Free Biology NEET Video Lectures for Breathing And Exchange Of Gases

00:00:02 [Music] so [Applause] [Music] [Applause] [Music] let's get it started so today we will discuss about breathing and exchange of gases and in this topic we will discuss about the complete uh respiratory uh aspect of a human being and side by side we'll compare with some uh some lower organism also that how this restorative system has been evolved in due course of time in the individual now in this topic uh basically one has to understand regarding the gaseous environment like what is happening in

00:01:00 human being when one is uh inspiring some air inside the body cavity and then exhaling out air from uh from the body to the atmosphere now if we start looking and see that every living individual every every living organism require a constant amount of air or some amount of air in order to sustain their day-to-day activity the metabolism the normal anabolism and catabolism of human body and the the organism living organism require a specific amount of air and definitely in different composition in order to

00:01:42 sustain its day-to-day activity and metabolism so we will discuss uh in detail about those gaseous element what is the composition of atmospheric gases element how the body system is uh taking those gaseous element what the mechanism of those exchange of gases from the environment to the body system and then finally we will see that how this mechanism works in case of higher organism taking human being and as example and then we'll go in detail about the function and anatomical physiological aspect of our human lung

00:02:19 so in in next slide if if one can see the composition of atmosphere this is very important in order to understand the respiratory system so the composition of atmosphere mostly comprises of nitrogen so nitrogen is approximately 78 percent of the total atmospheric content then comes the oxygen which is approximately 21 percent and then comes an argon which is another gaseous element coming comprising approximately about 0.9 percent so if you combine and give a total picture it comes about 99.9 percent now uh some trace elements are

00:03:00 also there trust gases gaseous elements are also there uh which comprise the total concentration of those stress elements are uh test gases are approximately 0.1 percent now this 0.1 percent includes methane helium neon ozone nitrous oxide and carbon dioxide now in this topic we will try to cover mostly oxygen and carbon dioxide now these are the two gaseous component we will try to focus our whole discussion of this respiratory system now having said that these these gases elements are present

00:03:41 in the atmosphere now one can ask an obvious question that if nitrogen percentage is 78 percent why not this gaseous element is exchanged why not this element is important for us now as such if we consider this nitrogen this is a incredibly inert material it don't want to change itself so whatever we are breathing nitrogen in is coming out also very layers kind of fluctuation on modulation and between the x inspired air and the expired out air so inspire is something which is we are taking in

00:04:17 and expired is something which we are breathing out so this nitrogen is very inert it is very stable in nature and that's why this atmospheric nitrogen is not used in normal physiological aspect in human body now second comes the carbon dioxide now carbon dioxide percentage is also very less but the acid this carbon dioxide and oxygen is very important and critically regulated in respiratory system and then we will discuss this to gaseous composition in in aspect of their respiratory passage and movement and all

00:04:55 now having said that these are the gaseous element or gaseous uh component in the atmosphere if you start looking in our next slide uh the step of respiration now these are some critical steps of respiration so what is happening in in this step of respiration that we are focusing our content so suppose the air is coming from the atmosphere and coming into the system and the system is body either human body or the body of lower vertebrate invertebrates and other organism living organism now this com

00:05:34 this composition of air is coming inside to take this composition inside the body cavity i am just giving an example of human being here right now so what we are having is this cavity we call it chest cavity in normal and in case of biological term we call it uh thoracic cavity now this thoracic cavity which is which is comprising this uh kind of equipment which we will learn later as lung is basically require a ventilation right so what will happen eventually this will undergo a pulmonary ventilation anything related to

00:06:10 pulmonary so the terminology if you go and check the slide again the terminology is called pulmonary pulmonary is very specific term related to lungs so anything related to lungs we called it pulmonary now this pulmonary ventilation is very important in order to take the oxygen content inside the body cavity inside our human body now the next step is after getting this air inside the body we need to get it diffused now diffusion is another process where the oxygen content on carbon dioxide contained whatsoever is

00:06:49 there is coming in the body either it will be diffused into the body system or from the body system it will diffuse out um into into into the into the cavity now we will again discuss this one this is just to give you a better understanding that what we will discuss in further lectures so the next step is diffusion and next after diffusion so suppose we have air in either in the blood vessel and then we have air in lungs so we have air in lungs and we have air in blood now this uh air requires transportation

