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Corresponds with chapter 36 665-675.  Excretion is the removal from the body of waste products of the metabolic pathways  Excretory organs tend to be.

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Presentation on theme: "Corresponds with chapter 36 665-675.  Excretion is the removal from the body of waste products of the metabolic pathways  Excretory organs tend to be."— Presentation transcript:

1 Corresponds with chapter

2  Excretion is the removal from the body of waste products of the metabolic pathways  Excretory 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 carbs  Removes the amino group (NH 2 ) and excretes it in the form of ammonia, urea, or uric acid  the removal of the amino group requires a set amount of energy  however when converting it the energy required changes

4  Ammonia little energy needed H toxic requires a lot of fluids to keep it under control N –H nitrogenous excretory product(w/ water) fish and aquatic animals H

5  Urea O H 2 N-C-NH 2 Needs energy Less toxic than ammonia Excreted in moderately concentrated solution (allows body water to be conserved) Advantage for terrestrial animals with limited access to water Main 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  Most animals have tubular organs that regulate the water and salt balance of the body  excrete metabolic wastes into the environment  May utilize other organs  Look at three examples, the planarian, the earthworm, and the arthropods

9  Planarians two strands of branching excretory tubules, open to the outside through the excretory pores flame cells along the tubules.each has a cluster of beating cilia cilia allows the fluid to move through the body and out rids the body of excess water and excretes waste

10  Earthworms body has segments and each segment has its own excretory structure nephridia nephridium has an ciliated opening and excretory pore as fluid moves through the tubule the composition is modified urine has salts, metabolic wastes, and water urine produced is equal to about 60% of its body weight. Excretion of ammonia is consistent

11  Extra credit give an example of an animal that doesn’t excrete what it was classified to excrete. why not?

12  Insects long set of thin tubules called Malpighian tubules attached to the gut uric acid is actively transported from surrounding hemolymph into these tubules water follows salt gradient established by active transport of K+ water and other materials are reabsorbed at the rectum uric acid excreted at the anus insects-> water =little rebsorbtion insects -> dry=lot of reabsorbtion-> semisolid mass of uric acid

13  Arthropods (others) excretory organs given different name,but the function is similar crustaceans remove wastes through diffusion across gills possess excretory organ green gland, in ventral portion of head region fluid collects in the tubules but is modified by time as it leaves Shrimp and pill bugs have Maxillary glands in maxillary segments Spiders, scorpions and other arachnids have coxal glands, located near one or more appendages Spherical sacs, wastes are collected from the surrounding blood and discharged at the pores at one to several pairs of appendages

14  Osmoregulation- to maintain particular ion concentrations in blood  Essential to maintain homeostasis b/c Ions like Ca 2+, Na+, K+ and PO 4- affect systems of the body  Necessary b/c few vertebrates have blood that is isotonic to the sea water

15  Cartilaginous fish concentration of various ions in blood is less than seawater blood plasma nearly isotonic with water b/c they pump it full of urea gives their blood same tonicity of water Do regulate concentration of solutes and have rectal glands that rids the body of excess salt  Marine bony fish Blood plasma is hypertonic to the marine environment (high in salts) avoid getting dehydrated lose water by osmosis, counteract by drinking sea water constant drinking causes the fish to acquire lots of salt, actively transport out into the sea through the gills kidneys conserve the water produces small amount of isotonic urine  Freshwater Bony Fish osmotic problems opposite to the marine gain water across gills and body surfac never drink water actively transport salt into blood across membrane of gills eliminate excess water by producing large quantities of dilute urine, discharge urine =1/3 of their body weight

16  What glands does a pill bug have?  What glands does a spider have?

17  Biological systems are affected by disruptions to dynamic homeostasis  dehydration  Kangaroo rat form concentrated urine(20x more concentrated than its blood plasma) survives using metabolic water derived using cellular respiration never drinks water adaptions allows for it to remain in water-salt balance

18  Seagulls, Reptiles, and Mammals kidneys are good at conserving water are able to drink sea water, unlike us seabirds and reptiles have salt glands that pump the salt out  Birds glands located near eye produces salty solution that is excreted through nostrils and drips off  In Sea Turtles salt gland is modified tear gland sea snakes located beneath the tongue  Commandeered a gland meant for another purpose to pump salt from the blood plasma and leave behind the water.

