Blood Groups and Blood Transfusion
Grouping of human blood is done
using the ABO system and the Rhesus factor.
The ABO system
The ABO system of grouping blood
depends on two things. First is the presence or absence of antigen A or antigen
B on the membranes of the red blood cells. Second is the presence of antibody
A or antibody B in the blood plasma.
A person cannot have a certain
antigen membrane of the red blood cell and also have the corresponding antibody
in the plasma. For example, you cannot have both antigen A antibody a. This
would cause agglutination clumping together of red blood cell. Agglutination
can cause fatal
The various blood groups and the
antigens a antibodies present in them are summarized
Blood group
|
Antigen on the membrane of the
blood cell
|
Antibody in the plasma
|
A
|
A
|
A
|
B
|
B
|
B
|
AB
|
A and B
|
(none)
|
O
|
(none)
|
a and b
|
Rhesus factor
This factor is named after the
Rhesus monkey in which it was first observed. When the rhesus factor is present
on the red blood cell membrane, a person is said to be rhesus positive. This is
abbreviated as Rh+. If it is absent, the person is rhesus negative this is
abbreviated as Rh-. Thus, a person’s blood is said to be A+ if it is blood
group A and has the Rhesus factor or A- if it is blood group A but lacks the
Rhesus factor. There is also B+ or B-, O+ or 0- and AB+ or AB- blood groups.
If a rhesus negative woman marries a
rhesus positive man, their children are highly likely to be rhesus positive.
During the last months of pregnancy, the rhesus antigen from the foetus passes
into the mother's blood. This causes the mother's body
to produce antibodies which destroy some of
the foetus's red blood cells. This destruction is minimal in the first child
but in the children that follow, a lot of destruction could take place, killing
the foetus. This is called haemolytic disease of the
newborn or erythroblastosis foetalis. To prevent this,
the mother is treated with anti-rhesus globulin. This prevents her body from
forming antibodies against the rhesus antigen.
Blood transfusion
Blood transfusion is the transfer of
blood from one person (the donor) to another (the recipient). It is necessary
to replace blood when the recipient has a blood disorder or has lost a lot of
blood due to surgery or an accident.
Blood
transfusion
In order for blood transfusion to be
successful, the blood of the donor and that of the recipient must mix without
agglutination. When this happens, the blood is said to be compatible. If the
blood is incompatible, agglutination occurs.
Blood compatibility depends on the
blood groups of the donor and the recipient. For example, if a person of blood
group A receives blood from a person of blood group B, the recipients’ body
produces antibodies against antigen B. This is because the antigen is seen as
foreign material.
Individuals with blood group AB are
called universal recipients. They can receive blood from people of any blood
group. However, they can only donate blood to someone with blood group AB.
Those with blood group O are universal donors. They can donate blood to people
of all blood groups. On the other hand, they can only receive blood from
someone with blood group O.
The following is a compatibility
table for the different blood groups.
Compatibility of blood groups
Donor's blood group Recipient's blood group
A
|
B
|
AB
|
O
|
|
A
|
√
|
×
|
√
|
×
|
B
|
×
|
√
|
√
|
×
|
AB
|
×
|
×
|
√
|
×
|
O
|
√
|
√
|
√
|
√
|
Key:
v - Means compatible
X - Means incompatible.
If blood from a rhesus positive
person is transfused to a rhesus negative person, the recipient produces rhesus
antibodies. If such a transfusion is done a second time, massive agglutination
can occur. This can lead to loss of life.
Precautions taken during transfusion
- Blood from the donor must be checked for compatibility
with blood from the recipient in terms of both ABO blood group and Rhesus
factor in order to avoid agglutination.
- The donor's blood must be screened to ensure that it
does not have pathogens that can cause diseases such as HIV and AIDS,
syphilis and hepatitis B.
- Donated blood is stored in special bags and an
anticoagulant is added to prevent it from coagulating.
- Donated blood is kept in a refrigerator for a maximum
of 21 days. After that it expires and should not be used.
- Transfusion should be done only when extremely
necessary.
Advantages of blood transfusion
- It ensures rapid replacement of blood lost from the
body, for example during surgery or due to an accident.
