respiratory system

1. Hole’s Human Anatomy
and Physiology
Twelfth Edition
Shier  Butler  Lewis
Chapter
19
Respiratory System
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1

2. 19.1: Introduction
• The respiratory system consists of passages that filter
incoming air and transport it into the body, into the lungs, and
to the many microscopic air sacs where gases are exchanged
• Respiration is the process of exchanging gases between the
atmosphere and body cells
• It consists of the following events:
• Ventilation
• External respiration
• Transport of gases
• Internal respiration
• Cellular respiration
2

3. 19.2: Why We Breathe
• Respiration occurs on a macroscopic level at the organ
system
• Gas exchange, oxygen and carbon dioxide, occur at the
cellular and molecular levels
• Aerobic reactions of cellular respiration allow for:
• ATP production
• Carbon dioxide generation forming carbonic acid
3

4. 19.3: Organs of the
Respiratory System
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• The organs of the respiratory
system can be divided into two
tracts:
• Upper respiratory tract
• The nose
• Nasal cavity
• Sinuses
• Pharynx
• Lower respiratory tract
• Larynx
• Trachea
• Bronchial tree
• Lungs
Frontal
sinus
Nasal
cavity
Hard
palate
Soft palate
Pharynx
Nostril
Oral
cavity
Larynx
Epiglottis
Esophagus
Trachea
Bronchus
4
Right lung
Left lung

5. Nose
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Frontal sinus
Superior
Middle
Inferior
Nasal
conchae
Sphenoidal sinus
Nostril
Hard palate
Uvula
Tongue
Hyoid bone
Pharyngeal tonsil
Nasopharynx
Opening of
auditory tube
Palatine tonsil
Oropharynx
Lingual tonsil
Epiglottis
Laryngopharynx
Larynx
Trachea
Esophagus
5

6. Nasal Cavity
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Nasal cavity
Mucus
Particle
Cilia
Goblet cell
Epithelial cell
(a)
(b)
b: © Biophoto Associates/Photo Researchers, Inc.
pseudostratified columnar epithelium with cilia
and goblet cells
6

7. Sinuses
• The sinuses are air-filled spaces
in the maxillary, frontal, ethmoid,
and sphenoid bones of the skull
7

8. Pharynx
• The pharynx is posterior to the oral cavity and between the nasal
cavity and the larynx
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Superior
Frontal sinus
Middle
Inferior
Nasal
conchae
Sphenoidal sinus
Nostril
Hard palate
Uvula
Tongue
Pharyngeal tonsil
Nasopharynx
Opening of
auditory tube
Palatine tonsil
Oropharynx
Lingual tonsil
Epiglottis
Hyoid bone
Laryngopharynx
Larynx
Trachea
Esophagus
8

9. Larynx
• The larynx is an enlargement in the
airway superior to the trachea and
inferior to the pharynx
• It is composed of a framework of
muscles and cartilages bound by
elastic tissue
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Epiglottis
Hyoid bone
False vocal cord
Thyroid cartilage
Glottis
Cricoid cartilage
True vocal
cord
(a)
Thyroid cartilage
Cuneiform cartilage
Hyoid bone
Epiglottis
Arytenoid cartilage
Epiglottic cartilage
False vocal
cord
Thyroid cartilage
True vocal cord
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Cricoid cartilage
Corniculate cartilage
Hyoid bone
(b)
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Thyroid cartilage
Posterior portion
of tongue
Cricoid cartilage
Glottis
False vocal cord
True vocal cord
Cuneiform cartilage
Corniculate cartilage
(a)
Trachea
(a)
Epiglottis
Glottis
Hyoid bone
Inner lining of trachea
(b)
Epiglottic cartilage
Thyroid cartilage
9
Cricoid cartilage
(b)
Trachea
(c)
c: © CNRI/PhotoTake

