Unit-1 Respiration.pptx

Shri Shivaji Education Society, Amravati's
SHRI PUNDLIK MAHARAJ MAHAVIDYALAYA, NANDURA RLY.
DIST. BULDANA
Topic: Unit-I: Respiration
Class: B.Sc-III, Sem-V
Mr. Shantaram Bhoye
Assistant Professor & Head
M.Sc., NET-JRF, SET, M.A.(Eng.)

Respiration:
 Respiration is a physiological process occurring in all living organisms.
 Every cell requires energy for carrying out its metabolic activities.
 The cell consumes oxygen during oxidation of substances resulting in the release of
heat and energy and production of carbon dioxide.
 The carbon dioxide acts as a poison for protoplasm unless removed from the body.
 The system designed for exchange of gases between the organism and its environment
is termed the respiratory system.

 Structure of respiratory organs: Gills and Lungs
 Exchange of oxygen and carbon dioxide in an organism takes place at two locations.
 During internal respiration gaseous exchange occurs between blood and cells of the.
 During external respiration, the gaseous exchange takes place between blood and the external
environment.
 Blood serves as transport medium for carrying oxygen to the body cells and carbon dioxide
away from the body cells.
 The body structures which are needed for gaseous exchange between the blood and the
surrounding medium are known as respiratory organs.
 Depending on the type of medium, vertebrates have two principal types of respiratory organs-
gills (for aquatic respiration) and lungs (for terrestrial respiration).

A. Gills:
Gills or branchia are the aquatic respiratory organs of molluscs, many crustaceans, fishes and amphibians.
In addition to gas exchange, gills may serve for loss or gain of water and elimination of salts in marine teleost's.
On the basis of their location, gills are of two types-internal gills and external gills.
In some animals both internal and external gills are present.
I. Internal gills or true gills:
The gills are characteristics of fishes.
In chordate embryo the pharyngeal cavity is connected to the outside by a series of lateral openings called, gill
slits or pharyngeal clefts.
The number of gill slits varies in different chordates- 140 pairs in Amphioxus, 6-14 pairs in cyclostomes, 5 pairs
in most elasmobranchs and bony fishes, and 4 pairs in teleosts.

 Structure of a true gill:
 They are supported by branchial cartilage.
 A single row of lamellae on one side of branchial septum forms half gill called a demibranch
or hemibranch.
 A branchial septum with two attached demibranchs forms a complete gill or holobranch.
 The gill filaments are richly supplied with blood capillaries.
 On the surface of gill filaments exchange of gases through water takes place.
 In bony fishes a bony flap called operculum covers the gills.

II. External or larval gills:
 They are ectodermal in origin and are usually temporary organs found only
in larval stages, therefore they are also called larval gills.
 They occur in the larvae of Lampreys, a few bony fishes, lung fishes and
all amphibians.
 In amphibians, larval gills are absorbed at the time of metamorphosis.
 In some urodels both external gills and gill slits persist during adult life.
 In amphibia gills are absorbed but gill slits persist.
 Gills assume different shapes: pectinate, bipinnate, dendritic, leaf like, etc.
 Each gill consists of a narrow main central axis bearing a double row of
filaments.
 They are vascularized by aortic arches.

B. Lungs:
 Lungs are the respiratory organs of land vertebrates and lung fishes.
 They are very elastic and distensible.
 In vertebrate embryos, lungs developed as a single midventral diverticulum (lung primordium) from
the floor of the pharynx.
 It soon bifurcates into right and left lung buds.
 The undivided common portion develops into windpipe called trachea and larynx which opens into
pharynx through glottis.
 Each lung has an inner endodermal lining derived from embryonic gut, an outer visceral peritoneum
and in between the two, mesodermal mesenchyme containing lymph and blood vessels, nerves,
smooth muscle fibers and connective tissues.

