Blood, Components and Blood Cell Production

Blood, Components and Blood Cell Production Our blood is a fluid that is also a type of connective tissue. It is composed of blood cells and an aqueous fluid known as plasma. Two major functions of the blood include transporting substances to and from our cells and providing immunity and protection against infectious agents such as bacteria and viruses. Blood is a component of the cardiovascular system. It is circulated through the body via the heart and blood vessels. Blood Components Blood consists of several elements. The major components of blood include plasma, red blood cells, white blood cells, and platelets. Plasma: This major constituent of blood comprises about 55 percent of blood volume. It consists of water with several different substances dissolved within. Plasma contains salts, proteins, and blood cells. Plasma also transports nutrients, sugars, fats, hormones, gases, and waste material contained within blood.Red Blood Cells (erythrocytes): These cells determine blood type and are the most abundant cell type in the blood. Red blood cells have what is known as a biconcave shape. Both sides of the cells surface curve inward like the interior of a sphere. This flexible disc shape helps to increase the surface area-to-volume ratio of these extremely small cells. Red blood cells do not have a nucleus, but they do contain millions of hemoglobin molecules. These iron-containing proteins bind oxygen molecules obtained in the lungs and transport them to various parts of the body. After depositing oxygen to tissue and organ cells, red blood cells pick up carbon dioxide (CO2) for transportat ion to the lungs where the CO2 is expelled from the body. White Blood Cells (leukocytes): These cells play an important role in the immune system and lymphatic system by defending the body against infection. These cells locate, destroy, and remove pathogens and foreign matter from the body. There are several different types of white blood cells, each with different functions. Examples include lymphocytes, monocytes, neutrophils, basophils, and eosinophils.Platelets (thrombocytes): These cell components are formed from pieces of cells found in the bone marrow called megakaryocytes. Fragments of the megakaryocytes circulate through the bloodstream and play a major role in clotting. When platelets encounter an injured blood vessel, they clump together to block the opening in the vessel. Blood Cell Production Blood cells are produced by bone marrow within the bone. Bone marrow stem cells develop into red blood cells, white blood cells, and platelets. Certain white blood cells mature in the lymph nodes, spleen, and thymus gland. Matured blood cells have varying life spans. Red blood cells circulate for about 4 months, platelets for about 9 days, and white blood cells range from about a few hours to several days. Blood cell production is often regulated by body structures such as the lymph nodes, spleen, liver, and kidneys. When oxygen in tissues is low, the body responds by stimulating the bone marrow to produce more red blood cells. When the body is infected, more white blood cells are produced. Blood Pressure Blood pressure is the force at which blood exerts pressure against artery walls as it circulates throughout the body. Blood pressure readings measure systolic and diastolic pressures as the heart goes through the cardiac cycle. In the systole phase of the cardiac cycle, the heart ventricles contract (beat) and pump blood into the arteries. In the diastole phase, the ventricles are relaxed and the heart fills with blood. Blood pressure readings are measured in millimeters of mercury (mmHg) with the systolic number reported before the diastolic number.Blood pressure is not constant and can fluctuate depending on various conditions. Nervousness, excitement, and increased activity are a few things that can influence blood pressure. Blood pressure levels also increase as we get older. Abnormally high blood pressure, known as hypertension, can have serious consequences as it can lead to hardening of the arteries, kidney damage, and heart failure. Persons with elevated blood pressure often experience no symptoms. Elevated blood pressure that persists for the majority of the time can lead to increased risk for health issues. Blood Type Blood type describes how blood is classified. It is determined by the existence or lack thereof of certain identifiers (called antigens) located on red blood cells. Antigens help the bodys immune system to identify its own red blood cell group. This identification is crucial so that the body will not build up antibodies against its own red blood cells. The four blood type groupings are A, B, AB, and O. Type A has A antigens on red blood cell surfaces, type B has B antigens, type AB has both A and B antigens, and type O has no A or B antigens. Blood types must be compatible when considering blood transfusions. Those with type A must receive blood from either type A or type O donors. Those with type B from either type B or type O. Those with type O can receive blood from only type O donors and type AB may receive blood from any of the four blood type groups. Sources: Dean L. Blood Groups and Red Cell Antigens [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2005. Chapter 1, Blood and the cells it contains. Available from: (ncbi.nlm.nih.gov/books/NBK2263/)What Is High Blood Pressure? National Heart, Lung, and Blood Institute. Updated 08/02/12 (nhlbi.nih.gov/health/health-topics/topics/hbp/)

