavityHeart occupies central portion called mediastinumApex is near the clavicle (superior portion)Base rests on the diaphragm (inferior portion)Each lung is divided into lobes by fissuresLeft lungtwo lobesRight lungthree lobesLungsFigure 13.4a

LungsFigure 13.4b

Coverings of the LungsSerosa covers outer surface of lungsPulmonary (visceral) pleura covers lung surfaceParietal pleura lines walls of thoracic cavityPleural fluid fills area between layers of pleura to allow glidingThese two pleural layers resist being pulled apartLungsFigure 13.4a

PleurisySymptomschest pain that most likely occurs when coughing or taking a deep breath in or outsome feel pain in shoulderdeep breathing, coughing, chest movements makes pain worsePleurisy can cause fluid to collect inside chest cavitycyanosiscoughingshortness of breathtachypnea (rapid breathing)

PleurisySigns and testsnormally smooth pleura become roughrub together with each breathmay produce a rough, grating sound called a "friction rub" health care professional can hear this with stethoscope or by placing an ear against chest

Bronchial (Respiratory) Tree DivisionsAll but the smallest of these passageways have reinforcing cartilage in their wallsPrimary bronchiSecondary bronchiTertiary bronchiBronchiolesTerminal bronchiolesconducting zone structuresBronchial (Respiratory) Tree Divisions Figure 13.5a

Respiratory ZoneStructuresRespiratory bronchiolesAlveolar ductsAlveolar sacsAlveoli (air sacs)Site of gas exchange = alveoli onlyrespiratory zoneBronchial (Respiratory) Tree Divisions Figure 13.5a

Respiratory Membrane (Air-Blood Barrier)Respiratory membrane = alveolar walls + capillary walls + their fused basement membranes + occasional elastic membranesRespiratory Membrane (Air-Blood Barrier)Thin squamous epithelial layer lines alveolar wallsAlveolar pores connect neighboring air sacsProvide alternative air pathway if theres mucus blockage, etcPulmonary capillaries cover external surfaces of alveoliOn one side of the membrane is air and on the other side is blood flowing past

Respiratory Membrane (Air-Blood Barrier)Figure 13.6 (1 of 2)

Respiratory Membrane (Air-Blood Barrier)Figure 13.6 (2 of 2)

Gas Exchange

Gas ExchangeGas crosses the respiratory membrane by diffusionOxygen enters the bloodCarbon dioxide enters the alveoliAlveolar macrophages (dust cells) add protection by picking up bacteria, carbon particles, and other debrisSurfactant (a lipid molecule) coats gas-exposed alveolar surfaces (more later)Four Events of RespirationPulmonary ventilationmoving air in and out of the lungs (commonly called breathing)External respirationgas exchange between pulmonary blood and alveoliOxygen is loaded into the bloodCarbon dioxide is unloaded from the bloodExternal RespirationFigure 13.6 (2 of 2)

Four Events of RespirationRespiratory gas transporttransport of oxygen and carbon dioxide via the bloodstreamInternal respirationgas exchange between blood and tissue cells in systemic capillaries

Mechanics of Breathing (Pulmonary Ventilation)Completely mechanical process that depends on volume changes in the thoracic cavityVolume changes lead to pressure changes, which lead to the flow of gases to equalize pressureMechanics of Breathing (Pulmonary Ventilation)Two phasesInspiration = inhalationflow of air into lungsExpiration = exhalationair leaving lungsInspirationDiaphragm and external intercostal muscles contract The size of the thoracic cavity increasesExternal air is pulled into the lungs due to Increase in intrapulmonary volumeDecrease in gas pressureInspirationFigure 13.7a

InspirationFigure 13.8

ExpirationLargely a passive process which depends on natural lung elasticityAs muscles relax, air is pushed out of the lungs due to Decrease in intrapulmonary volumeIncrease in gas pressureForced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage

ExpirationFigure 13.7b

ExpirationFigure 13.8

Pressure Differences in the Thoracic CavityNormal pressure within the pleural space is always negative (intrapleural pressure)Differences in lung and pleural space pressures keep lungs from collapsingNonrespiratory Air (Gas) MovementsCan be caused by reflexes or voluntary actionsExamples:Cough and sneezeclears lungs of debrisCryingemotionally induced mechanism Laughingsimilar to crying Hiccupsudden inspirationsYawnvery deep inspirationNonrespiratory Air (Gas) MovementsTable 13.1

Respiratory Volumes and CapacitiesNormal breathing moves about 500 mL of air with each breath This respiratory volume is tidal volume (TV)Many factors that affect respiratory capacityA persons sizeSexAgePhysical conditionRespiratory Volumes and CapacitiesInspiratory reserve volume (IRV)Amount of air that can be taken in forcibly over the tidal volumeUsually between 2100 and 3200 mLExpiratory reserve volume (ERV)Amount of air that can be forcibly exhaledApproximately 1200 mLRespiratory Volumes and CapacitiesResidual volumeAir remaining in lung after expirationAbout 1200 mlRespiratory Volumes and CapacitiesVital capacityThe total amount of exchangeable airVital capacity = TV + IRV + ERVDead space volumeAir that remains in conducting zone and never reaches alveoliAbout 150 mLRespiratory Volumes and CapacitiesFunctional volumeAir that actually reaches the respiratory zoneUsually about 350 mLRespiratory capacities are measured with a spirometerRespiratory VolumesFigure 13.9