Functions of Blood. Transport. Transport. Defense. Regulation. Unit 6 Cardiovascular System: Blood

Transcription

1 Unit 6 Cardiovascular System: Blood Functions of Blood With each beat of the heart, approximately 75 ml of blood is pumped On average, the heart beats 70 times per minute Every minute, the heart pumps 5,250 ml of blood per minute throughout the body If needed, the heart will pump even faster Three main functions of blood Transport Defense Regulation Transport Blood is the body s primary transport medium Acquires oxygen in the lungs and distributes it to body tissues Picks up nutrients from the digestive tract and delivers those as well Brings carbon dioxide back to the lungs Transports other wastes the kidneys for excretion Transports hormones Transport Proteins in the blood help in this transport Help transport hormones Lipoproteins (HDL and LDL) carry lipids Hemoglobin carries oxygen and assists in transporting carbon dioxide as well Carbon monoxide (CO) can also bind to hemoglobin Prevents oxygen from binding and the cells are starved of oxygen Defense Phagocytes white blood cells that engulf and destroy pathogens Lymphocytes white blood cells that produce antibodies Antibodies proteins that combine with and disable pathogens which can then be destroyed by the phagocytes When an injury occurs, blood clots to prevent blood loss Involves the platelets and proteins Prothrombin Fibrinogen Regulation Blood plays an important role in homeostasis Regulates body temperature by picking up heat mostly from active muscles, and transports it to the rest of the body If it gets too warm, blood vessels dilate, and the heat is released to the environment Plasma contains dissolved salts and proteins Maintains the water-salt balance Buffers regulate acid-base balance and keep the body at a relatively constant ph of about 7.4

2 Blood is a tissue contains cells and cell fragments Formed elements cells and cell fragments Plasma contains the formed elements Formed elements Red Blood cells White blood cells Platelets Produced in Red Bone Marrow Found in most bones of a child, but only certain bones of an adult 2-3 times smaller than white blood cells, but there are many more of them Millions in a mm 3 of blood Only thousands in a mm 3 of blood Increase in number when there is an infection present Platelets Aid in clotting Plasma Liquid medium for carrying substances in the blood Distributes the heat generated by metabolism, especially muscle activity About 91% water and the remaining 9% consists of salts (ions) and organic molecules Salts maintain osmotic pressure and act as buffers to maintain a stable ph Organic molecules like glucose and amino acids act as nutrients for the cells Plasma proteins the most abundant organic molecules in the plasma Produced by the liver Maintain ph and osmotic pressure Three major types Albumins contribute most to osmotic pressure; help to transport organic molecules Globulins three types alpha, beta, and gamma Alpha and beta transport hormones, cholesterol, and iron Gamma antibodies produced by lymphocytes, not the liver Fibrinogens inactive, but once activated, will form blood clots Erythrocytes Small (6-8 μm), biconcave disks that lack a nucleus when mature There are about 4-6 million RBCs in every mm 3 of blood Contain hemoglobin (Hb) Makes RBCs and blood red The iron part of the Hb molecule combines easily with O 2 in the lungs and then lets it go in the tissues It also combines with carbon monoxide (CO), but does not easily let it go Each Hb molecule can transport 4 molecules of O 2, and each RBC contains about 280 million hemoglobin molecules each RBC can transport over a billion molecules of O 2

3 The biconcave shape is due to losing their nuclei during maturation This shape gives them a greater surface area for the diffusion of gases into and out of the cells They also lack most organelles, including mitochondria they make ATP through anaerobic respiration in the cytoplasm When oxygen binds to hemoglobin, the shape slightly changes and is called oxyhemoglobin Once the oxygen is released into the tissues, the Hb regains its normal shape, and is referred to as deoxyhemoglobin When blood picks up CO 2 in the tissues, the distribution of CO 2 in the blood is 7% - plasma 25% - carried by hemoglobin carbaminohemoglobin 68% - transported in the bicarbonate ion (HCO 3 -) in the plasma and then diffuses out of the blood into the lungs and is exhaled The RBC stem cells in the bone marrow divide and produce new cells that will differentiate into mature RBCs As they mature, they lose their nuclei, and acquire hemoglobin Because they lack a nucleus, they are unable to produce important proteins and repair cellular damage life span of only 120 days They are then phagocytized by white blood cells in the liver and spleen About 2 million RBCs are destroyed every second and therefore an equal number must be produced When the RBCs are destroyed the hemoglobin is released and the amino acids in the Hb are recycled by the body Most of the iron is also returned to the marrow for reuse, but some is lost and needs to be replaced by diet The rest of the Hb is excreted by the liver and kidneys Jaundice - when the liver does not excrete the Hb causes yellowing of the skin and eyes The yellowing of a bruise is also caused by the breakdown of Hb Erythropoietin (EPO) a hormone released by the kidneys to stimulate the bone marrow to produce more RBCs Also made by the liver and other tissues Disorders of the RBCs Anemia lack of RBCs or not enough hemoglobin causes a tired, run-down feeling Iron-deficiency anemia lack of dietary iron Pernicious anemia lack of vitamin B 12 Folic acid anemia lack of folic acid common during pregnancy Hemolysis rupturing of RBCs Sickle-Cell Anemia hereditary condition in which the RBCs have a sickleshape Abnormal hemoglobin Life span of 90 days versus 120 Leukocytes Larger than RBCs Have a nucleus Lack hemoglobin Are translucent, unless stained 5,000 11,000 WBCs per mm 3 of blood Produced by stem cells in the red bone marrow The production of the different types of WBCs is regulated by a protein called colony-stimulating factor (CSF) In a person with normally functioning bone marrow, the number of WBCs can double within hours, if needed

