Circulation Flashcards
What is the transport system in many animals that moves substances made internally around the body made up of?
The heart and the circulatory system
What are the features mass transport systems have in common?
They have:
• a system of vessels that carry substances (usually tubes)
• a way of making sure that substances are moved in the right direction e.g. nutrients in and waste out
• a means of moving materials fast enough to supply the needs of an organism e.g. the pumping of the heart
• a suitable transport medium
What type of circulatory system do insects have?
An open one with the blood circulating in large open spaces
What is a close circulatory system?
Where the blood is contained within tubes
Fish have a single circulation system. What does this consist of?
The heart pumps deoxygenated blood to the gills (the organs of gas exchange) where the blood takes in oxygen becoming oxygenated and giving up CO2 at the same time. The blood then travels on around the rest of the body giving up oxygen to the body cells before returning to the heart
Why do birds and mammals need far more oxygen than fish?
Because they have to move around without the support of water and also maintain a constant body temperature that is higher than their surroundings. This takes a lot of resources so their cells need plenty of oxygen and glucose
Birds and mammals have a double circulatory system. Which two circulatory systems does it involve and what do they do?
- the systemic circulation carries oxygenated blood from the heart to the cells of the body where oxygen is used and carries deoxygenated blood back to the heart
- the pulmonary circulation Carries deoxygenated blood from the heart to the lungs to be oxygenated and carries oxygenated blood from the lungs back to the heart
What are the advantages of the separate circuits of a double circulatory system?
- it makes sure that oxygenated and deoxygenated blood do not mix
- the fully oxygenated blood can be delivered quickly to the body tissues at high pressure. If the oxygenated blood from the lungs went straight to the body tissues it would be travelling at very low pressure as it has to be in low pressure in the lungs so it doesn’t damage the tiny blood vessels
What is the mass transport system in mammals called and what is it made up of?
The cardiovascular system which is made up of a series or vessels with the heart as a pump to move blood through the vessels. The blood is the transport medium
What are the 4 functions of the cardiovascular system?
- delivers the materials needed by the cells of the body and carries away the waste products of their metabolism
- carries hormones (chemical messages) from one part of the body to another
- forming part of the defence system of the body
- distributing heat
What are the three main categories that the function of blood falls into?
Transport, defence and the formation of tissue fluid and lymph
What 4 things does the plasma play a major role in transporting?
- digested food products from the small intestine to where they are needed either for storage or immediate use
- nutrient molecules from storage areas to the cells that need them
- excretory products from cells to the organs such as the lungs or kidneys that excrete them from the body
- hormones from where they are made to where they cause changes in the body
Apart from tranportation what else does the plasma do?
- Helps to maintain a steady body temperature by transferring heat around the system from deep seated organs or very active tissues
- acts as a buffer to pH changes
What is another name for red blood cells?
Erythrocytes
What do erythrocytes do and where are they formed?
They transport oxygen from the lungs to all the cells and they are formed in the bone marrow
How are erythrocytes well adapted to their function?
- they contain haemoglobin, a red pigment that carries oxygen and gives them colour. Each red blood cell has about 250-300 million molecules of haemoglobin that carry about 1000 million molecules of oxygen.
- haemoglobin also Carrie’s some of the carbon dioxide produced in respiration back to the lungs
- they have a bioconcave shape which means they have a large SA:V ratio so oxygen can diffuse in and out quickly
- they have no nucleus which leaves more space for the haemoglobin molecules
Leococytes are much larger than erythrocytes so how can they fit through blood vessels?
They change their shape
Where are leococytes formed?
In the bone marrow but some mature in the thymus gland
What is the main function of a leococyte?
To defend the body against infection
What are the physical properties of leococytes?
They all contain a nucleus and have a colourless cytoplasm although some types contain granules that can be stained
What are the differences between granulocytes and agranulocytes?
