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by: Retta Mayert


Marketplace > University of Kentucky > Biology > BIO 152 > PRIN OF BIOLOGY II
Retta Mayert
GPA 3.54

Philip Bonner

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Philip Bonner
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This 15 page Class Notes was uploaded by Retta Mayert on Friday October 23, 2015. The Class Notes belongs to BIO 152 at University of Kentucky taught by Philip Bonner in Fall. Since its upload, it has received 11 views. For similar materials see /class/228203/bio-152-university-of-kentucky in Biology at University of Kentucky.




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Date Created: 10/23/15
Osmoregulation Osmoregulation is management of the body s water content and solute composition Solutes are molecules dissolved in water Osmoregulation is control of the movement of solutes between internal uids and the external environment Different kinds of animals have different strategies Osmoregulation also involves the removal of metabolic waste molecules before they accumulate to harmful levels Many animal species are osmoconformers they don t regulate the osmotic concentrations of solutes They have internal solute concentrations the same as the environmental uids These are almost all marine species saltwater not freshwater 442 Osmosis Osmosis is the diffusion of water from a region of higher concentration to one of lower concentration Diffusion never goes the other direction from low to high If two different water solutions are separated by a semipermeable membrane one that allows water to diffuse through it but not another kind of molecule and there are unequal concentrations of the other kind of molecule a solute molecule then water will move by diffusion osmosis from the region of low solute concentration to the region of high solute concentration The water molecules are actually moving from a region of high water concentration to low water concentration The concentration of water is reduced if there are solute molecules dissolved in it The solute molecules take up room that would otherwise be occupied by water molecules therefore there are fewer water molecules in a particular volume of water and thus water s concentration is lowered 711 Two different kinds of solute molecule diffuse independently of each other if a barrier is permeable to both 717 Passive and active movement of molecules across cell membranes Molecules can diffuse passively across cell plasma membranes as long as there is a pathway for them to follow and they are in higher concentration on one side than the other But if the cell wants to move molecules UP a concentration gradient energy must be used to do it because spontaneous diffusion always goes from a higher to a lower concentration 444 Saltwater and freshwater sh have opposite osmoregulatory strategies Many animals use a specialized tissue the transport epithelium to carry out the movement of solutes and water from internal uid to environmental uid and vice versa Transport epithelia involved in osmoregulation are analogous to the gas exchange surfaces where oxygen and carbon dioxide are exchanged Sometimes the two transport epithelia are the same as in fish Osmoregulatory transport epithelia in the gills of marine sh use active transport to move salt from the blood to seawater But freshwater fish actively pump salts into the blood from the dilute lowsalt esh water passing by the gill laments The solute concentration of seawater is higher than in sh blood Unless the marine sh counteract osmosis much of their water would diffuse into the seawater Thus saltwater sh save water and excrete large amounts of salt The urine has high a concentration of waste mostly urea Freshwater sh have the opposite problem their blood is saltier than the water they swim in they have to save salt and excrete lots of water and waste ammonia Saltwater Chondrichthyes cartilaginous sh sharks rays etc do the same things saltwater sh do but they have a trick to allow them to carry much more solutes in their tissues and uids They make a compound TMAO that protects proteins from damage by urea This allows them to keep high concentrations of urea in their blood and interstitial uid It also keeps the osmotic concentration of the blood the concentration of all the solutes in the blood including TMAO high so that the loss by diffusion of water from the animal s blood to seawater is reduced The salt concentration osmolarity of freshwater sh blood and interstitial uid is much higher than the water they swim in They have to excrete lowsalt urine to save salt but the urine must also be high volume so they can lose the large amount of water that enters the blood at the gills by osmosis 446 How to enjoy life and prosper in the desert don t drink Kangaroo rats get water from enzyme reactions of metabolism This is metabolic water They conserve water in three wa s 1 Their urine is very highly concentrated It is very low volume and contains very high solute concentrations mostly of urea 2 The Kangaroo rat trachea is long and convoluted and the surface is moist like all airway surfaces The inspired dry desert air is humidi ed by the airway surface water evaporating into it Evaporation cools the trachea surface When exhale the now very warm and humid air from the lungs comes