CHAPTER 8.2: RESPIRATORY SYSTEM
283
Chapter: 8.2
Respiratory System
Learning Objectives
This chapter discusses meaning of respiration, respiratory system and
different organs associated with that system, mechanism and physiology of
respiration, structure of the lungs, artificial respiration, and some terms
related to the mechanism of ventilation.
Pedagogic Approach
The following pedagogic approaches can be adopted;
i. Discuss with the students with the related term of respiration and
ii. differentiate between internal and external respiration.
iii. Describe the different parts of the system
iv. Describe the mechanism and physiology of respiration making
discussion.
v. Discus and make the student about pulmonary air volumes, Bohr’s
effects, Hamburger’s phenomenon, or chloride shift
vi. Let the students work together to make charts and find out different
parts of the system.
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Respiratory system
Respiration is the metabolic process of oxidation of food leading to the formation of energy
(internal respiration). You have to learn the topic in Botany, but, in Zoology, we are learning
the external respiration which is the process of exchange of gases. Fresh gases containing
Oxygen is taken up by the lungs while Corban dioxide is removed from the body. This is also
called as ventilation.
Fig. Respiratory System
8.2.1 Types of Respiration
Internal respiration; This is the oxidation of food to release energy and is a metabolic process.
It takes place in mitochondria of cells and tissues and energy thus produced is stored in the
form of ATP. When ATP break down to ADP and AMP, energy is released to the cells and they
can make the use of them.
The internal respiration is of two different types; they are;
1. Anaerobic; The respiration without Oxygen is anaerobic and each molecule of glucose
produces 2 ATP or 56 kilocalories of energy. In higher animals, the product is lactic
acid which is produced during hard and strenuous exercise.
C6H12O6
C3H6O3(Lactic acid) + 2ATP (56 Kcal)
However, the product are Ethyl alcohol and carbon dioxide among fungi and some
bacteria.
C6H12O6
energy
2CH3CH2OH (Ethyl alcohol + CO2 +2ATP or 56 Kcal of
2. Aerobic respiration; The respiration with air or Oxygen is Aerobic which is completed
CHAPTER 8.2: RESPIRATORY SYSTEM
285
in three steps, they are; Glycolysis, Kerb’s Cycle and Terminal oxidation. This is an
efficient oxidation of food producing much energy in well-developed higher organism
including human beings.
C6H12O6 + 6O2
6CO2 + 6H2O + 28ATP or 686 Kcal
Anaerobic respiration
Aerobic respiration
The respiration takes place without Oxygen
The respiration takes place with Oxygen
The respiration takes place in strenuous
exercise
The respiration takes in normal condition
The respiration is seen in anaerobic bacteria,
fungi, in strenuous exercise among
advanced animals
The respiration is seen in
advanced animals and plants
The products are Carbon dioxide, Ethanol, or
Lactic acid.
The products are Carbon dioxide and
Oxygen
among all
Ventilation or external respiration; External respiration is the process of gaseous exchange in
the lungs. The body of blood absorbs oxygen and expels Carbon dioxide to the alveolar spaces
by diffusion.
This physical process doesn’t produce
energy, but, loses during the mechanism.
Ventilation or external respiration;
Tissue or internal respiration;
It is physical Process of breathing
It is a chemical process
It takes place in alveoli of lungs, outside the
cells (extra cellular process)
It takes place inside all the cells and
tissues.( intra cellular process)
It doesn’t produce energy, but loses it
It generates energy
There are no specific types of it.
Aerobic and anaerobic respirations are the
types of it.
The mechanisms are different in animals
The mechanisms are the same in all
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system comprises of different organs and is responsible for the exchange of gases in the
lungs so that the blood can get Oxygen and release Carbon dioxide and the system includes;
Nostrils and nasal chambers; They are the anterior most parts of the system. Nostrils are a
pair of openings leading to the respective nasal chambers (right and left) separated by septum.
The chambers open in naso-pharynx through internal nares. Nose is supported externally by
nasal bones and terminal cartilages. The septum, however is supported by vomer and ethmoid
bones.
The cavities are internally lined by goblet cells embedded in ciliated cells. The major functions
of the parts are;

The olfactory cells help for smell

The mucus produced by goblet cells
moisten and humidify air for
breathing by decreasing surface
tension.
Fig. Nostrils and nasal chambers

Mucus produced by the goblet cells help catching dust particles, bacteria, pollen
grains, and other micro- organisms.