10. Trachea
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• The trachea (windpipe) is a
flexible cylindrical tube about
2.5 centimeters in diameter
and 12.5 centimeters in length
• As it extends downward
anterior to the esophagus and
into the thoracic cavity, it
splits into the right and left
primary bronchi
Larynx
Thyroid
cartilage
Cricoid
cartilage
Trachea
Superior (upper)
lobe bronchus
Cartilaginous
ring
Carina
Left
primary
bronchus
Right primary
bronchus
Middle lobe
bronchus
Superior (upper)
lobe bronchus
Inferior (lower)
lobe bronchi
10

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lumen of trachea
Hyaline cartilage
Ciliated epithelium
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Hyoid
bone
Smooth muscle
Connective tissue
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Connective
tissue
Smooth
muscle
Thyroid gland
Thyroid
cartilage
Cricoid
cartilage
Incision
Trachea
Jugular
notch
Hyaline
cartilage
Ciliated
epithelium
Lumen of
trachea
© Ed Reschke
11

12. Bronchial Tree
• The bronchial tree
consists of branched
airways leading from
the trachea to the
microscopic air sacs in
the lungs
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Larynx
Trachea
Right superior (upper) lobe
Left superior
(upper) lobe
Right primary bronchus
Secondary bronchus
Tertiary bronchus
Terminal bronchiole
Right inferior (lower) lobe
Right middle lobe
Left inferior
(lower) lobe
Respiratory bronchiole
Alveolar duct
Alveolus
12

13. Branches of the Bronchial Tree
• The successive divisions of
the branches from the trachea
to the alveoli are:
1.Right and left primary
bronchi
2.Secondary or lobar bronchi
3.Tertiary or segmental
bronchi
4.Intralobular bronchioles
5.Terminal bronchioles
6.Respiratory bronchioles
7.Alveolar ducts
8.Alveolar sacs
9.Alveoli
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© Ralph Hutchings/Visuals Unlimited
13

14. Blood flow
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Blood flow
Intralobular bronchiole
Pulmonary
venule
Pulmonary
arteriole
Blood flow
Smooth muscle
Alveolus
Pulmonary
artery
Capillary network on
surface of alveolus
Pulmonary
vein
Terminal
bronchiole
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Respiratory
bronchiole
Alveolar
duct
Alveolar
sac
Alveoli
Capillary
Simple squamous
epithelial cells
Alveolus
© McGraw-Hill Higher Education, Inc./Bob Coyle
14

15. The Respiratory Tubes
• The structure of the bronchus is
similar to that of the trachea, but
the C-shaped cartilaginous rings
are replaced with cartilaginous
plates where the bronchus enters
the lung
• These respiratory tubes become
thinner and thinner, and the cell
layers thin and change until the
alveoli is reached
• It is the alveoli that provides
surface area for gas exchange
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Blood flow
Blood flow
Venule
Arteriole
Alveolar
wall
Alveolus
Air
O2
CO2
CO2 O2
Capillary
15

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Blood vessel
Capillary
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Alveolus
Alveolus
Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, by R.G. Kessel and
R.H. Kardon. © 1979 W.H. Freeman and Company
Bronchiole
Courtesy of the American Lung Association
16

17. Lungs
• The right and left lungs are soft, spongy, cone-shaped
organs in the thoracic cavity
• The right lung has three lobes and the left lung two lobes
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Right lung
Left lung
Thyroid cartilage
Cricoid cartilage
Plane of
section
Trachea
Clavicle
Scapula
Superior (upper)
lobe of right lung
Superior (upper)
lobe of left lung
Middle lobe
of right lung
Heart
Pericardial
cavity
Inferior (lower)
lobe of left lung
Inferior (lower)
lobe of right lung
Visceral
pleura
Parietal
pleura
Pericardium
Pleura
Right pleural
cavity
Left pleural
cavity
Rib cartilage
Sternum
17

