Physiology & Anatomy of Respiratory System

1. RESPIRATION
- Principal functions of respiratory system is the exchange of gases between the
atmosphere, blood and the cells of the body.
- Other functions:
1. Filters inspired air
2. Houses the sense organs for smell
3. Sound production
- it has 3 basic steps;
1. PULMONARY VENTILATION
(BREATHING)
2. EXTERNAL (PULMONARY)
RESPIRATION
3. INTERNAL (TISSUE)
RESPIRATION

3. RESPIRATION
1. PULMONARY VENTILATION (BREATHING) – includes INSPIRATION
(inflow) and EXPIRATION (outflow) of air between the air spaces of lungs.

4. RESPIRATION
2. EXTERNAL (PULMONARY)
RESPIRATION
- Involves exchange of gases between the air
spaces of lungs and blood in the pulmonary
capillaries
- The pulmonary capillary blood gains oxygen
and looses carbon dioxide to the air in the
alveoli.

5. EXTERNAL (PULMONARY) RESPIRATION

6. RESPIRATION
3. INTERNAL (TISSUE) RESPIRATION
- Is the exchange of gases between blood in systemic capillaries and tissue cells
(BLOOD) Loses oxygen and gains carbon dioxide
(CELLS OF THE BODY)
The metabolic reactions consumes oxygen and gives off carbon dioxide during
production of ATP (called CELLULAR RESPIRATION)

7. INTERNAL (TISSUE) RESPIRATION

8. NOSE
FUNCTION
1. Warms, moistens and filters air - nasal hairs
2. Olfaction (i.e. has olfactory receptors)
3. Speech (i.e. large, hollow resonating chambers modify speech sounds)
i.e. has the superior, middle, and inferior nasal conchae (turbinates') – lined with mucus
membrane containing goblet cells and is vascular (moistens and traps particles)

9. PHARYNX (throat)
- The anatomic regions are divided into 3 parts;
1. NASOPHARYNX
2. OROPHARYNX
3. LARYNGOPHARYNX

10. PHARYNX
1) NASOPHARYNX
- Superior portion of pharynx
- Lines by mucus membrane (pseudo-stratified columnar epithelium)
- It lies posterior to nasal cavity and extends to the plane of soft palate
- It has 5 openings; i.e.
- 2 internal nares
- 2 openings Eustachian (auditory) tubes.
- 1 opening into oropharynx
FUNCTION;
i) Respiration
ii) Also exchanges small amounts of air with auditory tubes to equalize air pressure
between pharynx and middle ear
iii) Also contains pharyngeal tonsil

11. PHARYNX
2) OROPHARYNX
- The intermediate portion
- Lined by nonkeratinized stratified squamous epithelium
- It lies posterior to oral cavity and extends from soft palate inferiorly to the level of hyoid
bone.
- Has only one opening, the fauces.
FUNCTION:
i) Respiratory function
ii) Digestive function
iii) Also contains palatine and lingual tonsil
NB: It is a common pathway of air,
food and drink

12. PHARYNX
3) LARYNGOPHARYNX
- Inferior portion of pharynx
- Line by non-keratinized stratified squamous epithelium
- It begins at the level of hyoid bone and connects the oesophagus with the larynx, (voice
box).
FUNCTION
- Respiratory and digestive pathway.

13. LARYNX
1) THYROID CARTILAGE (Adam’s apple)
2) EPIGLOTTIS
FUNCTION:- prevents food from entering the larynx
3) CRICOID CARTILAGE
FUNCTION:- connects the larynx and trachea
4) PAIRED i) ARYTENOID CARTILAGE
ii) CORNICULATE CARTILAGE
iii) CUNEIFORM CARTILAGE
5) VOCAL CORDS
FUNCTION;- Produce sounds as they vibrate
i.e. a) tense/ taut vocal cords – high pitches
b) relaxed vocal cords – low pitches)
- Lined by nonkeritinized stratified squamous epithelium

14. LUNGS
- Left lung is 10% smaller than right lung
- Right lung is thicker and broader and shorter than left lung (Diaphragm is higher on right
side accommodating the liver the lies inferior to it)
BLOOD SUPPLY
• Arteries
- Oxygenated blood enters via bronchial arteries (branch of descending aorta) supplies
muscular walls of bronchi and bronchioles
- Deoxygenated blood enters lungs via pulmonary arteries
• Veins
- Four pulmonary veins

15. • Unique to pulmonary circulation is the vasoconstriction of pulmonary blood vessels at
hypoxia (low O2 level).
• For circulation in other tissues, hypoxia cause vasodilatation of the blood vessels.
Significance: allows for ventilation-perfusion coupling.
i.e. where ventilation is maximal in the lung, perfusion should also follow through
maximally. And where ventilation in the lung is minimal, perfusion should also be
reduced proportionately. This is to ensure efficient gas exchange (Maximal amount of
oxygen is taken up by pulmonary capillaries).

16. LUNGS
- Each bronchopulmonary segment consists of lobules, which contain lymphatics,
arterioles, venules, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar
sacs and alveoli.
- Alveolar walls consists of;
1. Type 1 cells
2. Type 2 cells
FUNCTION – Secretes surfactant.
* SURFACTANT FUNCTION: It reduces surface tension (of alveolar fluid) within the alveoli
preventing alveolar from collapsing during expiration
3. Alveolar macrophages
- Gas exchange occurs across the alveolar – capillary (respiratory) membranes.

