Leukocytes, plasma, and Platelets

Leukocytes Structures

• Also called white blood cells (WBC’s)

• Less numerous than RBC’s

• Crucial to body defenses

Leukocytes Functional Characteristics

• Form protective mobile army against bacteria, viruses, parasites, toxins, & tumor cells.

• Can slip into & out of blood vessels by DIAPEDESIS.

• Pinpoint areas of tissue damage & destroy foreign substances or dead cells

2 Main Types of Leukocytes

Granulocytes and Agranulocytes

Granulocytes

1. Have a granular cytoplasm

2. Originate from bone marrow

3. 65% of leukocytes

4. Multi-lobed nuclei

Agranulocytes

1. No granules in cytoplasm

2. Originate from lymphoid

3. 35% of leukocytes

4. Nucleus has single lobe

Granulocytes -> Neutrophils

-Most Numerous.

-Nuclei consist of 3-5 lobes.

-Attracted to sites of inflammation & active phagocytes

Granulocytes >Basophils

-u or s-shaped nucleus

-causes cells to release heparin & histamine.

-histamine: vasodilator 

-heparin: prevents blood clotting

-enhance migration of wbc’s

Granulocytes >Eosinophils

-nucleus has two lobes like figure 8 (sort of)

-reside in intestinal & pulmonary mucosae

-phagocytic

Agranulocytes > Lymphocytes

-2nd most numerous

-found in lymph tissue

-major cells of immunity

-yield antibodies

-nucleus is spherical & takes up most of cell

Agranulocytes > Monocytes

-nucleus is kidney shaped

-highly mobile macrophages

-Phagocytic

Production of WBCs

• Leukopoiesis: production of wbc’s

• Life span from a few days to several years

Blood plasma contains over 100 solutes:

Proteins, Organic Nutrients, Electrolytes, Respiratory gases and Plasma Proteins

Proteins

albumin, globulins, clotting proteins, and others (Lactic acid, urea, creatinine)

Organic nutrients

glucose, carbohydrates, amino acids

Electrolytes

sodium, potassium, calcium, chloride, bicarbonate

Respiratory gases

oxygen and carbon dioxide

Plasma Proteins

• Albumins – blood pressure

• Globulins (alpha, beta, gamma) – transport lipids and antibodies for immunity

• Fibrinogen – important for blood clotting

Hemostasis

• The process of stopping blood flow. Involves coagulation and clotting.

• 3 Events of Hemostasis

Stage 1

When the blood vessel wall is broken, thrombocytes (platelets) in the blood (which are easily damaged) disintegrate and release an enzyme called thromboplastin. Thromboplastin then converts a protein in the blood plasma called prothrombin into an active enzyme called thrombin. Calcium is needed for this process to work. (So: thromboplastin + calcium + prothrombin = thrombin). This makes the platelets stickier so they start to bind directly over the site of injury.

Stage 2

Thrombin then changes another plasma protein, fibrinogen into fibrin. Fibrin is insoluble and forms a netlike covering across the damaged vessel. (Thus thrombin + fibrinogen = fibrin).

Stage 3

As blood tries to flow through the net, red and white blood cells and platelets are trapped and form a clot. (Thus fibrin + blood cells = clot).

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Disorders of hemostasis

Thrombus, Embolus, Thrombocytopenia, Hemophilias

Thrombus

• Clot that develops & persists in an unbroken blood vessel

  • if too large may block circulation

Embolus

• Thrombus that breaks away from vessel wall & floats freely in bloodstream

  • will block circulation if encounters small artery

Thrombocytopenia

• Condition in which number of circulating platelets is reduced, causes bleeding

Hemophilias

• Inability for blood to clot properly