Chapter 5: Blood - PDF

Body's main internal transport system is circulatory system, it's the link between the cells inside the body and environment outside the body for cell requirements. Blood is the transport link between the cells of all the body systems, it maintains the constant internal environment of the body. Som...

Body's main internal transport system is circulatory system, it's the link between the cells inside the body and environment outside the body for cell requirements. Blood is the transport link between the cells of all the body systems, it maintains the constant internal environment of the body. Some functions are: - transporting oxygen and nutrients to all cells of the body - transporting carbon dioxide and other waste products away from the cells - transporting chemical messengers, called hormones, to the cells. - maintaining the pH of body fluids - distributing heat and maintaining body temperature - maintaining water content and ion concentration of the body fluids - protecting against disease-causing micro-organisms - clotting when vessels are damaged, thus preventing blood loss. Blood is composed of: - the liquid part, which is plasma, this makes up 55% of blood volume. - the non- liquid part, which is the formed elements, this makes up 45% of blood volume and consists of erythrocytes, platelets, and leucocytes. Plasma: - mixture of water with dissolved substances such as sugar and salt - function is to transport components of blood including cells, nutrients, wastes, hormones, proteins, and antibodies throughout the body. Erythrocytes: - most abundant cells in the body - 40-45% blood volume (Hematocrit %) - Biconcave disc shape meaning its flattened in middle on both sides, increases surface area. - Don't contain a nucleus which increases flexibility and room for haemoglobin. - Lack of nucleus limits life span to 120 days - Function of erythrocytes of to transport oxygen from the lungs to cells throughout the body - They are produced in the bone marrow and destroyed in the liver and spleen. Leucocytes: - Protect body from infection. - 1% of blood and larger that red blood cells - There are number of different leucocytes each with own structure and function: - **Granulocytes (with packages of enzymes)** - They have a granular cytoplasm with a lobed nucleus. - Neutrophils -- most common type, contain enzymes to digest pathogens. - Basophils -- responsible for allergic reactions as they produce histamines to defend the body against parasites and bacteria. - Eosinophils -- lead to inflammatory responses as they respond to larger parasites like worms. - **Agranular (non-granular)** - They have a spherical nucleus and agranular cytoplasm. - Monocytes -- form other cells like macrophages that engulf pathogens, damaged cells by phagocytosis. - Lymphocytes -- involved in immune response, cell immunity uses T-lymphocytes, antibody immunity uses B-lymphocytes. Thrombocytes: - They are small fragments of cells with no nucleus. - When a blood vessel is injured, the platelets adhere to lining and form a scaffold for coagulation of the blood to form a clot. - They are formed in the red bone marrow and last for about 7 days. Transport of Oxygen: - Oxygen is not verry soluble in water so 3% is carried in solution is plasma. - Other 97% is carried in combo with hemoglobin molecule only in RBC. - Hemoglobin combines with oxygen to form oxyhemoglobin. - Oxygenated blood has oxyhemoglobin which means its bright red in color in arteries. - Deoxygenated blood in veins is dark red. - The combination of oxygen and hemoglobin is a loose bond because O~2~ can easily break away in capillaries for gas exchange. - The presence of hemoglobin in RBC increases oxygen-carrying capacity of blood by 60-70 times. - When oxygen concentration is high it combines with hemoglobin. This occurs in the capillaries in the lungs where oxygen diffuses into the blood from the air in alveoli. - Oxyhemoglobin breaks down to hemoglobin and oxygen when the concentration of o2 is low. - This occurs because as the cells of the body continually use up oxygen, the tissue fluid around cells has low oxygen concentration because when RBC flow through the capillaries of body cells they give up their oxygen which diffuse into tissue fluid and into cells. Transport of Carbon Dioxide: - 8% dissolved in plasma and carried in solution. - 22% combines with globin part of haemoglobin to form carbaminohaemoglobin. - 70% is carried in plasma as bicarbonate ions, HCO3. - As blood flows through capillaries of body, co2 diffuses into plasma due to difference in co2 concentrations. - Some co2 dissolves in plasma, some combines with haemoglobin. - Most reacts with water to form carbonic