Exchange Surfaces and Transport in Animals Flashcards
can the cell membrane be an exchange surface for small organisms?
Yes
do small organisms have a high or low metabolic rate?
Low
do small organisms have a low or high surface area to volume ratio?
A high surface area to volume ratio
how do you calculate the surface area to volume ratio?
Surface area/volume
(SA:1)
in insects has the gas exchange system evolved to provide oxygen directly to cells?
Yes
do the specialised transport systems in insects transport oxygen or nutrients?
Nutrients
what is the surface of an insect covered with?
An exoskeleton
What is an insects exoskeleton make out of?
The polysaccharide chitin
Why do insects need spiracles on their exoskeleton?
So that gases like oxygen and carbon dioxide can diffuse into the insect
What do the spiracles lead to ?
The trachea
what is the diameter of the trachea in insects?
1mm
is the diameter of the trachea in insects larger or smaller than the diameter of the trachea in animals?
Smaller
What are walls of the trachea in insects made up of?
Chitin
What are walls of the trachea in animals made up of?
cartilage
Why does the trachea in insects need chitin?
To prevent the trachea from collapsing
What extends from the trachea in insects?
Very fine tubes called tracheoles
What is the diameter of tracheoles?
1 micrometre or less
is each tracheole a single cell?
Yes
are tracheoles supported by chitin?
No
Why is there a short diffusion distance between the tracheoles and the insects cells?
-because tracheoles have a narrow diameter
-because tracheoles are extremely close to cells
What is the oxygen from the tracheoles needed by the cells for?
Aerobic respiration, which produces carbon dioxide
What are the ends of the tracheoles filled with ?
tracheal fluid
Why does water from the tracheal fluid move into the insect cells during intense activity?
-Because during intense activity, cells around the tracheoles undergo anaerobic respiration and this produces lactic acid.
-This lowers the water potential of the cells and causes water to move from the tracheoles into the cells by osmosis.
-This reduces the volume of the tracheal fluid, drawing air down into the tracheoles
is gas exchange in insects an active or a passive process?
A passive process
what is a significant problem faced by insects?
Water loss
are the walls of the tracheoles moist or dry?
They’re moist
how can water vapour diffuse out of an insect?
Via the spiracles
What is each spiracle surrounded by ?
A muscular sphincter
What does the muscular sphincter do?
Control the opening and closing of the spiracles
How many main body segments do insects have?
3
What are the 3 main body segments of an insect?
The head, the thorax and the abdomen
Why do the trachea contain air sacs in some insects?
Because changes in the thorax and abdomen can squeeze the air sacs and cause air to move from the air sacs to the tracheoles . Insects can also use the oxygen in the air sacs during times when spiracles have been closed for water conservation
why do bony fish have a large oxygen requirement?
Because they are very active
Can gases pass through the scaly surface of fish?
No
do fish get their oxygen from air or water ?
From the water
where is the concentration of oxygen higher- in the air or in water?
In the air- the concentration of oxygen is much lower in the water
what is the operculum?
the flap of tissue on either side of the fish’s head
What is behind the operculum?
The opercular cavity
what can be found inside the opercular cavity?
The gills
what do the gills consist of ?
gill arches
what extends from each gill arch?
gill filaments
what are gill filaments covered with?
gill lamellae (gill plates)
are the gill lamellae where has exchange in a fish occurs?
Yes
how are the gill lamellae adapted for the efficient diffusion of gases?
- they have a massive surface area for diffusion to occur
- there’s a very short diffusion distance between the walls of the lamellae and the bloodstream
- gill lamellae have an extensive network of capillaries
- The counter current exchange system
Describe the counter current exchange system
-Water and blood move in opposite directions
-Blood with a low concentration of oxygen passes into the capillaries of the gill lamellae
- As the blood passes through the gill lamellae, oxygen diffuses from the water into the blood
- Oxygenated blood passes out of the gill lamellae and leaves the gills
what is the major advantage of the counter current exchange system?
A steep concentration gradient is always maintained
what is it called when water and blood flow in the same direction ?
Parallel flow
with a counter current exchange system , roughly what percentage of oxygen in the water diffuses into the bloodstream?