00:07:33 now this transportation is the next phenomena so then the whole passage a whole content oxygen contained and carbon dioxide contained is basically transported through these two uh area after diffusion and later on are very important to maintain this all process right so the first one is pulmonary ventilation next one is diffusion and the third one is transportation to regulate this we need to regulate the ventilation we need to really regulate the whole respiratory movement so if we go and again look into the step of

00:08:10 respiration we will see that we have first pulmonary ventilation diffusion transportation and definitely the finally regulating the complete ventilation process of human being as well as in in lower vertebrate also okay now we will go in detail about this uh restoration now we are calling it uh the the chapter uh title stands for breathing and exchange of gases now bathing is a terminology which is in the layman language one can call that we are breathing air and all now to to really understand this respiration

00:08:51 we need to go back and look the evolutionary history of um our living organism so if we start looking and digging back the evolutionary history there is no such sophisticated organ system in in lower inverting rates so if we start looking the inverting rates inverting rates stands for the the individual which don't have backbone so this inverted rates we need to understand that slowly in due course of time of evolution the the system get evolved so uh in lower organism something else was there to carry out

00:09:31 this process and slowly in due course of time it got developed evolved and finally in our case human being we have a very specialized structure what we call the respiratory passage which starts from nostril we will discuss now uh in in coming a few minutes about the whole place passage of the respiratory system and finally we have lung so we have very specialized structure in order to carry this process but a lower vertebrate so we will start with a very basic inverted rate don't have vertebral column and the

00:10:05 class is called sorry phylum is called pariphera so we have polyphera now this pariphera is basically sponges sponges now these sponges are present in the bed of our sea level so they are basically aquatic in nature if we start looking that how they look like so they their structures are quite irregular so they have the complete body cavity which is quite irregular in shape and then in the bottom they are attached to the substratum so their their nature is the size they are they are not showing any movement so they are called

00:10:48 sessile sessile is something which is not showing any movement it's called society so these are silent nature now what is happening the whole body of this peripheral these sponges are having very minute pore like a structure so they their whole body is having pore now this pore is called ostia this ostia is basically distributed throughout the body of these sponges so the the water because these anima these organisms are aquatic in nature so they are they are living inside sea level so everything is

00:11:26 coming with water so the water containing all the gaseous element is coming inside the body cavity and then after getting assimilated after getting absorbed through the body surface area it is coming out through a very specialized structure which is called osculum so osculum and ostea are the two entry and exit point respectively in case of sponges so can we say that this is an entry like oxygen is coming inside the body and then a carbon dioxide content is going out from this osculum so this is inspiration and this is

00:12:10 expiration or exhaling out so this is breathing in and breathe out phenomena kind of we correlating the phenomena with higher orgasm so we are calling inspiration which we are taking and expiration which we are expelling out so what is happening here there is no specialized structure so the whole body surface area so we can call body surface is the actual unit of exchange of gases in these sponges now these sponges are very specialized lower inverting rates so slowly it got evolved and because of evolution the

00:12:52 whole structure got modulated in in order to sustain this respiratory process but this is in nutshell about this we we are not going to discuss much about the whole polyphenol as such phylum but we will try to understand that why these are exchanging the gases to the surface area because they lack any specialized respiratory organ in their body next in the slide is cylindrita so in celentrata we have an ideal example and this ideal example is what we call hydra so the phylum cylindrica comprises of

00:13:37 many other organism and one such organism is called hydra if you start look looking into the hydra structure this is again a very cylindrical kind of structure and then again they have opening and this opening is kind of surrounded by this kind of celia or tentacle like a structure which is basically uh situated in the top of their um body cell surface cavity now same thing here also this body surface area is basically the unit of exchange of gases in case of cylindricator so cylindrita also they

00:14:13 have both mode of life they they are aquatic in nature mostly aquatic in nature but then there are certain varieties which are terrestrially also uh in nature of course we are not going to get and dig in detail about those one but again the surface area the body surface area is the actual unit of exchange of gases in this species the next one is is very important and that is called platy helmets now platyhelminthus is a very specific terminology the phylum platyhelminthus uh comprises of the organism which are

