mass transport in animals Flashcards
Why is mass transport necessary? [3]
- most cells too far away from exchange surface for diffusion alone
- maintains final diffusion gradients
- maintains relatively stable environment for cells
What is a closed double circulatory system?
blood passes through the heart twice for each complete circulation of the body
What is systemic circulation?
oxygenated blood in left side of heart pumped to body > deoxygenated blood returns to right side
What is pulmonary circulation?
deoxygenated blood in right side of heart pumped to lungs > oxygenated blood returns to left side of heart
Why is the closed double circulatory system important for mammals? [2]
- prevents mixing of oxygenated and deoxygenated blood
- blood can be pumped at a higher pressure to body
What do the Coronary Arteries do?
Deliver oxygenated blood to cardiac muscle
What does the Aorta do?
takes OXYGENATED blood from heart → respiring tissues
What does the Vena Cava do?
takes DEOXYGENATED blood from respiring tissues → heart
What does the Pulmonary Artery do?
takes DEOXYGENATED blood from heart → lungs
What does the Pulmonary Vein do?
takes OXYGENATED blood from the lungs → heart
Which vessel carries blood at the lowest pressure?
Vena Cava
Which vessel carries blood at the highest pressure?
Aorta
How does the structure of the Aorta relate to its function? [3]
Elastic tissue allows stretching and recoiling > smooths the flow of blood and maintains pressure
Thick wall > can withstand high pressure
Aortic valve > prevents backflow of blood
What is the function of the Septum?
To prevent the mixing of oxygenated and deoxygenated blood
What is a hole in the heart?
A hole in the septum between two ventricles
What is the function of the valve tendons (heart strings) ?
only allows valves to open in one direction
Where do the renal arteries/veins lead from/to?
The Kidneys
What do the Atrioventricular valves do?
Prevent backflow of blood from ventricles to atria
Name the Atrioventricular Valves
Tricuspid Valve / Bicuspid Valve (Mitral Valve)
What do the Semi-lunar valves do?
Prevent backflow of blood from arteries to ventricles
Name the Semi-lunar valves
Pulmonary Valve / Aortic Valve
Why does the left ventricle have a thicker muscle wall than the right?
oxygenated blood from left side has to travel greater distance around the body, so thicker muscle wall generates higher blood pressure
deoxygenated blood from right side has to travel a small distance to the lungs where high pressure would damage alveoli
Describe the structure of Arteries [4]
- thick muscle
- elastic fibre walls
- narrow lumen
- high blood pressure
What are Arterioles?
division of arteries to smaller vessels which can direct blood to different capillaries / areas
Describe the structure of Arterioles [4]
- thicker muscle wall than arteries
- thick elastic fibre walls
- narrow lumen
- very high blood pressure
Explain how an Arteriole can reduce blood flow to the capillaries [4]
- Arterioles have a very thick muscle tissue
- can contract
- narrowing lumen
- reducing blood flow
What are Venules?
Divisions of veins which carry blood from capillaries to veins
Describe the structure of Veins [5]
- Very little elastic and muscle tissue
- Wider lumen than arteries
- low blood pressure
- Valves
- Contraction of skeletal muscles squeezes veins, maintaining blood flow
What is the role of Capillaries?
Capillaries allow the efficient exchange of gases and nutrients between blood and tissue fluid
What factor limits the minimum internal diameter of the lumen of a capillary?
The diameter of a red blood cell
What is the relationship between the surface area and the blood velocity and why? [5]
The lower the surface area the higher the velocity
- capillaries is where there is the highest surface area
- this is where diffusion in and out of blood stream takes place - diffusion is more effective at a lower velocity as there is more time for substances to diffuse
- however in larger blood vessels diffusion doesn’t take place so blood can move at a higher velocity
Describe how capillaries are adapted for efficient exchange [5]
- Capillary epithelium is one cell thick > short diffusion pathway
- Capillary bed is made of a large network of branched capillaries > increased surface area
- Narrow lumen > reduces flow rate, more time for exchange
- Capillaries permeate tissues > no cell far away, short diffusion distance
- Pores in walls between cells > Allows substances to escape
(e.g. white blood cells to deal with infections)
What is Tissue Fluid? [3]
- The fluid surrounding cells / tissues
- Provides respiring cells with
(e.g. water / oxygen / glucose / amino acids) - Enables waste substances to move back into the blood
(e.g. urea, lactic acid, carbon dioxide)
Describe the formation of Tissue Fluid [3]
- Higher blood pressure inside capillaries than tissue fluid
- Forces fluid / water out of capillaries into spaces around cells
- Large plasma proteins remain in capillary, as too large
Describe the return of tissue fluid to the circulatory system [4]
- Blood pressure reduces as fluid leaves capillary
- an increasing concentration of plasma proteins lowers the water potential in the capillary below the water potential of the tissue fluid
- Water re-enters the capillaries from the tissue fluid by osmosis down a water potential gradient
- Excess water taken up by lymph system (lymph capillaries) and is returned to the circulatory system
How can low concentration of protein in blood plasma lead to an accumulation of tissue fluid? [3]
- Water potential in capillary higher so more water moves into tissue fluid by osmosis
- More tissue fluid formed at arteriole end
- Less water absorbed back into capillary by osmosis
How can high blood pressure lead to an accumulation of tissue fluid? [4]
- Increases outward pressure from arterial end of capillary / reduces inward pressure at venule end of capillary
- So more tissue fluid formed
- Less tissue fluid is reabsorbed
- The lymph system is not able to drain tissues fast enough
Why may the volume of blood leaving the capillary network be less than the volume entering?
