transport in animals Flashcards
The circulatory system is
a system of blood vessels with a pump and valves to ensure one-way flow of blood
fish circulatory system
Fish have a two chambered heart and a single circulation This means that for every one circuit of the body, the blood passes through the heart once
Double circulation in mammals
Mammals have a four chambered heart and a double circulation
This means that for every one circuit of the body, the blood passes through the heart twice
The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (the pulmonary circulation)
The left side of the heart receives oxygenated blood from the lungs and pumps it to the body (the systemic circulation)
Advantages of a Double Circulation
Blood travelling through the small capillaries in the lungs loses a lot of pressure that was given to it by the pumping of the heart, meaning it cannot travel as fast
By returning the blood to the heart after going through the lungs its pressure can be raised again before sending it to the body, meaning cells can be supplied with the oxygen and glucose they need for respiration faster and more frequently
the heart basics
The heart is labelled as if it was in the chest so what is your left on a diagram is actually the right hand side and vice versa
The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs
The left side of the heart receives oxygenated blood from the lungs and pumps it to the body
Blood is pumped towards the heart in veins and away from the heart in arteries
The two sides of the heart are separated by a muscle wall called the septum
The heart is made of muscle tissue which is supplied with blood by the coronary arteries
Arteries carry blood … the heart
Away from
structure heart
The ventricles have thicker muscle walls than the atria as they are pumping blood out of the heart and so need to generate a higher pressure
The left ventricle has a thicker muscle wall than the right ventricle as it has to pump blood at high pressure around the entire body, whereas the right ventricle is pumping blood at lower pressure to the lungs
The septum separates the two sides of the heart and so prevents mixing of oxygenated and deoxygenated blood
The Function of the Valves
The basic function of all valves is to prevent blood flowing backwards
There are two sets of valves in the heart:
The atrioventricular valves separate the atria from the ventricles
The valve in the right side of the heart is called the TRICUSPID and the valve in the left side is called the BICUSPID
These valves are pushed open when the atria contract but when the ventricles contract they are pushed shut to prevent blood flowing back into the atria
The semilunar valves are found in the two blood arteries that come out of the top of the heart
They are unusual in that they are the only two arteries in the body that contain valves
These valves open when the ventricles contract so blood squeezes past them out of the heart, but then shut to avoid blood flowing back into the heart
Pathway of Blood through the Heart
Deoxygenated blood coming from the body flows into the right atrium via the vena cava
Once the right atrium has filled with blood the heart gives a little beat and the blood is pushed through the tricuspid (atrioventricular) valve into the right ventricle
The walls of the ventricle contract and the blood is pushed into the pulmonary artery through the semi lunar valve which prevents blood flowing backwards into the heart
The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place (this is why there has to be low pressure on this side of the heart – blood is going directly to capillaries which would burst under higher pressure)
Oxygen rich blood returns to the left atrium via the pulmonary vein
It passes through the bicuspid (atrioventricular) valve into the left ventricle
The thicker muscle walls of the ventricle contract strongly to push the blood forcefully into the aorta and all the way around the body
The semi lunar valve in the aorta prevents the blood flowing back down into the heart
Exercise & Heart Rate
Heart activity can be monitored by using an ECG, measuring pulse rate or listening to the sounds of valves closing using a stethoscope
Heart rate (and pulse rate) is measured in beats per minute (bpm)
To investigate the effects of exercise on heart rate, record the pulse rate at rest for a minute
Immediately after they do some exercise, record the pulse rate every minute until it returns to the resting rate
This experiment will show that during exercise the heart rate increases and may take several minutes to return to normal
Why does Heart Rate Increase during Exercise?
So that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen for increased respiration
An increase in heart rate also allows for waste products to be removed at a faster rate
Following exercise, the heart continues to beat faster for a while to ensure that all excess waste products are removed from muscle cells
It is also likely that muscle cells have been respiring anaerobically during exercise and so have built up an oxygen debt
This needs to be ‘repaid’ following exercise and so the heart continues to beat faster to ensure that extra oxygen is still being delivered to muscle cells
Coronary Heart Disease
The heart is made of muscle cells that need their own supply of blood to deliver oxygen, glucose and other nutrients and remove carbon dioxide and other waste products
The blood is supplied by the coronary arteries
If a coronary artery becomes partially or completely blocked by fatty deposits called ‘plaques’ (mainly formed from cholesterol), the arteries are not as elastic as they should be and therefore cannot stretch to accommodate the blood which is being forced through them – leading to coronary heart disease
Partial blockage of the coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called angina
Complete blockage means cells in that area of the heart will not be able to respire and can no longer contract, leading to a heart attack
Risk Factors for Coronary Heart Disease
Reducing the risks of developing coronary heart disease:
Quit smoking
Reduce animal fats in diet and eat more fruits and vegetables – this will reduce cholesterol levels in the blood and help with weight loss if overweight
Exercise regularly – again, this will help with weight loss, decrease blood pressure and cholesterol levels and help reduce stress
Treatment of coronary heart disease:
Aspirin can be taken daily to reduce the risk of blood clots forming in arteries
