PowerLecture: Chapter 11

1
PowerLectureChapter 11

• The Respiratory System

2
Learning Objectives

• Understand how body processes generate a need to
  acquire oxygen and dispose of carbon dioxide.
• Describe the gradients that the respiratory gases
  follow in their routes into and out of the body.
• Understand how the human respiratory system
  functions and how it works in coordination with
  other systems of the body.

3
Learning Objectives (contd)

• Explain the controls over the breathing
  processes.
• List some of the things that can go wrong with
  the respiratory system and explain the mechanisms
  through which the breakdown in the system occurs.

4
Impacts/Issues

• Down in Smoke

5
Down in Smoke

• Smoking poses a threat to human health and
  survival.
• Cilia that line the respiratory
• airways and normally sweep
• away pollutants and microbes
• are immobilized for hours.
• Smoke kills white blood cells
• that defend the respiratory tract.
• Smoking puts the body at
• increased risk for cancer, high blood pressure,
  and elevated levels of bad cholesterol.

6
Down in Smoke

• The respiratory system functions to bring oxygen
  into, and carbon dioxide out of, the body.

Fig. 11.14a, p. 206
7
How Would You Vote?

• To conduct an instant in-class survey using a
  classroom response system, access JoinIn Clicker
  Content from the PowerLecture main menu.
• As tobacco use by its citizens declines, should
  the United States encourage international efforts
  to reduce tobacco use?
• a. Yes, tobacco use is costly both in terms of
  personal health and societal financial burden.
  The United States should encourage international
  efforts to reduce tobacco use.
• b. No, the United States should not encourage
  international efforts to reduce tobacco use.
  Tobacco use, though deleterious to health, is a
  personal choice that individuals have a right to
  make on their own.

8
Section 1

• The Respiratory SystemBuilt for Gas Exchange

9
The Respiratory System Built for Gas Exchange

• Airways are pathways for oxygen and carbon
  dioxide.
• The respiratory system brings in oxygen that each
  body cell requires and takes away carbon dioxide
  that every cell generates.
• Through the nasal cavities of the nose, air
  enters and leaves the respiratory system the
  nasal cavities are separated by a septum of
  cartilage and bone.

10
The Respiratory System Built for Gas Exchange

• Hair and ciliated epithelium filter dust and
  particles from the air.
• Blood vessels warm the air and mucus moistens it.
• The paranasal sinuses lie just above the cavities
  and are linked to them by channels.

Figure 11.2
11
The Respiratory System Built for Gas Exchange

• Air moves via this route nasal cavities gtgtgt
  pharynx gtgtgt larynx gtgtgt vocal cords (the gap
  between the cords is the glottis) gtgtgt trachea gtgtgt
  bronchi (one bronchus goes to each lung).
• The trachea leads from the larynx downward to
  branch into two bronchi, which are lined with
  cilia and mucus to trap bacteria and particles.
• The vocal cords at the entrance of the larynx
  vibrate when air passes through the glottis,
  allowing us to make sounds during swallowing,
  the glottis is closed to prevent choking.

12
vocal cords
glottis (open)
glottis (closed)
epiglottis
tongues base
Fig. 11.3, p. 197
13
The Respiratory System Built for Gas Exchange

• Lungs are elastic and provide a large surface
  area for gas exchange.
• Human lungs are a pair of organs housed in the
  rib cage above the diaphragm the two lungs are
  separated by the heart.
• Each lung is enclosed by a pair of thin membranes
  called pleurae (singular pleura) the pleural
  membrane is folded in a manner that forms a
  pleural sac leaving an intrapleural space filled
  with a lubricating intrapleural fluid.

14
The Respiratory System Built for Gas Exchange

• Inside the lungs, bronchi narrow to form
  bronchioles ending in respiratory bronchioles.
• Tiny clustered sacs called alveoli (singular
  alveolus) bulge out from the walls of the
  respiratory bronchioles.
• Together the alveoli provide a tremendous surface
  area for gaseous exchange, with the blood located
  in the dense capillary network surrounding each
  alveolar sac.

