5. Blood Vessels Flashcards
What are the 3 concentric layers of blood vessels?
Intima
media
adventitia
The intima is a single layer of endothelial cells. The media contains well organized layers of smooth muscle in arteries, which are organized haphazardly in veins. The adventitia contains?
loose connective tissue containing nerve fibers and vaso vasorum (vessels of the vessels)
There are elastic arteries (aorta), muscular arteries (coronary), and arterioles (tissues/organs) which are the principal point of?
physiologic resisitance to blood flow, since halving the diameter increases resistance 16 fold
BP control
Capillaries are small with no media and have pericytes which contract. Veins contain how much total blood volume?
2/3 total blood volume
What do arteries have that differentiates them from veins, among other characteristics?
internal elastic lamina (these are what break and dilate, causing aneurysms.
What are the 3 vascular anomalies?
aneurysms
arteriovenous malformations (AVM)
Fibromuscular dysplasia
What is a localized abnormal dilation of a blood vessel of the heart, which is not present at birth but develop over time due to underlying defect in the media of the vessel?
Aneurysms
Arteriovenous malformations shunt blood from arteries to veins without going through capillaries. What type of channels are present with prominent ulsatile ateriovenous shunting with high blood flow?
tangle, worm-like
**leads to high output cardiac failure
What is a focal irregular thickening in medium and large muscular arteries (renal carotid, splanchnic, and vertebral) which can be a developmental defect or from trauma?
fibromuscular dysplasia
What type of aneurysm is seen in the circle of willis and in AD polycystic kidney dz, with 90% of saccular aneurysms being found near branch points of anterior circulation in the circle of willis?
berry (saccular) aneurysms
Berry aneuryms are the most common cause of subarachnoid hemorrhage (SAH). 1/3 occur due to increased ICP (sex/stool). What is the most common location in the circle of willis?
anterior communicating artery, then MCA
What may originate from the following?
- embolization of septic embolus d/t infective endocarditis
- extension of a suppurative process
- organisms infecting the arterial wall
Mycotic aneurysms (d/t infected artery)
AVMs can result from reupture of aneurysm into vein, injuries that pierce A/V, or from inflammatory necrosis. Why would a procedure be done to make an AVM?
Ateriovenous fistulas provide vascular access for chronic hemodialysis
Fibromuscular dysplasia’s focal irregular thickening is common in young women and increased incidence if have first degree relative. What can occur and be seen if it occurs in renal arteries?
Renovascular hypertension
string of beads can be seen on angiography d/t attentuation of adjacent media
vascular injury associated with endothelial cell dysfunction or loss, stimulates smooth muscle cell recruitment and proliferation and assocaited matrix synthesis, ULTIMATELY resulting in?
intimal thickening
What are motile, undergo cell division, and acquire new biosynthetic capabilities?
neointimal smooth muscle cells
*can return to normal but results in intimal thickening
What is the initial event following vascular injury?
endothelial cell activation
Sustained BP over 139/89 is associated with increased risk of athersclerosis. What are the three types of HTN?
secondary
essential
malignant
5% of the population has secondary HTN, d/t underlying renal or adrenal dz (cushings/pheochromacytoma). HTN secondary to renal artery stenosis is caused by?
increased production of renin from the ischemic kidney
*bruit can be heard
Essential HTN is idopathic and 95% have this. It can lead to cardiac hypertrophy (left ventricular) and failure, multi infarct and renal failure. Who is more likely to have idopathic HTN? 2
vulnerability increases with age
african americans
Malignant HTN is when BP is 200/120 consistently, causes death in 1-2 years. What are 3 symptoms associated with it?
Severe HTN
Renal Failure
Retinal hemorrhage/exudate +/- papilledema
What is a function of cardiac output and peripheral vascular resistancem both of which are influenced by multiple genetic and environmental factors?
Blood pressure
Blood volume and vascular tone are modified and maintained by renin-angiotensin-aldosterone system (RAAS). In states of low volume or low peripheral resistance or decreased GFR, what occurs?
renin is released by juxtaglomerular cells in afferent arterioles in the kidneys
Renin cleaves circulating angiotensinogen to form angiotensin I. AGT1 is cleaved to form AGTII via?
