Biof4c10 PDF: Types of Circulatory Systems

## Types of Circulatory System ### The necessity for transport systems in complex multicellular organisms * Each living cell requires essential substances like oxygen and nutrients, and expels cellular waste products such as carbon dioxide and nitrogenous wastes. * In Chapter 2, you learned how un...

## Types of Circulatory System ### The necessity for transport systems in complex multicellular organisms * Each living cell requires essential substances like oxygen and nutrients, and expels cellular waste products such as carbon dioxide and nitrogenous wastes. * In Chapter 2, you learned how unicellular organisms like Amoeba sp. get their essentials and expel wastes by diffusion from and to its external surroundings. * Unicellular organisms have a small body mass. Therefore, the total surface area to volume ratio (TSA/V) of the organism is large. * As such, Amoeba sp. does not require a specialized transport system to transport substances in and out of the cell. * Large complex multicellular organisms cannot obtain essential substances and expel wastes by diffusion because their TSA/V is small. * The distance between the external environment and the cell is too far for direct substance exchange. ### Types of circulatory systems in multicellular organisms The circulatory system in multicellular organisms is divided into two types: open circulatory system and closed circulatory system. #### Open Circulatory System * In an open circulatory system, haemolymph flows directly into the body cavity (haemocoel) and bathes the cells. * Haemolymph is a blood-like nutritious liquid found in most invertebrates such as insects and molluscs. #### Closed Circulatory System * In a closed circulatory system, blood is always contained in a continuous closed blood vessel and is distributed to the whole body. * The exchange of substances that are essential to cells such as oxygen and nutrients occurs across the walls of blood capillaries. ### Open Circulatory System #### Circulatory System of Insects * The circulatory system of insects is an open circulatory system. This means that one or more hearts pump haemolymph through the blood vessels into the haemocoel. * Haemolymph flows out from the heart into the haemocoel when the heart contracts. * In the haemocoel, substance exchange between haemolymph and body cells occurs through diffusion. * When the heart relaxes, haemolymph flows back into the heart through tiny openings called ostium. #### Circulatory System of Fish * The heart of the fish has two chambers, that is, an atrium (plural: atria) and a ventricle. * Blood that leaves the ventricle is pumped to the gill capillaries to enable gaseous exchange. * The gill capillaries carry blood to the blood vessels that transport oxygenated blood to systemic capillaries. * In the systemic capillaries, oxygen diffuses into the tissues while carbon dioxide diffuses from the tissue into the capillaries. * The deoxygenated blood is then returned to the heart atrium through the veins. * As the blood flows in one direction, the fish circulatory system is known as a single circulatory system. ### Closed Circulatory System #### Circulatory System of Amphibians * The heart of an amphibian has three chambers, that is, two atria and a ventricle. * Unlike the single circulatory system of fish, blood flows in two directions: pulmocutaneous circulation and systemic circulation. Therefore, this system is known as a double circulatory system. * Amphibians are said to have an incomplete double circulatory system because the deoxygenated blood and the oxygenated blood are mixed. * Pulmocutaneous circulation transports blood to the lungs and skin, and the exchange of gases takes place here. * Systemic circulation transports oxygenated blood to the body tissues and returns the deoxygenated blood to the right atrium through the veins. #### Circulatory System of Humans * The human heart consists of four chambers: two atria and two ventricles that are separated completely. * Humans have a double circulatory system. This means that in one complete circulatory cycle, blood flows in the blood vessels through the heart twice. As there are two different circulations, humans are said to have a complete double circulatory system because the deoxygenated blood and the oxygenated blood do not mix. ##### Pulmonary circulation * Deoxygenated blood is transported through the pulmonary artery to the lungs for gaseous