17. ALVEOLI

19. PULMONARY VENTILATION
• DEFINE i.e. breathing – inspiration (i.e. atmospheric air enters lungs) and expiration
(i.e. air expired from lungs into the atmosphere)
• WHAT IS THE BASIC PRINCIPAL IN THE MECHANICS OF BREATHING?

20. INSPIRATION
• DEFINE – i.e. air moves down it’s pressure gradient from atmosphere into lungs.
- So we need to make the lungs have a lower pressure than the atmosphere pressure.
HOW IS THIS ACHIEVED?
Revise boyle’s law which shows relationship between pressure and volume at constant
temperature.
i.e. To pressure in lungs, we have to the lung volume.
- This is actively done by expanding thoracic cavity (which indirectly expands lung volume)
using inspiratory muscles.

21. INSPIRATORY MUSCLES
- There are 2 main inspiratory muscles;
1. EXTERNAL INTERCOSTAL MUSCLES
2. DIAPHRAGM
1. EXTERNAL INTERCOSTAL MUSCLES
FUNCTION: - They pull the ribs superiorly and sternum anteriorly.
( Anterior-posterior dimension of thoracic cavity)
NERVE SUPPLY: - Intercostal nerve
- Regulated by medullary respiratory center in reticular formation.
HOW? It sets the rate of breathing by sending impulses that last 2 seconds to the external
intercostal muscles via the intercostal nerve.

22. External intercostal muscle
• At contraction it elevates ribs, responsible for ~25% of air that enters lungs at
normal quiet breathing

23. INSPIRATORY MUSCLES
2. DIAPHRAGM
FUNCTION: - When the diaphragm contracts, it flattens and moves inferiorly.
( Superior – inferior dimension of thoracic cavity)
NERVE SUPPLY: Phrenic nerve
- It is regulated by medullary respiratory center in reticular formation.
HOW?
- It sets the rate of breathing by sending impulses that lasts 2 seconds to the diaphragm via the
phrenic nerve.
- Contraction of diaphragm is responsible for 75% of air entering at inspiration at rest.
NOTE: The diaphragm and external intercostal muscles contracts at the same time.

24. diaphragm
• (at inspiration)
- Descends 1 cm, produces pressure difference of 1- 2 mmHg, and at inhalation (at rest)
500mL of air enter
- Strenous breathing, diaphragm descends ~10 cm, produce a pressure difference of
100mmHg, and inhalation of 2 - 3 liters of air.

25. INSPIRATORY MUSCLES

26. INSPIRATORY MUSCLES

28. Inspiration
• (Forced inspiration)
Extra muscles recruited include (increase size of thoracic cavity):
1.Sternoceidomastoid muscle – elevates sternum
2.Scalene muscle – elevates first 2 ribs
3.Pectoralis minor muscle - elevates 3rd – 5th rib

29. INSPIRATION
• DESCRIBE THE EFFECTS OF THE CONTRACTION OF THE INSPIRATORY
MUSCLES (diaphragm and external intercostal muscles)

30. INSPIRATORY MUSCLES contract (continue)

31. EXPIRATION
i.e. Air is also moving down the pressure gradient from lungs into the atmosphere.
- Can be discussed in terms of;
a) Quiet breathing
b) Active breathing

32. EXPIRATION
QUIET BREATHING
i.e. a passive process because no muscular contractions involved.
1. INSPIRATORY MUSCLES are RELAX
2. ELASTIC RECOIL of chest wall and lungs
3. Inward pull of surface tension due to film of alveolar fluid

33. EXPIRATION
1. INSPIRATORY MUSCLES are RELAX

34. ACTIVE BREATHING
EXAMPLES of situations where active breathing happens.
a) Labored breathing
b) Conditions where air movement outside the lung is impeded.

35. Other factors affecting pulmonary ventilation
1. Surface tension of alveolar fluid
2. Compliance of the lungs
3. Airway resistance

36. • Surface tension – is force exerted on the surface of liquids causing them to have
“skin-like” effect(
- Surfactant reduces surface tension of alveolar fluid below surface tension of pure
water.
- Surfactant is a mixture of phospholipids and lipoproteins in present in alveolar fluid.
- Respiratory distress syndrome – deficiency of surfactant, surface tension of alveolar
fluid increase, so many alveoli collapse at end of relaxation

37. ALVEOLAR SURFACE TENSION
- Alveolar surface tension is produced by a thin layer of alveolar fluid that lies next to the
air in the alveoli.
- It exerts a force known as surface tension.