in contact with the long convoluted cool trachea and the water condenses on the trachea surface 3 Behavior kangaroo rats live in deep cool burrows and never venture out until well a er sunset They return to their burrows before the morning sun warms them up m lnholmion M V Wmm ml an 5 mm mm we now H 77 M AZTN 1 AL Bi They y 0 miles per hour GO years Withoiit touching land A Pre or t 16 weather 39 l39t d 1 b 39 39 world39s most endangei 39 39 C 565 be saved Albatross W ngspans are up to 10 feet 448 Marine and freshwater osmoregulators must adjust their blood salt concentrations Some marine birds such as albatrosses eat mostly animals from the ocean and drink sea water They take in a lot of salt that they have to get rid of They remove salt from their blood and dump it back into the ocean Transport epithelia of the salt glands in their heads carry out active transport to move sodium and chloride from the blood to the nostril and then it drips back into the sea It s a great way to get rid of salt but it carries a cost 7 a huge amount of ATP must be used to drive the active tranport proteins of the salt gland epithelial cells Marine sh have the same problem of living in an environment that has higher salt concentration than their blood does so there is a constant movement of salt from the sea water into the sh s blood Fish solve the problem the same way albatrosses do but their salt active transporters are in their gill epithelial cells chloride cells In the albatross the countercurrent arrangement of the blood vessels and the salt gland tubes makes the process more ef cient because the concentration difference between sodium in the blood and sodium in the salt gland cell is always maximally high This makes it easier for the active transport pumps of the salt gland cells to move sodium and chloride faster and use less energy ATP doing it Recall that sh gill blood vessels are in counter current to the ow of water past them Thus sh have the same adaptation as albatrosses one that allows them to use a minimal amount of ATP energy to remove salt from blood and put it back in the sea water 449 Transport epithelia in excretory organs often have the dual functions of maintaining water balance and disposing of metabolic wastes Metabolic waste those bits of food molecules that can t be used is dissolved in water so it can be excreted The digestion of sugars carbohydrates produces almost entirely carbon dioxide and water molecules that are easily handled by animals Fats also produce mostly C02 and H20 but digestion of protein produces a lot of nitrogen compounds that must be eliminated from the body They can t be breathed out the way C02 is nor are they liquid like water The nitrogencontaining product of digestion is ammonia NH3 and ammonia is toxic in high concentrations So animals have to be careful about how they dispose of ammonia The nitrogen waste must be removed from the blood and eliminated via the excretory system primarily the urinary system in vertebrates This impacts osmoregulation because the nitrogen waste adds to the total concentration of solute molecules in the blood The problem of toxicity must be dealt with too There are different strategies for this Ammonia is the most toxic and it is secreted only by animals that can afford to excrete highvolume urine limiting this strategy to freshwater sh For other animals the most common strategy is to turn toxic ammonia into a lesstoxic form such as urea or uric acid But the cost of this strategy is that it takes energy to convert ammonia to urea and even more to convert it to uric acid Only animals that must excrete only small volumes of water eg ying creatures like birds and some insects can afford to waste energy on conversion of ammonia to uric acid Most other animals convert ammonia to urea a process that takes some energy but not a lot The lesstoxic compound urea can be kept dissolved in smaller volumes of water than can ammonia but in a greater volume than that in which uric acid can be tolerated Which compound is an animal s main waste molecule thus depends on lots of other aspects of its overall adaptive strategies All text Slide Cells require a balance between osmotic gain and loss of water All animals face the same central problem of osmoregulation 39OVeI time the rates of water uptake and loss must balance OAnimal cells which lack cell walls swell and burst if there is a continuous net uptake of water or shrivel and die if there is a substantial net loss of water Osmosis is the movement by diffusion of water from a higher concentration of water to a lower concentration of water across a semi permeable membrane The water concentration difference is due to osmotic concentration a higher chemical concentration a lower water concentration Osmotic concentration is the concentration of ALL the solutes present in a unit volume of water This includes all the salts especially Na and C17 other small molecules medium size molecules and large molecules such as proteins and carbohydrates 4410 Vertebrate style excretory systems Pressure ltration pushes small molecules out of the blood into the excretory tube Big things like cells and proteins stay in the blood The pressure comes from blood pressure of a closed circulatory system or some other source in other kinds of animals The strategy is rst to save the valuable molecules