9webs.mn.catholic.edu.au/science/wilko//mt93/notes/mtn… · web view9.3.4.i perform an...

Senior Science

9.3 Medical Technology – Bionics

Section 4

Life SupportSystems

9.3 Medical Technology – Bionics ::: Section 4

9.3.4 Life support systems can be used to sustain life during operations or while the body repairs itself

9.3.4.a Describe the structures of the respiratory system and identify their function including– trachea– bronchi– alveoli– capillary network around the alveoli

9.3.4.b Explain why cardio-pulmonary resuscitation techniques can maintain life when the heart has ceased beating

9.3.4.c Identify that artificial lungs remove carbon dioxide from the blood and replace it with oxygen

9.3.4.d Discuss the type of operations that would require the use of an artificial lung

9.3.4.e Identify the devices that constitute life support systems in any major hospital

9.3.4.i Perform an investigation to model the action of the diaphragm in inhalation and exhalation

9.3.4.ii Perform a first-hand investigation to identify carbon dioxide in inhaled air and in exhaled air and determine which has the greater concentration

9.3.4.iii Gather, process and present information from secondary sources to identify monitoring and other devices that constitute life support systems and use available evidence to explain their roles in maintaining life


The role of the respiratory system

All of the cells in our body require a supply of oxygen. This is used in cells to turn food into energy allowing the body to move, grow and reproduce.

The word respiration defines two processes –

Internal or cellular respiration – glucose or some other small molecule (broken down by digestion) is oxidised to produce energy (and carbon dioxide)

External respiration (breathing) involves the intake of air (oxygen) and the removal of carbon dioxide from the lungs (gas exchenge).

The most important role of the respiratory system is to exchange gases. Blood removes oxygen from the lungs and releases carbon dioxide to the lungs. Humans would not be able to survive without this exchange of gases.

9.3.4.a Describe the structures of the respiratory system and identify their function including

– trachea– bronchi– alveoli– capillary network around the alveoli

The structures of the respiratory system and their function

The respiratory tract begins at: the nose and mouth, then the trachea, which divides into the right and left bronchi, then into smaller bronchi and bronchioles eventually ending in alveoli. Surrounding the alveoli is a capillary network

To be suitable for acceptance by the lungs, the outside air must – Be warmed to body temperature regardless of air temperature Be saturated with water vapour regardless of the humidity Be free of dust and debris, when it reaches the alveoli Be free of micro-organisms, which may cause problems if they enter the bloodThese functions and others must be completed as air travels down the various structures of the respiratory system

The conducting passages consist of muscle and/or cartilage and are lined with mucus. They conduct 10,000 litres of air daily. The air is heated as it passes through these passages. The incoming air picks up moisture from the mucus. In addition the mucus traps the


foreign matter that enters with the air. Small hair like projections called cilia line all the passages of the respiratory system. Their function is to move the mucus and the foreign matter it contains to the mouth. This helps protect the respiratory system. In the mouth the mucus and foreign material is swallowed and then sterilised in the stomach.

The cilia within the air passages beat at 1000 to 1500 times per minute. This moves the mucus at 0.5 to 1 mm/minute in the small airways and, up to 5 to 20 mm/minute, in the trachea and main bronchi. All foreign material collected in the lungs is normally removed within 24 hours. Ciliated cells may suffer damage from agents such as cigarette smoke. This damage can lead to a lack of function and an increased rate of infection.

Nose – The function of the nasal passages is to act as moisteners (mucus), filters (mucus and nose hairs) and warms (blood in capillaries) the air

Pharynx and Larynx – throat area; sounds made in the larynx; epiglottis prevents food and drink from entering lungs

Trachea – a tube fitted with rings of cartilage, which prevent it from collapsing under low pressure. It contains mucus and cilia to moisten, filter and warm the air. Air from the trachea enters two smaller tubes called bronchi. These are not the same size. The left lung is smaller than the right lung to accommodate the heart (the heart is situated slightly to the left side of the chest).

Bronchi – two smaller tubes with rings of cartilage also containing mucus and cilia. Each bronchus delivers air to one of the lungs. Air from each bronchus passes into paired branches of unequal length and diameter. The greater airflow in the larger diameter branches means that the air reaches all parts of the lungs at approximately the same time and the amount of air is uniform. The number of alveoli at the end of that branch controls the diameter.

