Lecture 5.8 Cardiovascular Histology Flashcards
What are the three layers of the heart? Name their components.
Epicardium the outer layer, which is a simple squamous epithelium. Has subepicardial connective tissue, blood vessels, fat, nerves.
Myocardium made of myocytes and capillaries.
Endocardium has an endothelial layer, subendothelial connective tissue, conducting tissue.
Describe purkinje fibres.
They are modified cardiac muscle cells specialised for electrical conduction.
They have lost the ability to contract, are full of glycogen and form bundles in subendocardium.
True or false? The nervous system beats the heart in an average person.
False. It only modifies the beating (faster/slower).
Describe 4 things about the intima.
Lined with squamous epithelium. Lies on a basal lamina supported by thing subendothelial connective tissue layer.
Inhibits clotting by secreting inhibitors.
But it also primes underlying subendothelial connective tissue with Von Willebrand’s factor to activate clotting during trauma.
Releases substances like endothelin and nitric oxide to constrict and dilate respectively.
Describe 3 things about the intima.
Mostly smooth muscle lined concentrically or helically.
They play the role of the fibroblast and they make the connective tissue in which they are embedded. It is made of collagen type 3, elastin and ground substance.
Can vary from 1 single layer to 40-50 layers of muscle.
Describe 2 things about the adventitia.
Made of connective tissue which is type 1 collagen, elastin, ground substance.
Anchors to surrounding tissue, and has its own blood supply known as vasa vasorum.
What is special about elastic arteries?
They lie closest to heart, and withstand massive blood pressure fluctuations. They also form the diastolic pressure as they have a compliance that pushes at the end of systole (diastole).
What are muscular arteries?
These are arteries that distribute blood to tissue, have little elastin but elastin are concentrated in internal and external elastic laminae. That is, layers between intima/media, and media/adventitia respectively.
True or false? Arterioles contribute most to TPR.
True.
What is the name of an intermediate vessel between arteriole and capillary? What is it characterised by?
Meta arteriole. Characterised by incompletely smooth muscle coat.
What are capillaries made of?
Single endothelial cells rolled into a tube and sealed with tight junction. Also has a basal lamina. Sometimes they can be associated with pericyte and surrounded by some collagen fibres (from adventitia).
What is a big difference between veins and arteries in terms of their media/adventitia?
Veins have thicker adventitias thinner medias. This is to withstand immense hydrostatic pressures.
Where does exchange occur most in terms of inflammatory cells?
Venules.
True or false? Relative arteries and veins have the same sized diameters.
False, veins have larger diameters. They have very well developed subendothelial connective tissue.
True or false? Lymphatics lack red blood cells.
True. That’s how we can differentiate them histologically. Otherwise, they look very similar to venules. They also have valves.