00:14:51 flat in nature so they are otherwise called as flat warm flat warm so this flat worm uh so just trying to give an understanding about why they are called as flat worm so we have if we start looking into human body this belly portion is called dorsal sorry ventral so this belly portion is called ventral and then something which is coming from the back is called dorsal so we call ventral so ventral is what is it there in the belly and then we have another thing which is called dorsal in between ventral and dorsal we have a

00:15:38 body cavity if you remove body cavity there is nothing in between so if we squeeze between the ventral and the dorsal surface there will be a flat surface now this worm is like that so they have a body like this so they have this area we can call it this is the ventral and in the back portion they have dorsal from that side and there is no as such defined body cavity we can say there is something in between but we cannot call it uh in lower invertebrate as a body cavity but as such they have dorsal ventrally flattened surface that

00:16:16 means the whole surface area is quite flat so this flat surface area is basically the unit of exchange of gases so the gases because of this large surface area they are exchanging the gases quite efficiently as compared to other species so there is slight advancement in these species in order to increase the substance area so their whole body is squeezed in order to increase the surface area to exchange the gases this is about the flat worm platy helmet the next in the slide is annelida now this analyter is

00:16:55 including the organism which are round and cylindrical in nature and a classical example is earthworm now this earthworm is basically the cylindrical in nature so they have cylindrical and their whole body is segmented so their whole body area is divided into segments and these segments are called as cuticle cuticle cuticles now this cuticles is an area or the the the aspect which are involved in gaseous exchange so basically the surface area the cuticle is involving gaseous section in case of this

00:17:40 analytica the earthworms so slowly we we can see that we are evolving right so the body is basically segmented in in in classification we will see that these structures are called metamers um and these analytes are basically segmented and metamask is a terminology which which defines the segment body cavity so this these are these uh some of the structures are there which are defined in case of anal data now so as i said earlier that organism get involved in due course of time now this thing happened and we

00:18:21 we have the organism evolved and one such evolved organism next in our slide is arthropoda so this arthropoda is ortho means joint so their poda means leg so they have joint leg appearance so their whole body is having a joint leg um appendages and everything is joined to with each other now this author pudda is living in both terrestrial condition and aquatic that means they are terrestrial terrace tree and they are also aquatic that means they can live in water and they can live in land also traditionally means someone

00:19:11 who can survive in land condition and someone who can survive in water aquatic condition to sustain the aquatic mode of life these organisms evolved in such a way that they have a very specialized structure called gills now gills are very specific there are numbers varying number of gills so the oxygen dissolved water or gaseous element dissolved water is passing through the gills and through the passage the gases are getting exchanged in these gills while in case of terrestrial uh arthropods the very specialized

00:19:49 structure we are not saying that these are not that much evolved but we are not calling those evolved organ as lung but we called it book lung so book lungs is a structure available in terrestrial arthropod in order to exchange the gases from the atmosphere to the body cavity so these are two very specialized structure in this arthropod species that can have the the effective exchange of gases from atmosphere to body cavity now having said that these are some of the modifications some of the things

00:20:29 available in the in the body cavity of lower invertebrates now we are not going to go in detail about this lower invertebrate we will try to focus our whole study to higher higher vertebrates like human beings because this whole chapter is about human physiology now in human physiology the whole thing is about a very specialized structure called lungs so as we discussed earlier that inhalation of gases is an important aspect and expiration of gases is an important aspect now um if if we look very critically what is

00:21:08 happening today day to day activity one can realize that we are taking the oxygen and related contain from our nostril as well as our mouth also so if we draw roughly um so what is happening that you have this nostril is one passage so you have no string and then we have this mouth so kind of a normal passage so the air normal air the mixture of oxygen nitrogen carbon dioxide and other gases are getting injury inside the body through either nostril or the mouth so there is a common passage which is kind of a available in

00:21:59 this particular area which is both common for nostrils as well as now and this particular area is called pharynx so this pharynx is a very unique structure uh which is available in the upper upper buccal cavity which is very common to nostril and and the mouth this passage is ultimately narrowing down to a very unique structure and these are the first entry point or the first entrance to the disputed passage and these are called as the rings now this larynx is a very important organ in respiratory system these are

00:22:56 the entry these are the first organ in in the respiratory passage in case of adult male this leadings are basically protruded out this leadings comprises of cartilage so sometimes this protruded version of the larynx and one can feel this depression here uh in in the cartilaginous area this is sometime in adult human beings male is called adam's apple so this adam's apple is basically an indication of that the sound sound system of a male uh individual and these these larynx and adam's apple are sometimes collectively

