Lecture 12: Composition and Functions of Blood

functions of blood

• transport

  • nutrients, gases, waste products, hormones

• regulation

  • thermoregulation

  • fluid and electrolyte balance

  • pH balance

• protection

  • immunity

  • hemostasis (clotting)

hematocrit

percentage of blood volume occupied by erythrocytes

can range from 25-60% depending on species

anemia, kidney, heart, and lung issues can affect RBC production

hemoglobin

imparts red color, depending on degree of oxygen saturation

plasma

colorless to yellow

blood volume

can vary from 5-8% BW depending on species

blood pH

rangs 7.35-7.45

venous blood is slightly more acidic due to increased CO2

WBC

produced in bone marrow or lymph tissue

circulate in blood and reside in some tissues

classified as granulocytes or agranulocytes

granulocytes

granules in cytoplasm

produced in bone marrow

neutrophils (both stains)

basophils (basic/blue)

eosinophils (acidic/red)

agranulocytes

monocytes and lymphocytes

monocytes

produced in bone marrow

agranulocyte

lymphocytes

produced in lymph nodes, splee, tonsils, lymphoid clusters in intestines

agranulocyte

granules

contain enzymes and inflammatory mediators that aid immune function

leukocytes

circulate in blood after development until leaving blood to perform jobs

typical total count 7000-15000 cells/uL

granulocyte lifespan

in blood 6-20 hours, constantly leaving

in tissues 2-3 days

don’t return to blood after leaving

monocytes lifespan

in blood <24 hours

in tissues for months

become fixed macrophages in liver, spleen, bone marrow, and lymph nodes

lymphocytes lifespan

recirculate constantly from blood to tissues, to lymph, and back to blood

• T cells live 100-200

• B cells live 2-4 days

• Memory T and B cells live for years

neutrophil-predominant species

dog

cat

horse

lymphocyte-predominant species

cow

sheep

goat

pig

dog neutrophil and lymphocyte WNL percentage

N: 65-70

L: 20-25

cat neutrophil and lymphocyte WNL percentage

N: 55-60

L: 30-35

horse neutrophil and lymphocyte WNL percentage

N: 50-60

L: 30-40

cow neutrophil and lymphocyte WNL percentage

N: 25-30

L: 60-65

sheep neutrophil and lymphocyte WNL percentage

N: 25-30

L: 60-65

goat neutrophil and lymphocyte WNL percentage

N: 35-40

L: 50-55

pig neutrophil and lymphocyte WNL percentage

N: 30-35

L: 55-60

Which leukocyte is the first to arrive at the site of acute inflammation and phagocytize?

neutrophils

neutrophils

• first leukocyte to arrive at a site of acute infection

  • phagocytize → pus

• azurophilic granules supply lysosomes → digest bacteria and viruses

• other granules produce hydrogen peroxide → kill bacteria

• lactoferrin → sequesters iron needed for bacterial growth

Which leukocyte transforms into macrophages, and is in high numbers in chronic infections?

monocytes

monocytes

• high numbers in chronic infections

• circulating monocytes phagocytize bacteria, viruses, and antibody-antigen complexes

• leave blood → enter tissues → transform to macrophages → kill phagocytized microbes using acidic pH, enzymes, and hydrogen peroxide

• comprise the mononuclear phagocytic system (MPS)

mononuclear phagocytic system (MPS)

• monocytes → intravascular (blood)

• macrophages → extravascular (tissues)

• mobile cells → macrophages

• fixed cells → Kupffer cells (liver, spleen, lymph nodes)

Which leukocytes dampen and terminate inflammatory allergic reactions, and is in high amounts in a parasitic infection?

eosinophils

eosinophils

• parasites → granules discharged onto opsonized parasites → attacked by antibodies

• limit allergies → granules contain histaminase → dampen and terminate inflammatory allergic reactions

Which leukocyte has receptors for IgE, and promotes local vascular and tissue allergic reactions?

basophils

basophils

• low in numbers when WNL

• receptors for IgE (antibodies associated with allergies)

  • antigen binds IgE on basophil → basophil ruptures → promotes local vascular and tissue allergic reactions

• granules contain histamine, bradykinin, serotonin, lysosomal enzymes

Cell mediated immunity

cytotoxic T cells (killer T cells)

