Study Guide- Chapter 20- Vessels PDF

Study Guide- Chapter 20- Vessels and Circulation Describe the relationship of the total cross-sectional area and velocity of blood flow. The relationship between the total cross-sectional area and velocity of blood flow can be described by the principle of continuity, which states that "the volume f...

Study Guide- Chapter 20- Vessels and Circulation Describe the relationship of the total cross-sectional area and velocity of blood flow. The relationship between the total cross-sectional area and velocity of blood flow can be described by the principle of continuity, which states that "the volume flow rate of an incompressible fluid is constant throughout a closed system" Predict the significance of slow blood flow in the capillaries. Slow blood flow in capillaries has significant consequences on various aspects of human physiology. It impairs oxygen and nutrient delivery to tissues, impedes waste removal, disrupts thermoregulation, and increases the risk of blood clot formation. Explain the process of diffusion and vesicular transport between capillaries and tissues. Diffusion allows small molecules and ions to passively move across capillary walls based on their concentration gradients, while vesicular transport mechanisms such as endocytosis and exocytosis play a role in the movement of larger molecules or specific substances between capillaries and tissues. These processes are vital for maintaining homeostasis by ensuring efficient exchange of nutrients, gases, and waste products within the body. Explain the processes of bulk flow, filtration, and reabsorption. Bulk flow is the downward movement of huge quantities of fluids and their dissolved constituents along a pressure gradient. Compare and contrast hydrostatic pressure and colloid osmotic pressure in the capillaries. While hydrostatic pressure pushes fluid out of the capillaries into tissue spaces, colloid osmotic pressure pulls fluid back into the capillaries. These two opposing forces work together to maintain proper fluid distribution between intravascular and extravascular compartments. Define net filtration pressure (NFP). Net filtration pressure (NFP) is the distinction between the net hydrostatic pressure and the net colloid osmotic pressure. Calculate net filtration pressure for both the arterial end and the venous end of a capillary. At the arterial end of a capillary: 1. Hydrostatic Pressure (HPc): This is the force exerted by the blood against the walls of the capillary. It tends to push fluid out of the capillary into the interstitial space. The typical value for HPc is around 35 mmHg. 2. Colloid Osmotic Pressure (OPc): This is the osmotic pressure exerted by plasma proteins in the blood. OPc tends to draw fluid back into the capillary from the interstitial space. The typical value for OPc is around 25 mmHg. 3. Fluid Permeability (Kf): This represents how easily fluid can move across the capillary wall. Kf depends on characteristics such as endothelial cell fenestrations or gaps between cells. Its typical value varies but is generally low compared to other factors. The net filtration pressure (NFP) at the arterial end can be calculated using the following formula: NFP = HPc - OPc Taking typical values, NFP = 35 mmHg - 25 mmHg = 10 mmHg. At the venous end of a capillary: 1. Hydrostatic Pressure (HPc): Due to resistance encountered along its length, hydrostatic pressure decreases from arteriole to venule end of a capillary. At this point, it typically drops to around 15 mmHg. 2. Colloid Osmotic Pressure (OPc): This remains relatively constant throughout a capillary bed and maintains an average value of approximately 25 mmHg. Using similar calculations as above: NFP = HPc - OPc NFP = 15 mmHg - 25 mmHg = -10 mmHg Explain the lymphatic system’s role at the capillary bed. While net filtration happens at the capillary's arterial end and net reabsorption occurs at the capillary's venous end, not all fluid is reabsorbed at the capillary's venous end. Typically, only around 85 percent of the fluid that has flowed from the blood into the interstitial fluid is reabsorbed by the capillary. Collecting and returning this surplus fluid to the circulation is the job of the lymphatic system. This extra fluid is reabsorbed, filtered, and returned to the venous circulation through lymph vessels. Edema may occur as a consequence of abnormal capillary exchange or lymphatic system absorption of excess fluid. Edema is an accumulation of interstitial fluid that results in tissue swelling. Describe what is meant by degree of vascularization. The degree of vascularization refers to the extent and density of blood vessels within a tissue or organ. It is a measure of how well an area is supplied with blood vessels, which are responsible for delivering oxygen and nutrients to cells, as