Blood

Chapter 12

Introduction

• What is the function of blood?

• Blood transports substances (nutrients, oxygen, wastes, and hormones)

• Also maintains homeostasis in the body with hormones

• Hematophobia = fear of blood

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Blood and Blood Cells

• Blood is a type of connective tissue with two basic components:– 1. Cells (red blood cells, white blood cells,

and platelets) = 45%

– 2. Plasma (water, amino acids, proteins, carbohydrates, lipids, vitamins, hormones, electrolytes, and cellular wastes) = 55%

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• Hematocrit – percentage of cells in a blood sample– Should be 45%, remaining 55% is plasma– Have to centrifuge a blood sample to test this

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Three types of cells

• Red blood cells - erythrocytes

• White blood cells - leukocytes

• Platelets - thrombocytes

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Red blood cells - erythrocytes

• Have a biconcave shape

• RBCC stand for red blood cell count which is the amount of blood cells in a cubic millimeter (5 million per cubic millimeter)

• They lack nuclei in a mature stage so they will not divide

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• Hematopoiesis – formation of new blood cells (done in bone marrow)

• Blood cells live for about 120 days, then are phagocytized by the liver and spleen

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• Erythropoietin – a hormone that is part of a negative feedback mechanisms that controls the rate of red blood cell formation– Produced in the liver and kidneys (controlled

by oxygen levels

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Main functions of Red blood cells

• Transports oxygen throughout body

and picks up carbon dioxide

• Hemoglobin - molecule which combines with oxygen to transport it within the blood

• Iron is critical to the creating of hemoglobin

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Oxygen levels in blood

• Oxyhemoglobin – blood has plenty of oxygen, appears bright red

• Deoxyhemoglobin – blood is not carrying much oxygen, appears "bluish red"

• Red blood cell production requires:– Iron– Vitamin B12– Folic Acid

• Anemia = too few red blood cells

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White blood cells – leukocytes

• General function - defend the body against disease-causing agents (microorganisms)

• Five different types in two groups:– 1. Granulocytes (granular cytoplasm):

Neutrophils, Eosinophils, Basophils

– 2. Agranulocytes (lacking granular cytoplasm): Monocytes, Lymphocytes

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1. Neutrophils

• Very active in phagocyting bacteria

• Are present in large amount in the pus of wounds

• Most common make up 60% of WBC

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2. Eosinophils

• Attack parasites

• Control allergic reaction

• 2% WBC

3. Basophils

• Produces Heparin (prevents blood clots) and Histamines (causes inflammatory reaction)

• Less then 1% WBC

4. Monocytes

• Precursors of macrophages

• Phagocytes

• Make up 6% of WBCs

5. Lymphocytes

• Main constituents of the immune system which is a defense against the attack of pathogenic micro-organisms such as viruses, bacteria, fungi and protista

• Yield antibodies and arrange them on their membrane

• Make up 30% of WBCs White blood cell interactive

Platelets – Thrombocytes

• Help initiate formation of blood clots,

• They close breaks in damaged blood vessels

http://www.ouhsc.edu/platelets/Platelet%20Pics/Platelets3.jpg

Blood Plasma

• The liquid portion of the blood– 92% water

– transports nutrients, gases, vitamins, maintains fluid and electrolyte balance, and pH

– Four types of proteins

in plasma

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Albumin

• Origin: Liver

• Function: Helps maintain osmotic pressure and blood volume (blood pressure)

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Alpha Globulin

• Origin: Liver

• Function: Transport lipids and fat – soluble vitamins

Beta Globulin

• Origin: Liver

• Function: Transport lipids and fat – soluble vitamins

Gamma Globulin

• Origin: Lymphatic tissue

• Function: Constitute a type of antibody for immunity

Fibrinogen

• Origin: Liver

• Function: Largest molecules of plasma proteins; important for blood clotting. Major event in blood clotting is the change of fibrogen into fibrin

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Hemostasis

• The process of stopping bleeding

• Coagulation causes the formation of a blood clot

• 3 Key Events

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1. Blood Vessel Spasm (vasoconstriction)

• Damaged or broken vessels stimulate muscle tissue in the walls of the blood vessels to contract

• This slows or stops blood flow, lasts for several minutes.

• Also, platelets release serotonin, a vasoconstrictor which maintains the muscle spasm even longer.

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2. Platelet plug formation

• Platelets stick to surfaces of damaged blood vessels and to each other to form a "plug"

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3. Blood coagulation

• Most effective, forms a blood clot (hematoma).

• Injury causes an increase in the release of coagulants.

• Main event - conversion of fibrinogen into long protein threads called fibrin.

• Tissue damage cause the prodction of prothrombin activator (calcium ions must be present)

• Prothrombin get converted to thrombin

• Thrombin acts as an enzyme to cause change of fibrinogen to fibrin, which traps platelets and blood cells to form a hematoma

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• Thrombus - a blood clot abnormally forming in a vessel

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• Embolus - when the clot moves and becomes lodged in another place

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Blood Groups and Transfusions

• Blood types are controlled by three alleles:– A, B, & O

• A & B are codominant; O is recessive

• This makes the genetics of blood very interesting

Antigens and Anitbodies

• Agglutination is the clumping of red blood cells following a transfusion reaction

• It is due to a reaction between red blood cell surface molecules called antigens and protein antibodies carried in plasma

• The type of antigens deternmines what blood type a person is

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Blood transfusions

• Blood that has antibodies on it that is not recognized by the body will be attacked by your immune system

• O is the Universal Donor because a person with this type of blood does not have antigens on the surface of the blood cells

• This will not cause an immune reaction in the patient.

• AB is the universal Acceptor because this person will not have an immune reaction to A, B, AB, or O

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Rh Blood group

• A person can either be Rh+ (have Rh surface antigens) or Rh- (do not have Rh surface antigens)– Positive is the dominant genotype

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• Problem: When a fetus is Rh+ and the mother is Rh-, this can cause the mother's immune system to attack the fetus.

• Called Erythroblastosis fetalis

• Doctors can prevent this reaction by giving the woman an injection that will suppress her immune reaction.

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