The ciliated cells act as a broom sweeping those particles out making the lungs clean
Pharynx; This is the junction of seven different passages (2 openings from Eustachian tubes
of ears, one from each side, 2 internal nares from nose, another from mouth, one more leading
to gullet of esophagus and the last one leads to the lungs through glottis) there are three
major parts in the organs which are;

Nasopharynx; It is the opening of
nasal chambers having openings
called internal nares, these nares
are closed by uvula during
swallowing of food.

Oropharynx; It is the middle part
located just behind the mouth, a
hollow tube of 12 cm up to
trachea, including last 1/3rd part
of tongue.

Laryngopharynx; The pharynx
opens into the larynx through the
glottis which is guarded by leaf
like epiglottis that prevents the
flow of food to the trachea or to the lungs. this is the lowermost part of the organ
extended from 4th to the 6th cervical vertebrae and helps in respiration. This portion is
called sound box as it produces vocal
Fig. Pharynx
sound.
CHAPTER 8.2: RESPIRATORY SYSTEM
287
How the sound is produced in humans?
The laryngo-tracheal cavity has 9 different cartilages (3 thyroid, cricoid and
epiglottis, one each and arytenoid, corniculate and cuneiform, one pair each), the
vocal cords extend between the thyroid and arytenoid cartilages. When the
cartilages are pulled apart, the cords are stretched and expulsion of air from the
lungs vibrates the cords producing basic vocal sound which is modified by the
tongue.
Males have long and large sound box having longer vocal cords and produce
harsh voice having low pitch but the females and children have small sound box
having short vocal cords producing high pitch or shrilled sound.
3. Larynx: It is cartilaginous muscular tube that lies at the anterior part of trachea. Its wall is
supported by four cartilages. These are a basal ring-like cricoid cartilage, a large C-shaped
thyroid cartilage and two pyramidal arytenoid cartilages that give attachment to the vocal
chords. Within the larynx, there are two fibrous cords called vocal cords enclosing glottis
at the middle. The vocal cords are longer in male, thus pitch of male is lower. When air is
forced from lungs through glottis, vocal cords set in vibration so sound is produced.
Hence, larynx is also called as voice box. Before puberty, it is equal in size in both the
sexes, but, after puberty, it becomes large in males mainly due to enlargement of thyroid
cartilage which is called Adam's apple.
Epiglottis
Hyoid bone
Thyroid
Thyroid
Croniculate
Arytenoid
Cricothyroid
Cricoid
Trachea
(a)
(b)
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Fig: 5.3: Structure of Larynx (a) Anterior View, (b) Posterior View
Adam’s apple; It is the enlargement of thyroid cartilages making out-bulging popularly known as
Adam’s apple that makes the sound harsh among males.
Trachea or wind pipe; The tube extended from trachea to the thoracic cavity leading up to the
lungs. The tube runs parallel to the esophagus, just to the front of it. The tube is 2 cm in diameter
and can be up to 15 cm in length. C shaped cartilages support the part form the front but are
incomplete at the back. They prevent the organ from being collapsed internally, the tube is lined
with pseudo-stratified epithelium having goblet and ciliated cells. Moreover, they have connective
tissue with elastic and collagen fibers.
Bronchus; The trachea divides into two parts penetrating to the respective side, to the left and right
lungs. The right bronchus is wider but shorter than the left one. They have similar histology to the
trachea.
Bronchioles; The bronchus in each side divides re-divides into number of smaller branches called
bronchioles they have similar histology to the earlier parts. The cartilage is, however is gradually
lost and smooth in this part, not C shaped.
Alveolar ducts; These are the smaller branches of bronchioles leading up to the functioning units,
alveoli or alveolar sacs. These tubes are devoid of cartilages, and goblet cells, but internally lined
by ciliated cells.
Trachea
Cartiliginous rings
Primary bronchus
Secondary
b
h
Tertiary bronchus
Bronchioles
Alveolar duct
Alveolar sac
Central passage
Air sacs
CHAPTER 8.2: RESPIRATORY SYSTEM
289
Fig. 5.4: Respiratory tract inside the Human Lung
Alveoli; There are 600 million functioning units of lungs(alveoli) where most of the gaseous
exchange takes place. These tiny sacs are made up of pavement or squamous epithelium and
are highly vascularized (having great many blood capillaries). Externally, they have elastic
bands so that they can expand and recoil.
To pulmonary vein
Blood capillary
Red cell
Epitelium of alveolus
Oxygen enters
red cells
Ventilation
Diffusion of
oxygen
Diffusion of
carbon dioxide
Carbon dioxide escapes
into alveolus
Film of moisture
From pulmonary artery
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Fig: 5.7: Alveolus showing Exchange of Gases
PRINCIPLES OF BIOLOGY XII
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291
The special features of the part are;