acid (h2co3). Carbonic acid then ionises into hydrogen ions and bicarbonate ions. - The alveoli are surrounded by a network of blood capillaries so co2 dissolved in plasma diffuses out of blood into air in alveoli. - The carbaminohaemoglobin breaks down and co2 molecules released diffuse into alveoli. - Hydrogen ions and bicarbonate ions recombine to form carbonic acid which breaks down under enzyme action into water and co2 which diffuses into alveoli. Transport of Nutrients and Waste: - Nutrients are obtained from food we eat. - Inorganic nutrients are transported as ions dissolved in the plasma like Na, Ca, K, Cl, I ions. - Organic nutrients are dissolved in blood plasma like glucose fatty acids, Amino acids, Vitamins etc. - Metabolic wastes are substances not used by cells or harmful if accumulated so they are transported in plasma like urea, creatinine, and uric acid. Blood Clotting: - When an injures occurs damaging the blood vessels the events that follow minimise blood loss and entry of pathogens: - Vasoconstriction: muscles in the walls of the arteries constrict to reduce blood flow - Platelet Plug: internal walls of smooth muscle are normally smooth, but any damage creates a rough surface to which platelets stick. Sticking platelets attract others and so a plug is built at site of injury helping reduce blood flow. The platelets release substances that act as vasoconstrictors which enhance constriction of damaged vessels. - Coagulation: for more serious injuries, blood clotting occurs. Blood clotting involves clotting factors that are present in the blood plasma. The complex series of reactions results in formation of threads on insoluble protein called fibrin and these threads form a mesh to trap blood cell, platelets and plasma and hold the clot in position. This mesh with trapped material is clot, thrombus. - Clot retraction occurs slowly as network of threads contract becoming denser, pulling the edges of damaged blood vessels together. A serum squeezes out then clot dries forming a scab over wound that prevents entry of infecting micro-organisms. [Moving Blood Though the Body] Heart: - 4 chambered pump that pushes blood around body. - Located between two lungs in mediastinum, slightly left to the sternum. - 12cm long -- 9cm wide -- 6cm thick (human fist) - It is enclosed in a membrane called pericardium that encloses heart, allows movement, and prevents overstretching. - The wall of heart is made up of cardiac muscle. - Left and right side of heart is separated by a wall called septum. - Right side of heart collects blood from the body and pumps it to the lungs. - Left side receives blood from the lungs and pumps it to the rest of the body. Heart Anatomy: - 4 chambers in heart - Top chambers are atria (singular -- atrium) - Bottom chambers are ventricles. - Right Atrium receives blood from body and passes it to right ventricle. - Right ventricle pumps blood to lungs - Left atrium receives blood from lungs and passes it to left ventricle. - The left ventricle pumps blood to body - The wall of the left ventricle is thicker than the wall of the right because it needs to be stronger to pump blood throughout body. Heart Valves: - Valves ensure that blood can only flow in one direction. - Between the atria and ventricles are the atrioventricular valves - Between right atrium and right ventricle is the tricuspid valve with three flaps - Between left atrium and left ventricle is the bicuspid valve which has two flaps - The atrioventricular valves are flaps of thin tissue with edges held by tendons called chordae tendinea, that attach to heart on papillary muscles. - When ventricles contract the blood catches behind flaps of tissue, and they parachute out sealing off atria. - Then blood leaves heart through arteries and not flow back into atria - When arteries leave the hear the second set of valves stop blood from flowing back into ventricles when ventricles relax. - There are semilunar valves: - Between the right ventricles and pulmonary artery is pulmonary valve which has 3 cusps - Between the left ventricle and aorta is the aortic valve which has 3 cusps - When blood flows into artery, cusps are pressed flat against the artery wall. - When blood tries to flow back into ventricle the cusps fill out and seal of the artery ensuring blood flows in one direction. - The closing of the atrioventricular and semilunar valves gives the heartbeats their lub dub sound. - Blood is pumped by the heart into blood vessels which carry the blood to cells of the body or lungs and bring it back to the heart again. - Circulations is the movement of blood through the heart and blood vessels. - There are three types of blood vessels that are joined