- Blood transfusion is used to treat diseases such as
sickle-cell anaemia
Disadvantages of blood transfusion
- There are no exact blood matches. Blood is a complex
tissue that contains many different. One person's blood cannot be exactly
the same as another's. Hence, there are chances of developing a reaction
to transfused blood.
- Transfused blood may not always be 100% free of
infections.
Blood circulation in human being
Blood circulation is the movement of
blood from the heart to all part of the body and back to the heart. Human being
exhibit double circulation where by the blood passes through the heart
twice for each complete circulation
Double
circulation in human being
In other less complex
organisms like the fish, blood goes through the heart only once; this is known
as single circulation.
Pulmonary circulation
- During pulmonary circulation, deoxygenated blood is
brought to the heart through the vena cava. This blood is emptied into the
right auricle. The right auricle pumps blood to the right ventricle. When
the right ventricle contracts, it pumps blood to the lungs through the
pulmonary artery.
- In the lungs, the blood is oxygenated. It then flows
back to the heart through the pulmonary vein. The movement of blood
between the heart and the lungs is called the pulmonary cycle.
Systemic circulation
- In systemic circulation, the pulmonary vein transports
blood to the left auricle. The left auricle then pumps the blood into the
left ventricle. The left ventricle has strong muscles that pump blood to
all parts of the body through the aorta.
-
- After the tissues have derived their requirements from
the blood, it flows back to the heart through the vena cava. This movement
of blood between the heart and the various parts of the body is called the
systemic cycle.
Formation of tissue fluid
The aorta is the largest artery in
the body. It braches into smaller arteries, which in turn branch into even smaller
vessels called arterioles. Arterioles branch into capillaries which are in
contact with the tissue of the body. The capillaries have tiny pores that allow
some components of blood to filter into the tissues.
At the arterial end of the
capillary, there is high blood pressure. This forces fluid out through the any
pores in the capillaries
The fluid is composed of water,
oxygen, hormones and nutrients. This fluid bathes the cells. It is called
tissue fluid or interstitial fluid.
The substances in this fluid diffuse
into the cells through the cell membrane. In addition, the waste products from
the cells diffuse into the tissue fluid. These wastes include carbon dioxide,
minerals, heat and nitrogenous wastes.
Formation of tissue fluid
At the venous end of the capillary,
blood pressure is low; water potential is also low. The pressure of the tissue
fluid is higher. This forces the tissue fluid back into the capillaries.
Diffusion also helps in the re-entry of tissue fluid to the capillary. However,
some tissue fluid remains within the cells. This later enters the lymphatic
system to form lymph.
The capillaries join to form
venules. Venules join to form veins. The veins transport blood back to the
heart. Veins in the lower part of the body unite to form the inferior vena cava
while veins in the upper part of the body unite to form the superior vena cava.
These two large veins join to form the vena cava which transports blood to the
right auricle of the heart.
Importance of blood circulation
- It enables the transportation of cell requirements such
as oxygen and nutrients to all the body tissues.
- It ensures that waste products from the cells are
removed in order to prevent accumulation. Accumulation of waste products
is harmful to the body.
- Blood circulation is important for the regulation of
body temperature. Body heat is transported to all parts of the body
through this system.
- Blood circulation also transports hormones from the
organs that produce them to the organs where they are needed. For example,
insulin from the pancreas is a hormone necessary for the regulation of
blood sugar levels
Blood pressure
Blood pressure is measured by
considering the systolic pressure and the diastolic pressure.
Systole occurs when the ventricles contract and pump blood into the
arteries.
Diastole is the phase when the auricles contract to pump blood into
the ventricles.
The pressure developed during these
actions can be felt in the arteries. It is measured in millimeters of mercury
(mmHg).
For example, if the pressure during
systole is 120 mmHg and the pressure during diastole is 80 mmHg, the blood
pressure is 120/80 mmHg. This is the average blood pressure in a normal human
being. A sphygmomanometer is the instrument used to measure blood
pressure.
Diseases and disorders of the human
circulatory system
The diseases and disorders of the
human circulatory system are increased by eating habits and lifestyles. Eating
food with high levels of cholesterol and fat causes narrowing of blood vessels
due to deposition in blood vessels. Lifestyles such as smoking, lack of
exercise, stress and taking alcohol also put one in danger of developing heart
problems such as coronary heart disease and high blood pressure.
