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Copyright 2010, John Wiley & Sons, Inc. Chapter 7 The Respiratory System.

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Presentation on theme: "Copyright 2010, John Wiley & Sons, Inc. Chapter 7 The Respiratory System."— Presentation transcript:

1 Copyright 2010, John Wiley & Sons, Inc. Chapter 7 The Respiratory System

2 Copyright 2010, John Wiley & Sons, Inc. Respiration: Three Major Steps 1.Pulmonary ventilation  Moving air in and out of lungs 2.External respiration  Gas exchange between alveoli and blood 3.Internal respiration  Gas exchange between blood and cells

3 Copyright 2010, John Wiley & Sons, Inc. Organs of the Respiratory System Upper respiratory system  Nose and pharynx Lower respiratory system  Trachea, larynx, bronchi, bronchioles, and lungs “Conducting zone” consists of  All airways that carry air to lungs: Nose, pharynx, trachea, larynx, bronchi, bronchioles, and terminal bronchioles “Respiratory zone”  Sites within lungs where gas exchange occurs Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli

4 Copyright 2010, John Wiley & Sons, Inc. Organs of the Respiratory System

5 Copyright 2010, John Wiley & Sons, Inc. Upper Respiratory System: Nose Structure  External nares  nasal cavity  internal nares  Nasal septum divides nose into two sides  Nasal conchae covered by mucous membrane Functions  Warm, humidify, filter/trap dust and microbes Mucus and cilia of epithelial cells lining nose  Detect olfactory stimuli  Modify vocal sounds

6 Copyright 2010, John Wiley & Sons, Inc. Upper Respiratory System: Pharynx Known as the “throat” Structure  Funnel-shaped tube from internal nares to larynx 3 parts Three regions (with tonsils in the upper two)  Upper: nasopharynx; posterior to nose Adenoids and openings of auditory (Eustachian) tubes  Middle: oropharynx; posterior to mouth Palatine and lingual tonsils are here  Lower: laryngeal pharynx Connects with both esophagus and larynx: food and air

7 Copyright 2010, John Wiley & Sons, Inc.

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9 Respiratory System: Head and Neck

10 Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Larynx “Voice box” Made largely of cartilage  Thyroid cartilage: V-shaped “Adam's apple”: projects more anteriorly in males Vocal cords “strung” here (and to arytenoids)  Epiglottis: leaf-shaped piece; covers airway During swallowing, larynx moves up so epiglottis covers opening into trachea  Cricoid cartilage: inferior most portion  Arytenoids (paired, small) superior to cricoid

11 Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Larynx

12 Copyright 2010, John Wiley & Sons, Inc. Voice Production Mucous membrane of larynx forms two pairs of folds  Upper = false vocal cords  Lower = true vocal cords Contain elastic ligaments When muscles pull elastic ligaments tight, vocal cords vibrate  sounds in upper airways Pitch adjusted by tension of true vocal cords Lower pitch of male voice  Vocal cords longer and thicker; vibrate more slowly

13 Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Trachea “Windpipe” Location  Anterior to esophagus and thoracic vertebrae  Extends from end of larynx to primary bronchi Structure  Lined with pseudostratified ciliated mucous membrane: traps and moves dust upward  C-shaped rings of cartilage support trachea, keep lumen open during exhalation Tracheostomy: opening in trachea for tube

14 Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Bronchi, Bronchioles Structure of bronchial tree  Bronchi contain cartilage rings  Primary bronchi enter the lungs medially  In lungs, branching  secondary bronchi One for each lobe of lung: 3 in right, 2 in left  Tertiary bronchi    terminal bronchioles These smaller airways  Have less cartilage, more smooth muscle. In asthma, these airways can close.  Can be bronchodilated by sympathetic nerves, epinephrine, or related medications.