together to form the channels through which blood flows. Arteries: - Blood vessels that carry blood away from the heart - Largest artery is the aorta. - Walls contain thick muscle layer & elastic fibers, when ventricles contract and push blood into arteries their walls stretch to accommodate extra blood. - When ventricles relax the elastic artery walls recoil to keep the blood moving and maintain pressure - Muscles can contract to reduce blood flow to organ- vasoconstriction. Vasodilation is the muscle relaxing to increase blood flow. This allows blood flow to be controlled. - Large arteries divide into smaller **arterioles** that have smooth muscle and that supply blood to capillaries. - Vasodilators are wastes from cellular respiration which produce a widening of the arterioles which results in increased blood flow through muscle tissues ensuring cells have oxygen. - Cellular respiration also releases heat energy which increases blood temperature and hear rate. - **They have a thick muscle, elastic wall that constricts and expands.** - **Narrow lumen** - **Blood flows at high pressure** capillaries: - Link between arteries and veins. - Form a network to carry blood close to mostly all cells enabling them to get requirements from blood and pass waste into blood. - 1 cell thick and thin walls helping with diffusion allowing substances to pass easily between blood and cells. - Narrow lumen - Blood flow at low pressure Veins: - Carry blood towards the heart. - Capillaries join into smaller veins called venules which join into larger veins like inferior and superior vena cava and pulmonary veins. - Don't have muscular walls as they cannot change in diameter. - Thin walls and constant pressure so walls don't have to be elastic. - Wide lumen - Blood flows at low pressure as blood lose pressure as it flows through capillaries. - Contain valves which prevent backflow. - The blood flow through our body depends on our activities and the cells requirements. - To cater for the changes in the cell's requirements the blood flow to and from the cells must change: - by changing the output of blood from the heart - by changing the diameter of blood vessels. Cardiac Cycle: - cardiac cycle is sequence of events that occurs in one complete beat of the heart. - the pumping phase where heart muscle contracts is systole. - the filling phase where heart muscle relaxes is diastole. - for a short time, atria and ventricles are in diastole as the atria fill with blood and ventricles receive blood as valves are open. - **then** atria contract forcing remaining blood to ventricle, this is atrial systole. - then atria relax and refill while ventricles contract in ventricular systole which forces blood into arteries - left and right side of heart operate together as both atria and ventricles contract simultaneously. Cardiac Output: - flow of blood around the body depends on how fast the heart is beating and how much blood the heart pumps with each beat. - heartbeat is the number of times the heart beats per minute. - stroke volume is volume of blood forced from ventricle with each contraction. - combination of both influences cardiac output which is the amount of blood leaving one of ventricles every minute. - Cardiac output (ml/min) = stroke volume (ml) x heart rate (beats/min) Transfusions: - Blood transfusion given to a person suffering from excessive blood loss, types of leukemia, anaemia. - It involves blood form a donor injected directly into patients' bloodstream. - In 1901 Austrian Dr Karl Landsteiner mixed samples of blood from different people and lead to discovery of ABO Blood Group - 39 years later he discovered Rh blood group system. Blood Groups: - Surface of red blood cells is coated with sugar and protein molecules that stimulate the immune system called antigens. - The protein produced by the immune system is antibody. - The antigen and antibody combine to form a complex and cause a reaction. ABO Blood Groups: - There are two sugar antigens involved in ABO classification -- Antigen A and B - On surface of RBC a person may have antigen A, Antigen B, both antigens and neither antigen - These 4 possibilities correspond to the 4 blood groups A, B, AB, or O - A body's ability to make antigens and so a person's blood group is determined by their DNA and is therefore inherited. - The antibody that reacts against Antigen A is anti-A while anti-B reacts against antigen B. - A person's immune system recognizes own antigens but will recognize others as **non-self** -- make antibodies to attack. Rh Blood Groups: - Named after study of rhesus monkey blood. - Rh antigens are on surface of red blood cell and are proteins. - A person with Rh antigens is Rh positive and