Module 3.1 and 3.2 Flashcards
there is about hundrd cards tha have been repeates o keep tha tin mindd ...
dUnicellular / singlecellular organism (amoeba)
-fresh water ponds
-all organisms re constanlty , eschaning materials , with their enviornment .
-e.g , amoeba carries out aerobic respirattion generae atp .
-oxygen , needed for aerobic respiration —> diffuses into he cel through the cell membrane .
-scientists call the cell membrane an exchange surface .
-when amoeba carries our respiration , it prouduces the gas co2 .
-this co2 diffuses out of the cel via the cell membrane ,
In microscopic organsisms _ amoeba organism , exhange all the substance it needs directly though the cell memerbane , There is two reasons for this .
reason one
-microsocopic organisms , relatively low rate of respiration as ehya rent ery active organsimss .
reasons two
relatively large compared to volue of the cell . SA:V ,
-calcukae sa;v ratio using this equation
s:volume ratio = surface area / volume
sa;v=24/8 =3:1 96/64=1.5:1 for example
-single cell organsisms have a large sa to volume ratio .
they can transfer all of the chemicals they need across the cell membrane .
-However , large multiceullar orgasims sa;V much less .
-some small multicellular organsisms do rely on diffusion across their body e.g flatowrm .
by evolvingg a very flat and thin body size all of the cells in the flat are clsoe to the surfce .
-so diffusion corss hte body urfce is sufficne in a fla surface .
-HOWEVER , LARGE MULTICeullar organsims sa : v can not what .
-So multiceullar organsism evovles two specialsied sytems to compensate .
evolving one
-evovled specialised gas exchange sytems –> very large surface area ( lungs in mammals gulls in gish .
evovling two
specialsied transport sytem to carry moelcules around their bodlood
Mammals have a very low surface to volume ratio .
-mammals are also very active animals , mammals maintain a constant body temp .
-this required , an increased rate of aerobic respiration .
for these reasons , mammals have an extremely high oxygen demand .
-mammals , get their oxygen from the air , via their lungs shown , structure of human breathing system .
-humans have two lungs which are found in the thorax chest activity .
-the lungs are protected by the ribs .
-The ribs also plays a role in breathing .
-Along , with the intercostal muscles and diaphragm .
stage one of breathing
-when humans breathe though their nose , air passes through the nasal cavity .
-hairs in the nasal cavity traps , dust particles and pathogens .
-the nasal cavity also warms and moistens the air before it enter the lungs .
stage two of breathing
-The air , then makes it way down a wide tube called the trachea .
-The air then makes it way down a wide tube calle the trachea .
the trachea two key adaptations which you need to learn .
-walls of the trachea contain cartilage which is a firm but flexible material .
-The cartilage prevent the walls of the trachea , for collapsing when we inhale .
-this diagram shows a view of the trachea looking down towards the lungs .
-as you can see the trachea is very close to the oesophagus , which is the tube carrying food to the stomach .
-Yu’ll notice that the cartilage in the trachea forms a c shape , rather than forming the complete rings ?
Why does it not form complete rings ?
The absence if cartilage in the region near the oesophagus allows the food to pass down the oesophagus easily .
What is the second adaptation of the trachea
The walls are lined with ciliated epithelial and goblet cells .
-Showing cells lining the walls of the trachea .
What s the role of goblet cells
Goblet cells secrete mucus which traps dust particles and pathogens .
-The ciliated epithelial cells have cilia extending from the cell membrane .
-T
What do the cilia do ?
The beating of the cilia moves the mucus to the throat .
-The mucus is then swallowed and the dust and pathogens are digested by the stomach enzymes .
Going back to our lungs , we can see trachea divide into two bronchi
two bronchus carries air into one of the lung .
-Just like the trachea , the bronchi contain cartilage ciliated epithelial and goblet cells .
What does each bronchus split into ?
Each bronchus splits forming progressively narrower airways called bronchioles .
-The walls of larger bronchioles are supported by cartilage , they also contain smooth muscle .