38. ALVEOLAR SURFACE TENSION
SIGNIFICANCE OF THE ALVEOLAR SURFACE TENSION;
- The alveolar fluid surrounding the alveolus, produces surface tension, an inwardly
directed force.
(ROLE OF SURFACE TENSION AT EXPIRATION)
- Alveolar surface tension is a major component of lung elastic recoil.
EFFECT: It assists in the size of alveoli during expiration.
(ROLE OF SURFACE TENSION AT INSPIRATION)
- Alveolar surface tension is undesirable because it increases the work of inflating the
alveolar.
- So therefore the lungs needs to alveolar surface tension at inspiration

39. ALVEOLAR SURFACE TENSION
Alveolar surface tension
makes inspiration difficult
Alveolar surface tension
assists in expiration of air out
of the lungs

40. ALVEOLAR SURFACE TENSION
- At inspiration, the lungs needs to decrease the alveolar surface tension.
HOW? Lungs decreases the alveolar surface tension by producing surfactant, a detergent like
substance.
DESCRIBE SURFACTANT – made of a mixture of phospholipids and lipoprotein.
FUNCTION OF SURFACTANT - Surface tension of alveolar fluid.
Net effect: Decreases the tendency for the complete collapse of alveoli at expiration.

41. • Compliance of lungs (refers to how effort is required to stretch lungs and chest wall)
i.e. high compliance – means lungs and chest expand easily
• Compliance is related to (2 factors):
i) elasticity
ii) surface tension.
• Lungs have high compliance if elastic fibers in lungs are easily stretched and surfactant
in alveoli fluid reduces surface tensions

42. COMPLIANCE
DEFINE – Compliance is the ease at which lungs and thoracic wall can be expanded.
• HIGH COMPLIANCE – means the lungs and thoracic wall can expand easily.
• LOW COMPLIANCE – means that lungs resists expansion
FACTORS THAT INFLUENCE COMPLIANCE;
1) ELASTICITY – i.e. Elastic fibers in lung tissue allows for them to be easily stretched.
2) SURFACE TENSION – i.e. Surfactant in alveolar fluid surface tension.

43. COMPLIANCE
• EXAMPLE OF CONDITIONS THAT COMPLIANCE.
i) Scar lung tissue – E.g. TB
ii) Lung(s) filled with fluid – e.g. Pulmonary oedema
iii) Deficiency of surfacant
iv) Conditions that impede lung expansion
E.g. Paralysis of phrenic and intercostal nerves.

44. AIRWAY RESISTANCE
DESCRIBE THE RELATIONSHIP OF AIRFLOW VELOCITY
IN AIRWAYS TO AIRWAY RESISTANCE?
Meaning;
Airway resistance will airflow velocity

45. AIRWAY RESISTANCE
FACTORS THAT AFFECT AIRWAY RESISTANCE;
1) BREATHING
(EXPIRATION) – (Reverse of the above)

46. AIRWAY RESISTANCE
2) DEGREE OF CONTRACTION. RELAXATION OF SMOOTH MUSCLES OF
AIRWAYS.

47. AIRWAY RESISTANCE
3) CONDITIONS THAT OBSTRUCT OR NARROW AIRWAY RESISTANCE

48. • Airway resistance
• Rate of airflow through airways depends on:
i) pressure difference - Airflow is influenced by the pressure difference between
atmospheric and alveoli pressure.
ii) Resistance - Walls of airways (dimensions) especially bronchioles offer resistance to
normal flow of air into and out of lungs
i.e. larger diameter airways – the air flows freely (less resistance) through the airways when
compared to a narrower airway
Significance: narrow airways (at exhalation and sympathetic stimulation of smooth muscle
of bronchioles) increases resistance to air flow
E.g. Asthma, COPD (complex disease that has emphysema and chronic bronchitis) –
increases airways resistance. (from obstruction or collapse of airways)

49. BREATHING PATTERNS
• EUPNEA – is normal quiet breathing (shallow and deep breathing combined).
• APNEA – is a temporary cessation of breathing
• DYSPNEA – is painful or laboured breathing
• TACHYPNEA – is rapid breathing
• COSTAL (shallow) BREATHING – shallow breathing. Named after chest breathing,
where there is an upward and outward movement of chest due to contraction of external
intercostal muscles.
• DIAPHRAGMATIC (deep) BREATHING – deep breathing i.e. due to outward
movement of the abdomen due to the contraction and descent of the diaphragm

50. LUNG VOLUMES & CAPACITIES
- In clinical practice, respiration (ventilation) is defined as “one inspiration and one
expiration”.
- Average adult normal respiratory rate is ~ 12 resp. / min
The equivalent quantitative amount is ~ 6 Liters/ min
- The apparatus used for quantitatively assessing respiration is called SPIROMETER
(RESPIROMETER).
• WHAT DOES THE SPIROMETER MEASURE?
i) Rate of ventilation
ii) Volume of air exchanged during breathing
iii) Produces a record called a SPIROGRAM.