- both leococytes
- granulocytes have granules in the cytoplasm that take up stain and are obvious under the microscope. Agranulocytes do not
- granulocytes have lobed nuclei, agranulocytes do not.
List three types of granulocytes and what they do
• Neutrophils - part of the non specific immune system, they engulf and digest pathogens by phagocytosis. They have multi lobed nuclei
• Eosinophils -part of the non specific immune system. They are stained red by eosin stain. They are important in the non-specific immine responses against parasites, in allergic reactions and inflammation and in developing immunity to disease
• basophils - part of the non specific immune system. They have a two lobed nucleus
They produce histamines involved in inflammation and allergic reactions
What are two types of agranulocytes and what do they do?
- monocytes - part of the specific immune system. The largest leucocyte. They can move out of the blood into the tissues to form macrophages and they also engulf pathogens by phagocytosis
- lymphocytes- small leococytes with very large nuclei that are very important in the specific immune response of the body including making antibodies
What are platelets tint fragments of and where is this cell found?
Megakaryotes found in the bone marrow
What are platelets involved in?
The clotting of the blood
What are the physical properties of a molecule of haemoglobin?
Each one is a large globular protein made up of four peptide chains each with and iron containing prosthetic group which can pick up four molecules of oxygen in a reversible reaction to form oxyhaemoglobin
What does the first oxygen molecule that binds to the haemoglobin do?
Alters the arrangement of the molecule making it easier for the following oxygen molecules to bind and the final oxygen molecule bind several times faster than the first. The same process happens in reverse when oxygen dissociates from haemoglobin
How is a steep concentration gradient fainter from the air in the lungs to the red blood cells and why is this beneficial?
There is a low concentration of oxygen in the red blood cells when the blood enters the lungs. Oxygen moves into the red blood cells from the lungs by diffusion. Because true oxygen is picked up and bound to the haemoglobin the free oxygen concentration in the cytoplasm of the red blood cells remains low. This maintains a steep concentration gradient
This is beneficial because more and more oxygen diffuses in and is loaded onto the haemoglobin
Why does oxygen move out of the red blood cells into the body cells by diffusion?
Because there is a concentration gradient as the concentration of oxygen in the cytoplasm of the red blood cells is higher than the surrounding tissue
Due to the strong affinity of haemoglobin for oxygen what can a small change in the proportion of oxygen in the surrounding air do? And how does this show itself in the lungs and tissues?
A small change in the proportion of oxygen in the surrounding air can have a big effect of the saturation of oxygen in the blood.
In the lungs the haemoglobin loads up rapidly with oxygen
In the tissues as the oxygen saturation of the environment falls oxygen is released rapidly
How does carbon dioxide affect the way in which haemoglobin takes up and releases oxygen?
When the partial pressure of CO2 is high the affinity of haemoglobin for oxygen is reduced so haemoglobin needs higher levels of oxygen to become saturated and gives up oxygen much more easily
What is Bohrs effect and where can it be seen in the body?
The changes in the oxygen dissociation curve that result as rhe carbon dioxide level changes
It can be seen in:
• active tissues with high carbon dioxide levels where haemoglobin releases oxygen much more easily
• in the lungs with low carbon dioxide levels it is easier for the oxygen to bind to the haemoglobin
Where is fetal haemoglobin found?
In the developing fetus
How is fetal blood adapted to make if easier to remove oxygen from the maternal blood?
- it has a higher affinity for oxygen than the haemoglobin in the mothers blood
- the maternal and fetal blood run in opposite directions in the placenta so there is a counter current exchange system maximising the oxygen transfer to the blood of the fetus
What is myoglobin?
A respiratory pigment found in the muscle tissue of vertebrates. It is a small bright red protein which gives meat its strong colour
Describe the affinity of myoglobin
It has a higher affinity for oxygen that haemoglobin so becomes easily saturated with oxygen and this affinity is not affected by the partial pressure of oxygen in the tissues.
Why is myoglobin a good pigment to have in muscles?
