Breathing and Exchange of Gases - Part 4 for NEET

1. Part - 4

2. Transport of Gases
• Blood is the medium of
transport for O2 and CO2
and transports gases
between the lungs and
body tissues.

3. Transport of Oxygen
97%
3%
As Oxyhaemoglobin (97%) As Dissolved Oxygen (3%)
• Through RBC
• In combination with Hb
• Through blood plasma
• Dissolved in H2O

4. As Oxyhaemoglobin
Haemoglobin
4 polypeptides,
4 haeme groups
1 Fe2+ in each haeme
4 O2 (one to each Fe2+/haeme)

5. 2 2
deoxyhaemoglobin oxygen oxyhaemoglobin
(reduced haemoglobin)
Hb O Hb O 
Oxygenation

6. Oxygen Dissociation Curve
• X axis: pO2
• Y-axis: % saturation of Hb
• Binding of oxygen with
haemoglobin is primarily
related to partial pressure of
O2.
pO2 % Saturation
95 mm Hg 97%
40 mm Hg
(resting tissues)
75%
26.7 mm Hg (P50) 50%
20 mm Hg 35%

7. In the alveoli:
high pO2,
low pCO2,
lesser H+ concentration
lower temperature,
Favour for formation of HbO2
In the tissues:
low pO2,
high pCO2,
high H+ concentration
higher temperature
Favour dissociation of HbO2

8. Bohr Effect
• Effect of CO2 and the H+ on the oxygen-affinity of haemoglobin
• Oxygen dissociation curve shifts to the right.

9. Effect of Temperature

10. Every 100 ml of oxygenated blood can deliver around 5 ml of O2 to the
tissues under normal physiological conditions
Amount of Hb in 100 mL of blood = 15 grams
Amount of O2 that can bind to
1 gram of Hb = 1.34 mL
Amount of O2 in 100 mL of
systemic arterial blood = 1.34x15x 97%
= 19.4 mL
Amount of O2 in 100 mL of
systemic venous blood = 14.4 mL
Amount of O2 delivered by 100 mL
of oxygenated blood to tissues = 19.4-14.4 = 5 mL

11. 2,3-bisphosphoglycerate (BPG)
• Formed in RBC during
glycolysis
• Decreases the affinity of
haemoglobin for O2
• BPG has little effect on
Hb-F.
• Therefore, O2-affinity of
Hb-F>Hb-A

12. Foetal Haemoglobin
1. Con. of Hb-F appr. 50% > Hb-A
2. Oxygen dissociation curve of Hb-F is to the left to that of the maternal Hb (Hb-A)
3. BPG has little effect on Hb-F

13. Double Bohr Effect

14. Transport of Carbon Dioxide
97%
7%
23%
70%
Dissolved Carbamino Compounds Bicarbonates

15. As Carbamino Compounds
• CO2 binds to terminal amino acids in the alpha and beta globin chains.
• This binding is related to the partial pressure of CO2.
• pO2 is a major factor which could affect this binding.

16. As Bicarbonate Ions
Haemoglobin can act as a buffer at physiological pH (7.4), because of its high content
of histidine.

17. Chloride Shift or Hamburger’s Phenomenon
Chloride
shift
Reverse
chloride
shift

19. Haldane Effect

20. Regulation of Ventilation
• Human beings have a
significant ability to maintain
and moderate the respiratory
rhythm to suit the demands of
the body tissues.
• This is done by the neural
system.
• A specialised centre present
in the medulla region of the
brain called respiratory
rhythm centre is primarily
responsible for this
regulation.

21. Regulation of Ventilation
Control through the respiratory centres in
the brain stem
Neural Control
Control through central and peripheral
chemoreceptors
Chemical Control

22. Respiratory Centre
• The group of neurons
located in the medulla
oblongata and pons
of the brain stem,
which send nerve
impulses to the
respiratory muscles,
is called the
respiratory centre.

23. Respiratory Centre
Medullary Rhythmicity Area
Pneumotaxic Centre
Apneustic Centre

24. Medullary Rhythmicity Area
• The function of the
medullary rhythmicity
area is to control the
basic rhythm of
respiration.
• There are inspiratory
and expiratory areas
within the medullary
rhythmicity area.

25. Nerve impulses generated in the DRG (inspiratory
area) establish the basic rhythm of breathing.
DRG Becomes Active
Inspiration Occurs
DRG Becomes Inactive
Passive Expiration Occurs
While DRG is active, it generates
nerve impulses for 2 seconds.
Diaphragm and external
intercostal muscles relax
allowing passive elastic
recoil of the lungs
When these impulses reach,
diaphragm and external intercostal
muscles contract
The inspiratory area becomes
inactive for 3 seconds

26. Expiratory Area
• The neurons of the VRG (expiratory area)
remain inactive during quiet breathing.
• During forceful breathing, nerve impulses
from the DRG activate the VRG.
• Impulses from the VRG cause forceful
breathing (both inspiration and expiration).

