11.3 The Kidney and Osmoregulation

Understandings

Syllabus Reference

11.3 The Kidney and Osmoregulation

Applications and Skills

Syllabus Reference

11.3 The Kidney and Osmoregulation

Answer these questions on your whiteboards

Starter

1. Define osmosis
2. Describe and explain the direction of net movement in this diagram
3. What issues might be faced by organisms that live in a) salt and b)fresh water?
4. Define Excretion

11.3 The Kidney and Osmoregulation

Guiding Questions

How do marine invertebrates avoid osmosis?

How does the habitat and the osmoregulatory mechanism influence the type of nitrogenous waste excreted?

What are osmoconformers and osmoregulators?

11.3 The Kidney and Osmoregulation

What is the difference between osmoregulators and osmocomformers?

11.3.U1 Animals are either osmoregulators or osmoconformers.

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

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

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• Osmoregulators are much more common in the animal kingdom

11.3 The Kidney and Osmoregulation

What is the difference between osmoregulators and osmocomformers?

11.3.U1 Animals are either osmoregulators or osmoconformers.

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

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

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

11.3 The Kidney and Osmoregulation

How do insects excrete wastes?

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

11.3 The Kidney and Osmoregulation

How do insects excrete wastes?

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

11.3 The Kidney and Osmoregulation

How do insects excrete wastes?

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

Via Active Transport. The salts helps the movement of water which in turn helps the movement of UREA

1. Hemolymph contains salts, water and uric acid
2. Actively transported into the Malpighian tubes
3. The fluid moves into the hindgut
4. Salts and Water are reabsorbed into the hemolymph
5. Uric acids and faeces are excreted

11.3 The Kidney and Osmoregulation

Where does our waste come from?

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

In mammals and most amphibians, ammonia can be toxic in high levels

Proteins

Nucleic Acids

Amino Acids

Nitrogenous Bases

Amino Groups (NH₂)

Most aquatic animals excrete ammonia (NH₃) which is water soluble

Most mammals excrete urea (NH₂)₂CO

Many reptiles and birds excrete uric acid

This takes energy to convert urea to uric energy, but saves more water 🡪 semi solid paste

11.3 The Kidney and Osmoregulation

Summary of

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

11.3 The Kidney and Osmoregulation

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

As tadpoles, frogs excrete ammonia, but once they become frogs they excrete urea, as they are not always surrounded by water

11.3 The Kidney and Osmoregulation

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

Organisms evolve to excrete wastes differently based on their habitat and this is evidence of evolution.

11.3 The Kidney and Osmoregulation

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

11.3 The Kidney and Osmoregulation

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

Ultrafiltration

Cortex

Medulla

Reabsorption of water

Pelvis

Collecting ducts in pelvis deliver urine to ureter

Ureter

Carries urine to the bladder

Renal Vein

Renal Artery

11.3 The Kidney and Osmoregulation

Blood in the renal vein compared and contrasted with the renal artery has …

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

renal vein

(filtered blood)

renal artery

(unfiltered blood)

ureter

(urine)

• no change in proteins – not filtered
• less urea and toxins
• less oxygen
• less glucose
• more carbon dioxide
• less salts and ions (if in excess)
• less water (if in excess)

urea

toxins

water

salts

ions

11.3 The Kidney and Osmoregulation

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

11.3 The Kidney and Osmoregulation

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

11.3 The Kidney and Osmoregulation

Balancing the blood

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

11.3 The Kidney and Osmoregulation

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

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

11.3 The Kidney and Osmoregulation

The Nephron is the functional unit of the kidney

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

Bowman’s Capsule

Ultrafiltration

Glomerulus

Delivers blood

Proximal Convoluted Tubule (PCT)

Distal Convoluted Tubule (DCT)

Loop of Henle

Osmoregulation

Collecting Duct

Urine to pelvis

Selective Reabsorption

Reabsorption

11.3 The Kidney and Osmoregulation

What is the structure of the Glomerulus?

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

Podocytes*

Capillary (Endothelium)

Fenestrations (gaps in the capillary)

Glomerular Space

These cells form a porous membrane surrounding the endothelial cells of the glomerulus.

