Vascular System Histology Flashcards
Angiogenesis
vessel formation via branches arising from existing vessels
Vasculogenesis
blood vessels arise from coalescence of hemangioblasts, which arise from blood islands
How do major vessels form?
Vasculogenesis
Why is it important to understand the processes of angiogenesis and vasculogenesis?
An understanding of these processes is relevant to developing therapeutic strategies to produce revascularization of ischemic tissues or inhibit angiogenesis in cancer and other disorders
When and where does early vasculogenesis begin?
In week 3 in extraembryonic splanchnic mesoderm surrounding the yolk sac: formation then moves into lateral plate mesoderm
What is the first site of formation of blood islands
Yolk sac.
Islands arise from mesoderm cells that are induced to form hemangioblasts, a common precursor for vessel and blood cell formation
Hemangioblasts differentiate into what two populations of cells
angioblasts and hematapoetic stem cells
Define angioblasts
vascular precursors - form endothelial cells. coalesce into cords and form a lumen
Define hematapoietic stem cells
differentiate into all types of blood cells
mesenchymal cells to hemangioblasts is regulated by
FGF 2
What factor elicits regional change in blood islands
VEGF (vascular endothelial growth factor)
signal to express VEG F may invlove HOXB5 which upregulates VEGF receptor FLK1
Factors involved in angiogenesis
VEGF, Ang1, Ang2
Role of Ang1
in angiogenesis, recruits pericytes to sm muscle cells in large vessels to organize mature blood vessels
Role of Ang 2
works where you might want to punch a hole and have something grow out. works on endothelial cells and stops interactions btwn them - either absence of growth OR cell death.
Vein specific genes controlling venous development
EPHB4
master gene for lymphatic vessel differentiation
PROX1
Specification of vessel type happens when?
Soon after angioblast induction
What factors specify arterial development?
SHH from notochord induces expression of VEG-F in mesoderm
VEG-F induces Notch pathway which specifies arterial development
through expression of EphrinB2 (ligand)
AGM stands for?
Aorta - gonad - mesonephros region.
What is found in the AGM
Definitive hematopoietic stem cells. These cells will eventually colonize the liver, which becomes major hematopoietic organ of the embryo (2-7 months). Hematopoiesis moves form liver to bone marrow at 7 months.
Progression of hematopoeisis
Blood islands - FGF@ tells them to become hemangioblasts - difinitive hematopoeitic stem cells then seen in AGM - liver - bone marrow.
What is a Hemangioma
Abnormally dense collection of capillary vessels. common tumors of infancy. focal or diffuse, look for other secondary complications
What is a Port Wine Stain?
superficial and dilated capillaries in the skin.
Tumor Angiogenesis
When some of the tumor cells switch to an angiogenic phenotype, the local equilibrium between positive and negative angiogenic refulators changes. allows the tumor to grow.
Folded endothelial tube whose wall is thickened to act as a regulated pump
Heart
Endocardium
consisting of an endothelial lining and sub endothelial CT
Myocardium
Functional syncytium of striated cardiac muscle fibers foming 3 major types of cardiac muscle
3 major types of cardiac muscle
atrial muscle
ventricular muscle
specialized excitatory and conductive muscle fibers.
Epicardium
Visceral layer of the pericardium
is a low friction surface
lined by a mesothelium in contact with the parietal pericardial space.
Cardiomyocytes (3 kinds)
Contractile
myoendocrine
Nodal
Contractile cardiomyocytes
Contract to move blood
Myoendocrine cardiomyocytes
produce atrial natriuretic factor that stimulates diuresis and excretion of Na in urine by +glomerular filtration rate, -blood volume