Understanding Blood

Veterinary Science

Mr. Pullom

OBJECTIVES

Instruction in this lesson should result in students achieving the following objectives:

1. Define blood and explain its major components.

2. Describe the role of blood in living organisms.

3. Explain how an organism maintains a supply of blood.

4. Identify the uses of blood analysis in animal production.

TERMS TO KNOW

• Anemia• Antibody• Bleeding• Blood• Blood analysis• Blood count• Blood poisoning• Blood transfusion• Blood typing

• Coagulation• Fibrin• Hemoglobin• Hormone• Marrow• Pathogen• Plasma• Platelets• Red blood cells• White blood cells

BEFORE STATEGY

Objective 1: Define blood and explain its major components.

I. Blood is the liquid in the circulatory system of an animal organism. Organisms cannot live without blood. All animals have blood, but its nature varies from one species to another. The amount of blood in an animal varies with the species and size of animal. A large animal has more blood than a small animal. An average adult human weighing 160 pounds (73 kg) has about 5 quarts (4.7 L) of blood. (Animals that live at high altitudes have more blood than those at lower altitudes. This is because air at higher altitudes has less oxygen. More blood is needed to meet the demands of the body for oxygen.)

A. Blood consists of four major components.1. Plasma is the liquid substance in which various solid materials are

suspended and moved about. Plasma is 90% water. The other 10% consists of dissolved substances including glucose, hormones, wastes, minerals, vitamins, and proteins. The plasma suspends and transports the solid blood materials. Plasma makes up 50–60% of blood by volume. Plasma has a straw color when the solid materials are removed.

2. Red blood cells (erythrocytes) are responsible for carrying oxygen from the lungs throughout the circulatory system. The oxygen is carried by a protein part of the blood known as hemoglobin. Red blood cells have a flexible membrane that allows them to squeeze through the very smallest blood vessel. Red blood cells do not repair themselves. New red blood cells are made in bone marrow. The dead red blood cells are removed by the spleen and liver. Scientists have found that one animal may possess a trillion blood cells.

3. White blood cells (leukocytes) are responsible for fighting disease and removing harmful substances from the body. Four different kinds of white blood cells are found in blood. Some white blood cells surround and digest infectious bacteria. Other white blood cells produce antibodies. An antibody is a kind of protein that destroys bacteria, viruses, and other substances that invade the body. Animals that are diseased produced increased numbers of white blood cells. The pus that forms in an infected wound is a large mass of white blood cells that has been fighting the infection.

4. Platelets (thrombocytes) are the structures in blood that are responsible for blood clotting. They are not complete cells and have a disk-like shape. In case of a wound, platelets stick to the edge of the skin and to each other to form a scab or cover that stops the flow of blood. Without platelets, an animal might bleed to death from a wound.

B. The organs in the circulatory system have an important role in assuring good blood circulation. Blockages interfere with body functions. The heart is the “pump” that sends blood out through the arteries and capillaries into the body. The blood returns in the veins. Circulation includes moving blood through the lungs by getting oxygen and giving off carbon dioxide, by the liver and spleen for cleaning, and throughout the entire body to support life processes.

http://www.youtube.com/watch?v=bzYmPQOKBL8

Objective 2: Describe the role of blood in living organisms.

II. Blood fulfills a number of functions that are essential to the well-being of an organism.

A. Blood must flow to all parts of the body to achieve these functions:1. Transport oxygen and carbon dioxide—Blood carries oxygen to all areas of

the body and acquires carbon dioxide from the respiration processes in the cells. Blood that is being sent out passes by the lungs to give off carbon dioxide and acquire oxygen. If an animal organism is cut, blood heavy with oxygen is bright red while that which has picked up carbon dioxide is reddish-brown.

2. Protects against disease—The white blood cells in blood help keep an organism

healthy and fight disease.3. Transport hormones—Blood carries substances known as hormones. A

hormone is a compound that produces a response within the body of an organism. Hormones are produced by endocrine glands and are secreted into the blood. Hormones regulate growth, metabolism, reproduction, and other functions of a living animal.