Negatively charged glycoproteins form a mesh to avoid plasma proteins being filtered out

11.3 The Kidney and Osmoregulation

This shows the relationship between the Glomerus and the Bowman’s Capsule

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

Efferent = Exit

Afferent Arteriole

Efferent Arteriole

Check out the diameters

Lumen of the Bowman’s Capsule

Proximal Convoluted Tubule (PCT)

Glomerular Filtrate goes for further filtration and absorption in the nephron

Renal (Bowman’s) Capsule

11.3 The Kidney and Osmoregulation

Selective reabsorption of useful substances from the proximal convoluted tubule (PCT)

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

11.3 The Kidney and Osmoregulation

Selective reabsorption of useful substances from the proximal convoluted tubule (PCT)

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

microvilli cell lining to increase the surface area for the absorption

a large number of mitochondria provide ATP for active transport

PCT cell

lumen of the nephron

The PCT extends from the Bowman’s capsule to the loop of Henle

plasma

filtrate

• 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) through protein channels

11.3 The Kidney and Osmoregulation

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

11.3 The Kidney and Osmoregulation

PPQ

Checkpoint

11.3 The Kidney and Osmoregulation

11.3

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 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;

11.3 The Kidney and Osmoregulation

There is around 1 million of these nephrons in each Kidney

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

11.3 The Kidney and Osmoregulation

11.3 The Kidney and Osmoregulation

11.3 The Kidney and Osmoregulation

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

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..

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

11.3 The Kidney and Osmoregulation

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The Loop of Henle generates a high concentration of solutes in the cells and fluid of the medulla. Output of urine is more dilute than input

As solute conc. Increases in the medulla, an osmotic gradient is established. Wave leaves the filtrate by osmosis

Na⁺ is pumped out via active transport

Cl^- flows

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Overall Effects:

• Filtrate Volume decreases
• Output is more dilute (slightly)
• Large amounts of salts removed

Countercurrent flow maintains gradient

11.3 The Kidney and Osmoregulation

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

If a person is dehydrated, ADH(a hormone) acts on the walls of the collecting duct, producing aquaporins (channels), making it more permeable to water

Filtrate enters the collecting duct from the DCT

Water moves into the capillaries via osmosis

They flow in opposite directions, maintaining a concentration gradient – a counter-current system

11.3 The Kidney and Osmoregulation

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

11.3 The Kidney and Osmoregulation

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 The Kidney and Osmoregulation

PPQ

Checkpoint

a. osmoregulation is regulation of water and solute/salt balance/solute concentrations;

b. nephron (is the functional unit of the kidney/osmoregulates);

c. ultrafiltration in glomerulus / glomerular filtrate collected by Bowman’s capsule;

d. loop of Henle establishes/maintains hypertonic conditions in medulla;

e. osmosis/reabsorption of water (from filtrate) in the collecting duct;

f. brain/hypothalamus monitors blood solute concentration / pituitary secretes ADH;

g. ADH secreted when solute concentration of blood is too high/hypertonic/when dehydrated;

h. ADH increases permeability of collecting duct to water;

i. ADH causes more aquaporins (in membranes of collecting duct wall cells);

j. more water reabsorbed resulting in more concentrated/hypertonic urine/less volume of urine;

k. less/no ADH secreted when solute concentration (of blood) is too low/hypotonic;

l. less water reabsorbed resulting in dilute/hypotonic urine/large volume of urine;

Reject ‘water balance’ and ‘water concentration’ for mpa.

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11.3 The Kidney and Osmoregulation

11.3

11.3 The Kidney and Osmoregulation

Dehydration vs Overhydration

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.

• 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 The Kidney and Osmoregulation

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

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 (diabetes or high blood pressure) vary depending on the seriousness and progression of the disease. If not treated kidney failure leads to death.

How do you treat kidney failure?

11.3 The Kidney and Osmoregulation

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

11.3 The Kidney and Osmoregulation

Treatment of kidney failure

11.3

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

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 The Kidney and Osmoregulation

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

• 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

11.3 The Kidney and Osmoregulation

Vocabulary

https://quizlet.com/_8wxcax?x=1qqt&i=28b19k

11.3 The Kidney and Osmoregulation

11.3

https://create.kahoot.it/share/kidney/8ce46df8-65fa-4d94-b32f-f2cebb178965

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11.3 The Kidney and Osmoregulation Quiz