then put detoxi ed molecules into the urine then extract most of the water This last step is essential for animals that live in dry terrestrial environment without it they would have to drink huge amounts of water or adapt to a wetter perhaps aquatic environment In humans the fullyprocessed urine that is excreted is about 15 liters per day This is formed from l2000L of blood that go through the two kidneys each day rst about 180L goes through the lter and of that 180 liters only l5 liters of urine excreted About 999 of the veryvaluable sodium that was in the 180 liters of ltrate is removed from the urine and retained in the blood Most of the small molecules that go through the lter and end up in the urine are valuable WATER Na Cl39 sugars amino acids etc and are speci cally taken out of the urine and put back in the blood The liver is constantly working on toxic compounds drugs and other unusual molecules to alter and inactivate them The inactivated compounds are secreted near the urinary tubes and diffuse into them They are not retrieved from urine 4411 Simpler versions of excretory systems Flatworms and protonephridia Planaria have no heart no blood vessels and no blood pressure so they have to use another trick to get their interstitial uid to enter a tube where it can be processed and valuable molecules retrieved The cap cells of the ame bulb wave around and wash interstitial uid between the interdigitations of cap cell and tube cell and into the tube The cells of the tube can transport valuable molecules back into the interstitial uid and gastrovascular cavity The tubes ultimately dump their contents to the outside Via openings nephridiopores 4412 A somewhat more complex version of a urinary system Earthworm metanephridia Earthworms are segmented animals and the segments must be kept separate from each other Each segment has a metanephridium that begins as a funnellike opening the nephrostome in one segment The nephrostome leads to a tube that pierces the segment wall and enters the next posterior segment where it becomes the transport epithelium and retrieval of valuable molecules and insertion of some wastes occurs Cilia move body uids into the nephrostome The long collecting tubule in the next segment is the transport epithelium and it ends with the nephridiopore the opening to the outside There are two nephridiostomes and nephridiopores per segment The major waste product is urea in most terrestrial polychaete worm species 4413 Malpighian tubules carry out osmoregulation and excretion in insects Insects have open circulatory systems Thus the hemolymph which circulates throughout the animal picking up waste molecules and distributing nutrients is directly outside the Malpighian tubule cells The Malpighian tubule cells constitute the transport epithelium Salt water nitrogenous wastes and many other osmotic solute molecules are transported across the epithelial cell surface of the tubule into the lumen The tubule lumen is continuous with the gut lumen As the gut contents are transported farther back towards the rectum the cells of the hindgut and rectum selectively transport valuable molecules such as water nutrients salts etc across the epithelium out of the gut and back into the hemolymph In this strategy the excretory and digestive systems share some tissues 7 the hindgut transports into the hemolymph nutrient molecules from food as well as those that were first transported into the Malpighian tubule Terrestrial insects generally excrete urea Some mostly those species that have adapted to drier environments tend to excrete highly concentrated uric acid 4414 The mammalian kidneys are the primary organs homeostatically controlling the osmotic concentration of blood and interstitial uids The kidneys also control total body water volume and separate waste molecules primarily urea from valuable molecules and excrete the waste as concentrated urine Concentrated urine means that the chemical concentration of solutes in the excreted urine is very much higher than the concentrations found in blood or interstitial uid What the kidneys do is to separate the good molecules from the bad molecules and then extract most of the water from the bad molecule solution The kidneys are supplied with very large volumes of blood by large branches of the aorta known as the renal arteries Within the kidneys blood travels rapidly through smaller and smaller arteries until small arterioles enter the glomeruli glomerulus means ball in the kidney cortex outer portion and pours its blood into a ball of capillaries Blood pressure forces the liquid part of blood the plasma out of holes in the capillary lower left transmission electron microscope picture in the next slide through slit spaces between cells which wrap around the capillaries the podocytes and into the bag the glomerulus sits in The bag is Bowman s capsule and the space between the capillary covering podocytes and the edge of the bag is Bowman s space The liquid primary urine that enters Bowman s space contains everything blood contains except for cells and all large molecules such as proteins Cells and large proteins are too big to fit through the selective filter located between the capillary endothelial cells and the podocyte cells The liquid goes from Bowman s space into the proximal tubule then the Loop of Henle