- When it is bound to an oxygen molecule it does not give up oxygen easily and so acts as an oxygen store
- when the oxygen levels in very active muscles get really and carbon dioxide levels are correspondingly high then myoglobin releases it’s much needed store of oxygen
What happens when carbon dioxide is dissolved in the blood?
It reacts slowly with the water to form carbonic acid H2CO3 which separates to form the ions H+ and HC03-
In what ways is carbon dioxide transported in the blood?
- 5% is carried in solution in the plasma
- about 10-20% combined with the haemoglobin molecules to form carbaminohaemoglobin
- most of the carbon dioxide is transported in the cytoplasm of the red blood cells as hydrogen carbonate ions
What enzyme catalysed the formation of carbonic acid from water and carbon dioxide and what else does it do?
Carbonic anhydrase
It also catalysed the reverse reaction so that free carbon can diffuse out of the blood and into the lungs
How does haemoglobin avoid changing the pH of the blood?
It acts as a buffer accepting the hydrogen ions to form haemoglobnic acid
What is a chloride shift?
When hydrogencarbonate ions pass out of the red blood cells by diffusion and the chlorine ions move in.
What would be the result if your blood didn’t clot?
- if you lose too much blood you will die
* pathogens can get into the body through an open wound
What flows from a cut vessel?
Plasma, blood cells and platelets
What does contact between platelets and components of tissue cause?
The platelets to break open in large numbers
Platelets release several substances when they break open. Which two are particularly important and why?
☆ Serotonin causes the smooth muscle of the blood vessel to contract. This narrows the blood vessels cutting off the blood flow to the damaged area
☆ Thromboplastin is an enzyme that sets in progress a cascade of events that leads to the formation if a clot
Which vitamin is important in the clotting cascade and why?
Vitamin K is important in the production of many of the compounds in the blood clotting cascade including prothrombin
What are the four stages of the clotting cascade?
- thromboplastin catalyses the conversion of a large soluble protein called prothrombin found in the plasma into another soluble protein, the enzyme called thrombin. This happens on a large scale at the site of a wound. Calcium ions need to be present in the blood at the right concentration for this reaction to happen.
- thrombin acts on another soluble plasma protein called fibrinogen converting it to an insoluble substance called fibrin which forms a mesh of fibres to cover the wound.
- more platelets and blood cells pouring from the wound get trapped in the fibrin mesh. This forms a clot
- special proteins in the structure of the platelets contract making the clot tighter and tougher to form a scab which protects the skin and vessels underneath as they heal
What happens if the bodys clotting mechanism is triggered in the wrong place and give examples
It can lead to serious problems in the blood vessels.
A clog in the vessels that supply your heart with blood can cause a heart attack
A clot in the brain can cause a stroke
What do arteries do?
Carry blood away from the heart towards the cells of the body
Which arteries dont carry oxygenated blood?
- the pulmonary artery: carries deoxygenated blood from the heart to the lungs
- the umbilical artery: during pregnancy this carries deoxygenated blood from the fetus to the placenta
What is the structure of an artery?
- lumen is small when artery outstretched by flow of blood from heart. It has smooth lining to allow easiest possible flow of blood. Tunica Intima is the inner layer
- middle layers of the artery wall contain elastic fibres and smooth muscle; arteries nearest the heart have more elastic fibres those further away from the heart have a greater proportion of muscle tissue. Tunica Media
- external layer of tough tissue. Tunica Externa
What are peripheral arteries?
Arteries further from the heart
In which arteries is the blood pressure lower?
The peripheral arteries
What is an average heartbeat
About 70 times a minute
Why do arteries closer to the heart contain more elastic fibres?
So they can withstand the high pressure surges of blood from the heart
What is the pulse you feel?
The arteries contracting and expanding as blood moves through it
How is an organs activity regulated?
The muscle fibres in the vessel walls in the peripheral arteries contract or relax to change the size of the lumen, controlling the blood flow and so how much blood flows into the organ
What does the capillary network link?
