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Blood

Connective tissue composed of cells and ECM• Cells- erythrocytes, leukocytes, thorombocytes• ECM- (Plasma)--water, lytes, proteins, hormones, etc..

– Cells in the body are surrounded by ECF---interstitial fluid and blood (20% of ECF)

• Body depends on the blood for:– Transportation- oxygen, carbon dioxide, nutrients, wastes,

hormones– Regulation-buffers, temperature, – Protection- immunity, coagulation

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Blood characteristics:

• Viscous due to cellular component• Temperature 100.4F• pH- 7.35-7.45• Volume: males- 5-6 L; females- 4-5 L

• Blood volume and therefore blood pressure is regulated via several hormones

• Which do you know?• New one—ANP

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Hematocrit

• Separation of cellular and ECM in blood using centrifuge

• 45% cells; 55% plasma – Females: 38-46% average 42%– Males: 40-54% average 47%

• Testosterone increases EPO production

• 99% of cells are erythrocytes• Buffy coat represents WBC and

thrombocytes• Anemias- see decreased erythrocytes• Polycythemias- see increased

erythrocytes• When? Problems?

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Blood components

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Blood Components

Formed elements: erythrocytes, leukocytes, thrombocytes

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Blood Components

Plasma:• 0ver 91.5% water• 7% plasma proteins

• created in liver• confined to bloodstream

– Albumin- small protein• maintains blood osmotic pressure

– globulins (immunoglobulins)• antibodies bind to foreign antigens• form antigen-antibody complexes

– fibrinogen

• 1.5% other substances – electrolytes, nutrients, hormones, gases, waste products

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Blood Cell Formation:

Hemopoiesis/ematopoiesis:

• Most blood cells continually replaced– die within hours, days or weeks

• In the embryo– Hemopoiesis--yolk sac, then liver, spleen, thymus, lymph nodes,

then prior to birth-- red bone marrow

• In adult– red marrow of flat bones like sternum, ribs, skull & pelvis and

ends of long bones—proximal epiphyses of humerus and femur

Hemopoiesis Animation:

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• Red blood cells ( erythrocytes )• White blood cells ( leukocytes )• Platelets (special cell fragments)

Cells enter sinusoidal capillaries entering bloodstream

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• Bone marrow biopsy/bone marrow aspiration• Iliac crest or sternum• View hematopoiesis---post chemotherapy• Aplastic anemia?

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Hemopoietic Growth Factors

Erythropoietin (EPO)• Hormone produced at peritubular interstitial cells in the kidney;

detect hypoxia• Stimulate erythropoiesis

– More EPO in males---testosterone

Thrombopoietin• Produced at liver; stimulates production of thrombocytes

Cytokines• produced at bone marrow, macrophages, other leukocytes,

endothelial cells, stimulate progenitor cells• Include CSF and interleukins

Post chemotherapy-EPO and CSF-G (granulocyte) and granulocyte- macrophage colony-stimulating factor; also given to those with renal dz.

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Erythrocytes

• Biconcave, anucleated cells—lose nucleus during development; large surface area due to lack of nucleus

• Lack mitochondria; anaerobic respiration for ATP production

• Flexible, 8 microns in diameter; able to bend in small blood vessels (capillaries)

• Contain hemoglobin (33% of cell weight)— carry oxygen molecules– Males- 5.4 million cells/micro liter of blood– Females- 4.8 million cells/micro liter of blood

• Each second 2 million enter the circulatory system

• Blood type depends on surface antigens (glycoproteins) on erythrocyte cell surface

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Hemoglobin• Primary function-- transportation of oxygen

– 280 million molecules of hemoglobin/erythrocyte

• Hemoglobin consists of four peptide chains– Two alpha, two beta chains (globin)– Each chain with a pigment portion (heme) containing an iron ion (Fe+2)-

-combines reversibly with one oxygen molecule• Each hemoglobin can combine with four oxygen molecules

– Hemoglobin also transports carbon dioxide on the globin portion—23% of carbon dioxide transport

• NO can be released by hemoglobin causing vasodilation and increased blood flow

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Erythrocytes• 120 day life cycle; become less flexible, more brittle• No repair possible; no nucleus• Recycles at the liver and spleen; broken down by macrophages.

