Presentation on theme: "KIDNEYS AND OSMOREGULATION"— Presentation transcript:
1 KIDNEYS AND OSMOREGULATION Corresponds with chapter 36
2 ExcretionExcretion is the removal from the body of waste products of the metabolic pathwaysExcretory organs tend to be tubular in both invertebrates and vertebrates
3 The breakdown of various molecules forms nitrogenous wastes. amino acids energy OR amino acids fats or carbsRemoves the amino group (NH2) and excretes it in the form of ammonia, urea, or uric acidthe removal of the amino group requires a set amount of energyhowever when converting it the energy required changes
4 Ammonia little energy needed H toxic requires a lot of fluids to keep it under controlN –H nitrogenous excretory product(w/ water)fish and aquatic animalsH
5 UreaOH2N-C-NH2Needs energyLess toxic than ammoniaExcreted in moderately concentrated solution(allows body water to be conserved)Advantage for terrestrial animals with limited access to waterMain form of waste for sharks, adult amphibians, and mammals
6 Uric acid Long complex series of enzymatic reactions that requires a lot of ATP Poorly soluble in water, it forms crystals Water conservation is needed because it can be concentrated more readily than urea, excreted in a dehydrated form Excreted by insects reptiles and birds
7 Possible to predict metabolic waste based on anatomy and environment EXTRA CREDIT:
8 Excretory organs among invertebrates Most animals have tubular organs that regulate the water and salt balance of the bodyexcrete metabolic wastes into the environmentMay utilize other organsLook at three examples, the planarian, the earthworm, and the arthropods
9 Planarianstwo strands of branching excretory tubules,open to the outside through the excretory poresflame cells along the tubules.each has a cluster of beating ciliacilia allows the fluid to move through the body and outrids the body of excess water and excretes waste
10 Earthwormsbody has segments and each segment has its own excretory structure nephridianephridium has an ciliated opening and excretory poreas fluid moves through the tubule the composition is modifiedurine has salts, metabolic wastes, and waterurine produced is equal to about 60% of its body weight. Excretion of ammonia is consistent
11 Extra creditgive an example of an animal that doesn’t excrete what it was classified to excrete.why not?
12 Insectslong set of thin tubules called Malpighian tubules attached to the guturic acid is actively transported from surrounding hemolymph into these tubuleswater follows salt gradient established by active transport of K+water and other materials are reabsorbed at the rectum uric acid excreted at the anusinsects-> water =little rebsorbtioninsects -> dry=lot of reabsorbtion-> semisolid mass of uric acid
13 Arthropods (others)excretory organs given different name,but the function is similarcrustaceans remove wastes through diffusion across gillspossess excretory organ green gland, in ventral portion of head regionfluid collects in the tubules but is modified by time as it leavesShrimp and pill bugs have Maxillary glands in maxillary segmentsSpiders, scorpions and other arachnids have coxal glands, located near one or more appendagesSpherical sacs, wastes are collected from the surrounding blood and discharged at the pores at one to several pairs of appendages
14 Osmoregulation in Aquatic Vertebrates Osmoregulation- to maintain particular ion concentrations in bloodEssential to maintain homeostasis b/cIons like Ca2+, Na+, K+ and PO4- affect systems of the bodyNecessary b/c few vertebrates have blood that is isotonic to the sea water
15 concentration of various ions in blood is less than seawater Cartilaginous fishconcentration of various ions in blood is less than seawaterblood plasma nearly isotonic with water b/c they pump it full of ureagives their blood same tonicity of waterDo regulate concentration of solutes and have rectal glands that rids the body of excess saltMarine bony fishBlood plasma is hypertonic to the marine environment (high in salts)avoid getting dehydratedlose water by osmosis, counteract by drinking sea waterconstant drinking causes the fish to acquire lots of salt, actively transport out into the sea through the gillskidneys conserve the waterproduces small amount of isotonic urineFreshwater Bony Fishosmotic problems opposite to the marinegain water across gills and body surfacnever drink wateractively transport salt into blood across membrane of gillseliminate excess water by producing large quantities of dilute urine, discharge urine =1/3 of their body weight
16 Extra credit What glands does a pill bug have? What glands does a spider have?
17 Osmoregulation among Terrestrial Vertebrates Biological systems are affected by disruptions to dynamic homeostasisdehydrationKangaroo ratform concentrated urine(20x more concentrated than its blood plasma)survives using metabolic water derived using cellular respirationnever drinks wateradaptions allows for it to remain in water-salt balance
18 Seagulls, Reptiles, and Mammals kidneys are good at conserving waterare able to drink sea water, unlike usseabirds and reptiles have salt glands that pump the salt outBirdsglands located near eye produces salty solution that is excreted through nostrils and drips offIn Sea Turtles salt gland is modified tear gland sea snakes located beneath the tongueCommandeered a gland meant for another purpose to pump salt from the blood plasma and leave behind the water.