19  Name two ions that affect the body systems.

20 Urinary system

21  The urinary system includes the  Kidneys – the major organ that regulates excretion; regulator of blood compostion  Urine – the modified filtrate made by the kidneys which is conducted from the body by the other organs in the urinary system  Ureter – each kidney is connected to a ureter; a duct that takes urine from the kidney to the urinary bladder  Urinary bladder – where the kidney is stored until it is voided from the body  Urethra – 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 vagina  There is no connection between the reproductive and urinary system for females, but in males the urethra carries the sperm during ejaculation

22  Bean shaped, reddish brown organs  About the size of a fist  Each adult kidney weighs between 115 and 170 grams  Approximately 11 cm in length, 6 cm in width, and 3 cm thick  Located 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 lower  3 major parts of the kidney (actually 4)  The 3 parts are the renal cortex, the renal medulla and the renal pelvis  there is also the hilum – located medially and serves as the point of entrance and exit for the renal artery, renal vein and ureter  Renal cortex – outer region of the kidney with a somewhat granular appearance  Renal 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 ureter  Renal Vein – oxygen poor blood; drains the kidney and returns the blood to the superior vena cava  Renal artery – oxygen rich blood; brings blood to the kidney from the aorta  Ureter – 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

25

26  Each kidney is composed of over 1 million tiny tubules called nephrons; approximately 1.2 million  These are the functional units of the kidney  Hollow tubes composed of a single cell layer  The nephrons of a kidney produce urine  Some are located in the renal cortex, but others dip down into the renal medulla  The 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 capsule  Then the renal artery leads to the kidney and branches into arterioles, then tiny capillaries  The glomerulus is the ball of capillaries which stays in the bowman’s capsule  Blood is filtered as it passes through the glomerulus and the plasma is forced out of the capillaries into the bowman’s capsule  This plasma is now called a filtrate

27  the 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 medulla  Then 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 arterioles  This short segment of the ascending limb is called macula densa  This 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 duct  The collecting duct transports urine down through the renal medulla and delivers it to the renal pelvis  The 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

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29  Each nephron has its own blood supply  The renal artery branches into numerous small arteries, which branch into arterioles, one for each nephron  Each arteriole, named an afferent arteriole divides to form a capillary bed, the glomerulus, which is surrounded by glomerular capsule  The 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  An average human produces between 1 and 2 liters of urine  There are three steps in the process of how urine is made: filtration, reabsorption, and secretion  Glomerular filtration – the movement of small molecules across the glomerular wall into the glomerular capsule as a result of blood pressure  When 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 filtrate  Plasma proteins and blood cells are too big to enter the filtrate, so they remain in the blood as it flows into the efferent arteriole  Glomerular filtrate is protein free, but similar to blood plasma

31  Tubular reabsorption takes place when substances move across the walls of the tubules into the associated peritubular capillary network  Osmosis 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 capsule  Sodium 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 tubule  Urea is passively reabsorbed from the filtrate  Tubular 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  Kidneys have four major functions:  -excrete metabolic wastes  -maintain water-salt balance  -maintain pH  -secrete hormones (ex. erythropoietin, renin)

33  Water and salt reabsorption occurs through the wall of the proximal convoluted tubule.  This is important for excreting hypertonic urine ◦ Loop of nephron ◦ Collecting Duct ◦ Water => Aquaporins

34  Loop of the nephron ◦ Renal medulla  The 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  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  Water diffuses out the entire length of the descending limb due to this osmotic gradient.  Countercurrent mechanism ◦ Water 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 gradient ◦ Water defuses out into the renal medulla, and thus urine is hypertonic to blood plasma.

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38  Antidiuretic 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 + pressure  Less ADH = Less water reabsorption, more urine ◦ Ideally, dependent on how much water you drink  Diuretics (ex. caffeine and alcohol) interfere with ADH and cause an increased urine flow.

39  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  Renin (enzyme) ◦ Angiotensinogen  angiotensin I  angiotensin II  This 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  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  Bicarbonate Buffer System ◦ Respiratory, powerful, does most of the work regulating blood pH  Essentially, 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+


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