descending and then ascending portions into the distal tubule past the juxtaglomerular apparatus through the distal straight tubule into a collecting duct down through the medulla and out into the ureter The meters are tubes that transport fullyprocessed urine from the kidneys to the bladder where it is stored before excretion Each region of the nephron all the tubes between the arteriole and the collecting duct has different functions and each cooperates to form the urine In the glomerulus the blood is ltered in the proximal tubule the valuable small molecules nutrients like glucose amino acids vitamins etc in the ltrate are transported across the tubule and back into the blood of a nearby capillary In the loop of Henle the urine contributes most of its salt Nat CI to forming a salt concentration in the medulla that will be used later to extract water from the urine as it ows through the collecting ducts Nontext picture of a sheep s kidney showing the anatomy W Mm v r m l Nontext scanning and transmission electron microscope pictures of parts of a human glomeru us In the lower left picture a at section of a glomerulus capillary you can see the holes fenestrations in the capillary endothelial cell through which the uid part of blood is forced The FILTER is the grey band between the capillary cell and the ngers of the podocyte cell L 4415 and 4416 Kidneys remove waste urea from the blood without losing much salt and water The nephron and collecting ducts are the transport epithelium In humans the volume of fullyprocessed excreted urine is about 15 liters per day This is formed from l0002000 liters of blood that go through the two kidneys each day First about 180L goes through the lter and of the 180 liters only l5 liters of urine are excreted About 999 of the veryvaluable sodium that was in the 180 liters of ltrate is removed from the urine and retained in the blood In the proximal tubule valuable molecules are retrieved from the urine and put back into the blood The osmotic concentration of the urine does not change however because water can enter and leave the tubule the solute concentration is the same in urine and blood concentration of the urine hasn t happened yet it s just getting cleaned up a bit by retrieval of the good stuff The medulla of human kidneys has a much higher osmotic concentration than does the cortex so when the urine goes down the descending thin limb of the Loop of Henle LOH water diffuses out of the urine into the interstitial space making the urine more concentrated The cells of the ascending LOH are not permeable to water so as the concentrated urine goes up the tube most of its solute molecules leave the urine and enter the now lessconcentrated uid outside This loss of solute molecules lowers the osmotic concentration inside the tube The ascending LOH cells do not allow the waste molecule urea to cross the tube When the urine gets to the thick segment of the ascending LOH active transport uses ATP energy to pump out almost all the rest of the sodium and chloride that s still in the urine This leaves the urine in the tube hypoosmotic a lower solute concentration than interstitial uid outside This now verywatery urine goes into a collecting duct and heads back down into the medulla The medulla is still very high osmolarity so most of that water in the urine oods out through channels in the duct cell plasma membranes The water is moving from high to low concentration trying to dilute the high salt concentration outside the collecting ducts This is the nal concentrating step After the collecting duct ends the urine is maximally concentrated ie it contains the least of water The urea that was in the blood rode through all the tubes without much change until the collecting ducts As the water leaves the urine the urea becomes very concentrated This allows you to save water by excreting urinating a relatively small volume of water that has a lot of urea in it The countercurrent multiplier moves Na and Cl out of the ascending limb of Loop of Henle This high concentration of Na and Cl moves into the descending tube Much of Na and Cl stays in the medulla 4419 4421 Homeostatic control of kidney function by the brain and endocrine system If salt intake is high and or water intake is low the kidney can change its operation to secrete a lowvolume highsalt and highurea urine This allows you to conserve water while still getting rid of excess salt and urea If salt intake is low andor water intake is high the kidneys produce a highvolume lowsalt urine that allows you to get rid of excess water without losing essential salt These changes of function are controlled by nerves and hormones that affect the cells of the kidneys Nerve cells in the brain measure the concentration of sodium in the blood There are proteins osmoreceptors in the plasma membrane of brain neurons that change shape when the concentration of sodium in their environment changes These brain neurons are exposed to cerebrospinal uid CSF the interstitial uid of the central nervous system which is similar to but not exactly the same as blood If the osmoreceptors of the sodium sensor nerve cells detect too much sodium in the CSF they send a neural signal to cells in the hypothalamus telling them to secrete antidiuretic hormone ADH into the blood ADH moves through the blood to the kidneys where it