BloodChapter 15

Hematology:Study of Blood

Functions:

Transports: moves many substances around the body

Ex. Oxygen is delivered from lungs to cells of the body

Ex. picks up waste material from the cells and delivers it to organs that can eliminate it from the body

Ex. nutrients, ions, hormones, etc. use blood as the vehicle for movement through the body

Regulation: blood helps to regulates fluid and elctrolyte balance, acid-base balance, and body temperature.

Protects: helps protect the body from infection and excessive blood loss.

Composition of Blood

Blood is a type of connective tissue - has liquid intracellular matrix (plasma)

Color of blood varies from bright red to darker red-blue - depends on the amount of oxygen in the blood

Average adult has 4-6 Liters of blood – varies with age, gender, and body size

Ph = (7.35-7.45)

Viscosity = ease at which blood flows through vessels - compare water to honey... honey is more viscous, thicker than water

2 Parts to bloodPlasma - pale yellow fluid composed mostly of water

Ions, Nutrients, Gases, Waste

Plasma Proteins - albumin, various clotting factors, antibodies, and compliment proteins

- help regulate fluid volume, protect the body from pathogens, prevent excessive blood loss

• Serum - is the plasma without the clotting proteins

Blood Cells - include:

RBC (red blood cells), erythrocytes - transport of oxygen to all body tissues

WBC (white blood cells), leukocytes - protect body from infection

Platelets (thrombocytes) - protect body from bleeding

Origin of Blood cells

Hematopoiesis - blood cell production

Hematopoeiten secreted by kidneys

Hematopoietic tissues:

Red Bone Marrow - ends of the long bones (femur)

- flat and irregular bones (sternum, cranial bones, vertebrae, pelvis)

Lymphatic tissue (spleen, lymph nodes, thymus gland)

Bone marrowHematopoiesis

3 different types of cell from Bone Marrow?

From the same cell? .... Stem Cell !!

Stem cells are influenced by specific growth factors which differentiates the cell into RBC’s, WBC’S and platelets

Bone MarrowBone Marrow Depression (myelosuppression) leads to...

Aplastic anemia - form of anemia- severe deficiency of red blood cells, erthrocytes

Leukopenia - deficiency of leukocytes (WBC) increase in susceptibility to infection

Thrombocytopenia - deficiency in platelets increases risk for hemorrhage

Many drugs and procedures (chemotherapy, radiation) depress the bone marrow and must be carefully monitored for symptoms of myelosuppression (reverse isolation)

Bone Marrow Overactivity

Polycythemia - overactive, excessive production of RBC’s - blood becomes more viscous and burdens the heart, overwhelms the clotting system - pt usually has a beet-red, ruddy face. Tx may be medication to depress the bone marrow or phlebotomy to remove excess blood

RBC’s, (Red Blood Cell), Erythrocytes... most abundant (4.5-6 million in 1 microliter of blood) Rate of production = several million per second

Primary concern is to transport oxygen

Reticulocytes are immature RBC’s...

usually very low, small amount in blood

Reticulocyte tests are done to evaluate changes in blood - may indicate blood loss, iron deficiencies - valuable diagnostic clues

Loss of blood stimulates bone marrow to make more RBC’s...there will be a greater number of reticulocytes circulating in blood = high retic count!

Low retic count could indicate bone marrow inability to make RBC’s such as in myelosuppression or iron deficiency.

Blood Cells:Red Blood cells

RBC’s -shape

Large enough to stay within the vessel walls

Disc-shaped, thick outer rim and thin center...can bend and squeeze through tiny vessels to deliver oxygen to every cell in the body

Sickle-cell disease - altered shape, limiting the RBC’s ability to move freely. C-shaped (sickle-shaped) RBC blocks blood flow through the smaller vessels - depriving tissue cells of oxygen.

RBC’s: Hemoglobin

RBC’s are filled with a large protein molecule called...

Hemoglobin heme= iron containing substance, globin= protein

responsible for the function of the RBC

RBC’s circulate through the blood vessels of the lungs...where oxygen molecules attach loosely to the iron atom in the heme...Oxyhemoglobin

Oxygen molecule detaches from the hemoglobin as it circulates through the body...O2 diffuses to the cells where it is used for cell metabolism

CO2 attaches to the globin (Carboxyhemoglobin) at the site of production (cell metabolism) and brought to the lungs to be excreted

Hemaglobin Facts:

• When hemoglobin is oxygenated...blood appears bright red

• When hemoglobin in un-oxygenated...blood appears darker blue-red...causing skin to look blue... cyanosis, a sign of hypoxemia

• Essential substances for hemoglobin production:

• Healthy bone marrow, iron, vit B12, folic acid, and protein

• iron deficiency anemia - diet low in iron

• folic acid deficiency anemia - diet low in folic acid

• pernicious anemia - inadequate absorption of vit B12

Regulation of RBC production:

