student of biological sciences at karakoram international university gilgit pakistan

1. GASEOUS EXCHANGE IN HUMAN
Zakia khatoon
Syyeda urooj
Nelofar Hanif
Diya Fatima
Kainat Abbas

2. INTRODUCTION
 Oxygen is needed for aerobic respiration
 CO₂ is produce as a result of aerobic respiration.
 Exchange of these gases with the environment.
 Need Respiratory Surface

3. RESPIRATORY SURFACES
• Thin
– Diffusion distance
– Speed
• Moist
– Gases dissolved in
solution
• Large
– SA to volume ratio
– Energy demands

4. ORGANS OF THE RESPIRATORY SYSTEM
 Nose
 Pharynx
 Larynx
 Trachea
 Bronchi
 Lungs –
alveoli
Figure 13.1

5. FUNCTION OF THE RESPIRATORY SYSTEM
 Oversees gas exchanges between the blood and
external environment
 Exchange of gasses takes place within the alveoli
 Passageways to the lungs purify, warm, and
humidify the incoming air

6. THE NOSE
 The only externally visible part of the respiratory
system
 Air enters the nose through the external nares
(nostrils)
 The interior of the nose consists of a nasal cavity
divided by a nasal septum

7. ANATOMY OF THE NASAL CAVITY
 Lateral walls have projections called conchae
 Increases surface area
 Increases air turbulence within the nasal cavity
 The nasal cavity is separated from the oral cavity by the
palate
 Anterior hard palate (bone)
 Posterior soft palate (muscle)

8. ANATOMY OF THE NASAL CAVITY
 Olfactory receptors are located in the mucosa on
the superior surface
 The rest of the cavity is lined with respiratory
mucosa
 Moistens air
 Traps incoming foreign particles
 Paranasal sinuses
 Cavities within bones surrounding the nasal cavity

9. PHARYNX (THROAT)
 Muscular passage from nasal cavity to larynx
 Three regions of the pharynx
 Nasopharynx – superior region behind nasal cavity
 Oropharynx – middle region behind mouth
 Laryngopharynx – inferior region attached to larynx
 The oropharynx and laryngopharynx are common
passageways for air and food

10. STRUCTURES OF THE PHARYNX
 Auditory tubes enter the nasopharynx
 Tonsils of the pharynx
 Pharyngeal tonsil (adenoids) in the nasopharynx
 Palatine tonsils in the oropharynx
 Lingual tonsils at the base of the tongue

11. LARYNX (VOICE BOX)
 Routes air and food into proper channels
 Plays a role in speech
 Made of eight rigid hyaline cartilages and a spoon-
shaped flap of elastic cartilage (epiglottis)
 Vocal cords - vibrate with expelled air to create
sound (speech)

12. STRUCTURES OF THE LARYNX
 Thyroid cartilage
 Largest hyaline cartilage
 Protrudes anteriorly (Adam’s apple)
 Epiglottis
 Superior opening of the larynx
 Routes food to the larynx and air toward the trachea
 Glottis
 opening between vocal cords

13. TRACHEA (WINDPIPE)
 Connects larynx with bronchi
 Lined with ciliated mucosa
 Beat continuously in the opposite direction of incoming air
 Expel mucus loaded with dust and other debris away from
lungs
 Walls are reinforced with C-shaped hyaline cartilage

14. PRIMARY BRONCHI
 Formed by division of the trachea
 Enters the lung at the hilus
(medial depression)
 Right bronchus is wider, shorter,
and straighter than left
 Bronchi subdivide into smaller
and smaller branches

15. BRONCHIOLES
 Smallest branches
of the bronchi
 All but the smallest
branches have
reinforcing cartilage
 Terminal
bronchioles end in
alveoli (grape like
sacs).
Figure 13.5a

16. LUNGS
 Ocupy most of the thoracic cavity
 Apex is near the clavicle (superior
portion)
 Each lung is divided into lobes by
fissures
Left lung – two lobes
Right lung – three lobes

17. LUNGS
Figure 13.4b

18. ORGANS IN THE RESPIRATORY SYSTEM
STRUCTURE FUNCTION
nose / nasal cavity
warms, moistens, & filters air as it is
inhaled
pharynx (throat) passageway for air, leads to trachea
larynx
the voice box, where vocal chords are
located
trachea (windpipe)
keeps the windpipe "open"
trachea is lined with fine hairs called
cilia which filter air before it reaches the
lungs
bronchi
two branches at the end of the trachea,
each lead to a lung
bronchioles
a network of smaller branches leading from
the bronchi into the lung tissue &
ultimately to air sacs
alveoli
the functional respiratory units in the lung
where gases are exchanged

19. RESPIRATORY DISRUPTIONS
• Smoking
– Inhibit cilia movement causes ‘smoker’s cough’
• Thicken bronchioles and reduce elasticity
• Alveoli rupture
– Stopping allows cilia and alveoli damage to reverse
• Premature birth (37 weeks or less)
– Surfactant production incomplete
• Keeps alveoli from collapsing
– Each breath requires large effort
• Emphysema
– Bronchi swell, tearing alveoli
– Reduced SA for gas exchange
• Pneumonia
– Fluid in alveoli
• Bronchitis inflames of bronchioles

20. VENTILATION/BREATHING
 The movement of air between the environment and
the lungs via inhalation and exhalation.
 Mechanical ventilation: using artificial methods to
assist breathing
 Medical ventilator: a mechanical ventilator, a
machine designed to move breathable air into and
out of the lungs.