The arterioles and venules
How do capillaries increase diffusion?
- they have thin walls consisting of only one cell. This allows them to branch between cells so substances can diffuse between the cells and the blood quickly
- the diameter of each individual capillary is small meaning the blood travels relitavely slowly through them so there is more opportunity for diffusion to occur
What’s the difference between the blood entering and exiting the capillary network?
Blood entering from the arteries is oxygenated. By the time it leaves it contains less oxygen and more carbon dioxide
What do veins do?
Carry deoxygenated blood towards the heart
Which veins dont carry deoxygenated blood?
- the pulmonary vein - carries oxygen rich blood from the lungs back to the heart for circulation around the body
- the umbilical vein - during pregnancy it Carrie’s oxygenated blood from the placenta into the fetus
What is the smallest branch of the arterial system called?
Arterioles
What leads from the capillary network and mergers into larger vessels leading back to the heart?
Venules
Describe the structure of a vein
- relatively large lumen with a smooth inner surface. Tunica intima
- relatively thin layer of smooth muscle with few elastic fibres. Tunica media
- outer tough layer consisting mainly of collagen fibres. Tunica externa/ adventitia
What are ultimately the two veins that carry the returning blood to the heart?
- the inferior vena cava from the lower parts of the body
* the superior vena from the upper parts of the body
Why is the blood pressure in veins low?
Because the pressure surges from the heart are eliminated as the blood passes through the capillary beds
What are the two main ways in which blood is returned to the heart through the veins?
- at frequent intervals throughout the venous system there are one way valves called semilunar valves. They are formed from infoldings of the inner wall. Blood can pass through the heart but if it starts to flow backwards the valves close preventing any backflow
- many of the larger veins are situated between large muscle blocks of body. When the muscles contract they squeeze these veins and this squeezing helps to return blood to the heart
What is the heart made up of?
Two muscular pumps joined together working in perfect synchrony
What are the two sides of the heart separated by?
A thick muscular septum
What do the right and left side of the heart do?
The right side receives blood from the body and pumps it to the lungs
The left side receives blood from the lungs and pumps it to the body
What is the muscle called that the heart is made up of?
The cardiac muscle
What is special about the cardiac muscle?
- it can carry on contracting regularly without resting or getting fatigued
- it has a good blood supply as the coronary arteries bring oxygenated blood to the tissue
- it contains a lot of myoglobin which stores oxygen for the respiration needed to keep the heart contracting regularly
Describe the 5 stages of blood moving through the heart
•the inferior and superior vena cave’s receive deoxygenated blood and deliver it to the right atrium
• as the right atrium fills with blood the pressure builds up and opens the tricuspid valve so the right ventricle starts to fill with blood too. When the atrium is full it contracts forcing blood into the ventricle. The atrium has thin muscular walls as it receives blood at low pressure. One way semilunar valves are at the entrance of the atrium to stop a backflow of blood
the triscupid valve (atrioventricular valve) is made up of three flaps and separates and atrium from a ventricle. It only lows blood to move from the atrium to ventricle
• the right ventricle is filled with blood under some pressure when the atrium contracts then the ventricle contracts. Its muscular walls produce the pressure needed to force blood out if the heart into the pulmonary arteries. This carries the deoxygenated blood to the capillary beds of the lungs. As the ventricle starts to contract the triscupid valves close to prevent blood backflow. Semilunar valves stop blood flowing from the artery back to the ventricle.
•the blood returns to the left side of the heart in the pulmonary veins. the blood is at quite low pressure. The blood returns to the left atrium which contracts to force blood into the left ventricle which is filled with blood under pressure. Backflow is prevented by the bicuspid valve
• the left ventricle pumps the blood out of the heart and into the aorta. This carries blood away from the heart at a very high pressure.
What makes sure that the valves are not turned inside out by the pressure exerted when the ventricles contract?