exchange. * Oxygenated blood from the lungs is returned to the left atrium and flows into the left ventricle. ##### Systemic circulation * Blood is pumped from the heart to all the body tissues through the aorta. Then the deoxygenated blood returns to the right atrium through vena cava. #### Table 10.1: Similarities and differences between circulatory systems in complex multicellular organisms | Similarity | |---|---| | The circulatory system is found in all multicellular organisms. | | The circulatory system consists of a heart to pump blood or haemolymph (in insects). | | The circulatory system functions to transport nutrients and wastes. | | The heart has valves that ensure blood flows in one direction. | | Organism | Types of circulatory system | Number of circulations | Number of heart cavities | Separation of oxygenated blood and deoxygenated blood | |---|---|---|---|---| | Insects | Open blood circulatory system | - | The heart is made up of many cavity segments | - | | Fish | Closed blood circulatory system | Single | Two (one atrium and one ventricle) | - | | Amphibians | Closed blood circulatory system | Double | Three (two atria and one ventricle) | Incomplete (some oxygenated blood is mixed with the deoxygenated blood in the ventricle) | | Humans | Closed blood circulatory system | Double | Four (two atria and two ventricles) | Complete (oxygenated blood does not mix with deoxygenated blood in the ventricle) | ## Circulatory System of Humans * There are three main components in the circulatory system of humans: * **Blood:** A type of connective tissue that is made up of blood plasma, blood cells and platelets. Blood acts as a medium of transportation. * **Heart:** Functions as a muscular pump that circulates blood to the whole body. * **Blood vessels:** Consist of arteries, capillaries and veins that are connected to the heart, and transport blood to all the body tissues. ### Structure of the heart * The heart is located between the lungs in the thorax cavity and contains four chambers: * Left atrium * Right atrium * Left ventricle * Right ventricle * The left chamber is separated from the right chamber by a muscular wall called septum. * Atrium receives blood that returns to the heart while the ventricle pumps blood out of the heart. The ventricle has thicker walls and contract stronger than the atrium. * The muscular wall of the left ventricle is much thicker than the muscular wall of the right ventricle. This is because the left ventricle has to generate greater pressure to pump blood out of the aorta to the whole body while the right ventricle only has to pump blood to the lungs. #### Coronary arteries * Transport oxygenated blood for heart tissues. #### Coronary veins * Transport deoxygenated blood. #### Aorta * The main blood artery that transports oxygenated blood to the whole body. #### Vena cava * The main vein that transports deoxygenated blood back to the heart. #### Semilunar valves * At the base of the pulmonary artery and the base of the aorta. * Ensure that blood which flows out of the heart does not flow back into the ventricle when the ventricle relaxes. #### Tricuspid valve * Located between the right atrium and the right ventricle. * Ensures that blood which flows into the right ventricle does not flow back into the right atrium. * This valve consists of three leaflets. #### Bicuspid valve * Located between the left atrium and the left ventricle. * Ensures that blood which flows into the left ventricle does not flow back into the left atrium. This valve consists of two leaflets. #### Septum * Separates the left part of the heart from the right part of the heart and ensures that the oxygenated blood does not mix with the deoxygenated blood. #### Pulmonary artery * Transports deoxygenated blood from the heart to the lungs. #### Pulmonary veins * Transports oxygenated blood from the lungs to the heart. ### Composition of human blood * The human blood consists of **55% plasma** and **45% cell components**. * **Plasma** is the medium of transportation in the body. * **Blood cells** consist of: * **Red blood cells or erythrocytes:** Transport oxygen * **Platelets** Involved in blood clotting * **White blood cells or leucocytes** Protect from pathogens ### Blood plasma components and main function | Component | Main function | |---|---| | Water | Blood plasma consists of 90% water. Water is a medium of transportation and a solvent for respiratory gas, ions, digestive products and excretory substances. | | Plasma proteins | Fibrinogen plays a role in blood clotting. Albumin controls blood osmotic pressure. Globulin is a type of antibody that is involved in the body’s defence.