Lecture 4 - Cardiovascular System 2 Flashcards
What are the 3 systems?
Arterial system
Venous system
Capillaries
Outline the arterial system
Arteries - carry blood away from heart
Arterioles - Smallest branches of arteries that lead to the capillary bed - blood pressure regulation through vasoconstriction and dilation
High pressure system delivering blood away from the heart
Outline the venous system
Venules - Smallest branches of the veins that collect from the capillaries - lower rate of blood flow
Veins - return blood to the heart
Outline the capillary system
Capillary bed - smallest blood vessels with thin walls
Location of exchange between blood and interstitial fluid
What is the AVA?
Arteriovenous anastomosis (collateral circulation)- Low resistance pathways that can bypass the capillary bed specifically in rapid control e.g. temperature regulation
What is the pathway of blood?
Heart - artery - arterioles - capillaries - venules - veins - heart
How is blood distributed?
64% - systemic venous system (most due to lower pressure and slower moving)
7% - systemic capillaries
13% - systemic arterial system
7% - heart
9% - Pulmonary circuit
What is the basic blood vessel structure?
Endothelium
Tunica intima
Tunica media
Tunica externa
What is the Tunica intima?
Inner layer
Encompasses the endothelial lining and connective tissue layer
Arteries - internal elastic membrane providing passive elasticity
Provides a secondary pump / pressure to the blood
Veins - aren’t as elastic - lower pressure
What is the endothelium?
Releases vasoactive substances which affect vascular tone, blood pressure and blood flow
Friction with endothelium cells and autonomic responses stimulate the release of vasodilators e.g. nitric oxide or vasoconstrictors e.g. endothelin
Maintains vascular homeostasis
What is the Tunica Media ?
Middle layer
Contains concentric sheets of smooth muscle in loose connective tissue some elastic fibres in arteries and collagen in veins
Encircles the endothelium that lines in the lumen of the vessel
Binds to inner and outer layer
What is the Tunica externa?
Outer layer
Anchors vessels to adjacent tissues
Contains - Collagen fibres, elastic fibres, smooth muscle in veins
What is the Vasa vasorum?
Vessels of vessels
Small arteries and veins in walls of large arteries and veins
Serve cells of Tunica media and externa
What are the differences between the typical artery and vein?
General appearance - a- round with thick walls / v- flattened or collapsed with thin walls
Intima / endothelium - a - rippled due to role in vessel constriction, internal elastic membrane
v - smooth and no elastic
Media - a - Thick smooth muscle and elastic fibers with an external elastic membrane v - thin smooth muscle and collagen no elastic membrane
Externa - a - Collagen and elastic fibres v - collagen and elastic fibres and smooth muscle
What are the 3 types of arteries?
Elastic - biggest - high elastin content in the aorta - conducting artery - secondary pump to allow blood flow (pressure reservoir )
Muscular - Tunica media is dominated by smooth muscle - e.g. femoral artery - less elastin - capable of greater vasodilation and constriction
Arterioles - no externa or interna - layer of endothelial cells wrapped in smooth muscle - big changes in blood pressure and flow
What are capillaries?
Endothelial tube inside thin basement membrane
No tunica media no tunica externa
Diameter is similar to a RBC
Exercise training - increased density of capillary bed
What are the 3 types of capillary?
Continuous, fenestrated and sinusoid
What are continuous capillaries?
Found in all tissues except epithelia and cartilage - nutrients from synovial fluid avascular
Have complete endothelial lining
Permit diffusion of water, small solutes and lipid soluble materials - blocks bigger cells blood and plasma proteins from moving
Specialised continuous in CNS and thymus - very restrictive permeability e.g. blood brain barrier
What are fenestrated capillaries?
Have pores in the endothelial lining
Permit rapid exchange of water and larger solutes
Found in the
Choroid plexus - group of cells that secrete CSF
Endocrine organs - hormones into the blood
Kidneys - dealing with waster products
Intestinal tract
What are Sinusoid capillaries?
Have gaps between adjacent endothelial cells
Permit free exchange of water and large plasma proteins
Found in Liver ,Spleen ,Bone marrow - for production of RBC , Endocrine organs
Phagocytic cells monitor blood at sinusoid - can engulf and break down bacteria and smaller particles
What is the capillary structure and function?
Capillary bed (plexus) - connects one arteriole and one venule
Precapillary sphincter - guards the entrance, opens and closes causing capillary blood to flow in pulses
Thoroughfare channels - Direct capillary connections between arterioles and venules
What are veins?
Collect blood from capillaries and return it to the heart
Compared to arteries they have
Larger diameter (lumen), thin walls, lower blood pressure
Smooth muscle which can vasoconstrict to help blood back to the heart
What are the 3 types of veins?
Large veins - 3 generic layers - absence of the elastic fibres - dominated by collagen
Medium sized veins - some smooth muscle
Venules - thin walls - tunica externa around the endothelium
What are the venous valves?
Folds of the Tunica intima
Prevents blood flowing backwards
Compression of veins pushes blood towards the heart
When walls of veins near the valves weaken varicose veins occur
