Class 9 Delivery and Exchange PDF

Pumps and Tubes: delivery and exchange Class 9 How do the processes of small scale flow connect to large scale flow in order to guarantee both delivery and exchange? What is the effect of gravity on the cardiovascular system?...

Pumps and Tubes: delivery and exchange Class 9 How do the processes of small scale flow connect to large scale flow in order to guarantee both delivery and exchange? What is the effect of gravity on the cardiovascular system? How did living systems evolve and adapt to terrestrial gravity? https://www.youtube.com/watch?v=ue7ImjBIJ04  Pumps and Tubes: delivery and exchange How do the processes of small scale flow connect to large scale flow in order to guarantee both delivery and exchange? https://www.youtube.com/watch?v=ue7ImjBIJ04  Extravascular Intravascular The extravascular compartment comprises many subcompartments, such as the cellular, interstitial, and lymphatic subcompartments, and a specialized system containing cerebrospinal uid in the central nervous system. fl Capillary exchange mechanisms  Myogenic mechanism Change in the blood ow by altering arteriolar resistance. Velocity of blood ow is inversely related to resistance. Myogenic mechanism slows blood ows by increasing resistance when arteriolar pressure rises. Blood changes maintain local tissue perfusion at a constant level and ensures that gases and other substances continue to be exchanged adequate amount even in uctuating pressures fl fl fl fl  Bulk flow erence between due to manipulations of positive and negative pressure. Direction of essure and blood flow c pressure uids out of Blood pressure es at the arteriole into capillaries Pressure Inward flow enule end. Outward flow Osmotic pressure Arterial end of capillary Venous end Colloidal blood pressure remain constant because generated by proteins present in circulation. Hydrostatic blood pressure decreases along the capillary as the blood ow moves away from the heart. fl curs. Another way of expressing this is to say that at the venous end of the cap The difference between blood pressure and colloidal osmotic pressure drives fluids out of capillaries When the blood pressure When the blood pressure falls Figure exceeds1. the Capillary Exchange. colloidal pressure Net filtration occurs near thebelow arterial theend of thepressure colloidal capillary since capillary uid is hydrostatic forced out pressure (CHP) is greater than blood of capillary. colloidal uid moves intoosmotic the capillary. pressure (BCOP). There is no net movement of fluid near the midpoint since CHP = BCOP. Net reabsorption occurs near the venous end since BCOP is greater than CHP. fl fl Filtration is the movement of fluid out of the capillary and Reabsorption is the movement of fluid back into the capillary. www.cvphysiology.com  Lymphatic vessels drain into the subclavian veins in the neck. Filtration of lymph: removal of water and electrolytes, while retaining proteins and lipids in the lymph. Destruction and elimination of bacteria and toxins, carried out by the macrophages in lymph nodes.  Edema refers to the swelling of a tissue that results from excessive accumulation of uid within the tissue. Edema occurs when net capillary filtration exceeds the capacity of the lymphatics to carry away the fluid (net filtration > lymph flow) www.cvphysiology.com fl  Venous system The venous system collects blood from the capillaries and delivers it to the heart via the veins, which are low-pressure, exible structures. Large changes in blood volume have little e ect on the venous pressure. Thus, the venous system contains most of the blood and acts like a large volume reservoir. The percentage indicate the relative proportion of blood in di erent part of the circulation. fl ff ff  The volume-pressure relationships for an artery and vein Vessel compliance is the ability of a vessel to respond to an increase in pressure by distending and increase the volume of blood it can hold, and vice versa with decreased pressure. Vessel compliance (C), is the change in volume (ΔV) divided by the change in pressure (ΔP).  When the left ventricle ejects blood into the aorta, the aortic pressure rises. The maximal aortic pressure following ejection is termed the systolic pressure (Psystolic). As the left ventricle is relaxing and re lling, the pressure in the aorta falls. The lowest pressure in the aorta, which occurs just before the ventricle ejects blood into the aorta, is termed the diastolic pressure (Pdiastolic). fi  Blood pressure decreases as it reaches the capillary. The venous circuit is under low pressure and there isn’t much of a driving force to propel blood to the heart. How does the venous blood return to the heart? Valves in the veins prevent blood from moving backward.  