well as removing waste products. Explain the process of angiogenesis and how it aids perfusion. Angiogenesis is how new blood vessels are formed in tissues in need of them. This mechanism assists in maintaining appropriate perfusion across the course of many weeks to months of anatomic changes. In skeletal muscle, aerobic exercise stimulates angiogenesis. Angiogenesis occurs in adipose connective tissue when a person accumulates weight in the form of fat deposits. Angiogenesis may also develop due to the progressive obstruction of coronary arteries, possibly enabling new pathways for blood to reach the heart wall. Describe the myogenic response that maintains normal blood flow through a tissue. The force that propels blood through blood arteries, known as systemic blood pressure, varies depending on the situation. However, because of the myogenic response, which involves the contraction and relaxation of smooth muscle inside blood vessels in response to variations in blood vessel wall stretch, blood flow into tissue may stay relatively constant. Increased systemic blood pressure results in a high blood volume entering the blood artery, stretching the smooth muscle cells lining the channel. This induces the contraction of smooth muscle cells, resulting in vasoconstriction. Therefore, even when systemic blood pressure is increased, which would result in increased blood flow into the blood vessel, the ensuing vasoconstriction reduces the size of the blood vessel lumen, cancelling out the increase in blood flow into the tissue. Reduced systemic blood pressure, on the other hand, causes a reduced amount of blood to enter the blood vessel, resulting in less stretching of the smooth muscle cells inside the blood vessel wall. This causes smooth muscle cells to relax, which causes vasodilation. Compare and contrast a vasodilator and a vasoconstrictor. Vasodilation is the process by which blood vessels, particularly arterioles and precapillary sphincters, relax and expand in response to certain signals or stimuli. This relaxation allows for an increase in the diameter of the blood vessels, resulting in a greater flow of blood through them. Vasoconstriction refers to the contraction or narrowing of blood vessels. This occurs when smooth muscles surrounding the blood vessels contract, leading to a reduction in their diameter. As a result, the flow of blood through these vessels is restricted. Explain how a tissue autoregulates local blood flow based on metabolic needs. Tissues autoregulate local blood flow based on metabolic needs through a process known as metabolic vasodilation. When the metabolic activity of a tissue increases, such as during exercise or in response to injury, metabolites like adenosine and carbon dioxide accumulate in the tissue. These metabolites act as vasodilators, causing the local arterioles to dilate and increase blood flow to meet the increased metabolic demands of the tissue. This mechanism ensures that tissues receive adequate oxygen and nutrients for their ongoing physiological functions. Describe how local blood flow is altered by tissue damage and as part of the body’s defense. - Tissue damage triggers a local inflammatory response. - Injured cells release chemical signals, such as histamine and prostaglandins, which cause blood vessels to dilate. - Dilation of blood vessels increases blood flow to the damaged area. - Increased blood flow brings oxygen, nutrients, and immune cells to the site of injury for tissue repair and protection against infection. - Blood clotting factors are also transported to the damaged tissues via increased blood flow, helping to stop bleeding and promote healing. - The increased blood flow can result in redness, warmth, and swelling at the site of injury. - This localized increase in blood flow is part of the body's defense mechanism to facilitate healing and protect against further damage. Explain the general relationship of total blood flow to local blood flow. Total blood flow - amount of blood transported throughout the entire vasculature in a given period of time and equal cardiac output. As one increases the other does too. Local blood flow is dependent upon total blood flow. Define blood pressure and blood pressure gradient. Blood pressure - the force blood exerts against the inside wall of a vessel Blood pressure gradient - the change in blood pressure from one end of a blood vessel to the other end driving force that moves blood through the vasculature Compare and contrast blood pressure and blood pressure gradients in the arteries,capillaries, and veins. 