Arteriosclerosis
Arteriosclerosis is the hardening of
arteries. It happens when there are fat deposits on the wall of the artery or
when fibrous tissues form in the artery wall or artery walls degenerate;
Arteriosclerosis hinders the
arteries from pulsating normally. The lumen is narrowed, affecting the
efficiency of blood flow
As a result, the heart has to pump
harder in order to supply the tissues with enough blood. The result of this is
high blood pressure (hypertension). High blood pressure usually has no specific
symptoms. However, it can cause headaches, dizziness and ringing in the ears.
Causes of arteriosclerosis
Arteriosclerosis is mainly caused by
excessive alcohol and smoking, stress, too much fat in the jet, lack of
exercise or old age,
Effects of arteriosclerosis
Arteriosclerosis causes swelling of
part of a blood vessel and rupturing of the artery walls. It also causes total
blockage of an artery, thus depriving some tissues of oxygen. This can cause
the affected tissue to become severely damaged or to die.
Prevention and treatment of
arteriosclerosis
People can prevent themselves from
arteriosclerosis by avoiding alcohol and smoking, reducing stress, minimizing
intake of fatty foods and engaging in regular exercise. Arteriosclerosis can be
treated by medication or surgery.
Sickle-cell anaemia
This condition is a genetic disorder
which causes production of abnormal haemoglobin and malformed red blood cells.
The effect is a reduction of the blood's capacity to transport oxygen. The
disease gets its name from the crescent or sickle shape of the red blood cells.
Signs and symptoms of sickle-cell
anaemia
Sickle-cell anaemia is characterized
by fatique or excessive tiredness, shortness of breath during exercise,
headaches, dark-coloured urine, abdominal pain, abnormal heartbeat and general
body weakness.
Treatment and prevention of
sickle-cell anaemia
Sickle-cell anaemia has no cure. It
is difficult to prevent since it is inherited. However, patients can be helped
by making sure that they avoid excessive physical exercise and eat a
well-balanced diet that is rich in minerals and vitamins.
Leukemia
Leukemia is a type of blood cancer.
It is caused by the over production of white blood cells and the suppressed
production of red blood cells
The excess white blood cells
infiltrate body organs, for example the liver and the spleen. This causes
reduced efficiency in the functioning of these organs and their abnormal
enlargement.
Signs and symptoms of leukemia
Leukemia is characterized by
abnormally high numbers of white blood cells, abnormal bleeding, e.g. nose
bleeding, bleeding even from minor cuts, extreme body weakness, anaemia, and
throat and mouth infections that may be recurrent.
Treatment of leukemia
Leukaemia cannot be cured. However,
it is controlled by frequent blood transfusions, radiotherapy and chemotherapy
to kill the abnormal cells, and bone marrow transplants
High blood pressure (Hypertension)
The blood pressure of a normal human
being is 120/80 mmHg. Very high blood pressure (over 140/90)
strains the blood vessels and causes hypertension and sometimes heart failure.
Increase in blood pressure may be caused by high fat levels due to
over-consumption of fatty foods, lack of exercise, obesity, high emotional
stress, alcoholism and smoking, and arteriosclerosis.
Signs and symptoms of hypertension
The signs and symptoms of
hypertension include feeling dizzy, ringing sound in the ear and severe
headaches.
Prevention and treatment of
hypertension
Hypertension can be prevented by
engaging in regular exercises, avoiding alcohol and smoking, eating a balanced
diet with less fat to control weight and reducing stress as much as possible.
Hypertension can be treated using drugs.
Coronary thrombosis
Coronary thrombosis occurs when
there are blood clots in the blood vessels that supply blood to the heart
(coronary arteries). This prevents blood from reaching some tissues of the
heart. The affected tissues lack adequate amounts of oxygen and waste materials
accumulate in the cells to toxic levels.
Symptoms of coronary thrombosis
Coronary thrombosis is characterized
by uncomfortable pressure or sharp pain in the chest, sometimes extending to
the neck, shoulders and arms, excessive sweating, dizziness or fainting, nausea
or a feeling of severe indigestion and shortness of breath.
Effects of coronary thrombosis
Coronary thrombosis can cause death
of some cardiac tissue or sudden death.
