5.2 Excretion

What are the main metabolic waste products in mammals?

1. Carbon dioxide --\> waste product of cellular respiration, excreted from the lungs

2. Bile pigments --\> forned from the breakdown of haemoglobin from old red blood cells in the liver, excreted in the bile from the liver into the small intestine

3. Nitrogenous waste products (urea) --\> formed from the breakdown of excess amino acids by the liver

What is excretion?

Excretion is the removal of toxic waste products of metabolism and substances in excess of requirement from the body

Why is excretion important?

Some metabolic products, like CO2 and ammonia, are toxic. They interfere with cell processes by altering the pH, which would prevent normal metabolism. Other products may act as inhibitors and reduce enzyme activity.

Generally, excretion is a key process in homeostasis + is important in maintaining metabolism as metabolic waste can have serious negative consequences on the body if allowed to accumulate.

What is the source of carbon dioxide and what is its effect on the body if accumulated?

Source: the decarboxylation of respiratory substances during aerobic respiration in mitochondria

Effect: cell damaged if blood pH falls below normal range

What is the source of ammonia and what is its effect on the body if accumulated?

Source: the deamination of excess amino acids in liver cells

Effect: increases cytoplasm and interferes with metabolic processes and receptors for neurotransmitters in the brain

What is the source of urea and what is its effect on the body if accumulated?

Source: the ornithine cycle in liver cells

Effect: urea readily diffuses into cells - this decreases their water potential and causes them to absorb water by osmosis and expand until they burst

What is the source of uric acid and what is its effect on the body if accumulated?

Source: breakdown of adenine + guanine in the liver

Effect: uric acid may form crystals in joints causing gout

What is the source of bile pigments and what is its effect on the body if accumulated?

Source: breakdown of the haem groups of haemoglobin in liver cells

Effect: bile pigments accumulate in skin, turning it yellow

What are the functions of the liver?

- breakdown of unwanted or toxic substances
- production of excretory waste

What supplies the liver with oxygenated blood?

Heptaic artery

Oxygenated blood from the heart travels from the aorta via the hepatic artery into the liver. This supplies the oxygen essential for aerobic respiration. Liver cells are very active as they carry out many metabolic processes which require energy in the form of ATP

What supplies the liver with deoxygenated blood?

The liver receives deoxygenated blood from the digestive system via the hepatic portal vein.

This allows the liver to absorb and metabolise many of the nutrients that are absorbed into the blood in the small intestine

How does deoxygenated blood leave the liver?

Via the hepatic vein which flows back to the heart

What is the forth vessel connected to the liver?

The bile duct --\> carries bile from the liver to the gall bladder, where it is stored until required to aid the digestin of fats in the small intestine.

What cells is the liver made up of?

hepatocytes

Internal structure of the liver:

- the liver is divided into many lobules, which are separated from each other by connective tissue
- branches of the hepatic artery and the hepatic portal vein supply each lobule with blood
- this blood is carried in wide capillaries (sinusoids)
- Each lobule is also connected to a branch of the hepatic vein that drains blood away from each lobule

Explain the blood flow in the liver

As the hepatic artery + hepatic portal vein enter the liver, they split into smaller vessels which run between and parallel to the lobules (inter-lobular vessels).

At intervals, branches from the hepatic artery + the hepatic portal vein enter the lobules. The blood from the 2 blood vessels is mixed + passes along a chamber (sinusoid).

As blood flows along the sinusoid, which is lined with liver cells, the liver cells are able to remove substances from the blood and return other substances to the blood.

What functions do hepatocytes carry out?

-The storage of glycogen
-The formation of urea
-Detoxification

The liver's role in the storage of glycogen:

- The liver vitally converts glucose into glycogen in a process known as glycogenesis.
- The conversion helps to regulate blood glucose concentration.
- Insulin triggers glycogenesis after it detects an increased blood glucose concentration.
- The synthesis of glycogen removes glucose molecules from the bloodstream and decreases the blood glucose concentration to within a normal range
- Glycogen acts as a compact and efficient carbohydrate storage molecule

Glycogenesis is the synthesis of glycogen from glucose molecules

The liver's role in the formation of urea:

- Instead of being secreted, excess amino acids are deaminated. This means that the amino (-NH2) group is removed.

