1. © 2017 Pearson Education, Inc.

2. The Respiratory System (15-1)
Consists of structures involved in:
Physically moving air into and out of the lungs
Gas exchange
Takes place at air-filled pockets called alveoli

3. Five Functions of the Respiratory System (15-1)
Provides large area for gas exchange between air and circulating blood
Moves air along respiratory passageways to and from gas-exchange surfaces of the lungs
Protects respiratory surfaces from dehydration, temperature changes, and pathogens
Produces sounds for speaking, singing, and other forms of communication
Aids in sense of smell

4. Divisions of the Respiratory System (15-1)
Can be divided based on anatomical structures into:
Upper respiratory system
Includes nose, nasal cavity, paranasal sinuses, and pharynx
Structures filter, warm, and humidify incoming air
Lower respiratory system
Includes larynx, trachea, bronchi, and lungs

5. Figure 15-1 The Structures of the Respiratory System.
Upper Respiratory System
Nose
Nasal cavity
Sinuses
Tongue
Pharynx
Esophagus
Lower Respiratory System
Clavicle
Larynx
Trachea
Bronchus
Bronchioles
Smallest
bronchioles
Ribs
Right
lung
Left
lung
Alveoli
Diaphragm

6. Functional Zones of the Respiratory Tract (15-1)
Respiratory tract refers to passageways carrying air to and from exchange surfaces in lungs
Divided into two portions
Conducting portion
From nasal cavity to larger bronchioles
Filters, warms, and humidifies air
Respiratory portion
Small bronchioles and alveoli
Where gas exchange occurs

7. Conducting Portion of the Respiratory Tract (15-1)
Epithelium lining passageway is respiratory mucosa
Ciliated columnar epithelium with many mucous cells
Underlying lamina propria supports epithelium
Mucus coats exposed surfaces of respiratory tract
Cilia sweep mucus and trapped debris toward pharynx
Process called the mucus, or mucocilary, escalator
Debris and microorganisms swallowed and destroyed by acids and enzymes in stomach

8. Figure 15-2 The Respiratory Mucosa.
Movement
of mucus
to pharynx
Ciliated columnar
epithelial cell
Mucous cell
Stem cell
Debris
Mucous
gland
Mucus layer
Lamina propria
Superficial view
SEM × 1647 b
A surface view of the epithelium. The cilia of
the epithelial cells form a dense layer that
resembles a shag carpet. The movement of
these cilia propels mucus across the
epithelial surface. a
A diagrammatic view of the respiratory
epithelium of the trachea. The arrow
indicates the direction of mucus
transport inferior to the pharynx.

9. The Nose (15-2) Air enters through external nares, or nostrils
Nostrils open into nasal cavity
Nasal vestibule is space enclosed by flexible tissues of nose
Nasal septum divides cavity into right and left sides
Hard palate forms floor of nasal cavity
Soft palate extends behind hard palate and lies under nasopharynx
Nasal conchae project from lateral walls
Help warm and humidify incoming air by increasing turbulence of airflow
Internal nares mark the border between nasal cavity and nasopharynx

10. The Pharynx (15-2) Also called the throat
Chamber shared by respiratory and digestive systems
Extends between internal nares and entrances to larynx and esophagus

11. Three Subdivisions of the Pharynx (15-2)
​Nasopharynx – from internal nares to posterior edge of soft palate
Lined by ciliated respiratory epithelium
Contains pharyngeal tonsil and entrances to auditory tubes
​Oropharynx – from soft palate to base of tongue
Lined by stratified squamous epithelium
Contains the palatine tonsils
​Laryngopharynx – from base of tongue at level of hyoid bone to entrance of esophagus

12. Figure 15-3 The Nose, Nasal Cavity, and Pharynx.
Frontal sinus
Nasal Conchae
Nasal cavity
Superior
Middle
Internal nares
Inferior
Entrance to auditory tube
Pharyngeal tonsil
Nasal vestibule
Pharynx
External nares
Hard palate
Nasopharynx
Oral cavity
Oropharynx
Laryngopharynx
Tongue
Soft palate
Palatine tonsil
Mandible
Epiglottis
Lingual tonsil
Hyoid bone
Glottis
Thyroid cartilage
Cricoid cartilage
Trachea
Esophagus
Thyroid gland

