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Hematology


Unit Overview: In this section you will learn that the average person has about five liters of blood in their body. Also you will read about how fibrin is a component that helps with the clotting of the blood. You will also read about the differences between WBC and RBC, For example each WBC contains a nucleus but a RBC needs to lose its nucleus in order to become a mature RBC.




1. Functions and Components of the Circulatory System.





Blood serves numerous functions by traveling through the body in a system of vessels leading from and returning to the heart.
Blood can also transport disease-causing viruses, bacteria, and their toxins. Protective mechanisms in the circulatory system guard against this.
Functions of the Circulatory System:
  • Transportation - any substance that is essential for cellular metabolism is transported by circulatory system
A. Respiratory - erythrocytes transport oxygen into the cells
B. Nutritive - the digestive system is responsible for the mechanical and chemical breakdown of food
C. Excretory - blood carries metabolic wastes and other molecules not needed by the body to the kidneys and excreted in urine
  • Regulation - circulatory system contributes to hormonal and temperature regulation
A. Hormonal - hormones are carried by blood from their original site to target tissues where they perform a variety of regulatory functions
B. Temperature - regulation is aided by the diversion of blood from deeper to more superficial vessels
  • Protection - circulatory system protects against blood loss from injury and against pathogens
A. Clotting - protects against blood loss when vessels are damaged
B. Immune - performed by leukocytes that protect against many disease-causing agents

Major Components of the Circulatory System:
  • Cardiovascular System
A. Heart - four-chambered double pump; the pumping action creates pressure needed to push blood through vessels to the lungs and body cells
B. Blood Vessels - tubular network that permits blood to flow from the heart to all living cells of the body and then back to the heart; arteries carry blood away from the heart and veins return blood to the heart
  • Lymphatic System
A. Lymphatic Vessels - in connective tissues around the blood vessels; fluid in these vessels is called lymph; lymph nodes cleanse the lymph prior to its return to the venuous blood
B. Lymphoid Tissue (within the spleen, thymus, tonsils, and lymph nodes)


2. Composition of the blood - Plasma, the formed elements of blood, hematopoiesis






Your body has around five liters of blood taking up around eight percent of your total body weight. The blood coming to your heart is called venous blood, and the blood going from your heart is called arterial blood. Venous blood is a darker red then arterial blood because it contains less oxygen.
Plasma makes up about fifty-five percent of the total blood volume, containing water and dissolved solutes. Seven to nine percent of the plasma is made up of the plasma proteins. Albumins, although they are the smallest of the plasma proteins, play a major role in maintaining blood volume pressure by drawing water into the capillaries by nearby tissues. They make up sixty to eighty percent of the plasma proteins. If you start losing too much water your hypothalamus gives you the sensation of thirst. It also releases a antidiuretic hormone that goes and works with the kidneys to help with increased intake of fluids.
Red blood cells (RBC's) are made through a process called hematopoiesis. It is believed that hematopoiesis tissue makes about five hundred billion cells every day. The hematopoiesis stem cells are self-renewing. Erythropoiesis has to do with the formation of red blood cells and leukopoiesis has to do with the formation of white blood cells. Since the liver and spleen keep destroying the red blood cells, so it is said that about two point five billion red blood cells are made every second. There is a chemical known as cytokines that regulates the making of the different types of white blood cells. When your blood level gets to low, erythroprotien is secreted by the kidneys to help speed up the formation of red blood cells. With red blood cells to become mature it takes about three days for the whole process to work and for them to lose their nuclei.

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" GENERAL COMPOSITION OF BLOOD "

There are two types of blood cells that are in the formed elements of blood. They are red blood cells (erythrocytes) and white blood cells (leukocytes). Red blood cells look like flatted, biconcave disks that contain about two hundred eighty million hemoglobin molecules to give blood its color. Red blood cells only last up to one hundred and twenty days because they don't contain a nuclei or mitochondria. They are removed by phagocytic cells found in the bone marrow, liver, and spleen.
Platelets also called thrombocytes, are the smallest elements. They also don't contain a nuclei like red blood cells, but like white blood cells can move to other places other than having stay in the blood vessels. They have a life span of about five to nine days before the liver and spleen kill them. Platelets play a major role in blood clotting. They attach together and release serotonin that constricts the blood vessels, slowing down the blood flow to that spot, while phospholipids enter the platelets cell membrane and enforce fibrin to help the platelets make a stronger less movable clot.

