The Respiratory System

Organs of the Respiratory SystemNosePharynxLarynxTracheaBronchiLungsalveoli

Organs 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 purify, humidify, and warm the incoming air

The 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 septum

Upper 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 particles

Anatomy of the Nasal CavityLateral walls have projections called conchaeIncrease surface areaIncrease air turbulence within the nasal cavityThe nasal cavity is separated from the oral cavity by the palateAnterior hard palate (bone)Posterior soft palate (muscle)

Paranasal SinusesCavities within bones surrounding the nasal cavity are called sinusesSinuses are located in the following bonesFrontal boneSphenoid boneEthmoid boneMaxillary bone

Upper Respiratory TractParanasal SinusesFigure 13.2

Paranasal SinusesFunction of the sinusesLighten the skullAct as resonance chambers for speechProduce mucus that drains into the nasal cavity

Pharynx (Throat)Muscular passage from nasal cavity to larynxThree regions of the pharynxNasopharynxsuperior region behind nasal cavityOropharynxmiddle region behind mouthLaryngopharynxinferior region attached to larynxThe oropharynx and laryngopharynx are common passageways for air and food

Structures 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 tongue

Upper Respiratory Tract: PharynxFigure 13.2

Larynx (Voice Box)Routes 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 the superior opening of the larynxRoutes food to the esophagus and air toward the tracheaWhen swallowing, the epiglottis rises and forms a lid over the opening of the larynx

Structures of the LarynxVocal folds (true vocal cords)Vibrate with expelled air to create sound (speech)Glottisopening between vocal cords

Upper Respiratory Tract: LarynxFigure 13.2

Trachea (Windpipe)Four-inch-long tube that connects larynx with bronchiWalls are reinforced with C-shaped hyaline cartilage Lined with ciliated mucosaBeat continuously in the opposite direction of incoming airExpel mucus loaded with dust and other debris away from lungs

Trachea (Windpipe)Figure 13.3a

Trachea (Windpipe)Figure 13.3b

Main (Primary) BronchiFormed by division of the tracheaEnters the lung at the hilum (medial depression)Right bronchus is wider, shorter, and straighter than leftBronchi subdivide into smaller and smaller branches

Main 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 lobes

LungsFigure 13.4a

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

Bronchial (Respiratory) Tree DivisionsAll but the smallest of these passageways have reinforcing cartilage in their wallsPrimary bronchiSecondary bronchiTertiary bronchiBronchiolesTerminal bronchioles

Bronchial (Respiratory) Tree Divisions Figure 13.5a

Respiratory ZoneStructuresRespiratory bronchiolesAlveolar ductsAlveolar sacsAlveoli (air sacs)Site of gas exchange = alveoli only

Bronchial (Respiratory) Tree Divisions Figure 13.5a

Bronchial (Respiratory) Tree Divisions Figure 13.5b

Respiratory Membrane (Air-Blood Barrier)Thin squamous epithelial layer lines alveolar wallsAlveolar pores connect neighboring air sacsPulmonary 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 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

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 blood

External 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 pressure

Mechanics of Breathing (Pulmonary Ventilation)Two phasesInspiration = inhalationflow of air into lungsExpiration = exhalationair leaving lungs

InspirationDiaphragm 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 pressure

InspirationFigure 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 collapsing

Nonrespiratory Air (Gas) MovementsCan be caused by reflexes or voluntary actionsExamples:Cough and sneezeclears lungs of debrisCryingemotionally induced mechanism Laughingsimilar to crying Hiccupsudden inspirationsYawnvery deep inspiration

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 condition

Respiratory 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 mL

Respiratory Volumes and CapacitiesResidual volumeAir remaining in lung after expirationAbout 1200 ml

Respiratory 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 mL

Respiratory Volumes and CapacitiesFunctional volumeAir that actually reaches the respiratory zoneUsually about 350 mLRespiratory capacities are measured with a spirometer

Respiratory VolumesFigure 13.9