Vascular Disease/Atherosclerosis Flashcards
Arterial Vascular Organization
Large Elastic Arteries
Medium Muscular Arteries
Small Arteries
Large Elastic Arteries
Aorta, iliac, and Pulmonary arteries
- Elastic fibers throughout the media
- Expands during systole to store energy
- Contract during diastole to propel blood
Medium Muscular Arteries
- Media is primarily muscle cells
- Elastin limited to internal and external elastic lamina
- Regional blood flow regulated by expansion/contraction
- Controlled by autonomic nervous system and pH
Small Arteries (<2mm) and Arterioles (20-100um)
- Media is primarily smooth muscle cell
- Arterioles control blood flow resistance
- Resistance ot fluid flow is inversely proprotional to 4th power of diameter ( cutting the diameter in half increase resistance 16-fold)=> small changes in arteriolar lumen size have major effects on bp
Aortic Anatomy
- Aorta thick vessel. Elastic material thoughout the media to store E of systole for use during diastole
- Oxygen diffuse to inner layer: advetita and outer media fed bby vasa vasorum
- Endothelium on ALL vessels is nonthrombogenic and resists adhesion of platelets and leukocytes (controls. adherance and passage of materials)
Structure of Medium Artery
- Tunica media; most prominet layer
- Less elastic material compared to aorta
- All interior and exterior elastic membrane to be seen clearly
Structure of Small Artery (arteriole)
- Wall bend into surrounding tissue
- 5 or fewer layers of smooth muscle around small artery
Capillary Vessels
- Have a diameter of 7-8 um
- Lined with endotherlial cells and partially surrounded by smooth muscle cells called PERICYTES
- Very slow rate of blood flow and thing walls => this favor rapid exchage of diffusible substance between tissue and blood
- BP ranges from 35mmHg entering and 10mmHg at the end; Average is 18mmHg
- Diffusion fo oxygen and nutrient not efficient beyond 100 um so the capillary network is very extensive
- Capillary density is highest in metabolically active tissue (and brain)
Venous System
- Venules (site of diffusion and leakage) collect blood from capillaries and anastomose to form larger venules and then vains
– Leakage of fluids (edema) and leukocyte emigration occurs at the level of venules - Veins have larger diameters, larger lumena and thinner less distinct walls than comparable arteries reflecting lower pressure.
– More prone to dilation (pressure is low so they dilate even when bp is low), collapse/compression, and tumor invasion than arteries
– Have valves that prevent backflow of blood
Collectively, the venous system has enormous capacitance; 2/3 of blood is in the venous system
Veins
- Medial layer (tunica media) is not prominent nor abundant
- Vein recoil is not as quick as artery recoil after distention.
- As veins and arteries travel together. The vein size will look larger because it is streached out
- Valve regulate the one way flow of blood. (fold of tunica intima -eg., endothelial outcroppings folded back on themselve)
- For deep veins in the legs, muscle contraction assist the blood flow back to heart
Arteries Vs. Veins
Artery: Muscularus is much thicker
Vein: Lumen is thicker, and it got a valve
Lymphatic system
- Thin-walled endothelium channels drain lymph (water, electrolytes, glucose, fat, protein, inflammatory cells) from interstitium of tiissues
- Lymph channels eventually connect with blood stream via THORACIC DUCT (drained upward, dump w/veinous system at neck)
- Lymph channel common conduit for movement of malignant cells and infectious microbes
Functions of Lymphatic System
- Retrieve protein that have escaped from capillaries into the interstitial fluid.
– This allow the interstitial colloid pressure to remain low and limit interstitial edema (third spacing => edema forms) - Absorb fat from small intestine. small intestinal lymphatics are called LACTEALS, they absorb ffat and fat souble vitamins and deliver them to the general circulation
- Immune regulation and surveillance.