21. CONTROL OF BREATHING
Respiratory centre
Chemoreceptor
pCO2

22. MECHANISM OF BREATHING
(PULMONARY VENTILATION)
 Mechanical process
 Depends on volume changes in the thoracic cavity
 Volume changes lead to pressure changes, which lead to
equalize pressure of flow of gases
 2 phases
 Inspiration – flow of air into lung
 Expiration – air leaving lung

23. ORGANS INVOLVED
Diaphragm
Intercostals' muscles
Ribcage

24. INSPIRATION
Active process
Quiet inspiration
Volume of ribcage increases
pressure will drop
air flow into the lungs.

25. .
 Active process
 Diaphragms contracts and flattens
 Thoracic cavity enlarges
 External intercostals muscles contract
 The ribs move up and outward and enlarges the
thoracic cavity
 Total volume of the thoracic cavity increases
Decrease in air pressure
 The elastic lungs expand and air flows into the
lungs

29. EXPIRATION
 Passive process dependent up on natural lung
elasticity
 As muscles relax, air is pushed out of the lungs
 Forced expiration can occur mostly by contracting
internal intercostal muscles to depress the rib cage

30. EXPIRATION
Figure 13.7b

31. MEASURES OF PULMONARY VENTILATION
Respiratory volumes – values determined by using
a spirometer
 Tidal Volume (TV) – amount of air inhaled or exhaled with
each breath under resting conditions
 Inspiratory Reserve Volume (IRV) – amount of air that
can be inhaled during forced breathing in addition to
resting tidal volume
 Expiratory Reserve Volume (ERV) – amount of air that
can be exhaled during forced breathing in addition to tidal
volume
 Residual Volume (RV) – Amount of air remaining in the
lungs after a forced exhalation.

32. TRANSPORT OF GASES
 The exchange of gases (O₂ & CO₂) between the
alveoli & the blood occurs by simple diffusion.
 O₂ diffusing from the alveoli into the blood & CO₂
from the blood into the alveoli.
 Diffusion requires a concentration gradient. So, the
concentration (or pressure) of O₂ in the alveoli must
be kept at a higher level than in the blood & the
concentration (or pressure) of CO₂ in the alveoli
must be kept at a lower lever than in the blood.

33. PARTIAL PRESSURE
 The partial pressure exerted by each gas in a
mixture equals the total pressure times the
fractional composition of the gas in the mixture.
 Total atmospheric pressure (at sea level) is about
760 mm Hg and, further, that air is about 21%
oxygen, then the partial pressure of oxygen in the
air is 0.21 times 760 mm Hg or 160 mm Hg.

34. LEVEL OF THE PARTIAL PRESSURE OF
MAIN GASES IN THE HUMAN BODY
 Partial Pressures of O2 and CO2 in the body
(normal, resting conditions):
Alveoli
 PO2 = 100 mm Hg
 PCO2 = 40 mm Hg
Alveolar capillaries
 Entering the alveolar capillaries
 PO2 = 40 mm Hg
 PCO2 = 45 mm Hg

35.  While in the alveolar capillaries, the diffusion of gasses
occurs: oxygen diffuses from the alveoli into the blood &
carbon dioxide from the blood into the alveoli.
 Leaving the alveolar capillaries
 PO2 = 100 mm Hg
 PCO2 = 40 mm Hg
 Blood leaving the alveolar capillaries returns to the left
atrium & is pumped by the left ventricle into the systemic
circulation. This blood travels through arteries &
arterioles and into the systemic, or body, capillaries.
 Entering the systemic capillaries
 PO2 = 100 mm Hg
 PCO2 = 40 mm Hg
 Body cells (resting conditions)
 PO2 = 40 mm Hg
 PCO2 = 45 mm Hg

37.  Because of the differences in partial pressures of
oxygen & carbon dioxide in the systemic
capillaries & the body cells, oxygen diffuses from
the blood & into the cells, while carbon dioxide
diffuses from the cells into the blood.
 Leaving the systemic capillaries
 PO2 = 40 mm Hg
 PCO2 = 45 mm Hg
 Blood leaving the systemic capillaries returns to
the heart (right atrium) via venules & veins (and
no gas exchange occurs while blood is in
venules & veins). This blood is then pumped to
the lungs (and the alveolar capillaries) by the
right ventricle.