A) The lungs of modern amphibia:
 They are simple hollow sacs a wide central cavity.
 They are elongated in urodels but bulbous in anurans.
 Left lung is usually longer in urodels but rudimentary in
caecilians.
 In frogs and toads lung wall may be divided peripherally by
network of folds or trabeculae into air sacs or alveoli.
 They are richly vascular.

B) Lungs of Reptiles:
 Lungs are reptiles are more complicated.
 In Sphenodon and snakes, lungs are simple thin walled sacs.
 In legless lizards and snakes left lung may be rudimentary or
absent.
 In lizards and turtles, wall of lung is greatly thick and
spongy.
 In Chamaeleon several air sacs arise from the distal portion
of lungs.

C) Lungs of Aves (Birds):
 Avian lungs are unique in architecture and greatly modified due to
their arial mode of life.
 Lungs in birds are small, compact, spongy and have very little
capacity of contraction and expansion.
 They have several thin walled, membranous air sacs.
 The bronchus divides repeatedly forming a network of air
capillaries which do not terminate blindly.
 Due to this the avian lungs become highly efficient organs.

D) Lungs of Mammals:
 They are highly developed, spongy and very elastics.
 They lie in pleural cavities.
 In mammals, externally the lungs are subdivided into lobes.
 Usually there are only two left lobes.
 Right lung has 3 lobes in Man and 4 lobes in Rabbit.
 In some mammals, such as whales, elephant, etc. lungs are
simple and without lobes.
 In monotremes and rats only the right lung is lobulated.
 The bronchus divides repeatedly inside the lung and ultimately
terminate in alveoli.
 They are terminal and blind they always retain certain amount
of residual air after every expiration.
 In mammals, intercoastal muscles, ribs, diaphragm, sternum
and abdominal muscles, all help in breathing.

REGULATIONOF VENTILATIONIN LUNGS:
 During normal quite breathing, inspiration is the active process involving contraction of
diaphragm and external intercoastal muscles, whereas, expiration is the passive process
involving recoiling of lungs and thoracic cage.
 The process of breathing or ventilation of lungs takes place in two distinct steps:
 Inspiration or breathing air into the lungs.
 Expiration or expelling out air from the lungs.
 The movement of air in and out of the lungs occurs because of alternated changes in intra-
pulmonary pressure which is brought about both during inspiration and expiration by the
contraction and relaxation of diaphragm and the intercoastal muscles.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

A) Mechanism of Inspiration:
 During inspiration the size of thoracic cavity increases in all
directions.
 The enlargement is brought about by the flattening of
diaphragm and lifting up of the thoracic basket.
 The diaphragm is formed of a thin sheet of radial muscles
present on the floor of thoracic cavity.
 In resting position it is dome-shaped.
 During inspiration, when the radial muscles contract,
diaphragm flattens and descends down into the abdominal
cavity.
 The ribs are provided with two sets of muscles: external
intercostal muscles and internal intercostal muscles.
 When thoracic cavity increases in size, the pleural cavities
expand and negative pressure is increased in it.
 Now lungs enjoy greater space and expand.

 Mechanism of expiration:
 During expiration, changes occur in opposite
direction.
 Due to relaxation diaphragm and ribs are
brought to their original position and form.
 The diaphragm assumes dome-shaped
appearance.
 Therefore, volume of thoracic cavity and also
the negative pressure of pleural cavities is
reduced.
 This exerts pressure on lungs and the air filled
in the lungs is compressed and is squeezed out.
 Thus, the expiratory phase is a passive event in
breathing.

 Thoracic cage and diaphragm play in respiration varies from animal to animal and from
year to year in the same animal.
 The lungs are not totally emptied by any movement of breathing and some air is left in air
passages.
 Therefore, air is never changed completely during inspiration but is merely freshened up.