ACE angiotensin converting enzyme
AGTII is potent but short lived vasoconstrictor. AGTII stimulates adrenal cortex to release aldosterone, causing?
renal absorption of sodium and water
AGTII is potent but short lived vasoconstrictor. AGTII stimulates adrenal cortex to release aldosterone, causing?
renal absorption of sodium and water
Since the kidney is absorbing sodium and water, resisitance and volume increase, raising blood pressure. The volume expansion induces myocardial release of atrial natriuretic peptide, which does what?
leads to Na+ excretion and diuresis, as well as vasodilation — lowering blood pressure
Hypertension affects 30% of adults in the US, prevalence of HTN increases with age and being african american. HTN is a major risk factor for? 3
atherosclerosis
CHF
renal failure
HTN is controlled by a single gene disorder or is secondary to renal, adrenal or other endocrine disorders. Sustained HTN requires participation of?
The kidney
primary hyperaldosteronism is MC secondary cause HTN
HTN causes degenerative changes in the walls of large and medium arteries that can lead to aortic dissection and or cerebrovascular hemorrhage. What are the two forms of SMALL blood vessel dz?
Hyaline arteriolosclerosis
Hyperplastic arteriolosclerosis
Hyaline arteriolosclerosis causes increase in smooth muscle matrix synthesis and shows what, causing luminal narrowing?
homogeneous pink (hyaline) thickening of the vessel wall
In nephrosclerosis due to HTN, arteriolar narrowing of hyaline arteriosclerosis causes diffuse impairment of renal blood supply and?
glomerular scarring
Hyperplastic arteriolosclerosis occurs in severe HTN, smooth muscle cells form _____ which leads to luminal narrowing.
concentric lamellations (onion skinning)
In malignant hypertension laminations are accompanied by fibrinoid deposits and vessel wall necorsis in the kidney called?
necrotizing arteriolitis
a Granular arteriolosclerotic kidney can be seen in benign HTN along with hyalinization or onion skinning of the arteriole. What can be seen in malignant HTN?
Numerous variegated hemorrhages and necrosis of glomeruli
Arteriosclerosis is when the arterial wall thickens and losses elasticity. While arteriolosclerosis may cause down stream?
ischemic injury (hyalinization/hyperplastic changes)
What occurs in people older than 50, with calcification of muscular arteries, internal elastic membrane involved, but no narrowing of the lumen and no clinical significance?
Monckeberg medial sclerosis
What is known as gruel and hardening; the most frequent and clinically important pattern?
Atherosclerosis
Atherosclerosis underlies the pathogenesis of coronary, cerebral, and peripheral vascular dz. It causes more morbidity and mortality than any other disorder. What is responsible for 1/4 of all deaths?
myocardial infarction
Atheromas or atherosclerotic plaque is a raised lesion with a soft grumous core of lipid covered by a fibrous cap. Besides obstructing flow, what else can this do?
plaques can rupture and cause obstructive vascular thrombosis
Plaques also increase the diffusion distance from the lumen to the media, causing ischemic damage resulting in?
weakening of the vessel wall and possible aneurysm formation
Athromas have a fibrous cap in the intima which contains smooth muscle cells, Mø, foam cells, collagen, elastin and neovascularization. What can be found in the necrotic center? 3
cell debris
- cholesterol crystals (cleffs)
- *foam cells - foamy mø
(men) 40-60 y/o have 5x increased incidence, with multiple risk factors having synergistic effects. What is said about atherosclerosis and premenopausal women?
They are protected, postmeno estrogen is not proven to help
Hypercholesterolemia is a risk factor for atherosclerosis. Metabolic syndrome (central obesity) conditions such as insulin resistance, HTN, dyslipidemia (high LDL low HDL), hypercoagulobility and pro inflammatory state may contribute to?
endothelial dysfunction and or thrombosis
What is the MCC of left ventricular hypertrophy?
What is the most important risk factor for atherosclerosis?
Chronic HTN
Family history
What is the simplest and most sensitive marker of inflammation?
C reactive protein CRP
CRPs expression is increased by a number of inflammatory mediators, (IL6) and it augments innate immune response by binding to bacteria and activating?
classical complement cascade
more CRP= inc. risk of MI, stroke, sudden cardiac death
The response to injury model views atheroslcerosis as a chronic inflammatory and healing response of the arterial wall to endothelial injury. The two most important causes of endothelial dysfunction are?
hemodynamic turbulence and hypercholesterolemia (circulating lipids)
hemodynamic turbulence occurs at openings of exiting vessels, branch points and what?
posterior abdominal aorta
Lipids in atheromatous plaques are predominantly cholesterol and cholesterol esters which accumulate in the intima and are taken up by?
macrophages and partially oxidized
The modified lipid.LDL accumulates within mø and smooth muscle cells forming what, and a lesion known as a fatty streak?
foam cells – this stimulates an inflammatory response to accumulation of this toxic form of LDL
List the steps in the response to injury hypothesis (5)
- Chronic endothelial injury (hyperlipidemia)
- Endothelial dysfunction (inc. perm = monocyte adhesion and emigration)
- Macorphage activation/SM recruitment
- Mø and SM cells engulf lipids = Foam cell
- SM prolife, collagen/matrix deposition
Chronic inflammation contributes to the intiation and progression of atherosclerotic lesions. Accumulation of cholesterol crystals within mø recognized by the inflammosome leads to what secretion?
