1. The Respiratory System
Chapter 18

2. Operations Pulmonary ventilation External respiration
Moving air in & out
External respiration
Gas exchange between alveoli & blood
Internal respiration
Gas exchange between blood & cells
Helps pH control

3. Anatomical Components
Upper respiratory tract
nose, pharynx
Lower Respiratory System
Trachea, larynx & bronchi & lungs
Conducting zone = tubing
Respiratory Zone= Gas exchange
Bronchioles, alveolar sacs & alveoli

4. Figure 18.1

5. Nose Nose: external nares nasal cavity internal nares
Nasal septum splits in two
Nasal conchae swirl air over mucus membrane
Designed to: Filter, Warm, Humidify
Trap dust and infectious agents
Detect olfactory stimuli
Modify vocal sounds

6. Pharynx Funnel shaped tube from internal nares to larynx = “throat”
Upper = naso pharynx
Middle = oropharynx
Between uvula & top of epiglottis
lower = laryngeal pharynx
Connects with both esophagus & larynx
Thus both air & food & drink

7. Figure 18.2

8. Larynx Short tube of cartilage Thyroid cartilage-
anterior = “Adam's apple”
Epiglottis – upper leaf-shaped piece
During swallowing larynx moves up and epiglottis covers opening to trachea
Cricoid cartilage- forms inferior wall
Paired arytenoids- above cricoid
attach to vocal cords & pharyngeal muscles

9. Figure 18.3

10. Voice Production Mucous membrane of larynx  two pairs of folds
Upper = false vocal cords
Lower = true vocal cords
Contain elastic ligaments stretched between cartilage
Move out into air way and vibrate
Pitch adjusted by tension and diameter of ligaments

11. Trachea
Trachea- larynx  upper part of T5 vertebra R. & L. primary bronchus
Lined with pseudostratified ciliated mucous membrane 
dust protection – move toward pharynx
C-shaped cartilage rings keep lumen open

12. Bronchi & Bronchioles Bronchi also contain cartilage rings
Primary bronchi enter the lungs
Blood vessels, lymphatic vessels & nerves enter lungs with bronchi
In lungs branch secondary bronchi
one for each lobe of lung
 tertiary bronchi  terminal bronchi
Smaller bronchi have less cartilage and more smooth muscle
ANS can adjust diameter = resistance to flow

13. Lungs Two organs (R. & L) Surrounded by pleural membrane
Parietal pleura attached to diaphragm & thoracic wall
Visceral pleura attached to lungs
Between is pleural cavity filled with fluid
Broad bottom = base; Pointy top = apex
Right lung has 3 lobes
Left lung has 3 lobes & cardiac notch

14. Lung Lobes Divided in lobules fed by tertiary bronchus
Further divisions terminal bronchiole
 respiratory bronchiole
Lined with non-ciliated cuboidal epithelium
 alveolar ducts  alveolar sacs 

15. Figure 18.4

16. Alveoli Cup-shaped out pouch of sac
Lined with thin alveolar cells (simple squamous)
Scattered surfactant secreting cells
Lowers surface tension & humidifies
Alveolar macrophages- “cleaners”
Gases diffuse across combined epithelia of alveolus & capillary
Combination called: Respiratory Membrane

17. Figure 18.5

18. Figure 18.6

19. Pulmonary Ventilation
Air flows between atmosphere & lungs due to difference in pressure
Caused by respiratory muscles
Inhalation: diaphragm & external intercostals
Diaphragm contracts  lung volume
Lung moves due to seal between parietal & visceral plura

20. Exhalation
Resting exhalation due to muscle relaxation= passive process
Diaphragm rises & ribs fall   lung volume
Can be active using internal intercostals & abdominal muscles
Push diaphragm up & pull ribs in 
More  lung volume

21. Figure 18.7a

22. Figure 18.7b

23. Pressure Changes  lung volume   alveolar pressure
Atmospheric pressure is constant
Atmospheric > alveolar inhalation
During exhalation   lung rises
Alveolar> Atmospheric  exhalation

