BIOLOGY 2B03 Chapter Notes - Chapter 8: Blood Vessel, Neutrophil, White Blood Cell
17 Jun 2018
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BIOLOGY 2B03 - Module 8 Lecture II
Leukocytes Leave the Blood Vessel
● Cell function requires transient or temporary associations that are established but then broken
again
● Example: connections that allow cells to migrate across an extracellular surface and the
migration of cells during embryogenesis
● Another example: the movement of leukocytes in response to local viral or bacterial
infections or traumatic injury
● The movement of leukocytes out of the blood vessel depends on a precise sequence of
adhesive interactions
○ Which together are called extravasation
● Endothelial cells: Specialized epithelial cells; forms the wall of the blood vessels
○ Adhesion between cells prevents the leakage of cells out of blood vessels
● Normally leukocytes are moving quicking with the red blood cells in the blood vessels
○ Leukocytes must be able to establish temporary connections with endothelial cells
→ mediated the process of extravasation and get to the site of infection
Types of Leukocytes
Granulocytes: target pathogens and include the neutrophils, eosinophils, and basophils
● Neutrophils: the most numerous
○ Undergo the process of extravasation, while eosinophils and basophils don’t
● These target primarily bacterial infections and are one of the first cells to respond to trauma
Monocytes: differentiate into macrophages
● Which engulf invading bacteria or dead and damaged cells through phagocytosis
● These cells are also capable of extravasation
Lymphocytes: includes the NK cells, or natural killer cells that lyse virally infected cells and
tumour cells
● T and B cells produce antibodies as part of immune response
● These cell types are also able to undergo extravasation
Overview of Extravasation
Extravasation is five-step process
● Initiated by a signal created by infection
● Example) free neutrophil moving through the blood vessels → a transient association
between the neutrophil and the apical surface of an endothelial cell within endothelial
wall → neutrophils are pushed by the flow of blo0d through the vessel but slower → the
cells are rolling along the endothelial cells
○ Rolling slows as the number of associations between the neutrophil and the
endothelial cells increase
○ Firm adhesion is the stronger attachment of the neutrophil with the endothelial cells
○ Accompanied by transmigration
■ To break connections between the endothelial cells and migrate along the
surface of the cells into the space outside of the blood vessel
○ At the site of infection: swelling occurs → result of escape of blood plasma in
addition to the transmigration of various leukocytes
Capture
● Signal from the infection that trigger capture of the neutrophil
● Mediated through cytokines released at infection
find more resources at oneclass.com
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Document Summary
Cell function requires transient or temporary associations that are established but then broken again. Example: connections that allow cells to migrate across an extracellular surface and the migration of cells during embryogenesis. Another example: the movement of leukocytes in response to local viral or bacterial infections or traumatic injury. The movement of leukocytes out of the blood vessel depends on a precise sequence of adhesive interactions. Endothelial cells: specialized epithelial cells; forms the wall of the blood vessels. Adhesion between cells prevents the leakage of cells out of blood vessels. Normally leukocytes are moving quicking with the red blood cells in the blood vessels. Leukocytes must be able to establish temporary connections with endothelial cells. Mediated the process of extravasation and get to the site of infection. Granulocytes: target pathogens and include the neutrophils, eosinophils, and basophils. Undergo the process of extravasation, while eosinophils and basophils don"t.