15
Fig. 11.1bc, p. 196
bronchiole
alveolar sac (sectioned)
alveolar sac
alveolar duct
alveoli
pulmonary capillary
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Nasal Cavity
Oral Cavity (mouth)
Pharynx (throat)
Epiglottis
Larynx (voice box)
Pleural Membrane
Trachea (windpipe)
Intercostal Muscles
Lung (one of a pair)
Bronchial Tree
Diaphragm
alveolar sac (sectioned)
bronchiole
alveolar sac
alveolar duct
alveoli
pulmonary capillary
Fig. 11.1, p. 196
17
Section 2

• Respiration Gas Exchange

18
Respiration Gas Exchange

• Respiration is the overall exchange of inhaled
  oxygen from the outside air for exhaled carbon
  dioxide waste.
• This exchange occurs in the alveoli afterward,
  the cardiovascular system is responsible for
  moving gases in the body.

19
In-text Fig., p. 198
O2
O2
CO2
CO2
Cellular respiration in mitochondria
Whole body respiration
20
Fig. 11-4, p. 198
food, water intake
oxygen intake
elimination of carbon dioxide
RESPIRATORY SYSTEM
DIGESTIVE SYSTEM
nutrients, water, salts
carbon dioxide
oxygen
CARDIOVASCULAR SYSTEM
URINARY SYSTEM
water, solutes
elimination of excess water, salts, wastes
elimination of food residues
rapid transport to and from all living cells
21
Section 3

• The Rules of Gas Exchange

22
The Rules of Gas Exchange

• Respiratory systems rely on the diffusion of
  gases down pressure gradients.
• Air is 78 nitrogen, 21 oxygen, 0.04 carbon
  dioxide, and 0.96 other gases.
• Partial pressures for each gas in the atmosphere
  can be calculated for example, oxygens is 160
  mm Hg.
• Oxygen and carbon dioxide diffuse down pressure
  gradients from areas of high partial pressure to
  areas of low partial pressure.

23
Fig. 11.5, p. 198
Total atmospheric pressure 760 mm Hg
78 N2 Partial pressure of N2 600 mm Hg
21 O2 Partial pressure of O2 160 mm Hg
760 mm Hg
1 CO2, other gases
24
The Rules of Gas Exchange

• Gases enter and leave the body by diffusing
  across thin, moist respiratory surfaces of
  epithelium the speed and extent of diffusion
  depends on the surface area present and on the
  partial pressure gradient.

25
The Rules of Gas Exchange

• When hemoglobin binds oxygen, it helps maintain
  the pressure gradient.
• Hemoglobin is the main transport protein.
• Each protein binds four molecules of oxygen in
  the lungs (high oxygen concentration) and
  releases them in the tissues where oxygen is low
  by carrying oxygen away from the lungs, the
  gradient is maintained.

26
The Rules of Gas Exchange

• Gas exchange rules change when oxygen is
  scarce.
• Hypoxia occurs when tissues do not receive enough
  oxygen at high altitudes the partial pressure of
  oxygen is lower than at sea level, so that
  hyperventilation may occur.

Figure 11.6a
27
The Rules of Gas Exchange

• Underwater, divers must breathe pressurized air
  from tanks and avoid nitrogen narcosis, where
  nitrogen dissolves into the body, including the
  brain divers must also ascend to the surface
  slowly to prevent nitrogen bubbles in the
  bloodthe bends or decompression sickness.

Figure 11.6b
28
Section 4

• Breathing
• Air In, Air Out

29
Breathing

• When you breathe, air pressure gradients reverse
  in a cycle.
• The respiratory cycle is the continuous in/out
  ventilation of the lungs and has two phases
• Inspiration (inhalation) draws breath into the
• airways.
• Expiration (exhalation) moves a breath out of
• the airways.