They have large surface area of around the size of a lawn-tennis court (about 84
square meter). The larger the area, the greater the gaseous exchange.

They have surfactant present in them which produce surfactant that decreases the
surface tension to increase the exchange of respiratory gases

They can expand and recoil as they have elastic strips in the outer layer helping for
the exchange.

They are highly vascularized having great many blood capillaries and great blood
supply increasing the exchange

They are made up of thin tissue, pavement or squamous epithelium adopted for good
exchange of gases.
Airways
Number
Diameter
Cartilage
Goblet
cells
Smooth
muscles
Cilia
Exchange
of gases
Trachea
1
1.8 cm
yes
yes
yes
yes
no
Bronchus
2
1.2 cm
yes
yes
yes
yes
no
Terminal
bronchiole
48,000
1 mm
no
no
yes
yes
no
Respiratory
bronchioles
300,000
0.5 mm
no
no
no
yes
no
Alveolar
duct
9,000,000
400 µm
no
no
no
no
yes
Alveoli
3,000,000,000
250 µm
no
no
no
no
yes
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The external features of lungs; The left and right lungs are quite different in structure. The
right one has three lobes (superior, middle and inferior) but the left one has two lobes
(superior and inferior). The right lung has cardiac notch to accommodate the heart. The lungs
are externally covered by bi-layered membrane (the outer partial pleura and the inner one
called visceral pleura) having a thin space in between (Pleural space). The layers are
impermeable (air tight), lubricating and cushioning for the easy breathing. The inter pleural
space has 5 cc of pleural fluid recreated by the membranes helping for lubrication (protects
the lungs by reducing the friction).
Larynx
Trachea
Tracheal rings
Apex
Superior lobe
Primary
Median lobe
Cardiac notch
Inferior lobe
Diaphragn
CHAPTER 8.2: RESPIRATORY SYSTEM
293
Fig. 5.2: Respiratory Organs of Man
8.2.2 Mechanism of ventilation or breathing
This is the mechanism of inspiring and expiring of gases. The body takes Oxygen and
removes Carbon dioxide and the mechanism is associated with that. The thoracic muscles, rib
-cage and diaphragm are associated with the process. The breathing rate is around 12 to 16
per minute among adults but the children breath much faster. The process has two steps;

Inbreathing, inhaling or inspiration

Out breathing, exhaling or expiration.
Fig. Mechanism of ventilation or breathing
Inbreathing, inhaling or inspiration
The process is completed in sequent steps which are listed underneath;

The external intercostal muscles contract, but the internal inter coastal muscles relax.

The rib cage is pulled up and out increasing the volume but decreasing the pressure

The diaphragm flattens to increase the volume.

The fresh atmospheric air containing much Oxygen flows from the atmosphere to the
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alveoli of the lungs due pressure gradient.

Gaseous exchange takes place in the lungs by diffusion and the steps are over
Out breathing, exhaling or expiration
This is the opposite process of the previous in which we out -breath the foul gases containing
Carbon dioxide. This is also completed in steps.

The internal intercostal muscles contract, but the internal external coastal muscles
relax.

The rib cage is pulled down and in decreasing the volume but increasing the pressure

The diaphragm tout forming dome shape pushing to the thoracic cavity to decrease
the volume.

The foul gases in the alveoli of lungs containing much carbon dioxide flows from the
alveoli to the atmosphere due to pressure gradient.

Ventilation now is over.
8.2.3 Physiology of respiration
This is the complete process of the exchange of gases which can be divided into the following
steps;
 Inspiration; This is the process of in-taking of fresh gases containing Oxygen from the
atmosphere to the alveoli of the lungs. Then gases move due to pressure gradient. Make
outr to the mechanism of ventilation.
 Intake of Oxygen in alveoli of lungs; Oxygen diffuses in to the blood from alveolar spaces
as the chambers have high partial pressure while the blood capillaries have low partial
pressure of the gas.

