The Life & Times of RBC                                                                                                                                                  

Birthplace Blood cells are produced in the in the red bone marrow (tissues within the ends of the bone that replaces and produces the red blood cells and is also the manufacturing site of white blood cells) of the interior of bones. Source: http://www.healthcare.ucla.edu/transplant/images/bonemarrowtransplant_1.jpg

Components of Blood Blood is made of cells and proteins. Fluid Fraction: Plasma (55% of blood volume) Over 90% is water. 60 proteins are present in blood. The most important are: albumin, which is involved in osmotic balance; globulins, involved in immune response; fibrinogen, which is responsible for blood clotting. Cellular Fraction (45% of blood volume) Consists of red blood cells, white blood cells & platelets. Red blood cells make up 99% of all blood cells. The remaining cells are white blood cells and blood platelets.

Blood Cell Family red blood cells (erythrocytes) white blood cells (leukocytes) lymphocytes neutrophils basophils monocytes platelets

Red Blood Cells (Erythrocytes) These cells number in the trillions and are the greatest number of blood cells in the body. Produced mainly in the red bone marrow, but are also produced in the liver & spleen. As they die, the red marrow replaces them in enormous numbers at a rate of about a million a minute. The main function of is to transport O2 (oxygen). To create as much space as possible for hemoglobin, the cell nucleus disappears as the cell matures, changing their name to red corpuscles or erythrocytes. Because they have no nucleus, their life span is decreased to about 120 days (four months).

Hemoglobin Hemoglobin is a complex iron protein substance. It is the component of red blood cells which gives red blood cells their special oxygen carrying proficiency as well as their colour. Although other substances in the body such as water and plasma can also carry oxygen, hemoglobin is unique in its oxygen carrying capacity because it increases by more than 50 times the quantity of oxygen it can carry.

White Blood Cells (Leukocytes) These cells are diverse in shapes and sizes, they are larger in size and rounder than the red blood cells, but fewer in number (a ratio of about 1:700). Leukocytes or white corpuscles are developed in bone marrow, the replacement of white blood cells can take place in a number of locations in the body: in the lymph nodes, in the intestinal tract , and in the spleen. They do have nuclei. They have three main functions: response to tissue damage and help with its repair; defense of the body against foreign organisms; and scavenging dead cell debris. Pus is the remaining protein fragments of neutralized foreign bacteria and dead white cells after the immune battle has taken place.

Specific WBC & Their Functions T- & B-Lymphocytes 20-40% of all leukocytes are T- and B-lymphocytes. Their function is to mount an immune response in the face of infection, they are the grunts. Neutrophils Neutrophils are small, very mobile cells, they travel across the epithelial layer and enter the tissues. Neutrophils devour pathogens by phagocytosis, they are the rangers. Basophils Basophils are involved in blood clotting, but they also contain enzymes to destroy invading bacteria, they are the engineer corps. Monocytes When stimulated, monocytes transform into macrophages. Macrophages are the heavy cavalry of the defense mechanism; they phagocytize most of the pathogens, they are the tanks.

Platelets (Thrombocytes) Platelets are not even cells, they are parts of cells, chunks of cytoplasm surrounded by plasma membranes. Platelets lack nuclei and are one fourth of the size of red blood cells. They are a crucial part of the blood clotting mechanism Platelets travel with the blood and assist to prevent the organism from bleeding to death if it experiences even the smallest of wounds. They activates some of the first biochemical processes needed to clot blood. The change of blood from a fluid to a solid is called clotting .

Blood Groups The ABO blood group was the first blood group system discovered, by Landsteiner at the beginning of this century. Based on 2 antigens (agglutinogens): A & B. genetically coded for found on the surface of the cell membrane You have the antibodies for the antigens that are NOT present. antibodies (agglutinins) develop after birth in the plasma of the blood 4 Types: A, B, AB, & O. Incompatible types based on antigen/antibody components.

What happens if we mix blood types? A reaction outside the body between like antigens and antibodies results in agglutination where the blood cells clump together. A reaction within the body between like antigens and antibodies results in hemolysis of the cells (they burst).

Rh Factors Three genes code for the the Rh antigens present on the RBC cell membrane. Rh+ – Rh anitgens are present on the RBCs Rh- – Rh antigens are not present on the RBCs Normally the plasma does not contain Rh antibodies. Rh- individuals that receive Rh+ blood can have their immune systems develop Rh antibodies that will remain in the blood.