30
Breathing

• During the cycle, the volume of the chest cavity
  increases, then decreases, and the pressure
  gradients between the lungs and outside air
  reverse.
• This works because the air in the airways is the
• same pressure as the outside atmosphere.
• Pressure in the alveoli (intrapulmonary pressure)
  
• is also the same as the outside air.

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INWARD BULKFLOW OF AIR
OUTWARD BULKFLOW OF AIR
Exhalation Diaphragm and external intercostal
muscles return to the resting positions. Rib cage
moves down. Lungs recoil passively.
Inhalation Diaphragm contracts and moves down.
The external intercostal muscles contract and
lift the rib cage upward and outward. The lung
volume expands.
Fig. 11.7, p. 200
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Breathing

• The basic respiratory cycle.
• To inhale, the diaphragm contracts and flattens,
  muscles lift the rib cage upward and outward,
  the chest cavity volume increases, internal
  pressure decreases, air rushes in.
• To exhale, the actions listed above are reversed
  the elastic lung tissue recoils passively and air
  flows out of the lungs.
• Active exhalation involves contraction of the
  abdominal muscles to push the diaphragm upward,
  forcing more air out.

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Breathing

• Another pressure gradient aids the process.
• The lungs are stretched to fill the thoracic
  cavity by a slight difference between the
  intrapulmonary pressure (higher) and the
  intrapleural pressure (lower).
• In a collapsed lung (pneumothorax), air enters
  the pleural cavity, disrupting the normal
  expansion and contraction of the lungs.

34
Breathing

• How much air is in a breath?
• About 500 ml of air (tidal volume) enters and
  leaves the lungs with each breath.
• A human can forcibly inhale 3,100 ml of air
  (inspiratory reserve volume) and forcibly exhale
  1,200 ml (expiratory reserve volume).
• The maximum volume that can be moved in and out
  is called the vital capacity (4,800 ml for males,
  3,800 ml for females).

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Fig. 11.8, p. 201
6,000
5,000
inspiratory reserve volume
4,000
tidal volume
vital capacity
total lung capacity
Lung volume (milliliters)
3,000
expiratory reserve volume
2,000
1,000
residualvolume
0
time
36
Breathing

• A residual volume of about 1,200 ml remains in
  the lungs and cannot be forced out.
• Sometimes food enters the trachea rather than the
  esophagus it can be forced out by the Heimlich
  maneuver, which forces the diaphragm to elevate,
  pushing air into the trachea to dislodge the
  obstruction.

37
Fig. 11.9a, p. 201
a Place a fist just above the choking persons
navel, with the flat of your thumb against the
abdomen.
38
Fig. 11.9b, p. 201
b Cover the fist with your other hand. Thrust
both fists up and in with enough force to lift
the person off his or her feet.
39
Section 5

• How Gases Are Exchanged and Transported

40
How Gases Are Exchanged and Transported

• Ventilation moves gases into and out of the
  lungs it is different from respiration, which is
  the actual exchange of gases between the blood
  and cells.
• In external respiration, oxygen moves from the
  alveoli to the blood carbon dioxide moves in the
  opposite direction.
• In internal respiration, oxygen moves from the
  blood into tissues and vice versa for carbon
  dioxide.

41
How Gases Are Exchanged and Transported

• Alveoli are masters of gas exchange.
• Each alveolus is only a single layer of
  epithelial cells surrounded by a thin basement
  membrane and a net of lung capillaries, also with
  thin basement membranes.
• Between the two basement membranes is a film of
  fluid.
• Together the system forms the respiratory
  membrane.
• The partial pressure gradients are sufficient to
  move oxygen in and carbon dioxide out of the
  blood, passively.

42
How Gases Are Exchanged and Transported

• Pulmonary surfactant is a secretion produced by
  the alveoli that reduces the surface tension of
  the film to prevent collapse of the alveoli
  infant respiratory distress syndrome occurs in
  premature babies who lack the ability to make the
  surfactant.