1. Arterial blood pressure: Blood flow in arteries pulses with cardiac cycle. Have: Systolic pressure (occurs when ventricle contracts); Diastolic (pressure occurs when ventricles relax); Pulse pressure (pressure in arteries added by heart contraction); 2. Capillary blood pressure: Pressure no longer fluctuates between systolic and diastolic. Needs to be high enough for exchange of substances. Needs to be low enough not to damage vessels; 3. Venous return of blood to the heart depends on pressure gradient, skeletal muscle pump, and respiratory pump. Venous pressure is low and not pulsatile Calculate pulse pressure and mean arterial pressure (MAP) in the arteries. https://www.youtube.com/watch?v=XiVpku0vjLU Pulse pressure is the extra pressure imposed on the arteries between the heart's resting state (diastolic blood pressure) and its contracting state (systolic blood pressure). The pulse pressure is obtained by subtracting the systolic and diastolic blood pressures. For example, if the diastolic blood pressure is 130 mm Hg and systolic is 80 mm Hg, then the pulse pressure is 130 – 80 = 50 mmHg. The average measure of blood pressure in the arteries is known as mean arterial pressure (MAP). The equation of the MAP is MAP = diastolic pressure + ⅓ systolic pressure. The mean arterial pressure is therapeutically relevant because it offers a numerical number for the perfusion of bodily tissues and organs. A MAP of 70 to 110 mm Hg is considered adequate perfusion. A MAP less than 60 mm Hg may suggest inadequate blood flow. A very high MAP may indicate larger than usual blood flow to bodily tissues, resulting in tissue edema (swelling). The arteries nearest to the heart, such as the aorta, have the greatest pulse and mean arterial pressure. These pressures diminish when the arteries branch into smaller vessels and remove themselves from the ventricles. The pressure gradient in arteries is rather steep, which aids in blood circulation through them. Explain the mechanisms that help overcome the small pressure gradient in veins to return blood to the heart. The blood pressure gradient is what propels blood through the vasculature. Variations in the blood pressure gradient are inversely proportional to variations in total blood flow. A greater blood pressure gradient increases total blood flow, while a smaller blood pressure gradient results in a reduction in total blood flow. Changes in cardiac output influence the blood pressure gradient. A greater cardiac output results in a greater pressure gradient. In the other direction, a reduction of cardiac production reduces the pressure gradient. Define resistance, and explain how it is influenced by blood viscosity, vessel length, and vessel radius. The term resistance refers to the degree of friction that blood encounters as it travels through the blood arteries. Resistance to blood flow is always present. This friction occurs due to the blood's interaction with the blood vessel wall. Typically, the phrase peripheral resistance refers to the resistance of blood in blood arteries. The term viscosity refers to a fluid's resistance to flow. It refers to the "thickness" of a liquid in a broader sense. The more viscous a fluid is, the higher its resistance to flow. The thickness is proportional to the relative proportion of particles in the liquid and their interactions. A change in the viscosity of blood results in an alteration in the resistance of blood flow through vessels. Increased vessel length increases resistance since longer vessels create more friction for the fluid as it travels through the vessel. In comparison, shorter vessels with equivalent diameters give less resistance. Blood viscosity and artery length stay largely stable in an average healthy person. The primary mechanism by which resistance may be adjusted is by modifying the radius of the vessel lumen. When vessel width grows, blood flow towards the margins decreases but total blood flow rises. When the radius of an artery shrinks, however, more blood flows at the margins and total blood flow drops. Explain the relationship of both blood pressure gradients and resistance to total blood flow. -as blood pressure gradient increases, total blood flow is greater and as blood pressure gradient decreases total blood flow lessens -if resistance increases blood flow lessens and if resistance decreases blood flow increases Discuss why blood pressure increases with increased resistance in the systemic circulation. People with chronically raised resistance caused by considerable weight gain or atherosclerosis have elevated arterial blood pressure measurements. This clinically relevant condition arises when a larger pressure gradient is required to overcome the increased resistance and maintain normal blood flow and appropriate perfusion of all tissues. Describe the anatomic components associated with regulating blood pressure through short-term mechanisms. Short-term regulation of blood pressure involves complex interactions between baroreceptors, the autonomic nervous system, and the cardiovascular system. These components