15 Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Lungs Two lungs: left and right  Right lung has 3 lobes  Left lung has 2 lobes and cardiac notch Lungs surrounded by pleural membrane  Parietal pleura attached to diaphragm and lining thoracic wall  Visceral pleura attached to lungs  Pleural cavity with little fluid between pleurae  Broad bottom of lungs = base; pointy top = apex

16 Copyright 2010, John Wiley & Sons, Inc. Lung Lobes Divided into lobules fed by tertiary bronchi Further divisions  terminal bronchioles  Respiratory bronchioles  Lined with nonciliated epithelium  Alveolar ducts  Alveolar sacs  Surrounded by alveoli

17 Copyright 2010, John Wiley & Sons, Inc. Lung Lobes

18 Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Alveoli Cup-shaped outpouchings of alveolar sacs Alveoli: composed of three types of cells  Lined with thin alveolar cells (simple squamous); sites of gas exchange  Scattered surfactant-secreting cells. Surfactant: Lowers surface tension (keeps alveoli from collapsing) Humidifies (keeps alveoli from drying out)  Alveolar macrophages: “cleaners” Respiratory membrane: alveoli + capillary  Gases diffuse across these thin epithelial layers: air  blood

19 Copyright 2010, John Wiley & Sons, Inc. Lobule of the Lung

20 Copyright 2010, John Wiley & Sons, Inc. Lobule of the Lung

21 Copyright 2010, John Wiley & Sons, Inc. Structure of an Alveolus

22 Copyright 2010, John Wiley & Sons, Inc. Respiration Step: 1. Pulmonary Ventilation Air flows: atmosphere   lungs due to difference in pressure related to lung volume  Lung volume changes due to respiratory muscles Inhalation: diaphragm + external intercostals  Diaphragm contracts (moves downward)   lung volume Cohesion between parietal-visceral pleura   lung volume as thorax volume .

23 Copyright 2010, John Wiley & Sons, Inc. Exhalation Exhalation is normally passive process due to muscle relaxation  Diaphragm relaxes and rises   lung volume  External intercostals relax   lung volume Active exhalation: exhale forcefully  Example: playing wind instrument  Uses additional muscles: internal intercostals, abdominal muscles

24 Copyright 2010, John Wiley & Sons, Inc. Muscles of Inhalation and Exhalation

25 Copyright 2010, John Wiley & Sons, Inc. Muscles of Inhalation and Exhalation

26 Copyright 2010, John Wiley & Sons, Inc. Volume-Pressure Changes in Lungs Volume and pressure are inversely related  As  lung volume   alveolar pressure  As  lung volume   alveolar pressure Contraction of diaphragm  lowers diaphragm   lung volume   alveolar pressure so it is < atmospheric pressure  air enters lungs = inhalation Relaxation of diaphragm  raises diaphragm   lung volume   alveolar pressure so it is > atmospheric pressure  air leaves lungs = exhalation

27 Copyright 2010, John Wiley & Sons, Inc. Volume-Pressure Changes in Lungs

28 Copyright 2010, John Wiley & Sons, Inc. Air Flow Terms Frequency = breaths/min; normal: 12 Tidal volume (TV) = volume moved in one breath. Normal ~ 500 ml  About 70% of TV reaches alveoli (350 ml)  Only this amount is involved in gas exchange  30% in airways = anatomic dead space Minute ventilation (MV) = f x TV = 6000 mL/min

29 Copyright 2010, John Wiley & Sons, Inc. Lung Volumes Measured by spirometer  Inspiratory reserve volume (ERV) = volume of air that can be inhaled beyond tidal volume (TV)  Expiratory reserve volume (IRV) = volume of air that can be exhaled beyond TV  Air remaining in lungs after a maximum expiration = residual volume (RV)

30 Copyright 2010, John Wiley & Sons, Inc. Lung Capacities Inspiratory capacity = TV + IRV Functional residual capacity (FRC) = RV + ERV Vital capacity (VC) = IRV + TV + ERV Total lung capacity (TLC) = VC + RV