What happens when the smooth muscle reflexes ?
The bronchioles widen allowing more air to pass into the deeper part of the lungs .
Deep in the lungs the bronchioles are extremely narrow .
What do these bronchioles lead to ?
Air sacs , called alveoli .
-Alveoli are the sites of gas exchange .
-There are hundreds of millions of alveoli in the lungs . The internal walls of the alveoli are covered with a thin layer of moisture .
-Close up of the alveoli , the alveoli is covered with blood capillaries .,
What happens to the oxygen in the air ?
Oxygen in the air of the alveoli dissolves nt he mositure on the inside of the alveoli wall .
-The oxygen then diffuses into the red blood cells where it combines with haemoglobin .
-Carbon dioxide diffuses from the blood into the alvelar spcae .
Between the alveoli , are elastic fibres which stretch and recoil during breathing .
As we have seen , the alveoli is where gases diffuse in and out of the blood .
What is one way alveoli are adapted to maximise the rate of diffusion .
Hundreds of millions of alveoli , these provide a massive surface area for the diffusion of gases .
Check sheet for the close up of alveolus and blood capillaries .
Both he wall of the alveolus and the walls of the capillary are only one cell thick .
-This means there is a very short diffusion distance between the air in the alveolia nd red blood cells in the capillary .
The narrow diameter of the capillary means that the red blood cells are close tot he capillary wall .
This minimises diffusion distance .
The extensive capillary network means that once oxygen diffuses into the blood , what happens ?
It is rapidly carried away from the alveoli -This ensures there is always a steep concentration gradient for oxygen .
Co2 also has a steep concentration gradient ,a s more is continually brought to the alveoli int he blood stream .
these concentration gradients are also maintained by breathing , which brings fresh air into the alveoli .
This ensures there is always a high concentration of oxygen in the alveolar air .
as well as a low concentration of co2 , this helps to ensure a rapid rate of diffusion of these gases .
What is breathing also known as ?
Ventilation .
-Ventilation brings fresh air from outside of the body into the alveoli .
-THIS , increases the concentration of oxygen in the alveoli air spaces whilst decreasing the concentration of co2 .
-The effect of this , is to increase the concentration of these gases thus increasing the rate of reaction .
What is the mechanism for ventilation ?
Simplified version of the lungs .
-Ventilation involves the action of two sets of muscles .
Muscle one involved in ventilation
intercostal muscles - which lie between the ribs and the diaphragm .
-Which separates the thorax (chest cavity ) from the abdomen .
-The two sets of muscles work together to change the volume of the thorax .
-
What happens if we change the volume of the thorax ?
By changing the volume of the thorax , this changes the pressure of air in the lungs .
-The effect of this , is to draw air into the lungs (inhalation ) . Or to expel air from the lugs (exhalation )
There are the two sets of intercostal muscles . What are they ?
These are called the external and internal intercostal muscles as they are involved in regular breathing . focus on external
-The internal intercostal muscles are involved in stronger breathing , this is what happens when we inhale / breathe in .
Stage one of inhalation
during inhalation ,t he external intercostal muscles contract aka they shorten .
-this pulls the ribs upwards and outwards l
stage two of inhalaiton
at the same time ,t he diaphragm also contracts which causes it tot flatten . The effect of these is to increase the volume of the thorax and lungs .
-This reduces the air pressure in the lungs .
stage thee of inhalation
as the air pressure in he lungs is now less than atmosphere pressure , air is drawn into he lungs .
-air is moves into the alveoli and the elastic fibres between the alveoli stretch .
BECAUSE - inhalation involve muscles constrain , inhalation active process .
Stage one of exhalation
during regular breathing , exhalation is essentially process as the muscles relax .
-Therefore exhalation does not require a great deal of energy .
stage two of exhalation
-during exhalation ,the external intercostal muscles relax and return to their original length .
stage three of exhalation
the diaphragm also relaxes returning to its usual dhape .
-The effects of this is to reduce there volume of the thorax and lungs .
-now air pressure in the lungs is gretaher than atmospehrec pressure .