About 80%
Describe how bony fish maintain constant water flow through the gas exchange system
- A bony fish opens its mouth and water flows into the buccal cavity (the mouth space)
- The floor of the buccal cavity lowers and increases the volume available for water
- The fish then shuts the operculum and this increases the volume of the opercular cavity
- Due to the increased volume, the pressure in the opercular cavity falls and the floor of the buccal cavity moves upwards.
- This increases the pressure of water and so the water moves down a pressure gradient and flows over the gills in the opercular cavity.
- Now, the fish closes its mouth and opens the operculum.
- The sides of the opercular cavity squeeze inwards on the water.
- This increases the pressure of water and forces it out of the operculum
Can water enter a bony fish’s mouth even when it’s not swimming?
Yes
What are the 2 main adaptations of the trachea?
- The walls of the trachea contain cartilage. This prevents the walls of the trachea from collapsing when we inhale
- The trachea walls are lined with ciliated epithelia and goblet cells
what is the function of the goblet cells?
They secrete mucus, which traps dust particles and pathogens
What do the ciliated epithelial cells do?
The cilia wafts mucus to the throat. The mucus is then swallowed and the dust and the pathogens are then digested by the enzymes in the stomach
does the bronchi also contain cartilage, ciliated epithelia and goblet cells ?
Yes
what do the bronchioles contain?
Cartilage and smooth muscle.
what do the elastic fibres between the alveoli do during breathing?
they stretch and recoil
how thick are the walls of the capillary?
Only one cell thick
how thick are the walls of the alveoli?
Only one cell thick
Use test for alveoli adaptations
What is another name for breathing?
Ventilation
What 2 sets of muscles work together to change the volume of the throrax during ventilation?
The intercostal muscles and the diaphragm
What happens during inhalation?
-The intercostal muscles contract
- The diaphragm contracts and flattens
- The volume of the thorax increases
- Air pressure in the lungs decreases
-Because air pressure in the lungs is now less than atmospheric pressure, air is drawn into the lungs
-Air consequently moves into the alveoli
What happens during exhalation?
- The intercostal muscles relax
- The diaphragm relaxes and becomes domed
- The volume of the thorax decreases
-Now, the air pressure in the lungs is greater than atmospheric pressure and so air is pushed out of the lungs
Why is inhalation an active process?
Because it requires muscle contraction
Why is exhalation a passive process?
Because the muscles relax
What membranes are the lungs surrounded by?
Pleural membranes
What is between the pleural membranes?
Pleural fluid, which acts as a lubricant as the lung volume changes
In which occasion can exhalation be an active process?
When you exhale strongly during intense exercise . In this case the internal intercostal muscles come to play.
What is mass transport?
When molecules are carried in a transport medium, such as blood, through a circulatory system
Describe a single circulatory system
Blood only passes through the heart once in a single circuit
What’s a major problem with a single circulatory system?
Oxygen is delivered to the body cells a lot slower
What’s happens to the pressure of the blood after it moves through the capillaries?
The pressure of the blood decreases
Describe a double circulatory system
Blood passes through the heart twice in a single circuit. This ensures that blood moves to the body tissues rapidly and under high pressure
What is a closed circulatory system?
Where the blood is contained in blood vessels
What are the advantages of a closed circulatory system?
-The blood can move rapidly
- Oxygen can be delivered to respiring tissues quicker and carbon dioxide can be removed from the body quicker
Do insects have an open or closed circulatory system?
They have an open circulatory system
What do insects contain instead of blood?
A fluid called haemolymph
What does haemolymp carry?
Nutrients such as sugars, but not oxygen
Is an open circulatory system enclosed in vessels or not?
Not
Is the blood in the left side of the heart oxygenated or deoxygenated?
Oxygenated
Is the blood in the right side of the heart oxygenated or deoxygenated?
Deoxygenated
What arteries are the kidneys supplied by?
The renal arteries
After passing through the arterioles, what does the oxygenated blood travel through?
The capillaries
Venules then….
Veins
What are the veins from the kidneys called?