• RBC’s are constantly added to the circulation

• Old, worn-out RBC’s are constantly being removed, dismantled and recycled

• Steps for RBC production:

• When the oxygen n the body tissues starts to decrease, the kidneys sense the need for additional oxygen...secrete a hormone called erythropoietin

• Erythropoietin stimulates the boen marrow to release RBC’s into the circulation

• The increase in the number of RBC’s...causes an increase in the amount of oxygen transported to the tissues

• As the tissue oxygenation increases...the stimulus for erythropoietin release diminishes...bone marrow slows production rate of RBC’s

Clinical Pearls about EPO:

• Chronically ill, hypoxic patients...emphysema? Low oxygen in the blood stimulates the secretion of excess EPO (erythropoietin)...excess RBC production causing polycythemia

• Patients with bone marrow depression may be given EPO as a drug to increase RBC production

• Athletes use EPO to increase RBC production trying to increase the amount of oxygen delivered to exercising muscles

• Patients with declining kidney function do not produce enough EPO...become anemic and are treated with EPO

Removal, Breakdown and Recycling the RBC

• Life span of RBC is 120 days, becomes ragged and worn out

• Ragged RBC membrane is detected by the macrophages that line the spleen and liver - the macrophages (big eaters) remove the RBC form the circulation - phagocytosis

• hemolytic anemia - when the RBC breakdown is quick, hemolysis, and exceeds the rate of production

White Blood Cells• White blood cell, WBC, leukocyte

• Large, round, contain nuclei

• Less numerous, (5,000-10,000) WBC’s per 1 microliter of blood

• Functions to protect the body by destroying disease-producing microorganisms (pathogens) and remove dead tissue, cellular debris - Phagocytosis

• Leukocytosis - when there is an increase in the number of WBC when an infection is present

• WBC’s can leave the blood vessels by squeezing through the cells of the blood vessel walls - to move toward the site of infection

Kinds of WBC’s:Granulocytes & Agranuocytes

• Classified according to presence of granules in the cytoplasm - Granulocytes and Agranulocytes (w/o granules)

Granulocytes:• Neutrophils most common

• Role is phagocytosis - cells move quickly to site of infection - phagocytose pathogen, remove tissue debris

• Pus - sometimes they leave behind a collection of dead neutrophils, parts of cells, and fluid

• Abscess - body can create a wall around the collection of pus to protect surrounding tissue and spread of infection

• Neutropenia (granulocytopenia)- deficiency of neutrophils leaving a person very susceptible to infection - common cold can be life-threatening

• Basophils normally present in small numbers

• Role is in the inflammatory response - releases histamine

• Releases Heparin, anti-coagulant - because Basophils are found mostly in areas that have an abundance of blood - the release of heparin reduces formation of tiny blood clots

• Eosinophils normally present in small numbers

• Role is in the inflammatory response - secretes chemicals that destroy certain parasites, engages in phagocytosis

• Elevated in patients with an allergic reaction or parasitic infection

Agranulocytes:Lymphocytes & Monocytes

• Lymphocytes - produced in red bone marrow; some mature and reproduce in the lymphoid tissue (lymph nodes, spleen, liver)

• Important role in the bodys immune system

• Monocytes -

• phagocytic... although less abundant than lymphocytes, they are much more effecient phagocytes

• Macrophages - monocytes differentiate (change) into macrophages - wandering or fixed?

• Wandering macrophages - travel around the body patrolling for pathogens and clean up debris

• most abundant under mucous membranes and the skin

• Fixed macrophages - present in a particular organ (liver, spleen, lymph nodes, red bone marrow)

• as blood or lymph flows through these organs, the fixed macrophages phagocytose any pathogens

• phagocytose old RBC’s - removing them from circulation

Monkey Business for WBC’s

• Naughty Neutrophils

• Little Lymphocytes

• Monke Monocytes

• Eat Eosinophils

• Bananas Basophils

• says

• GRAN Granulocytes

• BEN Basophils, Eosinophils, Neutrophils

Platelets

• Thrombocytes = platelets

• Smallest blood cell

• life span of 5-9 days

• produced in the red bone marrow

• 150,000-450,000 platelets per 1 microliter of blood

• prevents blood loss, plays a fundamental role in hemostasis (blood clotting)

• Thrombocytopenia - deficiency in platelets, characterized by tiny red hemorrhagic spots on the skin (petechiae) and an abnormal, potentially fatal bleeding episodes

• Thrombosis- when the number of platelets are too high and blood clots form -potentially obstructing blood flow to the head, heart, lungs, extremities

CBCComplete Blood Count

• Lab test that provides information about the composition of the blood

• provides normal range of expected blood cells

Hemostasis:Prevention of blood loss

• Hemostasis - process that stops bleeding after injury to a blood vessel

• 3 steps to hemostasis

• Blood vessel spasm - when a blood vessel is injured, the smooth muscle in he blood vessel responds by contracting (vascular spasm).