24. Figure 18.8

25. Air Flow Terms Frequency (f) = breaths per minute
Normal ~12 breaths per min
Tidal volume (TV) = volume moved in one breath
Normal ~ 500 ml
Minute Ventilation (MV) = f x TV
~ 70% of TV reaches alveoli (350 ml)
Only this involved in gas exchange
30% in airways = Anatomic Dead Space

26. Lung Volumes Inspiration beyond resting = Inspiratory reserve volume
Expiration beyond resting (active) = Expiratory reserve volume
Air left after a maximum expiration = residual volume

27. Lung Capacities Inspiratory capacity= Functional residual capacity =
TV + inspiratory reserve
Functional residual capacity =
Residual volume + expiratory reserve
Vital capacity (VC) =
Expiratory reserve + TV + Inspiratory reserve
Total lung capacity = VC + residual

28. Figure 18.9

29. Breathing Patterns Eupnea = normal breathing
Highly variable in pattern
Special modifications for speech and emotional responses
Also variations fro coughing & sneezing to clear airways
See table 18.1

30. Nature of Air Mixture of gases (N2, O2,, CO2, H2O & others)
Each gas has own partial pressure (Px)
Each gas diffuses down partial pressure gradient
Total = sum of partial pressures = atmospheric pressure

31. Pulmonary Gas Exchange: External Respiration
O2 diffuses from air (PO2 ~105mm Hg)  incoming blood (PO2 ~40mm Hg)
Continues until equilibrium (PO2 ~105mm Hg)
Some unexchanged mixture in out flow so Arterial blood is ~100 mmHg
Meanwhile blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40)
Again to equilibrium

32. Systemic Gas Exchange: Internal Respiration
Occurs throughout body
O2 diffuses from blood to cells
PO2 lower in cells because of use
Meanwhile CO2 diffuses in opposite direction

33. Figure 18.10

34. Transport of Oxygen
O2 dissolves poorly 98.5% bound to hemoglobin in RBCs
Binding depends on PO2
High at lung and lower at tissue PO2s
Tissue release of O2 increased by:
High CO2
Acidity
Higher temperatures

35. Transport of Carbon Dioxide
As comes in to blood from cells
Some dissolved (7%)
Bound to proteins including Hemoglobin (23%)
Becomes bicarbonate ions (70%)
CO2 + H2O <=> H+ + HCO3-
Process reverses at lungs

36. Figure 18.11

37. Control of Respiration
Medullary respiratory area in medulla
Contains both inspiratory & expiratory areas
Quiet breathing:
inspiratory area nerve signals to inspiratory muscles for ~2 sec
inspiration
Then becomes inactive & muscles relax
Expiration
Expiratory centre active only during forceful breathing
Area in pons adjusts length of inspiratory stimulation

38. Figure 18.12a

39. Figure 18.12b

40. Regulation of Respiratory Center
Cortical input: voluntary adjustment of patterns
Protection & talking
Chemoreceptor input will override breath-hold
Chemoreceptor input
Central receptors in medulla
Peripheral receptors in arch of aorta
respond to increased H+ or PCO2 increased ventilation
Thus negative feedback loop to maintain blood & brain pH
Significant falls in PO2 also stimulates breathing

41. Figure 18.13

42. Other Regulatory Factors
Limbic system-
anticipation of activity or emotion can stimulate
Proprioception stimulates on start of activity
Temperature  warming increases
Pain- Sudden pain  apnea
Prolonged somatic pain can increase rate
Airway irritation cough or sneeze
Inflation reflex- bronchi wall stretch receptors inhibit inspiration
Prevents overinflation

43. Aging Everything becomes less elastic  Decrease in Vital capacity
Can decrease blood O2 level
Decreased exercise capacity
Decreased macrophage activity
Increased susceptibility to pulmonary disease