13. The Larynx (15-2)
Tube that surrounds and protects the glottis, or “voice box”
Air enters the larynx through narrow opening of the glottis
Larynx made of nine cartilages stabilized by ligaments and skeletal muscles
Three largest cartilages are: epiglottis, thyroid cartilage, cricoid cartilage
Three pairs of smaller cartilages include: arytenoid, corniculate, cuneiform cartilages

14. Large Cartilages of the Larynx (15-2)
Epiglottis
Projects superior to glottis
Covers glottis during swallowing
Prevents entry of liquids and food into respiratory tract
Thyroid cartilage
Forms anterior and lateral surfaces of larynx
Ridge on anterior surface is “Adam’s apple”
Cricoid cartilage
Ring of cartilage just inferior to thyroid cartilage

15. Figure 15-4a-b The Anatomy of the Larynx and Vocal Cords.
Epiglottis
Hyoid bone
Ligament of
false vocal cord
Extrinsic
(thyrohyoid)
ligament
Corniculate cartilage
Elastic ligament
of true vocal cord
Thyroid
cartilage
Larynx
Arytenoid cartilages
Ligament
Cricoid cartilage
Ligament
Tracheal cartilages
Trachea a
Anterior view. b
Posterior view.

16. Vocal Cord Structure (15-2)
Two pairs of ligaments extending across the larynx
False vocal cords are the upper pair of ligaments
Inelastic
Help prevent foreign objects from entering glottis
Protect lower pair of ligaments
True vocal cords are the lower pair of ligaments
Elastic
Connect thyroid and arytenoid cartilages
Involved in sound production
Glottis is made up of true vocal cords and space between them

17. Figure 15-4c-e The Anatomy of the Larynx and Vocal Cords.
POSTERIOR
Corniculate cartilage
Corniculate cartilage
Glottis
(open)
Glottis
(closed)
Cuneiform cartilage
Cuneiform cartilage
False vocal cord
Glottis (open)
True vocal cord
False vocal cord
Epiglottis
True vocal cord
Root of tongue
Epiglottis
Root of tongue
ANTERIOR e
This photograph is a representative
laryngoscopic view. For this view the
camera is positioned within the oro-
pharynx, just superior to the larynx. c
Glottis in the open position. d
Glottis in the closed position.

18. The Trachea (15-2) Tough, flexible tube
Runs from cricoid cartilage to branches of primary bronchi
Walls supported by 15–20 C-shaped tracheal cartilages
Open parts of cartilages
Face posteriorly, toward esophagus
Allow passage of food along esophagus
Are connected by elastic ligament and trachealis muscle
Muscle under ANS control
Sympathetic stimulation dilates trachea

19. Figure 15-5 The Anatomy of the Trachea.
Hyoid bone
Larynx
Esophagus
Tracheal ligament
Trachealis muscle
(smooth muscle)
Respiratory
epithelium
Trachea
Tracheal cartilage
Tracheal
cartilage
Mucous gland
Primary bronchi
Secondary bronchi b
A cross-sectional view of the trachea and esophagus
RIGHT LUNG
LEFT LUNG a
A diagrammatic anterior view showing the plane of section for part (b)

20. The Bronchi (15-2) Trachea branches into two bronchi:
Right primary bronchus
Supplies right lung
Larger and at steeper angle
Creates more likely pathway for foreign objects
Left primary bronchus
Supplies left lung

21. The Bronchial Tree (15-2) Formed by primary bronchi and their branches
Secondary bronchi
First branches off primary bronchi
Enter lung lobes
Two in left lung, three in right lung
Tertiary bronchi
Branch off secondary bronchi
9–10 in each lung
Supply bronchopulmonary segment

22. Bronchioles (15-2) As proceed farther along bronchial tree: Bronchiole
Diameter decreases
Percentage of cartilage decreases
Bronchiole
Lung passageway when cartilage has disappeared
Walls dominated by smooth muscle
Sympathetic activation relaxes muscle, causing bronchodilation
Parasympathetic activation contracts muscle, causing bronchoconstriction