causes water channels in collecting duct cells to open allowing more water to be extracted from the urine and put back into the blood This reduces loss of water and gives the brain time to signal you to drink more water so that your blood volume can go back up If your blood volume goes down bleeding a lot not drinking enough water too much salt in your diet the hormone angiotensin II is released into the blood where it activates proteins in the kidney tubules to remove more Na from the urine This increases the concentration of sodium and activates the osmoreceptors in the brain If your blood volume goes down so does your blood pressure Decreased BP causes the arteries to collapse a bit including the ones that feed blood into kidney glomerulus capillaries When that happens cells in the glomerular arteriole tunica media release the enzyme renin into the blood Renin produces angiotensin II which not only causes arterioles to pinch off a bit increasing peripheral resistance and blood pressure but also causes ADH release as above Nutrient Processing and Distribution Circulation Updated 103008 404 Animals are heterotrophic Heterotrophic means they don t make their own food They eat alreadyprepared nutrient molecules produced ultimately by plants and other autotrophic photosynthetic organisms The problem with being hetrotrophic is that you must have ways to get food into your body convert the nutrient molecules to forms your own cells can handle and then distribute the useful nutrients to all your cells You also have to have a way to get rid of waste molecules those molecules produced when you are turning food into useable molecules and then again when you actually use those molecules to make stuff in your cells 418 419 4110 NUTRIENT PROCESSING Simple animals have simple digestive systems Animal digestive systems range from the simple gastrovascular cavity to the complex multiorgan system found in humans The hydra is a carnivore which catches prey with stinging cells Gland cells of the inner cell layer secrete enzymes into the gastrovascular cavity which break down the prey bodies into smaller molecules These smaller molecules are taken up inside other cells of the hydra body wall which then distribute the nutrients to their neighbors Complex animals have digestive and circulatory systems linked to each other to move nutrients to tissues and cells The circulatory and digestive systems of more complex animals show similar differences in complexity because the two systems are intimately linked to facilitate transport of nutrients from the digestive to the circulatory system and then on to individual cells 4112 4114 The vertebrate mammalian version of a digestive system Even though complex it does the same things simple ones do It provides a location for digestion breakdown of large nutrient molecules to small ones oral cavity stomach small intestines and absorption of the small molecules from intestine to blood The circulatory system then distributes the small molecules to all the cells of the body 4115 Absorption of nutrients and transport to blood The small intestine Nutrient transport into and out of small intestine cells occurs by the movement of the now small molecules produced by digestion through channels in the small intestine cells top membrane the apical plasma membrane domain Everything that crosses the small intestine wall goes through the semipermeable plasma membrane This is a process of selective uptake of molecules from the outside to the inside only molecules that can fit into one of the channels are allowed into the intestine cells The surfaces of the simple columnar epithelial cells that face the inside of the intestine the lumen have lots of microvilli small cylinderss of plasma membrane that stick up into the lumen These microvilli increase the surface area many fold Increased surface area increases the rate at which molecules can cross the membrane and improves the efficiency of nutrient absorption a lot Once in the intestine epithelial cell the nutrient molecules are transported out the other end through protein channels in the bottom side plasma membrane When they leave the intestine cell they are located in the extracellular space where they can quickly diffuse into a nearby blood capillary and be distributed to all parts of the body in the blood 422 3310 Circulation is a means of bathing each cell with an internal environment uid The uid inside an aquatic animal may be similar to the outside environment or it may be quite different depending on the particular species strategy for coping with its environment The internal environmental uid of terrestrial animals is very different from the external environment but is similar to the internal environment uid of aquatic animals from which they evolved The simplest form of a circulatory system is the gastrovascular cavity which serves as both digestive and circulatory systems in many invertebrates In these animals the internal environmental uid is the same as the outside environment 423 3322 There are two kinds of circulatory systems 7 open and closed In open systems uid called hemolymph is pumped through short vessels that empty into tissue space Fluid in tissue spaces the space between and among cells is called interstitial uid There is no difference between the hemolymph and interstitial uid It s all