Describe the important components and major functions of the blood
- plasma: About 55% of whole blood is blood plasma, a fluid that is the blood’s liquid medium, which by itself is straw-yellow in color. The blood plasma volume totals of 2.7-3.0 litres in an average human. It is essentially an aqueous solution containing 92% water, 8% blood plasma proteins, and trace amounts of other materials. Plasma circulates dissolved nutrients, such as, glucose, amino acids and fatty acids (dissolved in the blood or bound to plasma proteins), and removes waste products, such as, carbon dioxide, urea and lactic acid.
- red blood cells (erythrocytes): These contain hemoglobin, an iron-containing protein, which facilitates transportation of oxygen by reversibly binding to this respiratory gas and greatly increasing its solubility in blood.
- White blood cells: White blood cells are part of the immune system; they destroy and remove old or aberrant cells and cellular debris, as well as attack infectious agents (pathogens) and foreign substances
- Platelets: Platelets are responsible for blood clotting (coagulation). They change fibrinogen into fibrin. This fibrin creates a mesh onto which red blood cells collect and clot, which then stops more blood from leaving the body and also helps to prevent bacteria from entering the body.
•List the components of the cardiovascular system and explain the major functions of this system.
The four major functions of the cardiovascular system are:
- To transport nutrients, gases and waste products around the body
- To protect the body from infection and blood loss
- To help the body maintain a constant body temperature (‘thermoregulation’)
- To help maintain fluid balance within the body
List the characteristics and functions of red blood cells
Red blood cells lose their nucleus, rough endoplasmic reticulum, Golgi apparatus, and basically any membrane-bound organelles, simply so that there is more room for haemoglobin, which they are packed full of. They are in the shape of biconcave discs, to increase their surface area. All of these adaptations are so that they can transport oxygen and carbon dioxide to the tissues more efficiently.
Describe the structure of hemoglobin and indicate its functions.
A hemoglobin molecule consists of four polypeptide chains: two alpha chains, each with 141 amino acids and two beta chains, each with 146 amino acids. The protein portion of each of these chains is called “globin”. The a and b globin chains are very similar in structure. In this case, a and b refer to the two types of globin. Students often confuse this with the concept of a helix and b sheet secondary structures. But, in fact, both the a and b globin chains contain primarily a helix secondary structure with no b sheets.
Figure 2 is a close up view of one of the heme groups of the human a chain from dexoyhemoglobin. In this view, the iron is coordinated by a histidine side chain from amino acid 87 (shown in green.)
Each a or b globin chain folds into 8 a helical segments (A-H) which, in turn, fold to form globular tertiary structures that look roughly like sub-microscopic kidney beans. The folded helices form a pocket that holds the working part of each chain, the heme.
A heme group is a flat ring molecule containing carbon, nitrogen and hydrogen atoms, with a single Fe2+ ion at the center. Without the iron, the ring is called a porphyrin. In a heme molecule, the iron is held within the flat plane by four nitrogen ligands from the porphyrin ring. The iron ion makes a fifth bond to a histidine side chain from one of the helices that form the heme pocket. This fifth coordination bond is to histidine 87 in the human a chain and histidine 92 in the human b chain. Both histidine residues are part of the F helix in each globin chain.
Discuss red blood cell production and maturation.
Red blood cells are the most common type of blood cell and are the vertebrate body’s principal means of delivering oxygen from the lungs or gills to body tissues via the blood.
Red blood cells are also known as RBCs or erythrocytes (from Greek erythros for “red” and kytos for “hollow”, with cyte nowadays translated as “cell”). A schistocyte is a red blood cell undergoing fragmentation, or a fragmented part of a red blood cell.
The diameter of a typical human erythrocyte disk is 6–8 µm; they are thus much smaller than most other human cells. A typical erythrocyte contains about 270 million hemoglobin molecules, with each carrying four heme groups.
Adult humans have roughly 2–3 × 1013 red blood cells at any given time (women have about 4 million to 5 million erythrocytes per cubic millimeter (microliter) of blood and men about 5 million to 6 million; people living at high altitudes with low oxygen tension will have more). Red blood cells are thus much more common than the other blood particles: There are about 4,000–11,000 white blood cells and about 150,000–400,000 platelets in a cubic millimeter of human blood. The red blood cells store collectively about 3.5 grams of iron; that’s more than five times the iron stored by all the other tissues combined.
The process by which red blood cells are produced is called erythropoiesis. Erythrocytes are continuously being produced in the red bone marrow of large bones. (In the embryo, the liver is the main site of red blood cell production.) The production can be stimulated by the hormone erythropoietin (EPO), which is used for doping in sports. Erythrocytes develop in about 7 days and live a total of about 120 days. The aging cells swell up to a sphere-like shape and are engulfed by phagocytes, destroyed and their materials are released into the blood. The main sites of destruction are the liver and the spleen. The heme constituent of hemoglobin is eventually excreted as bilirubin.
