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The Respiratory System. Chapter 23. Introduction. The trillions of cells making up the body require a continuous supply of oxygen to carry out vita functions We can survive only a few minutes without oxygen

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  • The trillions of cells making up the body require a continuous supply of oxygen to carry out vita functions
  • We can survive only a few minutes without oxygen
  • As cells use oxygen, they give off carbon dioxide a waste product of cellular respiration
  • The major function of the respiratory system is to supply the body with oxygen and dispose of carbon dioxide
  • To achieve this function four distinct processes, collectively called respiration occur
    • Pulmonary ventilation
    • External respiration
    • Transport of respiratory gases
    • Internal respiration
  • Pulmonary ventilation
    • Air must be moved in and out of the lungs so that the gases in the air sacs (alveoli) of the lungs are continually changed and refreshed
    • This air movement is commonly called ventilation or breathing
  • External respiration
    • Gas exchange (oxygen loading and carbon dioxide unloading) between the blood and the air-filled chambers of the lungs must occur
  • Transport of respiratory gases
    • Oxygen and carbon dioxide must be transported between the lungs and tissue cells of the body
    • This is accomplished by the cardiovascular system, which uses blood as the transporting fluid
  • Internal respiration
    • At systemic capillaries, gas exchanges (oxygen unloading and carbon dioxide loading) must be made between the blood and tissue cells
respiratory system
Respiratory System
  • The organs of the respiratory system include the nasal cavity, pharynx, larynx, trachea, bronchi, lungs
respiratory system9
Respiratory System
  • Functionally, the respiratory system consists of the respiratory and the conducting zones
    • The respiratory zone, the actual site of gas exchange, is composed of the respiratory bronchioles, alveolar ducts, and alveoli
    • The conducting zone includes all other respiratory passageways, which provide fairly rigid conduits for air to reach the sites of gas exchange
    • Organs of the conducting zone clean, warm and humidify the incoming air
the nose
The Nose
  • The nose is the only visible part of the respiratory system
  • The external framework of the nose
the nose11
The functions of the nose include

