lecture 12 Flashcards
Describe the forces that create capillary filtration and reabsorption.
o Capillary filtration and reabsorption are primarily driven by two opposing forces: hydrostatic pressure which pushes fluid out of the capillary (filtration), and colloid osmotic pressure (oncotic pressure) which draws fluid back into the capillary (reabsorption); the balance between these forces determines the net movement of fluid across the capillary wall, with filtration dominating at the arterial end and reabsorption at the venous end of the capillary
o Hydrostatic pressure - This is the pressure exerted by the fluid within the capillary, pushing against the capillary walls and tending to force fluid out into the interstitial space. At the arterial end of the capillary, where blood pressure is highest, hydrostatic pressure is greater, promoting filtration.
o Colloid osmotic pressure - This pressure is created by the presence of large plasma proteins within the capillary, which draw water back into the capillary due to their high solute concentration. Since these proteins are largely unable to leave the capillary, their osmotic pull is constant, promoting reabsorption
essentially what are the capillary beds doing during filtration and reabsorption
Essentially in your capillary bed there is a game of tug-of-war between the arteries and venules where eventually the osmosis is higher. Osmosis is most responsible for fluid returning to the venule side of the capillary bed. This means that more fluid enters than returns to the blood. There is more pressure being exerted out of the blood and the lymphatic system helps to regulate all of this.
Explain how changes in net filtration pressure (NFP) can result in edema and how a functional lymphatic system normally prevents edema.
o Edema occurs when there is an increase in net filtration pressure (NFP), causing excessive fluid to leak out of capillaries into the interstitial spaces, leading to tissue swelling; a healthy lymphatic system prevents edema by actively draining this excess fluid back into the bloodstream, maintaining fluid balance within tissues
This means that if not enough fluid is taken out by the capillaries, an edema can occur which the lymphatic system gets rid of the wastes that cause this fluid buildup thus helping prevent edema.
blood pressure
the force per unit area exerted on a vessel wall (measured in mmHg)
blood flow
the continuous movement of blood through the circulatory system, from the heart to the body’s tissues and back again
peripheral resistance
the resistance of the arteries to blood flow
Pressure = Hr x SV x (V x L/R4)
State and interpret the equation that relates fluid flow to pressure and resistance.
o The equation that relates fluid flow (Q) to pressure difference (ΔP) and resistance (R) is: Q = ΔP / R; this means that the flow rate of a fluid is directly proportional to the pressure difference across a system and inversely proportional to the resistance to flow within that system.
Resistance = V x L/R4
If viscosity increases as does resistance, if length increases as does resistance, if radius increases resistance decreases.
Describe the role of arterioles in regulating tissue blood flow and systemic arterial blood pressure.
o Arterioles play a crucial role in regulating tissue blood flow and systemic arterial blood pressure by acting as the primary “resistance vessels” in the circulatory system, meaning they can significantly control blood flow to different tissues through their ability to constrict or dilate, thereby adjusting the resistance to blood flow based on local needs and systemic demands; this dynamic regulation directly impacts blood pressure throughout the body
Interpret relevant graphs to explain the relationships between vessel diameter, cross-sectional area, blood pressure, and blood velocity.
o cross sectional area measures vessel diameter whereas blood flow velocity measures the rate of blood transported per unit time and is measured in cm per second. These two have an inverse relationship. The capillaries have the shortest blood flow velocity and greatest cross sectional velocity
Using a graph of pressures within the systemic circuit, interpret the pressure changes that occur in the arteries, capillaries, and veins.
o A graph of pressures within the systemic circuit would show a significant drop in pressure as blood moves from the arteries to capillaries, with a further gradual decrease in pressure within the veins, indicating that the highest pressure is in the arteries, followed by a much lower pressure in capillaries, and the lowest pressure in the veins; this pressure gradient is crucial for blood to flow through the circulatory system.