-air ispushed out of the lugns .
-The elastic fibres between the alveoli also recoil helping to push out he air
scientists call this elastic retraction .
volume of lungs changes when we inhale and exhale
lungs are surrounded by a pleural membrane .
what do theyd o ?
between these membranes there is plural fluid which acts as a lubricant as the lung volume changes
As we have seen . during regular breathing exhalation is mainly a passive process .
This is not the case ,when we exhale strongly , as during this internal intercostal macules contract as we exhale strongly .
-this pulls the ribs down and inwards forcing air out of the lungs .
At the same time , the external intercostal muscles relax
As the internal intercostal muscles relax which the external interoctysal muscles contract . Scientists descrier this as antagnote .
What are bony fish and give examples
They are a large group of fish which have evolved a skeleton made of bone
Tuna salmon cod and trout
Whag js the significant issue when it comes to gas exhange in fish ?
Bony fish are large and active organisms with a very high oxygen requirement
-because of their large size they have a very low surface area to volume ratio .
2. The SCALY surface of bony fish does not allow gasses to pass through
How do fish get their oxygen ? But what is problem
From the water , but concentration of oxygen in the water is MUCH LOWER than in air .
So for these reasons , bony fish have evolved a specialised gas exchange system . Which extracts MAZOMUM AMOUNT of oxygen from water
Bony fish have a flap of tissue on either side , slightly behind their head function ? .
This is called operculum I’m and we have behind this the operculum cavity .
INSIDE the operculum cavity , we find gills .
S1 gas exchange in fish
Oxygen rich water enters the fish through the mouth
S2 gas exchange in fish
Water then passes over the gills ,
In gills oxygen diffuses from the water into the blood . And carbon dioxide diffuses from the blood into the water .
Finally water passes through the operculsr opening .
Structure of gills ( go all the way to card 397 to continue then come back to do insects )
gills consists of several bony arches , extending from each gill arch are a large number of gill filaments .
Insects can be extremely active organisms so what would there oxygen demand be like ?
They would have a very high oxygen demand , for example , during flight .
Key , how have gas exchange systems evolved in insects ?
to provide oxygen directly to cells .
-although insects do have a specialised transport system , this transfers nutrients and not oxygen .
What are insects covered with ?
A protective exoskeleton made of the polysaccharide chitin .
-Gases such as oxygen and carbon dioxide do not easily pass though .
-so on the surface of the exoskeleton ,t here are small openings called spircales .
What do spiracles do ?
Spiracles allow gases such as oxygen and carbon dioxide to diffuse into the body of the insect .
What can spiracles leads to ?
Spircales can lead into a network of tubes called the trachea .
(trachea are relatively wide tubes with a diameter of around 1 mm) .
-trachea extends down into the body of t he insect .
-trachea are relatively wide tubes with a diameter of around 1 mm .
-trachea extends down and along the insect’s body .
what is the trachea reinforced with
spirals of chitin .
-the chitin prevents the trachea from collapsing example when an insect moves .
-extending from the trachea are very fine tubes called tracheoles .
What are the adaptations of tracheoles ?
Tracheoles have a diameter of around 1 micrometre , or less .
-In fact they are much narrower than shown in the diagram .
-each trachea is a single cell that has extended to form a hollowtube .
insects
-a huge number of tracheoles extend down inbetween the cells of the insects body .
adaptations 2 of tracheoles
unlike trachea , tracheoles are not supported by chitin .
-This is because tracheoles have such a narrow diameter and are extremely close to cells , there is a very short diffusion distance for gases moving between the cells and the tracheoles .
adaptation 3 of tracheoles
huge number of tracheoles provide a very large surface area for gas exchange .
-this allows insects to maintain a very rapid rate of aerobic respiration ( example flight ) .
What are the ends of the trachea filled with ?
They are filled with fluid also known as tracheal fluid .
-during intense activity , the cells around the tracheoles undergo anaerobic respiration .
