BIOL 303 Lecture Notes - Lecture 12: Natural Killer Cell, Vascular Endothelial Growth Factor, Endothelium
Chapter 22 Part 3&4
Lecture III
• Briefly describe the characteristics of vascular endothelial cells, pericytes, and the steps
in angiogenesis (slides 4-6).
• Angiogenesis is the process whereby endothelial cells proliferate and form blood
vessels.
• Each new vessel originates as ‘sprouts’, at the tip of which is an endothelia
tip cell that is non-mitotic.
• Tip cells long filopodia, endothelia cells then migrate behind the
tip cells and become a hollow tube through fusion of pinocytic
vesicles.
• Tip cells are attached and repulsed by chemical gradients.
• Surrounding tissue release chemical signals (i.e. ligands) that can attract a
growing vesicle.
• Vascular endothelia growth factor (VEGF) is one key chemical ‘gradient factor’.
• For example:
• 1. Hypoxia (lack of O2) increases hypoxia-inducible factor 1alpha
(HIF1alpha),
• 2. Stimulates VEGF transcription
• 3. Surround cell release VEGF (secretory vesicles).
• 4. VEGF receptors (VEGFRs) are tyrosine kinase receptors, bind
VEGF and produce chemotaxis of growing filopodia & vessel
toward VEGF signal.
• 5. Blood enters newly constructed vessel, O2 rises, HIF1α
production declines in tissue, angiogenesis stops.
• Match blood cell types to their general function & abundance (slides 7-9).
• Hematopoietic (blood-making) stem cells are multipotent, producing all the red
and white differentiated blood cells, as well as some other cell types (e.g.
osteoclasts)
• Red blood cells (aka RBCs, erythrocytes) carry O2 and CO2, only one type of
differentiated cell.
• White blood cells (aka leukocytes) combat infection as part of immune system,
cross into blood and lymphatic vessels, and phagocytize invaders and cell debris.
• Made up of 3 main categories (Granulocytes, Monocytes, Lymphocytes)
with many differentiated cell types within each category.
• Platelets are fragments from large megakaryocytes. Adhere to damaged blood
vessels, central to clotting response.
• Monocytes (produce dendritic cells): Become tissue macrophages, which
phagocytose and digest invading microorganisms and foreign bodies as well as
damaged senescent cells.
• Lymphocytes
• T cells: Kill virus-infected cells and regulate activities of other leukocytes.
• B cells: Make antibodies.
• Natural killer (NK) cells: Kill virus-infected cells and some tumor cells.
• Platelets (cell fragments arising from megakaryocytes in bone marrow): initiate
blood clotting.
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