Vascular History and Diseases Flashcards
What does the innermost layer of a blood vessel consist of?
(tunica intima)
endothelial
subendothelial
elastic/fenestrated
which layer of intima directly contacts blood?
endothelial
what separates the endothelium from subendothelium?
basement membrane
what comprises the subendothelial layer?
delicate connective tissue and scattered stromal cells
what is the elastic/fenestrated layer?
membrane consisting of elastic fiber network
what forms the bulk of tunica intima?
elastic/fenestrated layer
what does the thickness of the elastic/fenestrated layer depend on?
type and size of vessel
what does the tunica media consist of?
concentric layer of SM cells and ECM
what does the thickness of SM cells of the tunica media depend on?
type and size of vessel
What does the SM cells of the tunica media produce?
ECM
What are the main functions of the tunica media?
conduct blood
control peripheral vascular resistance and maintain hydrostatic pressure
what is the tunica adventitia?
connective tissue layer surrounding blood vessel
What does the tunica adventitia consist of?
collagen, elastic fibers, vaso vasorum, and nerves
What is the function of vaso vasorum?
supplies nutrients to media and outer layer of larger blood vessels
What is the function of nerves of tunica adventitia?
regulate vascular muscle tone
What are special characteristics of adventitia?
vascular healing and pathology
Where does the inner layer of blood vessels receive nutrients?
directly from lumen
Which vessel has the greatest cross-sectional area?
capillaries
Describe blood velocity in vessel types
fast –> slow –> fast
arteries –> capillaries –> veins
what forms the bulk of elastic arteries’ wall?
media (1/3 SM cells and 2/3 concentric elastic tissue layers)
What maintains blood pressure during diastole?
elastic arteries
examples of elastic arteries
aorta and pulmonary trunk
Describe the structure of muscular arteries
prominent media with well-formed internal and external elastic lamina
function of larger muscular arteries
distributing arteries
function of smaller muscular arteries
resistance arteries
media of larger muscular arteries
3/4 of wall thickness
how many layers of SM cells do smaller muscular arteries have?
3 to 25
what determines blood pressure in muscular arteries?
peripheral vascular resistance
What determines peripheral vascular resistance?
muscle tone (contraction) in small muscular arteries and arterioles
What factors affect muscle tone?
- ANS
- circulating hormones
- local, endothelial-derived vasoactive mechs
describe arterioles
30-400 microns in diameter
1-2 SM layers
What is the main site of blood pressure regulation?
arterioles
small changes in muscle tone induce –
large changes in resistance
functions of arterioles
- regulate bp
- redistribute blood
- shunt blood
what is the function of metarterioles?
connect arterioles and capillaries
– constrict to reduce or shut off blood flow to their respective capillaries, shunting blood elsewhere
precapillary sphincter
capillaries’ caliber
5 microns
Describe capillaries
single layer of endothelial cells, basement membrane and pericytes
what are pericytes?
contractile cells that reside outside of the basement membrane
Most common type of capillary found in skeletal muscle, cardiac muscle, brain, skin, lung, exocrine glands
continuous capillaries
How does endothelial cells’ function helpful for continuous capillaries?
Endothelial cells have no fenestrae and are anchored together by tight junctions, which prevent diffusion between cells.
describe and give the function of fenestrated capillaries
Have fenestrae (60-80 nm in diameter) with or without diaphragms that allow relatively free passage of substances
where are fenestrated capillaries found
renal glomeruli, endocrine glands, and intestinal villi
describe sinusoid/discontinuous capillaries
Large diameter, discontinuous endothelial layer, and discontinuous basal lamina
what are usually within the vicinity of sinusoid?
macrophages
what does veins and venules mostly function as?
reservoir vessels
Describe Post-capillary venules
Appear similar to capillaries except wider lumens and more pericytes
Discontinuous elastic lamina with relatively thick adventitia
Preferential site for WBC migration
Post-capillary venules
what happens when venules become larger
fewer pericytes and more smooth muscle to form muscular veins (not as thick as arteries)
describe the adventitia of veins and venules
thick but no well-defined internal and external elastic laminae
how do veins maintain unidirectional flow?
valves
function of lymphatic vessels
removes excess interstitial fluid and immune cells to lymph nodes
describe lymphatic vessels
Larger vessels have thin muscle layer and adventitia
Have blind ends and valves
Similar histologically to veins except have no RBC
what is an aneurysm?
localized dilation of vessel or heart
true aneurysm
All 3 layers of the arterial wall (or heart)
what is a false aneurysm?
contained rupture
what is a contained rupture/false aneurysm?
Transmural tear of vessel wall and blood clot formation in the perivascular soft tissue.
histological features of aortic aneurysm
atherosclerosis and medial degeneration
Most common pre-existing histologic finding in aortic dissection if present
medial degeneration
Describe a medial degeneration
elastic tissue is fragmented
medial degeneration may indicate –
collagen vascular disease (Marfan syndrome, Loeys-Dietz syndrome, Ehlers-Danlos, syndrome, familial thoracic aortic aneurysm & dissection)
other causes of aortic aneurysm
Infections (AKA mycotic aneurysms)
Traumatic
Inflammatory (e.g. vasculitis, syphilis)
Congenital defects (e.g. berry aneurysms)
Most common atherosclerotic aneurysm
abdominal aortic aneurysm
prevalence of abdominal aneurysm
Rare before age 50 years and more frequently seen in men
where does abdominal aortic aneurysm occur?
below renal arteries and above aortic bifurcation
abdominal aortic aneurysm: Complicated atherosclerotic plaques result in –
destruction and thinning of aortic media
what partially or completely fills abdominal aortic aneurysm?
thrombus (blood clot)
complications of aneurysms
rupture –> hemorrhage
vascular obstruction
atheroembolism
compression of adjacent structure
what is a dissection?
A partial tear within the wall of a blood vessel
what does dissection allow for?
blood to separate the layers of the media
intimal tear
inner 2/3 of media separated from outer 1/3 creating 2 lumens (passages w/in vessel)
what is the false lumen created by a dissection?
new space within the wall of the artery
what is aortic dissection?
passage of blood within the media, which often ruptures outward causing massive hemorrhage
who does aortic dissection affect?
> 90% occur in men between ages of 40 and 60 years with history of hypertension
younger patients with systemic or localized connective tissue disorder that affects aorta
name other predisposing factors of aortic dissection
pregnancy and iatrogenic
aortic dissection type A
involves ascending aorta
aortic dissection type B
involves descending aorta only
which type of aortic dissection requires medical emergency?
type A
aortic dissection based on site of intimal tear
DeBakey
aortic dissection based on site of dissection
Stanford
