Essential idea: All animals excrete nitrogenous waste products and some animals also balance water and solute concentrations.

11.3 The kidney and osmoregulation

By Chris Paine

https://bioknowledgy.weebly.com/

The form in which nitrogenous waste is excreted reflects evolution and ecological niche occupied, by the animal.

http://images.mentalfloss.com/sites/default/files/styles/article_640x430/public/bird-poop-white-why_5.jpg

UnderstandingsStatement Guidance

11.3.U1 Animals are either osmoregulators or osmoconformers.

11.3.U2 The Malpighian tubule system in insects and the kidney carry out osmoregulation and removal of nitrogenous wastes.

11.3.U3 The composition of blood in the renal artery is different from that in the renal vein.

11.3.U4 The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.

11.3.U5 The proximal convoluted tubule selectively reabsorbs useful substances by active transport.

11.3.U6 The loop of Henle maintains hypertonic conditions in the medulla.

11.3.U7 ADH controls reabsorption of water in the collecting duct.

ADH will be used in preference to vasopressin.

11.3.U8 The length of the loop of Henle is positively correlated with the need for water conservation in animals.

11.3.U9 The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

Applications and SkillsStatement Guidance

11.3.A1 Consequences of dehydration and overhydration.

11.3.A2 Treatment of kidney failure by hemodialysis or kidney transplant.

11.3.A3 Blood cells, glucose, proteins and drugs are detected in urinary tests.

11.3.S1 Drawing and labelling a diagram of the human kidney.

11.3.S2 Skill: Annotation of diagrams of the nephron. The diagram of the nephron should include glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule; the relationship between the nephron and the collecting duct should be included.

11.3.U9 The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

http://www.bio.miami.edu/dana/dox/nitrogenouswaste.html

Mammals metabolize ammonia into a molecule called urea.

Much of metabolic waste is in the form of Nitrogen

Reptiles and birds go one step further, packaging their nitrogenous waste as uric acid. It requires more metabolic energy to make than urea, but is less toxic, and requires very little water to flush from the body.

Animals such as fish and amphibians, which have constant access to water flush their nitrogenouswaste primarily as ammonia.

Terrestrial animals, however, because they have less access to water, have been under selective pressure to "repackage" their toxic ammonia as less toxic molecules which can be flushed with less water

http://science.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecPhysio/44_08NitrogenousWastes_L.jpg

11.3.U1 Animals are either osmoregulators or osmoconformers.

Osmoconformers maintain an internal conditions that are equal to osmolarity of their environment.

Minimizing the osmotic gradient minimizes the water movement in and out of cells. A disadvantage is that internal conditions may be sub- optimal.

Most Osmoconformers are marine invertebrates, e.g. starfish.

Osmoregulators tightly regulate their body osmolarity, which always stays constant, irrespective of their environment.

Kidneys play a large role in osmoregulation by regulating the amount of water reabsorbed. A disadvantage is that osmoregulation costs the animal ATP.

Osmoregulators are much more common in the animal kingdom, e.g. bony fish.

Osmoregulation in saltwater fish Osmoregulation in freshwater fish

https://en.wikipedia.org/wiki/Osmoregulation#Regulators_and_conformers

11.3.U2 The Malpighian tubule system in insects and the kidney carry out osmoregulation and removal of nitrogenous wastes.

#Malpighian tubules are longer and more convoluted than shown in this simplified illustration, they extend into the body cavity, where they are surrounded by hemolymph.

http://biology-forums.com/index.php?action=gallery;sa=view;id=1281

*Hemolymph is a fluid (analogous to the blood) that circulates in the interior of the insect’s body remaining in contact with the tissues.

The removal of nitrogenous waste and osmoregulation in insects by the Malpighian tubule

*

#

http://i-biology.net/

11.3.S1 Drawing and labelling a diagram of the human kidney.

http://www.biologymad.com/resources/kidney.swf

11.3.U3 The composition of blood in the renal artery is different from that in the renal vein.

The kidney causes changes in the composition of blood

renal vein(filtered blood)

renal artery(unfiltered blood)

ureter(urine)

blood in the renal vein compared and contrasted with the renal artery has …• no change in proteins – not filtered• less urea and toxins#

• less oxygen*• more carbon dioxide*• less salts and ions$ (if in excess) • less water$ (if in excess) • less glucose*

*Oxygen and glucose are used for cell respiration in the kidney and carbon dioxide is produced.

ureatoxinswater saltsions

# Undesired waste is removed from the blood.

$ The blood water and salt concentration needs to be balanced (osmoregulation). The kidney helps by removing these molecules if in excess.