The tough tendinous cords/ valve tendons/ heart strings
What are the two atrioventricular valves called and which side of the heart are they both found in?
- tricuspid valve in the right side
* bicuspid valve in the left side
What are one way valves called?
Semilunar valves
What are one way valves called?
Semilunar valves
What does the septum do?
Prevents oxygenated and deoxygenated blood from mixing
What is the gap in the septum in the embryo called?
The foramen ovale
What is patent foramen ovule?
‘Hole in the heart’ where the foramen ovule goes not close over at birth
What do your heartbeat sounds come from and what noise is this described as?
They come from blood hitting the valves and the sound is described as ‘lub-dub’
Describe the lub dub sound
- the first sound comes as the blood is forced against the atrioventricular valves when the ventricles contract
- the second sound comes as a backflow of blood hits the semilunar valves in the pulmonary artery and aorta as the ventricles relax
What is the contraction of your heart called?
A systole
What can systole be divided into and what is the space of time between them.
- atrial systole where the atria contract forcing blood into the ventricles
- ventricular systole where the ventricles contract
Ventricular systole happens about 0.13 seconds after atrial systole
What is a diastole
The relaxation stage between contractions when the heart relaxes and is filled with blood
What is the cardiac cycle?
A single heartbeat which is made up of one cycle of systole and diastole and lasts about 0.8 seconds in humans
What does myogenic mean?
Originates from muscle tissue
What does the myogenic stimulation give rise to?
The intrinsic rhythmicity of the heart
What is the intrinsic rhythm maintained by?
A wave of electrical excitation similar to a nerve impulse that spreads through a special tissue in the heart muscle
What are the 7 stages of the multi step process that controls the heartbeat?
- the area of the heart with the fastest insintric rhythm is called the sinoatrial node (SAN) and this acts as the hearts own natural pacemaker
- the sinoatrial node sets up a wave of electrical excitation (depolarisation) that causes the atria to start contracting
- the annulus fibrosus is a region of non-conducting tissue between the atrium and the ventricle. This prevents the excitation from the atria from spreading directly to the ventricles
- the wave of excitation from the SAN spreads through the atria as the contract. It stimulates another region of conducting tissue between the atrium and ventricle called the atrioventricular node (AVN)
- The AVN is stimulated but produces a slight delay before it passes the wave of depolarisation into the bundle of His, a group of conducting fibres in the septum. This ensures that the atria have stopped contracting before the ventricles start.
- the bundle of His splits into two branches and carries the wave of excitation onto the Purkyne tissue
- the purkyne tissue consists of conducting fibres that penetrate down through the septum spreading around the ventricles. As the depolarisation travels through the tissue it sets off the contraction of the ventricles starting at the apex (bottom) and so squeezing blood out of the heart
What measures the electrical changes of the heart?
And electrocardiogram (ECG)
What are the procedures in order to carry out an ECG?
- 12 electrodes and leads are attached to your body
- your skin is wiped with alcohol to remove grease or sweat to make best contact with the electrodes
- sometimes a gel is applied to the electrodes ro make sure they conduct electricity as effectively as possible
How many different views come from an ECG and why this many?
12, as information is fed back from each electrode
How is an ECG carried out?
- with the patient lying down and resting
* with the patient exercising (stress test)
What is atherosclerosis?
‘Hardening of the arteries’
The build up of plaques on the inside of arteries
What is a plaque, what can it do and where is it likely to form?
It is a yellowish fatty deposit which can build up until it restricts the flow of blood through an artery or even block it completely and they are likely to form in the arteries of the heart and neck (coronary and carotid arteries)
What is the typical progression of the development of a plaque?
- a slight damage to the endothelial cells lining the arteries leads to a build up of lipids - the start of a plaque deposit
- blood platelets form a cap over the fatty plaque, which narrows the whole artery
- any further damage causes a clot to form and this can block the whole artery
What is the typical progression of the development of a plaque?