Providing an airway for respiration

Moistening and warming entering air

Filtering inspired air and cleansing it of foreign matter

Serving as a resonating chamber for speech

Housing the olfactory receptors

The Nose
the nose12
The Nose
  • The structures of the nose are divided into the
    • External nose
    • Nasal cavity
  • Surface features
    • Root (between eyes)
    • Bridge
    • Dorsum nasi
    • Apex
    • Philtrum
    • External nares
    • Alae
the nose13
The Nose
  • The nasal cavity lies in and posterior to the external nose
  • During breathing air enters the external cavity by passing through the external nares or nostrils
  • The nasal cavity is divided by a midline nasal septum
  • The nasal cavity is continuous posteriorly with the nasal portion of the pharynx through the internal nares
the nose14
The Nose
  • The roof of the nasal cavity is formed by the ethmoid and sphenoid bones of the skull
  • The floor is formed by the palate which separates it from the oral cavity below
  • Anteriorly, where the palate is supported by the maxillary processes and the palatine bones is considered the hard palate
  • The unsupported posterior portion is the muscular soft palate
the nose15
The Nose
  • The vestibule is lined with skin containing sebaceous and sweat glands and numerous hair follicles
  • The hair or vibrissae filter coarse particles from inspired air
the nose16
The Nose
  • The nasal cavity is lined with two types of mucous membrane
  • The olfactory mucosa, lining the slitlike superior region of the nasal cavity, contain the receptors for the sense of smell
  • The balance of the nasal cavity is lined with respiratory mucosa which is made up of pseudostratified columnar epithelium, containing scattered goblet cells, that rests on a lamina propria richly supplied with mucous and serous glands
the nose17
The Nose
  • Each day the mucous glands secrete about a quart of sticky mucous containing lysozyme, an antibacterial enzyme
  • The mucous traps inspired dust, bacteria and other debris, while lysozyme attacks and destroys bacteria chemically
  • The epithelial cells of the respiratory mucosa also secrete defensins, natural antibotics that help to get rid of invading microbes
the nose18
The Nose
  • The ciliated cells of the respiratory mucosa create a gentle current that moves the sheet of contaminated mucus posteriorly toward the throat where it is swallowed and digested by stomach juices
  • These ciliated cells become sluggish in cold weather allowing mucus to accumulate in the nasal cavity where it “runs” on a cold day
the nose19
The Nose
  • A rich plexus of thin walled veins underlies the nasal epithelium and warms the incoming air as it flows across the mucosal surface
  • Blood flow increases when the weather turns cold
  • Because of its superficial location and the extent of vessels, nosebleeds are common and often profuse
the nose20
The Nose
  • Protruding medially from each lateral wall of the nasal cavity are three mucosa-covered projections, the superior, middle and inferior conchae
  • The conchae serve to increase nasal turbulence in the nasal cavity
  • Mucus/sneeze
the paranasal sinuses
The Paranasal Sinuses
  • The nasal cavity is surround by sinuses located in the frontal, sphenoid, ethmoid and maxillary bones
  • They function to
    • Produce mucus
    • Lighten the skull
    • Warm the air
    • Voice resonance
the pharynx
The Pharynx
  • The funnel shaped pharynx (throat) connects the nasal cavity and mouth to the larynx and esophagus inferiorly
  • It serves as a common pathway for food and air
  • The pharynx extends for about 5 inches from the base of the skull to the level of the sixth cervical vertebrae
  • Its three regions are nasopharynx, oropharynx and laryngopharynx
the nasopharynx
The Nasopharynx
  • The nasopharynx lies above the point of food entry, it serves only as an air passageway
  • During swallowing the uvula reflects posteriorly to close off the nasopharynx and prevent food from entering the nasal cavity
the nasopharynx24
The Nasopharynx
  • The nasopharynx is continuous with the nasal cavity through the internal nares
  • It ciliated pseudo- stratified epithelium produces mucus
  • Mucosa high on the posterior wall contains masses of lymphatic tissue, the pharyngeal tonsils or adenoids
the oropharynx
The Oropharynx
  • The oropharynx lies posterior to the oral cavity and is continuous with it through an archway called the fauces
  • Both swallowed food and air pass through
  • Lined with stratified squamous epithelium for protection from food abrasion and chemical trauma
the oropharynx26
The Oropharynx
  • Three tonsils lie embedded in the oropharyngeal mucosa
    • Paired palatine tonsils
    • Lingual tonsil
the laryngopharynx
The Laryngopharynx
  • The laryngopharynx serves as a common pathway for food and air and is lined with stratified squamous epithelium
  • It lies directly posterior to the upright epiglottis and extends to the larynx where the digestive and respiratory pathways diverge
the laryngopharynx28
The Laryngopharynx
  • The esophagus conducts food to the stomach while air enters the larynx anteriorly
  • During swallowing food has the “right of way” and air passage temporarily stops
the larynx
The Larynx
  • The larynx attaches to the hyoid bone superiorly and opens into the laryngopharynx
  • Inferiorly is is continuous with the trachea
the larynx30
The Larynx
  • The larynx has three important functions
    • It provides an airway for respiration
    • Act as a switching mechanism to route air and food into the proper channels
    • Vocal cords housed in larynx are used in voice production
the larynx31
The Larynx
  • The framework of the larynx is an arrangement of nine cartilages connected by membranes and ligaments
  • Except for the epiglottis, all laryngeal cartilages are made of hyaline
the larynx32
The Larynx
  • The large, shield shaped thyroid cartilage is formed by the fusion of two cartilage plates
  • The laryngeal prominence marks the midline fusion point
  • The cricoid cartilage is anchored to the trachea inferiorly
the larynx33
The Larynx
  • Three pairs of small cartilages, the arytenoid, cuneiform and corniculate form part of the lateral and posterior walls of the larynx
  • The arytenoid anchors the vocal cords
the larynx34
The Larynx
  • The ninth cartilage the flexible, spoon shaped epiglottis is composed of elastic cartilage
  • It is almost entirely covered by mucosa
  • The epiglottis extends from the posterior aspect of the tongue to its anchoring point on the thyroid cartilage
the larynx35
The Larynx
  • When only air is flowing into the larynx, the inlet to the larynx is open wide and the free edge of the epiglottis projects upward
  • During swallowing the larynx is pulled superiorly and the epiglottis tips to cover the laryngeal inlet
the vocal folds
The Vocal Folds
  • The vocal ligaments attach the arytenoid and thyroid cartilages
  • These ligaments are composed of elastic fibers
  • The vocal cords vibrate, producing sound as air rushes up from lungs
the vocal folds37