• attack transplanted organs

• directly destroy infected or abnormal cells by recognizing specific antigens and releasing cytotoxic substances

Helper T cells

• coordinate immune response by activating cytotoxic T cells and stimulating B cells

Memory T cells

• long-lived cells that “remember” previous antigens and mount a faster response upon re-exposure

cytotoxic T cells (killer T cells)

• attack transplanted organs

• directly destroy infected or abnormal cells by recognizing specific antigens and releasing cytotoxic substances

Helper T cells

• coordinate immune response by activating cytotoxic T cells and stimulating B cells

Memory T cells

• long-lived cells that “remember” previous antigens and mount a faster response upon re-exposure

Humeral immunity

activated B cells

• proliferate after recognizing an antigen and differentiate into plasma cells and memory B cells

memory cells

• long-lived cells that respond rapidly to future exposure to the same antigen

plasma cells

• produce and secrete large quantities of antibodies that bind and inactivate antigens (humeral immunity)

activated B cells

• proliferate after recognizing an antigen and differentiate into plasma cells and memory B cells

memory cells

• long-lived cells that respond rapidly to future exposure to the same antigen

plasma cells

• produce and secrete large quantities of antibodies that bind and inactivate antigens (humeral immunity)

hemoglobin molecule composition

4 globin chains

4 heme groups (each contains iron)

can carry 4 oxygen molecules

erythropoesis

production of erythrocytes

• rate is controlled by oxygen need → erythropoetin from kidneys stimulates production

• reticulocytes increase

reticulocytes

immature RBC that retain some ribosomes

mature in blood after a few days

Dog RBC shape

biconcave disc

goat RBC shape

spherical

camel RBC shape

elliptical

deer RBC shape

sickle

myoglobin

one heme group and one globin chain (muscle has this)

primary hemostasis

formation of a temporary plug

What molecule has the primary role of initiating platelet adhesion after vessel injury in primary hemostasis?

collagen

What molecule has the primary role of bridging platelets to exposed collagen (adhesion) in primary hemostasis?

von Willebrand factor (vWF)

What molecule has the primary role of activating and recruiting additional platelets in primary hemostasis?

Thromboxane A₂ (TXA₂)

What molecule has the primary role of bridging activated platelets together (aggregation) in primary hemostasis?

fibrinogen

What molecule has the primary role of reinforcing platelet activation and initiating fibrin formation during secondary hemostasis in primary hemostasis?

thrombin

Aspirin irreversibly binds to and inhibits _______, which prevents _____ synthesis and results in a [longer/shorter] bleeding time

cyclooxygenase-1 (COX-1)

TXA2

longer

How is plasma obtained? What about serum?

P: blood is collected with an anticoagulant to prevent clotting

S: blood is allowed to clot before collection

Describe the clotting factors in plasma vs. serum

P: present (including fibrinogen)

S: absent (consumed during clot formation)

primary function of plasma vs serum

P: transport medium and exchange between blood vessels and tissues

S: laboratory sample remaining after clot formation

water content of plasma vs serum

P: >90% water

S: >90% water (minus clotting factors)

major proteins in plasma vs serum

P: albumin, globulins (a, B, y), fibrinogen

S: albumin and globulins remain, fibrinogen is absent

immunoglobulins in plasma vs serum

P: y-globulins (IgG, IgE, IgA, IgM, IgD) present

S: same immunoglobulins remain present

clinical application of plasma vs serum

P: preferred when coagulation factors need to be measured

S: preferred when clotting factors are not needed

albumin

maintains >80% of plasma oncotic pressure and transports many substances

predominant plasma protein in dogs, sheep, goats, and humans

globulins

include transport proteins and immunoglobulins (antibodies)

albumin and globulins are present in nearly equal amounts in horses, pigs, cows, and cats

y-Globulins (immunoglobulins)

antibodies involved in immune defense

IgG is the most abundant

fibrinogen

precursor of fibrin during coagulation

present in plasma but absent in serum

Albumin, fibrinogen, and some globulins are produced where?

liver

Most immunoglobulins (y-globulins) are produced where?

plasma cells in lymphoid tissues (lymph nodes and mucosal tissues)

primary hemostasis

platelets adhere, activate, and aggregate to form a temporary platelet plug

secondary hemostasis

fibrin stabilizes the platelet plug to form a stable clot, which later retracts and is removed by fibrinolysis