person without is Rh negative. - An induvial without Rh antigens can produce an anti-Rh antibody that reacts against those antigens. - Rh-positive individual cannot produce an anti-Rh antibody. Transfusions: - For a transfusion it is necessary to match the blood group of the donor and the recipient - Clotting factors may not require matching of blood groups. - The mixing of blood types that are incompatible can cause the erythrocytes to clump together or agglutinate. - If the receives blood contains or is able to make antibodies against antigens on the donors red blood cells the foreign cells will clump together and disintegrate - The first transfusion of Rh-positive blood to a Rh-negative person does not cause problems because antibodies are produced slowly, however the first exposure sensitise the person so that any exposure again results in production of antibodies and erythrocytes agglutinate. Types of Transfusions: - Whole blood is taken from donor and chemical added to prevent clotting -- severe blood loss. - Red Cell Concentrate (most common) produced by spinning blood at high speed in centrifuge causing heavier cells to sink to bottom and lighter plasma on top. White blood cells are removed and may or may not contain platelets - heart disease & severe anemia. - Platelet concentrate given to low platelet count patients or abnormal platelets. - Cryoprecipitate is freezing the plasma and thawing it slowly. When plasma is thawed cryoprecipitate remains solid and contains substances for blood clotting - hemophilia/ severe bleeding - Immunoglobulins are proteins that acts as antibodies. They are extracted from blood and used for patients who are deficient in antibodies - patients with no immunity to disease. - Autologous transfusion is when patients own blood is used and collected from patient prior to operation that may requires a transfusion. Often used for elective surgery and collected four weeks before -- eliminates risk of transmitted diseases. Blood Donor: - Free service - Always needing donations - Any healthy person aged 16-70 - Satisfaction of helping others [Lymphatic System:] - Blood enters capillaries at high pressure causing fluid escapes from capillary walls. - Functions: collect fluid that escapes capillaries and return it to circulatory system and defence against disease-causing organisms - The structure is a network of lymph capillaries which join to larger lymph vessels and lymph nodes along lymph vessels. Lymph Vessels: - Due to high pressure in the capillary fluid leaks out at arterial end. - Some of this fluid retunes to capillary at venous end. - The excess fluid (lymph) in tissue is returned to blood by lymphatic system. - This systmen is. One-way system carrying fluid away from tissue. - Lymph vessels originate as bind-ended tubes in the spaces between cells. - Capillaries are more permeable than blood capillaries. - Proteins and disease-causing organisms pass through lymph capillaries into lymph. - Network of lymph vessels join to form lymphatic ducts that empty lymph into larger veins in upper chest. - lymph moves through lymphatic vessels because of smooth muscle, skeletal muscle, and valves. - the smooth muscle layer of the vessels can contract to push lymph along the vessel, the skeletal muscles surrounding the vessels are also able to contract adding additional force. - larger lymph vessels have valves that close when the pressure drops, preventing backflow of lymph. Lymph Nodes: - Occur at intervals along lymph vessels. - Most numerous in neck, armpits, groin -- bean shaped 1mm-25mm long - Each Node is surrounded by a capsule of connective tissue which forms a framework. - Within framework are masses of lymphoid tissue containing cells known as lymphocytes, macrophages. - Lymph enters vessel on convex side of node, filters through the spaces and passes out through vessels on the opposite side. lymph passes through several nodes before entering circulatory system. Role of Lymphatic System in defense against dieses: - lymph enters carrying debris, foreign particles & micro-organisms. - large particles are trapped in the meshwork of fibers through the spaces in the nodes. - large phagocytic cells called macrophages destroy these particles, the macrophages ingest the particles by phagocytosis, projections from the macrophage surround the particle and take it into the cell, where it is destroyed by enzymes. - most bacteria ingested in this way are killed within 10 to 30 minutes. - when infections occur, the formation of lymphocytes increases, causing the lymph nodes to become swollen and sore. for example, an infected finger may result in swelling and tenderness in the armpit, where there are many lymph nodes.