Neurophysiologic control of respiration:
 Respiration is an involuntary process and is carried out automatically at a constant rate
under normal conditions.
 The contraction of various respiratory muscles at proper time and with proper strength to
secure adequate gaseous exchange.
Nervous Control:
 Medullary respiratory center (The vital knot of Fluorenes):
 It is situated in the floor of 4th ventricle present in the medulla.
 The center is bilateral and two halves are connected together by commissural neurons.
 The neuron cells of the center are connected to the breathing apparatus with motor as well
as sensory (afferent and efferent) nerves and thus maintain a reflex arch.
 These cells are sensitive to changes in chemical composition of blood and concentration of
Carbon dioxide in plasma.

 Each half of the respiratory center is composed of two parts:
Inspiratory and Expiratory center.
 The expiratory center lies above the inspiratory center.
 Out of the two, only one works at a time.
 According to Pitts, Magoun and Ranson, the inspiratory
center works in normal breathing and expiratory center during
forced expiratory conditions like sneezing, laughing and
coughing.
 In the wall of alveoli of lungs are present stretch receptors or
baroreceptors.
 These are stimulated by the expansion and relaxation of
lungs.
 These receptors propagate inhibitory impulses to the
inspiratory and expiratory parts of the respiratory center
respectively.
 Pneumotaxic center lies in the upper part of pons. It maintains
rhythmicity of respiration.
 It is connected with both inspiratory and expiratory centers.

 Hering-Breuer Reflexes:
 The respiratory center is connected with baroreceptors or stretch receptors present in the
lungs and with the chemoreceptors located in the carotid sinuses and aortic arch through
afferent nerve fibers.
 The inspiratory center propagates motor impulse spontaneously to the external intercostal
muscles and the muscles of diaphragm and also the pneumotaxic center.
 As a result these inspiratory muscles contract and the thorax and lungs expand, filling the
lungs with fresh air.
 This stimulates baroreceptors in the lungs.
 These send inhibitory impulses to inspiratory center, resulting in the relaxation of inspiratory
muscles and expiration follows by the initiation of Hering-Breuer expiratory reflex.
 When expiration is completed, the lungs are deflated and lung baroreceptors are inhibited to
start Hering-Breuer inspiratory reflex.

Chemical Control:
 Rate of breathing is controlled by Carbon dioxide level of the arterial blood and
cerebrospinal fluid.
 Chemoreceptors in the brain, aortic arch and carotid sinus detect carbon dioxide, pH and
Oxygen levels in blood and conduct the information to the brains rhythmic center.
 Carbon dioxide has more effect on breathing than the level of oxygen.
 When Carbon dioxide content of blood drops below a certain critical level, breathing stops
and with the increase in Carbon dioxide level in blood, breathing is accelerated.
 By repeated deep inhalations and exhalations in rapid succession, Carbon dioxide level in
blood falls and breathing becomes normal.

Respiratorypigments:
 The uptake, transport and delivery of Oxygen and Carbon dioxide is done by a group of
colored proteins (chromoproteins) called respiratory pigments.
 These pigments are capable of forming a loose, reversible combination (Oxyhaemoglobin)
with O2 (sometimes with CO2) when exposed to O2 high tension and releasing O2 readily at
lower tensions at level of tissues.
 There are different pigments in different phyla and even several different pigments in the
same phylum or more than one pigment exists in the same animal.
 Respiratory pigments are present in RBCs or in different components of blood.
 Those pigments present outside the blood cells (extracellular fluid) do not function as carriers
of O2 and CO2.

 1. Haemoglobin (Hb):
 It is the most familiar, most efficient respiratory pigment.
 It occurs in majority of vertebrates and invertebrates.
 In invertebrates it is found dissolved in plasma, whereas in vertebrates it its contained in the
special cells, called red blood corpuscles (RBC).
 Its Oxygen carrying capacity is more than other respiratory pigments.
 It is an iron containing compound and consists of an iron-porphyrin compound (heme)
associated with a protein globin.
 Heme is a metalloporphyrin.
 Molecular weight of Hb in RBC 68,000 Dalton.
 In human beings each gram of Hb can combine with 1.3 ml of O2 in normal man.
 100 ml of blood of normal man contains about 16 gms of Hb and in normal woman it is about
14 gms.
 At the level of respiratory surface Hb combines with O2 to form oxyhemoglobin while at tissue
level O2 is released.
 Hb also carries some CO2 in the form of carbhaemoglobin from tissues to the lung alveoli for its
removal to exterior.