00:23:48 called as sound box so basically these are the sound producing organ a while a similar kind of a structure is available in case of parrot where we are not calling this a structure as a larynx but we are calling it as a saline which is very sweet kind of sound producer so this whole area is basically the entry point in in case of respiratory system this larynx is basically continuing to a cartilaginous structure which are having a round ring-like structure this round ring-like structure is called

00:24:27 trachea so this trachea is another cartilaginous structure which is basically giving passage and kind of a availability to uh or passage to to to the gaseous material this trachea at the level of fifth rib so we will discuss about this aspect so this is kind of a if we discuss so these are the the level of fifth rib so if you see these are the ribs and in in in the level of fifth rib actually so this fifth rib if you count one two three four and five in in the fifth rib this particular kind of bifurcation is visible in case of

00:25:26 trachea so this bifurcation is called bronchial bronchi now this bronchi are the terminal part of this trachea so there is a cartilaginous ring and at the level of fifth rib there is a bifurcation and this bifurcation is leading into two distinct kind of uh of bronchi now this two bronchi is going to a very distinct kind of a capsulated structure which is kind of like this and these are the specialized structure of respiration and these are called lungs so these are basically structure of lungs

00:26:22 which are containing this bronchi into it now um we will we will see and we will describe this whole uh lung system as such in in detail so uh we'll try to understand here the oxygen entry point and the whole whole aperture the openings which are responsible to getting this in our nostril and mouth these are coming into an area called pharynx pharynx is continuing into a very specialized structure called larynx and this landing is continuing into a cartilaginous ring-like structure called trachea and this trachea

00:27:03 if we start looking and going back to the tissue level what are the what kind of tissue ah structured here so here these are these are stratified squamous epithelium cells which are having a kind of a seriated like structure which we'll try to discuss in in our later classes and then at the level of fifth rib these are tracheal rings containing structure are bifurcating into bronchi which is ultimately going inside this very specialized unique structure called lungs so we will discuss this lung

00:27:41 structure in next so what we have understood till now is the the passage and the ultimate organ now here is trachea and this trachea is coming [Music] into a very specialized destruction and these are basically roughly now this lung are basically we can differ differently this one is a right and this one is a left in human being this right lung light lobe of the lung is divided into three upper middle and one and in case of left we have on the upper and lower and instead of the complete structure we

00:28:45 have a small groove here this group is basically a notch that can have a very specialized mechanism because this is the area where you have this very specialized structure we call it heart so this whole area this this this curvature in this lung left lung is called cardiac notch cardiac notch now this whole uh lung as such is covered by a very specialized kind of a membrane in order to protect the complete covering this unique covering of lung is called plural so pleura is a very specialized structure a kind of a membrane a kind of

00:29:51 recovery that is protecting the lung lobes of lung with their unique structure and this plural is nicely demarcating of lungs with the other organs in the body and since we discussed that these ribs are already here in between ribs you have muscles these muscles are called as intercostal muscle and in the bottom you have a very unique kind of a structure which is very much flexible and giving an actual mechanism of respiration and this structure called diaphragm now this diaphragm is the organ or the the the area which

00:30:55 give flexibility which will which is required later time point for inhalation and expiration uh we will we will discuss this mechanism in in later one later so till now we have this lung and up uh lung lobes upper and lower and then these these right lungs like lobes of lung is differentiated to three ropes while in case of left ones we have upper and lower sometimes we all uh know that there are always kind of a thrust and an injury is going on in our body in in case of lung very fragile organ so

00:31:38 sometimes if you have any infection sometime if you have any kind of a inflammation any kind of injury around lung cavity this particular area is getting inflamed and because of this inflammation this particular area in between lung lobe and the plural membrane is filled out with fluid so this whole area is getting filled with a fluid at the time of inflammation and this fluid is giving a kind of a force to this lung having a distress in in respiration the condition where we have an inflammation

00:32:27 of the lung lobe and the pleural cavity is called pleuritis so we called pleuritis so up we have very very unique kind of an inflammation inflammatory process where the fluoride membrane is getting inflamed and the the fluid filled cavity is the condition is called fluorescein sometime uh due to inflammation and all so these are the typical anatomical model where the lung structure is divided with the help of this unique plural membrane we have ribs this is kind of a cage like a structure and then outer covering is