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White blood cells are very different from red blood cells. First they contain a nuclei and mitochondria. They have the ability to get to infections by squeezing their way through the pores in the capillary walls, while red blood cells can't leave the blood vessels. Since white blood cells are very hard to see under a microscope unless they are stained, are named by how they stain. Eosinophils are pink, Basophils are blue, Neutrophils are similar to both pink and blue. Neutrophils are the most abundant white blood cell making up fifty to seventy percent. There are two types of agranular leukocytes. They are called lymphocytes and monocytes.
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Active Neutrophils
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Lymphocyte












3. Composition of the blood part 2- red blood cell antigens and blood typing, Blood clotting, Dissolution of clots.

Red Blood Cell Antigens and Blood Typing

Antigens- are part of certain molecules on the surface of all cells in our body. They can be recognized by the immune system and can stimulate a response in the body to create antibodies which can attach to the antigens.

The major blood typing groups are the ABO system and the Rh system.

ABO system
Everyone inherits 2 genes that control the production of the ABO antigens 1 gene from each parent. Your blood type refers to the kind of antigens found on the surface of the red blood cells.


ABO_system.jpg
When different types of blood are mixed, antibodies against the red blood cell antigens cause the red blood cells to agglutinate or clump together (not clot).


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Agglutination Reaction


agglutination.jpg
Blood type. Agglutination of RBC happens when antigens of different blood types are mixed together. If no agglutination occurs then it is type O blood. (not shown)


When receiving type O blood this is considered the universal donor because it lacks A and B antigens, the recipient's antibodies can't attach to the donor RBC antigens. However, type O blood which has a large volume of plasma, could cause agglutination in all other blood types, because the plasma has Anti-A and Anti-B antibodies.

Type AB blood is considered the universal recipient because it lacks Anti-A and Anti-B antibodies and can't agglutinate with donor RBC's. But just like type O blood plasma in large volumes can cause agglutination in the blood.

Rh Factor

The other group of antigens found in RBC's is the Rh Factor. The Rh antigen that is used most often is the D antigen or Rho(D). If this Rh antigen is found on a person's RBC's they are Rh positive, if not then they are Rh negative. Rh+ doesn't make antibodies against antigens, but Rh- does. Rh+ is the more common condition then Rh-. This process is very important during pregnancy. The Rh Factor can cause problems when an Rh- Mother has Rh+ babies. During birth the mother can be exposed to Rh+ blood from the fetus. So when the mother gets pregnant again she will produce Rh antibodies. Erythroblastosis fetalis- happens when Rh antibodies from the mother cross the placenta and combines with Rh+ antigens on the fetal blood cells causing hemolysis of the fetal RBC's. This can cause many health issues and even can cause a still born baby. There are medications out now that can prevent this condition to happen.

Blood Clotting

When a blood vessel is damaged, platelets adhere to the exposed subendothelial collagen proteins.





blood_clotting.jpg
"Blood Clotting" the purple cells are platelets.
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Platelet Release Reaction- Platelets that stick to collagen undergo a release reaction, in which they secrete ADP, serotonin, and thromboxane A2. Serotonin and thromboxane A2 cause vasoconstriction. ADP and thromboxane A2 attract other platelets and make them stick to the growing mass of platelets that are stuck to the collagen in the broken vessel this process is called a platelet plug. Shown in the picture above.

Quick note: Aspirin can reduce the Platelet Release Reaction process. Taking excessive amounts of aspirin can cause bleeding because it prevents platelets from clotting and forming a platelet plug.

