Circulatory system Flashcards
Large elastic artery function
conducting
Location of large elastic artery
closest to heart
Tunica intima structure of LEA
endothelial cells w thin subendothelium of CT and discontinuous elastic laminae
Tunica Media structure LEA
4-70 fenestrated elastic membranes w smooth muscle cells and collagen btwn lamella
Thickest part of elastic artery?
Tunica media
Tunica Adentitia LEA
thin CT layer containing lymphatics, nerves and vasa vasorum
Distributing artery
Medium muscular artery
function MMA
distribute blood to sub-regions of body
T.intima MMA
endothelium, subendo and thick elastic lamina
T.Media MMA
~40 layers smooth muscle connected by gap junctions
gap junction in TM MMA allow
coordinated contraction
T.Adentitia MMA
thin CT layer containing minor vasa vasorum, lymphatics and nerve fibres
Arterioles function
microcirculation. carry blood to metarterioles
structure arterioles
diameter less than 0.1mm
3 layers smooth muscle cells
no internal elastic lamina
metarterioles function
supply capillary beds
structure metarterioles
precapillary sphincters- intermediate rings of smooth muscle control blood flow
Veins structure
larger diameter and thinner wall. more CT less elastic and muscle fibres
small/medium veins structural features
well developed TA, thin TM and TI
large veins structural features
diameter over 10mm, thicker TI. well developed longitudinal smooth muscle
Venules function
continuous with postcapillary venules, unite to form a vein
Venules structure
endothelium assoc with pericytes, form thin wall.
diameter up to 1mm.
contains valves
pericytes
thin smooth muscle cells
postcapillary venules function
receive blood from capillary beds, empties into venules.
surrounding tissue drains in due to lower pressure than cap and venules
site of wbc migration due to permeability
structure postcap venules
endothelial lining assoc w pericytes
diameter 10-30 micrometres
capillary structure
one layer endothelium and basement membrane.
short diff pathway
3 types of capillary
continuous, fenestrated, sinusoid
continuous capillary
complete lining, diffusion water, small and lipid soluble molecules
specialised in cns and thymus
fenestrated capillary
pores in endothelium, rapid water and larger solutes exchange
sinusoid capillary
gaps btwn adj endothelial cells. free transfer of water and large plasma proteins
phagocytes monitor gaps.
arteriorvenous anastomosis
connection btwn two blood vessels.
Tunica intima characteristics
inner layer.
encompasses endothelial lining
in arteries only- stretch and recoil to cop with changes in pressure
why does TI encompass endo lining
reduce friction
endothelium characteristics
internal walls of bv
reduce friction, continuous with artery/vein endothelium
function of endothelium
release vasoactive substances affecting vascular tone, blood pressure and blood flow.
vasodilation/constriction
maintain vascular homeostasis
vasodilators released by endo
nitric oxide- released by mechanical stress
vasoconstrictors released by endo
endothelin
Tunica Media characteristics
smooth muscle and loose CT
CT- elastic fibres in artery, collagen in vein
encircles endothelium, lines lumen of bv
binds to inner and outer layers
artery TM contains
external elastic membrane seperating TM from TE
Tunica Externa characteristics
contains collagen, elastic fibres, vaso vasorum
in veins- cont smooth muscle cells
function of TE
anchors vessel to adj tissues
3 types of artery
- elastic/ conducting
- muscular
- arterioles
function elastic artery
conduct, maintain pressure
function muscular artery
less recoil, distribute
function arterioles
regulate pressure
venous valves made of
TI folds
function of valves
prevent backflow
skeletal muscle pump
muscles create constriction on veins of muscles => valves open superior to contracting muscle, valves close inferior to contracting muscle