Respiration : Respiratory organs and their structure . Mechanism of respiration...Useful for UG PG

1.  Unicellular and small
multicellular
organisms rely on
diffusion for gas
exchange
 Larger organisms
must rely on a
combination of bulk
flow and diffusion
for gas exchange,
i.e., they need a
respiratory system
Respiratory strategies of animals

2. Respiratory systems - physics
Diffusion
Diffusion is the movement
of molecules from a high
concentration to a low
concentration
• Slow over long distances
• Fast over short distances

3. Respiratory systems - diffusion
The Fick equation
J= -DAdC/dx
J = rate of diffusion (moles/sec)
D = diffusion coefficient
A = area of the membrane
dC = concentration gradient
dx = diffusion distance
For gases, we usually use partial pressure rather than concentration

4.  Rate of diffusion will be greatest when the
diffusion coefficient (D), area of the membrane
(A), and energy gradients (dC/dx) are large,
but the diffusion distance is small
 Consequently, gas exchange surfaces are
typically thin, with a large surface area
Respiratory systems - diffusion
J= -DAdC/dx
For gases, we usually use partial pressure rather than concentration

5.  Total pressure exerted by a gas is related to the number
of moles of the gas and the volume of the chamber
 Ideal gas law: PV = nRT
P- total pressure; V- Volume; n – number of moles of gas
molecules; R – gas constant (8.314472 J · K-1 · mol-1)
T – temperature in Kelvin
Gas Pressure

6. Gas Pressure cont.
 Air is a mixture of gases: nitrogen (78%), oxygen (21%),
argon (0.9%) and carbon dioxide (0.03%)
 Dalton’s law of partial pressures: in a gas mixture
each gas exerts its own partial pressure that sum to the
total pressure of the mixture

7. Gases Dissolve in liquids
 Gas molecules in air must first dissolve in liquid
(water or extra-cellular fluid) in order to diffuse
into a cell
 Henry’s law: [G] = Pgas x Sgas

8. Gases Dissolve in liquids
CO2 is much more soluble in water than is O2. Thus, at
the same partial pressure, more CO2will be dissolved in a
solution than will oxygen

9. Diffusion Rates
Graham’s law
 The relative diffusion of a given gas is
proportional to its solubility in the liquid and
inversely proportional to the square root of its
molecular weight:
Diffusion rate  solubility/MW
 O2 32 atomic mass units
 CO2 44 amu
 In air “solubilities” are the same (1000 ml/L at 20oC)
 Oxygen diffuses about 1.2 times faster than CO2
 However, CO2 is about 24 times more soluble in aqueous
solutions than O2. So CO2 diffuses about 20 times faster
than O2 in water

10. Diffusion Rates at a constant
temperature
Combining the Fick equation with Henry’s and
Graham’s laws:
Diffusion rate  dPgas x A x Sgas / X x (MW)
At a constant temperature the rate of diffusion is
proportional to
Partial pressure gradient (dPgas)
Cross-sectional area (A)
Solubility of the gas in the fluid (Sgas)
And inversely proportional to
Diffusion distance (X)
Molecular weight of the gas (MW)

11. Fluid Movement: Bulk flow
 Bulk flow: Mass movement of water or air as the result of
pressure gradients
 Fluids flow from areas of high to low pressure
 Boyle’s Law: P1V1 = P2V2
Temperature and the number of gas molecules remain constant

12. Bulk flow and Boyle’s law
Respiratory systems use changes in volume to cause
changes in pressure!
P1V1 = P2V2 P2V2 P1 = P2
P1V1 = P2V2 P2 P1 = P2 V2

13. Surface Area to Volume Ratio
 As organisms grow
larger, their ratio of
surface area to
volume decreases
 This limits the area
available for
diffusion and
increases the
diffusion distance
J= -DAdC/dx

14. Respiratory strategies of animals
 Unicellular and small multicellular organisms rely on diffusion for gas
exchange
 Larger organisms must rely on a combination of bulk flow and
diffusion for gas exchange, i.e., they need a respiratory system