Bronchioles – smaller and smaller tubes with thinner and thinner walls; have no cartilage below a certain diameter. The smallest bronchioles lead to alveolar sacs. Each sac contains about 20 tiny air spaces called alveoli.

Alveoli are small sacs at the ends of bronchioles. The function of these sacs is to provide the place where gaseous exchange occurs.


Gaseous exchange relies on simple diffusion. To do this effectively the sacs have the following structure: A large surface area. The surface area of

the 300,000,000 alveoli sacs is large, approximately 140 square metres.

A very short diffusion path between the oxygen and the blood. The air and blood are separated by 1/1000th of a millimetre.

An appropriate concentration gradient for oxygen and carbon dioxide, between air and blood needs to be maintained. The processes of breathing and circulation, maintains the desired concentration gradients.

Some particles do not get caught in the mucus and end up in the alveloi. Special cells, called alveolar macrophages absorb the particles and then destroy them or carry them to the mucus. They are the main defence mechanism for the lungs.

The capillary network is a network of very small capillaries in the walls of each alveolus. Its function is to collect oxygen and release carbon dioxide. The network structure exists to maximise the gas exchange that occurs in the alveoli. A thin layer of tissue separates the air and the blood. The exchange of gases takes in only 0.25 second as oxygen enters the circulatory system and carbon dioxide leaves it. A red blood cell takes three times as long to pass through the capillary. The entire blood supply (about 5 litres) passes through the lungs each minute.

Questions

1. Define or describe the terms [7 marks]diffusion, exchange, filter, mucus, network, sterilised, tract

2. Name the structures of the respiratory system that contain mucus. [1 mark]

3. Name the structures of the respiratory system that contain cilia. [1 mark]

4. Name the structures mentioned that help protect the respiratory system. [1 mark]

5. Describe the structures of the respiratory system and identify their function including the trachea, bronchi, alveoli and capillary network around the alveoli. Put the information into a table similar to the one below. [12 marks][NB Describe means to identify features &/or characteristics]

Structure Description of structure Identify function of structure


9.3.4.b Explain why cardio-pulmonary resuscitation techniques can maintain life when the heart has ceased beating

CPR – Cardio-Pulmonary Resuscitation

A person whose heart has stopped beating can be kept alive by rescuers who provide: artificial ventilation of the lungs (mouth to mouth breathing – external air resuscitation) and artificial circulation of blood (external cardiac compression). Together this procedure is known as cardio-pulmonary resuscitation, or CPR.

It is called CPR because it involves the cardiac muscle and pulmonary circulation. The heart is made up of special muscle tissue called cardiac muscle. Pulmonary circulation involves blood flow from the heart to the lungs via the pulmonary artery. This blood is deficient in oxygen. As well, it involves blood flow from the lungs to the heart via the pulmonary vein. This blood is rich in oxygen since oxygen is absorbed at the lungs.

In CPR mouth to mouth breathing provides a supply of oxygen that can be absorbed by blood in the lungs. The fresh air we breathe in contains 21% oxygen; the lungs absorb 5% of this oxygen, and so the air we breathe out contains 16% oxygen. That is, mouth-to-mouth resuscitation is effective in providing oxygen to the lungs because there is enough oxygen (16%) in the air that is breathed out. This oxygen is absorbed by circulating blood and therefore life can be maintained.

Diagrams Diagrams

External cardiac compression (a rhythmic compression of the chest) is designed to squeeze the heart between the sternum and backbone. This causes blood to be pumped out of the heart. External cardiac compression is effective because it will provide enough movement of blood to sustain life and prevent the brain damage, when combined with mouth to mouth. This is provided the blood is collecting oxygen as it passes through the lungs.

People who experience a heart attack have about a 1 in 20 chance of survival but if CPR is performed until medical help arrives, the chances improve to 1 in 4. CPR is also applicable in cases of drowning, electrocution, suffocation and drug overdose. The use of CPR may also be therapeutic for those who witness any of these occurrences. They may feel helpless unless they become involved in helping.