Transport of Oxygen to the cells and tissues; Oxygen is transported by RBC in the form
Oxyhemoglobin (98%), while 2% oxygen is transported by water present in the blood
plasma.
H i gh P O 2 i n l u n g s
Hb + O2
O
H bO 2
(100 ml of blood carries about 20 ml of O2.)
CHAPTER 8.2: RESPIRATORY SYSTEM
295
Fig. Exchange of gases


Exchange of carbon dioxide in the alveoli; The exchange done in alveoli due diffusion
alveoli. The concentration of CO2 is higher in the blood that diffuses out into alveolar
spaces having low partial pressure.
Internal or tissue respiration; This is the biochemical processes that involve biochemical
reactions that produce energy. This is the release of energy during cellular respiration
g l u cose + ox y g en
en erg y r el eased
carb on d i ox i d e + w ater
C6H12O6 + 6O2  6CO2 + 6H2O
4.
a.
Transport of CO2 to the alveoli of lungs
Carbon dioxide thus produced due to tissue respiration should be removed quickly from
the body as it is highly toxic. Under normal conditions, 100 ml. of blood transport about
3.7 ml of CO2 in following three ways:
In form of Carbonic Acid: About 7% of CO2 content is transported in form of carbonic acid
by blood. It is formed by dissolution of CO2 in water in RBCs in presence of carbonic
anhydrase enzyme.
CO2 + H2O
b.
Carbonic
anhydrase
H2CO3 (In RBCs)
In form of bicarbonates: Most of CO2 (about 70%) is transported in form of sodium and
potassium bicarbonates by blood. Large amount of H2CO3 dissociates into H+ and HCO3–.
Most of HCO3– diffuse from RBCs into plasma. To maintain electro neutrality, equal
amount of Cl– ions diffuse from plasma into RBCs which is called chloride shift or
Hamburger phenomenon.
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CO2 + H2O
Carbonic
anhydrase
PRINCIPLES OF BIOLOGY XII
H2CO3
H2CO3
H+ + HCO3–
In plasma HCO3– combines with Na+ forming sodium bicarbonate.
c.


Na+ + HCO3–  NaHCO3
Some potassium bicarbonate is also formed in RBCs.
K+ + HCO3–
KHCO3
In the form of Carb-amino Compound: About 23% of CO2 content is removed in this form.
It is formed by combination of CO2 with amino groups of globin (protein).
CO2 + Hb.NH2
Hb.NH.COOH
Exchange of carbon dioxide in the alveoli; The exchange done in alveoli due diffusion in
alveoli. The concentration of CO2 is higher in the blood that diffuses out into alveolar
spaces having low partial pressure of the gas.
Expiration; The foul gas containing Carbon dioxide is breathed out during expiration due
pressure gradient. Refer the mechanism of ventilation.
Pulmonary air volumes;
Figure 37-6 Diagram showing respiratory excursions during normal breathing and during
maximal inspiration and maximal expiration.
CHAPTER 8.2: RESPIRATORY SYSTEM
297
The amount of air breathed during different modes of inspiration and expiration can be
Pulmonary air volumes. They graphically represented as;

Tidal volume or TV; during each effortless breathing, an adult person inhale or exhale 500
cc of air known as tidal volume.

Inspiratory reserve volume or IRV; During each inspiration with effort, an adult inhales
3,000 cc of air addition to the TV known as Inspiratory reserve volume or IRV

Expiratory reserve volume or ERV; During each expiration with effort, an adult inhales
2000 cc of air addition to the TV known as expiratory reserve volume or ERV

Residual volume or EV; Even after the ERV, some air is left in the lungs and the value is
1500 cc.

Vital capacity or VC; the maximum volume of air that can be exchanged during breathing
is known as vital capacity and the value is equal TV+ERV+IRV, which is around 5,500cc

Total lung capacity or TLC; when VC is added with RV, this becomes the maximum air
holding capacity of lungs and called TLC. The value is around 6 to 7 liters.