15. Respiratory Strategies
Animals more than a few millimeters thick
use one of three respiratory strategies
 Circulating the external medium through the body
 Sponges, cnidarians, and insects
 Diffusion of gases across the body surface
accompanied by circulatory transport
 Cutaneous respiration
 Most aquatic invertebrates, some amphibians, eggs of birds
 Diffusion of gases across a specialized respiratory
surface accompanied by circulatory transport
 Gills (evaginations) or lungs (invaginations)
 Vertebrates

16. Most animals have a circulatory system
Respiratory
surface
Tissue
Circulatory
system
External
medium
 Diffusion of gases across a specialized respiratory
surface accompanied by circulatory transport
O2
O2

17. Cutaneous respiration
Respiration through skin
Found in some aquatic invertebrates and a few vertebrates
Disadvantages: relatively low surface area
Conflict between respiration and protection
Salamander
Annelid Lake Titicaca frog

18. External gills
Gills originate as outpocketings (evaginations)
• Advantages: high surface area, exposed to
medium
• Disadvantages: easily damaged, not suitable in
air
Polychaete
Salamander

19. Internal gills
• Advantages: High surface area, protected
• Disadvantages: not usually suitable in air

20. Lungs
Originate as infoldings (invaginations)
• Advantages: High surface area, protected, suitable
for breathing air
• Disadvantages: not suitable in water

21. Respiratory System –
Functions
Basic functions of the respiratory system are:
1. provides oxygen to the blood stream and
removes carbon dioxide
2. enables sound production or vocalization as
expired air passes over the vocal chords
3. enables protective and reflexive non-
breathing air movements such as coughing
and sneezing, to keep the air passages clear
4. control of Acid-Base balance
5. control of blood pH

25. Chelicerates - Spiders and scorpions
Have four book lungs
 Consists of 10-100
lamellae
 Open to outside via
spiracles
 Gases diffuse in and out
Some spiders also have a
tracheal system – series of
air-filled tubes
 Oxygen diffuses into the
trachea and dissolves in
the interstitial fluid
before diffusing into the
tissues

28. Accessory respiratory
structure in Anabas / Clarius

29. The Indian climbing perch Anabas scandens (Fig. 44.6) has
special air chambers above the gills, where three concentrically
folded bony laminae, called labyrinth form organs are
developed from the first epibranchial bone on each side. Their
covering vascular mucous membrane brings about respiration.
Anbas is so dependent
on air that even in
water it comes to the
surface to gulp air and
it is asphyxiated if
prevented from doing
so. It can survive for
long periods on land
and makes excursions
by means of its many
long spines on the
operculum and ventral
fins

31. The catfish Clarias, found in Indian and African rivers, has
a pair of supra-branchial organs, each lying on one side
and divided into two parts,
a highly branched arborescent organ formed from second
and fourth branchial arches,
and a vascular sac of the branchial chamber which encloses
the arborescent organ.
Several gill-fans formed by coalescing of gill-filaments close
the entrance of the suprabranchial organ.
Air is taken into the organ through the mouth continuously,
and Clarias cannot only live outside water for several hours
but it can move along on damp grass.
Accessory respiratory organs are found generally in tropical
fishes of amphibious habit, they are devices for sustaining
life out of water.

32. Lungs of frog
 A frog may also breathe much like a
human, by taking air in through their
nostrils and down into their lungs.
 The mechanism of taking air into the
lungs is however sligthly different
than in humans.
 Frogs do not have ribs nor a
diaphragm, which in humans helps
serve in expand the chest and thereby
decreasing the pressure in the lungs
allowing outside air to flow in.

33.  In order to draw air into its mouth
the frog lowers the floor of its
mouth, which causes the throat to
expand. Then the nostrils open
allowing air to enter the enlarged
mouth.
 The nostrils then close and the air
in the mouth is forced into the
lungs by contraction of the floor
of the mouth.
 To elimate the carbon dioxide in
the lungs the floor of the mouth
moves down, drawing the air out
of the lungs and into the mouth.
Finally the nostrils are opened and
the floor of the mouth moved up
pushing the air out of the nostrils.

34. Respiratory System in
Pigeon
 Avian flight demands more supply of oxygen. As
pigeon is a flighting animal the respiratory system of
pigeon is more complicated than other groups of
vertebrates.
 Respiration is by means of lungs. Lungs are small in
size and supplemented by air sacs which reduce the
body weight. Expiration is more active than
inspiration.
 There is no muscular diaphragm to separate thoracic
chamber from abdominal chamber.
 The respiratory system of pigeon includes respiratory
organs, air sacs and respiratory tract.