2. Chlorocruorin:
 It is the second major respiratory pigment found in blood of invertebrates.
 It is distributed in only four annelid families of the class polychaeta.
 It occurs only in plasma.
 The affinity of chlorocruorin for O2 is equivalent to Hb.
 It is within the same family of worms like sabellidae, serpulidae and amphotritidae some species
have chlorocruorin while other have Hb.
 In serpula both these pigments are present.
 The oxygen carrying capacity of chlorocruorin is 9.1 ml pf O2/100 ml of blood.
 As compared to Hb it has higher affinity for CO2.
 In dilute state it is green in colour while in concentrated form it is red in color.

3. Hemocyanin:
 Hemocyanin is a copper-containing pigment without any porphyrin group.
 It always occurs dissolved in plasma.
 It is the main respiratory pigment occurring in two important phyla i.e. Mollusca and
Arthropoda.
 It is colourless when deoxygenated and blue when oxygenated.
 It is transport O2.

4. Haemerythrin:
 Haemerythrin is a iron containing blood pigment in which iron is directly attached to protein,
as porphyrin is absent.
 It is found in marine invertebrates from sipunculeds, Priapulids, Brachiopods and in Annelid
worm Magalona.
 Pigment appears purple when oxygenated and becomes colourless when reduced.
 It is a protein with M.W. 1,08,000.
 Vascular haemerythrin transports O2 from high O2 pressure of sea water to the coelom and
coelomic haemerythrin and thereby constitute a transfer system between vascular pigments
and tissue.

Transport of Respiratory gases:
Transport of Oxygen:
1. In simple solution:
 Oxygen dissolves in water of plasma and is transported in physical form.
 The amount of oxygen transported in this way is very negligible only 0.3 ml/100 ml of
plasma is transported in this way.
 This is because of poor solubility of oxygen in water content of plasma.
 Still the transport of oxygen in this form becomes important during excess demand of
oxygen by the tissues (muscular exercise).

 2. In combination with Hb:
 Oxygen combines with Hb to form oxyhemoglobin.
 97% of oxygen is transport by this method.
 When the partial pressure of oxygen in the blood is more, Hb combines readily with oxygen
and wherever the partial pressure of oxygen in blood is less, Hb releases oxygen.
 Each molecule of Hb contains 4 atoms of iron.
 Each iron atom combines with one molecule of oxygen.
 The combination of oxygen with Hb is called oxygenation because iron remains in ferrous
form only.
 Hb4 + 4O2 ↔Hb4 O8
 The amount of O2 transported by blood is called oxygen carrying capacity of blood.
 One gram of Hb carries 1.34 ml of oxygen.

Oxygen Hb dissociation curve:
 This curve demonstrates the relationship between partial pressure of Oxygen and the
percentage saturation of Hb with oxygen.
 It explains affinity of Hb for oxygen.
 Normally, Hb is saturated with oxygen only up to 95%.
 This saturation of Hb with oxygen depends upon the partial pressure of oxygen.
 When the partial pressure of oxygen is more, Hb accepts oxygen and when partial pressure
of oxygen is less, Hb releases oxygen.

 The partial pressure of oxygen and saturation of Hb are plotted to obtain the oxygen Hb
dissociation curve.
 Under normal conditions, oxygen Hb dissociation curve is ‘S’ shaped or sigmoid shaped.
 The lower part of the curve indicates dissociation of oxygen from Hb.
 The upper part indicates the acceptance of oxygen by Hb, depending upon the partial
pressure of oxygen.
 PO50 is the partial pressure of oxygen at which Hb saturation with oxygen is 50%.