-anaerobic respiration which produces lactic acid lowering the water potential of the cells .
what does lowering the water potential of cells do to the tracheal fluid ?
causes the water in the tracheal fluid to move into the cell .
-this reduces the volume of the tracheal fluid drawing air into the tracheoles .
-also shows more tracheole surround avoidable for diffusion of oxygen and carbon dioxide .
Is gas exchange active or passive in insects ?
It is essentially a passive process .
This is because , oxygen diffuses down its co2 gradient from a high concentration in the external air into the lower concentration .
describe co2 diffusion in insects
co2 , diffuses down its conc tracheoles gradient .
-with a relatively high concentration in the tracheoles out to the external air .
rate of diffusion decreases with distance meaning insects tend to be small .
smaller size of insects , reduces distance required for diffusion to take place .
…
However , what is one problem that insects have ?
This is loss of water .
-The walls of the tracheoles are moist and the ends contain tracheal fluid .
-Meaning , water vapour can diffuse out of an insect via the spiracles .
However , what is one problem that insects have ? (2)
muscular sphincter .
-This means insects can reduce water loss by closing their spiracle (example insects oxygen req)
ocr , –> how have some insects evolved to increase rate of gas exchange ?
-If , we look at insects ,w e can see they have three main body segments .
Head –> Thorax–> Abdomen
-Some insects can also contract muscles to change the volume of the thorax and abdomen .
ocr , –> how have some insects evolved to increase rate of gas exchange ? (2)
causing , pressure changes in the trachea pushing air in and out .
-this bulk movement is called mass movement .
-in some insects , the trachea contain expanding sections called air sacs .
-What are the adaptations of the air sacs ?
-changes in the volume of the thorax and the abdomen can squeeze the air sacs , causing air to move from the air sacs into the tracheoles . -insects can also use the oxygen in the air sacs during when the spiracles have been closed for water conservation .
Larger organisms , have a much lower surface area to volume ration , so what does this mean ?
The vast majority of cells are a large distance from the surface of organisms .
-also , large organsisms , are often , very active , and have a high demand of oxygen for aerobic respirations /
so , if larger organisms , cannot rely on diffusion alone for the exchange of material , what else do they rely on ?
-we have already seen , how insects fish and humans have specialised gas exchange systems .
-This ensures a very efficent gas exchnage sytem for oxygen and carbondioixde .
how have insects adapted to their gas exchange system ?
so that gases diffuse directly .
How does diffusion work in fish and humans ?
gases dissolve in blood , which acts as a transport system .
-The blood then moves around the circulatory system , transferring the gases between the cells and
the gas exchange system .
what else does blood transfer , other than oxygen ?
Other essential molecules like glucose and amino acids .
-when molecules are carried in a transport medium such as blood through a circulatory system , scientists call this mass transport .
circulatory system of fish (1)
deoxygenated blood , is pumped by the heart , through the blood vessels to the gills .
circulatory system of fish (2)
In the gills , blood passes though narrow blood vessels called capillaries .
-oxygen diffuses from the water into the blood .
circulatory system of fish (3)
the oxygenated blood now passes from the gills though the blood vessels to the body tissues .
circulatory system of fish (4)
when it reaches the body tissues , the blood again passes though narrow capillaries , where oxygen diffuses from the blood to the cells that needd it .
circulatory system of fish (5)
finally , the deoxygenated blood , now returns in blood vessels back to the heart .
circulatory system of fish (6)
so blood , only passes though the heart only once .
-as it moves around the circulatory system scientists call this a single circulatory system .
problem with single circulatory system ?
when the blood passes through two sets of narrow capillaries .
-firstly ,
-firstly , in the gills . and secondly , as it passes into the body tissues when the blood passes though capillaries’ , blood flows down and looses pressure .
-MEANING –> once ,, the blood passes though the gills , blood is moving relatively slowly .