Dead space; During TV, 500 cc of air is taken in, out of which 350 cc reach alveoli and
alveolar duct. The remaining 150cc stuck in the trachea, bronchus and bronchioles where
gaseous exchange doesn’t take place and the value is known as dead space.
8.2.4 Oxygen dissociation curve
When partial pressures of oxygen at different levels and hemoglobin saturation levels are
experimentally verified to plot in a graph, they make a sigmoid or s shaped curve known as oxygen
dissociation curve. It indicates that the higher the partial pressure of Oxygen, the higher the
hemoglobin saturation rate with Oxygen.
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Fig. Oxygen dissociation curve
Bohr’s effect; Even if the partial pressure of Oxygen is unaltered, Carbon dioxide concentration
affects the oxygen dissociation curve. In low partial pressure of Carbon dioxide, the curve
moves up and left indicating higher saturation levels of Oxygen and Hemoglobin saturation,
but, when the partial pressure of Carbon dioxide increases, the efficiency decreases and line
moves down and right. This indicates the concentration of Carbon dioxide adversely affect the
saturation levels of Oxygen and hemoglobin.
CHAPTER 8.2: RESPIRATORY SYSTEM
299
Fig. Bohr’s effect
Chloride shift or Hamburger's phenomenon;
Fig. Chloride shift
(a) Exchange of O2 and CO2 in pulmonary capillaries (external respiration)
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When the HCO3 - ions are attracted by Na + outside the RBC, H+ ions are left in the cells they in
turn attract the Cl– ions by H+ to RBC and the ions move from blood plasma to the cells known
as Chloride shift or Hamburgers Phenomenon.
Artificial respiration; When a person is drowned or has electric
shock, or an accident affecting medulla oblongata of brain, the
person becomes unconscious and stops breathing and requires
forced mouth to mouth respiration as a primary treatment.
In case breathing is depressed or stopped, then artificial respiration
becomes necessary. There are different methods of artificial
respiration, like mouth to mouth, mouth to nose, tank respirator etc.,
but mouth to mouth respiration is more common.
In mouth-to-mouth respiration, at first patient is placed on a firm
surface on his/her back in such a way that head is slightly lower in
position than stomach. Then mouth and throat are cleared off
from debris. Nostrils of patient are closed and a deep breath is
Fig: 5.9: Mouth to Mouth
blown in mouth by operator until chest is seen to rise. Then
Respiration
patient is allowed to exhale the foul air through the mouth. The
above process is repeated 12-15 times per minute till the
patient coughs and starts breathing.
Respiratory quotient (RQ)
RQ is the ratio of the volume of CO2 produced to volume of O2 consumed over a period of time
in respiration.
Volume of CO2 evolved
RQ =
Volume of O2 absorbed
For glucose RQ is 1, for fat it is 0.7 and for protein it is about 0.9.
Respiratory control; It is a rhythmic, semi-autonomic (a person can hold the
breathing only for short, but, not for long) activity controlled by breathing center at
medulla oblongata. It can be controlled by brain under the conscious mechanism,
but, only for short duration. The medulla oblongata is connected to the intercostal
muscles and diaphragm through spinal cord and spinal respiratory neurons.
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301
Exercise
Group A
Circle the correct one from given alternatives.
(One marks for each)
1. The left and right human’s lungs respectively have;
a. 3 and 2 lobes
b. 3 and 2 lobes
c. 3 and 4 lobes
d. 2 lobes each
2. The trachea in humans and different mammals doesn’t collapse because
a. C shaped cartilaginous rings
b. Bony rings
c. Chitinous rings
d. Silicious rings
3. Most of the carbon dioxide in the body is transported in the form of;
a. Carbaminohemoglobin
b. Carbonic acid
c. Freely in water
d. Bicarbonates
4. When CO2 concentration in blood increases, breathing becomes
a. Faster and deeper
b. Shallow and slower
c. Deeper but slower
d. No affect in the breathing rates
5. Respiratory center of brain is sensitive to