51. SPIROMETER

52. SPIROMETER

54. SPIROGRAM
• SPIROGRAM – the record produced by a spirometer.
• Upward deflection on spirogram correlates with inhalation
• Downward deflection on spirogram correlates with exhalation

55. SPIROGRAM
• QUANTITATIVE VALUES PRODUCED BY A SPIROGRAM
- They can be discussed in terms of ;
a) Lung volumes at REST
i) Tidal volume, (VT)
ii) Minute volume of Respiration, (MVR)
iii) Alveolar ventilation rate, (AVR)
b)Lung volumes at STRENOUS BREATHING
i) Inspiratory reserve volume
ii) Expiratory reserve volume
iii) Forced expiratory volume in 1 sec (FEV1)

57. SPIROGRAM

58. SPIROGRAM;-LUNG VOLUMES AT REST
i) TIDAL VOLUME (VT) ~ 500mL
- It is the volume of air moved into and out of airways with each inspiration and expiration
during normal quiet breathing.
- SIGNIFICANCE;
- In the same person, tidal volume varies at different times.
- It varies between different individuals.
DISTRIBUTION OF TIDAL VOLUME

59. SPIROGRAM;-LUNG VOLUMES AT REST
ii) MINUTE VOLUME OF RESPIRATION (MVR)
DEFINITION – It is the total volume of air taken during 1 min. Also called MINUTE
VENTILATION.
- Not all minute ventilation can be used in gas exchange; some remains in the anatomic dead
space
CALCULATION of MVR;

60. SPIROGRAM;-LUNG VOLUMES AT REST
iii) ALVEOLAR VENTILATION RATE, (AVR)
DEFINITION – Volume of air per minute that reaches alveoli.
E.g. 350 mL/breath x 12 breaths/min = 4200 mL/min

61. LUNG VOLUMES AT STRENOUS BREATHING
• Lung volumes are larger in males, taller person and in younger adults.
• Lung volumes are smaller in females, shorter person and in elderly.
IMPORTANT USES OF LUNG VOLUMES;
i.e. For making diagnosis of respiratory disease by comparing the individual’s quantitative
volumes and the predicted normal average values for the individual – by gender, height
and age
EXAMPLES;
i) INSPIRATORY RESERVE VOLUME
ii) EXPIRATORY RESERVE VOLUME
iii) FORCED EXPIRATORY VOLUME IN 1 SEC

62. i) INSPIRATORY RESERVE VOLUME (IRV).
Amount of air in excess of tidal volume that can be inhaled with maximum effort.
How is the IRV volume measured?
(About 3100 mL in average adult male and comparatively 1900mL in average adult female)
LUNG VOLUMES AT STRENOUS BREATHING

63. LUNG VOLUMES AT STRENOUS BREATHING
ii) EXPIRATORY RESERVE VOLUME
Amount of air in excess of tidal volume that can be exhaled with maximum effort.
How is this measured?
(About 1200mL in males and 700mL in females)

64. LUNG VOLUMES AT STRENOUS BREATHING
iii) FORCED EXPIRATORY VOLUME in 1 second (FEV1). i.e. following a maximal
inhalation the volume of air forcefully expired in the 1 second is the FEV1
How is this volume measured?

65. LUNG VOLUMES AT STRENOUS BREATHING
• VOLUMES THAT ARE MEASURED INDIRECTLY;
i.e. i) RESIDUAL VOLUME
ii) MINIMAL VOLUME

66. LUNG VOLUMES
i) RESIDUAL VOLUME
- Amount of air remaining in the lungs after maximum expiration; that is, the amount of air
that can never be voluntarily exhaled.
- Even after the expiratory reserve volume is expelled, still some air remains in the
lungs.
- This volume can not be measured by spirometry.
EXPLAIN THE RESIDUAL VOLUME DISTRIBUTION.
- At lower intrapleural pressure;
- 1) Alveoli are kept slightly inflated
- 2) Some air remain in non-collapsible airways.

67. LUNG VOLUMES
ii) MINIMAL VOLUME

68. LUNG VOLUMES
MINIMAL VOLUME – Medico-legal application.
- Minimal volume provides a medico-legal tool for determining whether a baby was born or
died after birth.

69. LUNG CAPACITIES
DEFINE; - are combinations of specific lung volume.
- The different types of lung volumes include;
1. INSPIRATORY CAPACITY
2. FUNCTIONAL RESIDUAL CAPACITY
3. VITAL CAPACITY
4. TOTAL LUNG CAPACITY

70. LUNG CAPACITIES
i) INSPIRATORY CAPACITY
Maximum amount of air that can be inhaled following a normal expiration.
DEFINE – i.e. Tidal volume (VT) + Inspiratory reserve volume
4100 mL = 500 mL + 3600 mL
ii) FUNCTIONAL RESIDUAL CAPACITY
Amount of air remaining in the lungs following a normal expiration.
DEFINE – i.e. Residual volume + Expiratory reserve volume
3600 mL = 1200 mL + 2400 mL

71. LUNG CAPACITIES
iii) VITAL CAPACITY
DEFINE; Amount of air that can be forcefully exhaled following a maximum inspiration
iv) TOTAL LUNG CAPACITY
DEFINE; Maximum amount of air in the lungs at the end of a maximum inspiration

72. EXTERNAL RESPIRATION
• DEFINITION – Exchange of O2 and CO2 between air in alveoli of lungs and blood in
pulmonary capillaries.
i.e. deoxygenated blood from heart is oxygenated in the lungs and returned to the heart.
HOW?

