Why%20oxygen%20is%20import

1
Why oxygen is import Most animals satisfy their
energy requirement by oxidation of food, in the
processes forming carbon dioxide and
water Oxygen is most abundant element in the
earths crust (49.2) In atmosphere
Per liter water (150C, 1 atm) O2 20.95
7.22 ml CO2 0.03 1019.0 ml N2
78.09 16.9 ml Argon
0.93 Total 100
2
Vacuum
760 mm
Pressure exerted by atmospheric air above Earths
surface
Pressure at sea level
Mercury (Hg)
3
Oxygen and carbon dioxide in physical environment
Oxygen is added to atmosphere Photosynthesis
(dominant) Photodissociation of water
vapor Oxygen is removed from atmosphere Living
organism respiration Oxidizing of organic matter,
rocks, gases and fossil fuels
4

• "Global warming" is a real phenomenon Earth's
  temperature is increasing.
• True
• False

5
(No Transcript)
6
(No Transcript)
7
Fig. 11-2, p.464
8
(No Transcript)
9
Oxygen and carbon dioxide in physical environment
Solubility of oxygen decreases with increasing
water temperature and salinity Temperature
Fresh water Sea water ml O2/L water
ml O2/L water 0 10.29 7.97 10
8.02 6.35 15 7.22 5.79 20
6.57 5.31 30 5.57 4.46 Normoxic
water 100 saturated with oxygen Hypoxic water
contains less oxygen than normoxic water Anoxic
water contains no dissolved oxygen
10
(No Transcript)
11
(No Transcript)
12

• Transport O2 and CO2 in living systems
• Diffusion is common mechanism for transport both
  O2 and CO2 across the body surface
• To maximize the rate of gas transfer
• Large respiratory surface area
• Small diffusion distance

13
(No Transcript)
14
The lungs contain many branching airways which
collectively are known as the bronchial tree
bronchial tree
15

• The trachea and all the bronchi have supporting
  cartilage which keeps the airways open.
• Bronchioles lack cartilage and contain more
  smooth muscle in their walls than the bronchi,
  for airflow regulation
• The airways from the nasal cavity through the
  terminal bronchioles are called the conducting
  zone.
• The air is moistened, warmed, and filtered as it
  flows through these passageways.

16
(No Transcript)
17

• The pulmonary arteries carry blood which is low
  in oxygen from the heart to the lungs.
•  These blood vessels branch repeatedly,
  eventually forming dense networks of capillaries
  that completely surround each alveolus.
• oxygen and carbon dioxide are exchanged between
  the air in the alveoli and the blood in the
  pulmonary capillaries.
• Blood leaves the capillaries via the pulmonary
  veins, which transports the oxygenated blood out
  of the lungs and back to the heart.

18
Alveoli

• 300 million air sacs.
• Large surface area (60 80 m2).
• Each alveolus is 1 cell layer thick.
• Total air barrier is 2 cells across (0.5 mm).
• 3 types of cells
• Alveolar type I
• Structural cells.
• Alveolar type II
• Secrete surfactant.

19
Ventilation

• Mechanical process to move air in and out of the
  lungs.
• O2 of air is higher in the lungs than in the
  blood, O2 diffuses from air to the blood.
• C02 moves from the blood to the air by diffusing
  down its concentration gradient.
• Gas exchange occurs entirely by diffusion.
• Diffusion is rapid because of the large surface
  area and the small diffusion distance.

20
Three types of cells 1. simple epithelium
cells 2. alveolar macrophages 3.
surfactant-secreting cells
The wall of an alveolus is primarily composed
of simple epithelium, or Type I cells. Gas
exchange occurs easily across this very thin
epithelium. The alveolar macrophages, or dust
cells, creep along the inner surface of the
alveoli, removing debris and microbes. The
alveolus also contains scattered
surfactant-secreting, or Type II, cells.
21

• Water in the fluid creates a surface tension.
• Surface tension is due to the strong attraction
  between water molecules at the surface of a
  liquid, which draws the water molecules closer
  together.
• Surfactant, which is a mixture of phospholipids
  and lipoproteins, lowers the surface tension of
  the fluid by interfering with the attraction
  between the water molecules, preventing alveolar
  collapse.
• Without surfactant, alveoli would have to be
  completely reinflated between breaths, which
  would take an enormous amount of energy.