27. • The neurons of the VRG
(expiratory area) remain
inactive during quiet
breathing.
• During forceful breathing,
nerve impulses from the DRG
activate the VRG.
• Impulses from the VRG cause
forceful breathing (both
inspiration and expiration).
Forceful
Breathing
Ventral Respiratory Group

28. • Pneumotaxic centre can moderate the
functions of the respiratory rhythm
centre.
• It transmits inhibitory impulses to the
inspiratory area.
• Neural signals from this centre can reduce
the duration of inhalation and thereby
alter the respiratory rate.
• When the pneumotaxic area is more
active, breathing rate is more rapid.
• Thus, pneumotaxic centre controls the
rate and depth of breathing.
Shorter Duration of Inhalation
Pneumotaxic Area

29. • This area sends stimulatory
impulses to the inspiratory area
that activate it and prolong
inhalation.
• The result is a long, deep
inhalation.
• When the pneumotaxic area is
active, it overrides signals from
the apneustic area.
Long and Deep Inhalation
Apneustic Area

30. Cerebral and Limbic
System Control
• As the cerebral cortex has
connections with the
respiratory centre, we can
voluntarily alter our pattern
of breathing (e.g. during
talking or singing).
• Nerve impulses from the
hypothalamus and limbic
system also stimulate the
respiratory centre, allowing
emotional stimuli to alter
respirations as, for
example, in laughing and
crying.

31. Chemical Control of Ventilation
• Chemoreceptors are
specialized neurons that
respond to changes in
chemicals in solution.
• The chemoreceptors
involved in the regulation
of respiration respond to
changes in hydrogen
ion concentrations,
changes in pCO2, or both.
• They modulate the
activity of the respiratory
centres.

32. Central Chemoreceptors
• Central chemoreceptors are
located in the chemosensitive
area of the medulla oblongata
adjacent to the respiratory
rhythm centre.
• These are highly sensitive to
CO2 and H+.
• Increase in these substances
can activate this centre, which
in turn can signal the rhythm
centre to make necessary
adjustments in the respiratory
process by which these
substances can be eliminated.

33. Peripheral
Chemoreceptors
• Peripheral
chemoreceptors
associated with aortic
arch (aortic bodies) and
carotid artery (carotid
bodies) also can
recognise changes in
CO2 and H+ concentration
and send necessary
signals to the rhythm
centre for remedial
actions.

34. Role of Oxygen
• The role of oxygen in the regulation of respiratory rhythm is quite
insignificant (under normal conditions).
• Because of the S shape of the curve, at any pO2 above 80 mm Hg, nearly
all of the haemoglobin is saturated with oxygen.

35. Regulation of Ventilation
• Man cannot hold his breath for
long.
• He is forced to breathe in.
• When pCO2 and H+
concentrations increase to a
certain level, the respiratory
rhythm centre is strongly
stimulated which resumes
breathing.
• At sea level carbon dioxide is
the main stimulus to ventilation.
At higher altitudes hypoxia
increases ventilation when pO2
in the inspired air is reduced to
about 100 mmHg (3000 m
altitude).

36. Respiratory System
• At a height of about 6000 m the pO2 becomes almost
half of what it is at the mean sea level, hence the
mountain sickness in people ascending mountains.

37. Disorders of Respiratory System
1 Asthma
2 Emphysema
3 Bronchitis
4 Pneumonia
5 Occupational R. Disorders

38. Asthma
• Asthma is a difficulty in breathing causing
wheezing due to inflammation of bronchi and
bronchioles.
• It is characterized by the spasm of smooth
muscles present in the walls of the bronchi and
bronchioles.
• In asthma, the allergens cause release of
histamine and other inflammatory mediators due
to which the muscles around the bronchioles are
hyperexcitable and contract more than usual.
• Contraction of these muscles narrows the
bronchioles (broncho-constriction).

39. Asthma
• Symptoms include coughing, difficulty in
breathing and wheezing.
• Wheeze is a whistling sound produced
during breathing resulting from a partially
obstructed airway.
• The symptoms of asthma can be
alleviated by inhaling an aerosol mist
containing bronchodilators or
corticosteroids or both.

40. EMPHYSEMA
• Emphysema is a chronic
disorder in which alveolar
walls are damaged and they
coalesce due to which
respiratory surface is
decreased.
• The lungs show larger but
fewer alveoli which are more
fibrous and less elastic.
• One of the major causes of
this is cigarette smoking.

41. EMPHYSEMA
• Emphysema reduces the elastic
quality of the lungs and the total
surface area of the alveoli, which
decreases the rate of oxygen
diffusion from the lungs into the
circulation.
• Consequently, pO2 in the arteries
will be lower than normal.
• It is also physically harder to
exhale because of the loss of
elasticity, and therefore, arterial
CO2 levels increase.

42. Bronchitis
• It is the inflammation
of the bronchi,
resulting in the swelling
of mucous lining of
bronchi, increased
mucus production and
decrease in the
diameter of bronchi.
• Symptoms include
chronic cough with
thick mucus/sputum
(phlegm).