18. 18

19. 19.4: Breathing Mechanism
• Breathing or ventilation is the movement of air from outside
of the body into the bronchial tree and the alveoli
• The actions responsible for these air movements are
inspiration, or inhalation, and expiration, or exhalation
19

20. Inspiration
• Atmospheric pressure due to
the weight of the air is the
force that moves air into the
lungs
• At sea level, atmospheric
pressure is 760 millimeters of
mercury (mm Hg)
• Moving the plunger of a
syringe causes air to move in
or out
• Air movements in and out of
the lungs occur in much the
same way
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Air passageway
Atmospheric pressure
of 760 mm Hg on the
outside
Atmospheric
pressure
of 760 mm Hg
on the inside
Diaphragm
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20
(a)
(b)

21. Inspiration
• Intra-alveolar pressure decreases to about 758mm Hg as the
thoracic cavity enlarges due to diaphragm downward
movement caused by impulses carried by the phrenic nerves
• Atmospheric pressure then forces air into the airways
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Atmospheric pressure
(760 mm Hg)
Intra-alveolar
pressure
(760 mm Hg)
Intra-alveolar
pressure
(758 mm Hg)
Diaphragm
(a)
(b)
21

22. Inspiration
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Sternocleidomastoid
elevates sternum
Sternum
moves
Up and out
Pectoralis minor
elevates ribs
External
intercostal
muscles pull
ribs up and out
Diaphragm
contracts
(a)
Diaphragm
contracts more
(b)
22

23. 23

24. Expiration
• The forces responsible for normal resting expiration come
from elastic recoil of lung tissues and from surface tension
• These factors increase the intra-alveolar pressure about 1 mm
Hg above atmospheric pressure forcing air out of the lungs
24

25. Expiration
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Posterior internal
intercostal muscles
pull ribs down and
inward
Diaphragm
Diaphragm
Abdominal organs
recoil and press
diaphragm upward
Abdominal organs
force diaphragm
higher
Abdominal wall
muscles contract
and compress
abdominal organs
(a)
(b)
25

26. 26

27. Respiratory Air
Volumes and Capacities
• Different degrees of effort in breathing move different
volumes of air in and out of the lungs
• This measurement of volumes is called spirometry
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Lung volume in milliliters (mL)
6,000
5,000
Inspiratory
reserve volume
Vital
capacity
4,000
3,000
2,000
1,000
0
Tidal
volume
Residual
volume
Expiratory
reserve volume
Inspiratory
capacity
Total lung
capacity
Functional
residual
capacity
27

28. 28

29. Alveolar Ventilation
• The volume of new atmospheric air moved into the
respiratory passages each minute is minute ventilation
• It equals the tidal volume multiplied by the breathing rate
• Much of the new air remains in the physiologic dead space
• The tidal volume minus the physiologic dead space then
multiplied by breathing rate is the alveolar ventilation rate
• This is the volume of air that reaches the alveoli
• This impacts the concentrations of oxygen and carbon
dioxide in the alveoli
29

30. Nonrespiratory Air Movements
• Air movements other than breathing are called
nonrespiratory movements
• They clear air passages, as in coughing and sneezing, or
express emotions, as in laughing and crying
30

31. 31

32. 19.5: Control of Breathing
• Normal breathing is a rhythmic, involuntary act that
continues when a person is unconscious
• Respiratory muscles can be controlled as well voluntarily
32

33. Respiratory Areas
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• Groups of neurons in the
brainstem comprise the
respiratory areas that control
breathing
• Impulses travel on cranial nerves
and spinal nerves, causing
inspiration and expiration
• Respiratory areas also adjust the
rate and depth of breathing
• The respiratory areas include:
• Respiratory center of the
medulla
• Respiratory group of the
Midbrain
Fourth
ventricle
Pontine respiratory
group
Pons
Medulla oblongata
Ventral respiratory group
Dorsal respiratory group
Medullary
respiratory
center
Internal (expiratory)
intercostal muscles
External (inspiratory)
intercostal muscles
Diaphragm
33

