42 - Cardiovascular Histology Flashcards
Three layers of heart
1) Epicardium 2) Myocardium 3) Endocardium
Epicardium
Simple squamous epithelium lies on top of a lot of connective tissue. Blood vessels, fat, nervous tissue in this layer.
Myocardium
Cardiac muscle cells and capillaries
Endocardium
Endothelial layer, subendocardial connective tissue, conducting tissue.
Why is conductive tissue needed for synchronised heart contraction?
Gap junctions only provide local sharing of electric charge.
Which cell type is this?
Cardiac muscle
Conducting pathway through heart
How is the contraction of different heart chambers co-ordinated?
Purkinje fibres
Function of Purkinje fibres
Conduct signals from SA/AV nodes to ventricles
Purkinje fibres 1) 2) 3) 4)
1) Modified cardiac myocytes 2) Limited contractile machinery 3) Full of glycogen 4) Form bundles in subendocardium
Layers of all blood vessel walls
1) Tunica intima 2) Tunica media 3) Tunica adventitia
Tunica intima 1) 2) 3)
1) Lined with simple squamous epithelium 2) Epithelium lies on basal lamina 3) Supported by a thin subendothelial layer
What is this?
Tunica intima of a blood vessel. Note how, as the blood vessel is not full of blood, the endothelial cells bulge into lumen. When blood vessel is full, endothelial cells are taught
Roles of the endothelium 1) 2) 3)
1) Actively inhibit clotting by secreting inhibitors (EG: prostacyclin) 2) Prime underlying subendothelial tissue with Von Willebrand factor for clotting 3) Release vasoactive substances to smooth muscle like NO (vasodilatory), endothelin (strongly vasocontrictive)
How is smooth muscle arranged in media?
Concentrically or helically
Where does the connective tissue of the tunica media come from?
Secreted by smooth muscle. Collagen type III, elastin, ground substance.