43
Fig. 11.10, p. 202
alveolar epithelium
respiratory membrane
capillary endothelium
pore for air flow between adjoining alveoli
fused- together basement membranes of both
epithelia
space inside alveolus
a Surface view of capillaries associated with
alveoli
b Cutaway view of one alveolus, showing the
respiratory membrane
c Closer view of the respiratory membranes
structure
red blood cell
44
Fig. 11.10a, p. 202
pore for air flow between adjoining alveoli
a. Surface view of capillaries associated with
alveoli
45
Fig. 11.10b, p. 202
pore for airflow between adjoining alveoli
respiratory membrane
(see next slide)
space inside alveolus
red blood cell
b. Cutaway view of one alveolus, showing the
respiratory membrane
46
Fig. 11.10c, p. 202
alveolar epithelium
capillary endothelium
fused-together basement membranes of both
epithelia
c. Closer view of the respiratory membranes
structure
47
How Gases Are Exchanged and Transported

• Hemoglobin is the oxygen carrier.
• Blood cannot carry sufficient oxygen and carbon
  dioxide in dissolved form as the body requires
  hemoglobin helps enhance its capacity to carry
  gases by transporting oxygen.
• Oxygen diffuses down a pressure gradient into the
  blood plasma gtgtgt red blood cells gtgtgt hemoglobin
  where it binds at a ratio of four oxygens to one
  hemoglobin to form oxyhemoglobin.
• Hemoglobin gives up its oxygen in tissues where
  partial pressure of oxygen is low, blood is
  warmer, and pH is lower all three conditions
  occur in tissues with high metabolism.

48
Fig. 11.11, p. 203
O2 160
O2 120
MOISTEXHALED AIR
DRYINHALED AIR
CO2 0.3
CO2 27
alveolar sacs
CO2 40
O2 104
pulmonary arteries
pulmonary veins
O2 40
O2 100
CO2 45
CO2 40
start of systematic veins
start of systematic capillaries
O2 100
O2 40
CO2 40
CO2 45
cells of body tissue
O2 less than 40
CO2 more than 45
49
How Gases Are Exchanged and Transported

• When tissues are chronically low in oxygen, red
  blood cells produce DPG (2,3-diphosphoglycerate),
  which decreases the affinity of hemoglobin for
  oxygen, allowing more oxygen to be released to
  the tissues.
• Hemoglobin and blood plasma carry carbon dioxide.
• Because carbon dioxide concentration is higher in
  the body tissues rather than in blood, it
  diffuses into the blood capillaries.

50
How Gases Are Exchanged and Transported

• Seven percent remains dissolved in plasma, 23
  binds with hemoglobin (forming carbaminohemoglobin
  ) and 70 is in bicarbonate form.
• Bicarbonate and carbonic acid formation is
  enhanced by carbonic anhydrase, an enzyme located
  in the red blood cells.
• Reactions that make bicarbonate are reversed in
  the alveoli where the partial pressure of carbon
  dioxide is low.

51
Section 6

• Homeostasis Depends on Controls over Breathing

52
Homeostasis Depends on Controls Over Breathing

• A respiratory pacemaker controls the rhythm of
  breathing.
• Automatic mechanisms ensure a regular cycle of
  ventilation.
• Clustered nerve cells in the medulla coordinate
  the signals for the timing of exhalation and
  inhalation the pons fine tunes the rhythmic
  contractions.
• The nerve cells are linked to the diaphragm
  muscles and the muscles that move the rib cage
  during normal inhalation, nerve signals travel
  from the brain to the muscles causing them to
  contract and allowing the lungs to expand.

53
Homeostasis Depends on Controls Over Breathing

• Normal exhalation follows relaxation of muscles
  and elastic recoil of the lungs.
• When breathing is deep and rapid, stretch
  receptors in the airways send signals to the
  brain control centers, which respond by
  inhibiting contraction of the diaphragm and rib
  muscles, forcing you to exhale.

