 This video will cover the following objective from Physiology of Blood Hematology. Describe the composition of whole blood. Describe the functions of the major plasma proteins. Describe the structure and function of the cell types, making up the formed elements of blood, erythrocytes, types of leukocytes, and platelets. A centrifuge is a machine that's used to separate the components of blood. A tube containing a sample of blood is placed into a slot that holds the tube at an angle, and then the centrifuge spins rapidly, creating a centrifugal force that causes the more dense components of blood to move to the bottom of the tube and the less dense components of the blood to rise to the top of the tube. So on the right here we can see an illustration of what a normal blood tube would look like after being separated in a centrifuge. The top component is the plasma, which is primarily water with dissolved solutes. Some of those solutes include electrolytes like sodium ions, chloride ions, potassium ions, phosphate and carbonate. There's also lots of other nutrients dissolved in the plasma, including glucose and amino acids. There's several proteins dissolved in plasma and several hormones. The buffy coat component consists of the white blood cells, which are also known as leukocytes, and the platelets, which are also known as thrombocytes. And then the hematocrit component of the blood is primarily red blood cells, which are also known as erythrocytes. Albumin is the most abundant plasma protein, representing around 50 to 60% of the proteins dissolved in blood plasma. It has important functions in transporting nutrients like fatty acids and cholesterol and steroids and minerals. And being the most abundant protein in the plasma, it's also important in contributing to the osmolarity or the solute concentration of plasma in order to help maintain an isotonic osmolarity relative to the solute concentration of the cytosol in cells. When blood plasma is loaded into an electrophoresis gel and separated with an electric field, proteins separate out based on their relative charge and size and shape. And we see that the top band here is albumin. Now the other proteins are grouped together into the alpha-globulin bands, alpha-1-globulin, alpha-2-globulin, and the beta-globulin band, as well as the gamma-globulin band. And so there are several different proteins in the alpha and beta-globulin bands. And we'll see the gamma-globulin band primarily contains antibodies. Some of the major proteins that are found in the alpha and beta-globulin region of the plasma protein electrophoresis gel is the lipoproteins. Lipoproteins are important for transporting lipids in the blood plasma because lipids are not soluble in plasma. Lipoproteins form lipid droplets that have an outer layer of phospholipidin protein with a lipid interior that contains lipids like cholesterol and triglyceride, which would not be soluble in blood plasma without the help of the lipoprotein particle with that hydrophobic lipid interior and hydrophilic exterior. So the lipoproteins ApoB and ApoA are proteins that are found in these lipoprotein particles and are important for helping to regulate the movement of the lipids from the plasma in and out of cells. So lipoproteins are important clinically because they have the function of transporting cholesterol in the blood and elevated blood cholesterol level is associated with increased risk of cardiovascular disease. But we've learned that it's not just elevated cholesterol but in particular a certain type of lipoprotein particle containing cholesterol that is associated with the increased risk of cardiovascular disease. This is what's known as an LDL or a low density lipoprotein particle. LDLs come from other lipoprotein particles. When the liver packages cholesterol and other lipids and sends it into the blood, those lipids are being transported out in a lipoprotein particle known as a VLDL or very low density lipoprotein. Then VLDLs are distributing lipids to cells throughout the body and as the lipids are released from the VLDL, VLDLs are transformed into IDLs which are intermediate density lipoproteins and then LDLs which are low density lipoprotein particles. This LDL can be removed from the blood, can be taken back up by cells in the liver and broken down but we've learned that it is strongly associated with cardiovascular disease risk if you have a high level of LDLs in your blood. One of the ways that you can end up having an abnormally high level of LDLs in the blood is a genetic mutation that you could have inherited called familial hypercholesterolemia which is a mutation in the LDL receptor, a protein on the surface of cells that normally is involved in taking LDL out of the blood and so if that receptor isn't functioning properly, LDL levels become elevated leading to increased risk of cardiovascular disease. There's another type of lipoprotein particle that we've learned is associated with decreased risk of cardiovascular