Human Circulatory system
12. Human Body - Circulatory system
Circulatory system
Blood is the circulatory fluid of circulatory system. A healthy person has around 4-5 litres of blood. It is slightly alkaline in nature. It is composed of plasma and three types of corpuscles. Plasma is yellow coloured fluid consisting of water (92%), proteins(6-9%) and 1% minerals. Plasma transports red and white blood cells and platelets throughout the body. It also delivers nutrients to cells and picks up cell waste products.
Features of blood cells: Red blood cells, white blood cells, and platelets grow from a single precursor cell, known as a haematopoietic stem cell.
RBC (erythrocates)
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WBC(leucocyts)
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Platelets (thrombocytes)
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5 million (per cu mm of blood)
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5 to 9 thousand
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300,000
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life span 110-120 days
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life span of < 2 weeks
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life span of few hours
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devoid of nuclei
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contains one nucleus
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enucleated
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discs in concave shape
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irregular shaped cells
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spherical bodies
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formed in bone marrow
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red bone marrow
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formed in bone marrow
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destroyed by spleen
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destroyed by spleen
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destroyed by spleen
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consists of haemoglobin which transports oxygen
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provides immunity to the body
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important role in blood cloting
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Blood clotting
It is internal mechanisms of animals to prevent blood loss at the time of injury. During the blood clotting, the blood platelets produce an enzyme called thromokinase which forms prothrombin protein in the plasma. It combines with calcium ion to form thrombin. It convert the soluble plasma protein(fibrinogen) to form fibrin threads. corpuscles get entangled in these threads and forms clot.
Blood groups
The colour of human blood is red. However it does not mean that anyone can receive blood from others without agglutination. The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the red blood cells and the antibodies are in the blood plasma. based on this, four blood groups are identified. They are denoted by the letter A,B, AB, O (null). There are two type of antigen A and B and two types of anti bodies anti A and Anti B.
The colour of human blood is red. However it does not mean that anyone can receive blood from others without agglutination. The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the red blood cells and the antibodies are in the blood plasma. based on this, four blood groups are identified. They are denoted by the letter A,B, AB, O (null). There are two type of antigen A and B and two types of anti bodies anti A and Anti B.
Blood Group
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Antigens
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Antibodies
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Can give blood to
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Can receive blood from
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AB
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A and B
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None
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AB
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AB, A, B, O
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A
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A
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B
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A and AB
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A and O
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B
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B
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A
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B and AB
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B and O
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O
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None
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A and B
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AB, A, B, O
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O
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Blood transfusion
The general rule for blood transfusion is the donors red cells must be compatible with recipients plasma. Anti A plasma agglutinates A red cells, and anti B plasma agglutinates B red cells. People with O blood group can give blood to any group because they do not contain A and B anti bodies. So they are called universal donors. People with AB blood group are called universal recipients because they can accept blood from any group. So they are known as universal receipients.
The general rule for blood transfusion is the donors red cells must be compatible with recipients plasma. Anti A plasma agglutinates A red cells, and anti B plasma agglutinates B red cells. People with O blood group can give blood to any group because they do not contain A and B anti bodies. So they are called universal donors. People with AB blood group are called universal recipients because they can accept blood from any group. So they are known as universal receipients.
Rhesus (Rh) factor
About 85% of people also have a so called Rh factor on the red blood cells surface. This is also an antigen and those who have it are called Rh+. Those who have not are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. The antibodies stay for life. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems. This problem becomes dangerous the blood of mother is Rh + and she conceives a fetus that has inherited the Rh-positive factor from its father, the antibodies in her blood during her pregnancy pass through the placenta into the fetus and attack the fetus blood. This antibody will not harm her first child but if she conceives again, the antibody destroys the red cell of the embryo. This is known as erythroblastosis. If not treated, the fetus suffers severe anemia, which leads to brain retardation or death. Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.
About 85% of people also have a so called Rh factor on the red blood cells surface. This is also an antigen and those who have it are called Rh+. Those who have not are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. The antibodies stay for life. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems. This problem becomes dangerous the blood of mother is Rh + and she conceives a fetus that has inherited the Rh-positive factor from its father, the antibodies in her blood during her pregnancy pass through the placenta into the fetus and attack the fetus blood. This antibody will not harm her first child but if she conceives again, the antibody destroys the red cell of the embryo. This is known as erythroblastosis. If not treated, the fetus suffers severe anemia, which leads to brain retardation or death. Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.