| | Solutes - nutrients such as glucose, excretory substances such as urea and respiratory gas | Nutrients are important for energy, growth and maintenance of health. Excretory substances are toxic substances that need to be disposed off from the body. Oxygen is required in the respiration of cells. | | Hormones and enzymes | Hormones control physiological activities in the body. Enzymes are involved in the metabolic processes of cells. | ### Characteristics and functions of blood cell types | Blood cell type | Characteristics | Functions | |---|---|---| | Erythrocyte (red blood cell) | * Has an elastic plasma membrane. * The biconcave disc shape enables a large TSA/V for efficient gaseous exchange. * It does not have a nucleus at the mature stage so that more haemoglobin can be loaded into it. * It is produced in the bone marrow of bones such as the sternum and ribs. * Can live up to 120 days and is destroyed in the liver or lymph through the phagocytosis process. | * Each erythrocyte has a haemoglobin which is the red pigment that gives blood its red colour. * Haemoglobin contains a heme group. The heme group consists of an iron atom which is the binding site for oxygen. * Haemoglobin combines with oxygen to form oxyhaemoglobin in high oxygen partial pressure conditions. * Oxyhaemoglobin releases oxygen in tissues or cells when the partial pressure of oxygen is low. | | Platelet | * Platelets are produced from fragments or scraps of cell cytoplasm that originate from the bone marrows. * The life span is less than one week. | * Involved in the blood clotting process. | | Leucocyte (white blood cell) | * The shape is irregular and is not fixed. * Contains nucleus. * Does not contain haemoglobin. * Produced in the bone marrow. * Life span is less than five days. | * Leucocyte can diffuse out of the capillary pore and fight pathogens in tissue fluids. It is divided into two types: granulocytes (contain granules) and agranulocytes (no granules). | ### Granulocytes * **Neutrophil:** The nucleus is made up of two to five lobes. Ingests bacterial cells and dead cells or tissues from wounds by phagocytosis. * **Eosinophil:** The nucleus is made up of two lobes. Releases enzymes that fight inflammation and allergy reaction. * **Basophil:** The number of basophils is lowest in the blood. It contains heparin that prevents blood clotting. ### Agranulocytes * **Lymphocyte:** Contains a large nucleus with very little cytoplasm. Produces antibodies to destroy bacteria and viruses that enter the body. Can also produce antitoxins against toxins that are produced by bacteria or viruses. * **Monocyte:** The biggest leucocyte. Spherical-shaped nucleus. Ingests bacteria and dead cells or tissues by phagocytosis. ## Human Blood Vessels * **Arteries:** Blood vessels that transport blood out of the heart. The function of the artery is to quickly transport blood at a high pressure to the tissues. * **Capillaries:** Blood vessels with thin walls, as thick as one cell. Blood capillaries allow the exchange of gases to occur between blood and cells through diffusion. Nutrients, excretory substances and hormones diffuse through blood capillaries. * **Veins:** Form larger blood vessels called veins that transport blood back to the heart. Vena cava is the main vein that carries deoxygenated blood back to the heart. ### Differences between arteries, capillaries and veins | Characteristics | Artery | Capillaries | Veins | |---|---|---|---| | Wall | Wall is thick, muscular and elastic. | Wall is as thick as one cell, not muscular and not elastic. | Wall is thin, less muscular and less elastic. | | Lumen | Small. | Very tiny. | Large. | | Valve | No valve except for semilunar valve at the base of the aorta and at the base of the pulmonary artery. | No. | Contain valves to maintain one-way flow of blood. | | Blood pressure | High. | Low. | Very low. | | The direction of blood flow | From the heart to the entire body. | From the artery to the vein. | From the whole body to the heart. | ## Mechanism of Heartbeat * The heart is made up of cardiac muscles that intersect and are connected with one another. This arrangement allows electric impulses to spread rapidly through the heart and at the same time, stimulates the cardiac muscle cells to contract simultaneously and