9.3.4.c Identify that artificial lungs remove carbon dioxide and replace it with oxygen

9.3.4.d Discuss the type of operations that would require the use of an artificial lung

Artificial Lungs

Artificial lungs remove carbon dioxide from the blood and replace it with oxygen.

The chief role of the lungs is to supply oxygen to, and remove carbon dioxide from, the circulatory system. Operations where either of these two functions is affected would require the use of an artificial lung.

The first external artificial lung – the iron lung – was developed in 1928. This device is used to treat patients whose muscles and organs of breathing have been paralysed. The iron lung saved many lives in the 1950’s, when polio epidemics caused respiratory paralysis. The iron lung helped people to breathe by reducing the pressure in the device, which surrounded the patient. This restricted the patient’s ability to move.

Today other kinds of respiratory machines are used. Positive pressure ventilators, which forced air into the lungs were developed in the 1950’s. Most of these units needed an artificial airway and required a great deal of effort on the patient’s part. A tube placed through a surgical incision in the throat created the artificial airway. Modern ventilators provide gaseous interchange through a nose or face-mask and require very little effort on the patient’s part. Most are computer controlled to mimic the patient’s breathing more efficiently.

Lung replacement in humans is possible but there are not enough donors. Also complications can occur because the transplant may be rejected. The IMO (Intravenous Membrane Oxygenator) is a device that performs the same function as the natural lungs. Absorption of oxygen and removal of carbon dioxide occurs but it operates differently to natural lungs. The IMO is intended for patients with pneumonia, chronic lung disease and organ transplant operations.

The IMO is fitted within the vena cava (see diagram opposite). It consists of hundreds of hollow fibre membranes and an inflating-deflating balloon (see diagram below). The balloon improves oxygen absorption and carbon dioxide removal but can cause damage to the blood and clotting.


Artificial lungs are widely used as the lung part of the heart-lung machines needed during open-heart surgery. This is a short time application, for the length of an operation. More work is being done to increase this time, up to a number of weeks, so that sufferers of acute but reversible respiratory distress may be helped and ultimately for years as a permanent transplant.

The device is shown below, as is its positioning in the body. The IMO is placed before the lungs, so that blood can be oxygenated as much as possible and then any addition from the lungs will be of extra benefit.

What to do

Read and answer the following questionDiscuss the type of operations that would require the use of an artificial lung

The question provides no structure, yet it requires an extended answer. In order to answer the question a plan needs to be developed. The steps below show one way of developing a plan.

Step 1 Underline and recall meanings of the important words in the questionType of operations, Artificial lung

Step 2 Circle the KEY (Board of Studies) verb in the question and recall the meaning of the verb(s). Discuss – identify issues; provide points for and against.

Step 3 Make a list of issues that could be used to answer the questionProvide points for and against some of these issues[NB this step may require some research]

Identify the function of an artificial lung Identify the type of operations that would require an artificial lung Explain how the artificial lung is useful on ONE operation

Step 4 Write an answer.


9.3.4.e Identify the devices that constitute life support systems in any major hospital

Life support systems

Without the support of many devices people would die. Such devices constitute life support systems. These include: Heart rate monitors Artificial lungs Artificial heart Kidney dialysis machines

9.3.4.iii Gather, process and present information from secondary sources to identify monitoring and other devices that constitute life support systems and use available evidence to explain their roles in maintaining life

Life Support Systems

There are a large number of monitoring and other devices that constitute life support systems. One such device is the kidney dialysis machine.

The kidneys are complex organs that have a number of important functions. The most important function is the production of urine. This liquid removes a number of wastes from the body. If these wastes are not removed from the body poisons build up in the body, and death can result.

If the kidneys do not function adequately, people can be kept alive by a kidney dialysis machine. A dialysis machine filters blood by removing excess fluid and wastes such as urea, that is it supports or replaces kidney function. Tube connects the machine to an artery in the patients arm. Blood flows into the machine where the blood is filtered. Another tube carries blood back into a vein in the arm. This is a life support device because if the wastes were not removed toxins would build up in the body and the patient would eventually die.

Research

Choose one life support system. Explain the role of this life support system in maintaining life.