Lymph
It is a yellowish fluid carried in the lymphatic system. Lymph is like blood but it contains white blood cells especially lymphocytes and red blood cells are absent. It acts as a medium for the exchange of material between cells and blood. It fights against germs.
It is a yellowish fluid carried in the lymphatic system. Lymph is like blood but it contains white blood cells especially lymphocytes and red blood cells are absent. It acts as a medium for the exchange of material between cells and blood. It fights against germs.
The human heart
The heart is a fist-sized, muscular organ that pumps blood through the body. Oxygen-poor blood enters the right atrium of the heart (via veins called the inferior vena cava and the superior vena cava). The blood is then pumped into the right ventricle and then through the pulmonary artery to the lungs, where the blood is enriched with oxygen (and loses carbon dioxide). The oxygen-rich (oxygenated) blood is then carried back to the left atrium of the heart via the pulmonary vein. The blood is then pumped to the left ventricle, then the blood is pumped through the aorta and to the rest of the body. This cycle is then repeated. Every day, the heart pumps about 7,600 liters of blood, beating about 100,000 times.
left atrium
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Upper left chamber of the heart; It receives oxygen-rich blood from the lungs via the pulmonary vein.
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right atrium
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The right upper chamber of the heart. It receives oxygen-poor blood from the body through the inferior vena cava and the superior vena cava.
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left ventricle
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The left lower chamber of the heart. It pumps the blood into the aorta (biggest and longest artery in human body). The left ventricle is much thicker than the right because it must pump blood around the entire body; this involves exerting a considerable force to overcome the pressure caused by the body.
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right ventricle
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The right lower chamber of the heart. It pumps the blood into the pulmonary artery.
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Heart valves & muscle
Heart contains valves which prevents mixing of blood in the four chambers.
Heart contains valves which prevents mixing of blood in the four chambers.
- septum - the muscular wall that separates the left and right sides of the heart.
- pulmonary valve - the flaps between the right ventricle and the pulmonary artery. When the ventricle contracts, the valve opens, causing blood to rush into the pulmonary artery. When the ventricle relaxes, the valves close, preventing the back-flow of blood from the pulmonary artery to the right atrium.
- mitral valve - the valve between the left atrium and the left ventricle. It prevents the back-flow of blood from the ventricle to the atrium.
- tricuspid valve - the flaps between the right atrium and the right ventricle. It is composed of three leaf-like parts and prevents the back-flow of blood from the ventricle to the atrium.
The wall of the heart is very muscular and does not tire. It consists of three distinct layers. The first is the outer epicardium which is composed of a layer of flattened epithelial cells and connective tissue. Beneath this is a much thicker myocardium made up of cardiac muscle. The endocardium is a further layer of flattened epithelial cells and connective tissue.
A large blood supply is necessary to power the heart itself. It is supplied by the left and right coronary arteries, which branch off from the aorta.
Regulation of the cardiac cycle
Cardiac muscle is myogenic, which means that it is self-exciting. This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The hearts rhythmic contractions occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influences such as exercise or the perception of danger.
The rhythmic sequence of contractions is coordinated by the sinoatrial node and atrioventricular nodes. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation that initiates the atria to contract. Once the wave reaches the atrioventricular node, situated in the wall between ventricular chambers, it is conducted through the bundles of His and causes contraction of the ventricles. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden.
The blood pressure for youg adult is 120 (systolic) and 80 (diastolic) mm of Hg. The Pulse is the throbing of arteries due to sudden detension of their walls after the ventricular systole. It it 72 in adult male and faster in women and children.
Cardiac muscle is myogenic, which means that it is self-exciting. This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The hearts rhythmic contractions occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influences such as exercise or the perception of danger.
The rhythmic sequence of contractions is coordinated by the sinoatrial node and atrioventricular nodes. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation that initiates the atria to contract. Once the wave reaches the atrioventricular node, situated in the wall between ventricular chambers, it is conducted through the bundles of His and causes contraction of the ventricles. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden.
The blood pressure for youg adult is 120 (systolic) and 80 (diastolic) mm of Hg. The Pulse is the throbing of arteries due to sudden detension of their walls after the ventricular systole. It it 72 in adult male and faster in women and children.