Why is it bad for ammonia to build up in the blood?

Ammonia is a very soluble and highly toxic compound that is produced during deamination

This is avoided by converting ammonia to urea, which is less soluble and less toxic than ammonia

What is the ornithine cycle?

Ammonia is converted to urea by combining it with CO2 and the amino acid ornithine

What happens in the Ornithine Cycle?

-Ammonia is combined with carbon dioxide to form urea
- This occurs in a series of reactions in the Ornithine Cycle
- During this cycle, ammonia and carbon dioxide and the amino acid Ornithine are converted to Citrulline using energy from 2 ATP molecules.
- This is converted to arginine by addition of further ammonia and another ATP molecule
- Ornithine is recycled through the metabolic breakdown of Arginine by Arginase and water. The by-product is urea.
- The urea diffuses through the phospholipid bilayer of the membranes of the hepatocytes and is then transported to the kidneys dissolved in the blood plasma

SIMPLIFIED ornithine cycle:

- Ammonia + CO2 + Ornithine produces H20 + Citrulline

- Citrulline then reacts with more ammonia to produce H20 + arginine

- Arginine then reacts with water to produce Urea + Ornithine

- Ornithine then further helps break down ammonia to produce urea in future reactions

What do the lungs excrete?

carbon dioxide - every living cell in the body produces CO2. CO2 is then passed into the bloodstream (mostly in the form of hydrogencarbonate ions) to the lungs. In the lungs CO2 diffuses into the alveoli to be excreted as you exhale.

What does the liver do?

- Products are passed into bile for excretion with the faeces

- The liver is also involved in converting excess amino acids into urea. Amino acids are broken down in deamination. The nitrogen-containing part of the molecule then combines with CO2 to make urea

What is the process of deamination ?

The process by which amino acids are broken down if there is an excess.

The amino group is removed and forms the very soluble and highly toxic compounds, ammonia.

This is then converted to urea which is less soluble and less toxic. Urea is then transported to the kidneys for excretion.

The remaining keto acid may enter the Krebs cycle (in the mitochondria) to be respired, or converted to glucose, or converted to glycogen or fat for storage. The keto acid will be respired to restore energy from the amino acid

What are the liver's metabolic functions?

- control of blood glucose levels, amino acid levels + lipid levels
- synthesis of bile, plasma proteins + cholesterol
- synthesis of red blood cells in the foetus
- storage of vitamins, A, D and B12, iron + glycogen
- detoxification of alcohol + drugs
- breakdown of hormones
- destruction of red blood cells

Why does the liver store glycogen?

This glycogen can be broken down to release glucose into the blood as required

What cells does the liver contain for detoxification?

- Catalase \= converts hydrogen peroxide to oxygen + water.

- Cytochrome P450 \= group of enzymes used to breakdown drugs

What is detoxification?

The liver detoxifies substances that may cause harm.

Toxins can be rendered harmless by oxidation, reduction, methylation or by combination with another molecule

Liver cells contain many enzymes that render toxic molecules less toxic.

What is the central vein?

The central vein (intralobular vessel) is a branch of the hepatic vein that drains blood from the liver back to the heart. The central vein carries deoxygenated blood away from the lobule.

Blood flows out of the sinusoids into the central vein, removing detoxified substances and metabolic end products.

What are sinusoids?

capillaries in the liver. They form from branches of the portal vein and hepatic artery. They are where the blood from the hepatic artery and hepatic portal vein are mixed. They then enter the different vessels inside lobules.

What are Kupffer cells?

Kupffer cells are specialised macrophages which move about within sinusoids.

What is the function of a Kupffer cell?