Skeletal muscle contraction helps to carry venous blood back to the hearth The reason we feel discomfort while standing for long periods or sitting during a long plane ight is because our leg muscles are immobile and that causes the blood to accumulate in our lower veins. fl  Pumps and Tubes: delivery and exchange What is the effect of gravity on the cardiovascular system? https://www.youtube.com/watch?v=ue7ImjBIJ04  Staticfrom The pressure Fluid Pressure the weight of a column of liquid of area A and height h is of gravity. Fluid Pressure Measurement Index pressure static fluidexerted by a the arises from static fluidofdepends weight the fluid only and isupon giventheby the of the fluid, the density of the fluid, and the acceleration fluid of gravity. 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The fluid pressure at a given depth does not depend upon the total mass or total volume of the liquid. Pressure The above pressure expression is easy to see for the straight, unobstructedPressure concepts column, but not obvious for the cases of different geometry which are shown. concepts The fact that the liquid levels are Because of the ease of visualizing a column height of atheknown liquid, it has become same in these three common practice to state all kinds of pressures in column height units, manometers shows like mmHg or cm that the H2O, etc. Pressures are often measured by manometerspressure in terms of aglass in the liquid column height. manifold remarkable thing about this expression is what it does not include. The fluid above them is uniform. 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Arterial and Arterial and venous venous pressure pressure inin aa man man asas he he assumes assumes different different postures. postures. When person is lying down, the heart is at the same position as the feet and head, When person is lying down, the heart is at the same position as the feet and head, and pressures and pressures are are similar similar in in arteries arteries in in the the head, head, chest chest and and limbs. limbs. When GoWhen the person is standing up the relationship between head chest and limb Back the person is standing up the relationship between head chest and limb change with respect to gravity. changes with respect to gravity. Knut Schmidt-Nielsen, 1997 Knut Schmidt-Nielsen, 1997  Orthostatic or postural hypotension Arterial pressure fall when a person suddenly stands upright - cardiac output (CO) and mean arterial pressure (MAP) fall. Gravity acts on the vascular volume, causing blood to accumulate in the lower extremities and reduce cerebral blood flow to where a person might experience syncope (fainting). System in place… When a person stands up, baroreceptor reflexes are rapidly activated to restore arterial pressure (primarily through systemic vasoconstriction) so that mean arterial pressure normally is not reduced by more than a few mmHg when a person is standing compared to lying down.  Baroreceptor re ex Cardiovascular response in a person moving suddenly from a supine position to a standing position. Pa=arterial pressure; fl TPR=total peripheral resistance What about the gravitational effect on blood pressure in bigger animals?  How does the gira e produce the necessary blood pressure to lift blood up to its brain? The heart relative to the body weight of giraffes is similar to other mammals despite the high blood pressure, but the cardiac output is low and therefore the energy expenditure of the heart (relative to body weight) is similar to other mammals. Thick ventricular wall and a small ventricular lumen. (c) An original recording of aortic pressure (black), left ventricular pressure (red), and right ventricular pressure (blue) of an anaesthetized gira e ff ff Eckert, 2002 - Modified from White, 1972  Adaptation to posture changes The di erent gravitational e ects could cause a drop in pressure and back ow of blood to the brain, but it is prevented by a precise control and regulation of blood pressure and ow. 100 mmHg At the base of the giraffe’s brain is a complex maze of small blood vessels (rete mirabile) Venous valves in the jugular veins Vessels are extra thick and elastic Baroreceptor-mediated control of vascular tone Eckert, 2002 ff fl ff fl A sphincter-like structure in the conduit arteries at the knees and elbows, in combination with thick- walled small arteries in the legs, protects the lower limbs against high arterial pressure. A gira e wraps the legs with collagen to prevent blood from pooling in the lower legs ff  A snake that crawls on the ground has its head at more or less the same level as its heart, and if the head is tilted more than 45 degrees, blood ow to the head drops to zero. Tree-climbing snakes tend to have higher blood pressure and they maintain ow to the head well. Lillywhite, 1993 fl fl  The effect of gravity on position of the heart in three types of snakes. Lillywhite demonstrated a unique adaptation to gravity in aquatic, terrestrial, and tree-climbing snakes which are known to lack venous valves. In tree-climbing snakes, the closeness of the heart to the head and a slender body minimize gravitational pooling and assure adequate blood supply to the brain even during vertical climb (left). The effect of gravity is minimized in water snakes in which the heart is close to midline of the body (bottom, right). In terrestrial species the heart is positioned between the two extremes (top, right) Brachiosaurs were the heaviest and tallest sauropod dinosaurs for which complete skeletons exist  25 m What about the gravitational effects for a Brachiosaurus? 