35. There are nine air sacs.
One median
interclavicular,
One pair of cervical,
Two pairs of thoracic
One pair of abdominal
air sacs.
Flow-through
ventilation,

38. The air sacs help to maintain high body temperatures.
They make the body lighter and help in flight.
(I) RESPIRATORY TRACT:
Respiratory tract includes External
nares, Larynx, Trachea, Syrinx and
Bronci.
(i) External Nares and Nasal
Passages:
There are presences of paired slit
like openings; external nares are
situated at the base of the beak. The
openings are surrounded by soft
sensitive membranous cere or
operculum. Nostril leads into short
nasal sac or nasal passages.
Nasal sac opens into the pharynx
through internal nares situated
dorsal to palatal folds.

39. (ii) Larynx:
There is a slit like opening situated on
the floor of buccopharyngeal cavity
called Glottis. It is just behind the
root of the tongue. IT communicates
Pharynx to the Larynx.
Larynx is the anteriorly expanded
chamber at the anterior most margin
of trachea. It is greatly reduced in
birds. Larynx is supported by a
triangular cricoids cartilage. There are
no vocal cords in Larynx.

40.  (iii) Trachea:
Trachea is a fairly long, flexible
cylindrical tube running backward
through the neck; ventral to the gullet
pierced into the thoracic cavity
beneath the oesophagus and is
displaced to the left in the middle
region by the crop.
On entering into thoracic cavity
trachea diatates to form syrynx.

41. (iv) Syrynx:
Syrynx is the sound producing organ of pigeon called sound box. It is a wide cavity
supported by tracheal rings. Wide spacious part of syrynx is called tymopanum mucus
membrane of which forms cushion like thickening on either side.
At the junction of both bronchi, there is a bar of cartilage called pressulus.
It supports a small, vibratory crescentic or semi-lunar membrane which supplements the
vibration of tympanic membrane resulting sound production when air passes through it.
(v) Bronchi:
There are two bronchi continued from the syrynx running for a short distance enters into
the lungs. Each bronchus made up of cartilaginous rings.
The part of bronchus which enters up to the posterior end of lungs is called
mesobronchus.
These is no brounchioles. They send their branches to the air sacs in form of secondary
bronchi and tertiary bronchior para bronci.

42. (I) Breathing at rest:
When the bird is in rising position, its sternum rises and
falls alternately by the activities of abdominal inter costal
muscles.
i) During inspiration, the sternum lowered, the air sacs
expand and lungs remain compressed.
ii) As a result of which fresh air enters through the nostril,
trachea and mesobronchus to the posterior air sacs.
iii) At the same time the air present in lungs moves to the
anterior air sacs.
iv) During expiration the sternum is raised air sacs
compressed and the lungs expand.
v) Air containing O2 moves from posterior air sacs to the
lungs.
vi) Gaseous exchange takes place, then the air passes to
the anterior air sacs and pass out through the
mesobronchus and respiratory tract to outside.

43. (II) Breathing during Flight:
 During flight, the skeleton is kept
rigid and ribs become immovable
trace the wings. The air goes in and
out of the lungs by elevation and
depression of the back with the
synchronized with the strokes of the
wings. The faster a bird flies more
rapidly it respires. This respiration
takes place by –
i) Increasing and decreasing of the
thoracic and abdominal cavities by
movement of pectrol flight muscles.
ii) Pressure of viscera against the sacs
which contract and expand alternately
and cause air to circulate back and
forth in the lungs.
iii) As the bird flies more rapidly the sternum moving away and towards the vertebral column. Thus air
circulation and gaseous exchange become more rapid.
Presence of anastomising and inter-communicating air capillaries in avian lungs accompanied by the
presence of ait sacs, increase the efficiency of breathing to a higher degree.

44. Respiratory System
Principal Organs

45. Physical Properties of the Lungs
 Ventilation occurs as a result of
pressure differences induced by
changes in lung volume.
 Physical properties that affect lung
function:
 Compliance.
 Elasticity.
 Surface tension.

46. Compliance
 Distensibility (stretchability):
 Ease with which the lungs can expand.
 Change in lung volume per change in
transpulmonary pressure.
DV/DP
 100 x more distensible than a balloon.
 Compliance is reduced by factors that
produce resistance to distension.