31 Copyright 2010, John Wiley & Sons, Inc. Lung Capacities

32 Copyright 2010, John Wiley & Sons, Inc. Respiration Step 2: Pulmonary Gas Exchange: External Respiration Diffusion across alveolar-capillary membrane  O 2 diffuses from air (P O2 ~105 mm Hg) to pulmonary artery (“blue”) blood (P O2 ~40 mm Hg). (Partial pressure gradient = 65 mm Hg) Continues until equilibrium (P O2 ~ mm Hg)  Meanwhile “blue” blood (P CO2 ~45) diffuses to alveolar air (P CO2 ~40) (Partial pressure gradient = 5 mm Hg)

33 Copyright 2010, John Wiley & Sons, Inc. Respiration Step 3: Systemic Gas Exchange: Internal Respiration Occurs throughout body O 2 diffuses from blood to cells: down partial pressure gradient P O2 lower in cells than in blood because O 2 used in cellular metabolism Meanwhile CO 2 diffuses in opposite direction: cells  blood

34 Copyright 2010, John Wiley & Sons, Inc. Internal and External Respiration

35 Copyright 2010, John Wiley & Sons, Inc. Transport of Oxygen within Blood 98.5% of O 2 is transported bound to hemoglobin in RBCs  Binding depends on P O2  High P O2 in lung and lower in tissues  O 2 dissolves poorly in plasma so only 1.5% is transported in plasma Tissue release of O 2 to cells is increased by factors present during exercise:  High CO 2 (from active muscles)  Acidity (lactic acid from active muscles)  Higher temperatures (during exercise)

36 Copyright 2010, John Wiley & Sons, Inc. Transport of Carbon Dioxide CO 2 diffuses from tissues into blood  CO 2 carried in blood:  Some dissolved in plasma (7%)  Bound to proteins including hemoglobin (23%)  Mostly as part of bicarbonate ions (70%) CO 2 + H 2 O  H + + HCO 3 - Process reverses in lungs as CO 2 diffuses from blood into alveolar air  exhaled

37 Copyright 2010, John Wiley & Sons, Inc. Transport of Oxygen and Carbon Dioxide

38 Copyright 2010, John Wiley & Sons, Inc. Control of Respiration Medullary rhythmicity area in medulla  Contains both inspiratory and expiratory areas Quiet breathing  Inspiratory area  nerve signals to inspiratory muscles for ~2 sec   Inspiration   Inspiration ends and muscles relax   Expiration   Expiratory center active only during forceful breathing Two areas in pons adjust length of inspiratory stimulation

39 Copyright 2010, John Wiley & Sons, Inc. Control of Respiration

40 Copyright 2010, John Wiley & Sons, Inc. Control of Respiration

41 Copyright 2010, John Wiley & Sons, Inc.

42 Regulation of Respiratory Center Cortical input: voluntary adjustment of patterns  For talking or cessation of breathing while swimming  Chemoreceptor input will override breath-holding

43 Copyright 2010, John Wiley & Sons, Inc. Regulation of Respiratory Center Chemoreceptor input to  increase ventilation  Central receptors in medulla: sensitive to  H+ or PCO2 in CSF  Peripheral receptors in arch of aorta + common carotids: respond to  PO2 as well as  H+ or PCO2 in blood Blood and brain pH can be maintained by these negative feedback mechanisms

44 Copyright 2010, John Wiley & Sons, Inc. Regulation of Respiratory Center

45 Copyright 2010, John Wiley & Sons, Inc. Other Regulatory Factors of Respiration Respiration can be stimulated by  Limbic system: anticipation of activity, emotion  Proprioception as activity is started  Increase of body temperature Sudden pain can  apnea: stop breathing  Prolonged somatic pain can increase rate Airway irritation  cough or sneeze Inflation reflex  Bronchi wall stretch receptors inhibit inspiration  Prevents overinflation

46 Copyright 2010, John Wiley & Sons, Inc. Aging and the Respiratory System Lungs lose elasticity/ability to recoil  more rigid; leads to  Decrease in vital capacity  Decreased blood P O2 level  Decreased exercise capacity Decreased macrophage activity and ciliary action   Increased susceptibility to pneumonia, bronchitis and other disorders


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