IL1, more mø and T cells are recruited and activated at the site
Smooth muscle proliferation and matrix deposition leads to atherosclerosis as well. Several growth factors are implicated in the proliferation of SM, including PDGF, fibroblast growth factor and?
TGF-a
SM cells synthesize ECM and collagen. Due to intimal expansion from foam cells and extracellular lipids, inflam cells, SM cells, and increased ECM, what is formed?
antheromatous plaque!
From most frequent/severe sites of athersclerosis to least: abdominal aorta, coronary arteries, popliteal, ICA, and circle of willis. What are 4 complications of atherosclerotic plaques?
rupture and ulceration (thrombosis)
hemorrhage into plaque
Embolism
aneurysm formation
What are fatty streaks composed of?
lipid filled foamy macrophages
Consequences of atherosclerosis include stenosis of the arterial lumen with continuously growing plaques. The lumen of the affected vessel shrinks, leading to ischemia a point known as ?
critical stenosis where approx 70% of the vessel is occluded leading to chronic ischemia
An acute thrombus may form over the plaque, occluding the artery. This may occur secondary to rupture of the plaque or?
erosion or ulceration of the plaque surface (or hemorrhaging into the atheroma expanding its volume)
There are vulnerable and stable plaques determined by the amount of collagen in the fibrous cap, which is continuously degraded and resynthesized. What can degrade the cap?
inflammation degrades the cap and inhibits resynthesis= dec in collagen = weak cap
Changes in BP and vasoconstriction can cause plaque rupture as well. if ruptured, they can form atherosclerotic debris (cholestrol emboli) causing?
partial or complete vascular occlusion when it reaches a vessel small enough
what is a localized abnormal dilation of a blood vessel or the heart that may be congenital or acquired?
Aneurysm
What is an intact but thinned muscular wall at the site of dilation, either saccular or fusiform?
True aneurysm
What is a defect through the wall of the vessel, communicating with an extravascular hematoma that freely communicates with the intravascular space… PULSATING HEMATOMA?
False aneurysm or pseudo-aneurysm
What arises when blood enters a defect in the arterial wall and tunnels between its layers, for example, between intima and media?
dissection
An aneurysm may occur whenever the connective tissue of the wall is weakened either acquired or congenital. What is an example of defective vascular wall CT? 2
Marfan syndrome (defective fibrillin synthesis) Ehler danlos
Aneurysms may also occur due to degradation of vascular wall CT via inflammatory conditions such as atherosclerosis leading to increase MMP. What are three ways the vascular wall is weakened by ischemia?
atherosclerosis (ischemia inner media)
HTN (ischemia of outer media)
** Tertiary Syphillis (ischmeia of outer media - thoracic aorta) **
Obliterative endarteritis (late stage syphillis) shows a predilection for small vessels including the vasa vasorum of the thoracic aorta. This leads to ischemic injury of the aorta media and?
aneurysmal dilation which involves the aortic valve annulus == aortic valve regurgitation
loss of vascular wall elastic tissue or ineffective elastin synthesis leads to what?
cystic medial degeneration (disorganized elastin, inc. ground substance)
cystic medial degeneration is a final common result of different conditions including ischemic medial damage and?
marfans syndrome
What are the two most important causes of aortic aneurysms?
athersclerosis (AAA) and hypertension (ascending aortic)
What can originate from septic emboli (d/t infective endocarditis), and extension of a suppurative process or circulating organisms directly infecting the arterial wall?
Mycotic aneurysms
What can be seen in cystic medial degeneration?
elastin fragmentation and areas devoid of elastin that resemble cystic spaces but are actually fillled with proteoglycans
AAA is due to athersclerosis in the abdomen below the renal arteries before the bifurcation, and often involve the iliac arteries. More frequent in? 3
men
smokers
6th decade of life
AAA are characterized by severe athersclerosis covered with mural thrombi. Sometimes detected as a pulsating mass and bruit. Complications include occlusion of arteries and downstream ischemia and was else? 3
rupture and hemorrhage
embolism
impingement of another structure
If a younger patient presented with back pain and elevated inflammatory markers (CRP) what can one expect?
Inflammatory AAA (5-10%)