transport systems Flashcards
(23 cards)
Common features of transport systems:
they are made up of tubes or ‘vessels’ that carry materials from one part of the organism to another
they make close contact with cells, such as those of exchange surfaces
What substances are transported in the blood?
Substance transported : From : To
Oxygen The lungs All the body’s cells
Carbon dioxide All the body’s cells Lungs
Glucose Digestive system The liver, then all the body’s cells
Urea Liver cells Kidneys
Oxygen is carried in
Red blood cells
. Dissolved substances are carried in the
plasma
The heart has four chambers
two
atria
and two
ventricles
Humans have a double circulatory system. The heart pumps blood through two circuits:
the
pulmonary circulation
the
systemic circulation
The pulmonary circulation transports blood to the lungs. At the lungs:
oxygen
diffuses
into the blood from the
alveoli
- the blood becomes oxygenated
carbon dioxide
diffuses from the blood into the lungs
Arteries
Always carry blood away from the heart
Carry oxygenated blood, except for the pulmonary artery
Carry blood under high pressure
Have thick muscular and elastic walls to pump and accommodate blood
A type of supporting tissue called connective tissue provides strength
The channel in the blood vessel that carries blood - the lumen - is narrow
Veins
Always carry blood to the heart
Always carry deoxygenated blood, except for the pulmonary vein
Carry blood under low or negative pressure
Have thin walls - have less muscular tissue than arteries
Have less connective tissue than arteries
Have a wide lumen
Capillaries FEATURES
The walls of capillaries are just one cell thick. Capillaries therefore allow the exchange of molecules between the blood and the body’s cells - molecules can
diffuse
across their walls.
Types of blood cell and cell fragments:
red blood cells
white blood cells
platelets
function of all
Plasma Transporting carbon dioxide, digested food molecules, urea and hormones; distributing heat
Red blood cells Transporting oxygen
White blood cells Ingesting pathogens and producing antibodies
Platelets Involved in blood clotting
Red blood cells advantages
They have no
nucleus
- they lose it during their development - so they can pack in more haemoglobin.
They are small and flexible so that they can fit through narrow blood capillaries.
They have a biconcave shape - they are the shape of a disc that is curved inwards on both sides - to maximise their surface area for oxygen absorption.
They are thin, so there is only a short distance for the oxygen to diffuse to reach the centre of the cell.
Phagocytes
About 70 per cent of white blood cells are
phagocytes
. Phagocytes engulf and destroy unwanted microorganisms that enter the blood, by the process of
phagocytosis
. They are part of the body’s
immune system
.
Lymphocytes
Lymphocytes make up about 25 per cent of white blood cells. They are also part of the body’s immune system. Lymphocytes produce soluble proteins called
antibodies
when a foreign body such as a microorganism enters the body.
Platelets
Platelets are cell fragments produced by giant cells in the
bone marrow
.
Platelets stop bleeding in two main ways:
they have
proteins
on their surface that enable them to stick to breaks in a blood vessel and clump together
they secrete proteins that result in a series of chemical reactions that make blood clot, which plugs a wound.
Coronary heart disease
The coronary arteries may become blocked by a build-up of fatty material, caused by certain kinds of ‘bad’
cholesterol
. As the fatty material increases, one or more coronary arteries narrow, and can become blocked.
If a blockage builds up, the amount of oxygen reaching the heart muscle is reduced. A person will develop chest pain, and if left untreated, a heart attack is the result.
Ways of treating cardiovascular disease
Statins drugs that help to lower cholesterol in the blood. They do this by lowering its production in the
liver
.
Some studies have raised concerns regarding the side effects of statin use, while others believe they can bring additional positive benefits.
Statins are not suitable for everyone - they should not be prescribed for people with liver disease, or pregnant or breast feeding women.
Some patients taking statins often experience side-effects such as headaches and memory loss. There have been reports of statins being linked with type 2
diabetes
and liver damage.
Other people argue that statins should be used more widely. They may protect against other conditions such as
Alzheimer’s disease
, but further research is needed.
Another way
Stents
Coronary arteries that are blocked or have become narrow can be stretched open and a
stent
inserted to restore and maintain blood flow.
They can be used in instances where drugs are less effective, and offer a longer term solution. Stents are made from metal
alloys
and do not lead to an immune response in the patient.
Around 75 000 operations are carried out each year. Risk factors depend on the patient’s:
age
general health
whether they have had a heart attack
Heart transplants
A heart transplant is required in cases of
heart failure
.
Coronary heart disease can lead to heart failure.
A consultant assesses the patient’s condition. If other treatments are not managing the heart condition, a transplant may be recommended and a patient will be put on a waiting list
After the transplant, the patient will:
need time to heal, recover and build up strength
have to take drugs called
immunosuppressant drugs
for the rest of their life - this prevents the person’s immune system from rejecting the donor heart
have an increased risk of infection because of these drugs
Evaluating the treatment methods Advantages
Drugs - statins:
Reduce the risk of heart attack. Studies have shown a decrease in ‘bad cholesterol’ and an increase on ‘good cholesterol.’ Used to reduce high cholesterol levels that have genetic causes. May have beneficial effects on other conditions.
Heart Transplant:
Improve quality of life.
Replacement heart valves:
Restore blood flow through the heart
Stents:
Widen coronary arteries that have not responded to drug treatment. The recovery time is short following insertion of the stent.
Disadvantges
Not suitable for people with liver disease. Some side effects. Must be taken for life. Should not be taken if pregnant or breastfeeding - Statins
Few donor hearts are available. Recovery time is long. There is a risk of rejection by the body's immune system.- Heart Transplant
Biological valves may wear out. Blood clots may stick to mechanical valves - anti-blood clotting drugs need to be taken. = Replacement valves
In a minority of cases, further treatment is required. = Stents
Calculation blood flow
Cardiac output in cm3 per minute = heart rate in beats per minute × stroke volume in cm3 per beat.
An athlete is exercising. If their maximum heart rate is 130 beats per minute, and stroke volume is 150 cm3, what is their cardiac output in dm3?
19.5 dm3
Calculation:
Cardiac output in cm3 per minute = heart rate in beats per minute × stroke volume in cm3 per beat.
Cardiac output in cm3 per minute = 130 × 150 = 19 500 cm3 per minute = 19.5 dm3 per minute.
