Blood and circulation

Blood and circulation
Blood is the fluid tissue or medium in which all materials are transported to and from individual cells in
the body.
Component of blood
Red blood cell (RBC)
blood cell
Blood disorders (will study in chapter 12 but relevant here too)
Sickle-cell anemia
 Sickle cell disease is an inherited blood disorder involving haemoglobin. Affected RBCs are stiff rather
than flexible; as they try to squeeze into narrow blood vessels, they can’t fold over like a normal RBC.
 Instead, their shape becomes distorted: the cells elongate and the ends point, making them look
somewhat like a sickle (grass cutting tool).
 These distorted cells are also sticky, causing them to clump together and block small blood vessels.
This deprives tissues of necessary oxygen, resulting in intense pain.
 Other complications of sickle cell disease include kidney or heart failure or stroke.
 Results from a deficiency of one of the clotting factors.
 Haemophilia is a sex-linked recessive disorder, it affects primarily males.
 People with hemophilia may be deficient in any one of several different clotting factors, but the most
common missing factor is factor VIII.
 Because people with hemophilia lack the ability to form blood clots, even minor injuries can become
life threatening. The disorder is treated with infusions of the missing clotting factor.
The structure and function of the circulatory system
 Humans have a double circulatory system. Blood is pumped from the heart to the site of gas
exchange (the lungs) then comes back to the heart before being pumped to the rest of the body.
 Blood vessels
Arteries (branches into
Carry blood away from heart.
Arteries have thick muscular and elastic walls to withstand pressure.
Veins (formed by connecting
Carry blood towards the heart.
Veins have valves at intervals to prevent the back flow of blood.
Unite arterioles and venules, forming a network in the tissues.
The wall of a capillary vessel is only a single layer of cells thick which
allows the process of diffusion of dissolved substances to and from the
tissues to occur.
The heart
heart beat is initiated
Heart rate
Number of heart beats per minute,
The average heart beats in an adult is between 60 and 80 beats per minute.
Factors affecting the heart beats rate include:
● exercise
● heat
● strong emotions such as grief, fear, anger or excitement (under the influence of adrenaline).
Regulation of heart rate
The heart generates and maintains its own beat. However, the nervous system— even though it doesn’t
initiate the heartbeat— can alter the heart’s rhythm and force of contractions. Specifically, the medulla
in the brain detects changes in the body and sends messages to raise or lower heart rate.
Tissue fluid
 Liquid part of blood than seeps out of capillaries when substances are exchanged.
 Different from plasma as the proteins are absent (enzymes, hormones, antibodies etc).
Lymphatic system
The tissue fluid, that is not reabsorbed by the capillaries, drain into the lymph vessels. The liquid, now
known as lymph, is filtered of micro-organisms, cell debris or harmful substances at lymph nodes before
reentering the blood stream.
Q2 What is a heart rate?
Q3 Cell fragments of blood involve in the clotting of the blood
Q4 Fill in the blanks
Transfer of blood from donor to recipient is called …...................………
Antigen are present on ………………………, and antibodies in the ……………………...
People from blood group O can receive blood from blood group /groups………………………
The clear colourless liquid flowing out of the blood capillary walls is called …..……………….
1) The blood cell designed to protect the body against infection is:
a leucocyte
b erythrocyte
c platelet
d thrombocyte
2) The blood vessel that carries deoxygenated blood from the heart to the lungs is the:
a pulmonary vein
b pulmonary artery
c aorta
d inferior vena cava
3) The bicuspid valve of the heart is found between the:
a left atrium and left ventricle
b right atrium and right ventricle
c pulmonary artery and right ventricle
d left ventricle and aorta
4) Which of the following is a unique part of the structure of a vein?
a thick muscular wall
b valves
c thick elastic wall
d single cell layer thick
5) The condition presenting with constricting pain in the left side of the chest radiating to the left arm is:
a anaemia
b angina
c stroke
d aneurysm
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