75. EXTERNAL RESPIRATION
At pulmonary capillary – O2 is taken-up by the pulmonary capillary.
PULMONARY
CAPILLARY

76. At pulmonary capillary – CO2 is taken-up by the alveoli

77. EXTERNAL RESPIRATION
• FACTORS THAT AFFECT EXTERNAL RESPIRATION
(diffusion of gases)
1.Partial pressure difference of gases
2.Surface area for gas exchange
3.Diffusion distance
4.Solubility and molecular weight of gases

78. EXTERNAL RESPIRATION
FACTORS THAT AFFECT EXTERNAL RESPIRATION (diffusion of gases)
1. PARTIAL PRESSURE DIFFERENCE OF GASES
i.e. diffusion of O2 from alveolar air into pulmonary capillary will occur as long as pO2 in
alveolar is greater than pO2 in pulmonary capillary.
Describe situations where this can happen?
a) Certain drugs (e.g. morphine) slow ventilation
EFFECT: Amount of CO2 and O2 exchanged between alveoli and blood.
b) Higher altitudes
- At high altitudes, atmospheric pressure although O2 is 21% of total air

79. EXTERNAL RESPIRATION
PARTIAL PRESSURE DIFFERENCE OF GASES
EXAMPLE
Sea level, pO2 = 160 mmHg
10, 000 ft above sea level, pO2 = 110 mmHg
50, 000 ft ABOVE SEA LEVEL, pO2 = 18 mmHg
HOW DOES THIS AFFECT GAS EXCHANGE?
i.e. pO2 inhaled air
pO2 alveolar air
Less O2 diffuses into blood

80. EXTERNAL RESPIRATION
PARTIAL PRESSURE DIFFERENCE OF GASES
DESCRIBE THE CLINICAL CONDITION.
- It is called High altitude sickness = Acute mountain sickness
SYMPTOMS (All caused by low O2 in blood)
- Shortness of breath, head ache, fatigue, insomnia, nausea and dizziness.

81. EXTERNAL RESPIRATION
2. SURFACE AREA FOR GAS EXCHANGE
- Gas exchange surface area is large (~ 70 m2)
Conditions that surface area for gas exchange.
a) Pulmonary disorder that functional surface area between alveolar and capillary
membrane.
EFFECT: Rate of external respiration.
E.g. EMPHYSEMA – a pulmonary disease where the alveolar wall is disintegrating.
RESULT: Functional surface area for gas exchange

82. EXTERNAL RESPIRATION
3) DIFFUSION DISTANCE
i.e. total thickness alveolar - capillary membrane ~ 0.5 mm (normal)
FACTORS THAT COULD CHANGE DIFFUSION DISTANCE
a) Thickness alveolar-capillary membrane
i.e. Alveolar and/ or capillary membrane disease
b) Diffusion distance between alveolar air space to haemoglobin in RBC
(NORMALLY) Capillary is narrow so RBC passes in a single file
(Means) There is a short distance of diffusion between air spaces to haemoglobin in RBC

83. EXTERNAL RESPIRATION
Conditions that diffusion distance
1) Pulmonary oedema i.e. Fluid builds-up in pulmonary capillary
RESULTS: Diffusion distance

84. EXTERNAL RESPIRATION
4) SOLUBILITY AND MOLECULAR WEIGHT OF GASES
i) O2 has a lower molecular weight than CO2
What we expect to see?
O2 should diffuse 1.2 times faster than CO2 across alveolar-capillary membrane
ii) But what we see?
CO2 is 24 times more soluble than O2

85. 4) SOLUBILITY AND MOLECULAR WEIGHT OF GASES
Net effect- CO2 diffuses 20 times faster than O2
SIGNIFICANCE of these observation
- If any diffusion abnormality in the alveolar-capillary membrane (e.g. emphysema or
pulmonary edema);
a) We first see symptoms of low blood O2 developing first
b) We later see symptoms of CO2 retention

86. INTERNAL RESPIRATION
• DEFINITION – exchange of CO2 and O2 between blood capillaries and tissue
cells.
i.e. internal respiration

87. Henry’s Law
"At a constant temperature, the amount of a given gas that dissolves in a given type and
volume of liquid is directly proportional to the partial pressure of that gas in equilibrium
with that liquid.“
i.e. the solubility of a gas in a liquid is directly proportional to the partial pressure of the
gas above the liquid”
•Henry's law can described mathematically (at constant temperature) as
p = kHc
p - partial pressure of the solute in the gas above the solution, c - the concentration of the
solute,
kH - is a constant with the dimensions of pressure divided by concentration. Henry's law
constant, depends on the solute, the solvent and the temperature.

88. INTERNAL RESPIRATION- at tissue (internal respiration site (O2)

89. INTERNAL RESPIRATION- at tissue (internal respiration site (CO2)

90. TRANSPORT OF OXYGEN
WHAT IS THE SIGNIFICANCE OF THIS?
i) At pulmonary capillary (external respiration site) – O2 is taken-up by the pulmonary
capillary.
PULMONARY
CAPILLARY

91. PARTIAL PRESSURE GRADIENTS & GAS SOLUBILITY

92. TRANSPORT OF OXYGEN
ii) At tissues (internal respiration sites ) – O2 is taken-up by tissue cells.
Tissue cell
Tissue cell

93. TRANSPORT OF OXYGEN
DESCRIBE OXYGEN CARRIAGE IN BLOOD?
~ 1.5% of O2 dissolved in plasma take part directly in internal respiration
INTERNAL RESPIRATION – defined as the exchange of CO2 and O2 between blood
capillaries and tissue cells
~ 98.5% combines to haemoglobin, (Hb) in blood indirectly take part in internal
respiration.
EXAMPLE
100mL of blood contains 20 mL
0.3 mL dissolves in plasma
19.7 mL is bound to Hb