Circulatory System Functions regulates osmotic balance regulates pH transports nutrients and gases carries hormones regulates temperature is part of the immune system

Blood Vessels Blood vessels are part of a closed extensive network of narrow elastic passageways whose main function is to circulate blood to all the far out places of the body. In a closed system would take blood go along this route: heart > arteries > arterioles > capillaries > venules > veins and then back to heart. There are two kinds of blood vessels: arterial arteries (carry blood away from the heart) and venous veins (carry blood toward the heart to be re-pumped).

Arteries & Arterioles Arteries have to bear high hydrostatic pressures created by the heart, they are composed of three main layers: a outer layer of connective tissue; the middle layers are composed of a thick-walled layer made of smooth muscle (to resist high pressure), containing a layer of collagen fibres (to give elasticity), and a smooth inner connective tissue layer lined with endothelial cells (to protect red blood cells from mechanical damage) The aorta is the largest artery in the body and the primary blood vessel which carries oxygenated blood out of the heart to the rest of the body.

Capillaries Capillaries are the “heart” of the circulatory system, all the action is in the capillaries, and all other blood vessels merely assist them. Capillaries, are the smallest blood vessels in the body and form a network that allows blood and cells to exchange substances (such as oxygen). Capillaries are very narrow (10 mm diameter, the red blood cells that travel through capillaries are 6 mm in diameter). Capillaries are made of thin endothelial cells (one layer thick); the cells fit loosely, and nutrients go through pores between the cells.

Physical Mechanism of the Capillaries The blood flow across the capillary bed is regulated by a sphincter muscle on the arteriole side, whenever there is little need to supply blood to a given capillary bed, the sphincter closes and blood bypasses the capillary bed via an arterio-venal shunt. The reason for the shunt is to avoid the large pressure drop across the bed caused by the small size of the capillaries, which create a bottleneck. This bottleneck means that, on the arterial side of the capillaries (before the blood enters capillary bed), blood is under high pressure, whereas the blood at the venal side (at the end of the capillary bed) is under low pressure.

Capillary Fluid Exchange The high hydrostatic pressure on the arterial side squeezes water and nutrients out of the capillaries. Water leaving the capillaries builds up the osmotic pressure because since the blood components become more concentrated. Towards the venal end, water and waste materials are sucked into capillaries by the osmotic pressure. Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Veins & Venules Veins are blood vessels in which blood flows toward the heart conveying deoxygenated blood. The tissues of the veins are thinner, less flexible, and less muscular than the arteries because there is little pressure to bear. The veins have pocket (venous) valves to prevent back-flow. The skeletal muscles work with the valves to move the blood back to the heart. The venules are the smallest vessels that collect blood from the capillaries and join to form veins.

The Heart The heart is just a pump. The heart is fist-sized muscle. Through its pumping action it helps to circulate blood through the body. The heart must be unceasingly supplied with rich fresh oxygen and used blood must be returned to the lungs for reoxygenation. It has a right and left side partitioned by a sinewy wall of muscle called a septum .

Atria & Ventricles Atria Ventricle The upper chamber of the heart has two atria, the right atrium and the left atrium. The atria serve as a holding cache for blood that enters the heart. Ventricle The lower chamber of the heart has two ventricles , the right ventricle and the left ventricle. The left ventricle has the responsibility of pumping blood to the entire body and therefore is somewhat bigger and more muscular than the right ventricle, it has an opening that blood flows through to the aorta (the central artery where blood circulation originates throughout the body).

The Double Pump In order to split the work, a double circulation evolved that has one pump for each capillary bed. The heart consists of a double pump: the pulmonary circuit – the right atrium/ventricle combination pumps deoxygenated blood to the lungs; and the systemic circuit – the left atrium/ventricle pumps oxygenated blood through the body capillaries. In the double system, deoxygenated and oxygenated blood take separate routes through the heart.

The Pulmonary Circuit The system of blood vessels that carries deoxygenated blood to the lungs and oxygenated blood back to the heart. The deoxygenated blood arrives from body via capillaries > vena cavae > right atrium > right ventricle > pulmonary artery > lungs (alveoli) > pulmonary veins > left atrium

The Systemic Circuit The system of blood vessels that carries oxygenated blood to the tissues of the body and deoxygenated blood back to the heart. The oxygenated blood arrives from the lungs to the left atrium>left ventricle > aorta > the rest of the body

Setting the Heart’s Tempo The heart is made of specialized muscle, cardiac muscle, which is incredibly resistant to fatigue. Your heart must contract 2-3 billion times during your lifetime. The heart is myogenic, that is, it initiates own contractions and does not need the brain to do it. The Heart’s pacemaker, called the sinoatrial (SA) node is located near the entrance to the right atrium, causes simultaneous contraction of both atria and then both ventricles. Gap junctions in cardiac cells help rapid spread of the impulse to all cells irrespective of distance from the pacemaker.