Express Quantity in English for Beginning Speakers

Express Quantity in English for Beginning Speakers There are many phrases used to express quantities and amounts in English. In general, much and many are the  standard quantifiers  used to express  large quantities. Which expression you use will often depend on whether the noun is countable or uncountable, and whether the sentence is negative or positive. While much and many are among the most common, the following expressions are often used in place of much and many, especially in positive sentences: A lot ofLots ofPlenty ofA great deal ofA large number of These expressions can are combined with of in the sense of most, many, or much. A lot of people enjoy listening to jazz. A great deal of time is spent understanding these issues. But note that much, most, and many do not take of. Most people enjoy listening to some type of music. Not: Most of  people... Much time is spent understanding math. Not: Much of time is spent ... Much Much is used with uncountable nouns: There is much interest in learning English around the world. How much money do you have? There isnt much butter left in the refrigerator. Much is used in negative sentences and questions, too: How much money do you have? There isnt much rice left. Note that much is rarely used in the positive form. English speakers generally use a lot of or lots of  with uncountable  nouns. We have a lot of time. Not: We have much time. There is a lot of wine in the bottle. Not: There is much wine in the bottle. Many Many is used with countable nouns: How many people came to the party? There arent many apples on the table. Note that many is used in the positive form, unlike much:   Andrew has a lot of friends / Andrew has many friends. A lot of my friends live in New York / Many of my friends live in New York. A Lot of / Lots of /  Plenty  Of A lot of and lots of can be used with both countable and uncountable nouns. A lot of and lots of are used in positive sentences: There is a lot of water in that jar. Hes got lots of friends in London. Note that generally speaking, lots of sounds less formal than a lot of.   A Little / A Few A little and a few  indicate a quantity or number. Use a little with uncountable nouns: There is a little wine in that bottle.   There is a little sugar in my coffee. Use a few with countable nouns. He has a few friends in New York. We bought a few sandwiches on our way to the park. Little / Few Little and few indicate a limited quantity. Use little with uncountable nouns: I have little money to spend. She found little time for work. Use few with countable nouns: He has few students in his class.   Jack finds few reasons to stay. Some Use some in positive sentences when there is neither a lot nor a little. Some can be used with both countable and uncountable nouns. We have some friends who work in Los Angeles.   Ive saved some money to spend on vacation this summer.   Any (Questions) Use any in questions to ask if someone has something. Any can be used with both countable and uncountable nouns: Do you have any friends in San Francisco? Is there any pasta left?   Note that when offering or requesting something use some instead of any  for polite questions. Would you like some shrimp? (offer) Would you lend me some money? (request) Any (Negative Sentences) Use any with countable and uncountable nouns in negative sentences to state that something doesnt exist. We wont have any time for shopping today. They didnt have any problems finding our house.   Enough Use enough  with countable and uncountable nouns to state that you are satisfied with the amount of something. She has enough time to visit her friends in Dallas. I think we have enough hamburgers for tomorrows grill.   Not Enough Use not enough when you are not satisfied with the amount of something. Im afraid theres not enough time to continue this conversation. There are not enough people working at the moment.   Each / Every Use each or every when referring to the individuals in a group. I think every person in this room would agree with me. Im sure each step of this process is important.   Large / Big / Vast / Huge Amount of Use these adjectives with amount of with uncountable and countable nouns to express large quantities. This form is often used to exaggerate just how much there is. There is a huge amount of work to be done to today. Tom has a vast amount of knowledge about the subject.   Tiny / Small / Minuscule Amount of   Use these similar adjectives with amount of to express very small quantities. This form is often used in exaggeration to express how little there is of something.   Peter has a small amount of patience, so dont joke around with him. There is a minuscule amount of time left to register. Hurry up!