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ANP1105 (101)
Chapter 22

ANP1105 Chapter 22: The Respiratory System (p. 801-816) Functional Anatomy of the Respiratory System

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Anatomy and Physiology
Jacqueline Carnegie

Major function of respiratory system is to supply body with oxygen and dispose of CO2. To achieve this, four processes must happen called respiration: I. Pulmonary ventilation (breathing):Air is moved in & out of lungs (inspiration and expiration); gases are continually refreshed II. External respiration: oxygen diffuses from lungs to blood; CO2 diffuses from blood to lungs III. Transport of respiratory gases: Oxygen is transported from lungs to tissues of body; CO2 is transported from tissues of body to lungs. Uses blood as transporting fluid (cardiovascular system) IV. Internal respiration: oxygen diffuses from blood to tissue cells; CO2 diffuses from tissue cells to blood *Respiratory handles first two processes, CV (cardiovascular) handles last two processes Respiratory system consists of two zones: respiratory zone & conducting zone • Respiratory zone: actual site of gas exchange. Composed of bronchioles, alveolar ducts and alveoli (all microscopic) • Conducting zone (respiratory passageways): includes: nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles o also cleanses, humidifies and warms incoming air Nose: • functions: o provides an airway for respiration o moistens and warms entering air o filters and cleans inspired air o serves as resonating chamber for speech o houses olfactory (smell) receptors • structures are divided into external nose and internal nasal cavity External nose: • difference in shape and size due to differences in nasal cartilage • includes: o root: area between eyebrows o bridge o dorsum nasi: terminates in apex (tip of nose) o nostrils: external openings; bound by flared alae • skin covering nose is thin & contains many sebaceous glands • Pathway:Air enters nasal cavity via external nares (nostrils): divided by midline nasal septum (formed anteriorly by cartilage and posteriorly by bone).Air then goes via internal nares to nasopharynx. Nasal cavity: • Roof of nasal cavity (area between eyebrows) is formed from ethmoid and sphenoid bones • Floor of nasal cavity is formed by palate (anterior is hard; posterior is soft): separates nasal cavity from oral cavity below • Vibrissae: Hair follicles that filter coarse particles (ex: dust and pollen) from inspired air • Nasal cavity lined by two types of mucosa: olfactory mucosa and respiratory mucosa o Olfactory mucosa: contains receptors for smell o Respiratory mucosa: pseudostratified ciliated columnar epithelium with goblet cells; lamina propria has mucous & serous glands (1 L/day sticky mucus containing lysozyme: antibacterial enzyme)  Respiratory mucosa cilia move contaminated mucus posteriorly to throat where it is swallowed and digested  Cold air makes cilia sluggish and mucus accumulates = runny nose  Veins underlie the nasal epithelium and when inspired air is cold, the vein is engorged with blood. Due to the vein’s thin walls, they burst and nosebleeds occur. • Nasal conchae: o Mucus-covered projections protruding from the nasal cavity o Increase mucosal surface area exposed to air and enhance air turbulence in the cavity o Air must twist and turn to avoid the mucus, and large particles are not likely to pass through • nasal mucosa richly supplied with sensory nerves, so irritants trigger sneeze reflex Paranasal sinuses: • surround nasal cavity • located in frontal, sphenoid, ethmoid and maxillary bones • they lighten the skull, produce mucus & warm and moisten air • nasal mucosa is continuous with sinus mucosa increasing spread of infection • sinus headache: passageways connecting sinuses to nasal cavity blocked > air in sinus absorbed > partial vacuum Pharynx: • commonly called the throat: common pathway for food and air • extends 13 cm, composed of skeletal muscle; mucosal lining varies • divided into three regions: nasopharynx, oropharynx and laryngopharynx Nasopharynx: • above soft palate & below sphenoid bone • serves only as an air passageway • Swallowing: the soft palate and its uvula move forward and close off the nasopharynx, preventing food from entering the nasal cavity • Nasopharynx is continuous with nasal cavity, so pseudostratified ciliated epithelium takes over the job of propelling mucus where the nasal mucosa leaves off • Pharyngeal tonsil: traps and destroys pathogens entering nasopharynx by air • Pharyngotympanic (auditory) tubes: drain the middle ear cavities and allow middle ear pressure to equalize with atmospheric pressure o Ridge of pharyngeal mucosa constitutes the tubal tonsil which helps protect the middle ear against infections likely to spread from the nasopharynx Oropharynx: • Isthmus of the fauces connect oral cavity to oropharynx • Extends from soft palate to epiglottis, so both swallowed food and air pass through • As nasopharynx blends into oropharynx, the epithelium changes from pseudostratified columnar to a more protective stratified squamous: accomadates the increased friction and chemical trauma accompanying food passage • Paired palatine tonsils + lingual tonsil Laryngopharynx: • Passageway for food and air • Lined with stratified squamous epithelium • Extends from epiglottis to larynx where respiratory and digestive pathways diverge (go separate ways) • During swallowing, food has “right of way” and air passage stops Larynx (voice box): • Extends 5 cm from 3 -6 cervical vertebra • Attaches to hyoid bone (above) and continuous with trachea (below) • 3 functions: o Produce an open airway o Act as a switching mechanism to route air and food into proper channels o Voice production: houses vocal cords • 9 cartilages connected by membranes and ligaments o Except for epiglottis, all nine are cartilaginous • Thyroid cartilage: formed by fusion of two cartilage plates o Adam’s apple marks the fusion point o Larger in males than females because male sex hormones stimulate its growth during puberty • Arytenoid cartilages (2): pyramid-shaped which anchor the vocal folds • Epiglottis: o 9 cartilage. o Flexible o Composed of elastic cartilage o Covered by taste-bud mucosa o Anchors to anterior rim of thyroid cartilage & extends up to base of tongue • True vocal cords: white (lack blood vessels); vibrate, producing sounds as air ruses up from the lungs o Opening between the vocal cords is called glottis • False vocal cords:
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