9.3.4.i Perform an investigation to model the action of the diaphragm in inhalation and exhalation

Introduction

A very simplified operation of the lungs can be viewed using the equipment below. While the movement of the ribs cannot be shown and the filling of the balloons is marginal, the process is adequately mimicked.

Air enters the lungs when the chest cavity is expanded. To do this, the ribs are pulled outward and the diaphragm contracts and moves downward. This reduces the pressure of gases in the lungs. Since the air pressure outside is higher than the air pressure inside the lungs, air is forced in.

Air is exhaled when the muscles relax and the diaphragm moves up to its original position. The reduction in the volume of the chest, coupled with the increased amount of air in the lungs, results in a larger pressure inside the lungs than outside the lungs. Air is exhaled.

What to do

1. Stretch the bottom ‘elastic’ section downwards.2. Observe what happens to the ‘balloon lungs’3. Identify the part of the balloon lungs that acts as the diaphragm. [1 mark]4. Outline the role of the diaphragm in real lungs. [2 marks]5. Complete the table below. [5 marks]6. Copy and then label the parts of the ‘balloon lungs’ as indicated. [3 marks]7. Outline the parts of the respiratory system not modelled by the balloon lungs. [3 marks]

Model lung Real LungInhalation Inhalation Rubber diaphragm stretched down Ribs pulled out; diaphragm pulled down Volume of container INCREASES Air pressure decreases [Air moves from areas of high to low pressure] Air flows into balloons and they expand

Exhalation Exhalation


9.3.4.ii Perform a first-hand investigation to identify carbon dioxide in inhaled air and in exhaled air and determine which has the greater concentration

CO2 in inhaled and exhaled air

Introduction

The following equipment can be used to find a qualitative measure of the relative amount of carbon dioxide gas in air, which is inhaled, compared to that which is exhaled. By breathing slowly into the mouthpiece inhaled air will pass through the limewater solution in flask 1 and into the subject. As the subject breathes out, exhaled air will pass through the limewater solution in flask 2. The limewater undergoes a chemical reaction with carbon dioxide to produce insoluble calcium carbonate, which gives a milky appearance to the solution. The greater the amount of carbon dioxide the more precipitate produced and the ‘whiter’ the solution.

calcium oxide + carbon dioxide calcium carbonate

What to do

1. Set up the equipment drawn below and perform the experiment.


Write a laboratory report of this investigation using the lab report scaffold.H13 13.1a Select and use appropriate text types for written presentations

a. Write a heading for the investigation

b. Write an aim for the investigation.

c. Make a list of equipment needed.

d. List possible risks and other safety factorsH11 11.3b Carry out a risk assessment of the intended investigation

H12 12.1d Identify and use safe working practices during investigations

e. Write a method for the investigation.Be sure that in your instructions it is clear that: one variable (independent) is being deliberately changed by the experimenter. it is expected that only one other variable will change (dependent) some variables need to be controlled for all groups there is a control group there is an experimental group the instructions are logical and repeatable the experiment is repeated enough to obtain reliable results

f. Write down what you observe in the results section. Draw a labelled diagram.H13 13.1e Use pictorial representations to present information clearly and succinctly

g. Write a conclusion.H14 14.1a Analyse results to identify trends

2. Complete the discussion questions.

Discussion

1. Name the independent variable.2. Name the dependent variable.

H11 11.2a demonstrate use of the terms independent and dependent to describe variables

3. Identify variables that need to be kept constant.4. Identify the control in this experiment5. Discuss why a control is necessary.

H11 11.2b identify variables that need to be kept constant; demonstrate use of a control

6. Describe how the dependent variable is measured in this investigation.

7. Explain why the method described is appropriate.H11 11.2d Describe procedures to undertake investigations & explain why a procedure is appropriate

8. How many times should this experiment be repeated for the results to be reliable?

9. Identify one reason why this experiment is repeatable.

10. Identify a design fault in this experiment that could lead to an invalid conclusion.11.Evaluate the validity of the data collected in this investigation.

H12 12.4d Evaluate the validity of first-hand data in relation to the area of investigation


9webs.mn.catholic.edu.au/science/wilko//mt93/notes/mtn… · web view9.3.4.i perform an...

Documents