-limiting how rapidly oxygen can be delivered to body cells .
circulatory system in mammals (1)
deoxygenated blood is pumped under high pressure from the heart to the lungs .
circulatory system in mammals (2)
in the lungs , blood passes though the narrow capillaries and oxygen diffuses from air into the blood.
circulatory system in mammals (3)
As the blood , has passed though the capillaries , it is moving slowly with lower pressure .
circulatory system in mammals (4)
however , now the oxygenated blood returns back to the heart . Pumping blood at high pressure around the body .
circulatory system in mammals (5)
as it passes though the body , blood passes through the capillaries and oxygen diffuses to the body cells .
circulatory system in mammals (6(
the low pressure , deoxygenated blood now makes it way back to the heart to be pumped again .
so double circualtory system , blood passes though twice
this makes sure the blood makes it ways to the body tissues rapidly and under high pressure .
-so a double circulatory system can carry oxygen more efficiently , than a single circulatory system .
what is a closed sytem ?
-fish and mammmals , blood is always contained in blood vessels as it travels form the heart . this is a closed ciruclaotry sytem .
-in a closed cirulatory sytem , blood can move relatively rapidly , and the amout of blood pumped to differen ooorgans can be controlled by constricting or dialiating blood vessels .
What is an open circulatory sytem ?
insects have it , insects do not contain blood .
-instead , they contain a fluid called haemolymph .
-haemolymph carries nutrients also like sugar’s but do not carry oxygens //
-haemolymph is pumped out of the insects heart and passes directly into the body cavity called haermoroel .
-moelcuels are then transferred , becween the haemolymp and body ells an d hten the haemolymph makes its way back into the heart .
what is key about haemolymph
It is not carried in Venule , so it is an example of an open circulatory system .
-as the haemolympg is not Carried in vessels and jf moves rapidly around the insect .
-Also. (!3 insect is nkg essily change or cannot of how how much is moving to different parts of its body .
What do arteries branch to form
They form narrow blood vessels called arterioles.
Arteries carry the blood to the capillaries from each organ .
How does molecules diffuse in the capillaries
-Morley les diffuse from the body cells back into the blood .
-finally . The blood then passes from capillary to blood vessels called Venules and the which carry the blood back k tk the heart .
What way does the arteries carry the blood ?
Arteries carry the blood away from the heart to the organs blood on the arteries is under high pressure .
What is the pulse ?
When the heart beats , a surge of even higher blood
Pressure is pushed down the arteries scientists call this
PULSE
What way does the heart beat even when the heart beats ?
It moved FORWARD
-cross ex goin of w typical artery
- although I should point out , that very large artistes can have a wide diameter
Adaptation of arteries
The first thing to notice is that the artery wall is relatively thick .
-l this alllsws the artery to withstand high pressure of the blood .
The walls of the artery consist of several layers
…
The outer layer of the artery EXPLAIN
The other layer of the artery is rich in the fibrous protein collagen .
-collagen plays a structural role in, strengthening the artery wall against the pressure of the blood .
Next , the artery has a layer containing smooth malice
When the smooth muscle contracts , the diameter of the artery narrows .
THis alllws the body to control how much blood flows to different organs .
Different between large and small muscles
Smaller arteries tend to have a greater proportion of SMOOTJ muscles than larger ateries .
-that js bevause smaller attire is okay a great role in controlling blood pressure
Next layer w shave is elastic fibres
Elastin fibres contain the protein elastin which can stretch .
/when the heart contracts a surge of high blood pressure passes down the artery .
-as fhe surge moves through , the elastic fibres stretch , fhen recoil , once the surge has passed .
Elastic recoil helps the blood moving smoothly forward , inbetween contractions of the heart .
What is the. Entrap. about of the artery. Called ? Lumen
The linen is where the blood flows through. Lumen is lined with a thin layer of endothelial cells .
- this presents a very smooth surface to reduce the friction as blood flows through .
What do arteries branch into ?
Smaller blood vessels called arterioles .
What is the job of the arterioles
The jobs of the arterioles is to deliverto to the capillaries .
-the walls of the arterioles contain the same layers as arteries . -but as you will see they differe in their relative thickness .
Blood pressure in arterioles
-the blood pressure is lower than in arteries and the effect of the pulse is weak . This means , that in arterioles the collagen - rich outer mager and the elastic kager are relatively thin compared to the arteries .