23. Figure 15-6a The Bronchial Tree and a Lobule of the Lung.
Trachea
Cartilage plates
Left primary
bronchus
Visceral pleura a
The branching pattern of bronchi
and bronchioles in the left lung,
simplified
Secondary
bronchus
Tertiary bronchi
Smaller
bronchi
Bronchioles
Terminal
bronchiole
Alveoli in a
pulmonary
lobule
Respiratory
bronchiole
Bronchopulmonary
segment

24. Terminal to Respiratory Bronchioles (15-3)
Terminal bronchioles are the finest conducting passageways
Average 0.3–0.5 mm in diameter
Each supplies one pulmonary lobule
Segment of lung tissue bound by connective tissue partitions
Supplied by a bronchiole, pulmonary arteriole, and venule
Terminal bronchioles branch into respiratory bronchioles
May have some gas exchange ability
Lead into alveolar ducts

25. Alveolar Ducts and Alveoli (15-3)
Alveolar ducts end at alveolar sacs
Chambers that connect to multiple individual alveoli
Each lung contains about 150 million alveoli
Give lung spongy, airy appearance
Vastly increase surface area
Total surface area of both lungs together is ~140 m2
Allow for extensive, rapid gas diffusion to meet metabolic needs

26. Figure 15-7a-b Alveolar Organization.
Alveoli
Respiratory bronchiole
Respiratory
bronchiole
Smooth muscle
Capillaries
Bands of
elastic fibers
Alveolar duct
Alveolar
sac
Alveolar
sac
Alveolarduct
Arteriole
Alveolus a
The basic structure of the distal end of a
single lobule. Note that multiple alveoli open
off a single alveolar duct, and that a network
of capillaries, supported by elastic fibers,
surrounds each alveolus.
Histology of the lung
LM × 14 b
Low-power micrograph of lung tissue.

27. Structure of Alveoli (15-3)
Primary cells are type I pneumocytes
Unusually thin simple squamous epithelium
Roaming alveolar macrophages
Patrol epithelium, engulfing any particles
Type II pneumocytes
Produce surfactant
Helps keep alveoli open by reducing surface tension
Lack of surfactant triggers respiratory distress syndrome

28. The Respiratory Membrane (15-3)
Where diffusion of gases takes place
Can be as thin as 0.1 µm
Averages 0.5 µm
Three layers
​Alveolar epithelium – squamous epithelial cells lining the alveoli
​Capillary endothelium – of adjacent capillary
​Fused basement membranes between alveolar and endothelial cells

29. Figure 15-7c-d Alveolar Organization.
Type II
pneumocyte
Type I pneumocyte
Alveolar
macrophage
Red blood cell
Elastic fibers
Capillary lumen
Capillary
endothelium
Nucleus of
endothelial cell
0.5 µm
Fused
basement
membrane
Alveolar
epithelium
Surfactant
Alveolar macrophage
Capillary
Alveolar air space d
The respiratory membrane, which
consists of an alveolar epithelial cell,
a capillary endothelial cell, and their
fused basement membranes.
Endothelial
cell of capillary c
A diagrammatic view of alveolar structure. A single capillary may be
involved in gas exchange with several alveoli simultaneously.

30. The Lungs (15-3) Divided into lobes, separated by deep fissures
Left lung has two lobes: superior and inferior
Right lung has three lobes: superior, middle, and inferior
Costal surface follows inner contours of rib cage
Mediastinal surface of left lung has cardiac notch
Provides space for pericardial cavity

31. Figure 15-8 The Gross Anatomy of the Lungs.
Apex
Superior lobe
Superior lobe
(costal surface)
Right lung
Left lung
Middle lobe
Cardiac notch (in
mediastinal surface)
Inferior lobe
Inferior lobe
Base
Anterior view

32. The Pleural Cavities (15-3)
Surround each lung within thoracic cavity
Pleura is serous membrane of pleural cavity
Visceral pleura covers outer surface of lungs
Parietal pleura lines inside of chest wall and diaphragm
Pleural layers secrete pleural fluid, reducing friction
Pleural cavity is potential space between the two layers
Parietal and visceral layers usually in close contact