The renal veins
Describe the structure of an artery
-Very thick walls to allow the artery to withstand high pressure
-Collagen rich outer layer , which strengthens the artery wall against the pressure of the blood
-Smooth muscle layer. When this layer contracts, the diameter of the artery narrows and this allows the body to control how much blood flows to different organs
- elastic layer that is rich in elastic fibres. This allows the artery to recoil and stretch
-Lumen is lined with endothelial cells which allows for a very smooth surface and reduces friction
What is the job of the arterioles?
To deliver oxygenated blood to the capillaries
is the blood pressure in arterioles higher or lower than the blood pressure in arteries?
Lower
Describe the structure of an arteriole
-Collagen layer and the elastin layer are thinner than that of the arteries
-Thicker smooth muscle later than arteries because they control blood flow into the capillaries
When does vasodilation take place?
When an organ requires an increased amount of oxygen
Describe the structure of the capillaries
-Have a wall that is one cell thick allowing greater time for the diffusion of molecules to occur
-Capillary lumen is only slight bigger than the lumen of the red blood cells. This means that red blood cells can move slowly and in single file through the capillaries, allowing for more time for the diffusion of molecules to occur
-Capillaries have pores in their walls. These gaps allow tissue fluid to pass out of the blood. They also allow the white blood cells to leave the bloodstream
What does tissue fluid do?
It bathes the cells and provides them with essential molecules, such as glucose and amino acids
Describe the structure of veins
-Have thin walls because veins don’t have to withstand high pressure
-Large lumen to carry a great volume of blood
-Thinner elastic fibre layer because blood is under low pressure so veins don’t need to stretch and recoil
-Lumen has an internal lining of endothelial cells to create a smooth surface that reduces the friction between the blood and the wall of the vein
- Valves to ensure that there’s no backflow and that blood moves in the right direction
What does the blood plasma contain?
Red blood cells, White blood cells, platelets, glucose, amino acids, mineral ions, oxygen, plasma proteins
What does tissue fluid do?
It transfers molecules, such as glucose and oxygen, to the tissue cells. It leaves the capillaries near the arterial end
Describe the movement of fluid in and out of the capillary
- at the arterial end of the capillaries, hydrostatic pressure was greater than oncotic pressure, so fluid moves out of the capillary
- At the venous end of the capillary, hydrostatic pressure was lower than oncotic pressure , so fluid moves into the capillaries
What happens to tissue fluid that isn’t reabsorbed back into the blood?
This fluid drains into lymph capillaries and becomes lymph flyid
Do lymph vessels have valves?
Yes
What adaptations do red blood cells have for transporting oxygen?
-Biconcave shape, to give a large surface area to
-Contains lots of haemoglobin
-No nucleus to give more space for haemoglobin
How many polypeptide chains does haemoglobin have?
4
What is each of the 4 polypeptide chains in haemoglobin bound to?
A prosthetic group called haem
Which iron ion does haem contain?
Fe2+
How many molecules of oxygen can one haemoglobin molecule bind to?
1 and as oxygen is diatomic, haemoglobin binds to 8 oxygen atoms altogether
What is it called when oxygen binds to haemoglobin?
Oxyhaemoglobin
What is on the y axis of the oxygen dissociation curve?
The percentage saturation of haemoglobin with oxygen
What is on the x axis of the oxygen dissociation curve?
The partial pressure of oxygen (Kpa)
At low partial pressures of oxygen…
Haemoglobin has a low affinity for oxygen
Why does the affinity of hemoglobin for oxygen increase after one oxygen molecule has bound?
Because as one oxygen molecule binds , the polypeptide chain opens, exposing the other 3 haem groups. The affinity of the haem groups for oxygen therefore increases
The partial pressure of oxygen is high in the lungs so..
Oxygen readily combines with haemoglobin
The partial pressure of oxygen is low in the tissues so….
Oxygen is readily released by haem
What happens when the partial pressure of carbon dioxide is high?
Haemoglobin releases oxygen more readily and it’s affinity for oxygen decreases
Is the oxygen dissociation curve shifted to the left or to the right when there’s a high partial pressure of carbon dioxide?
The right
Is the Bohr affect when a high partial pressure of carbon dioxide causes haemoglobins affinity for oxygen to decrease?