11.3.S2 Skill: Annotation of diagrams of the nephron.

11.3.S2 Skill: Annotation of diagrams of the nephron.

11.3.U4 The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.

filtration slits between foot projections of podocyte cellsact as a filter allowing only smaller molecules to be filtered.

The capillary wall is fenestrated (it contains pores) allowing fluid to move through it

The basement membrane only allows smaller molecules to be filtered

Ultrafiltration occurs in the Bowman’s capsule

http://cd1.edb.hkedcity.net/cd/science/biology/resources/animation/Topic16.swfEdited from: http://www.slideshare.net/gurustip/the-kidney

11.3.U4 The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.

Edited from: http://www.slideshare.net/gurustip/the-kidney

11.3.U4 The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.

Occurs in the Bowman’s/renal capsule;In the kidney cortex;The (entering) afferent arteriole has a larger diameter than the (leaving) efferent arteriole;This creates high pressure in the capsule;Some smaller molecules are forced out of the glomerulus/blood into the capsule;Through basement membrane and the fenestrations/pores in the capillary wall;filtration slits between foot projections of podocyte cells also act as a filter;Molecules in the filtrate include water, urea, glucose, amino acids, salts;Plasma proteins, platelets, and cells are too large so remain in the blood;Glomerular filtrate is then transported through the nephron;

Edited from: http://www.slideshare.net/gurustip/the-kidney

11.3.U5 The proximal convoluted tubule selectively reabsorbs useful substances by active transport.

This where most selective reabsorption occurs: All glucose, amino acids, vitamins and hormones are reabsorbed here, along with approx 80% of the mineral ions and water

microvilli cell lining to increase the surface area for the absorptionCarrier proteins and pumps are present to actively transport substances.

a large number of mitochondria provide ATP for active transport

PCT cell

capillary

lumen of the nephron

Selective reabsorption of useful substances from the proximal convoluted tubule (PCT) The PCT extends from the Bowman’s capsule to the loop of Henle

plasma

filtrate

11.3.U5 The proximal convoluted tubule selectively reabsorbs useful substances by active transport.

This where most selective reabsorption occurs: All glucose, amino acids, vitamins and hormones are reabsorbed here, along with approx 80% of the mineral ions and water

microvilli cell lining to increase the surface area for the absorption

a large number of mitochondria provide ATP for active transport

PCT cell

capillary

lumen of the nephron

Selective reabsorption of useful substances from the proximal convoluted tubule (PCT) The PCT extends from the Bowman’s capsule to the loop of Henle

• Amino acids, hormones mineral ions & vitamins are actively transported into the PCT cells

• Glucose is actively transported across the membrane in symport* with sodium

• Water follows the movement of the ions passively (by osmosis)

Due to high concentrations of recovered substances in PCT cells the substances can passively diffuse into the bloodstream (along the concentration gradient)

plasma

filtrate

*symport is a type of cotransport here a molecule of glucose and sodium are moved together in the same direction.

11.3.U6 The loop of Henle maintains hypertonic conditions in the medulla. AND 11.3.U7 ADH controls reabsorption of water in the collecting duct.

The job of the loop of Henlé is to generate a high concentration of solutes (low concentration of water) in the tissue fluid of the medulla compared to the filtrate in the nephron. This aids the reabsorption of water in the collecting duct.

Osmoregulation is the control of water and solute concentrations in the body fluids (e.g. the blood plasma).

The hormone ADH balances the water concentration of the blood by changing the permeability of the collecting duct.

11.3.U6 The loop of Henle maintains hypertonic conditions in the medulla.

11.3.U6 The loop of Henle maintains hypertonic conditions in the medulla.

11.3.U6 The loop of Henle maintains hypertonic conditions in the medulla.

11.3.U7 ADH controls reabsorption of water in the collecting duct.

11.3.U7 ADH controls reabsorption of water in the collecting duct.

11.3.U7 ADH controls reabsorption of water in the collecting duct.

http://highered.mheducation.com/sites/0072495855/student_view0/chapter20/animation__hormonal_communication.html

11.3.U8 The length of the loop of Henle is positively correlated with the need for water conservation in animals.

The kangaroo rat’s (Dipodomys nitratoides) loop of Henle is much longer than that of other rodents. This in part explains the kangaroo rat’s amazing ability to survive in deserts.

https://commons.wikimedia.org/wiki/File:TiptonKangarooRat.jpg

The kangaroo rat's kidneys are especially efficient and produce only small quantities of highly concentrated urine. They have very long loops of Henle which builds a higher ion concentration in the medulla. Therefore allowing more water to be reabsorbed in the collecting duct.