22
The wall of an alveolus and the wall of a
capillary form the respiratory membrane, where
gas exchange occurs.
23
(No Transcript)
24
Summary The lungs contain the bronchial tree,
the branching airways from the primary bronchi
through the terminal bronchioles. The
respiratory zone of the lungs is the region
containing alveoli, tiny thin-walled sacs where
gas exchange occurs. Oxygen and carbon dioxide
diffuse between the alveoli and the pulmonary
capillaries across the very thin respiratory
membrane.
25
Three main factors 1.The surface area and
structure of the respiratory membrane. 2.
Partial pressure gradients 3. Matching alveolar
airflow to pulmonary capillary blood flow
26
Atmosphere 760 mm Hg
Atmospheric pressure (the pressure exerted by the
weight of the gas in the atmosphere on objects on
the Earths surface760 mm Hg at sea level)
Airways (represents all airways collectively)
Thoracic wall (represents entire thoracic cage)
Intra-alveolar pressure (the pressure within the
alveoli760 mm Hg when equilibrated with
atmospheric pressure)
760 mm Hg
Pleural sac (space represents pleural cavity)
756 mm Hg
Lungs (represents all alveoli collectively)
Intrapleural pressure (the pressure within the
pleural sacthe pressure exerted outside the
lungs within the thoracic cavity, usually less
than atmospheric pressure at 756 mm Hg)
Fig. 11-17, p.480
27
760
Airways
Pleural cavity (greatly exaggerated)
Lung wall
Lungs (alveoli)
Thoracic wall
756
756
760
760
760
756
Transmural pressure gradient across lung wall
intra-alveolar pressure minus intrapleural
pressure
Transmural pressure gradient across thoracic wall
atmospheric pressure minus intrapleural
pressure
Numbers are mm Hg pressure.
Fig. 11-18, p.481
28
(No Transcript)
29
Accessory muscles of inspiration (contract
only during forceful inspiration)
Internal intercostal muscles
Sternocleidomastoid
Scalenus
Sternum
Ribs
Muscles of active expiration (contract
only during active expiration)
External intercostal muscles
Diaphragm
Major muscles of inspiration (contract
every inspiration relaxation causes
passive expiration)
Abdominal muscles
Fig. 11-20, p.482
30
External intercostal muscles (relaxed)
Elevated rib cage
Elevation of ribs causes sternum to move upward
and outward, which increases front-to-back
dimension of thoracic cavity
Contraction of external intercostal muscles
Sternum
Contraction of diaphragm
Diaphragm (relaxed)
Before inspiration
Inspiration
Lowering of diaphragm on contraction increases
vertical dimension of thoracic cavity
Contraction of external intercostal muscles
causes elevation of ribs, which increases
side-to-side dimension of thoracic cavity
(a)
Fig. 11-21a, p.483
31
Contraction of internal intercostal
muscles flattens ribs and sternum, further
reducing side-to-side and front-to-back
dimensions of thoracic cavity
Relaxation of external intercostal muscles
Contraction of internal intercostal muscles
Relaxation of diaphragm
Contraction of abdominal muscles
Position of relaxed abdominal muscles
Passive expiration
Active expiration
Contraction of abdominal muscles causes diaphragm
to be pushed upward, further reducing
vertical dimension of thoracic cavity
Return of diaphragm, ribs, and sternum to resting
position on relaxation of inspiratory muscles
restores thoracic cavity to preinspiratory size
(c)
(b)
Fig. 11-21bc, p.483
32
(No Transcript)
33
H2O molecules
An alveolus
Fig. 11-23, p.486
34
Fig. 11-26, p.489
35
Fig. 11-27, p.490
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
Factors affecting the exchange of oxygen and
carbon dioxide during internal respiration 1.The
available surface area 2. Partial pressure
gradients. 3. The rate of blood flow in a
specific tissue.
41
Oxygen and Carbon Dioxide Transportation
The blood transports oxygen and carbon dioxide
between the lungs and other tissues throughout
the body. These gases are carried in several
different forms 1. dissolved in the plasma 2.
chemically combined with hemoglobin 3. converted
into a different molecule
42
(No Transcript)
43
Hemoglobin and 02 Transport

• 280 million hemoglobin/ RBC.
• Each hemoglobin has 4 polypeptide chains and 4
  hemes.
• Each heme has 1 atom iron that can combine with 1
  molecule O2
• Each hemoglobin can combine with 4 molecule O2
• Combine reversibly with O2 depend on PO2

44
Hemoglobin's affinity for oxygen increases as its
saturation increases
the affinity of hemoglobin for oxygen decreases
as its saturation decreases
45
Hemoglobin

• Oxyhemoglobin
• Normal heme contains iron in the reduced form.
  Reduced form of iron can share electrons and bond
  with oxygen.
• Deoxyhemoglobin
• When oxyhemoglobin dissociates to release oxygen,
  the heme iron is still in the reduced form.

