Vessel structure Flashcards
Tunica intima
Single layer endothelial cells
Lining in heart
These cells can secrete paracrines that regulate blood flow
Elastica interna
Made of elastin that are capable of stretch and recoil
Tunica media
Smooth muscle (contraction and relaxation changes vessel radius)
Contraction vs relaxation
Vasoconstriction, vasodilation
Elastica externa
Layer of elastin
Tunica externa
Outer layer of connective tissue
Arteries:
Thick walls w/ lots of elastic tissue
Large elastic arteries like aorra have very large diameters (radii)- aka little resistance
arteries are a pressure reservoir that helps maintain:
i) the driving force of blood during venticular diastole (relaxation)
ii) the constant flow of blood toward capillaries
Why are arteries walls thick and elastically
So it can expand when blood is expanding but also maintain pressure (passive elastic recoil that occurs pushing blood downstream)
Arterioles (walls and functions)
Think walls w/ little elastic and lots of smooth muscle innervated by sns
Functions:
1. Help maintain mean arterial pressure (MAP)
- Determines the relative blood flow to individual organs through vasocons/dial
- Eliminates flow/pressure changes in capillaries
Innervation to sns and smooth muscle progressively decrease In arteries…
As they get closer to capillaries
Capillaries
Most numerous, and smallest/thinest
Single layer endorhelial cells surrounded by thin glycoprotein/collegan (basement membrane)
Function=exchange
Highly permeable to small soluble substances
Capillaries 2 different classes (levels of exchange):
1) continuous capillaries:
Cells connected by leaky junctions
2) fenwstrated capillaries: large junctions between cells and large channels (pores) passing through cells
Found in kidney, bone marrow and liver (in liver and bone marrow= discontinuous)
Veins (structure)
Thin walled, high complience vessels (expand easily w/ increasing pressure)
Contains less smooth muscle and elastic but more collagen (connective tissue) than arteries
Veins functions
1) low resistance (high complience): large cross sectional area= low velocity= pooling of blood
2) volume resorvior: hold much greater blood than veins even w/ lower pressure
Constriction of veins vs dilation
Prevents blood from pooling and increase venous return.
Dilation= pooling (opp)