The Vocal Folds
  • The opening through which air passes is the glottis
  • Superior to the vocal cords are the vestibular cords which play no part in voice production
vocal folds
Vocal Folds
  • Stratified squamous epithelium lines the superior portion of the larynx, an area subject to food contact
  • Below the vocal folds the epithelium is pseudostratified ciliated columnar epithelium
  • Cilia move the mucus away from our lungs
voice production
Voice Production
  • Speech involves the intermittent release of expired air and opening and closing of the glottis
  • The length of the true vocal cords and the size of the glottis are altered by the action of the intrinsic laryngeal muscles most of which move the arytenoid cartilages
  • As the length and tension of the vocal folds change, the pitch of the sound is altered
voice production40
Voice Production
  • The glottis is wide when we produce deep tones and narrows to a slit for high pitched sounds
  • Length and thickness of the vocal folds changes for males during puberty
  • Loudness of the voice depends on the force with which the airstream rushes across the vocal cords
  • The greater the force, the stronger the vibration and the louder the sound
sphincter functions of larynx
Sphincter Functions of Larynx
  • The vestibular folds can perform a sphincter function under certain conditions
  • In abdominal straining associated with defecation and urination, inhaled air is held temporarily in the lower respiratory tract by closing the epiglottis
  • The abdominal muscle then contract and the interabdominal pressure rises
  • The action know as the Valsalva manuever can also stabilize the trunk when one lifts a heavy load
the trachea
The Trachea
  • The trachea descends from the larynx through the neck and into the mediastinum
  • It ends by dividing into the two primary bronchi at midthorax
  • 10 cm long and 2.5 cm in diameter
  • The trachea is very flexible and mobile
the tracheal wall
The Tracheal Wall
  • The tracheal wall consists of several layers that are common in many tubular organs of the body
the tracheal wall44
The Tracheal Wall
  • From internal to external these layers are the mucosa, submucosa, and adventitia
the tracheal wall45
The Tracheal Wall
  • The mucosa contains the same goblet cells containing pseudostratifed epithelium that occurs throughout most the of respiratory tract
the tracheal wall46
The Tracheal Wall
  • Its cilia continually propel mucus, loaded with dust particles and other debris, toward the larynx
the tracheal wall47
The Tracheal Wall
  • Smoking inhibits and ultimately destroys the cilia in the mucosa layer
  • When their function is lost, coughing is the only means of preventing mucus from accumulating in the lungs
  • Smokers with respiratory congestion should avoid medications that inhibit the cough reflex
the tracheal wall48
The Tracheal Wall
  • The submucosa, a connective tissue layer, contains seromucous glands that help produce the mucus “sheets” within the trachea
the tracheal wall49
The Tracheal Wall
  • The adventitia is a connective tissue layer that is reinforced by 16 to 20 C-shaped rings of hyaline cartilage
the tracheal wall50
The Tracheal Wall
  • The cartilage rings prevent the trachea from collapsing and keep the airway open despite the changes in pressure that occur in breathing
the tracheal wall51
The Tracheal Wall
  • The open posterior parts of the rings, which abut the esophagus are connected by smooth muscle fibers of the trachealis muscle and soft connective tissue
the tracheal wall52
The Tracheal Wall
  • Since this portion of the tracheal wall is not rigid, the esophagus can expand anteriorly as swallowed food passes through it
the trachea53
The Trachea
  • The last tracheal cartilage is expanded and a spar of cartilage called the carina projects posteriorly from its inner surface, marking the point where the trachea splits
  • Contacting this point results in violent coughing
the trachea54
The Trachea
  • Tracheal obstruction is life threatening
  • The Heimlich maneuver was developed to expel an obstruction using the residual air in the victim’s lungs
  • The maneuver creates interthoracic pressure that drives the obstruction from its lodging point
the conducting zone
The Conducting Zone
  • The right and left primary bronchi are formed by the division of the trachea at the level of T5
the conducting zone56
The Conducting Zone
  • Each bronchi runs obliquely in the mediastinum before plunging into the medial depression (hilus) of the lung on each side
conducting zone bronchial tree
Conducting Zone: Bronchial Tree
  • Once inside the lungs, each primary bronchus sub- divides into secondary and then tertiary bronchi which then divide further (23 orders of branching)
the conducting zone58
The Conducting Zone
  • Air passages under 1mm in diameter are called bronchioles and the smallest of these are called terminal bronchioles and are less than 0.5mm
the conducting zone59
The Conducting Zone
  • The tissue composition of the walls of the primary bronchi mimics that of the trachea but as the conducting tubes become smaller, a number of structural changes occurs
    • The cartilage supports change
      • Rings are replaced by plates and then none at all
    • The epithelium type changes
      • Pseudostratified columnar, to columnar, to cuboidal
      • Debris removed by macrophages at bronchiole level
    • The amount of smooth muscle increases
      • A complete layer of circular smooth muscle allows for vasoconstriction and vasodilation
the respiratory zone
The Respiratory Zone
  • The respiratory zone begins as the terminal bronchioles feed into respiratory bronchioles within the lungs
  • Protruding from these smallest bronchioles are scattered alveoli
the respiratory zone61
The Respiratory Zone
  • The respiratory bronchioles lead into alveolar ducts
  • The ducts lead into terminal clusters of alveoli called alveolar sacs
  • Respiration takes place within the alveoli
the respiratory membrane
The Respiratory Membrane
  • The walls of the alveoli are composed primarily of a single cell layer of squamous epithelial cells, called Type I cells underlain by a flimsy basal lamina
  • The cell walls are extremely thin to allow for ease of gas exchange
the respiratory membrane63
The Respiratory Membrane
  • The external surfaces of the alveoli are densely covered with a web of pulmonary capillaries
  • Together the alveolar and capillary walls and their fused basal lamina form the respiratory membrane with gas on one side and blood on the other
the respiratory membrane64
The Respiratory Membrane
  • Gas exchange occurs by simple diffusion across the respiratory membrane
  • Oxygen from the alveoli passes into the blood and carbon dioxide leaves the blood to enter the alveoli
the respiratory membrane65
The Respiratory Membrane
  • Scattered amid the type I squamous cells that form the alveoli walls are cuboidal type II cells
  • Type II cells secrete a fluid containing a surfactant that coats the alveolar surfaces which reduces the surface tension of the alveolar fluid