The cardiac cycle
Every beat of the heart involves a sequence of events called the cardiac cycle. This consists of three major stages: the atrial systole, the ventricular systole, and the complete cardiac diastole. The atrial systole consists of the contraction of the atria and the corresponding influx of blood in to the ventricles. Once the blood has fully left the atria, the atrioventricular valves, which are situated between the atria and ventricular chambers, close. This prevents any backflow into the atria. It is the sound of the valves closing which produces the familiar beating sounds of the heart.
The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood has left, the pulmonary and aortic semilunar valves close. Finally complete cardiac diastole involves the relaxation of the atria and ventricles in preparation for new blood to enter the heart.
Every beat of the heart involves a sequence of events called the cardiac cycle. This consists of three major stages: the atrial systole, the ventricular systole, and the complete cardiac diastole. The atrial systole consists of the contraction of the atria and the corresponding influx of blood in to the ventricles. Once the blood has fully left the atria, the atrioventricular valves, which are situated between the atria and ventricular chambers, close. This prevents any backflow into the atria. It is the sound of the valves closing which produces the familiar beating sounds of the heart.
The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood has left, the pulmonary and aortic semilunar valves close. Finally complete cardiac diastole involves the relaxation of the atria and ventricles in preparation for new blood to enter the heart.
Diseases and treatments
The study of diseases of the heart is known as cardiology. Important diseases of the heart include:
The study of diseases of the heart is known as cardiology. Important diseases of the heart include:
- Coronary heart disease is the lack of oxygen supply to the heart muscle; it can cause severe pain and discomfort known as Angina.
- A heart attack occurs when heart muscle cells die because blood circulation to a part of the heart is interrupted.
- Congestive heart failure is the gradual loss of pumping power of the heart.
- Endocarditis and myocarditis are inflammations of the heart.
- Cardiac arrhythmia is an irregularity in the heartbeat. It is sometimes treated by implanting an artificial pacemaker.
Other important points If a coronary artery is blocked or narrowed, the problem spot can be bypassed with coronary artery bypass surgery or it can be widened with angioplasty.
Beta blockers are drugs that lower the heart rate and blood pressure and reduce the hearts oxygen requirements. Nitroglycerin and other compounds that give off nitric oxide are used to treat heart disease as they cause the dilation of coronary vessels.
At Groote Schuur Hospital in Cape Town, South Africa, 53-year-old Lewis Washkansky on December 3, 1967 became the first human to receive a heart transplant (however he died 18 days later from double pneumonia). The transplant team was headed by Christiaan Barnard.
Beta blockers are drugs that lower the heart rate and blood pressure and reduce the hearts oxygen requirements. Nitroglycerin and other compounds that give off nitric oxide are used to treat heart disease as they cause the dilation of coronary vessels.
At Groote Schuur Hospital in Cape Town, South Africa, 53-year-old Lewis Washkansky on December 3, 1967 became the first human to receive a heart transplant (however he died 18 days later from double pneumonia). The transplant team was headed by Christiaan Barnard.
The hearts of other animals
The structure of the heart of other mammals is quite similar to that of humans, with four chambers. Birds also have a four-chambered heart, however it is thought that this evolved independently of that of mammals. Amphibians have a three-chambered heart. Fish have a single circulation system and a heart with two chambers. The hearts of arthropods and mollusks have a single chamber. The earthworm has a series of multiple primitive hearts.
The structure of the heart of other mammals is quite similar to that of humans, with four chambers. Birds also have a four-chambered heart, however it is thought that this evolved independently of that of mammals. Amphibians have a three-chambered heart. Fish have a single circulation system and a heart with two chambers. The hearts of arthropods and mollusks have a single chamber. The earthworm has a series of multiple primitive hearts.
Heartbeat
Smaller animals have faster heartbeat. This is evident within a species as well, as the young beat their hearts faster than the adults. Gray Whale beats 9 times per minute, Harbour Seal 10 when diving, 140 when on land, elephant 25, human 70, sparrow 500, shrew 600, and hummingbird 1,200 when hovering.
Smaller animals have faster heartbeat. This is evident within a species as well, as the young beat their hearts faster than the adults. Gray Whale beats 9 times per minute, Harbour Seal 10 when diving, 140 when on land, elephant 25, human 70, sparrow 500, shrew 600, and hummingbird 1,200 when hovering.
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