Prevention and treatment of coronary
thrombosis
People can avoid coronary thrombosis
by doing regular exercise, avoiding sudden strenuous activity, avoiding alcohol
and smoking, minimize intake of fatty foods and avoiding excessive stress
Thrombosis can be treated by drugs.
Stroke
A stroke occurs when there is
interference in the amount of blood flowing to the brain. Such interference can
be due to blockage or rupture of an artery supplying blood to the brain. This
causes some brain cells to lack adequate oxygen and nutrients.
Symptoms of stroke
Symptoms of a stroke include sudden
numbness or weakness especially on one side of the body, sudden confusion or
trouble in understanding or speaking and sudden poor vision in one 01 both
eyes. The patient also experiences sudden dizziness, loss of balance, trouble
when walking 01 lack of coordination, and sudden severe headaches
Effects of a stroke
A stroke has severe effects on the
victim such as weakness or paralysis on one side of the body, leading to
difficulties in movement and coordination. It also causes lack of feeling on
one side of the body, speech or language problem; and loss of memory. Other
effects are behaviour changes, difficulty when swallowing and exhaustion.
Prevention and treatment of a stroke
A stroke can be avoided by avoiding
drinking and smoking, ensuring your blood pressure remains it the normal range
and exercising regularly. Eating a low-fat, low-salt diet can also prevent a
stroke Medication can help in the treatment of a stroke.
The Lymphatic system
The lymphatic system closely
resembles the blood circulatory system. It consists of lymph, lymph vessels
through which lymph travels, and lymphoid organs and tissues such as thymus,
adenoids, tonsils, lymph nodes and spleen.
Lymphatic system connects with the
blood circulatory system at the superior vena cava
After cells get their requirements
from tissue fluid, not all the fluid flows back into the capillaries, Part of
it flows into lymph vessels. Once in these vessels, the fluid is called lymph.
Lymph is a pale yellow fluid. It has the same components as tissue fluid, but
more fatty substances.
Lymph vessels unite to form larger
vessels called lymph ducts. There are two main lymphatic ducts; the
right lymphatic duct empties into the right subclavian vein while the
left lymphatic duct drains into the left subclavian vein. The two
veins join to form the superior vena cava. In this way, the contents of lymph
enter the blood circulation system
Formation of lymph
Lymphatic ducts form nodule-like
structures called lymph nodes. These nodes are found in the abdomen,
groin, armpits and neck. Lymph nodes are important sites for the production of
white blood cells. They also filter out foreign materials such as bacteria and
dead tissue before they enter the bloodstream.
The flow of lymph depends greatly on
the squeezing of lymph vessels by breathing movements, intestinal movements and
muscular movements. The lymph vessels have valves to prevent back flow of
lymph.
Importance of the lymphatic system
- Lymph nodes produce lymphocytes (white blood cells)
which help the body to fight diseases.
- Lacteals enable absorption of fatty acids after
digestion.
3.
It provides a way of getting tissue fluid back to the circulatory system.
4. The
spleen destroys worn out red blood cells.
5. The
spleen, the adenoids and the tonsils produce antibodies which help in
fighting disease-causing microorganisms
Disorders and diseases of the
lymphatic system
There are many diseases and
disorders that affect the lymphatic system. Some of these diseases and
disorders are explained below.
Elephantiasis
This is a disease that is caused by
worms (filaria) that block the lymph vessels causing accumulation of lymph
which leads to swelling of the arms or legs
Filaria worms are transmitted by
mosquitoes. Elephantiasis is treated by destroying the parasites. One way of
preventing it is by eliminating breeding areas of mosquitoes, for instance
bushes and stagnant water.
Oedema
This is the swelling of body tissues
due to excessive lymph. It is caused by increased blood pressure in the
capillaries, causing the production of large amounts of lymph that the
lymphatic system cannot transport efficiently, pregnancy, obesity and protein
deficiency.
Oedema can be controlled by taking
measures to reduce blood pressure, pregnant women keeping the feet slightly
raised when sitting or lying down eating a well-balanced diet and taking
measures to reduce body weight, for example by exercising and avoiding eating
excessive amounts of food.
Lymphoma
Lymphoma is the term used to refer
to cancers that affect the lymphatic system. These cancers cause abnormal
growth or functioning of the components of the lymphatic system. The result is
weakened immune response in the body.