4. Transport nutrients and wastes—Blood carries nutrients from digested food. Blood that flows in the walls of the small intestine acquires nutrients as food molecules. As cells use the nutrients or grow and die, wastes are created. These wastes are transported by the blood to the liver for removal and excretion.

5. Heat regulation—Blood helps regulate the temperature in an organism. Activity by muscles in the body produces heat. The heat is picked up by the blood and distributed throughout the body. The skin may use some of the liquid in blood as sweat.

B. Proper circulation and good blood health are essential for these functions to be achieved. Any disruption causes the organism to suffer and possibly die.

Objective 3: Explain how an organism maintains a supply of blood.

III. The body of an organism must have adequate blood to function and be healthy.

A. The production of blood cells and materials is regulated by hematopoietic growth factors. These involve complex processes that occur in the body. In general, three processes are involved in maintaining a supply of blood.

1. Regulation of amount—The amount of blood and proportions of materials in blood is continuously being adjusted to meet the demands of the body. For example, an animal that is diseased will produce increased white blood cells.

2. Replacing worn cells—Damaged and worn cells and platelets must be replaced. Blood cells and platelets are produced in bone marrow. Marrow is the soft substance in the middle of bones. Marrow may be red or yellow. Different processes are used to make red and white cells and platelets. All begin as similar cells but develop differently depending on needs of the body.

3. Controlling bleeding—Bleeding is the loss of blood due to injury or disease. Bleeding may be on the skin due to a scratch or cut, or bleeding may be internal due to injury or disease of the organs or tissues. Blood plasma contains clotting (coagulation) factors. These cause the blood to coagulate. Coagulation is a complex process. It is initiated by injured tissues giving off signals indicating that bleeding is occurring. The clotting factors result in the formation of sticky strands known as fibrin. The fibrin crisscross each other creating a blockage that stops the loss of blood from the wound. Blood also contains substances that dissolve clots. Occasionally a clot will occur where it is not needed, such as in an artery. The clot disrupts blood flow and can result in disease and death, especially if the clot results in a heart attack or stroke.

B. Organisms that lose blood in an accident or medical procedure may be given blood that has been taken from another animal with the same blood type. This process is known as a blood transfusion. It is more common in humans than in domesticated animals. Transfusions can transmit disease from on organism to another. Blood transfusions should only be done by trained individuals.

http://www.youtube.com/watch?v=--bZUeb83uU

Objective 4: Identify the uses of blood analysis in animal production

IV. Blood analysis is the process of testing blood to determine its characteristics. Samples are collected and tested to determine various attributes.

A. Blood typing is a kind of analysis that is used in genetics studies. Genetic markers in the blood can be used to determine the parents of offspring. For example, the identity of the sire of a calf can be determined by blood typing a calf. Newer DNA analysis procedures may be replacing some uses of blood typing.

B. Blood count is a type of analysis that determines the number of red and white cells and hemoglobin in blood. Microscopes are used to visually determine the number of each cell using a grid slide. Only a drop is needed for a blood count. A substance is added to the blood to prevent coagulation so that it will “flow” over the slide. Visual counts are made when viewed through the microscope.

C. Blood analysis is primarily used in determining the health condition of an animal.

1. Blood analysis may be used to determine the nutritional adequacy of an animal’s diet. Samples of blood are taken and examined. For example, the size of the red blood cells of an animal indicates adequacy of nutrition. A deficiency of iron results in smaller than normal red blood cells. This condition caused by inadequate iron is known as anemia.

2. Blood analysis may be used to determine the presence of pathogens. A pathogen is a microscopic organism that causes disease. Bacteria and viruses are common pathogens. Analysis also indicates the proportions of red and white blood cells. Higher amounts of white cells indicate that the body is fighting an infection. Blood poisoning is a condition in the blood caused by the presence of bacteria or fungi that cause disease. The microorganisms enter the blood through an infection or wound. Good sanitation helps prevent blood poisoning in case of an injury.

3. Other diseases can be determined with blood analysis. For example, too few white cells in blood is a sign of a disease in bone marrow. A very high white blood cell count is a sign of leukemia in humans.

QUESTIONS???

ASSIGNMENTS

• Word Search

• Crossword

• Reading Comprehension