- a slight damage to the endothelial cells lining the arteries leads to a build up of lipids - the start of a plaque deposit
- blood platelets form a cap over the fatty plaque, which narrows the whole artery
- any further damage causes a clot to form and this can block the whole artery
Why does atherosclerosis usually occur in arteries rather than veins?
Because the blood in arteries flows fast under quite high pressure which puts more strain of the endothelium lining the vessels and can cause small areas of damage.
What is a plaque also known as?
An atheroma
What happens when the damage to the arteries has occured?
The bodys inflammatory response begins and white blood cells arrive at the site of the damage. These cells accumulate chemicals from the blood, particularly cholesterol. This leads to an atheroma. Fibrous tissue and calcium salts also build up around the atheroma turning it into a hardened plaque. This hardened area means that part of the artery wall hardens so it is less elastic than it should be
Why does atherosclerosis lead to increased blood pressure and what problems does increased blood pressure lead to?
- the lumen of the artery becomes smaller which leads to increased blood pressure
- increased blood pressure makes it harder for the heart to pump blood around the body
- the raised blood pressure makes damage more likely in other areas of the endothelial lining and more plaques will form. This will make the blood pressure even higher and so the problem gets worse
- high blood pressure damages the tiny blood vessels in your kidney and sometimes if the kidney tubules are narrowed they force out proteins through their walls
- it also damages the vessels supplying the retina of the eyes and if they get starved of oxygen if they are blocked you can become blind
What is an aneurysm?
A weaker bulging area of artery wall that results from a build up behind a blockage cause by plaques. The weakened artery wall may split open leading to massive internal bleeding
Where do aneurysms usually occur?
They frequently happen in the blood vessels supplying the brain or in the aorta
What are the two most common types of heart disease?
- angina
* myocardial infection (heart attack)
What happens in angina?
Plaques build up slowly in the coronary arteries reducing blood flow to the parts of the heart muscle beyond the plaques
When are the first symptoms of angina noticed and why?
During exercise when the cardiac muscle is working harder needing more oxygen the coronary arteries cannot supply enough oxygenated blood and the heart muscle resorts to anaerobic respiration.
What are the symptoms of angina?
- A gripping pain in the chest that can extend to the arms, particularly the left one and the jaw
- breathlessness
What can angina be helped by?
Taking regular exercise, losing weight and not smoking
How are the symptoms of angina treated?
• with drugs that cause rapid dilation of the coronary blood vessels so that they supply the cardiac muscle with the oxygen it needs
What is used to treat angina?
- a stent may be inserted
* heart bypass surgery may be carried out
What happens in a myocardial infection?
One of the branches of the coronary artery becomes completely blocked and part of the heart muscle is permanently starved of oxygen
What are many heart attacks caused by and why does this happen?
- a blood clot as a result of atherosclerosis
- the wall of an artery affected by a plaque is stiffened making it much more likely to suffer cracks or damage and platelets come into contact with the damaged surface of the plaque and the clotting cascade is triggered
What is a clot that forms in a blood vessel known as?
A thrombosis
What is a clot that gets stuck in a coronary artery known as?
Cornornary thrombosis
What happens if a clot blocks the coronary artery?
It starves the heart muscle beyond that point of oxygen and nutrients and this often leads to a heart attack
What are the symptoms of a heart attack?
There is severe pain in your chest and down your left arm
What is a stroke caused by?
An interruption to the normal blood supply to an area of the brain.
This may be due to bleeding from damaged capillaries or a blockage cutting off the blood supply to the brain caused by a blood clot, and atheroma or both
Sometimes the blood clot is formed somewhere else in the body and is carried in the bloodstream until it gets stuck in an artery in the brain
What are the symptoms of stroke and why do they vary?
- dizziness, confusion, slurred speech, blurred vision or loss of part of the vision (usually just in one eye), numbness and paralysis in severe strokes (usually down just one side of the body)
- they vary depending on how much of the brain is affected
What does risk describe?