What about the smooth muscle layer in arterioles
-is
Much thicker than in arteries .
- that is because arterioles are invovled in. Contracting the amount of blood passing through the capillaries .
What happens when the smooth muscles on the arterioles contact
Blood flow through the cappillaties ir reduced .
-scientists call this vasoconstriction
/hwo ded fhe smooth muscle in the arteries relaxes .
- blood flow through the capillaries increases , scientists call this vasodilation .
When does vasodilation take place ?
Vasodilation takes place when an organ requires an in increased amount of oxygen .
There is an extensive network of.Capillaries in every organ ?
As you can see , cappilladies are extensively branched and no body cell is very far from a capillary .
What is a network of capillaries called ?
What happens here ?
It is called a capillary bed .
_the capillary hed is where substances are e change between the blood and body cells .
-for example , oxygen and glucose diffuse from the blood to the body cells .
How do waste products diffuse ?
Waste products such as carbon dioxide diffuse from the cells back to the blood .
What does the extensive branching of capillaries provide ?
It provides a massive surface area for the exchange of. Materials .
- the structure of capillaries has evolved tk maximise the rate of diffusion for molecules such as oxygen .
What are the walls of capillaries like in the blood vessels ?
They ade extremely thin walls
-in fact , the walls of the capillaries consist of a single layer of endothelial cells .
What is the outside membrane like of capillaries ?
There is a thin membrane called the basement membrane .
-consists of a single layer of cells .
-making there is a short diffusion distance between the blood and the cells near the capillary .
Why does the shift diffuse distance of the capillaries help ?
-it increases the rate of diffusion for molecules .
-between the blood and the cells for example oxygen and carbon dioxide .
What is the diameter of the capillary lumen like compared to. Red blood cell
It is only slighted higher than a red blood cell .
—this means that when red blood cells pass through the capillary , they are pressed against the capillary wall .
What is the effect of the red blood cells being pressed against the wall !
This reduces the distance for diffusion fo oxygen .
-from the red blood s tk the tissue cells .
- as the lumen of the capillaries is only slightly wider than a red blood cell .
-meaning ew e blood cells reve
Though capillaries in a single file. /
What does it mean as red blood cells are travelling in single file ?
Because of this , red blood cells
Love though the capillaries
More
Slowly than on arteries and arterioles .
-this relative movement , increases the time available for molecules to diffuse in and out of the blood S
Last adaptation of capillaries
-if we look at the capillaries we can see gaps between endothelial cells .
These gaps allow fluid to pass out of the blood and scientists flak this tissue fluid .
- tissue fluid ? Bathes the cells providing essential molecules such as glucose and amino acids .
What do the gals in the capillary wall do ?
Allow white blood cells to leave the blood steam .
Where does the blood goe after it passes though the capillary ?
It makes its way though very small veins called the venules .
What do venules connect into . S
Venules connect into larger veins .
- these veins carry deoxygenated blood to the venavava where it passes into the heart .
How does blood in the Venules travel ?
Unlike arteries the blood in the Venules and veins flow under flow pressure and it is not travelling in pulses .
-this means that the structure of the veins is different to the arteries .
Why do veins have thinner s than arteries ?
This is because the walls of the veins do not need to withstand high blood pressure.
Why do veins have a larger lumen ?
To carry a greater volume of blood compared to the arteries .
- the smooth muscle layer and the elastic.are thinner in veins compared to the arteries .
Rememebr , the blood on veins does not travel in pulses , so there is no elastic. Recoil .
However , just like arteries. (!: lumen of the veins has an internal lining of endothelial cells . The smooth surfaces reduces the friction between the old and the walls of the veins .
Another important adaptation of grind er nerd yo learning that veins contain valves .
These valves keep the blood flowing in the forward direction.
- rememebr , the blood vessels are moving back to the heart .
Meaning blood may well be moving against gravity especially in legs and arms
Problem of blood in the veins ?