94. Relationship between Hemoglobin and oxygen partial pressure
• Total blood volume adult male (5.5 liter)
• 5.4 million RBC per microliter of blood
• ~ 280 million Hb in RBC
WHAT DOES % SATURATION OF Hb MEAN?
i.e. % of HbO2 in total HB
• ”fully” saturated Hb - means all deoxyHb is converted to oxyHb
• “partially” saturated Hb - means Hb is a mixture of oxyHb and deoxyHb

95. TRANSPORT OF OXYGEN
• DESCRIBE HAEMOGLOBIN (Hb) MOLECULE?

96. TRANSPORT OF OXYGEN
• Relationship between %saturation Hb and pO2 is shown in the oxygen-Hb dissociation
curve
• When pO2 is high, large amounts of O2 binds to Hb ~ 100% saturated. E.g. pulmonary
capillary, pO2 is high, a lot of O2 binds to Hb
• In tissue capillary pO2 is low, haemoglobin unloads its oxygen bounded to Hb, O2 dissolve
in blood plasma which in turn is taken up by tissues
• Haemoglobin is ~ 75% saturated with O2 at a pO2 of 40mmHg (average pO2 of tissue cells
of a person at resting condition)

97. TRANSPORT OF OXYGEN
• WHICH PART OF THE OXYGEN IN BLOOD TAKES
PART IN INTERNAL RESPIRATION?
- O2 dissolved in blood (~1.5%)
i.e. meaning, the 98.5% of O2 bounded to Hb is NOT freely available for internal
respiration.
• HOW DOES THE O2-BOUNDED TO Hb(Oxy-Hb complex)
BE MADE AVAILABLE FOR INTERNAL RESPIRATION?
i.e. If pO2 is high more O2 is bounded to Hb
If pO2 is low O2 is released from OxyHb complex

98. O2–Hb Dissociation curve
• COMMENTS FROM O2 – Hb DISSOCIATION CURVE
1. pO2 is high Hb binds to large amounts of O2
pO2 is low oxy-Hb releases O2
2. In resting tissues, pO2 ~ 40mmHg, and haemoglobin is still O2 saturated ~ 75%
What does this mean?
~ 25% of O2 bounded to oxy-Hb is used in tissues it is sufficient to meet their metabolic needs.

99. O2–Hb Dissociation curve
- In resting tissues, pO2 ~ 40mmHg, and haemoglobin is still O2 saturated ~ 75%

100. O2–Hb Dissociation curve
• COMMENTS FROM O2 – Hb DISSOCIATION CURVE
3. At pO2 between 60 -100mmHg, oxy-Hb is still around 90% or more saturated with O2.
SIGNIFICANCE;
(i.e. lung disease, heart disease and high altitude) Conditions where pO2 is as low as 60mmHg,
Hb is still nearly saturated with O2 (i.e. ~ 90% at least)

101. O2–Hb Dissociation curve
- At pO2 between 60 -100mmHg, oxy-Hb is still around 90% or more saturated with O2

102. O2–Hb Dissociation curve
• COMMENTS FROM O2 – Hb DISSOCIATION CURVE
4. At pO2 between 20 mmHg and 40 mmHg
i.e. pO2 ~ 40mmHg Hb % is ~ 75%
pO2 ~ 20mmHg Hb % is ~ 35%
- we see a sharp drop in Hb% saturation from 75% to 35%
SIGNIFICANCE;
Muscle contraction, pO2 may drop to < 40 mmHg
So large amounts of O2 is released from Hb
Necessary to match the increase in O2 needed for increased metabolic activity

103. O2–Hb Dissociation curve
• At pO2 between 20 mmHg - 40 mmHg, we see a sharp drop in Hb% saturation from 75% to 35%

104. O2–Hb Dissociation curve
• FACTORS THAT AFFECT % O2 SATURATION OF HB .
• How do these factors work?

105. Other factors affecting the affinity of
hemoglobin for oxygen
1. Acidity
2. Partial pressure of carbon dioxide
3. Temperature
4. 2,3 - biphosphoglycerate

106. O2–Hb Dissociation curve
1. ACIDITY (pH)
EXPLAIN THE EFFECT OF ACIDITY ON AFFINITY OF Hb-02.
EXPLAIN THE BEHAVIOUR AT MOLECULAR LEVEL.