hemolymph Open systems are found in animals such as insects arthropods mollusks In closed circulatory systems the circulating uid is blood and it is different from interstitial uid Interstitial uid is formed from blood Closed systems are found in earthworms squid octopi chordates Molecules move between blood and interstitial uid compartments by diffusion 424 425 The anatomy of hearts is different for different kinds of animals The particular kind of heart an animal has re ects its strategies for surviving in its particular environmental niche Fish have one atrium to receive blood one ventricle to pump it out to BOTH the gill and systemic capillaries Blood ow to fish tissues is slow because it goes through 2 capillary networks both of which reduce ow rates and blood pressure Because 02 gets to tissues slowly these animals cannot produce ATP energy rapidly and so have relatively low energy levels Amphibian hearts have 2 atria and l ventricle Ozrich and Ozpoor blood mix in the single ventricle causing the blood that goes to the capillaries to carry less oxygen than they would if the atria and ventricles were totally separate Reptiles have a septum in the ventricle that reduces mixing of oxygen rich and poor blood and diverts oxygenated blood mostly to one artery oxygenpoor blood mostly to the other Birds and mammals have 2 atria and 2 ventricles Such double circulation guarantees complete separation between Ozrich and ipoor blood More oxygen gets to tissues High pressure blood goes rapidly to tissues to maintain high metabolic rates Endotherms warmblooded animals need this 426 A four chambered heart The left ventricle sends blood into the aorta at high pressure The right ventricle does the same for blood going to the lungs Rapid circulation brings lots of new oxygen to tissue cells and takes away C02 double circulation means that each circuit the pulmonary and systemic is operated under high blood pressure and rapid ow This allows all the body tissues to be exposed to oxygenrich blood and to be able to carry out their activities at high rates relative to animals without separate atria and ventricles 427 428 A fourchambered heart works by having the atria ll with lowpressure blood and then contracting to send it to the ventricles which then contract strongly to send it at high pressure out to the lungs or peripheral tissues 429 The sequence of atrial contraction followed by ventricular contraction is controlled within the heart by electrical signals produced at the sinoatrial node and propagated to the cardiac muscle cells by specialized modi ed muscle cells The signal depolarization of muscle cell plasma membranes spreads rapidly from cell to cell in the two atria The spread from atrium to AV node is slow delaying ventricle contraction for 0l sec The AV node is insulated from the SA node by connective tissue Action potentials that spread through atrial myocardium drive the contraction that is measured as the BP of atrial systole Transmission from SA to AV node cells is slow and activation of AV cells is slow as is transmission through bundle bers Transmission along Purkinje bers is faster Fast 46Msec slow 01 7 2 Msec or so The bundle bers and Purkinje bers take the electrical signal down to the bottom tip of the ventricles before it spreads out to the cardiac muscle cells Contraction of the ventricles thus begins at the bottom apex and spreads rapidly to the top ensuring that the blood moves ef ciently out the top of the ventricles into the pulmonary artery and the aorta 4210 4214 Structure of blood vessels All blood vessels except capillaries consist of three distinct tissue layers From the inside out epithelium smooth muscle and connective tissue The tunica intima is made of a single layer of squamous endothelial cells and a thin outer covering of connective tissue The tunica media is made of smooth muscle cell layers and elastic connective tissue The media of arteries is thicker than that of veins The tunica adventitia is just a connective tissue wrap around the media The adventitia protects the vessel and attaches it to the surrounding tissues Remember that the only permeable vessels are the capillaries Molecules enter and leave the blood only at the capillaries Movement of tissues outside veins especially those caused by muscles squeezes the vessels and propels the blood back towards the heart guided by semilunar valves that prevent ow in the opposite direction away from the heart 4211 Blood pressure is highest in arteries and lowest in veins because of cross sectional area differences among the vessels BP is determined partly by cardiac output the volume of blood expelled from the heart per unit time and partly by peripheral resistance the resistance owing blood encounters in smaller blood vessels mostly arterioles Peripheral resistance is controlled mostly at arterioles Nerve signals hormones and stress control the smooth muscle cells of the tunica media Contraction of the smooth muscle cells causes the lumen diameter to decrease and the blood pressure to increase The BF increases and ow decreases because the total crosssectional surface area of the vessels has decreased due to contraction It s now a set of smaller pipes Blood ow through veins is aided by muscle activity and body movements squeezing the veins Veins below the heart have oneway ow valves in their