Fluid making up that volume is tissue fluid or fluid in the lymphatic system
What are the 3 stages of the Cardiac Cycle?
Atrial systole
Ventricular systole
Diastole
Describe Atrial Systole [5]
- Atria contract
- Decreasing volume + increasing pressure in atria
- Pressure inside atria greater than pressure inside ventricles
- Atrioventricular valves forced open
- Blood pushed into ventricles
Describe Ventricular Systole [6]
- Ventricles contract
- Decreasing volume + increasing pressure in ventricles
- Pressure inside ventricles greater than pressure inside arteries
- Atrioventricular valves shut
- Semi-lunar valves open
- Blood pushed out of heart through arteries
Describe Diastole [3]
- Atria and ventricles relax
- Increasing volume + decreasing pressure inside chambers
- Blood from veins fills atria (increasing pressure inside atria slightly) and flows passively to ventricles
What is Cardiac Output?
amount of blood pumped out of the heart per minute
Pressure in Ventricle > Pressure in Atrium
Atrioventricular Valves CLOSED
Semi-lunar Valves OPEN
Pressure in Ventricle < Pressure in Atrium
Atrioventricular Valves OPEN
Semi-lunar Valves CLOSED
Give 6 examples of risk factors, increasing the chance of cardiovascular disease
- Age
- Diet high in salt or saturated fat
- High consumption of alcohol
- Stressful lifestyle
- Smoking cigarettes
- Genetic factors
Where is Haemoglobin found?
In red blood cells
How are Red Blood Cells Adapted to their function? [2]
- No nucleus > contain more haemoglobin
- Biconcave shape > increase surface area for rapid diffusion/absorption of oxygen
Describe the structure of Haemoglobin [2]
- Quaternary structure protein > made of 4 polypeptide chains
- Each polypeptide chain contains a Haem group containing an iron ion (Fe2+) which combines with oxygen
What is pO2? [3]
Partial pressure of oxygen
- Reflects the amount of oxygen gas dissolved in the blood
- Measuring the effectiveness of the lungs in pulling oxygen into the blood stream
Describe the process of oxygen being loaded, transported and unloaded in the blood
Haemoglobin can carry 4 oxygen molecules
(one at each Haem group)
In the lungs…
- at a high pO2
- haemoglobin has a high affinity for oxygen
- oxygen readily associates with haemoglobin
At respiring tissues…
- at a low pO2
- haemoglobin has a low affinity for oxygen
- oxygen readily dissociates from haemoglobin
- Also, concentration of CO2 is high, increasing the rate of unloading (Bohr effect)
Describe haemoglobin and how its affinity for oxygen changes as the molecules bind
As 1st oxygen molecule binds >
Haemoglobin has a low affinity for oxygen
After the 1st oxygen molecule binds >
shape of haemoglobin changes >
making it easier for 2nd & 3rd oxygen molecules to bind >
haemoglobin has a higher affinity for oxygen
After the 3rd molecule binds >
haemoglobin starts to become saturated >
the shape of haemoglobin changes >
making it harder for other molecules to bind >
Haemoglobin has a low affinity for oxygen
The Bohr Effect [6]
- When rate of respiration is high (e.g. during exercise)
- releases CO2
- High pCO2 lowers pH
- Reduces haemoglobin’s affinity for oxygen as haemoglobin changes shape
- Increases rate of oxygen unloading
- Advantageous because provides more oxygen for muscles/tissues for aerobic respiration
What does an organism’s haemoglobin having a higher affinity for oxygen mean and who is it advantageous to?
More oxygen associates with haemoglobin more readily at a higher pO2
BUT
dissociates less readily
Advantageous to organisms…
- living in high altitudes
- living underground
- foetuses
What does an organism’s haemoglobin having a lower affinity for oxygen mean and who is it advantageous to?
Oxygen dissociates from haemoglobin more readily to respiring cells at a lower pO2
BUT
associates less readily
Advantageous to organisms…
- high rate of respiration / metabolic rate
(e.g. small / active organisms)
What are the 4 components of the blood and what are their functions?
Plasma > fluid containing: glucose, water, urea, ions
Platelets > helps blood to clot
Red Blood Cells > carries oxygen
White Blood Cells > fights infections
What is the effect of exercise? [2]
-Increased heart rate
- Increased stroke volume
How do you convert cm3 > dm3?
x1000
What is the cardiac output equation?
cardiac output = stroke volume x heart rate
(dm3/minute) (dm3) (bpm)
Heart Disease [5]
Atheroma >
Plaque >
Aneurysm / Thrombosis >
Myocardial Infarction
Atheroma
a build-up of fat on the inside an artery
Plaque [3]
- The atheroma can collect minerals and become hardened to form a rough plaque.
- The plaques bulge into the lumen of the artery
- causing it to narrow so that blood flow is reduced
Aneurysm [3]
- plaque weakens the wall of the artery
- weakened points swell to form a balloon-like structure called an aneurysm
- if the wall is particularly weak it may burst
Thrombosis [3]
- atheroma breaks through the endothelium
- forms a rough surface that interrupts the smooth flow of blood
- may block the blood vessel reducing or preventing blood supply to the tissues
Myocardial Infarction [2]
- thrombosis prevents oxygen reaching the cardiac cells beyond the blockage
- The death of these cells is the MI (heart attack)