107. O2–Hb Dissociation curve
i.e. increase acidity moves curve to RIGHT

108. O2–Hb Dissociation curve
2. PARTIAL PRESSURE CO2 (pCO2)
EXPLAIN THE EFFECT OF ACIDITY ON AFFINITY OF Hb-02.

109. O2–Hb Dissociation curve
• 3. TEMPERATURE
• Within limits, as the temperature increases, so does the amount of
O2 released from hemoglobin.
• Heat is a metabolic by-product (e.g. produced from contracting
muscle fibers)
• Metabolically active cells need more O2 and release more acids and
heat.
• Acids and heat favor the release of O2 from oxy-Hb
• Fever produces similar results
• Hypothermia (lowered body temperature) cell metabolism slows,
less O2 used by cells, so O2 remains bound to Hb (left shift
saturation curve)

110. O2 –Hb Dissociation curve
i.e. increase temperature moves curve to the RIGHT

111. O2 –Hb Dissociation curve
3. 2, 3 – biphosphoglycerate (2,3-BPG)
DESCRIBE THE EFFECT OF 2,3-BPG ON O2-Hb AFFINITY.
FACTORS THAT 2,3 –BPG in RBC;
i) Certain hormones – thyroxine, epinephrine, norepinephrine, testosterone,
human growth hormone
ii) Living in high altitudes

112. O2–Hb Dissociation curve
i.e. increase in 2,3-BPG moves curve to the RIGHT

113. Oxygen affinity of fetal (Hb-F) and adult (Hb-A) hemoglobin
• Fetal hemoglobin (Hb-F) is different from adult hemoglobin (Hb-A); has a
stronger affinity for O2 – Why? Binds 2,3,BPG less strongly
• At low pO2, Hb-F carries 30% more O2 than maternal Hb-A
Significance: Maternal blood in placenta is quite low. If this special fetal
hemglobin existed, the fetus could suffer hypoxia

114. HYPOXIA
DEFINITION – it is the deficiency of O2 at tissue level.
- There are different types depending on the causes of the hypoxia.
HYPOXIC HYPOXIA – From low pO2 in the arterial blood . E.g. High altitude air
thinner low atm. pressure low PO2.
ANAEMIA HYPOXIA – From little functioning haemoglobin, (Hb) in the blood so
O2 is carried in the blood.
STAGNANT (ischaemia) HYPOXIA – From in blood flow to tissue so O2
delivered to tissues.
HISTOTOXIC HYPOXIA – There is adequate blood delivered to tissue but the tissue is
unable to use it properly.
E.g. presence of toxic agent (E.g. cyanide poisoning) – blocks the metabolic machinery of
cells related to O2 use.

115. CARBON DIOXIDE TRANSPORT
- Carbon dioxide is transported in the body in 3 forms;
i) Dissolved CO2 (7%)
ii) Carbaminohaemoglobin (23%)
iii) Bicarbonate (HCO3
-) (70%)

116. CO2 TRANSPORT
i) Dissolved CO2 , (~7%)

117. CO2 TRANSPORT
ii) Carbaminohaemoglobin (~ 23%)
HOW IT FORMS?

118. CO2 TRANSPORT
FACTORS THAT INFLUENCE AMOUNT OF HB.CO2 IN BLOOD.
- Partial pressure of CO2
SIGNIFICANCE;
H+
H+
H+
H+

119. CO2 TRANSPORT
iii) Bicarbonate (HCO3-)
- 70% of CO2 is transported in plasma as HCO3- ion.
- How does HCO3- form in blood?
RBC

120. SUMMARY OF CO2 TRANSPORT

122. SUMMARY OF EXCHANGE OF CO2 & O2 IN TISSUES
What do we know about gases involved in the Gas exchange?
• O2
- O2 is taken-up in the lungs, carried in the blood by being
bound to Haemoglobin, (Hb) and released in the tissues
• CO2
- CO2 is produced as a by-product of metabolic activities.
- CO2 is taken up into the blood from the tissues and released in the lungs where it is
finally exhaled out into the air.

123. How is 02 released in the tissues?
(step-wise)
1. IN TISSUES

124. HOW DOES O2 ENTERING RBC DISPLACE THE O2 BOUND TO Hb?
Inside the RBC; CO2 uptake results in the reaction below;

125. HALDANE EFFECT
Describe how O2 enters blood from alveolar air and into RBC in blood. (i.e. in the lungs,
there is pO2 so the reverse of Bohr effect happens, called Haldane effect.)
DESCRIBE “HALDANE EFFECT”
(Breathed out)

126. CHLORIDE SHIFT
- As blood picks up CO2,
HCO3- accumulates
inside RBSs (eqn. pushed
to right)
- In exchange, chloride
ions, (Cl-), moves from
plasma into RBCs.
SIGNIFICANCE
This exchange of
negative ions which
maintains the electrical
balance between blood
plasma and RBC cytosol,
is called the chloride
shift.

127. CONTROL OF RESPIRATION
ROLE OF RESPIRATORY CENTER.
- The basic rhythm of respiration is controlled by the Respiratory center,
located in the medulla oblongata.
STRUCTURE OF RESPIRATORY CENTER
- Functionally divided into 3 parts;
1. MEDULLARY RHYTHMICITY AREA
2. PNEUMOTAXIC AREA
3. APNEUSTIC AREA

128. RESPIRATORY CENTER

131. RESPIRATORY CENTER
1) MEDULLARY RHYTHMICITY AREA
LOCATION; - Medulla oblongata
FUNCTION; - a) INSPIRATORY CENTER
- Sets the basic rhythm of respiration
HOW? At the beginning of expiration, inspiratory area is
inactive.

132. RESPIRATORY CENTER
a) EXPIRATORY CENTER
FUNCTION;
i) (QUIET BREATHING)
Expiratory center inactive
i.e. Inspiratory muscle relax
Expiration is passive by passive elastic recoil of lungs and thoracic wall.