uniformly. * Cardiac muscles are **myogenic**. This means that the heart contracts and relaxes without receiving any impulse signal from the nervous system. If the cardiac muscles are stored in a warm oxygenated solution that contains nutrients, these muscles will contract and relax rhythmically on their own. ### Blood circulation in humans * The produced force that enables blood to circulate in humans is generated by the pumping of the heart and the contraction of the skeletal muscles. ### Pumping of the heart * The contraction of the heart is initiated and coordinated by the **pacemaker**. The pacemaker is a group of specific heart muscle cells that initiates the rate of heart contraction and is located at the right atrium wall. #### The sequence of heart contraction that causes the pumping of the heart 1. The sinoatrial node (SA) generates electrical impulses. 2. Electrical impulses spread rapidly in both the atria, causing the atria to contract simultaneously. The contraction of the atria helps to pump blood into the ventricles. 3. The electrical impulses reach the atrioventricular node. The electrical impulses spread through the bundle of His, and the Purkinje fibres up to the apex of the heart. 4. The electrical impulses spread from the apex of the heart to the whole ventricle wall. As a result, the ventricles contract to pump blood out to the lungs and body. ### Contraction of skeletal muscles around the veins * The pumping of the heart helps in the distribution and flow of blood through the arteries, arterioles and blood capillaries. However, the force produced by the pumping of the heart is insufficient for the blood flow to continue through the veins and return to the heart. Besides, the blood is forced to flow against the force of gravity. The presence valve in the veins ensures that the blood flows in one direction to the heart. ### Mechanism of Blood Clotting * Blood clotting involves a series of chemical reactions that takes place in the blood when someone is injured to prevent excessive bleeding. #### The mechanism of blood clotting 1. The coagulated platelets, damaged cells and clotting factors in the blood plasma will form an activator (thrombokinase). 2. Thrombokinase, with the aid of calcium ions and vitamin K, converts prothrombin to thrombin. 3. Thrombin (active plasma protein that acts as an enzyme). Thrombin catalyses the conversion of fibrinogen to fibrin. 4. Fibrin (insoluble). Fibrin is a threadlike protein fibre that forms a network on the wound surface to trap erythrocytes and to close the wound to prevent blood loss. ### Health issues related to blood clotting * Under normal conditions, blood does not clot in blood vessels that are not damaged because of some anticoagulants such as heparin. #### Haemophilia * An example of an illness that prevents blood from clotting. * A hereditary illness caused by the lack of certain clotting factors in the blood. * Excessive bleeding due to small wounds or bruises can result in death. #### Thrombosis * Formation of a blood clot (thrombus). * Thrombosis happens as a result of: * Damage in blood vessels, or * Sluggish blood flow that causes clotting factors to accumulate. #### Embolism * When a blood clot is transported by blood flow, the blood clot is called embolus. * If the embolus gets stuck in a tiny blood vessel, the blood flow will stop. ## Blood Groups of Humans ### ABO blood group * Human blood is classified into A, B, AB and O groups. * Donation and transfusion of blood is based on the compatibility of the blood group of the donor and the recipient. * This is because the recipient has antibodies in the blood serum that can act against the antigen on the red blood cells of the donor. * Blood transfusion from a donor to a recipient must take into consideration the blood group type of the donor and the recipient. * If the blood group of both the donor and receiver is not compatible, the red blood cells of the recipient will experience agglutination (coagulation). #### Antigen and antibody in blood groups | Blood group | Antigen on red blood cells | Antibody in the blood serum | |---|---|---| | A | Antigen A | Anti-B | | B | Antigen B | Anti-A | | AB | Antigen A and Antigen B | No | | O | No | Anti-A and Anti-B | #### Compatibility of blood donor group with the recipient | Blood group | Can donate blood to blood groups | Can receive blood from blood groups | |---|---|---| | A | A and AB only | A and O only | | B | B and AB only | B and O only | | AB | AB only | A, B, AB and O | | O | A, B, AB and O | O only | ### Rhesus Factor * Another antigen found on the surface of the red blood cells is the Rhesus factor (Rh factor). * The red blood cells of an individual with the Rh factor or antigen D are known as Rh-positive. * An individual who does not possess the Rh factor or antigen D is known as Rh-negative. * If the blood of a Rh-positive donor mixes with the blood of a Rh-negative recipient, the blood of the recipient will react by producing the Rhesus antibody or anti-D antibody. * When the recipient receives another dose of Rh-positive blood, the Rhesus antibody will cause the agglutination of the donor blood cells. * This situation could result in the death of the recipient. ### Pregnancy and the Rhesus factor * Problems will arise when an Rh-negative mother marries an Rh-positive father and conceives an Rh-positive foetus. * During the last month of pregnancy, fragments of foetal blood cells containing antigen D cross the placenta and enter the blood circulation of the mother. * As a result, the white blood cells in the mother's blood will react and produce anti-D antibodies that will flow back through the placenta into the foetal blood circulatory system. * The antibodies will destroy the red blood cells of the Rh-positive baby before or immediately after birth. * The concentration of antibodies produced is not enough to affect the first child. But the anti-D antibodies will last in the blood circulatory system of the mother. * The problem arises when the second child is also Rh-positive. The anti-D antibodies that are present in the mother's blood cross the placenta and destroy the red blood cells of that foetus. The symptoms of this disease are called erythroblastosis fetalis. * The second foetus dies if the blood is not replaced with Rh-negative blood through blood transfusion. * In a less serious situation, the baby may suffer from anaemia and mental retardation. However, this problem can now be addressed by treating the affected mother with anti-Rhesus globulins after the first pregnancy to stop the formation of anti-D antibodies. ## Health Issues Related to the Human Circulatory System ### The necessity for a healthy circulatory system * A healthy circulatory system is important to ensure optimum health. * Practices for maintaining the circulatory system are a balanced intake of food that is low in fat and regular exercise. * The practice of not smoking and not drinking alcoholic drinks also ensures a healthy circulatory system. ### Cardiovascular diseases * Cardiovascular diseases are the leading cause of death in many countries. * Cardiovascular diseases include diseases related to the heart and the blood circulatory system such as atherosclerosis, arteriosclerosis, angina, hypertension, myocardial infarction (heart attack) and stroke. #### Cardiovascular diseases 1. **Atherosclerosis:** The formation and deposition of plaque on the artery walls. The plaque is formed from cholesterol, lipid, dead muscle tissues and coagulated platelets. The plaque will clog and narrow the lumen in blood vessels. 2. **Hypertension:** The restricted blood flow can cause hypertension. Hypertension causes fine arteries to break and the patient can suffer from stroke if this happens in the brain. 3. **Stroke:** Also caused by blood clots (thrombus) that clog the flow of blood in the brain. 4. **Arteriosclerosis:** The early stage of arteriosclerosis. Arteriosclerosis occurs when calcium is deposited on the plaque and causes the artery to become hard and lose its elasticity. 5. **Angina:** If the lumen of the coronary artery (artery for the heart) is narrowed, the insufficient oxygen supply to the heart muscles can cause angina (severe chest pain). 6. **Myocardial infarction (heart attack):** If the artery is completely clogged, myocardial infarction (heart attack) will occur. ## Human Lymphatic System * In addition to the blood circulatory system, there is one more system in the body whose function is closely related to the blood circulatory system. * This system is called the **lymphatic system**. ### The formation of tissue fluid 1. Blood that reaches the arterial end of the blood capillary has a high pressure due to the small diameter of capillaries and the pumping force of the heart. 2. This pressure allows the blood plasma to diffuse continuously from the blood capillaries to the intercellular space. 