The Heart Beat Activation of heart beat: the impulse from the SA node spreads on the walls of the atria; it arrives at the atrioventricular (AV) node, placed along the inter-ventricular septum; the impulse follows these fibres to the ventricles; and spreads along the ventricle walls through Purkinje fibres.

Lubb-Dubb The two sounds of a beating heart are made by the closing atrioventricular and aortic valves and correspond to the two phases of the heart cycle: systole and diastole. Systole is the contraction of the atria, during which the ventricles fill with blood, followed by contraction of the ventricles, which pushes blood out past the aortic valve to the arteries. To prevent back-flow to the atrium, the atrioventricular valve closes, making a sharp sound. Systolic contraction is followed by relaxation of the heart, diastole. Relaxation of the ventricles results in loss of pressure in the heart and closure of the aortic valve by the pressure in the aorta.

Heart Regulation Although the heart initiates its own beat, the nervous system can accelerate the heartbeat (via the sympathetic nerves) or slow down the beat (via the vagus nerve). The heart is also under hormonal control. For example, the hormone adrenaline accelerates the heart beat.

Cardiovascular Diseases Heart attack (myocardial infarction): is caused by heart ischemia (lack of O2) usually caused by obstruction by a blood clot. Stroke (cerebral infarction): clot in the brain or rupture of a weak blood vessel. Atherosclerosis: thickening of artery walls, which narrows the atrial lumen, is the leading cause of death.

Blood Pressure The pressure of the blood on the walls of the blood vessels. Measured in two numbers. The first, systolic pressure (top number), measures the pressure of the blood against the artery walls as the heart contracts. The second (bottom number), diastolic pressure, measures the pressure against the artery walls when the heart relaxes between beats. Normal blood pressure is 120/80 mm Hg.

Lymphatic System Sponge and re-circulate: Transportation: Immunity: A lot of water is lost in the blood capillaries, the lymphatic system collects this water from the tissues and empties it into the circulatory system. Lymphatic vessels are thin walled and have valves for unidirectional flow like the veins. They join to form the thoracic duct and right lymph duct, which empty near the heart. Transportation: Another function of the lymphatic system is to transport lipids and molecules that are too large to cross the walls of capillaries, e.g., some hormones and large proteins. Immunity: The lymphatic system is also a part of the immune system. Lymphocytes (white blood cells) congregate in lymph nodes.

Components of Blood Diagram Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Cells of the Blood Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Erythrocyte Structure Source: www.bio.psu.edu/.../Biol142/ blood/bloodlab.html

Source: www.bio.psu.edu/.../Biol142/ blood/bloodlab.html Hemoglobin Structure Source: www.bio.psu.edu/.../Biol142/ blood/bloodlab.html

Types & Functions of WBC Source: http://www.colorado.edu/epob/epob1220lynch/image/figure11a.jpg

ABO Blood Type Compatibility Source: http://opbs.okstate.edu/~melcher/MG/MGW1/MG11121.html

Major Arteries & Veins Copyright © 2002 by Nelson Thomson Learning, a division of Thomson Canada Ltd.

Arterio-Venal Shunt Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Capillary Fluid Exchange Diagram Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Venous Valves Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Heart Diagram Copyright © 2002 by Nelson Thomson Learning, a division of Thomson Canada Ltd.

Blood Circulation in the Heart Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Pulmonary Circuit Diagram Copyright © 2002 by Nelson Thomson Learning, a division of Thomson Canada Ltd.

Systemic Circuit Diagram Copyright © 2002 by Nelson Thomson Learning, a division of Thomson Canada Ltd.

Heart Beat Diagram Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Heart Sounds Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Lymphatic System Components Source: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm

Sources: http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/30_Circulatory.htm http://learning.mgccc.cc.ms.us/science/blood/index.htm http://library.thinkquest.org/2935/Natures_Best/Nat_Best_High_Level/Circulatory_Net_Pages/Circulatory_page.html#blood