Yes
Describe the carriage of carbon dioxide in the blood
-The carbon dioxide produced in respiring tissues diffuses into the blood where most of it enters the red blood cells.
- In the red blood cells, the enzyme carbonic anhydrase catalyses the reaction between carbon dioxide and water. Carbonic acid is produced
- Carbonic acid is a weak acid and so dissociate into hydrogen ions and hydrogen carbonate ions.
- The hydrogen ions can combine with haemoglobin to produce haemoglobinic acid
- Hydrogen ions act as a pH Buffer and when haemoglobinic acid is formed, the haemoglobin is forced to drop some of the oxygen it’s carrying
- Some of the carbon dioxide that enters the red blood cells doesn’t undergo the process described above and instead combines directly with haemoglobin to form carbaminohaemoglobin
How is fetal haemoglobin different to adult haemoglobin?
Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin . This increases the oxygen transfer across the placenta from the mother to the baby
Does carbon dioxide from the foetus diffuse into the maternal blood?
Yes. This carbon dioxide lowers the oxygen affinity of the maternal haemoglobin and
In which 3 ways is carbon dioxide transported around the body?
-Dissolved in the blood plasma
-Carried as carbaminohaemoglobin in red blood cells
- as hydrogen carbonate ions in the blood plasma
How many molecules of carbon dioxide can one molecule of haemoglobin react with?
4
Do the ventricles have thicker muscular walls than the atria?
Yes
What are the atria separated from the ventricles by?
The atrioventricular valves (AV valves)
What is the left AV valve called?
The bicuspid valve
What is the right AV valve called?
The tricuspid valve
What does the septum do?
It prevents any blood from passing directly between the 2 sides of the heart
What does the superior vena cava
Brings blood from the head and other parts of the body back to the heart
What does the inferior Vena Cava do?
Ir brings deoxygenated blood back to the heart from lower parts
why is the heart myogenic?
Because it triggers its own heartbeat- no external factors come to play
What is another name for the pacemaker?
The SAN
What is another name for the SAN?
The pacemaker
What happens when the cells in the SAN become electrically ecited?
A wave of electrical excitement spreads across the atria and this causes the atria to contract
What is the contraction of the atria called?
Atrial systole
What is the AVN connected to?
Conducting fibres called Purkyne fibres
What is the Bundle of His?
Where the Purkyne fibres are bundled together
Where do the Purkyne fibres run down to ?
The apex
What happens after the AVN detects the electrical excitation passing over the atria?
The AVN then transmits the electrical excitation down to the Purkyne fibres. This electrical excitation causes the ventricles to contract
In which direction do the ventricles contract?
From the apex upwards
Why do the ventricles contract from the apex upwards?
To ensure that the maximum volume of blood is pumped out of the ventricles
Why is there a slight delay before the AVN triggers a wave of excitation down the Purkyne fibres?
To ensure that the ventricles contract after the atria have contracted
Describe the initiation and cooordinatiion of the action of the heart
1) A wave of electrical excitation spreads out from the SAN across both the atria. As a result, the atria contract and atrial systole occurs.
2) The electrical wave is stoppepd from passing through to the ventricles by the non consucting atriventricular septum.
3) The AVN picks up the electrical wave and after a short delay, sends an impulse down the bundle of His.
4) The electrical signal is down the bundle of His to the Apex. From the apex, the electrical signal branches into smaller Purkyne fibres,
5) Both ventricles contract from the ventricles upwards. This is ventricular systole.
What is the cardiac cycle?
The different steps involved in producing a single heartbeat
What does systole mean?
Contracting
What does diastole mean?
Relaxing
Describe the cardiac cycyle
1) Blood flows into the atria through the vena cava and the pulmonary vein. This causes the pressure in the atria to rise.
2) At a certain point, the pressure in the atria is greater than the pressure in the ventricles.
3) This causes the Atrioventricular valves to open, allowing blood to flow down the atria and into the ventricles.