3. Blood plasma that occupies the intercellular space and constantly bathes cells is called tissue fluid. The tissue fluid does not contain any erythrocyte, platelet and plasma protein because these are too large to diffuse out of the blood capillaries. 4. Tissue fluid allows the exchange of materials in the blood and cells to occur. Nutrients and oxygen diffuse from tissue fluid to body cells. Simultaneously, excretory products and carbon dioxide diffuse from body cells to blood capillaries through the tissue fluid. ### Lymph formation and components of the lymphatic system * At the venule end of the blood capillary, blood plasma is hypertonic compared to the tissue fluid surrounding it. * Blood pressure is also lower. As a result, the reabsorption of water, mineral salts and waste takes place in the venule capillary. * Only 85% of the fluid that leaves the blood at the arteriole end of blood capillary diffuses back into the venule end. * The remaining 15% that is left in the intercellular space forms about 4 litres of fluid that is lost from capillaries each day. * This fluid is collected and returned to the blood through the lymphatic capillary, which is the smallest vessel in the lymphatic system. * This fluid is known as lymph and is pale yellow in colour. ### Comparison between lymph and tissue fluid/blood #### Similarity * Both contain plasma without the plasma proteins, erythrocytes and platelets. #### Differences: Lymph vs. Tissue Fluid | Lymph | Tissue Fluid | |---|---| | Higher content of fat and fat-soluble substances | Low content of fat and fat-soluble substances | | High content of lymphocytes | Low content of lymphocytes | #### Differences: Lymph vs. Blood | Lymph | Blood | |---|---| | Does not contain plasma protein, erythrocyte and platelet | Contains plasma proteins, erythrocytes and platelets | ### The lymphatic capillary * Consists of one layer of cells only. * One of its end is blocked or closed while the other end is connected to the lymphatic vessel. * Lymphatic capillaries found in intercellular spaces merge to form a larger lymphatic vessel. * Along the lymphatic vessel, there are lymph nodes at certain distances. ### The lymphatic system * Consists of organs such as lymph nodes, spleen, thymus gland, bone marrow, tonsils and appendix. * The lymphatic system does not have its own pump to circulate the lymph along the lymphatic vessel. The flow of lymph is aided by heartbeat pulse, contraction of skeletal muscles, peristalsis in the digestive tract and changes in pressure during inhalation and exhalation of breath. * In the lymphatic vessel, one-way valves ensure the lymph flows continuously to the heart. * These valves also prevent the lymph from flowing back. ### Relationship between the blood circulatory system and the lymphatic system * All lymphatic vessels will eventually join with one of the two main lymphatic vessels which are the thoracic duct dan right lymphatic duct. ### The necessity of the lymphatic system * Complements the blood circulatory system: The lymphatic system returns the excess tissue fluid in the intercellular space into the blood flow. The composition, pressure and volume of blood are maintained at a normal range. * Necessities of the lymphatic system: * **Body Defence:** Lymph nodes produce and store lymphocytes that are involved in the production of antibodies. * **Transportation of Fat-Soluble Substances:** Fats and fat-soluble substances diffuse into the lacteal in the villus of the small intestine. Lacteals are lymphatic capillaries. Lipid droplets are transported to the thoracic duct and blood circulatory system through the left subclavian vein. ## Health Issues Related to the Human Lymphatic System * If the lymphatic system does not function properly, tissue fluid that is not returned to the blood flow will accumulate in the intercellular space. * This will result in the swelling of the body tissues. * This condition is known as oedema. ### Causes of oedema * **Pregnancy:** The body will produce more body fluid to fulfill the needs of a growing foetus. * **Prolonged Bedridden Patients:** Paralysed or stroke patients with limited mobility can suffer from oedema in the legs. * **Deficiency in plasma protein:** Deficiency of albumin in the blood. * **Parasitic infection:** The parasite worm Brugia sp. infects the lymphatic vessel and prevents the flow of lymphatic fluid. The infected part, for example, leg will swell. The patient contracts lymphatic filariasis. This worm is transmitted through mosquito bites.