a. Concentration of O2 in the blood b. Concentration of CO2 in the blood
c. Blood accumulation in brain
d. all of these
6. Dissociation curve shifts to the right when;
a. CO2 Concentration increases
b. CO2 concentration decreases
c. O2 Concentration increases
d. Chlorine concentration increases
7. The next process name of Hamburgers phenomenon is;
a. Calcium shift
b. Bicarbonate shift
c. Chloride shift
d. Sodium shift
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8.
PRINCIPLES OF BIOLOGY XII
Lack of pulmonary surface produces
a. Asthma
b. Emphysema
c. Respiratory distress syndrome
d. None
9. Which of these has the lowest value?
a. Expiratory reserve volume
b. Total lung capacity
c. Vital Capacity
d. Tidal volume
10. In expiration, diaphragm becomes
a. flattened
b. stretched
c. tightens
d. dome shaped
11. If a hole is made in the diaphragm of a mammal, the breathing is;
a. stopped
b. decreased
c. increased
d. not affected
12. The contraction of internal intercostal muscles in man causes:
a. inspiration
b. normal respiration
c. aspiration
d. forced expiration
13. Intercostal muscles are found attached with:
a. ribs
b. pelvic girdle
c. backbones
d. clavicle
14. The movement of sternum during inspiration is;
a. Downward and Inward
b. Backward and upward
c. Upward and outward
d. Downward and forward
15. Chloride shift is essential for transport of:
a Sodium
b. Oxygen
c. CO2
d. Carbon monoxide
16. The volume of gas taken during breathing with effort is;
a. Residual volume
b. Vital capacity
c. Tidal volume
d. Inspiratory reserve volume
17. The effortless breathing intake 500 cc of gas in or out known as;
a. Tidal volume
b. Vital capacity
c. Inspiratory reserve volume
d. Total lung capacity
18. Volume of air remaining in lungs after maximal expiratory effort is:
a. Vital capacity
b. Total lung capacity
c. Tidal volume
d. Residual volume
19. The respiratory center that controls the breathing is found in;
a. Cerebrum
b. Medulla oblongata
c. Cerebellum
d. Spinal cord
20. Tidal volume in human beings is:
a. 1500mL
b. 800mL
c. 1200mL
d. 500ml
21. Residual air is the volume of air left in the lungs after expiration with effort, where does the air
remain?
a. Trachea
b. Bronchioles
c. Alveoli of lungs
d. All of them
22. The amount of air breathed with an effort is called:
a. Inspiratory Reserve volume
b. Tidal volume
CHAPTER 8.2: RESPIRATORY SYSTEM
303
c. Total lung capacity
d. Vital capacity
23. How many alveoli are there in a lung?
a. 100 million
b. 200 million
c. 500 million
d. 900 million
24. During moderate aerobic exercise
a. arterial pH decreases
b. blood lactate level increases
c. alveolar ventilation increases
d. all of these
25. In humans, the vital capacity is around;
a. 1500 cc
b. 2500 cc
c. 3500 cc
d. 4500 cc
26. The maximum amount of air that our lungs can normally hold is:
a. Vital capacity
b. Total lung capacity
c. Dead space
d. Tial volume
27. The amount of air that remains in the lungs after the most powerful expiration is termed
a. vital capacity
b. Reserve air
c. Tidal air
d. Residual air
28. How is oxygen transported by blood in vertebrates:
a. in the form of Oxyhemoglobin
b. in the form carbonic acid
c. In the form of carb-oxyhemoglobin d. None of them
29. Hypoxia is a medical condition due to less concentration of Oxygen in the blood which is
caused due to;
a. Higher concentration of CO in the atmosphere
b. Less Oxygen concentration
c. Less concentration of hemoglobin in the blood
d. All of the above
30. How is oxygen transported by blood?
a. absorbed to the surface of RBC's b. combined with hemoglobin
c. dissolved in plasma
d. all the above ways
31. The highest affinity of hemoglobin is with;
a. Carbon mono-oxide
b. Nitrogen
c. Carbon dioxide
d. Oxygen
32. Myoglobin is found in:
a. Blood
b. RBC
c. Liver
d. Muscles
33. How many molecules of oxygen can associate with a molecule of hemoglobin in man?
a. One
b. Two
c. Three
d. Four
34. How much Oxygen is carried by 100 ml of blood?
a. 10mL
b. 20ml
c. 30 mL
d. 40mL
35. Oxygen dissociation curve is;
a. Straight
b. Zig-zag
c. Sigmoid
d. Parabolic
36. Which vertebral organ receives only oxygenated blood?
a. Gill
b. Lung
c. Spleen
d. Liver