Kangaroo rats can concentrate urea to 3,500 mmol/l, whereas humans can only concentrate urea to 400 mmol/l.

Length of the loop of Henle and water conservation

11.3.U8 The length of the loop of Henle is positively correlated with the need for water conservation in animals.

The ion concentration in the medulla builds as the loop of Henle descends. A longer loop of Henle in implies a larger medulla (compared to the kidney size) than in animals with a shorter loop of Henle. The shows the relationship between relatively medullary area in the mammalian kidney and the maximal urine concentration* that can be produced.

http://www.open.edu/openlearn/nature-environment/natural-history/animals-the-extremes-the-desert-environment/content-section- 3.2

small medulla large medulla

Length of the loop of Henle and water conservation

*The higher the ion concentration the more water can be reabsorbed in the collecting duct making the urine more concentrated.

11.3.A1 Consequences of dehydration and overhydration.

Overhydration is less common and occurs when there is an over-consumption of water.

Dehydration is due to loss of water from the body so body fluids become hypertonic.

http://movietvtechgeeks.com/wp-content/uploads/2015/02/rafael-nadal-defeats-pablo-cuevas-rio-tennis-open-2015. jpg

Consequences of dehydration and overhydration

• thirst, small quantities of dark coloured urine

• lethargy, (exposure to higher levels of metabolic waste, reduced muscle effeciency)

• low blood pressure (reduced blood volume)

• raised heart rate (low blood pressure)

• Inability to lower body temperature (lack of sweat)

• in severe cases seizures, brain damage and death

• clear urine• swelling of cells due to osmosis

(from hypotonic body fluid)• Headache, disruption of nerve

function (Swelled cells)• In more serious cases delirium,

blurred vision, seizures, coma and death

11.3.A2 Treatment of kidney failure by hemodialysis or kidney transplant.

Treatment of kidney failure

https://commons.wikimedia.org/wiki/File:Patient_receiving_dialysis_03.jpg

Kidney failure is a condition in which the kidneys fail to adequately filter waste products from the blood. It can be caused by injury or disease symptoms vary depending on the seriousness and progression of the disease. If not treated kidney failure leads to death.g

Treatment of kidney failure focuses on two main approaches:• Hemodialysis• Kidney transplants

11.3.A2 Treatment of kidney failure by hemodialysis or kidney transplant.

https://commons.wikimedia.org/wiki/File:Hemodialysis-en.svg

Hemodialysis (commonly called kidney dialysis) is a process of purifying the blood of a person whose kidneys are not working normally.

Treatment of kidney failure Hemodialysis treatment lasts about four hours and is done three times per week. A person can be treated this way for years.

The Dialyser contains a semi-permeable membrane that allows small particles (e.g. urea) to diffuse through, but larger molecules and cells remain in the blood

Used dialysate collects filtered out small molecules such urea

Fresh dialysate contains*:• No urea – to encourage

diffusion from the blood• Glucose and other useful

molecules at optimal concentrations – to minimize loss from the blood.

• High solute concentration removes excess water.

*Other molecules and ions are present and therefore filtered/balanced, but these are the key components of the dialysate.

Saline solution prevents excessive water loss which could lead to dehydration.

11.3.A2 Treatment of kidney failure by hemodialysis or kidney transplant.

http://www.kalingahospital.com/data/images/transplant1.jpg

A transplant is the best long-term treatment.

Donors can be either:• Someone who has recently died• A person who has chosen to give up one of

their two kidneys

Donors and the recipient have to be a close match in both blood and tissues to minimize the chance of rejection*.

Treatment of kidney failure

*If the match is not close enough the receipient’s immune system will react to the new kidney as it would to a pathogen.

The transplanted kidney is grafted in to the lower abdomen with the renal artery, renal vein and ureter connected to the recipient’s blood vessels and bladder.

11.3.A3 Blood cells, glucose, proteins and drugs are detected in urinary tests.

http://learn.parallax.com/sites/default/files/content/Reference/Urinalysis/Multistix-Urinalysis-Color-Key.pnghttp://detoxlabs.com/wp-content/uploads/2014/08/pee-cup.jpg

Urinalysis

• Presence of blood cells infections, disease and some cancers.

• Glucose is a strong indication of diabetes.• Trace amounts of protein are normal

(some proteins are very small), but larger amounts indicate kidney disease.

• Drugs (or their breakdown products) can often be detected in urine samples

Diagnostic tests of urine samples provide an easy effective way to detect illness and drug abuse.

Processes that affect the metabolism affect the metabolic waste that is produced and then excreted in urine.

Bibliography / Acknowledgments

Bob Smullen