33. Figure 15-9 Anatomical Relationships in the Thoracic Cavity.
Parietal pleura
Mediastinum
Right pleural cavity
Visceral pleura
Right Lung
Left Lung
Pericardial cavity
Heart
Superior view

34. External and Internal Respiration (15-4)
Respiration includes two integrated processes
​External respiration
Exchange of oxygen and carbon dioxide between body fluids and external environment
​Internal respiration
Absorption of oxygen and release of carbon dioxide by cells of the body

35. External Respiration (15-4)
Includes three steps
​Pulmonary ventilation, or breathing
Physical movement of air into and out of lungs
​Gas diffusion across respiratory membrane and across capillary walls between blood and body tissues
​Transport of O2 and CO2 in blood

36. Inadequate Oxygen Concentrations (15-4)
Hypoxia
Low tissue oxygen
Metabolic activities become limited
Anoxia
Supply of oxygen cut off completely
Cells die off quickly
Damage from strokes or heart attacks are a result of anoxia

37. Pulmonary Ventilation (15-5)
The physical movement of air into and out of the respiratory tract
Primary function to maintain alveolar ventilation
Movement of air into and out of alveoli
Prevents buildup of carbon dioxide
Ensures continuous supply of oxygen

38. Pressure and Airflow into Lungs (15-5)
Air moves down pressure gradient
In closed, flexible container (lung), air pressure is altered by changing the volume of container
Increase in volume decreases air pressure
Decrease in volume increases air pressure
Volume of lung depends on volume of thoracic cavity

39. Changes in Thoracic Volumes (15-5)
Diaphragm forms floor of thoracic cavity
Relaxed diaphragm is dome-shaped
Pushes up into thorax, compressing lungs
Contraction pulls it downward, increasing volume of thoracic cavity, expanding lungs
Rib cage
Elevation increases volume of thoracic cavity
External intercostal muscles and accessory muscles
Relaxation decreases volume of thoracic cavity
Internal intercostals and other accessory muscles

40. Figure 15-10a Pulmonary Ventilation
Ribs and
sternum
elevate
As the diaphragm is
depressed or the ribs
are elevated, the
volume of the thoracic
cavity increases and
air moves into the
lungs. The outward
movement of the ribs
as they are elevated
resembles the outward swing of a raised bucket handle.
Diaphragm
contracts

41. Volume Change Causes Pressure Gradient (15-5)
Inhaling
Increase in volume, pressure inside (Pi) decreases
Pi lower than pressure outside (Po), air moves in
Exhaling
Decrease in volume, Pi increases
Pi higher than Po, air moves out
At end-inhalation and end-exhalation, Pi = Po

42. Figure 15-10b Pulmonary Ventilation
AT REST
Mediastinum
Pleural cavity
Right
lung
Left
lung
Diaphragm
Poutside = Pinside
When the rib cage and
diaphragm are at rest, the
pressures inside and outside
the lungs are equal, and no
air movement occurs.

43. Figure 15-10c Pulmonary Ventilation
INHALATION
Accessory Respiratory
Muscles
Sternocleidomastoid
muscle
Scalene muscles
Pectoralis minor muscle
Serratus anterior muscle
Primary Respiratory
Muscles
External intercostal
muscles
Diaphragm
Elevation of the rib cage
and contraction of the
diaphragm increase the
volume of the thoracic
cavity. Pressure within
the lungs decreases,
and air flows in.
Thoracic cavity volume increases
Poutside > Pinside

44. Figure 15-10d Pulmonary Ventilation
EXHALATION
Accessory Respiratory
Muscles
Transversus thoracis muscle
Internal intercostal muscles
Rectus abdominis
When the rib cage returns
to its original position and
the diaphragm relaxes, the
volume of the thoracic
cavity decreases. Pressure
within the lungs increases,
and air moves out.
Thoracic cavity volume decreases
Poutside < Pinside

45. Compliance (15-5) Compliance is ease with which lungs expand
Greater compliance means easier to fill and empty lungs
Lower compliance requires greater force to fill and empty lungs
Dramatically increases energy needed for breathing
Compliance can be affected by these factors
Loss of supporting tissues due to alveolar damage increases compliance (as in emphysema)
Decrease in surfactant decreases compliance (as in respiratory distress syndrome)
Limits on movements of thoracic cage (as with arthritis) decreases compliance