Clotting Factors: Formation of Fibrin

In the formation of a blood clot, a soluble protein called fibrinogen is converted into insoluble threads of fibrin. This reaction is catalyzed by the enzyme thrombin.
Thrombin is derived from prothrombin, its inactive precursors, by either an intrinsic or an extrinsic pathway.

the_clotting_pathway.jpg
The intrinsic pathway, which is the longer of the two, requires the activation of more clotting factors. The shorter extrinsic pathway is initiated by the secretion of tissue thromboplastin when there is damage outside blood vessels. The clotting sequence requires Ca2+ as a co-factor and phospholipids present in the platelet cell membranes. Ca2+ and phospholipids convert Prothrombin into Thrombin as stated above. Thrombin converts Fibrinogen to fibrin which polymerizes to form a mesh. As stated above the mesh then traps platelets and RBC's to create a plug until the damage is repaired in the vessels.


The_Plasma_Clotting_Factors.jpg



Dissolution of the clot eventually occurs when the vessel damage is repaired. Activated factor XII causes the activation of kallikrein which converts plasminogen into plasmin. Plasmin then digests the fibrin and dissolves the clot.

Anticoagulants
Clotting can be prevented by Ca2+ chelators (Sodium citrate or ethylenediamineteraacetic acid "EDTA") or heparin which activates antithrombin III which blocks thrombin. Coumarin blocks clotting by inhibiting activation of vitamin K which works indirectly by reducing Ca2+ availability to promote clotting.


Essential Questions:

-Create a chart that shows the antigens and antibodies of the ABO+/- blood typing system. Also include on your chart, which blood types are compatible.

Antigen & Antibody
BLOOD GROUP
ANTIGEN
ANTIBODY
A
A
anti-B
B
B
anti-A
AB
A and B
neither
O
neither anti-A or anti-B
anti-A,B

Blood Compatibility Rh Factor
x means compatible
Recipient
Donor
O-
O+
B-
B+
A-
A+
AB-
AB+

AB+
X
X
X
X
X
X
X
X
AB-
X

X

X

X

A+
X
X


X
X


A-
X



X



B+
X
X
X
X




B-
X

X





O+
X
X






O-
X









-Describe what happens on the molecular level when blood types are not compatible.
The blood will start to clump together resulting in blockage or exploding red blood cells which will lead to problems with organs, such as the kidney. This is life threatening.
-What blood type is considered the universal donor and why?
Type O is the universal donor because it doesn't contain either A or B antigens.
-What blood type is considered the universal recipient and why?
Type AB is the universal recipient because they don't contain anti A or B antibodies.

How does this apply to PTA?

This pertains to our field because if a patient doesn't exercise their total blood volume decreases. So if they are in bed or in a chair and gets up too fast, they can become dizzy because their blood volume is low do to the fact that they haven't be exercising. The patient might try to get out of exercising because they get dizzy, instead of stopping the Therapist would allow the patient to rest for a minute or two then get them walking to bring their blood levels up. When you don't exercise you loose the amount of blood in your body. To help resolve this issue you can start by just walking every day or doing some form of exercise for at least 30 minutes preferably everyday or at least 5 days a week. This will not only improve your circulation but also bring your blood volume up as well because the body is in demand for more blood in the system.





1.http://www.google.com/images?hl=en&source=imghp&biw=1362&bih=583&q=Neutophils&gbv=2&aq=f&aqi=g-s1g-sx7g-msx2&aql=&oq=
2.http://www.google.com/images?hl=en&source=imghp&biw=1362&bih=583&q=lymphocytes&gbv=2&aq=f&aqi=g9g-m1&aql=&oq=
3.http://www.google.com/images?hl=en&biw=1362&bih=583&gbv=2&tbs=isch%3A1&sa=1&q=erythrocytes&aq=f&aqi=g9g-m1&aql=&oq=
4.http://highered.mcgraw-hill.com/sites/0073378119/student_view0/chapter13/textbook_images.html
5.Fox, Stuart I. "Human Physiology." New York: McGraw-Hill, 2011. Print.
6. Thrombus picture http://kska.org/wp-content/uploads/2008/08/blood-clot1.jpg
7. http://www.getbodysmart.com/ap/circulatorysystem/blood/overview/composition/tutorial.html
8. http://www.simscience.org/membranes/advanced/essay/blood_comp_and_func1.html
9. http://www.youtube.com/watch?v=PgI80Ue-AMo