00:33:15 what we have called plural membrane and this plural membrane is sometimes getting inflamed and converted and and getting a condition called pleuritis this pleuritis is sometimes getting accumulation of the fluid because you receive so in these are some of the anatomical features related to this bronchi and lungs so um to understand the alveoli what is there in the alveoli uh so say this is our trachea and this trachea is bifurcating at the level of fifth trip and the level of riffs and then uh this

00:33:56 specific uh terminal branches of bronchi we call this one as bronchi now this bronchi is basically branching out into smaller so there are many branching pattern so this branching pattern is there so many branches are there and this branching pattern is called bronchioles bronchioles now this bronchioles is the terminal aspect terminal point of this bronchi now this bronchiole if you start looking bronchioles in detail they have a very kind of globular structure this globular structure now this globular structure is what we

00:34:50 called l v o lie so these are the alveoli and uh if we start digging again back and see that what are the actual content of alveoli we can call this one as an alveoli sac so we can call it this is a sac so this is a bag-like structure anything related or look like bag we call sac in biology and then we have a small kind of duct following through this thing so we call it duct so we have alveolar sac and the alveoli duct so these are actually the content of alveoli so we have sac and duct now this structure is quite elastic

00:35:35 because we need to inspire the air once the air is going there is a huge flexibility and because of this flexible flexible movement the things are expanding in and out so we need some very specialized elastic fiber so these there are small fibers which are quite distributed throughout this area and these are all elastic fibers elastic fiber and of course this whole area is what we call lungs so these are basically lungs so these are specialized structure and this alveoli is the terminal point where

00:36:14 we need to understand the exchange of gases so now we will try to see what is happening exactly the level of alveoli where the exchange of gases takes place now having said that so this this terminal part is very flexible and this uh regulation of ventilation and other thing which we we we discussed in the very beginning of our lecture that we require to intake the air and for that we need ventilation so this pulmonary ventilation is very much regulated by this elastic filament and of course there are many muscles involved in this

00:36:49 process which we will discuss in in our coming now if we see this is the alveoli and then if we start looking the structure of this much of the algolite and if we look in this algolite one can see that these are very unique epithelium these epitheliums are very very thin and because of the thin nature these are called squamous epithelium now this is formulas epithelium is available in the lining of this bronch alveoli and in this alveoli this lining this small lining is important because there there requires an is effective

00:37:32 diffusion of gases from alveoli to the blood vessels now this whole structure which are very unique here basically comprises of a very thin nucleus which are which is which is pulled out in this area so these are the line of this very structure called alveolar so this squamous epithelium are the ultimate so we have here oxygen and we have here co2 and then in in this area we have this blood coming up into into the into the system now this blood there are two kind of blood vessels which we'll discuss again uh in our

00:38:27 coming lectures uh one which can carry the pure blood although all arteries of the blood all arteries of the body carry the pure blood but pulmonary artery is one such artery in the body that carry the impure blood but opposite is true in case of veins all veins carry the impure blood but pulmonary vein is one such vein in the body that carry the pure oxygenated form of the blood so now since this this so here the concentration of oxygen is very high so oxygen is moving from higher gradient to lower gradient

00:39:08 so oxygen is coming here since this blood is coming from the tissue side the concentration of co2 is quite high here now the co2 concentration from this area is getting exchanged in this direction because of the higher concentration to lower concentration so we will discuss about this mechanism in our coming lectures where we will see how this gaseous exchange takes place in terms of the partial pressure of oxygen and carbon dioxide molecule in terms of mm of mercury so ah these are in in nutshell about the

00:39:44 complete mechanism complete uh picture complete anatomical structure of the human respiratory passage right from the nostril and mouth and till the alveoli which is the ultimate unit where the exchange of gases takes place so if we summarize the whole anatomical structure and the physiological function of respiratory passage one can nicely uh jot down the whole phenomena into few things one the gases are coming inside the body which are mixture of oxygen nitrogen and carbon dioxide and these gases

00:40:24 are kind of traveling downstream in this passage which is called respiratory passage and coming to a very specialized structure called algorithm and from this algolite one can nicely see because of this unique structure unique epithelium called as squamous epithelium the gases are exchanged from the higher concentration to lower concentration you