46. Modes of Breathing (15-5) Quiet breathing Forced breathing
Inhalation involves only primary muscles of inspiration: diaphragm and external intercostals
Diaphragm accounts for 75 percent of air movement
Exhalation is passive
Forced breathing
Inhalation involves both primary and accessory muscles
Exhalation uses internal intercostals and abdominals

47. Respiratory Cycle and Rate (15-5)
A single breath of inhalation (inspiration) and exhalation (expiration)
Respiratory rate
Number of breaths per minute
Normal adult rate 12–18 breaths per minute

48. Lung Volumes and Capacities (15-5)
Tidal volume (VT)
Amount of air moved into or out of lungs in single respiratory cycle during quiet breathing
Expiratory reserve volume (ERV)
Amount of air you can voluntarily expel at end of a normal “exhale”, or quiet respiratory cycle
Inspiratory reserve volume (IRV)
Amount of air that can be taken in above tidal volume
Vital capacity = VT + IRV + ERV
Maximum amount of air that can be moved into and out of lung in one respiratory cycle

49. Lung Volumes and Capacities cont. (15-5)
Residual volume
Amount of air remaining in lungs after maximal exhalation
Minimal volume
Amount of air remaining in lungs after lung collapse
Anatomic dead space
Amount of air in conducting passageways
Does not take part in gas exchange
Averages about 150 mL (when tidal volume is 500 mL)

50. Figure 15-11 Pulmonary Volumes and Capacities.
Pulmonary Volumes and Capacities (adult male)
6000
Gender Differences
Tidal volume
(VT = 500 mL)
Inspiratory
reserve
volume (IRV)
Inspiratory
capacity
Males
Females
IRV
3300
1900
Inspiratory
capacity
Vital
capacity
Volume (mL) VT
500
500
Vital
capacity
ERV
1000
700
Functional
residual
capacity
Residual volume
1200
1100
2700
Total lung
capacity
Total lung capacity
6000 mL
4200 mL
2200
Expiratory
reserve volume
(ERV)
Functional
residual
capacity
1200
Residual
volume
Minimal volume
(30–120 mL)
Time

51. Gas Exchange (15-6) Gas exchange depends on two factors
Partial pressure gradient of gases involved
Diffusion of molecules between gas and liquid

52. Partial Pressure of a Gas in a Mixture (15-6)
100 percent of atmospheric air is made up of:
78.6 percent nitrogen, 20.9 percent oxygen, 0.04 percent carbon dioxide
Remaining 0.5 percent is water vapor
At sea level atmospheric pressure is 760 mm Hg
Each gas in a mixture contributes a proportional pressure, a partial pressure (Pgas)
PO2 = 760 mm Hg × 20.9% = 159 mm Hg

53. Atmospheric vs. Alveolar Partial Pressures (15-6)
Air entering respiratory structures changes in character
Increase in water vapor and temperature
Alveolar air is mixture of atmospheric air and residual volume
Exhaled air is changed also
Mixes with air in conducting zone or dead space that never reached alveoli

54. Partial Pressures in Pulmonary Circuit (15-6)
Deoxygenated blood entering pulmonary arteries
PO2 = 40 mm Hg; PCO2 = 45 mm Hg
Alveolar air
PO2 = 100 mm Hg; PCO2 = 40 mm Hg
Gases move down partial pressure gradients
Oxygen moves from alveolar air to capillaries
Carbon dioxide moves from capillaries into alveolar air
Blood entering pulmonary veins mixes with low oxygen blood from capillaries around conducting zone
Blood entering left atrium has PO2 = 95 mm Hg

55. External Respiration PO2 = 40 PCO2 = 45 PO2 = 100 PCO2 = 40 PO2 = 100
Figure 15-12a An Overview of Respiratory Processes and Partial Pressures in Respiration. a
External Respiration
Alveolus
PO2 = 40
PCO2 = 45
Respiratory
membrane
Systemic
circuit
Pulmonary
circuit
PO2 = 100
PCO2 = 40
Diffusion
Pulmonary
capillary
PO2 = 100
PCO2 = 40
Systemic
circuit