4) The atria then contract and atrial systole takes place. This pushes the remaining blood from the atria and to the ventricles
5) The ventricles then contract and enter ventricular systole. The pressure in the ventricles now rises rapidly and because the ventricular pressure is now greater than the atrial pressure, the atrioventricular valves close.
6) This prevents any blood from moving back into the atria from the ventricles
7) The semilunar valves in the aorta and pulmonary artery are also open. So blood is pumped from the ventricles and out of the heart .
8) Finally, the ventricles relax and enter ventricular diastole
9) At some point, the pressure in the ventricles falls below the pressure in the pulmonary artery and aorta. This causes the semilunar valves to shut and this prevents blood from flowing back into the ventricles.
10) The heart is now ready to enter the next cardiac cycle
What does ECG stand for?
Electrocardiogram
What does the P wave on an ECG trace show?
The contraction of the atria/ atrial systole
What does the QRS wave on an ECG trace show?
The contraction of the ventricles/ ventricular systole
What does the T wave on an ECG trace show?
the relaxation of the ventricles/ ventricular disastole
What is the heart rate?
Heart beats per minute
What is a slow heart beat called?
Bradycardia
What is a fast heartbeat called?
Tachycardia
What is a fast and irregular heartbeat called?
Atrial fibrillation
What is an ectopic heartbeat?
When it feels as though the herat has missed a beat
What is the cardiac output?
The volume of blood pumped into the circulatory system in one minute
What is the stroke volume?
The volume of blood pumped out of a ventricle during each contraction
What is a typical stroke volume?
Around 70cm^3
What is the equation for cardiac output?
Cardiac output (cm^3/min) = heart rate(bom) X stroke volume (cm^3)
How do you convert the cardiac outfit from cm^3/min to dm^3/min?
You divide by 1000
What is the tidal volume?
The volume of air inhaled/exhaled during regular breathing
What is the vital capacity?
The maximum volume of air inhaled/exhaled in 1 breath
Why is there always resdiual volume left behind in the lungs?
Because the lungs can’t be completely compressed
What does the smooth muscle do?
It constricts the airway and controls the flow of air
What do the elastic fibres do?
They stretch and recoil
When the drum moves up, is the subject breathing in or out?
They’re breathing out
When the drum moves down, is the subject breathing in or out?
In
How do you use a spirometer to measure the rate of oxygen uptake?
- You measure the volume of oxygen used in a given time
- You draw a line along the tips of peaks/troughs
-Divide volume by time taken
Why is a nose clip used when using a spirometer?
To ensure all the air breathed comes from the air chamber
How do substances that are dissolved in the blood plasma, such as oxygen and glucose, enter the tissue fluid from the capillaries?
-The substances diffuse from an area of high concentration to an area of low concentration.
-They hydrostatic pressure in the capillaries is higher than the the hydrostatic pressure in the tissue fluid.
-So fluid moves down a pressure gradient and so do the dissolved substances like Oxygen
What effect might tachycardia have on the heart?
-Less blood will leave the heart because ventricles won’t have time to fill before contracting
Why doesn’t tissue fluid contain erythrocytes?
because the erythrocytes are too big too fit through the pores in the capillary walls
Describe the role of haemoglobin in transporting oxygen around the body
- Haemoglobin has a high affinity for oxygen
- Oxygen binds to haemoglobin in the lungs
- This forms oxyhaemoglobin
- The oxygen is released in respiring tissues
Describe the pressure changes in the blood as it flows through the circulatory system from the aorta to the veins?
-The pressure drops as the distance from the heart increases
- The greatest pressure drop is while the blood is in the arteries
- The pressure remains constant in the veins
What causes the overall changes in pressure as blood flows from the aorta to the arteries and from the arteries to the capillaries?
- blood flows into a larger number of vessels
- the total cross-sectional area of the arteries is greater than the aorta
- the total cross-sectional area of the capillaries is greater than the arteries
Explain why it’s important that the pressure changes as blood flows from the aorta to the capillaries?
Because the capillary wall is thin and it can’t withstand the high pressure
How do pressure changes in the heart bring about the closure of the atrioventricular (bicuspid valve)?
- The ventricle contracts
- This raises ventricular pressure
- The movement of blood generated by ventricular systole causes the valve to shut