19 Extra creditName two ions that affect the body systems.
21 The Urinary System (pg 670-673) The urinary system includes theKidneys – the major organ that regulates excretion; regulator of blood compostionUrine – the modified filtrate made by the kidneys which is conducted from the body by the other organs in the urinary systemUreter – each kidney is connected to a ureter; a duct that takes urine from the kidney to the urinary bladderUrinary bladder – where the kidney is stored until it is voided from the bodyUrethra – through which the urine is voided from the body; in males the urethra passes through the penis while in females the opening of the urethra is ventral to that of the vaginaThere is no connection between the reproductive and urinary system for females, but in males the urethra carries the sperm during ejaculation
22 Kidneys Bean shaped, reddish brown organs About the size of a fist Each adult kidney weighs between 115 and 170 gramsApproximately 11 cm in length, 6 cm in width, and 3 cm thickLocated on either side of the vertebral column just below the diaphragm, in the lower back, where they are partially protected by the lower rib cage; right is lower3 major parts of the kidney (actually 4)The 3 parts are the renal cortex, the renal medulla and the renal pelvisthere is also the hilum – located medially and serves as the point of entrance and exit for the renal artery, renal vein and ureterRenal cortex – outer region of the kidney with a somewhat granular appearanceRenal medulla – consists of 6-10 (8-18) cone shaped renal pyramids that lie on the inner side of the renal cortex, the apex of each pyramid terminates into what is called the papilla, which directs the urinary stream into what is called the minor calyx (numerous minor calyces expand into two or three open ended pouches called the major calyces, which feed into the pelvis)
23 Renal pelvis – the inner most part of the kidney, like a hollow chamber, also known as the expanded upper portion of the ureter (divides into 2 or 3 major calyces which divide into 8 minor calyces) ; urine collects in the renal pelvis and then is carried to the bladder by a ureterRenal Vein – oxygen poor blood; drains the kidney and returns the blood to the superior vena cavaRenal artery – oxygen rich blood; brings blood to the kidney from the aortaUreter – the muscular tubes which propel urine from the kidneys to the urinary bladder
24 Extra credit:what is an example of an organism that uses another gland meant for another purpose to excrete salt
26 NephronsEach kidney is composed of over 1 million tiny tubules called nephrons; approximately 1.2 millionThese are the functional units of the kidneyHollow tubes composed of a single cell layerThe nephrons of a kidney produce urineSome are located in the renal cortex, but others dip down into the renal medullaThe blind end of a nephron is pushed in on itself to form a cuplike structure known as the glomerular capsule (bowman’s capsule) – the outer layer of the bowman’s capsule is composed of squamous epithelial cells; the inner layer is composed of specialized cells that allow the easy passage of molecules; there is a visceral layer composed of podocytes which help the kidneys filter out substances and then the parietal layer which is composed of the squamous epithelial; blood enters the nephrons at the bowman’s capsuleThen the renal artery leads to the kidney and branches into arterioles, then tiny capillariesThe glomerulus is the ball of capillaries which stays in the bowman’s capsuleBlood is filtered as it passes through the glomerulus and the plasma is forced out of the capillaries into the bowman’s capsuleThis plasma is now called a filtrate
27 continuedthe filtrate travels along the entire nephron, from the bowman’s capsule the filtrate passes through the proximal convoluted tubule – lined by cells with many mitochondria and tightly packed microvilli; the longest and most convoluted segement of the nephron; its cell provides a much greater surface area for reabsorption and secretion; initially the proximal tube forms several coils followed by a straight segment which descends toward the medullaThen simple squamous epithelium appears in the loop of Henle (loop of nephron) which has a descending and ascending limb, near the end of the thick ascending limb, the nephron passes between its afferent and efferent arteriolesThis short segment of the ascending limb is called macula densaThis is followed by the distal convoluted tube (lined by cuboidal cells that reabsorb sodium and chloride from the tubular filtrate)Then several distal convoluted tubules enter one collecting duct (the distal convoluted tubules begin a short distance beyond the macula densa and extends to the point in the cortex where two or more nephrons join to form the cortical collecting ductThe collecting duct transports urine down through the renal medulla and delivers it to the renal pelvisThe filtrate is modified to form urine as it travels along the tube, the urine moves from the collecting ducts into the ureters, then into the bladder, and finally out through the urethra
29 Each nephron has its own blood supply The renal artery branches into numerous small arteries, which branch into arterioles, one for each nephronEach arteriole, named an afferent arteriole divides to form a capillary bed, the glomerulus, which is surrounded by glomerular capsuleThe glomerulus drains into an efferent arteriole which branches into a second capillary bed around the tubular parts of the nephron, these are called peritubular capillaries, which lead to venules that join to form veins leading to the renal vein, a vessel that enters the inferior vena cava