4 Function as part of the immune system to fight infection Most live only a few days they die while fighting pathogens Others can live from a few months up to a few years Phagocytosis the WBC surrounds the pathogen and engulfs it, forming a vesicle lysosomes within the cells release enzymes to break it down Antibodies proteins that combine with antigens Antigen a cell or other substance foreign to the individual The antibody-antigen pair is then marked for destruction by phagocytosis Types of : Neutrophils 50-70% of WBCs Usually the first responders to infection Phagocytes Eosinophils Increase during allergic reactions or parasitic infection Basophils Release histamine during an allergic reaction Lymphocytes 25-35% of all WBCs B cells produce antibodies T cells directly destroy pathogens the AIDS virus attacks T cells Monocytes Largest WBCs Phagocytes Stimulate lymphocytes Disorders of the WBCs Severe combined immunodeficiency disease (SCID) Genetic Stem cells of WBCs lack an enzyme and the B and T cells cannot develop Treatment Injection of the enzyme and bone marrow transplants Leukemia Uncontrolled production of WBCs many are abnormal or immature and are incapable of performing their normal functions Infectious Mononucleosis Infection of the lymphocytes Fever, sore throat, swollen glands symptoms usually disappear without medication, but can remain dormant and can be reactivated by stress the kissing disease

5 Platelets Thrombocytes Come from fragments of larger cells called megakaryocytes 2 million per day are produced 150, , 000 per mm 3 of blood Involved in the process of blood clotting (coagulation) along with the plasma proteins Platelets Blood clotting involves at least 12 clotting factors plus calcium ions (Ca 2+ ) Initiated when a blood vessel is damaged At the site of the break, the platelets clump together and release prothrombin activator The prothrombin activator converts the plasma protein prothrombin to thrombin with the assistance of the Ca 2+ ions The thrombin then acts like scissors cutting two short amino acid chains from the plasma protein fibrinogen to form long chains of fibrin The fibrin then winds around the platelet plug to start to form a temporary clot Once blood vessel repair begins, the enzyme plasmin destroys the fibrin to allow for new cell growth After blood clots, a yellow serum, containing all components of plasma except for prothrombin and fibrinogen, escapes from the clot Platelets Disorders of the platelets Thrombocytopenia low platelet number; frequent nosebleeds, bruising, rashes; danger of bleeding into the brain and other internal bleeding Thromboembolism - when a blood clot (thrombus) becomes dislodged and travels through the blood (embolus) and eventually becomes stationary again Hemophilia deficiency in clotting factors; danger of bleeding into the brain; can be treated with injections of clotting factor Blood transfusion transfer of blood from one person to another Must be done between persons of the same blood type so that agglutination (clumping of the RBCs) does not occur Involves determining the ABO blood group and whether the person is Rh + or Rh - Our RBCs contain glycoproteins that act as antigens (foreign substances) to those with different blood types ABO blood typing is based on the presence or absence of 2 antigens on the RBCs Type A antigen Type B antigen The plasma contains antibodies of the opposite type if the wrong blood type is given, the antibodies can bind to the antigens on the RBCs and cause agglutination

6 Blood Compatibility very important when transfusions occur because of the risk of agglutination Universal Donor Type O Lacks both antigens Universal Recipient Type AB Lacks both antibodies Before any blood is transfused, a procedure in which the two blood types are mixed on a slide (blood-type crossmatching) is performed to make sure there is no agglutination In emergencies, Type O is given without crossmatching Rh factor Rh - individuals do not have Rh antibodies, but will make them when exposed to the Rh factor If a mother is Rh - and the father is Rh +, the baby may be Rh + During pregnancy the Rh + antigens can leak across the placenta into the mother s bloodstream and will cause the mother to produce anti-rh antibodies In a subsequent pregnancy, they may leak across the placenta and destroy the baby s RBCs Can be prevented by giving the mother an injection to prevent her from making the antibodies