Symptoms of lymphoma include swollen
and painful lymph nodes, fatigue, weight loss, night sweats and itching.
Lymphomas are treated using
chemotherapy and radiation therapy. Severe cases may call for bone marrow
transplants
Tonsillitis
This is an infection and swelling of
the tonsils. It is caused by bacteria or viruses that enter the body through
the mouth or sinuses.
Symptoms include red and swollen
tonsils, sore throat, fever or chills, muscle ache and tiredness.
Mild cases of tonsillitis are
treated by having adequate rest and taking plenty of fluids. More severe cases
may require medical treatment; frequent tonsillitis is sometimes solved by
tonsillectomy (surgical removal of the tonsils).
Summary:
- The mammalian heart is responsible for pumping blood to
all parts of the body. It has four chambers: two auricles (or atria) and
two ventricles.
- Valves in the heart and veins prevent the back flow of
blood.
- The flow of blood in the heart is as follows
(a) Deoxygenated blood from the body
enters the right auricle through the vena cava
(b) The right auricle pumps blood to
the right ventricle.
(c) The right ventricle pumps blood
to the lungs through the pulmonary artery.
(d) Oxygenated blood from the lungs
enters the left auricle through the pulmonary vein.
(e) The left auricle pumps blood to
the left ventricle.
(f) The left ventricle pumps blood
to all parts of the body through the aorta.
4.The main blood vessels are
arteries, veins and capillaries.
5. Arteries are muscular vessels
that transport blood away from the heart. Arteries contract and relax, creating
a pulse.
6. Veins are less muscular than arteries. They transport blood
towards the heart.
7. Capillaries are very small
vessels whose walls are one cell thick. They are in direct contact with the
body tissues.
8. Blood is a fluid tissue consisting of plasma, red blood cells, white blood cells and platelets
9. Plasma is the fluid part of blood. It transports dissolved substances, helps to regulate body temperature and pH and acts as a site for the exchange of nutrients and waste products.
8. Blood is a fluid tissue consisting of plasma, red blood cells, white blood cells and platelets
9. Plasma is the fluid part of blood. It transports dissolved substances, helps to regulate body temperature and pH and acts as a site for the exchange of nutrients and waste products.
10. Red blood cells are biconcave in
shape, lack a nucleus and contain haemoglobin. Their function is to transport
oxygen and carbon dioxide.
11. White blood cells are
irregularly shaped. They are important for immunity.
12. Platelets are fragments of
cells. They help in blood clotting.
13. Grouping of human blood is done
according to the ABO system and the Rhesus factor.
14. Blood transfusion is the transfer of blood from a donor to a recipient.
15. Agglutination occurs if transfused blood is incompatible with the recipient’s blood.
16. Blood circulation is the movement of bloodfrom the heart to all parts of the body. Blood circulation in humans involves a double circulation system where there are two cycles:
- Pulmonary cycle (from the heart to the lungs and back).
- Systemic cycle (from the heart to all parts of the body and back)
17. Diseases and disorders of the human circulatory system include high blood pressure, arteriosclerosis, sickle-cell anaemia and leukaemia.
18. Blood pressure is measured by considering the pressure when the ventricles contract (systole) and the pressure when the auricles contract (diastole).
19. Lymph is formed from tissue fluid that does not flow back into the capillaries.
20. Disorders of the lymphatic system include oedema, lymphoma, tonsillitis and elephantiasis.
14. Blood transfusion is the transfer of blood from a donor to a recipient.
15. Agglutination occurs if transfused blood is incompatible with the recipient’s blood.
16. Blood circulation is the movement of bloodfrom the heart to all parts of the body. Blood circulation in humans involves a double circulation system where there are two cycles:
- Pulmonary cycle (from the heart to the lungs and back).
- Systemic cycle (from the heart to all parts of the body and back)
17. Diseases and disorders of the human circulatory system include high blood pressure, arteriosclerosis, sickle-cell anaemia and leukaemia.
18. Blood pressure is measured by considering the pressure when the ventricles contract (systole) and the pressure when the auricles contract (diastole).
19. Lymph is formed from tissue fluid that does not flow back into the capillaries.
20. Disorders of the lymphatic system include oedema, lymphoma, tonsillitis and elephantiasis.
0 Comments