133. RESPIRATORY CENTER
b) EXPIRATORY CENTER
FUNCTION;
ii) (ACTIVE BREATHING)
(THEORY)
i.e. recruits the
active expiratory
muscles e.g.

134. RESPIRATORY CENTER
2) PNEUMOTAXIC AREA
LOCATION: Superior Pon region
FUNCTION: Sends inhibitory impulse to inspiratory area.

135. RESPIRATORY CENTER
3) APNEUSTIC AREA
LOCATION: Inferior Pon region
FUNCTION:

136. REGULATION OF RESPIRATORY CENTER
- The respiratory rhythm set by the respiratory center can be modified
by input from;

137. REGULATION OF RESPIRATORY CENTER
1. BRAIN REGIONS
a) CEREBRAL CORTEX - It can influence the respiratory
center by voluntarily altering our breathing pattern.
IMPORTANCE: - Protective function
EXAMPLE: We can refuse to breathe to prevent water or
irritating gases from entering the lungs
LIMITATION: - Build-up of CO2 and H+ in blood can override
our voluntary control over breathing
EXAMPLE:

138. REGULATION OF RESPIRATORY CENTER
1. BRAIN REGIONS
b) HYPOTHALAMUS & LIMBIC SYSTEM
HOW DOES IT WORK?
* Limbic system is the center that control emotional
response

139. REGULATION OF RESPIRATORY CENTER
- The respiratory rhythm set by the respiratory center can be modified
by input from;

140. REGULATION OF RESPIRATORY CENTER
2. RECEPTORS of PERIPHERAL NERVOUS SYSTEM
THAT REGULATE RESPIRATORY CENTER.
How do they regulate the respiratory system?
- By chemical regulation through chemoreceptors
i.e. specifically respond to blood levels of pCO2 and H+ in
blood.
TYPES OF CHEMORECEPTORS
- There are 2 types;
i) CENTRAL CHEMORECEPTORS
ii) PERIPHERAL CHEMORECEPTORS

141. CENTRAL CHEMORECEPTOR
LOCATION – Medulla oblongata in CSF
FUNCTION – Responds to changes in H+ and pCO2
EXAMPLE: pCO2 CO2 is lipid soluble and diffuses
across plasma membrane.
(also blood-brain barrier)

147. pCO2 and H+ in CSF and in blood.
Compare the effects of pCO2 and H+ in CSF and in blood.

148. CENTRAL CHEMORECEPTOR
EFFECT OF THEIR STIMULATION
i.e. Stimulation of inspiratory center
SEE: Rapid and deep breathing called hyperventilation
RESULT:- Exhales out of more CO2
- Until pCO2 and H+ returns to normal.

149. PERIPHERAL CHEMORECEPTOR
- There are 2 types;
i) AORTIC BODY
ii) CAROTID BODY

150. CAROTID BODY
LOCATION: - They are oval nodules in the wall of left
and right common carotid arteries where they
divide into internal and external carotid arteries.
NERVE SUPPLY:- Right and left glossopharyngeal nerve

152. CAROTID BODY

153. AORTIC BODY
LOCATION: - Cluster of chemoreceptor in the wall of arch
of aorta
NERVE SUPPLY:- Vagus nerve

154. PERIPHERAL CHEMORECEPTOR
FUNCTION
- They respond and stimulate respiratory center by
these responses;
a) pCO2 in blood
b) H+ in blood
c) Hypoxia

155. EFFECT OF HYPOCAPNIA ON CHEMORECEPTORS
DOES HYPOCAPNIA (i.e. arterial pCO2 < 40mmHg)
AFFECT CENTRAL AND PERIPHERAL
CHEMORECEPTOR?

156. EFFECT OF HYPOCAPNIA ON
CHEMORECEPTORS
SIGNIFICANCE
- Voluntary hyperventilation to get hypocapnia
EXAMPLE: Divers used to voluntary hyperventilate to
get hypocapnic (i.e. low pCO2) so they can hold their
breathe longer underwater.
Has a great risk for also inducing hypoxia

157. HYPOXIA
WHY IS HYPOXIA DANGEROUS?

158. NEURAL CHANGES DUE TO MOVEMENT
HOW DOES MOVEMENT EFFECT NEURAL CHANGES
THAT CHANGE RESPIRATORY EFFECT.
- i.e. main input from proprioceptors that monitor
movement of joints and muscles
EXAMPLE: During exercise
EFFECT:
i) Sends direct stimulatory impulses to respiratory
center (i.e. inspiratory center of medulla oblongata)
ii) At the same time axons that originate in primary
motor cortex also sends excitatory impulses into
inspiratory area

159. OTHER INFLUENCES THAT HELP
REGULATE RESPIRATION
DESCRIBE
i) BLOOD PRESSURE – indirect relationship
i.e. Sudden BP – rate of respiration
ii) LIMBIC SYSTEM

160. OTHER INFLUENCES THAT HELP REGULATE
RESPIRATION (con’td)

161. OTHER INFLUENCES THAT HELP
REGULATE RESPIRATION (con’td)

162. OTHER INFLUENCES THAT HELP
REGULATE RESPIRATION (con’td)