38. TRANSPORT OF CO₂ IN BLOOD
Three main ways to transport CO₂ in blood from tissues to
lungs
 As bicarbonate ions
 As carboxyhaemoglobin
 As dissolved CO₂ in plasma

40. AS BICARBONATE IONS
 Most of the carbon dioxide approximately 70% is carried in
blood as bicarbonate ions.
 CO₂ entering blood cells reacts with water and form carbonic
acid in the presence of carbonic anhydrase.
 Carbonic acid is unstable and splits into H+ and HCO₃⁻
 H+ combine with H₄bO₂ that dissociates O₂ from Hb and
diffuse into cells for aerobic respiration.
 The bicarbonate ion then diffuses outside the RBC in the
plasma and combines with Sodium ions to from Sodium
bicarbonate (NaHCO3).

41. CONT..
 Loss of bicarbonate ions from RBC causes positive
charge inside RBC which is balanced by diffusion of
chloride (Cl-) ion from plasma into the RBC.
 This exchange of Cl- ion and HCO3- ion between
plasma and RBC is known as chloride shift.
 This phenomenon of chloride shift maintains the
electrical neutrality of cell.

42. O₂ HEMOGLOBIN DISSOCIATION CURVE
 The following four factors decrease the affinity, or
strength of attraction, of Hb for O 2 and result in a
shift of the O 2‐Hb dissociation curve to the right
1. Increase in temperature.
2. Increase in partial pressure of CO 2 (pCO 2). The
effect of CO2 on Oxygen dissociation curve is
known as Bohr effect.
3. Increase in acidity (decrease in pH).

43.  It has been found that increase in concentration of
CO2 decreases the amount of oxyhaemoglobin
formation.
 according to Bohr effect, for any particular partial
pressure of Oxygen, the affinity of Haemoglobin
toward Oxygen decreases and favors dissociation
of oxyhaemoglobin when the partial pressure of
carbondioxide increases.
 It means, higher CO2 concentration causes the
dissociation of HbO2 releasing free O2.
 Increase in PCO2 shifts the O2 dissociation curve
downwards. Higher PCO2 lowers the affinity of
hemoglobin for O2.

45. AS CARBAMINOHAEMOGLOBIN (23%)
 some CO2 combines with Haemoglobin to form
carbaminohaemoglobin in RBCs.
 CO2 + NHbNH2————–HbNH.COOH
(carbaminohaemoglobin).
 finally, CO2 are carried to lungs and expelled out by
expiration process of breathing

46. AS DISSOLVED CO₂ IN PLASMA
 some CO₂ dissolved in the plasma to form carbonic acid
 carbon dioxide mixed with water of blood plasma to
form carbonic acid.
 CO₂+ H₂O——————H₂CO₃

47. CO₂ POISONING/
HYPERCAPNIA OR HYPERCARBIA
Causes: breathing volcanic gas.
 rebreathing exhaled air (e.g., from breathing air in a
bag, sleeping in a sealed tent, sleeping with a blanket
over one's head)
 scuba diving, hypoventilation, lung diseases.
 breathing in confined spaces or areas with poor air
circulation, such as a sealed room, a tunnel, cargo.
Symptoms:
 high blood pressure, flushed skin, headache and
twitching muscles.
 At severe conditions panic, irregular heartbeat,
hallucinations, vomited and potentially
unconsciousness or even death.

48. RESPIRATORY DISORDERS
Pre-term birth can lead to infants with under-
developed lungs . Smoking and air pollution are two
common causes of respiratory problems.
Diorders include:
 Obstructive conditions (e.g., emphysema,
bronchitis, asthma attacks)
 Infectious, environmental: (e.g., pneumonia,
tuberculosis, asbestosis, particulate pollutants):

49. CONT…
Common Respiratory Disorders Include:
 Swine flu, also called swine influenza, hog flu,
or pig flu, a respiratory disease of pigs that is
caused by an influenza virus.
 Chronic Bronchitis: - Any irritant reaching the
bronchi and bronchioles will stimulate an increased
secretion of mucus. In chronic bronchitis the air
passages become clogged with mucus, and this
leads to a persistent cough.

50. CONT…
 Emphysema: The delicate walls of the alveoli
break down, reducing the gas exchange area of the
lungs. The condition develops slowly and is seldom
a direct cause of death.
 Asthma: - Periodic constriction of the bronchi and
bronchioles makes it more difficult to breathe.
 Pneumonia :- An infection of the alveoli. It can be
caused by many kinds of both bacteria and viruses.
Tissue fluids accumulate in the alveoli reducing the
surface area exposed to air. If enough alveoli are
affected, the patient may need supplemental
oxygen.