IB Biology/Excretion

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[edit] Topic 12: Excretion

[edit] Excretion

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Outline the need for excretion in all living organisms.

• The idea behind excretion holds true for all living organisms. If excess toxins, salts, and water builds up it may cause serious bodily harm to that organism. The kidneys make sure that this doesn’t happen and allows for normal bodily functions to continue. If not for this system the organism may also end up needing to spend excessive amounts of energy to filter out the toxins that could kill it.

State that excretory products in plants include oxygen and carbon dioxide, and in animals, they include carbon dioxide from respiration, and nitrogenous compounds.

Excretory products in plants include oxygen, and in animals they include nitrogenous compounds and carbon dioxide.

Discuss the relationship between the different nitrogenous waste products and habitat in mammals, birds, and reptiles

• Any metabolism involving proteins and nucleic acids produces a nitrogen containing waste with the main waste product being Ammonia. The direct excretion of Ammonia, in one form or another, is the most biologically efficient way of disposing of waste. In fish ammonia can simply be excreted purely as it is extremely water soluble. Fishes mainly lose Ammonia through the epithelium of their gills as NH4+. Fresh water fishes also take up sodium as an exchange for the Ammonia. Animals, however, can not excrete pure Ammonia since it is too toxic to be excreted without first being diluted and terrestrial animals can’t dispose of it quickly enough. Thus mammals excrete urea, a product which is much less toxic than Ammonia and requires less water to be excreted which is important to terrestrial creatures where water is more scarce. Finally birds excrete Uric Acid as their form of Ammonia removal. It is much less soluble in water than Ammonia is, thus leaving much more water for the bird which is needed during long migration patterns. Uric acid can also precipitate, allowing for shelled offspring who are permeable to gas but not permeable to liquid, as Ammonia or Urea would be.

[edit] The Human Kidney

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Draw the structure of the kidney

Draw the structure of the glomerulus and associated nephron

Explain the process of ultra-filtration

• Blood pressure forces fluid from the capillaries of the Glomerulus across the Epithelium of the Bowman’s Capsule, and into the lumen of Nephron tubule. The porous capillaries act as a filter as they have membranes which are permeable to water and small solutes but not to blood cells or larger molecules. The efferent arteriole reabsorbs amino acids, glucose, water, and salts and NH2, excess water, and sodium chloride descend into the loop of Henle. There more water and sodium is absorbed and tubular excretion begins in distal convoluted tube. Large molecules which weren’t absorbed enter for excretion and the collecting duct takes it to the renal pyramid.
• 15-20% of blood plasma is filtered into glomerulus, that exit through fenestrated blood capilaries (porous). The basement membrane is a protein layer between the glomerulus and Bowman's Capsule that prevents blood cells and large proteins from entering the Bowman's Capsule.

Define osmoregulation

Osmoregulation - the control of water and solute levels

Explain the reabsorption of glucose, water, and salts in the proximal convoluted tube

• In the Proximal Convoluted Tubule there is selective re-absorption of water and salt, depending on how dehydrated the body is. In the presence of ADH, much more water is reabsorbed than when ADH isn’t present. Microvilli also helps to expand surface area to allow for more absorption. Filtration, on the other hand, is not selective at all as it is important that essential nutrients return to the body so sugar, vitamins, and other organic nutrients are reabsorbed into the filtrate. Some are actively transported (glucose, amino acids, sodium ions) and some are passively transported (H2O, potassium ions, chloride ions).

Explain the roles of the Loop of Henle, medulla, collecting duct and ADH in maintaining the water balance of the blood

• Water leaves the Nephron via Osmosis while in the descending limb of the Henle’s loop due to the increasing salt concentration of the medulla in the kidney. Blood will pass into the capillaries where it is removed and salt will diffuse into the filtrate. The ascending limb is impermeable to water, allowing various salts to leave. Fluid that leaves the loop is less concentrated than the tissue around it, and blood entering the medulla will lose water due to osmosis and pick up salt and urea through diffusion. The exact opposite happens in the ascending capillary. When a lack of water is detected in the kidney, ADH is released by the pituitary gland which increases permeability of the walls in the distal convoluted tube and the collecting duct. When ADH isn’t present, walls are impermeable and water is used to dilute urine.