It is travelling slowly and under low pressure q
Quesfion ? What makes blood in the veins move back to the heart
Many veins are found lying between the skeletal muscles such as the large muscle of the arms and legs .
- when these muscles contract e.g during normal movement , they stayed: between the veins lying between them .
Blood flowing back to the heart part two
As we have seen xx veins have relatively thin walls . So when they squeeze they change shape .
This squeezing forces the blood along . If the blood moves forward then the valves. Remain open XD s
/however if the blood starts to move backwards fhen then the valves shut
The combined egg feed kd the muscles Darryl’s and the grind Ed erll Ed the action of the valves
Helps to keep the blood moving towards the heart .
What are the two main components of blood
Cells —> red blood cells which transport oxygen and white blood cells which play a role in the immunity .
- blood cells are suspended and cell fragments platelets are in a water solution invovled in blood clotting called blood plasma .
What does blood plasma contain
Blood plasma contains a range of dissolved molecules such as glucose and amino acids and ions such as sodium ions xx
- blood plasma also cotnains dissolved oxygen which ?
Blood plasma also contains contains dissolved oxygen which doffusss out of the red blood cells. .
- another very important of blood plasma are proteins such as Albanian scientists refer to these as plasma proteins. .
What does the fluid do in the capillaries ?
The fluid passes out of the blood and bathed the tissue cells .
- scientists call it tissue fluid .
What does tissue fluid do ?
Tissue fluid leaves the bloood at the part of the capillary which is near the artery .
/ tissue fluid transfers molecules such as oxygen and tissue cells .
What do waste meocluels from tissue cells do ?
Did exmsd co2 pass into the tissue fluid
- the tissue fluid then truths bsck I my o the bloodstream. Af parts of the capillary which are near the vein ,
Stage one of how tissue fluids move on and out of the blood (1)
Tissue fluid is forced out of the blood at the arterial end of the blood capillary . And returns back to the blood at the venous end of the blood capillary ,
In order to understand the tissue fluid process we need to look at two competing factors
-. These are calllrd hydrostatic pressure and on proof oressure
/ structural end of capillary whrte tisdru fluid it reached - at the end of the capillary , the blood ha: .
end of the capillary the blood has just passed into an arteriole
-because of this , the blood at the arterial and of the capillary is still under relatively high pressure ,
-scientists call this hydrostatic pressure
what does hydrostatic pressure do ?
hydrostatic pressure tends to force fluid out of the blood into the tissue .
-remember , in blood plasma , got plasma proteins like abeli .
what do plasma proteins do ?
-plasma proteins are hydrophilic so they try to lower the water potential , of the blood plasma .
-because the plasma proteins , there is a tendency for water to move back into the blood by osmosis .
-scientists call this oncotic pressure .
what is the hydrostatic pressure like at the arterial end ?
the hydrostatic pressure is greater than the oncotic pressure .
-this means tissue fluid is forced out of the capillary through the gaps between the endothelial cells .
-scientists call this process ultrafiltration .
do proteins and blood plasma leave ?
no , they are too large so they remain in the blood plasma .
What is the hydrostatic pressure like ,a t the venous end ?
The hydrostatic pressure is much lower , as a large amount of water has left the blood .
how is the oncotic pressure like at the venous end ?
the oncotic pressure is still high due to the plasma proteins in the blood plasma .
- so , because of this ,a t the venous end , the hydrostatic pressure is less than the oncotic pressure . Causing , water to move back to the blood by osmosis .
Around 90% of the tissue fluid is reabsorbed back into the blood .
what happens to the remaining ten percent .
the remaining ten percent of the tissue fluid drains into a series of blind-ended valves called lymph capillaries .
What do lymph capillaries do ?
Lymph capillaries connect into large lymph vessels forming the lymphatic system .
-the lymphatic fluid moves along to the lymph vessels are squeezed by nearby skeletal muscles .
There are also valves in the lymph valves , why ?
valves into he lymph help to keep the lymph fluid .
-eventually , the lymph fluid returns to the blood stream via blood vessels under the collar bone .