54
Fig. 11.12, p. 204
neurons (pacemaker for respiration)
brain stem (pons and medulla)
vagus nerve
motor pathways via spinal cord
phrenic nerve to diaphragm
intercostal nerves to rib muscles
stretch receptors in alveoli of lungs
diaphragm
55
Homeostasis Depends on Controls Over Breathing

• CO2 is the trigger for controls over the rate and
  depth of breathing.
• The nervous system is more sensitive to levels of
  carbon dioxide and uses this gas to regulate the
  rate and depth of breathing.
• Sensory receptors in the medulla detect hydrogen
  ions produced when dissolved carbon dioxide
  leaves the blood and enters the cerebrospinal
  fluid bathing the medulla.
• The drop in pH in the cerebrospinal fluid
  triggers more rapid and deeper breathing to
  reduce the levels of carbon dioxide in the blood.

56
Homeostasis Depends on Controls Over Breathing

• Changes in the levels of carbon dioxide, oxygen,
  and blood pH are also detected by carotid bodies,
  located near the carotid arteries, and aortic
  bodies, located near the aorta both receptors
  signal increases in ventilation rate to deliver
  more oxygen to tissues.

57
Fig. 11.13, p. 205
brain-stem (pons and medulla) receptors detect
decreases in pH of cerebrospinal fluid (due to
rising CO2 in blood)
carotid bodies (CO2, O2 receptors)
aortic bodies (O2 receptors)
heart
lungs
spinal cord
58
Homeostasis Depends on Controls Over Breathing

• Chemical controls in alveoli help match air flow
  to blood flow.
• When the rate of blood flow in the lungs is
  faster than the air flow, the bronchioles dilate
  to enhance the air flow and thus the rate of
  diffusion of the gases.
• When the air flow is too great relative to the
  blood flow, oxygen levels rise in the lungs and
  cause the blood vessels to dilate, increasing
  blood flow.

59
Homeostasis Depends on Controls Over Breathing

• Apnea is a condition in which breathing controls
  malfunction.
• Apnea is a brief interruption in the respiratory
  cycle breathing stops and then resumes
  spontaneously.
• Sleep apnea is a common problem of aging because
  the mechanisms for sensing changing oxygen and
  carbon dioxide levels gradually become less
  effective over the years.

60
Section 7

• Disorders of the Respiratory System

61
Disorders of the Respiratory System

• Tobacco is a major threat.
• Smoking has both immediate effects (for example,
  loss of cilia function) and long term effects,
  such as lung cancer.
• Even one cigarette can cause
• you damage as well as hurt those
• around you through secondhand
• smoke.
• A variety of pathogens can infect the respiratory
  system.

Figure 11.17
62
Fig. 11.14b, p. 206
63
Disorders of the Respiratory System

• Pneumonia occurs when inflammation in lung tissue
  and the buildup of fluids makes breathing
  difficult pneumonia can sometimes occur when
  infections that start in the nose and throat,
  such as from influenza, spread.
• Tuberculosis arises from infection by the
  bacterium Mycobacterium tuberculosis the disease
  destroys patches of lung tissue and can cause
  death if untreated.
• Histoplasmosis is caused by a fungus treatment
  is possible, but the infection can sometimes
  spread to the eyes, causing impairment or
  blindness.

64
Disorders of the Respiratory System

• Irritants cause other disorders.
• Bronchitis, caused by air pollution, cigarette
  smoke, or infection, leads to increased mucus
  secretions, interference with ciliary action, and
  eventual inflammation and possible scarring of
  the bronchial walls.

Figure 11.18
65
Fig. 11.18a, p. 210
66
Disorders of the Respiratory System

• If bronchitis progresses so that more of the
  bronchi become scarred and blocked with mucus,
  emphysema may result here alveoli also begin to
  break down, further eroding the ability to
  breathe.

67
Fig. 11.15, p. 207
68
Disorders of the Respiratory System

• Asthma occurs in response to various allergens
  smooth muscles in the bronchiole walls contract
  in spasms, mucus rushes in, and breathing becomes
  difficult. Steroid inhalers may be needed to
  relieve symptoms.

Figure 11.16