Compare the composition of blood in the renal artery and renal vein, and compare the composition of the glomerular filtrate and urine

• Renal Artery – More Toxins
• Renal Vein - Less Toxins
• Renal Artery - Oxygenated
• Renal Vein - Deoxygenated
• Renal Artery - More Salt/ions
• Renal Vein - Less Salt
• Renal Artery - More H2O
• Renal Vein - Less H20
• Renal Artery - Less CO2
• Renal Vein - More CO2
• Renal Artery - More Nutrients
• Renal Vein - Less Nutrients
• Renal Artery - Supplies Kidneys with Oxygen
• Renal Vein - Returns blood from kidneys to Heart
• Renal Vein – Blood with no wastes,less O2, urea, salt/ions, and more CO2
• Glomerular Filtrate: Amino acids, glucose, Na+ Cl, NH2, Urea, Nutrient excess, Nitrogenous waste, H+, H20, hormones, vitamins
• Urine: Wastes: Urea, Na+, Cl, NH2, H2O, large molecules

Outline the structure and action of kidney dialysis machines

• Blood enters machine from patient’s vein and runs through partially permeable tubules and into the dialysis chamber. The tube allows nitrogenous waste to diffuse from the blood and into the dialysis fluid. Urea diffuses through the membrane, as dialysis fluid contains none, removing it from the body. Water and solutes will then be added to the blood if necessary by diffusion from the dialysis fluid which runs across the semipermeable tubules containing the circulating blood. The blood is then run through an air bubble trap before it is reintroduced to the vein.

Addtional Information:

Kevin Yang 12-15-07 IB Biology II H

IB Biology Excretory System Review Sheet

1.Why is excretion important in all living things? It eliminates waste product from life processes that if concentrated, may be harmful.

2.What are the organs of the excretory system? What do they excrete? The organs of the excretory system are the kidneys, skin, intestines, and lungs. The kidneys help excrete waste from blood. The skins excretes dissolved waste (salt, etc.). The lungs get rid of carbon dioxide and the intestines help get rid of nitrogenous wastes, salts, and water.

3.What are the excretory products in plants? Animals? The excretory products in plants are oxygen and in animals carbon dioxide.

4.What is the function of the respiratory system? The function of the respiratory system to to eliminate CO2 produced by the body.

5.What are the two systems involved in getting O2 in the body and CO2 out? How do they compliment each other? They are the respiratory and circulatory system. The respiratory gets the oxygen and delivers it to the blood. The blood delivers the oxygen to the cells and gets carbon dioxide which it deliveries to the respiratory to eliminate as waste.

6.Explain the difference between ventilation, gas exchange and cellular respiration. Ventilation is the actual inhalation and exhalation of air between the atmosphere and the lungs. Gas exchange is in the alveoli where oxygen is given to the red blood cells and taken away to be exhaled. Cellular respiration is where the oxygen is used in combination with sugar to make ATP (and release carbon dioxide).

7.Draw a picture of the organs involved in the respiratory system. Label the parts.

8.What are the 4 processes involved in respiration? Explain each. \During inhalation (inspiration), the diaphragm muscle contracts and flattens. The external intercostal muscles contract making the ribs and sternum go up. The volume increases making the pressure decrease, so air flows in.

9.Explain the relationship between the lung, visceral pleura, parietal pleura, and pleural cavity. Draw a diagram to help your explanation. The outer layer is attached to the wall of the thoracic cavity and is called the parietal pleura. The inn layer, the visceral pleura, covers the lungs. They are separated by the diaphragm.

10.How does the left lung differ from the right lung? The right lung has 3 lobes while the left lung only has 2.