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Iron Overload• Iron can become toxic in excessive levels• Iron ions typically bound with tranferrin or ferritin proteins• Seen with repeated transfusion

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Erythropoiesis• Proerythroblasts (produce hemoglobin);

mature to become reticulcytes• Reticulocytes enter the circulatory system and

within two days; become mature cells– Reticulocyte count usually 0.5-1.5% of

erythrocytes• Decreased number may mean inability

to make or making too little• Increased number may indicate proper

treatment for anemia/increased demand

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Erythrocytes• Hypoxia increases production via EPO

– Seen with hemorrhage, high altitude, circulatory problems, anemias– Feedback mechanism used to maintain homeostasis

• Anemias- decreased oxygen carrying ability; erythrocyte and/or hemoglobin deficiency– iron deficiency- hemorrhage; dec. iron intake– Megaloblastic(vit. B12)- decreased folic acid; – Pernicious anemia- due to lack of intrinsic factor– Hemorrhagic- loss of erythrocytes; large blood loss– Thalassemias- defective hemoglobin; alpha or beta chains.

Seen in people with Mediterranean heritage. Abnormal erythrocytes

– Aplastic anemias- inability to produce blood cells– S/sx- lethargy, cold-intolerance, pallor—conjunctiva, oral

mucosa, nailbed. Severe- cp, sob– Tx?

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Leukocytes

• Contain nuclei• MHC antigens on their cell membrane- cell recognition• Divided into granular or agranular type depending on the presence

of granules that take up stain– granular leukocytes--neutrophils, eosinophils, basophils– agranular leukocytes--lymphocytes (T cells, B cells), and

monocytes (become fixed or wandering macrophages as they exit blood vessels)

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Leukocytes• 5-10,000/microliter of blood• Numbers increase with infection--type of infection or stress

increases the specific number of leukocytes

• Leukocytosis- greater than 10K/microliter of blood– Strenuous exercise; microbial infection

• Leukopenia- less than 5K/microliter of blood– Radiation, chemotherapy, cortisol

• Only 2% of total WBC population in circulation– lymphatic fluid, skin, lungs, lymph nodes & spleen

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LeukocytesGranular leukocytes:• Neutrophils- also known as polys

(polymorphonuclear) or segs due to their multi-lobe nucleus

– 2-5 lobes; increase in number with age– 10-12 micron diameter– 60 to 70% of circulating WBCs– Stain blue/lilac with basic dye– Bands- immature cells with band/rod/horseshoe

shaped nucleus• Seen with acute infections

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Leukocytes

• Basophils- abundant granules present in cytoplasm obscuring nucleus, typically bi-lobed, irregular shaped

– 8 to 10 microns in diameter– Less than 1% of circulating

WBCs– Blue/lilac in color

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Leukocytes

• Eosinophils- large red/orange granules in cytoplasm

– Bilobed nucleus, thin strand connecting them

– 10 to 12 microns in diameter– 2 to 4% of circulating WBCs

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Leukocytes

Agranular leukocytes• Contain small granules not seen with the

light microscope

• Lymphocytes- round, darkly staining nucleus– Small (6-9 microns); large (10-14

microns)– Cytoplasm amount increases with size– increase in number during viral

infections– 20 to 25% of circulating WBCs

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Leukocytes

• Monocytes- 12-20 microns in diameter; – Kidney shaped or “dented” nucleus– Diameter is 12 - 20 microns– Cytoplasm is a foamy blue-gray – 3 to 8% of circulating WBCs– Blue-gray, “foamy” appearance of

cytoplasm– Become macrophages when they

leave blood vessels• Fixed- found in liver, lung, spleen• Wandering- travel into various

tissues; fxn in inflammation; fight infections

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Leukocyte function

• Neutrophils and macrophages- phagocytic, able to engulf pathogens and cause their destruction.