Explain the importance of blood typing and the basis for ABO and Rh incompatibilities.
The A,B,O blood time is determined by the presence or absence of specific carbohydrates (referred to above as surface antigens) on the erythrocytes, or red blood cells that are recognized by the individuals immune system. For instance, let us say that Type A is characterized by circle carbohydrates and Type B is represented by triangles. The immune system of a type A patient would recognize the triangle antigens as foreign and therefore elicit an immune/inflammatory response. For this reason Type B blood is incompatible for a Type A patient.
Furthermore, AB blood has the presence of both surface antigens so there is no immune response upon transfusion of Type A, B, AB or O blood. O in turn is completely devoid of these surface antigens and is therefore the universal donor. The Rh factor is an additional category represented by + or -. O- is truly the universal donor when you take into account Rh factor
Categorize the various white blood cells on the basis of structure and function.
Leukocytes
•Have nuclei and other organelles
•Defend the body against pathogens
•Remove toxins, wastes, and abnormal or damaged cells
•Are capable of amoeboid movement (margination) and positive chemotaxis
•Some are capable of phagocytosis
- Granular leukocytes
- Neutrophils – 50 to 70 % total WBC population
- Eosinophils – phagocytes attracted to foreign compounds that have reacted with antibodies
- Basophils – migrate to damaged tissue and release histamine and heparin
- Agranular leukocytes
- Monocytes - become macrophage
- Lymphocytes – includes T cells, B cells, and NK cells
Describe the structure, function and production of platelets.
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•Describe the reaction sequences responsible for blood clotting.
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- List five major functions of blood.
The major functions of blood are transporting dissolved gases, nutrients, hormones, and metabolic wastes; regulating the pH and ion composition of interstitial fluids; restricting fluid losses at injury sites; defending against toxins and pathogens; and stabilizing body temperature.
- Identify the composition of the formed elements in blood.
Red blood cells, white blood cells, and platelets are the formed elements of blood.
- What two components make up whole blood?
Whole blood is composed of plasma and formed elements.
- Why is venipuncture a common technique for obtaining a blood sample?
Venipuncture is a common sampling technique because superficial veins are easy to locate, the walls of veins are thinner than those of arteries, and blood pressure in veins is relatively low, so the puncture would seals quickly.
- List the three major types of plasma proteins.
The three major types of plasma proteins are albumins, globulins, and fibrinogen.
- What would be the effects of a decrease in the amount of plasma proteins?
A decrease in the amount of plasma proteins in the blood would lower plasma osmotic pressure, reduce the ability to fight infection, and decrease the transport and binding of some ions, hormones, and other molecules.
- Which specific plasma protein would you expect to be elevated during a viral infection?
During a viral infection, you would expect the level of immunoglobulins (antibodies) in the blood to be elevated.
- Describe hemoglobin.
Hemoglobin is a protein composed of four globular subunits, each bound to a heme molecule, which gives red blood cells the ability to transport oxygen in the blood.
- How would the hematocrit change an individual suffered a significant blood loss?
After a significant loss of blood (especially of red blood cells), the hematocrit – the amount of formed elements (mostly red blood cells) as a percentage of the total blood – would be reduced.
- Dave develops a blockage in his renal arteries that restricts blood flow to the kidneys. What effect will this have on his hematocrit?
Dave’s hematocrit will increase, because reduced blood flow to the kidneys triggers the release of erythropoietin, which stimulates an increase in erythropoiesis (red blood cells formation).
- In what way would a disease that causes damage to the liver affect the level of bilirubin in the blood?
Bilirubin would accumulate in the blood, producing jaundice, because diseases that damage the liver, such as hepatitis or cirrhosis, impair the liver’s ability to excrete bilirubin in the bile.
- What is the function of surface antigens on RBCs?
Surface antigens on RBCs are glycolipids in the plasma membrane; they determine blood type.
- Which blood type can be safely transfused into a person with Type O blood?
Only Type O blood can be safely transfused into a person whose blood type is O.
- Why can’t a person with Type A blood safely receive blood from a person with Type B blood?
If a person with Type A blood receives a transfusion of Type B blood, which contains anti-A antibodies, the red blood cells will agglutinate (clump), potentially blocking blood flow to various organs and tissues.
- Identify the five types of white blood cells.
The five types of white blood cells are:
- neutrophils
- eosinophils
- basophils
- monocytes
- lymphocytes
