Leukocytes- Slideshow Notes

Erythrocytes

• anuclear

• remain vasculature

• lifespan 120 days

• flexible

• 5.4 million erythrocytes per uL of blood

Leukocytes

• have nucleus/ organelles

• 5000-10,000 per uL of blood

• mean diameter ranges from 6-20 um

• typically leave vasculature

• lifespan hours to days

Steps in Release of Leukocytes

• injured tissue release cytokines that stimulate red marrow to release neutrophils

• damaged cells release factors the increase tissue permeability/ attract immune cells

• endothelial cells contract to create gaps and produce CAMS to grab neutrophils

• neutrophils enter tissue by crawling through gaps between endothelial cells

• neutrophils adhere to endothelium and roll along until they encounter a gap

Leukocyte Emigration/ Diapedesis

1. leukocytes in blood respond to chemical attractants released by pathogens and chemical signals from nearby injured cells

2. leukocytes squeeze between cells of capillary walls as they follow chemical signals to where they are most concentrated

3. within damaged tissue. monocytes differentiate into macrophages and phagocytes the pathogens, eosinophils and neutrophils release chemicals that break apart pathogens

Leukocytes

• Agranular

  • lymphocytes

  • monocytes

• Granular

  • basophil

  • neutrophil

  • eosinophil

Neutrophils

• most abundant leukocyte

• smallest in size

• multilobed nucleus with 3-5 lobes joined by slender strands

• combat bacterial infections

Eosinophils

• bilobed nuclei

• contain peroxidase, lysosomal enzymes, and major basic protein

• make up 1-3% of WBC

• largest of granulocytes

Eosinophil Function

• primary mode of attack is exocytosis of toxic compounds

• phagocytic and engulf antibody-coated or marked foreign substances

• respond to parasitic infection

Basophil

• least common WBC

• simple nucleus often hard to see due to large purplish granules

• granules release histamines which contribute to inflammation and heparin

Basophil Function

• high count common in allergic reactions and parasitic infections

• elevated in hypothyroidism

• low counts observed during pregnancy, stress, and hyperthyroidism

Monocytes

• can be fixed or wandering

• specialized macrophages may be referred to by different names in different tissues

• phagocytic cell

• participate in chemotaxis

  • release chemoattractants

• differentiate once they enter tissues

Macrophages

• principal cells involved in chronic inflammation and usually become more prevalent at the site of injury only after days or weeks

Monocyte Levels

• high counts indicate viral or fungal infection, TB, leukemia, or other chronic disorders

• abnormally low counts indicate abnormalities in bone marrow functions

Lymphocytes

• do not contain visible granules

• play major role in defense against disease

• 3 major types

  • B, T, and NK cells

NK Cell

• non-sepecific immunity

• recognize non-self cells

• engage in cell to cell combat

T cell

• part of specific immunity

• will develop memory cells after exposure to pathogen

• cell to cell killing of foreign or infected cell

• mature in thymus

• adaptive immunity

B Cell

• part of specific immunity (humoral)

• will develop memory cells after exposure to pathogen

• differentiate into plasma cells when activated

• mature in bone marrow

Leukocyte Levels

• high count could indicate viral infection or cancer

• low levels could indicate immunosuppression

Leukemias

• cancers of blood forming tissues

  • cancerous cells spread from origin in red bone marrow

  • first symptoms appear with presence of immature and abnormal WBC in circulation

  • fatal if untreated

Production of Platelets

myeloid stem cell→ megakaryoblast → megakaryocyte → platelet precursor extensions → platelets

Steps in Production of Platelets

1. myeoloid stem cells differentiate into megakaryocytes

2. megakaryocytes eventually shed cytoplasm in small membrane enclosed packets that = platelets