Given values for systolic and diastolic blood pressure, calculate pulse pressure (PP)and mean arterial pressure (MAP).
o Pulse pressure = systolic pressure – diastolic pressure
o Mean arterial pressure = diastolic + (pulse pressure/3)
State the equation relating mean arterial pressure (MAP) to cardiac output (CO) and total peripheral resistance (TPR).
o MAP = CO x TPR
MAP = cardiac output X total peripheral resistance
Predict and describe how mean arterial pressure (MAP) would be affected by changes in total peripheral resistance (TPR) or by changes in cardiac output (CO) or any of its components - heart rate (HR), stroke volume (SV) or preload.
o increasing either cardiac output (CO) or total peripheral resistance (TPR) will directly result in an increase in mean arterial pressure (MAP), while decreasing either factor will lead to a decrease in MAP; changes in individual components of cardiac output like heart rate (HR) or stroke volume (SV) will also affect MAP proportionally as they contribute to the overall CO value
Explain the role of the autonomic nervous system in regulation of blood pressure and volume.
o The autonomic nervous system (ANS) plays a crucial role in regulating blood pressure and volume by controlling heart rate, blood vessel constriction (vasoconstriction), and the release of hormones that influence fluid balance, primarily through its sympathetic and parasympathetic divisions, responding to changes in blood pressure detected by specialized receptors called baroreceptors.
Explain how local control mechanisms and myogenic autoregulation influences blood flow to tissues.
o Local control mechanisms, particularly the myogenic autoregulation process, significantly influence blood flow to tissues by allowing individual organs to adjust their vascular resistance based on their immediate needs, maintaining a relatively constant blood flow even when systemic blood pressure fluctuates; essentially, the blood vessels within a tissue constrict or dilate in response to changes in pressure to ensure adequate tissue perfusion regardless of the overall circulatory pressure
Provide specific examples to demonstrate how the cardiovascular system maintains blood pressure homeostasis in the body.
o The cardiovascular system maintains blood pressure homeostasis through mechanisms like adjusting heart rate, altering blood vessel diameter (vasoconstriction and vasodilation) in response to signals from the nervous system, and regulating blood volume via the renin-angiotensin-aldosterone system (RAAS), effectively adapting to situations like exercise, changes in posture, or blood loss, to ensure consistent blood pressure throughout the body
Define a portal system. [introduced with Hypophyseal portal system in - Review from Endocrine]
o A portal system is a specialized network of blood vessels where blood flows from one capillary bed directly to another, allowing for the efficient transport of substances between two organs without first entering the systemic circulation; the most well-known example is the hypophyseal portal system, which connects the hypothalamus to the anterior pituitary gland, enabling the rapid delivery of regulatory hormones from the hypothalamus to the pituitary gland
Describe the structure and functional significance of the hepatic portal system.
o The hepatic portal system is a unique circulatory network of veins that carries blood from the digestive organs (stomach, intestines, pancreas, and spleen) to the liver, allowing the liver to process absorbed nutrients, toxins, and other substances before they enter the systemic circulation; this system consists of the hepatic portal vein, which is formed by several tributary veins from the digestive tract, and branches into smaller vessels within the liver called sinusoids, where the blood is processed by hepatocytes before draining into hepatic veins and eventually into the inferior vena cava
Describe the role of the placenta, umbilical vessels, ductus venosus, foramen ovale, and ductus arteriosus in fetal circulation [covered foramen ovale and ductus arteriosus in heart]
o In fetal circulation, the placenta acts as the primary site for gas and nutrient exchange with the mother, while the umbilical vessels carry oxygenated blood from the placenta to the fetus and deoxygenated blood back to the placenta; the ductus venosus allows oxygenated blood to bypass the liver, the foramen ovale shunts blood from the right atrium to the left atrium bypassing the lungs, and the ductus arteriosus further diverts blood away from the lungs by connecting the pulmonary artery to the aorta; all these structures work together to ensure the fetus receives adequate oxygen and nutrients while in the womb
Connect the cardiovascular system to other body systems
Respiratory system: The cardiovascular system carries deoxygenated blood to the lungs where it picks up oxygen, then returns oxygenated blood to the body through the circulatory loop.
Digestive system: Blood from the small intestine absorbs nutrients which are then transported throughout the body by the cardiovascular system.
Endocrine system: Hormones secreted by endocrine glands are transported via the bloodstream to target organs throughout the body.
Muscular system: The cardiovascular system supplies oxygen and nutrients to muscles to support their contraction and movement.
Nervous system: The nervous system regulates heart rate and blood pressure through signals sent to the heart and blood vessels.