46
Hemoglobin

• Hemoglobin production controlled by
  erythropoietin.
• Production stimulated by P02 delivery to kidneys.
• Loading/unloading depends
• P02 of environment.
• Affinity between hemoglobin and 02.

47
Oxyhemoglobin Dissociation Curve

• Oxygen dissociation curve describes the relation
  between percent of saturation and the partial
  pressure of oxygen (S-shape, sigmoid)
• At high PO2, a large amount of O2 is bound
• At low PO2, only small amount of O2 is bound

48
Hemoglobin saturation is determined by the
partial pressure of oxygen
S-shaped curve
49
(No Transcript)
50
(No Transcript)
51
Oxyhemoglobin Dissociation Curve

• Loading and unloading of 02.
• Steep portion of the curve, small changes in P02
  produce large differences in saturation (unload
  more 02).
• Decreased pH, increased temp., and increased 2,3
  DPG, increase CO2 affinity of Hb for 02
  decreases.
• Shift to the right greater unloading.

Bohr effect
52
(No Transcript)
53
Muscle Myoglobin

• Slow-twitch skeletal fibers and cardiac muscle
  cells are rich in myoglobin.
• Has a higher affinity for 02 than hemoglobin.
• Acts as a go-between in the transfer of 02 from
  blood to the mitochondria within muscle cells.
• May also have an 02 storage function in cardiac
  muscles.

54
Human fetal hemoglobin contains g chains, which
has a high O2 affinity than adult b hemoglobin
In humans, the oxygen affinity of blood decrease
for about 3 months after the birth
55
(No Transcript)
56
(No Transcript)
57
This reaction is catalyzed by the enzyme carbonic
anhydrase.
58
C02 Transport

• C02 transported in the blood
• HC03- (70).
• Dissolved C02 (7).
• Carbaminohemoglobin (23).
• HCO3- is high in plasma than in erythrocytes
• CO2 enters and leaves the blood as molecular CO2
  rather than HCO3-

59
Chloride Shift at Systemic Capillaries

• H20 C02 H2C03 H HC03-
• At the tissues, C02 diffuses into the RBC,
  reaction shifts to the right.
• Increased HC03- in RBC, HC03- diffuses into the
  plasma with assistance of band III protein.
• RBC becomes more .
• Cl- diffuses in (Cl- shift).
• HbC02 formed, give off 02.

60
At Pulmonary Capillaries

• H20 C02 H2C03 H HC03-
• At the alveoli, C02 diffuses into the alveoli,
  reaction shifts to the left.
• Decreased HC03- in RBC, HC03- diffuses into
  the RBC.
• RBC becomes more -.
• Cl- diffuses out (Cl- shift).
• Hb02 formed, give off HbC02.

61
(No Transcript)
62
(No Transcript)
63
Summary O2 is transported in two ways
dissolved in plasma, and bound to hemoglobin
as oxyhemoglobin The O2 saturation of
hemoglobin is affected by PO2, pH ,
temperature, PCO2, and DPG CO2 is transported
in three ways dissolved in plasma, bound to
hemoglobin as carbaminohemoglobin, and converted
to bicarbonate ions Oxygen loading facilitates
carbon dioxide unloading from hemoglobin. This is
known as the Haldane effect. When the pH
decreases, carbon dioxide loading facilitates
oxygen unloading. The interaction between
hemoglobin's affinity for oxygen and its affinity
for hydrogen ions is called the Bohr effect.
64
Pons
Pons respiratory centers
Pneumotaxic center
Apneustic center
Pre-Bötzinger complex
Respiratory control centers in brain stem
Dorsal respiratory group
Medullary respiratory center
Medulla
Ventral respiratory group
Fig. 11-40, p.513
65
Input from other areas some excitatory, some
inhibitory
Inspiratory neurons in DRG (rhythmically firing)
Medulla

Spinal cord

Phrenic nerve
Diaphragm
Not shown are intercostal nerves to external
intercostal muscles.
Fig. 11-41, p.513
66
Sensory nerve fiber
Sensory nerve fiber
Carotid sinus
Carotid bodies
Carotid artery
Aortic bodies
Aortic arch
Heart
Fig. 11-42, p.514
67
Arterial PO2 lt 60 mm Hg
No effect on
Fig. 11-43, p.515
68
Fig. 11-44, p.516