 The oxygen Hb dissociation curve is shifted to left or right by various factors.
1. Shift to left indicates acceptance of Oxygen by Hb.
2. Shift to right indicates dissociation of Oxygen by Hb.

Bohr’s Effect:
 It is the effect by which the presence of carbon dioxide decreases the affinity of Hb for
oxygen.
 It was postulated by Christian Bohr in 1904.
 Due to continuous metabolic activities the partial pressure of Carbon dioxide increases in the
tissue and partial pressure of oxygen decreases in the tissue.
 Due to this Carbon dioxide enters the blood and oxygen is released from the blood to the
tissue.
 If enhances further release of oxygen to the tissue and the oxygen dissociation curve is shifted
to right. This is due to Bohr’s effect.

Transport of Carbon dioxide:
 Carbon dioxide transported by the blood from tissues to the alveoli.
 Carbon dioxide is transported in the blood in four ways-
 As dissolved form- 7%
 As carbonic acid- negligible
 As bicarbonates- 63%
 As carbamino compounds- 30%
1. Transport of Carbon dioxide as dissolved form:
 Carbon diffuses into blood and dissolves in plasma forming a simple solution.
 Only about 3 ml/100 ml of plasma of carbon dioxide is transported in dissolved form.
2. Transport of Carbon dioxide as carbonic acid:
 Part of dissolved carbon dioxide in plasma combines with the water to form carbonic acid.
 This reaction is very slow and a negligible amount of carbon dioxide is transported in this form.

3. Transport of Carbon dioxide as Bicarbonate:
 About 63% of carbon dioxide is transported as bicarbonate.
 From plasma, carbon dioxide enters the RBCs.
 In the RBCs, CO2 combines with water to form carbonic acid under the action of an enzyme
called carbonic unhydrase.
 It dissociates into bicarbonate and hydrogen ions.
 The concentration of bicarbonate increases more and more in the cell which causes its diffusion
through the cell membrane of RBCs into the plasma.

Chloride shift or Hamburger phenomenon:
 The exchange of chloride ion for a bicarbonate
ion across the cell membrane of RBC is called
chloride shift.
 It was discovered by Hartog Jakob Hamburger
in 1892.
 Chloride shift occurs when CO2 enters the blood
from the tissues.
 Plenty of sodium chloride is present in plasma.
 It dissociates into sodium and chloride ions
when the negatively charged bicarbonate ions
move out of RBC into the plasma, the
negatively charged chloride ions move into the
RBC in order to maintain the ionic balance.
 The bicarbonate ions combine with sodium ions
in the plasma and form sodium bicarbonate
which is transported by the blood.
 The hydrogen ions dissociates from carbonic
acid are buffered by Hb inside the RBC.

Reverse chloride shift:
 The process by which the chloride ions are moved back into plasma from RBCs is called
reverse chloride shift.
 When the blood reaches the alveoli, NaHCO3 dissociates into NA+ and HCO3 ions.
 Bicarbonate ion moves into RBC, which makes Cl- ion to move out of the RBC into the
plasma, where it combines with sodium and forms sodium chloride.
 At the same time, O2 also enters the RBC.
 It displace H+ from Hb and combines with HCO3 to form H2CO3 which dissociates into
H2O and CO2. Then the CO2 is expelled out.

4. Transport of CO2 as Carbamino
compounds:
 About 30% of CO2 combines with Hb to from
carbamino-haemoglobin or carbhaemoglobin
and it combines with plasma proteins to form
carbamino-proteins.
 carbamino-haemoglobin and carbamino-protein
are together called carbamino compounds.
 CO2 combines with Hb or proteins with a loose
bond so that, CO2 is easily release into alveoli,
where partial pressure of CO2 is low.

Unit-1 Respiration.pptx

More Related Content

Similar to Unit-1 Respiration.pptx

More from Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly. Dist. Buldana

Recently uploaded

Unit-1 Respiration.pptx