11.Explain the features of alveoli and how they are adapted to gas exchange. The alveoli are very small air sacs surrounded by capillaries. They are moist, thin, and contain no cilia. This aids in O2/CO2's ability to diffuses through the membrane to the blood cells.

12.What is the purpose of mucus and cilia in the respiratory system? The mucus and cilia help filter out any solid particles. The moisture of the mucus helps humidify the air and keep it from drying out the throat and lungs.

13.Where is the diaphragm located in the relation to the lungs? What is its function? It is located under the lungs. Its function is to aid in breathing by forcing the lungs to expand and contract.

14.Explain the mechanism of ventilation in human lungs including the action of the intercostals muscles, diaphragm, and the abdominal muscles. During inhalation, the diaphragm muscle contracts and flattens. The external intercostal muscles contract making the ribs and sternum go up. The volume increases the making the pressure decrease, so air flows in. Exhalation is the same thing but in reverse.

15.What advantages are lost when a person breathes through the mouth instead of the nasal passages? The air is not humidified and particles are not filtered out.

16.What is the function of the epiglottis? The epiglottis prevents choking by closing the entrance to the windpipe during eating.

17.What is another name for the pharynx? Larynx? It is called the throat. It is the voice box.

18.Trace the path of air from the nasal passages to the alveoli. Air comes from the nasal passages (already filtered) to the pharynx to the larynx (if the epiglottis doesn't block it). Then it enters the trachea, down the bronchi, into the bronchioles and finally at the alveoli.

19.What is the function of the vocal cords? How do they work? The function of the vocal cords is to make sound.

20.Describe the make up of the trachea. The trachea has C-shaped rings lined with ciliated mucus that traps particles.

21.Explain how the exchange of gas takes place between both the alveoli and the capillaries and the capillaries and the tissues of the body. It takes place through diffusion, The low oxygen in the blood causes oxygen to go into the hemoglobin. The low amount of carbon dioxide in the lungs allows it to diffuse into the lungs. The same thing happens in the capillaries with waste products going into the blood and oxygen/nutrients going into the cell.

22.What is the function of the pulmonary artery? Pulmonary vein? The pulmonary vein takes blood from the heart to the lungs to be reoxygenated. The pulmonary artery takes reoxygenated blood from the lung and brings it back to the left atrium.

23.Diagram and explain the relationship between bronchi, bronchioles, and alveoli. The trachea splits into two bronchi, which splits into even smaller bronchioles. At the very end, a bunch of small sacs called alveoli remain.

24.How are red blood cells important to the respiratory system? They are the primary transporter of oxygen carbon dioxide which it is the job of the respiratory system to take in and eliminate.

25.What is hemoglobin? What is it made of? What is its function? Where is it found? How many oxygen can each molecule hold? It is a red pigment in red blood cells. It is made of a protein molecule called hemoglobin and a iron group called heme. It is found in erythrocytes. Each molecule can hold 4 O2 molecules.

26.What is oxyhemoglobin? How is it made? It is a hemoglobin that has combined with an oxygen molecule. It is made by combining a hemoglobin molecule with oxygen atoms.

27.How does pH and temperature affect oxygen saturation in the blood? Be sure to use the terms CO2 and lactic acid in your explanation. Too much lactic acid will reduce the amount of oxygen in the blood because the hemoglobin must get rid of the CO2 and acid. As you work, CO2 production increases, which increases the amount of H+ and lowers the pH. This causes the respiratory rate to increase.

28.How does hemoglobin act as a buffer in the blood? It helps turn carbonic acid into bicarbonate and hydrogen.

29.How does exercise affect breathing? As more exercise is done, the acid builds up in the blood, and breathing becomes faster in an effort to eliminate the acid.

30.What problem would a person who lives in Phoenix, Arizona (elevation 1000 feet) have if they ran a marathon in Flagstaff (elevation 7500 feet)? There is thinner air in Flagstaff and their lungs are not used to having to draw so much air in. Therefore, it is considerably harder to breathe.