– Due to high permeability (thin walls) of lymphatic capillaries, the bacteria and other microorganism enter lymph system and are transported to lymph nodes, where immune and inflammatory cells may act on them
Where do Lymphatic vessels run
They run along side veins and arteries
- Lymphatic vessels have lymph nodes, their walls are thinner than veins , they have valves for unidirectional flow
Lymphatic system (composition)
Lymph composed of:
- Water
- Protein that are too large to be reabsorbed (mosltly albumin)
- Foreign substances
Lymphatic veins drain into => right lymphatic duct and thoracic duct. These drain lymph into => the left and righ subclavian veins
Disease of Vasculature
Disorders of arteries:
- Artheriosclerosis: most common - can cause coronary artery disease, peripheral vascular disease, strokes, aneurysm (hardening of arteries)
– account for than half the death in US
– Three distinct morphological types
- Hypertension: BP mis-regulation that lead to adverse structural alteration of the arteries (related to artheriosclerosis)
- Aneurysm
Disorders of Arteries and veins:
- Thrombosis: hemodynamic disorder altering vessel structure
Disorders of veins:
- Varicose veins
- Thrombophlebitis (infectious vein that favor arteriosclerosis)/Phlebothrombosis (presence of clot that cause disease)
Arteriosclerosis
Atherosclerosis: most common and most IMPORTANT form of arteriosclerosis
Arteriolosclerosis: Affect small arteries and arteriolesl cause ischemia. (small hardening)
- The Two variant (hyaline and hyperplastic arteriolosclerosis) are associated with hypertension.
Monckebery medial calcific sclerosis: Characterized by calcium deposit in media and internal elastic lamina of muscular arteries (radial, ulnar, uterine) of individuals over 50 years.
- It does not reduce on the vessel of lumen
Fibromuscular intimal hyperplasia: non atherosclerotic thickening of smooth muscle cells in arteries that had been injured, inflamed, or immunologically injured
Atherosclerosis
Cause of most morbidity and mortality
- Characterized by formation of intimal lesion (atheromas) that narrow lumen and can cause sudden occlusion when rupture
- Atheromas weaken vessel wall, leading to aneurysm formation
- Condition begins early in life as fatty streak regardless of risk factors. Present in all children by 10 but not all will turn into atherosclerosis
Atherosclerotic Plaques:
Intimal thickening and lipid accumulation representing disease progression (blood vessels lose laminar flow and become turbalant)
Atherosclerosis: risk factors
- Multiple constitution: genetics, gender, and age
- Modifiable: Hypertension, hemodynamic disturbances, hypercholesterolemia, smoking, diabetes omega-3 fatty acids
These interact in multiplicative manner to enhance the effect of each
Atherosclerosis: Vessels Involved
Infra-renal abdominal aorta
Coronary arteries
Popliteal arteries
Cicle of Willis in brain
Strongly associated with regions of vascular turbulence, particularly at orgin or branches of vessels (slow progression)
Pathogenesis of Atherosclerosis
Response to injury hypothesis is most widely held. It view atherosclerosis as chronic inflammatory response of the artery wall to endothelial injury
1) Endothelial injury, resulting from hemodynamic disturbance or hypercholesterolemia, leading to increased permeability and leukocyte adheasion
2) Accumulation of lipoproteins (primarily LDL and Cholesterol) in sub-intima
3) Monocyte infilreation to endothelium, migration to intima, differentiation to macrophages (in tissues) and foam cells
4) Lipid accumulation within macrophages, => response by releasing inflammatory cytokines
5) Smooth muscle cell recruitment and proliferation and production of extracellular matrix
6) Plaque may weaken vessel wall, narrow vessel lumen, clacify, form thrombi or (worst case) rupture causing acute occlusion
Atheroma
Once formed is irreversible
Endothelial Injury (basemnet embrance becomes expose)
- Injurous agents will be released => monocytes adhere => Monocytes pass intima (macrophages ingest lipids)
- Altered surface => (Monocytes adhere) + Platelets adhere => growth factor relased => smooth muscle proliferation + connective tissue deposition + lipid synthesis
- Increased permeability => Increased libid in intima
There last step in each will all come together and FORM ATHEROMA
What is the first step in atherogenesis
Formation of fatty streaks (pale yellow streaks that run along the intima from accumulation of macrophages that store fat in their cytoplasm)
- Do not develop into plaques in thoracic aorta
Atherosclerosis Timeline
Foam Cells => Fatty Streaks => Intermediate Lesion => Atheroma => Fibrous Plaques => Complicated Lesion/Rupture (irreversible)
Vessel Wall Atherosclerosis Complication
The damage happen from
- Calcification (complex lesion)
- Hemorrhage
- Tunica Media Destruction (thinning)
- Ulceration
Atherosclerosis; Endothelial Surface
1) Damage to cells
2) Permeability to LDL (cholesterol- VLDL traffic lipid into cell)
3) Adherence and entry of monocytes into intima