CVM 711 Lecture 12: Composition and Functions of Blood

• Percentage of blood volume occupied by erythrocytes

• Can range from 25-60% depending on species

Hematocrit

Imparts red color (depending on degree of oxygen saturation)

Hemoglobin

Colorless to yellow

Plasma

Range of 7.35 - 7.45

Blood pH

What is more acidic: Venous blood or arterial blood?

Venous blood

What is more acidic: O2 or CO2?

CO2

Less 02, more CO2

Venous blood

More O2, less CO2

Arterial blood

What is another term for red blood cells?

Erythrocytes

What is another term for white blood cells?

Leukocytes

What are the two classifications of WBCs/leukocytes?

Granulocytes and agranulocytes

What are the three granulocytes?

Neutrophils, basophils, and eosinophils

What are the two agranulocytes?

Monocytes and lymphocytes

Stay in blood for 6-20 hrs, constantly leaving blood. Stay in tissues for 2-3 days. Do not return to blood after leaving.

Granulocytes (the phils)

Stay in blood for less than 24 hours. Stay in tissues for months. Become fixed macrophages in liver, spleen, bone marrow, and lymph nodes

Monocytes

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

Lymphocytes

How long do T cells live?

100-200 days

How long do B cells live?

2-4 days

How long do T and B cells live?

For years

What is the typical total leukocytes (wbc) count?

7000 - 15000 cells/μL

What are the neutrophil (a type of granulocyte) predominant species?

Dog, cat, horse (N is for compaNioN)

What are the lymphocyte (a type of agranulocyte) predominant species?

Cow, sheep, goat, pig (L is for Livestock)

• First leukocytes (wbc) to arrive at site of acute inflammation

• Very mobile

• Numbers increase dramatically in acute infections

• Cause phagocytosis which forms pus

• Azurophilic granules supply lysosomes

• Other granules produce hydrogen peroxide

• Lactoferrin (sequesters iron needed for bacterial growth)

Neutrophils

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

• Leave blood in order to enter tissues, they then transform to macrophages in order to kill phagocytized microbes using acidic pH, enzymes, and hydrogren peroxide

Monocytes

Which part of the mononuclear phagocytic system (MPS) is intravascular (in blood)?

Monocytes

Which part of the mononuclear phagocytic system (MPS) is extravascular (in tissue)?

Macrophages

Which part of the mononuclear phagocytic system (MPS) are mobile cells?

Macrophages

Which part of the mononuclear phagocytic system (MPS) are fixed cells?

Kupffer cells (in liver, spleen, and lymph nodes)

• Discharge granules onto opsonized parasites (parasites that have been attacked by antibodies)

• Limit allergies due to the granules containing histaminase which dampens and terminates inflammatory allergic reactions

Eosinophils

• Receptors for IgE (antibodies associated with allergies)

• Antigen bings IgE which causes this cell to rupture, which promotes local vascular and tissue allergic reactions

• Granules contain histamine, bradykinini, serotonin, and lysosomal enzymes

• Low numbers in normal, healthy animals

Basophils

What are T and B cells?

Lymphocytes

What are the cell-mediated immunity cells?

T cells (the T in cell-mediaTed)

What are the humoral immunity cells?

B cells (B is for bone marrow, humerus is a bone)

Directly destroy infected or abnormal cells by recognizing specific antigens and releasing cytotoxic sybstances. Are known to attack transplated organs.

Cytotoxic T cells (killer T cells)

Coordinate the immune response by activating cytotoxic T cells and stimulating B cells

Helper T cells

Long-lived cells that remember prevoius antigens and mount a faster response upon re-exposure

Memory T cells

Proliferate after recognizing an antigen and differentiate into plasma cells and memory B cells

Activated B cells

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

Memory B cells

Produce and secrete large quantities of antibodies that bind and inactivate antigens (humoral immunity)

Plasma cells

4 globin chains, 4 heme groups (each group has iron) → can carry 4 oxygen molecules

Hemoglobin molecule

production of erythrocytes 

erythropoiesis

What from the kidneys stimulates production of erythrocytes (rbc)

Erythropoietin

Immature erythrocytes (rbc) that retain some ribosomes and mature in blood after a few days. Numbers increase if RBC production is increased.

Reticulocytes

What is the RBC shape in dogs?

Biconcave disk

What is the RBC shape in goats?

Spherical

What is the RBC shape in camels?

Elliptical

What is the RBC shape in deer?

Sickle

4 globin chains, 4 hem groups, can carry 4 oxygen molecules

Hemoglobin

One heme group, one globin chain

Myoglobin

Formation of a temporary platelet plug

Primary hemostasis

• Vascular damage exposes collagen in the basement membrane.

• Damaged endothelial cells release fibronectin and von Willebrand factor (vWF), which promote platelet adhesion.

Step 1 of primary hemostasis: Vessel injury exposes collagen

• Platelets bind exposed collagen through vWF (platelet adhesion)

• Platelets extend pseudopods to capture additional circulating platelets

Step 2 of primary hemostasis: Platelets adhere to the injured site

• Collagen and thrombin activate platelet receptors

• Intracellular Ca2+ increases

• Activated platelets synthesize and release TXA2

Step 3 of primary hemostasis: platelets become activated

• TXA2 amplifies platelet activation (positive feedback)

• Activated platelets release α-granules and dense granules containing coagulation factors, Ca2+, ADP, ATP, serotonin, and additional vWF

Step 4 of primary hemostasis: Platelets recruit additional platelets

• Activated platelet integrins bind fibrinogen, which bridges adjacent platelets

• Platelets continue to aggregate, forming a temporary platelet plug that limits blood loss until stabilized by fibrin during secondary hemostasis

Step 5 of primary hemostasis: Platelets aggregate to form temporary plug

Initiates platelet adhesion after vessel injury

Collagen

Bridges platelets to exposed collagen (adhesion)

von Willebrand factor (vWF)

Activates and recruits additional platelets

Thromboxane A₂ (TXA₂) (thanx for helping collagen)

Bridges activated platelets together (aggregation)

Fibrinogen

Reinforces platelet activation and initiates fibrin formation during secondary hemostasis

Thrombin

Formation and resolution of a stable fibrin clot

Secondary hemostasis

• Thrombin converts fibrinogen into fibrin (to turn gen to rin, you need the bin)

• Fibrin forms a mesh-like network that reinforces the temporary platelet plug

• Blood cells become trapped within the fibrin mesh, producing a stable clot firmly attached to the vessel wall

Step 1 of secondary hemostasis: Fibrin clot forms

• Platelet contractile proteins (thrombosthenin, actin, and myosin) contract, causing the clot to shrink

• Serum is squeezed out of the clot, allowing more blood flow to the damaged tissue

• Clot retraction reduces wound size and draws the vessel walls closer together to promote repair

Step 2 of secondary hemostasis: Clot retracts

• Plasmin, an enzyme, breaks down the fibrin meshwork

• The clot is gradually dissolved once healing has occured

• Normal blood flow is restored through the repaired vessel

Step 3 of secondary hemostasis: Clot dissolves (fibrinolysis)

Involved in killing or inactivating antigens, and creating memory cells to respond to antigens when exposed in the future

Lymphocytes

Transforms to a macrophage before using acidic pH, enzymes, and hydrogen peroxide to kill

Monocyte

Contains cell-surface receptors for IgE and granules contain substances to enhance allergic reactions

Basophil

Granules supply lysosomal enzymes and hydrogen peroxide to digest and kill

Neutrophil

Granules contain histaminase to dampen/stop allergic reactions

Eosinophil