Surgical treatments include:
- Angioplasty
A narrow catheter (tube) is threaded through the groin up to the blocked vessel
A tiny balloon inserted into the catheter is pushed up to the blocked vessel and then inflated
This flattens the plaque against the wall of the artery, clearing the blockage
To keep the artery clear, a stent (piece of metal / plastic mesh) is also inserted which pushes against the wall of the artery
Sometimes the stent is coated with a drug that slowly releases medication to prevent further build up of plaque
Inserting a stent into a blocked artery
- Coronary bypass surgery
A piece of blood vessel is taken from the patient’s leg, arm, or chest and used to create a new passage for the flow of blood to the cardiac muscle, bypassing the blocked area
The number of bypass grafts gives rise to the name of the surgery, so a ‘triple heart bypass’ would mean three new bypass grafts being attached
Arteries
Carry blood at high pressure away from the heart
Carry oxygenated blood (other than the pulmonary artery)
Have thick muscular walls containing elastic fibres
Have a narrow lumen
Speed of flow is fast
Veins
Carry blood at low pressure towards the heart
Carry deoxygenated blood (other than the pulmonary vein)
Have thin walls
Have a large lumen
Contain valves
Speed of flow is slow
Capillaries
Carry blood at low pressure within tissues
Carry both oxygenated and deoxygenated blood
Have walls that are one cell thick
Have ‘leaky’ walls
Speed of flow is slow
How Structure of Blood Vessels is Adapted to their Function
Arteries
Have thick muscular walls containing elastic fibres to withstand high pressure of blood and maintain the blood pressure as it recoils after the blood has passed through
Have a narrow lumen to maintain high pressure
How Structure of Blood Vessels is Adapted to their Function
Veins
Have a large lumen as blood pressure is low
Contain valves to prevent the backflow of blood as it is under low pressure
How Structure of Blood Vessels is Adapted to their Function
Capillaries
Have walls that are one cell thick so that substances can easily diffuse in and out of them
Have ‘leaky’ walls so that blood plasma can leak out and form tissue fluid surrounding cells
Arterioles & Venules
As arteries divide more as they get further away from the heart, they get narrower
The narrow vessels that connect arteries to capillaries are called arterioles
Veins also get narrower the further away they are from the heart
The narrow vessels that connect capillaries to veins are called venules
Shunt Vessels
Sometimes the cardiovascular system need to redistribute the blood to specific areas of the body
For example:
During exercise, more of it goes to the working muscles and less of it goes to other body organs such as the digestive system
When we are hot, more blood flows through the surface of the skin and when we are cold less blood flows through the surface of the skin
This redirection of blood flow is caused by the use of a vascular shunt vessel
The shunt vessels can open or close to control the amount of blood flowing to a specific area
Circulation around the Body
lood is carried away from the heart and towards organs in arteries
These narrow to arterioles and then capillaries as they pass through the organ
The capillaries widen to venules and finally veins as they move away from the organs
Veins carry blood back towards the heart
Lymph Fluid
The walls of the capillaries are so thin that water, dissolved solutes and dissolved gases easily leak out of them / pass through the walls from the plasma into the tissue fluid surrounding the cells
Cells exchange materials (such as water, oxygen, glucose, carbon dioxide, mineral ions) across their cell membranes with the tissue fluid surrounding them by diffusion, osmosis or active transport
More fluid leaks out of the capillaries than is returned to them and this excess fluid passes into the lymphatic system and becomes lymph fluid
Lymph Vessels & Nodes
The lymphatic system is formed from a series of tubes which flow from tissues back to the heart
It connects with the blood system near to the heart, where lymph fluid is returned to the blood plasma
Lymph nodes are small clusters of lymphatic tissue found throughout the lymphatic system, especially in the neck and armpits
Large numbers of lymphocytes are found in lymph nodes
Tissues associated with the lymphatic system, such as bone marrow, produce these lymphocytes
Lymphocytes play an important role in defending the body against infection
Blood consists of
red blood cells, white blood cells, platelets and plasma
White Blood Cells basics
White blood cells are part of the body’s immune system, defending against infection by pathogenic microorganisms
There are two main types, phagocytes and lymphocytes
Phagocytes
Carry out phagocytosis by engulfing and digesting pathogens
Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it
They can be easily recognised under the microscope by their multi-lobed nucleus and their granular cytoplasm
Lymphocytes
Produce antibodies to destroy pathogenic cells and antitoxins to neutralise toxins released by pathogens
They can easily be recognised under the microscope by their large round nucleus which takes up nearly the whole cell and their clear, non granular cytoplasm
Functions of the Parts of Blood
Plasma is important for the transport of carbon dioxide, digested food (nutrients), urea, mineral ions, hormones and heat energy
Red blood cells transport oxygen around the body from the lungs to cells which require it for aerobic respiration
They carry the oxygen in the form of oxyhaemoglobin
White blood cells defend the body against infection by pathogens by carrying out phagocytosis and antibody production
Platelets are involved in helping the blood to clot
Blood Clotting
Platelets are fragments of cells which are involved in blood clotting and forming scabs where skin has been cut or punctured
Blood clotting prevents continued / significant blood loss from wounds
Scab formation seals the wound with an insoluble patch that prevents entry of microorganisms that could cause infection
It remains in place until new skin has grown underneath it, sealing the skin again
When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding
A series of reactions occur within the blood plasma
Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot.
The clot eventually dries and develops into a scab to protect the wound from bacteria entering