10 m Imagine a large brachiosaur eating leaves at a height ~25 meters, with its chest (heart) only ~10 meters above the ground. 0m Calculate the change in aortic blood pressure necessary for a brachiosaur to go from horizontal posture (heart, head & tail = same elevation) to vertical while standing up and graze the tops of trees. DENSITY(BLOOD) = 1 g/cm^3 = 10^3 kg/m^3 MANOMETRIC PRESSURE = 10^3 kg/m^3 * 9.8 m/sec^2 * 15 m = 1.47 x 10^5 Pa = 147 x 10^3 Pa = 147 kPa x (1/101.3 kPa/760 mm Hg) = ~1100 mmHg  What about the gravitational effects for a Brachiosaurus? More recently a popular idea is that the Brachiosaurus never lifted its head up but instead just moved it back and forth horizontally. Blood pumping would According to Dr. Michael Habib from the University of Southern get a boost any time the dinosaurs moved California, in sauropods motion acts as an accessory pump their necks. In sauropods, as the cervical ribs exed, they would have compressed towards the neck, and the muscle would have pushed on air sacs wrapped around the vertebral artery. Taylor MP, Wedel MJ. (2013) Why sauropods had long necks; and why giraffes have short necks. PeerJ 1:e36 https://dx.doi.org/10.7717/peerj.36 fl  What about 25 m the gravitational effects for a Brachiosaurus? 10 m The change in arterial blood pressure necessary for a brachiosaur to go from horizontal posture (heart, head & tail = same elevation) to vertical is about 1000 mmHg 0m If may have been possible for the same brachiosaur to hold his breath and forage underwater for plants on the bottom of a deep lake. If it stood up in the water to breathe but this time still fully submerged except for its nostrils, what would happen to the arterial blood pressure? Stay the same  Theoretical model of gravitational effects on blood vessels in the cardiovascular system. The hydrostatic pressure in water increases with depth and e ectively matches the increases in blood pressure due to gravity. In air, pressure increases with the height of the blood column and the blood tends to pool and distend the lower parts of the vasculature. In water, the increased hydrostatic pressure with increasing water depth cancels out gravity effects on the blood column. Modi ed from Satchell, G.H., 1991. Physiology and Form of Fish Circulation. Cambridge University Press fi ff  Pumps and Tubes: delivery and exchange How did living systems evolve and adapt to terrestrial gravity? https://www.youtube.com/watch?v=ue7ImjBIJ04 In vertebrate moving from water to land there was an extensive reorganization of the venous system. The gravitational e ect is a problem only for terrestrial animals! For a whale the water outside the animal is a ected by the same gravity of the water inside the animal. ff ff  In space there is no gravity to pull blood into the lower part of the body. Instead, blood goes to the chest and head, causing astronauts to have pu y faces and bulging blood vessels in their necks. The lack of blood owing to and from the brain can cause astronauts to feel dizzy and sometimes even faint when they return to Earth's gravity. Gravity also a ects the ow of blood through the brain; at accelerations beyond 5g, this begins to a ect the brain’s electrical activity, producing patterns that resemble epileptic seizures. ff ff fl fl ff  Case Study Hypothetical arterial blood pressures (mmHg) and tissue fluid accumulations on Earth and in actual microgravity, horizontal bed rest and 6 degrees head-down-tilt bed rest. Long-duration bed rest as an analog to microgravity vs. the 6 degree head-down tilt (HDT) bed rest. Alan R. Hargens, and Laurence Vico J Appl Physiol 2016;120:891-903 2016 ©2016 by American Physiological Society  Pumps and Tubes: Class 9 delivery and exchange How do the processes of small scale flow connect to large scale flow in order to guarantee both delivery and exchange? - Primary mechanisms of capillary exchange - Blood hydrostatic pressure and Blood colloidal osmotic pressure What is the effect of gravity on the cardiovascular system? - How the venous blood returns to the heart How did living systems evolve and adapt to terrestrial gravity? - Adaptation to posture change and different environments