31.Explain the differences between myoglobin and hemoglobin (make sure to tell where each is found.) Hemoglobin are found in red blood cells and carry oxygen. Myoglobin is found in muscle tissues. It does not use oxygen pressure to bind with O2 atoms but binds very well with oxygen atoms to allow organisms to hold their breath.

32.How does smoking affect the air passages? It can cause lung cancer and can irritate the bronchioles (which causes a great deal of clogging with mucus and asthma). It also freezes cilia.

33.What affects would lung cancer or asthma have on gas exchange? It would restrict the space in the bronchis and reduce the amount of gas exchange that can take place.

34.What is carbon monoxide? Where does it come from? Why is CO so lethal? Carbon monoxide is a compound made of 1 carbon atom and 1 oxygen molecule. It is colorless, odorless, and gaseous. It comes from combustion reactions and is present in the atmosphere. It is lethal because people are unaware they are breathing it in, it binds to the heme group on red blood cells, and refuses to come off. This causes eventual suffocation.

35.Name the parts of the urinary tract. What is function of each? The parts of the urinary tract are the kidneys, the ureters, the bladder, and the urethra. The kidneys produce urine, travels through the ureter to the bladder, where it is stored. Then they exit the body through the urethra.

36.In humans, what is the first waste product made that contains nitrogen? Why is it so dangerous ? The first nitrogen waste product is ammonia which is dangerous because it can easily turn into ammonium hydroxide which is a very strong base and will disrupt homeostatsis.

37.What are the two most common substances used by terrestrial animals to get rid of nitrogen? They get rid of it through uric acid or in urea with urine.

38.What is the difference between birds and lizards, fish and mammals in the way they get rid of their waste? Why are these differences important? Birds and lizards excrete it as uric acid in a solid form. Fish and mammals secrete it with water in a diluted urea solution. This is important so birds do not have to drink lots of water and lizards can conserve water. Fish and mammals have access to water, so they can excrete through urine.

39.Draw and label the parts of the urinary system.

40.What is filtrate? A filtrate is a substance that is forced through the glomerulus into Bowman's Capsule. IT is made of water, urea, glucose, amino acids, and various salts.

41.Draw a kidney. Label the parts including the cortex, medulla, pelvis, ureter, and renal blood vessels.

42.Draw and label a nephron.

43.What is glomerulus? The glomerulus is a group of capillaries that form a tight ball at the end of one nephron.

44.What is a osmoregulation? Osmoregulation is the absorption and excretion of water and dissolved substances (solutes) so that proper water balance is maintained between the organism and its surroundings.

45.Explain the process filtration and reabsorption. The filtrate enters the glomerulus with Bowman's capsule and substances are absorbed from the renal artery. Then it goes through the loop of Henle where some substances are reabsorbed by the renal vein (reabsorption).

46.Explain the role of the loop of Henle, medulla, and collection duct in maintaining the water balance of the blood. The loop of Henle takes in water and other substances and it is located in the medulla. The water that will not be retained is sent to the collection duct.

47.What is the difference in blood in the renal artery and renal vein? The renal artery is “bad” blood as it has not been filtered while the renal vei blood has been.

48.Compare the composition of filtrate and urine. Urine is 95% water and is much more diluted than filtrate.

49.What is the function of ADH in the role of maintaining a water balance in the blood? How does it work? Antidiuretic hormone or ADH from the pituitary is one factor influencing urine production. ADH promotes water retention by the kidneys. ADH is regulated by a negative feedback loop involving blood water and salt balances. ADH helps the kidney tubules reabsorb water the concentrate the urine. When blood levels are too high (when you've been drinking a lot of liquids) acts as a negative feedback to inhibit it the secretion of ADH so more water is released.

50.What would happen to the body if the kidneys failed? Excess wastes and fluids would build up and the body would poison itself.

51.What is kidney dialysis? How does it work? It is a machine that cleans blood every few days. It takes blood from the body, where it is filtered, and then it is returned to the body.