43. Bronchitis
Bronchitis
• It is the inflammation of
the bronchi, resulting in
the swelling of mucous
lining of bronchi,
increased mucus
production and
decrease in the
diameter of bronchi.
• Symptoms include
chronic cough with
thick mucus/sputum
(phlegm).
Bronchitis

44. COPD
• Asthma, emphysema and chronic bronchitis
come under Chronic Obstructive Pulmonary
diseases (COPDs).
• Asthma and chronic obstructive pulmonary
disease (COPD) have traditionally been
viewed as distinct clinical entities.
• Recently, however, much attention has been
focused on patients with overlapping features
of both asthma and COPD: those with
asthma COPD overlap syndrome (ACOS).

45. PNEUMONIA
• It is infection of lungs caused
by bacteria such as
Streptococcus pneumoniae
and also by certain viruses,
fungi, protozoans and
mycoplasmas.
• Symptoms include
inflammation of lungs,
accumulation of mucus in
alveoli, and impaired
exchange of gases, leading to
death if untreated.

46. OCCUPATIONAL RESPIRATORY DISORDERS
• In certain industries, especially those
involving grinding or stone-breaking, so
much dust is produced that the defense
mechanism of the body cannot fully cope
with the situation.
• Long exposure can give rise to
inflammation leading to fibrosis
(proliferation of fibrous tissues) and thus
causing serious lung damage.

47. Occupational Respiratory Disorders
Occurs due to
chronic exposure to
asbestos dust in the
people working in
asbestos industry.
Asbestosis

48. Occupational Respiratory Disorders
Occurs because of
long term exposure
to silica dust in the
people working in
mining industries,
quarries, etc.
Silicosis

49. Occupational Respiratory Disorders
Occurs due to
deposition of
inhaled iron
particles in tissues.
Siderosis

50. Occupational Respiratory Disorders
A lung disease that
develops from
inhalation of coal
dust. It is common
in long time coal
mine workers.
Black Lung Disease

51. Types of Siderosis
Pneumoconiosis Due to inhalation of iron particles
Hyperferremia Abnormally high concentration of iron
in the blood
Hemosiderosis Causes recurrent alveolar hemorrhage
(iron overload disorder resulting in the
accumulation of hemosiderin)

52. OCCUPATIONAL RESPIRATORY DISORDERS
• Black-lung disease is a lung disease that
develops from inhalation of coal dust. It is
common in long time coal mine workers.
• Byssinosis is an occupational lung
disease caused by exposure to cotton dust
• Also called "brown lung disease" or
"Monday fever“.
• Common in workers of spinning and
ginning mills.

53. OCCUPATIONAL RESPIRATORY DISORDERS
• The patient may be provided with
symptomatic treatment, like
bronchodilators and antibiotics, to remove
underlying secondary infection.
• Workers in such industries should wear
protective masks.

54. Respiratory System
Elephant seal, a
mammal can remain
under water for up to two
hours.
The muscles of the
elephant seal and some
other aquatic mammals,
contains myoglobin
(muscle haemoglobin)
which has more affinity
for oxygen.

55. • Lung cancer, or bronchopulmonary carcinoma, is an
aggressive class of malignancies originating in the bronchial
passageways or alveoli.
• These cancers affect the epithelial cells that line conducting
passageways, mucous glands, or alveoli.
• Cigarette smoke is the most common cause of lung cancer.
• Signs and symptoms generally do not appear until tumours
restrict airflow or compress adjacent structures.
• Chest pain, shortness of breath, a cough or a wheeze, and
weight loss commonly occur.
• Treatment methods include surgery, radiation therapy and
chemotherapy.

56. Cystic fibrosis
• Cystic fibrosis (CF) is a life-threatening, genetic
disease.
• In people with CF, a defective gene causes a thick,
build-up of mucus in the lungs, pancreas and other
organs.
• In the lungs, the mucus clogs the airways and
traps bacteria leading to infections, extensive lung
damage and eventually, respiratory failure.
• In the pancreas, the mucus prevents the release
of digestive enzymes that allow the body to break
down food and absorb vital nutrients.

57. Severe Acute Respiratory Syndrome
(SARS)
• Severe Acute Respiratory Syndrome (SARS) is a contagious respiratory disease
first identified in 2002. SARS is caused by a coronavirus (SARSCoV) that exists in
bats and civets (carnivorous mammals) in Southern China.
• The infection is spread easily from person to person through respiratory droplets.
• Infected people have symptoms of pneumonia, including fever and shortness of
breath.
• Diarrhoea may also occur.
• Severely affected people experience respiratory failure and may need mechanical
ventilation.
• Older people, pregnant women, and those with underlying illnesses are at higher risk
for severe disease.
• No cases of SARS have been diagnosed since 2004.
• There is no medication that is known to treat SARS.
• Treatment is supportive.
• During the 2002 outbreak, approximately 25% of people had severe respiratory
failure and 10% died.
• The SARS outbreak in 2002 was controlled solely by using public-health measures
such as wearing surgical masks, washing hands well, and isolating infected patients.

58. • Rhinitis is the chronic or acute inflammation
of the mucous membrane of the nose due to
viruses, bacteria, or irritants.
• Excessive mucus production produces a
runny nose, nasal congestion, and postnasal
drip.
• Sputum is a mixture of mucus and other
fluids from the air passages that is
expectorated (expelled by coughing).