Circulatory System and Blood, and Acid-Base Physiology Flashcards
(42 cards)
What are the components of whole blood?
plasma and formed elements (blood cells/cell fragments). hematocrit is the ratio of rbc to total blood volume. in women it is around 37-48% and in men 45-52%. hematopoietic stem cells are 2 early branch points which form lymphoid progenitor cells for lymphocytes and natural killer cells, and myeloid progenitor cells for any other blood cell in the body.
What are the major functions of the circulatory system?
it distributes dissolved gases and other molecules for nutrition, growth and repair to to tissues and removes metabolic wste products from tissues. it circulates hormones or neurotransmitters for fast chemical signalling. it dissipates heat by delivery of heat from the core to the surface of the body. it mediates the inflammatory and host defence responses against invading microorganisms. it supports detoxification and elimination roles of the liver and kidneys.
What is the function of arteries, arterioles and capillaries in blood vessels.
arteries deliver oxygenated blood to tissues. they are made of extensive elastic tissue and smooth muscle, and under high pressure they have thick walls.
arterioles are the smallest branch of arteries
capillaries are the site of gas, nutrients and water exchange. it has the largest total cross sectional and surface area.
What is the function of venules, arteriovenous anastomosis and veins in blood vessels.
venules are formed by merged capillaries.
arteriovenous anastomosis is a transitional muscuolar central vessel in a capillary bed where blood is shunted and allowed to bypass capillaries (fingers and toes)
veins are the site of return of blood to heart (from systemic circulation or lungs). they progressively combine to form larger veins. contain valves, have thin walls and under low pressure compared to arteries.
What is the anatomy of an artery?
contained tunica which is a layered structure, categorised into externa, media and intima. they vary in diameter and proportion of smooth musculature and elastic tissue.
elastic arteries accomodate pressure changes from the cardiac cycle. muscular arteries regulate bp.
arterioles regulate local tissue perfusion and capillaries provide gas/nutrient exchange.
What is the anatomy of a vein?
they contain tunica. they have thinner walls so the lumen of the vein is larger than the lumen of an artery of a comparable size. they contain valves to prevent blood backflow due to gravity, always directing blood back to the heart.
What is the arterial system?
the vasodilation/constriction of arterioles significantly affects bp. slight vasodilation will significantly dec resistance in the vessel and increase blood flow. slight vasocontriction will significantly increase resistance in the vessel and decrease blood flow.
What is the venous system?
vasoconstriction inc bp helping with venous return to the heart. it also causes the lumen to become rounder, decreasing resistance and increasing flow. it is a low pressure resevoir, and as blood moves from venule to veins, bp drops but blood velocity increases.
What is venous return?
venous return occurs through muscle contractions, respiratory pump, and vasoconstriction.
in muscle contractions, pressure inc passively in veins forcing blood through the valves.
in the respiratory pump, as air pressure within the thorax drops, bp in thoracic vein also dec below pressure of abdominal veins, causing the blood to flow from outside thorax to inside thorax following the pressure gradient.
in vasoconstriction, the constriction of veins increases bp and flow and opens valves eg during exercise.
What is flow characterisation?
blood flow is usually laminar, forward in a parabolic pathway. if flow becomes impeded or when there is a regularity, blood flow can become turbulent. this can be caused by a blood clot or occur near a valve, which can cause increased resistance and damage the wall of the blood vessel leading to an increased risk of disease. reynold’s number predicts the likelihood of flow being turbulent.
How is bp measured?
bp is measured through a sphygmomanometer. turbular flow is accomponied by murmurs or bruits (in vasculature). a bruit reflects the commencement of turbulent blood flow when the pressure of the cuff dec below the arterial pressure. when obtaining manual bp, this is heard through a stethescope.
What is blood perfusion?
it is the rate of blood flow into a tissue. perfusion rates at rest reflect metabolic activity, which differs dramatically during exercise.
How is tissue perfusion regulated?
it is regulated by both local factors and autonomic sympathetic tone.
