Please complete table and explain questions 1) Does regulating blood flow throug
ID: 225921 • Letter: P
Question
Please complete table and explain questions
1) Does regulating blood flow through capillaries directly alter:
A) length of the blood vessels? Explain.
B) diameter or radius of the vessel(s)? Explain.
C) viscosity of the blood? Explain.
D) resistance within the vessel? Explain.
E) the flow of blood? Explain.
Increase
Decrease
No change
Length
Diameter
Viscosity
Resistance
Blood flow
Increase
Decrease
No change
Length
Diameter
Viscosity
Resistance
Blood flow
Explanation / Answer
(A)
The walls of all blood vessels except the smallest consist of three layers: the tunica intima, tunica media, and tunica externa.
The tunica intima reduces friction between the vessel walls and blood; the tunica media controls vasoconstriction and vasodilation of the vessel; and the tunica externa protects, reinforces, and anchors the vessel to surrounding structures.
Elastic, or conducting, arteries contain large amounts of elastin, which enables these vessels to withstand and smooth out pressure fluctuations due to heart action.
Muscular, or distributing, arteries deliver blood to specific body organs, and have the greatest proportion of tunica media of all vessels, making them more active in vasoconstriction.
Arterioles are the smallest arteries and regulate blood flow into capillary beds through vasoconstriction and vasodilation.
Capillaries are the smallest vessels and allow for exchange of substances between the blood and interstitial fluid.
Continuous capillaries are most common and allow passage of fluids and small solutes.
Fenestrated capillaries are more permeable to fluids and solutes than continuous capillaries.
Sinusoidal capillaries are leaky capillaries that allow large molecules to pass between the blood and surrounding tissues.
Capillary beds are microcirculatory networks consisting of a vascular shunt and true capillaries, which function as the exchange vessels.
A cuff of smooth muscle, called a precapillary sphincter, surrounds each capillary at the metarteriole and acts as a valve to regulate blood flow into the capillary.
(B)
Blood flow refers to the movement of blood through a vessel, tissue, or organ, and is usually expressed in terms of volume of blood per unit of time. It is initiated by the contraction of the ventricles of the heart. Ventricular contraction ejects blood into the major arteries, resulting in flow from regions of higher pressure to regions of lower pressure, as blood encounters smaller arteries and arterioles, then capillaries, then the venules and veins of the venous system. This section discusses a number of critical variables that contribute to blood flow throughout the body. It also discusses the factors that impede or slow blood flow, a phenomenon known as resistance.
As noted earlier, hydrostatic pressure is the force exerted by a fluid due to gravitational pull, usually against the wall of the container in which it is located. One form of hydrostatic pressure is blood pressure, the force exerted by blood upon the walls of the blood vessels or the chambers of the heart. Blood pressure may be measured in capillaries and veins, as well as the vessels of the pulmonary circulation; however, the term blood pressure without any specific descriptors typically refers to systemic arterial blood pressure—that is, the pressure of blood flowing in the arteries of the systemic circulation. In clinical practice, this pressure is measured in mm Hg and is usually obtained using the brachial artery of the arm.
(C)
Viscosity is an intrinsic property of fluid related to the internal friction of adjacent fluid layers sliding past one another (laminar flow). This internal friction contributes to the resistance to flow. The interactions between fluid layers depend on the chemical nature of the fluid, and whether it is homogeneous or heterogeneous in composition. For example, water is a homogeneous fluid and its viscosity is determined by molecular interactions between water molecules. Water behaves as a Newtonian fluid and therefore under non-turbulent conditions, its viscosity is independent of flow velocity (i.e., does not change with changes in velocity). Although plasma is mostly water, it also contains other molecules such as electrolytes, proteins (especially albumin and fibrinogen), and other macromolecules. Because of various molecular interactions between these many different components of plasma, it is not surprising that plasma has a higher viscosity than water. In fact, plasma at 37°C is about 1.8-times more viscous than water at the same temperature.
(D)
Blood vessels - and in particular, the more muscular arteries - are often the source of resistance. One way an artery can actively resist blood flow is by contracting the smooth muscle in its wall, causing the artery to constrict. When an artery constricts, we call it vasoconstriction. This is an easy term to recall if you remember that 'vaso' refers to 'blood vessel.' During vasoconstriction, the artery gets smaller and offers increased resistance. This causes a decreased blood flow through its lumen, or hollow center. If, on the other hand, the smooth muscle in the wall of the artery relaxes, the blood vessel moves into a state of vasodilation, and its lumen dilates, or gets bigger. This offers decreased resistance and causes an increased blood flow. This is much like a nozzle at the end of a hose. If the nozzle is almost closed, it will allow less water to get through. If the nozzle is opened wide, it will allow more water to flow through.
(E)
Blood flow is the continuous movement of blood through the circulatory system. As blood moves through your body, it encounters resistance to its flow. There are a number of factors that influence blood flow. These factors include the thickness, or viscosity, of your blood and the length of a blood vessel. In other words, if the blood is thicker - more like molasses than it would be like water - there's more resistance to flow. Also, if a blood vessel is longer, it will be harder for blood to pass through that vessel, and there will be more resistance to blood flow. Another factor is the difference in pressure at the beginning and end of the vessel. This pressure difference is important, because later, we will see that blood flows from high to low pressure. However, one of the most important factors influencing blood flow is the size or radius of the blood vessel the blood is passing through.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.