56. Partial Pressures in Systemic Circuit (15-6)
Oxygenated blood entering systemic arteries
PO2 = 95 mm Hg; PCO2 = 40 mm Hg
Interstitial fluid
PO2 = 40 mm Hg; PCO2 = 45 mm Hg
Gases move down partial pressure gradients
Oxygen moves from plasma to tissues
Carbon dioxide moves from tissues to plasma
Deoxygenated blood returning to right atrium

57. Figure 15-12b An Overview of Respiratory Processes and Partial Pressures in Respiration.
Systemic
circuit
Pulmonary
circuit b
Internal Respiration
Interstitial fluid
Systemic
circuit
PO2 = 95
PCO2 = 40
PO2 = 40
PCO2 = 45
Diffusion
PO2 = 40
Systemic
capillary
PCO2 = 45

58. Gas Transport in Blood (15-7)
O2 and CO2 have limited ability to dissolve in plasma
Tissues need more O2, and generate more CO2, than can be dissolved
Red blood cells (RBCs) can carry both gases on hemoglobin
CO2 can chemically convert to soluble compound
As gases are removed from plasma, more diffuse in
All reactions are temporary and completely reversible

59. Oxygen Transport (15-7)
1.5 percent of O2 transported in solution in plasma
Remainder binds to central iron in heme unit of hemoglobin (Hb) molecule
Reversible reaction
Rate of release of O2 determined by:
PO2 of tissues, pH, and temperature
Low PO2, low pH, and high temp increases O2 release

60. Carbon Dioxide Transport (15-7)
CO2 generated as product of aerobic cell metabolism
Transported in three ways
7 percent of CO2 is dissolved in plasma
23 percent is in RBC bound to Hb
Bound to globin portion of Hb
Forms carbaminohemoglobin
70 percent is transported as bicarbonate ions

61. Carbon Dioxide Transport as Bicarbonate (15-7)
Overall reaction is:
This reaction occurs in RBCs
Bicarbonate (HCO3–) diffuses out of RBC in exchange for chloride ion (Cl–)
Known as the chloride shift
Reactions are rapid and reversed in pulmonary capillaries

62. Figure 15-13 Carbon Dioxide Transport in Blood.
CO2 diffuses
into the
bloodstream
7% remains
dissolved in
plasma (as CO2)
93% diffuses
into RBCs
23% binds to Hb,
forming
carbaminohemoglobin,
Hb•CO2
70% converted to
H2CO3 (carbonic
acid) by the enzyme
carbonic anhydrase
RBC
H2CO3 dissociates
into H+ and HCO3–
H+ removed
by buffers,
especially Hb H+
Cl–
HCO3– moves
out of RBC in
exchange for
CI– (chloride
shift)
PLASMA

63. Figure 15-14 A Summary of Gas Transport and Exchange.
Slide 4
O2 pickup
(PO2 = 100, PCO2 = 40)
O2 delivery
(PO2 = 95, PCO2 = 40)
Pulmonary
capillary
Systemic
capillary
Plasma
Red blood cell
Red blood cell
Cells in
peripheral
tissues
Alveolar
air space
Alveolar
air space
Chloride
shift
Cells in
peripheral
tissues
Pulmonary
capillary
Systemic
capillary
CO2 delivery
(PO2 = 40, PCO2 = 45)
CO2 pickup
(PO2 = 40, PCO2 = 45)

64. Maintaining O2 and CO2 Levels (15-8)
Cells are continually absorbing oxygen and generating carbon dioxide
Rates of absorption and generation need to be balanced with delivery and removal
Two homeostatic processes maintain equilibrium
Changes in blood flow and oxygen delivery under local control
Changes in depth and rate of respiration under control of brain’s respiratory centers

65. Local Control of Respiration (15-8)
In the tissues:
Increased activity results in:
Decrease in tissue PO2 and increase in PCO2
Result is more rapid diffusion of O2 into cells, CO2 out of cells
In the lungs:
When alveolar capillary PO2 is low:
Precapillary sphincters constrict, shunting blood to high PO2 pulmonary lobules
When air in bronchioles has high PCO2 bronchioles dilate; when low they constrict
Causes airflow to be directed to lobules with high PCO2