34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Respiratory areas
Pontine respiratory
group
Medullary respiratory center
Ventral
respiratory
group
Dorsal
respiratory
group
Nerve impulses
Nerve impulses
Respiratory muscles
Basic rhythm
of breathing
Forceful breathing
34

35. Factors Affecting Breathing
• A number of factors affect
breathing rate and depth
including:
• Partial pressure of
oxygen (Po2)
• Partial pressure of carbon
dioxide (Pco2)
• Degree of stretch of lung
tissue
• Emotional state
• Level of physical activity
• Receptors involved include
mechanoreceptors and central
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Medulla oblongata
Sensory nerve
(branch of
glossopharyngeal
nerve)
Carotid bodies
Sensory nerve
(branch of vagus nerve)
Common carotid
artery
Aorta
Aortic bodies
Heart
35

36. Factors Affecting Breathing
• Changes in blood pH, O2 and
CO2 concentration stimulates
chemoreceptors
Sensory pathway
• Motor impulses can travel
Vagus nerve
from the respiratory center
to the diaphragm and external Phrenic nerve
intercostal muscles
Stretch receptors
• Contraction of these muscles
Lung
causes the lungs to expand
stimulating mechanoreceptors in
the lungs
• Inhibitory impulses from the
mechanoreceptors back to the
respiratory center prevent
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Respiratory center
Spinal cord
–
–
Motor pathways
External intercostal
muscles
Intercostal nerve
Rib
Diaphragm
36

37. 37

38. 19.6: Alveolar Gas Exchanges
• The alveoli are the sites of the vital process of gas exchange
between the air and the blood
38

39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Type I
(squamous
epithelial) cell
of alveolar wall
Type II
(surfactantsecreting) cell
Fluid with
surfactant
Macrophage
Alveolus
Respiratory
membrane
Cell of
capillary wall
Capillary lumen
Alveolar fluid
(with surfactant)
Alveolar epithelium
Alveolus
Basement membrane of
alveolar epithelium
Interstitial space
Respiratory
membrane
Basement membrane of
capillary endothelium
Capillary endothelium
Diffusion of O2
Diffusion of CO2
Red blood cell
Capillary
39

40. Respiratory Membrane
• Part of the wall of an alveolus is made up of cells (type II
cells) that secrete pulmonary surfactant
• The bulk of the wall of an alveolus consists of a layer of
simple squamous epithelium (type I cells)
• Both of these layers make up the respiratory membrane
through which gas exchange takes place
40

41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EP
AS
BM
RBC
AS
IS
41
© Imagingbody.com

42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Alveolus
Diffusion of CO2
Alveolar
wall
PCO = 40 mm Hg
2
PCO = 45 mm Hg
2
PO = 104 mm Hg
2
Diffusion of O2
PO = 40 mm Hg
2
Blood flow
(from body
tissues)
Blood flow
(to body
tissues)
Capillary
PCO = 40 mm Hg
PO = 104 mm Hg
2
2
42

43. Diffusion Through the
Respiratory Membrane
• Molecules diffuse from regions where they are in higher
concentration toward regions where they are in lower
concentration
• It is important to know the concentration gradient
• In respiration, think in terms of gas partial pressures
• Gases diffuse from areas of higher partial pressure to areas of
lower partial pressure
• The respiratory membrane is normally thin and gas exchange
is rapid
• Increased diffusion is favored with more surface area,
shorter distance, greater solubility of gases and a steeper
partial pressure gradient
• Decreased diffusion occurs from decreased surface area 43

44. 19.7: Gas Transport
• Blood transports O2 and CO2 between the lungs and the
body cells
• As the gases enter the blood, they dissolve in the plasma or
chemically combine with other atoms or molecules
44