What are the 3 main types of capillaries?
continuous capillary is the most common form, made of endothelial junctions 10-15nm wide and are found in skeletal muscle.
fenestrated capillary have thin endothelial cells and have many fenestrations, they surround epithelia and can be found in the small intestines and exocrine glands.
discontinuous (sinusoidal) capillary have large fenestrations and gaps and are found in sinusoids such as liver and marrow.
What is capillary exchange?
capillary exchange provides surrounding tissues with oxygen, glucose, amino acids, and fluid exchange between blood and surrounding extracellular fluid. they are responsible for diffusion, trancytosis and bulk flow.
What is the sterling hypothesis?
it states the flow of fluid across the capillary wall depends on the force of bp (hydrostatic pressure) on the walls, which tends to force fluids out, and osmotic pressure within the capillary, which tends to bring fluids in and has a greater conc of dissolved substances in blood. net filtration pressure is the combination of pressures inside the capillary. starling forces determind the volume and directionality of fluid movement (Jv).
What is filtration and absorbtion?
filtration occurs from blood to ECF to cells, with O2, glucose, amino acids, and hormones.
absorption occurs from cells to ECF to blood, with CO2, waste and water.
What are fluid dynamics?
approx 20L fluid filtered through the capillaries per day. 85% of fluid that is filtered along arteriole end is reabsorbed on venous end. fluid that doesn’t return are plasma proteins that leave capillary into the interstitial space. the remainder of fluid and proteins enter the lymphatic capillaries (3L/day) and is eventually returned to blood.
How is blood flow regulated in the capillaries?
regulated by local factors through autoregulation. capillaries open and closed based on the requirements of a given tissue, with oxygen requirement being the most important. the terminal part of the arteriole (metarteriole) contains precapillary sphincters to control blood flow into the capillaries. local factors influence whether the sphincters are open or closed (vasomotion).
How is blood flow regulated in skeletal muscle?
relies on autoregulation. this leads to hyperemia which increases blood flow into the vessels. active hyperemia is local vasodilation to deliver blood (and oxygen) to muscles more efficiently. reactive hyperemia is blood flow response to occlusion (eg increased flow following occulsion of the bronchial artery when measuring bp)
How is blood flow regulated in the kidneys?
through autoregulation such as arteriole myogenic mechanism, or tubuloglomerular feedback.
through sympathetic tone, where the reduction of sympathetic stimulation results in vasodilation and increased flow at rest, and increase of sympathetic stimulation constricts arteriolar smooth muscle resulting in diminished glomerular filtration rate (GFR) and less demand for oxygen.
Describe blood flow to the liver and how it is regulated.
blood flows to the liver through the hepatic system. it is regulated by hepatic arterial flow, portal venous inflow and the relationship between hepatic arterial and portal inflow circuits. the portal triad is the hepatic arteriole which delivers oxygenated blood to the liver, the portal venule which carries blood from the pancreas, stomach, spleen, small intestine and colon to the liver, and the bile duct which collects bile products secreted by hepatocytes. blood mixes with the microvessels (sinusoids) and drains into the central vein which leads to the vena cava and back to the right atrium of the heart.
What is the lymphatic system?
it helps with fluid balance throughout the day, and drains interstitial fluid back into the venous system. it initiates an immune response by producing and transporting lymphocytes, and transports dietary lipids absorbed by GI into the blood.
it consists of the lymph which is a colourless fluid that floats in lymphatic vessels, and lymphatic tissues which have special capillaries that permit movement of lymphocytes from the blood into the lymphatic system throughout the body.
How is fluid moved in the lymphatic system?
20L of fluid leave capillaries everyday, only 17L returned. the lymph helps return the other 3L to circulation from capillaries into the llymph system , passing through lymph nodes and lymphatic vessels and drains back into the venous system. the rate of lymph flow depends on interstitual fluid pressure and the activity of lymphatic pump (valves) being stretched and opening, continuously moving lymph through the system.