lumen so the muscle aided local increase in BP causes blood to ow only one way 7 towards the heart 4215 Blood ow through capillary beds is regulated Small ringlike bundles of smooth muscle cells sphincters within the tunicae mediae of the smallest a1teries are signaled to contract or relax When the sphincters are contracted blood does not ow through the capillary fed by that arteriole The thoroughfare channel also called an arteriovenous shunt is always open Body temperature regulation is accomplished in large part by regulating blood ow through peripheral capillaries of the skin At any given time most of the capillaries up to 90 in an animal s body are not open Nontextbook picture A high magnification picture of an arteriole that has branched to form two smaller arterioles All of the connective tissue surrounding the a1terioles has been removed so you can see the outer surface of the tunica intima the layer of smooth muscle cells The unbranched part left probably has one to two layers of smooth muscle cells while the two smaller ones right most likely have only one layer You can clearly see that the muscle cells are oriented circumferentially and that when they contract they will reduce the diameter of the vessel concomitantly reducing the size of the open space inside the tube which reduces the rate of blood ow through the vessel Reduction of ow rate by squeezing the tube causes blood pressure to increase Arteriole tunica media smooth muscle cells will contract when they get signals from nerves or endocrine signals like adrenaline They control how much blood ows through vessels in different parts of an organisms body lye 24 canning eleclmn nuclogmyh o a blanching arlenole Showan me cucumlelcnlial anangemenl m n B We a 0th muscle Cal 5 Mlcugmph muncsy or J Desakx and Y UeharaJ 4216 Unlike movement of nutrient molecules out of the small intestine into connective tissue interstitial uid molecules moving from blood to interstitial uid and vice versa do not have to pass through a semipermeable membrane The edges of the endothelial cells of the capillary are only loosely held together so uid ows through the slits But cells and large molecules proteins can t t through the slits and so stay in the blood keeping the osmotic pressure concentration of solutes fairly constant To imagine what a capillary looks like think of a water lled balloon rolled up into a cylinder and attached to other cylinders at each end and wherever they meet the edges are held together by small spots of glue The small spots of glue keep the edges a small distance from each other The balloon is analogous to an endothelial cell the water represents the cytoplasm and the small distance between the edges of balloons are equivalent to the space through which molecules move N on textbook picture Lymph interstitial uid is the liquid part of blood that left a capillary but didn t return to a capillary Because blood cells are too big to t through the open spaces between capillary endothelial cells there are no blood cells in interstitial uid and lymph Lymph often has lymphocytes but no other blood cells Lymph vessels are blindended meaning one end is closed and the other open they begin blindly and they are not part of a circulatory system Liquid and molecules of interstitial uid enter the lymph capillaries by diffusing through slits between simple epithelial endothelial cells The liquid lymph moves towards the open end of the system where it is dumped into large veins venae cavae near the heart Movement is due to momentary pressure increases caused by muscle activity and motion of body parts Lymph vessels pressure is very low almost zero because they are not connected to the output side of the heart The only pressure they have is generated by being squeezed Systemic aneri 4217 Blood cells All blood cells are generated from a small population of stem cells that divide continuously to produce daughter cells that can differentiate into cells of all the blood cell lineages Erythrocytes are specialized for carrying oxygen from the lungs to peripheral tissues Basophil cells react to antigens and release histamine Histamine is a small molecule that causes endothelial cells of capillaries to increase the width to the little slits between blood capillary endothelial cells This lets more uid out of the blood causing edema swelling due to increased volume outside the blood vessels Eosinophils release antihistamines which help to turn down the effects of basophils Neutrophils are highly specialized to nd and kill bacteria The bodies of millions of neutrophils that gave their lives to protect yours is much of what you see as pus in infected tissues Monocytes don t stay in the blood long and when they leave the blood and enter surrounding tissue they differentiate to become macrophages cells that are vacuum cleaners that take in and destroy many different kinds of things including bacteria and other microorganisms and toxins The B and T lymphocytes are the most active cells of the immune system B cells make antibodies proteins that bind to foreign molecules and mark them for destruction by macrophages while T cells move around the body looking for foreign cells and tissues Unfortunately organ transplants are often seen as foreign to T cells and they try to kill it


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