• Basophils- release histamine, heparin and serotonin; function in allergic reactions; increasing inflammation. Become mast cells

• Eosinophils- release histiminase, decreasing allergic reactions. Fight parasitic infections, phagocytize antibody-antigen complexes

• B-lymphocytes- produce antibodies in response to antigens. Give rise to antibody producing plasma cells

• T-lymphocytes- directly kill pathogens/invaders.

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Leukocyte function

Emigration (diapedesis)• With help via adhesion molecules

displayed by endothelial cells when damage occurs (selectins)

• Integrins on neutrophils attach – Neutrophils followed by

macrophages squeeze through to site of damage/infection

– Neutrophils & macrophages phagocytize bacteria & debris

– chemotaxis of both• kinins from injury site &

toxins

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Leukocyte function

• Neutrophils- phagocytic; release lysozyme, oxidants, defensins– Defensins- function like antibiotics against bacteria and fungi---

perforate cell wall– First responders

• Monocytes/Macrophages- phagocytic; respond in large numbers, destroy microbes and clean up cellular debris. – Seen with viral or funal infection

• Basophils- release histamine, heparin and serotonin. Chemicals involved in inflammation and allergic reactions, pain. Basophils become mast cells in connective tissue.

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• Eosinophils- enter tissue fluid, reduce effects of histamine via release of histiminase; fight parasites, phagocytize antibody-antigen complexes

• B lympocytes- destroy bacteria and their toxins– Transform into antibody producing plasma cells

• T lymphocytes- attack viruses, fungi, transplanted organs, cancer cells & some bacteria

• Natural killer cells– attack many different microbes & some tumor cells– destroy foreign invaders by direct attack

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Blood testsComplete blood count• Blood cell numbers- able to identify problems with anemias,

infections, thrombocyte levels.• Includes total number of erythrocytes, leukocytes and

thrombocytes. Leukocyte differential and hemoglobin also measured.

Leukocyte differential looks at the percentages of specific leukocytes; changes help with diagnosis

• In general terms- increased percentages could mean certain problems

neutrophils (bacterial infection)lymphocyte (viral infection)monocytes (fungal/viral infection)eosinophil (parasitic infection or allergy reaction)basophil (allergy reaction)

Normal hemoglobin range—in grams per 100mL of blood:– infants 14 to 20; adult females 12 to 16; adult males 13.5 to

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Thrombocytes

• Derived from myeloid stem cells responsible for hemostasis---stopping bleeding

• Thrombopoietin stimulates the eventual production of megakaryocytes

• Fragments of the magakaryocytes are the thrombocytes– 150-400K/microliter of blood– Each thrombocyte 2-4 microns in diameter– Forms plug via release of chemicals from granules– Live 5-9 days and then broken down at liver and spleen

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Hemostasis

Involves • Vascular spasm- vasoconstriction due to smooth muscle

damage; seen in small blood vessels, arterioles.

• Platelet plug formation- plug stops bleeding in small vessel breech; involves the release of clotting factors, ADP, ATP, Calcium, serotonin, enzymes producing thromboxane A2 from platelet granules

• Blood clotting (coagulation)- production of fibers that trap cells and form a gel mass (clot).

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Platelet Plug Formation

Platelets granules needed for platelet plug formation• clotting factors • platelet-derived growth factor

– cause proliferation of vascular endothelial cells, smooth muscle & fibroblasts to repair damaged vessels

• ADP, ATP, Ca+2, serotonin, fibrin-stabilizing factor, & enzymes that produce thromboxane A2

– Serotonin and thomboxane A2 act as vasoconstrictors– ADP,Thromboxane A2 make platelets sticky so they can

aggregate

• Steps in the process– (1) platelet adhesion (2) platelet release reaction (3) platelet

aggregation

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Platelet Plug Formation

• platelet adhesion- exposed collagen fibers stimulate adhesion thrombocytes

• Platelet release reaction- release of ADP, serotonin and thromboxane A2 results in vasoconstriction and thrombocytes becoming sticky

• Platelet aggregation- more platelets aggregate forming the plug. Now with blood clotting (coagulation) the formation of fibrin threads will stabilize the plug.

