L29-structure Of Blood Vessels Flashcards
What are the 3 layers of blood vessels
Tunica intima Inner most layer Tunica media Middle layer Tunica adventitia Outer most layer
Describe the tunica intima
▪️Endothelial cells provide a physical barrier between blood and rest of blood vessel wall
What is an important step in development of atheroma
Disruption Of endothelial layer in tunica intima
Describe the tunica media
▪️two layers of elastic tissue:internal and external elastic laminae
▪️smooth muscle
▪️source of mechanical strength for blood vessel and as it contains sm the means by which the diameter of the vessel can be altered
Describe the tunica adventitia
▪️layer of CT
▪️serves to hold Bvs in place
▪️contains vasa vasorum
Describe the arteries
High pressure side of circulation Contains about 12% of total blood volume Classified in to: 1-large arteries(elastic) 2-small arteries(muscular) 3-arterioles
Describe large arteries
Aorta and its major branches
Distensible=elastic
Play little role in regulation of peripheral circulation
What does the wall of large arteries contain
1-fibrous tissue(collagen) which provides strength and inc with age
2-elastic tissue which is inflated by entry of additional blood during systole
3-smooth muscle(less than small arteries)
What is the windkessel effect
Large arteries are inflated by entry of additional blood in systole
During diastole when blood is no longer entering the arteries they recoil and help to maintain peripheral tissue perfusion
Describe small arteries
Radial artery,cerebral and coronary
More smooth ms than large
Poses a considerable resistance to blood flow
Some involvement in circulatory control mechanisms
What does wall of small arteries contain
Smooth muscle Fibrous tissue(less than large) Elastic tissue(some)
Describe arteriols
Smooth muscle is a major component of vessel wall
Resistance vessels
1-major sure for regulation of distribution of blood flow
2-arterial blood pressure regulation
3-pulsatile blood flow is smoothed out to a constant pressure
What is the pre capillary sphincter in arteriols
Small cuff SM at entrance to a capillary bed
When sphincter is closed capillary is not perfused with blood
In resting 90% are closed
No nerve supply but are regulated by local metabolite concentrations
Describe capillaries
▪️Site of exchange of nutrients and waste products between circulation and interstitial fluid surrounding cells
▪️6% of blood vol
What is the bolus flow
Volume of trapped plasma in between successive red cells
What is capillary formed by
Tube is made up of a single layer of endothelial surrounded by BM
Pores and clefts present
Pericyte around endothelium
What are the types of capillaries
Continuous
Fenestrated
Discontinuous
Describe cont cap
Location:lung,skin,muscular tissue, adipose,nervous,brain
Endothelial cells held together by tight junctions
Bm is cont and consists mainly of collagen
Larger molecules exist via caveolae which cover both surfaces of endothelial cells
Describe fenestrated cap
Location:tissues that have high transcapillary water flux
1-glomerulus of kidney
2-intestinal villi
3-choroid plexus of brain
Fenestrae are not completely open holes but are covered by a very thin diaphragm derived from the glycocalyx
14 wedgeshaped gaps
Intact BM
Describe discont cap
Location:bone marrow, liver, soleen
Gaps in between adj endothelial cells
Incomplete BM
What are the 3 types of veins
Large(vena cava)
Small(most named veins)
Venules
Describe venules
Wall is made of endothelial+small amounts of fibrous tissue+incomplete layer of sm
Capillaries and venules are imp site for movement of water and nutrients
Describe small veins
Wall:collagen+elastic+smooth ms(less than small arteries)
Distensible
45% of total blood vol
What are the mechanisms of venous return and prevention of venous pooling
1-have effective venoconstrictor sympathetic nerve supply
2-have valves
Describe large veins
Wall is made of excess collagen+some elastic+smooth Ms
15% of total blood vol
Function of pericytes
Provide support
Contractile