work together to detect changes in blood pressure and initiate appropriate responses to maintain homeostasis. Explain the autonomic reflexes that alter blood pressure. -Chemoreceptor reflexes also influence blood pressure -Stimulation of chemoreceptors brings about negative feedback reflexes to return blood chemistry to normal -Main peripheral chemoreceptors are in aortic and carotid bodies -High carbon dioxide, low pH, very low oxygen stimulate chemoreceptors -Chemoreceptor firing stimulates vasomotor center Describe the hormones that regulate blood pressure. -Hormones also regulate blood pressure -Epinephrine and norepinephrine work with sympathetic nervous system -Angiotensin II, antidiuretic hormone, aldosterone, and atrial natriuretic peptide also have effects Explain the renin-angiotensin system and its influence on blood. Because the neurological system initiates angiotensin II synthesis (short-term processes), and angiotensin II induces the release of other hormones, the renin-angiotensin system straddles short-term neuronal control and long-term hormonal regulation. Angiotensinogen is a plasma protein created by the liver and released into the bloodstream regularly. In reaction to low blood pressure or sympathetic division activation, the kidney releases the enzyme renin into the bloodstream. Renin converts angiotensinogen to angiotensin I in circulation. Angiotensin-converting enzyme (ACE), an enzyme found in the capillary endothelium, converts angiotensin I to angiotensin II. The actions of angiotensin II on its target organs in order to impact the major factors that govern blood pressure include the following: Angiotensin II is a strong vasoconstrictor of blood arteries, which results in a larger rise in peripheral resistance and blood pressure Contrast the effects of aldosterone, antidiuretic hormone, and angiotensin II on blood pressure with those of atrial natriuretic peptide. - Aldosterone promotes sodium reabsorption and water retention, raising blood volume and increasing blood pressure. - ADH promotes water reabsorption, reducing urine output and increasing blood volume. - Angiotensin II causes vasoconstriction, increasing peripheral resistance and raising blood pressure. - ANP promotes vasodilation, increases urinary sodium excretion, and reduces water reabsorption, resulting in decreased blood volume and lowered blood pressure. Aldosterone, ADH, and angiotensin II are all involved in mechanisms that increase blood pressure, while ANP works to decrease it. Compare total blood flow and distribution at rest and during exercise. Total blood flow: - At rest, total blood flow is lower compared to during exercise. During rest, cardiac output and total blood flow are typically around 5 liters per minute - During exercise, total blood flow increases significantly. During moderate-intensity exercise, cardiac output can increase up to 25 liters per minute or more Distribution of blood flow: - At rest, a larger proportion of the blood is directed towards essential organs such as the brain, heart, and kidneys. At rest, approximately 20% of the cardiac output goes to the brain, while about 15-20% goes to the heart and approximately 20% goes to the kidneys- During exercise, there is a redistribution of blood flow to meet the increased oxygen demands of working muscles. Blood flow to skeletal muscles can rise from around 15-20% at rest to over 80% during intense exercise Trace the pathway of blood circulation in the fetus. Oxygen and nutrients from the mother's blood are transferred across the placenta to the fetus through the umbilical cord. This enriched blood flows through the umbilical vein toward the baby's liver. There it moves through a shunt called the ductus venosus. Describe the changes that occur after the baby is born and must utilize the pulmonary circulation. The fetal circulation starts to transition to the postnatal pattern during delivery. When a newborn breathes for the first time, pulmonary resistance decreases, and the pulmonary arteries expand. Consequently, the pressure on the right side of the heart reduces, increasing the pressure on the left side, which is responsible for systemic circulation. Postnatal alterations include the following: Umbilical veins and arteries contract and become inoperable. They develop into the liver's round ligament and the medial umbilical ligaments The ductus venosus becomes inoperable and constricts, transforming into the ligamentum venosum Due to the increased strain on the left side of the heart, the interatrial septum's two flaps block off the foramen ovale. The foramen ovale's only surviving relic is a narrow, oval indentation in the septum's wall called the fossa ovalis. After 10 to 15 hours of birth, the ductus arteriosus constricts and transforms into the ligamentum arteriosum, a fibrous tissue.