45. Oxygen Transport
• Almost all oxygen carried in the blood is bound to the protein
hemoglobin in the form of oxyhemoglobin
• Chemical bonds between O2 and hemoglobin are relatively
unstable
• Oxyhemoglobin releases O2 into the body cells
• About 75% of the O2 remains bound to hemoglobin in the
venous blood ensuring safe CO2 levels and thereby pH
45

46. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Alveolus
Blood
PO = 95 mm Hg
Capillary
2
Alveolar
wall
Oxygen
molecules
Diffusion
of oxygen
Hemoglobin
molecules
Blood
PO = 40 mm Hg
2
Blood flow
(to lungs)
Oxyhemoglobin
molecule
Blood flow
(from body
tissues)
(a)
Hemoglobin
molecules
Tissue cells
Tissue
PO = 40 mm Hg
Diffusion
of oxygen
2
(b)
46

47. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
100
% saturation of hemoglobin
90
80
70
60
50
40
30
20
10
0
10
20
30
40
50
60 70 80
PO2(mm Hg)
90 100 110 120 130 140
Oxyhemoglobin dissociation at 38°C
47

48. • The amount of oxygen released from oxyhemoglobin increases
with:
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100
80
70
PCO =
60
2
20 mm Hg
40 mm Hg
80 mm Hg
50
40
30
20
10
10
20
30
40
50
60 70 80
PO (mm Hg)
90
100 110 120 130 140
2
Oxyhemoglobin dissociation at 38°C
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100
90
80
70
pH =
60
7.6
50
7.4
7.2
40
30
20
10
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0
10
20
30
40
50
60
70
80
90
100
PO2 (mm Hg)
Oxyhemoglobin dissociation at 38°C
1 10
120
130
140
100
C
0°
90
% saturation of hemoglobin
0
% saturation of hemoglobin
% saturation of hemoglobin
90
10
80
°C
20
°C
30
70
°C
38
60
°C
43
50
°C
40
30
20
10
0
10
20
30
40
50
60
70
80
PO2 (mm Hg)
90
48 110
100
120
Oxyhemoglobin dissociation at various temperatures
130 140
48

49. Carbon Dioxide Transport
• Blood flowing through capillaries gains CO2 because the
tissues have a high Pco2
• The CO2 is transported to the lungs in one of three forms:
• As CO2 dissolved in plasma
• As part of a compound with hemoglobin
• As part of a bicarbonate ion
49

50. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Tissue cell
Tissue
PCO2 = 45 mm Hg
Cellular CO2
CO2 dissolved
in plasma
PCO = 40 mm Hg
2
Blood
flow from
systemic
arteriole
CO2 + H2O
CO2 combined with
hemoglobin to form
carbaminohemoglobin
H2CO3
PCO = 45 mm Hg
HCO + H
3
+
2
+
H combines
with hemoglobin
HCO3Plasma
Red blood cell
Blood
flow to
systemic
venule
Capillary wall
50

51. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Capillary wall
Cl-
Red blood cell
HCO3-
Plasma
Cl-
HCO3HCO3Cl-
51

52. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Alveolus
PCO = 40 mm Hg
2
CO2
CO2dissolved
in plasma
PCO = 45 mm Hg
2
Blood flow
from pulmonary
arteriole
HCO3-
Plasma
CO2
Alveolar wall
CO2 + H2O
3
H2CO3
CO2
Carbaminohemoglobin
H+ released
from hemoglobin
Red blood cell
PCO = 40 mm Hg
2
HCO + H
+
CO2 + hemoglobin
Blood
flow to
pulmonary
venule
Capillary wall
52

53. 53

54. 19.8: Lifespan Changes
• Lifespan changes reflect an accumulation of environmental
influences and the effects of aging in other organ systems,
and may include:
• The cilia become less active
• Mucous thickening
• Swallowing, gagging, and coughing reflexes slowing
• Macrophages in the lungs lose efficiency
• An increased susceptibility to respiratory infections
• A “barrel chest” may develop
• Bronchial walls thin and collapse
• Dead space increasing
54