disease and this is called the HDL or high density lipoprotein. The HDLs are also produced in the liver and the function of HDLs is to travel in the blood around the body and pick up extra cholesterol from tissues and then transport that excess cholesterol to be repackaged and reprocessed so it can deliver that excess cholesterol back to the liver or to other cells but it's helping to remove lipid deposition helping to prevent deposits of lipid from accumulating in blood vessels and tissues throughout the body so the HDL is associated with decreased risk of cardiovascular disease and this is why HDL is commonly referred to as good cholesterol and contrast LDL is commonly referred to as bad cholesterol. Another protein that's found in the alpha and beta globulin bands of the plasma protein electrophoresis is called fibrinogen and fibrinogen is an important protein for the coagulation mechanism that helps to stop bleeding fibrinogen is a soluble protein that can be activated to form a cross linked network called fibrin and so in the mechanism of coagulation the soluble protein fibrinogen is converted into the insoluble fibrin protein forming a cross linked network of protein to help stabilize a blood clot in the gamma globulin band of the plasma protein electrophoresis the primary proteins found there are the antibodies which are also known as the immunoglobulins or abbreviated IG so there are many different types of immunoglobulins many different types of antibodies and these antibodies are important for the adaptive immunity they help our body defend against infections but not just helping to defend against infection in general rather antibodies are specific in that antibodies will recognize a very specific chemical pattern called an antigen and an antigen is specific for a certain pathogen and so our immune system learns to recognize the antigens from specific pathogens as we develop an acquired immunity and we start to produce more antibodies that can bind to those antigens to help defend against those specific infections the formed elements of blood are erythrocytes, leukocytes and platelets or red blood cells, white blood cells and thrombocytes the primary function of the erythrocytes is to transport oxygen and carbon dioxide in the blood the erythrocytes are the most numerous of the formed elements and they are relatively small cells that have a flattened biconcave disc shape which helps to maximize the efficiency of the exchange of gases of carbon dioxide and oxygen as oxygen and carbon dioxide can rapidly move across the erythrocytes plasma membrane as a result of a really high surface area to volume ratio leukocytes are the white blood cells that are relatively large cells and they are much less numerous than either the erythrocytes or the platelets the leukocytes do have a nucleus and so that is one thing that makes them distinctive when you're looking at blood under the microscope they're the only cells in blood that would normally have a nucleus and the major function of leukocytes is involved in defense against infection we'll study in more detail the roles of the leukocytes when we move on to the immunology section and then the platelets which are also known as thrombocytes are just small cellular fragments that are produced by cells found in the red bone marrow and so the platelets are produced from a cell called a megakaryocyte and the megakaryocyte breaks off small fragments that exit the bone marrow and move into the blood to function as the platelets or thrombocytes that help to defend against bleeding in a mechanism we call hemostasis the platelets will stick together forming a platelet plug that can block a blood vessel to help blood clotting to help stop bleeding that is to maintain hemostasis hemoglobin is the primary protein found in the cytoplasm of erythrocytes that functions to transport oxygen the structure of hemoglobin contains four globin polypeptides and each of those polypeptides contains a cofactor known as heme and the chemical structure of heme is shown on the right here the chemical structure of heme contains an iron atom which is important for helping to bind oxygen within the structure of hemoglobin and because iron is required to produce heme for hemoglobin if we have a dietary iron deficiency this will impair the ability to produce hemoglobin leading to a common form of anemia iron deficiency anemia anemia is a decreased number of erythrocytes a decreased oxygen carrying capacity of the blood and this will lead to feeling tired as you have a low oxygen availability for fueling aerobic cellular respiration and cells throughout the body leukocytes are categorized into two large groups there are granular leukocytes also known as granulocytes and agranular leukocytes also known as agranulocytes so granulocytes contain dark staining cytoplasmic granules which are just secretory vesicles that help to defend against infection by releasing chemicals that are cytotoxic chemicals or chemicals that promote