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Platelet Plug Formation

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Blood Clotting

• Involves the production of fibrin threads • Fibrinogen converted to fibrin via the enzyme thrombin• Thrombin produced from prothrombin via the enzyme

prothrombinase. • Two enzyme pathways lead to a common pathway seen

in the body that results in the production of prothrombinase.

• What is needed?– Clotting factors (produced at the liver)– Calcium– Chemicals released by platelets and damaged tissue– Completion of the three stages-

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Blood Clotting

• Extrinsic pathway- due to tissue trauma– Results in the release of TF– Fast----seconds; less steps

• Intrinsic pathway- due to damaged vessel walls– Damaged platelets, exposed

collagen fibers– Slower---minutes; more steps

• Common Pathway- prothrombinase with calcium results in the activation of prothombin into thrombin

• Third stage involves the conversion of fibrinogen into fibrin and the stabilization of threads via factor XIII

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Hemostasis

Retraction of Clot• Tightening of clot- platelets trapped in clot have Factor XIII

squeezed out • Platelets pull on fibrin• Fibroblast and endothelial cells continue repair

Role of Vitamin K:• Vitamin K- needed by the liver to produce clotting factors- factors II

(prothrombin), VII, IX and X• Produced in the GI tract via bacteria (lipid soluble vitamin)• Absorbed with help from bile

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Fibrinolytic system

• Blood clots are continually made and dissolved if not needed

• Fibrinolytic system dissolve inappropriate clots and those not needed once repair is done– Fibrinolysis- dissolving of clot

• Plasminogen- present in blood and clot– Plasminogen converted to plasmin (fibrinolysin)– Thrombin, factor XII and tissue plasminogen activator (t-PA)

does conversion

• Plasmin dissolves clot– Digest fibrin threads– Inactivates fibrinogen, prothrombin, factors V and XII

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Blood Clot Localization

• Fibrin absorbs thrombin into clot• Blood disperses clotting factors• Endothelial cells and leukocytes produce protacyclins

(prostaglandins) that oppose thromboxane A2

Anticoagulation in blood:• Antithrombin blocks clotting factors XII, X, II

(prothrombin)• Heparin produced by basophils and mast cells-

combines with antithrombin increasing the blocking of thrombin

• Warfarin/Coumadin- antagonist to Vitamin K• EDTA (ethylene diamine tetraacetic acid) and CPD

(citrate phosphate dextrose) remove/bind calcium

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Intravascular Coagulation (Clotting)

• Thrombus- blood clot in an unbroken blood vessel• Thrombosis- process of clotting in an unbroken blood

vessel• Embolis- thrombus that has become free floating in the

blood– Air bubble, fat, debris (bone), clot– Results in ischemia, infarction, stroke, PE

• Causes– Stagnant blood, endothelial damage– Tissue damage post surgery

• Tx- thrombolytic agents: plasminogen, streptokinase, t- PA; low dose aspril for prevention of repeated thrombus– Streptokinase- coronary artery – (t-PA)- MI, stroke due to obstruction

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Blood Groups/Types

• ABO blood groups• Universal Donor- O• Universal recipient- AB

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RH factor• Three alleles: Rh positive or negative• Can form antibodies to Rh factor if Rh negative and exposed to Rh

positive blood• Hemolytic disease of newborn (erythroblastosis fatalis)• Tx- anti-Rh antibodies (RhoGAM)

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Blood typing and crossing

• Typing involves determination of blood type• Crossmatch involves mixing donor and recipient blood to

ensure no transfusion reactions.

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Disorders• Sickle cell anemia- trait vs. disease• Decreases risk of malarial infection• Having both alleles for SC results in Dz.• Low oxygen levels cause erythrocytes to assume

sickle shape---obstructing blood flow

• Hemophilia-– Hemophilia A lacks factor VIII (males only)

• most common– Hemophilia B lacks factor IX (males only)– Spontaneous bleeding with minor truma,

bleeding at articulations leading to joint destruction

– X-lined seen mainly in male offspring of female carriers

– Replace missing clotting factors