The probability that a particular event will happen
Why is atherosclerosis a multifactorial disease?
Because many things influence your chances of being affected
What is a correlation
When there is a similarity in pattern between two things
What is causation?
When one thing is shown to have caused another
What are the three main risk factors for atherosclerosis which you cant control?
- Genes: there is a genetic tendency is some families and ethnic groups to develop atherosclerosis or other cardiovascular diseases
- age: as you get older your blood vessels begin to lose their elasticityc and to narrow slightly making you more likely to suffer from atherosclerosis and CVDs
- sex: under the age of 50 men are more likely to suffer from atherosclerosis as the female hormone oestrogen reduces the build up of plaque
What are the modifiable risk factors for atherosclerosis and why?
- smoking: chemicals in tobacco smoke can damage the artery linings making the build up of plaque more likely, cause the arteries to narrow, raising the blood pressure and increasing the risk of atherosclerosis
- exercise: regular exercise helps to lower blood pressure, prevent obesity and diabetes, lower blood cholesterol levels, balance lipoproteins and reduce stress
- weight: it is an indicator of risk because high blood pressure and type 2 diabetes increase the risk of damage to blood vessel linings and so of plaque formation and they are both a direct result of being overweight
- stress: stress causes the release of cytokines that trigger an inflammatory response in blood vessels leading to plaque formation and it tends to cause raised blood pressure
- diet: the balance of low density and high density lipoproteins is an indication of your risk of developing atherosclerosis and the associated CVDs
What is tissue fluid?
A fluid that is Plasma without the plasma proteins and red blood cells that moves out of the capillaries and bathes the individual cells of the body
Why is tissue fluid important?
Because substances diffuse into the cells from the tissue fluid and waste products diffuse out into the tissue fluid
What are the two factors involved in making sure 90% of tissue fluid is back in the blood vessels by the time the blood leaves the capillary bed and how does this work?
- water potential: the plasma proteins exert an osmotic effect giving blood a constant and fairly low water potential of -3.3kPa. The tissue fluid has a water potential of about -1.3kPa. Water moves from an area of high water potential to an area of low water potential so the tendency is for water to move into the blood by osmosis. The pressure behind this movement is about -2kPa and is called the oncotic pressure
- hydrostatic pressure: the residual pressure from the heartbeat that is still present as the blood enters the arterial end of the capillary beds which tends to force fluid out through the leaky capillary walls
What happens at the arterial end of the capillaries?
The hydrostatic pressure is quite high at about 3.3kPa whereas the oncotic pressure is about -2.0kPa. The hydrostatic pressure is higher so the tissue fluid is squeezed out ot the capillary and fills the spaces around all the cells
Why does the hydrostatic pressure tall to around 1.0kPa at the venous end of the capillaries?
- the pressure from the pulse is completely lost
* fluid moves out of the capillaries to form tissue fluid so the volume of blood in the capillaries is lowered
What happens at the venous end of the capillaries?
The oncotic pressure is higher than the hydrostatic pressure so most of the tissue fluid moves back into the capillaries by osmosis
What is lymph and where is it found?
The remaining 10% of the tissue fluid that does not return to the capillaries and it drains into blind ended tubes called lymph capillaries
In what way are lymph vessels similar to veins?
- they have one way valves to prevent the lymph from flowing backwards
- lymph is moved through the vessels by the contraction of the body muscles
How is lymph returned to the neck area?
It joins the left and right subclavian veins found under the collar bone
Where are lymph glands found?
At intervals along the lymph vessels
What happens at the lymph glands?
- this is where the lymphocytes accumulate and produce antibodies to fight disease
- the lymph glands remove bacteria and other pathogens to be taken in and destroyed by phagocytes
How do the antibodies get into the blood?
They are emptied into the blood with the lymph at the subclavian glands
What are albumins?
A group of small proteins involved in the transport of other substances