37. Exchange of gases between blood and alveolar air in lungs occurs by:
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a. Passive transport
b. Diffusion
c. Active transport
d. Gravity
38. The blood in the pulmonary veins is rich in;
a. CO2
b. O2
c. Both
d. None
39. Oxygen dissociation curve affected by
a. concentration of CO2
b. Temperature of the blood
c. pH value
d. All of them
40. Which of these in blood absorbs O2 in respiration?
a. WBCs
b. Plasma
c. RBCs
d. Platelets
41. Adam’s apple in the male of humans is located in:
a. Thorax
b. Neck region of male
c. Abdomen
d. Head
42. The exact site for the exchange of gases in human lungs is;
a. Bronchioles
b. Trachea
c. Bronchi
d. Alveoli
43. How many lobes are there in the right lungs?
a. 2 lobes
b. 3 lobes
c. 4 lobes
d. No lobes
44. Majority of CO2 is transported in the form of;
a. H2CO3
b. KHCO3
c. NaHCO3
d. Hb.NH.COOH
45. The volume of inspired or expired gas in tidal or effortless breathing is;
a. 500 cc
b. 1,500 cc
c. 1,000 cc
d. 1, 750 cc
46. According to Bohr’s effect, if the partial pressure of CO2 increases, the hemoglobin saturation
rates;
a. Increases
b. Decreases
c. Remains the same
d. All
47. What happens to the number of RBC when we live at high altitudes?
a. Increases
b. Decreases
c. Remains constant
d. None of them.
48. Tracheal rings found in the organ is;
a. C-shaped
b. Circular like rings
c. Long like rods
d. Both, ‘a’ and ‘b’
49. Sound box popularly known as larynx is supported by;
a. 2-cartilages
b. 3-cartilages
c. 4-cartilages
d. 5-cartilages
50. Which of these organs has ciliated cells?
a. Bronchus
b. Heart
c. Uterus
d. Liver
CHAPTER 8.2: RESPIRATORY SYSTEM
305
Group B
Give short answers to the following questions
(5 marks for each)
1. Describe the importance of the respiratory system in Humans.
2. Differentiate between external and internal respiration
3. Draw a well-labeled diagram of the respiratory system in human beings. (No description is
required)
4. Describe the process of transport of Oxygen and Carbon dioxide.
5. What is meant by ventilation? Describe the process in humans.
6. What is chloride shift? Describe in detail.
7. Describe the mechanism of Oxygen transport and its release to cells.
8. Describe the different lobes of the lungs with a well-labeled diagram and describe the covering of
the organ.
9. Differentiate between aerobic and anaerobic respiration.
10. Describe the histology of different parts of the lungs.
Group C
Give long answers to the following questions
(8 marks for each)
1. Describe the physiology of the lungs.
2. How sound is produced in humans? Mention shortly.
3. How the gases (Oxygen and Carbon dioxide) are transported? Describe.
4. Draw a well-labeled diagram of human’s respiratory system and describe the parts.
5. Describe the mechanism of ventilation or breathing.
Activities
1.
Make a sample respiratory system and label the parts with the local materials.
Some Extra Questions for practice.
1. What is meant by respiratory pigment? Name the chemical.
2. Name the tissues that respire anaerobically.
3. Write down the major functions of the nasal chamber.
4. What is the exact site for the exchange of gases.
5. How many cartilages are found in the larynx? Name them.
6. Write down the location of the Larynx.
7. What is pulmonary ventilation? Define the term.
8. What do you understand by different levels of saturation of hemoglobin? What is your
perception if the saturation is said to be 90%?
9. Differentiate between tidal volume and residual volume.
10. Describe the location of intercostal muscles?
11. Define chloride shift possibly with sketch.
12. Describe the oxygen dissociation curve and Bohr's effect with sketch.
1. (b)
11. (b)
21. (d)
2. (a)
12. (d)
22. (a)
Answers to the multiple choice questions
3. (d)
4. (a)
5. (b)
6. (a)
7. (c)
8. (c)
13. (a) 14. (a) 15. (d) 16. (d) 17. (a) 18. (d)
23. (c) 24. (c) 25. (d) 26. (b) 27. (d) 28. (a)
9. (d)
19. (b)
29. (d)
10. (d)
20. (d)
30. (d)
306
UNIT – 8: HUMAN BIOLOGY
31. (a)
41. (b)
32. (d)
42. (d)
33. (d)
43. (b)
34. (b)
44. (c)
PRINCIPLES OF BIOLOGY XII
35. (c) 36. (c)
45. (a) 46. (b)

37. (b)
47. (a)
38. (b)
48. (a)
39. (d)
49. (b)
40. (c)
50. (a)