Examples of vascular resistance in the following topics:
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- They are the primary site of vascular resistance.
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- Resistance to flow must be overcome to push blood through the circulatory system.
- If resistance increases, either pressure must increase to maintain flow, or flow rate must reduce to maintain pressure.
- Numerous factors can alter resistance, but the three most important are vessel length, vessel radius, and blood viscosity.
- With increasing length, increasing viscosity, and decreasing radius, resistance is increased.
- The resistance offered by peripheral circulation is known as systemic vascular resistance (SVR), while the resistance offered by the vasculature of the lungs is known as pulmonary vascular resistance (PVR).
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- When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance.
- When blood vessels dilate, the flow of blood is increased due to a decrease in vascular resistance.
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- With the first breaths, there is a fall in pulmonary vascular resistance and an increase in the surface area available for gas exchange.
- These two changes result in a rapid redirection of blood flow into the pulmonary vascular bed, from approximately 4% to 100% of cardiac output.
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- Key muscle groups and the associated vascular and
nervous systems can also be separated from other tissue, such as in the
upper arm.
- Muscle fascia is predominately composed of
cross-linked collagen and elastin fibers oriented parallel to the direction of
muscle force, making them able to resist high-tension forces while remaining somewhat elastic.
- Each individual fiber within a fascicle is
surrounded by a thin connective layer termed the endomysium, which
helps maintain close association between the muscle fiber and associated
vascular and nervous systems.
- It also maintains
the close association of the vascular and nervous system with the
muscle, which is required to deliver necessary metabolites and nerve impulses.
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- Venous pressure is the vascular pressure in a vein or the atria of the heart, and is much lower than arterial pressure.
- Venous pressure is the vascular pressure in a vein or the atria of the heart.
- This value is a function of the cardiac output (total blood pumped) and total peripheral resistance (TPR).
- TPR is primarily a function of the resistance of the systemic circulation.
- The latter can actively contract, reduce diameter, and increase resistance and pressure.
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- Clinical studies on mammals have shown that porous metals, such as titanium foam, may allow the formation of vascular systems within the porous area.
- For orthopedic uses, metals such as tantalum or titanium are often used because these metals exhibit high tensile strength and corrosion resistance, along with excellent biocompatibility.
- In addition, the porous structure allows for soft tissue adherence and vascularization within the implant.
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- During embryological development, new capillaries are formed by vasculogenesis, the process of blood vessel formation occurring by de novo production of endothelial cells and their formation into vascular tubes.
- A capillary bed can consist of two types of vessels: true capillaries, which branch mainly from arterioles and provide exchange between cells and the circulation, and vascular shunts, short vessels that directly connect arterioles and venules at opposite ends of the bed, allowing for bypass.
- When heart rate increases and more blood must flow through the lungs, capillaries are recruited and are distended to make room for increased blood flow while resistance decreases.
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- The vasoconstriction response is triggered by factors such as a direct injury to vascular smooth muscle, signaling molecules released by injured endothelial cells and activated platelets (such as thromboxane A2), and nervous system reflexes initiated by local pain receptors.
- Vascular spasm is much more effective at slowing the flow of blood in smaller blood vessels.
- During inflammation, vasodilation occur, along with increased vascular permeability and leukocyte chemotaxis, ending the spasm of vasoconstriction and hemostasis as wound healing begins.
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- For example, vascular disorders (such as strokes) occur over minutes or hours, whereas chronic disorders (such as Alzheimer's disease) occur over a matter of years .
- Grades 4 -, 4, and 4+ may be used to indicate movement against slight, moderate, and strong resistance respectively;
- Rigidity-Cogwheeling (abnormal tone suggestive of Parkinson's disease), Gegenhalten (resistance to passive change, where the strength of antagonist muscles increases with increasing examiner force.