Type II Cell

the respiratory membrane66
The Respiratory Membrane
  • Lung alveoli have three other features
    • Surrounded by fine elastic fibers
    • Open pores connect adjacent alveoli
      • Allow for pressure equalization
      • Alternative air routes for blocked bronchi
    • Alveolar macrophages crawl freely along the internal alveolar surfaces


the lung
The Lung
  • The lungs occupy all of the thoracic cavity except the mediastinum
  • Each cone shaped lung is suspended in its own pleural cavity and connected to the mediastinum
the lung68
The Lung
  • The anterior, lateral and posterior lung surfaces lie in close contact with the ribs and forms a curving surface called the costal surface
  • The apex is the superior tip of the lung
the lung69
The Lung
  • The concave inferior surface that rests on the diaphragm is called the base
  • The hilus is the location where the pulmonary and systemic circulation and the primary bronchi enter
the lung70
The Lung
  • The left lung is divided into two lobes (upper and lower) while the right has three lobes (upper, middle, lower)
  • Each of the lobes contains a number of bronchopulmonary segments separated by connective tissue
  • Each lung has 10 segment
the pluera
The Pluera
  • The pleura is a thin, double layered serosa
  • The parietal pleura lines the thoracic wall and superior surface of the diaphragm
  • The visceral pleura covers the external surface of the lung
  • The pleura produce the fluid that lubricate the membrane
end of material

End of Material

Chapter 23