30 Urine formationAn average human produces between 1 and 2 liters of urineThere are three steps in the process of how urine is made: filtration, reabsorption, and secretionGlomerular filtration – the movement of small molecules across the glomerular wall into the glomerular capsule as a result of blood pressureWhen blood enters the glomerulus,blood pressure is sufficient to cause small molecules such as water, nutrients, salts, and wastes to move from the glomerulus to the inside of the glomerular capusle (note that the glomerular walls are very permeable)The molecules that leave the blood and enter the glomerular capsule are called the glomerular filtratePlasma proteins and blood cells are too big to enter the filtrate, so they remain in the blood as it flows into the efferent arterioleGlomerular filtrate is protein free, but similar to blood plasma
31 Urine process continued Tubular reabsorption takes place when substances move across the walls of the tubules into the associated peritubular capillary networkOsmosis of the water from the filtrate cannot occur yet because the osmolarity of the blood is essentially the same as that of the filtrate in the glomerular capsuleSodium ions are actively pumped into the peritubular capillary and then chloride ions follow so now the osmolarity of the blood is such that water moves passively form the tubule into the blood, 60-70% of salt and water are reabsorbed at the proximal covoluted tubuleUrea is passively reabsorbed from the filtrateTubular secretion is the second way substances are removed form the blood and added to tubular fluid; this process is like the body removing harmful compounds not filtered in the glomerulus
32 The Kidneys and Homeostasis Kidneys have four major functions:-excrete metabolic wastes-maintain water-salt balance-maintain pH-secrete hormones (ex. erythropoietin, renin)
33 Salt + Water BalanceWater and salt reabsorption occurs through the wall of the proximal convoluted tubule.This is important for excreting hypertonic urineLoop of nephronCollecting DuctWater => Aquaporins
34 Continued Loop of the nephron Renal medullaThe loop of the nephron is composed of a descending limb and an ascending limb.The bottom of the ascending limb is thin, and salt passively diffuses out.The upper part of the ascending limb is thicker and the salt is actively transported out.No water can leave the ascending limb because it is impermeable to water.
35 Continued Osmotic gradient in the tissues of the renal medulla; Salt > concentration in direction of the inner medulla.This is because the further up the thick part of the ascending limb the fluid goes, less salt is available for transport.The innermost medulla itself has the highest concentration of solutes;Because urea leaks out of the collecting duct.
36 ContinuedWater diffuses out the entire length of the descending limb due to this osmotic gradient.Countercurrent mechanismWater leaves the descending limb, and as it diffuses out, the remaining fluid contains a greater osmotic concentration of solutes, and therefore can diffuse through the limb from top to bottom.The collecting duct also has the osmotic gradientWater defuses out into the renal medulla, and thus urine is hypertonic to blood plasma.
38 ADH + ReabsorptionAntidiuretic hormone regulates urine formation and excretion.This is released by the posterior lobe of the pituitary gland.More ADH = More water reabsorption, less urine, raise in blood volume + pressureLess ADH = Less water reabsorption, more urineIdeally, dependent on how much water you drinkDiuretics (ex. caffeine and alcohol) interfere with ADH and cause an increased urine flow.
39 Hormones + Salt Reabsorption 99% of Na+ filtered at the glomerulus returns to blood; 67% reabsorbed at the proximal convoluted tubule; 25% extruded by the ascending limb.Blood volume + pressure is partially regulated by salt reabsorptions.When glomerular filtration can not be supported, renin is secreted.
40 Continued Renin (enzyme) Angiotensinogen angiotensin I angiotensin IIThis vasoconstrictor stimulates adrenal glands on the kidneys to release aldosterone.Aldosterone is a hormone that promotes excreting K+ and absorbing Na+ at the distal convulted tubeule.Water reabsorption follows and blood volume + pressure increase (and therefore glomerular filtration can now occur).
41 ANH Atrial Natriuretic Hormone does the exact opposite. Secreted by the atria of the heart when cardiac cells get too stretched from higher blood volume and pressure.Inhibits the secretion of renin (from the juxtaglomerular apparatus) and aldosterone (from the adrenal cortex)As a result, natriuresis occurs (increased secretion of Na+ and water, lowering blood volume + pressure.Other hormones secreted to regulate other ions as well ( ex. K+, HCO3-, Mg2+)
42 Acid-Base Balance (pH) Bicarbonate Buffer SystemRespiratory, powerful, does most of the work regulating blood pHEssentially, kidneys reabsorb bicarbonate ions and excrete hydrogen ions as needed.pH high (acidic) = Hydrogen excreted and bicarbonate reabsorbed.pH Low (basic) = Hydrogen excreted, but bicarbonate NOT reabsorbed.Urine is usually acidic, showing excess hydrogen is usually excreted.Ammonia = NH3 + H+ = NH4+