-the lymphatic system also plays a role in immunity .
what is the activity of insects ?
insects can be extremely active organisms with a very high oxygen demand . For examples , during flight .
What is key about the gas exchange in insects ?
gas exchange systems in insects have evolved to provide oxygen directly to cells .
-although insects do have a specialised transport system , this only tansfers nutrients not oxygen .
What are insects covered in to aid gas exchange ?
insects are covered with a protective exoskeleton , made from the polysaccharide chitin .
-gases such as oxygen and carbon dioxide cannot easily pass through the exoskeleton , so what does the exoskeleton have to aid this ?
-On the surface of the exoskeleton , we have small openings called spiracles .
-Spiracles allow gases such as oxygen and carbon dioxide to diffuse into the body of the insect .
what do spiracles lead to ?
spiracles can lead into a network of tubes called trachea .
-The trachea are relatively wide tubes with a diameter of 1 mm .
-trachea extends down and along an insects body .
what are the walls of the trachea reinforced with ?
they are reinforced with spirals of chitin .
what does the chitin do in the trachea ?
-the chitin prevents the trachea from collapsing example when an insect moves .
-extending from the trachea are very fine tubes called tracheoles .
give one adaptation of tracheoles
tracheoles have a diameter of around 1mm or less / So in fact , they are much mroe narrow then shown .
-each trachea is a single cell that has extendfed to forma hollow tues .
where do the tracheoles extend into ?
down in-between the insects body .
another adaptation of tracheoles
-unlike trachea , tracheoles are not supported by chitin . Because , tracheoles have such a narrow diameter and have an extremely close to cells .. there is a very short diffusion distance for gases moving in between the cells and for gases moving between he cells and the tracheoles .
another adaptation of tracheoles (2)
this allows , oxygen to diffuse rapidly from the air in the trachea , into the cells .
-the oxygen is needed for aerobic respiration which produces the gas carbon dioxide .
-the carbon dioxide can also rapidly diffuse back into the air in the tracheoles .
Give a third adaptation of tracheoles
huge number of tracheoles provide a very large surface area for gas exchange .
-this allows insects to maintain a very rapid rate of aerobic respiration (flight)
-the ends of the trachea are filled with fluid aka tracheal fluid .
what happens during intense activity in insects
cells undergo anaerobic respiration .
-anaerobic respiration produces lactic acid , lowering the water potential of cells.#
-This then causes the water in the tracheal fluid to move into the cells .
-This reduces the volume of the trachea fluid drawing air into the tracheoles.
-also means more tracheole surface is available for diffusion of carbon dioxide and oxygen
In many insects , gas exchange is essentially an a passive process , explain ?
-oxygen diffuses down the co2 gradient and from high concentrations in the external air .
-rate of diffusion decreases with distance meaning insects tend to be small .
-smaller size insects reduces distance for diffusion to take place .
What is the significant problem that insects face ?
Loss of water .
-walls of the tracheoles are moist and the ends of the tracheoles contain tracheal fluid .
-meaning water vapour can diffuse out of the insect via the spiracles .
however , what is the spiracles surrounded
each spiracle is surrounded by a muscular sphiniser, this means that insects can reduce water loss by closing their spiracles .
(e.g insects increase oxygen requirement )
some insects have evolved to gas exchange
if we look at insects we can see we have three main body segments .
-head
-thorax
-abdomen .
-some insects can also contract muscles to change the volume of the thorax and the abdomen
-causing pressure changes in the trachea and tracheoles , pushing air in and out this bulk movement of air is called mass transports .
in some insects , the trachea contain expanding sections called air sacs . Explain what the air sacs do ?
changes in the volume of the thorax and the abdomen can squeeze the air sac causing air to move from the airspaces into the tracheoles .
-insects can also use the oxygen in airsacs during … when spiracles have been closed for water conservation .
what do larger organisms have compared to smaller organisms ? 1
-larger organisms have a much lower surface area to volume ration with the vast majority of cells a large distancer form he surface of the organisms .