inflammation or regulate inflammation whereas the agranular leukocytes do not contain dark staining cytoplasmic granules the granulocytes include basophils, eosinophils and neutrophils whereas the agranular leukocytes are the monocytes and lymphocytes neutrophils are the most common of the leukocytes in blood and they have a distinctive morphology to their nucleus where there's the appearance of multiple lobes this gives rise to a synonym for neutrophils they're also known as polymorphonucleocytes which is commonly abbreviated as polys so the polys or the neutrophils are the most abundant leukocytes typically the first cells on the scene of infection and the color of pus is white as a result of numerous neutrophils eosinophils are associated with parasitic infections where they help to defend against multicellular parasites like parasitic worms eosinophils are also associated with allergies and so there's elevated levels of eosinophils commonly seen in the patients with allergies then basophils are important for stimulating inflammation while they're the least common of the leukocytes when basophils become activated to release their cytoplasmic granules it stimulates inflammation to help recruit other leukocytes to come and defend against infection so the neutrophils are particularly effective at defending against bacterial infections where neutrophils can perform phagocytosis to engulf a bacterial cell and break it down they can also release cytotoxic granules that kill bacterial cells eosinophils are also phagocytic cells but they're particularly effective against multicellular parasites and are especially recruited to help defend against these parasites when there are antibodies binding to the surface of the parasite the antibodies will help to direct the eosinophil to come and defend against that by releasing cytotoxic granules and also performing phagocytosis to engulf fragments from the parasite basophils are the least common of the leukocytes and are important for promoting inflammation where their cytoplasmic granules contain histamine histamine is a chemical that stimulates vasodilation and increases the permeability of capillaries which helps other leukocytes to come and defend against infection lymphocytes are the most abundant of the agranular leukocytes in blood and the second most abundant of all the leukocytes in blood the function of lymphocytes is important for the adaptive immunity to specific infections that is the lymphocytes enable the immune system to form a memory against specific pathogens there are two major categories of lymphocytes T cells also known as T lymphocytes are important for the cellular immunity where they help to defend against intracellular pathogens like viruses the T cells can directly attack our own cells that have become infected stimulating a process that kills our own cells in order to prevent the virus from spreading the B cells release antibodies important for the humoral immunity the antibodies are released and travel throughout the blood and then bind to antigens on the surface of pathogens for example antibodies could bind to antigens on the surface of bacterial cells neutralizing those bacterial cells preventing them from spreading the infection throughout the body and helping to label them for other leukocytes to come and destroy those cells to defend against the infection monocytes are the largest of the leukocytes in blood the function of monocytes is important for defending against extracellular pathogens where monocytes can perform phagocytosis to engulf the pathogen and then a monocyte can break down the pathogen and display antigens from that pathogen on its surface in a process called antigen presentation monocytes function as antigen presenting cells where they display antigens from the pathogens that they have engulfed and they display these antigens to the T lymphocytes in order to inform the adaptive immune response about what types of pathogens the monocytes have encountered when the monocytes leave the blood and enter into other tissues they differentiate into macrophages which are also cells that are specialized for phagocytosis and function as antigen presenting cells to communicate with the adaptive immunity thrombocytes which are also known as platelets are produced from a stem cell found in the red bone marrow that stem cell then can differentiate to form a megakaryoblast that further differentiates into a megakaryocyte and then cytoplasmic fragments break off from the megakaryocyte and enter into the blood as the platelets or thrombocytes the primary function of the platelets or thrombocytes is blood clotting to maintain the mechanism of hemostasis or to stop bleeding when a blood vessel is damaged platelets will stick to the damaged blood vessel wall and become activated releasing clotting factors that stimulate more platelets to stick together forming a platelet plug that blocks the end of the ruptured vessel in order to stop bleeding and maintain hemostasis