• Vascular spasm causes the diameter of the blood vessel to decrease - decreasing the amount of blood that flows through - successful with tiny vessels - additional support needed wth larger vessels

• Formation of platelet plug when blood vessel is torn, he inner lining of the vessel activates the platelets - they become sticky and adhere to the inner lining of the injured vessel and each other forming a platelet plug

• Platelets also release chemicals that stimulate vascular spasm and help ctivte the blood-clotting factors

• Blood clotting - third stage !!

Blood Clotting• Coagulation (blood clotting) a series of chemical reactions that

result in the formation of a netlike structure. The net is composed of fibrin - protein fibers

• Blood Clot - blood flows through the fibrin net, large particles (RBC’s, platelets) get trapped forming a structure that seals off the opening in the injured vessel and stops the bleeding

• Formation of a blood clot:

• Stage I - injury activates various clotting factors which produce prothrombin activator (PTA)

• Stage II - thrombin is formed from prothrombin in presence of calcium, platelet chemicals and PTA

• Stage III - thrombin activates fibrinogen which helps form fibrin fibers

Anticoagulants• 2 major mechanisms that prevent blood clot formation

• Endothelium - smooth inner lining of blood vessels allows blood to flow easily along its surface

• Secretion of Heparin - mast cells (basophils) which are located in areas where blood is stagnant (apt to clot) - areas in and around the lungs/liver - cells secrete heparin

• Heparin - acts an anti-coagulant by removing thrombin from he clotting process

• Thrombus - blood clot

• Thrombosis - process of clot formation

• Embolus - piece of the thrombus that breaks away and travels through the blood

• Administration of medications - anticoagulants such as coumadin or heparin

• Fibrinolysis - dissolving of the clot after task complete - plasmin dissolves the clot

• Plasminogen - inactive circulating form of plasmin - gets activated by tissue plasminogen activator (TPA) which is formed by injured tissue

• TPA - has been administered as a drug to dissolve clots

Blood Types:• Blood is classified by specific antigens on the surface of an RBC

• Antigen - is a substance that body recognizes as foreign. An antigen stimulates an antigen-antibody response - attacks and destroys the substance. Genetically determined

• ABO Grouping - refers to the antigen on the RBC

• Four Blood types: A, B, AB, O

• Ex. Type A blood has an A antigen

• Type B blood has a B antigen

• Type AB blood has both A and B antigens

• Type O blood has neither A or B antigen

• Antibodies

• bind with specific substances and inactivate them

• found in the plasma of each blood type

• Ex. A blood type has antibodies to B type blood

• B blood type has antibodies to A type blood

• AB type blood has neither A nor B antibodies

• O type blood has antibodies to both A and B antigens

Antigen - Antibody Reaction

• What happens when the Anti - A antigen is exposed to A type blood?

• Agglutination - the anti-A antigen would clump with the A antibodies causing hemolysis - possibly death.

• That is why we check Blood type and Compatibility.

• Compatible blood groups are able to mixed together without agglutination

• Incompatible blood groups agglutinate when exposed to each other

• Crossmatch - is when a sample of the donor blood is mixed with the recipients blood - any evidence of agglutination deems the donor blood to be incompatible.

• Universal Donor - O type blood

• Universal Recipient - AB type blood

Rh Classification• Blood is also classified according to the Rh Factor

• Rh Factor is an antigen located on the surface of the RBC - if the RBC contains the Rh factor - it is said to be Rh positive (+) - if the RBC does not have the antigen on the membrane it is said to be Rh negative (-)

• Plasma does not usually carry anti-Rh antibodies, however in 2 conditions a person can develop ant-Rh antibodies in the plasma allowing agglutination and hemolysis to occur if exposed again.

• Administration of Rh positive blood to a Rh negative person.

• Initial transfusion is without incident, however, the Rh antigen of the donor stimulates the recipient to produce anti-Rh antibodies - the person has now become sensitized - If the Rh(-) person receives a second transfusion of Rh(+) blood the anti-Rh antibodies will attack the Rh antigen

• Pregnancy - If an Rh(-) mother is carrying a Rh (+) baby - the first pregnancy is uneventful, it is the second pregnancy that potentially could be fatal. The mother has been sensitized during her first pregnancy.

• Rhogam - is a drug given to the mother during pregnancy and within 72 hours after delivery. Rhogam surrounds the baby’s Rh (+) antgens - thereby preventing them from stimulating the development of anti-Rh antibodies in the mother.

Disorders of the Blood

• Anemia -

• Ecchymosis -

• Hemophilia -

• Leukemia

• Polycythemia