47. Elasticity
 Tendency to return to initial size after
distension.
 High content of elastin proteins.
 Very elastic and resist distension.
 Recoil ability.
 Elastic tension increases during
inspiration and is reduced by recoil
during expiration.

48. Surface Tension
 Force exerted by fluid in alveoli to resist
distension.
 Lungs secrete and absorb fluid, leaving a very
thin film of fluid.
 This film of fluid causes surface tension.
 Fluid absorption is driven (osmosis) by Na+ active
transport.
 Fluid secretion is driven by the active transport of
Cl- out of the alveolar epithelial cells.
 H20 molecules at the surface are attracted to
other H20 molecules by attractive forces.
 Force is directed inward, raising pressure in
alveoli.

49. Surfactant
 Phospholipid produced by
alveolar type II cells.
 Lowers surface tension.
 Reduces attractive forces of
hydrogen bonding by
becoming interspersed
between H20 molecules.
 Surface tension in alveoli is
reduced.
 As alveoli radius
decreases, surfactant’s
ability to lower surface
tension increases.
 Disorders:
 RDS.
 ARDS.
Insert fig. 16.12

50. Respiratory System –
Lungs

51. Respiration Process
A collective term for the following processes:
 Pulmonary Ventilation
Movement of air into the lungs (inspiration)
Movement of air out of the lungs (expiration)
 External Respiration
Movement of oxygen from the lungs to the blood
Movement of carbon dioxide from the blood to the lungs
 Transport of Respiratory Gases
Transport of oxygen from the lungs to the tissues
Transport of carbon dioxide from the tissues to the lungs
 Internal Respiration
Movement of oxygen from blood to the tissue cells
Movement of carbon dioxide from tissue cells to blood

52. Pulmonary Ventilation
The intercostal muscles and the diaphragm work together
Inspiration, or inhalation – a very active process that requires input of energy
Air flows into the lungs when the thoracic pressure falls below atmospheric
pressure. The diaphragm moves downward and flattens while the intercostal
muscles contract.
Expiration, or exhalation – a passive process that takes advantage of the recoil
properties of elastic fibers Air is forced out of the lungs when the thoracic
pressure rises above atmospheric pressure. The diaphragm and expiratory
muscles relax.

53. Pulmonary Ventilation -
Volumes

54. 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.

55. Formulas – Capacities
 Vital Capacity – maximum amount of air that
can be expired after taking the deepest
breath possible (VC = TV + IRV + ERV)
 Inspiratory Capacity – maximum volume of
air that can be inhaled following exhalation
of resting tidal volume (IC = TV + IRV)
 Functional Residual Capacity – volume of air
remaining in the lungs following exhalation
of resting volume (FRC = ERV + RV)
 Total Lung Capacity – total volume of air
that the lungs can hold (TLC = VC + RV)

56. Control of Respiratory
System
 Respiratory control centers –
found in the pons and the medulla
oblongata
 Control breathing
 Adjusts the rate and depth of
breathing according to oxygen and
carbon dioxide levels
 Afferent connections to the
brainstem
 Hypothalmus and limbic system
send signals to respiratory control
centers

57. Gas Exchange
and Transport
 Alveolar Gas Exchange – the loading of oxygen and
the unloading of carbon dioxide in the lungs
 Oxygen is carried in the blood bound to hemoglobin
(98.5%) and dissolved in plasma (1.5%)
 Carbon dioxide is transported in three forms
 Carbonic acid – 90% of carbon dioxide reacts with water to form
carbonic acid
 Carboamino compounds – 5% binds to plasma proteins and
hemoglobin
 Dissolved gas – 5% carried in the blood as dissolved gas

58. Systemic Gas
Exchange
 Carbon dioxide loading -The Haldane
Effect – the lower the partial pressure of
oxygen and saturation of it in hemoglobin,
the more carbon dioxide can be carried in
the blood
 Oxygen unloading from hemoglobin
molecules

59. Blood Chemistry &
Respiratory Rhythm
Hydrogen ion concentrations -
strongly influence respiration
Carbon dioxide concentrations -
strongly influence respiration
Oxygen concentrations - have little
effect on respiration