Their primary function is to breakdown and recycle old red blood cells.

They also engulf bacteria and debris and are involved in the digestion of haemoglobin which produces bilirubin.

What is bile canaliculi?

Fine channels that run parallel to sinusoids.
They are small ducts between hepatocytes that collect bile produced by the hepatocytes. The bile is then drained into the gallbladder

What is the portal triad?

Consist of the hepatic portal vein, the hepatic artery and the bile duct

What are hepatocytes?

functional cells of the liver - they play roles in metabolism + detoxification.

How is alcohol detoxified?

- Alcohol is first broken down in hepatocytes by ethanol dehydrogenase to ethanal.
- This is dehydrogenated further by the enzyme ethanal dehydrogenase.
- The final compound is ethanoate (ethanoic acid)
- Ethanoate combines with coenzyme A to form acetyl coenzyme A.
- This enters respiration
- The hydrogen atoms released in the process are combined with the enzyme NAD to produce reduced NAD.

What is the role of the kidneys?

- Removal of nitrogenous waste from the body
- Osmoregulation \= the mechanism by which balance of water + dissolved solutes is regulated

What is the structure of the kidney?

-Renal Cortex
-Medulla
-Renal Pelvis
-Renal Artery
-Renal Vein

What is the glomerulus?

A bundle of capillaries that are contained within the Bowman's capsule

What is the efferent arteriole?

Takes filtered blood away from the glomerulus and to more capillaries surrounding the rest of the tubule

What is the afferent arteriole?

The arteriole that takes blood into each glomerulus

Explain the difference in width of the efferent and afferent arteriole

The afferent arteriole is wider than the efferent arteriole. The difference in diameters ensure that the blood in the capillaries of the glomerulus maintains a pressure higher than the pressure in the Bowman's capsule. This pressure difference tends to push fluid from the blood into the Bowman's capsule that surrounds the glomerulus.

What is the renal artery?

The artery that brings oxygenated blood from the heart TO the kidney via the aorta

What is the renal vein?

Returns deoxygenated blood to the heart via the vena cava

What is the cortex of the kidney?

outer layer of the kidney

What does the cortex contain?

the glomerulus, bowman's capsule, proximal convoluted tubule and distal convoluted tubule of the nephrons

What is the medulla?

Inner region

What does the medulla contain?

loops of henle and collecting ducts

What is the renal pelvis?

A funnel-shaped cavity that collects urine into the ureter \= where the ureter joins the kidneys

What is the loop of Henle?

The big dip in the center of the nephron

After selective reabsorption, the filtrate passes through this structure which acts as a countercurrent multiplier.

In the descending limb of the loop of Henle, the water potential of the fluid is decreased by the addition of mineral ions + the removal of water

In the ascending limb of the loop of Henle, the water potential is increased as mineral ions are removed by active transport.

What is Bowman's capsule?

C-shaped structure partially surrounding the glomerulus. The bowman's capsule leads into the rest of the tubule.

How is the PCT adapted for reabsorption?

The cells of these tubules have a high folded surface producing a brush border which increases the surface area

What happens in the proximal convoluted tubule?

In the PCT, the fluid is altered by reabsorption of all sugars, most mineral ions and some water.

What is a single nephron made up of?

- The Bowman's capsule + glomerulus
- The Proximal convoluted tubule
- The loop of Henle
- The Distal convoluted tubule
- Collecting duct

What is ultrafiltration?

Small molecules (amino acids, water, glucose, urea + inorganic ions) are filtered out of the blood capillaries of the glomerulus and into the Bowman's capsule to form glomerular filtrate.

Red blood cells, white blood cells and platelets remain in the blood as they are too large to pass through the holes in the capillary endothelial cells.

Why does ultrafiltration occur?

Ultrafiltration occurs due to the difference in water potential between the plasma in the glomerular capillaries and the filtrate in the Bowman's capsule.

Overall, the effect of the pressure gradient outweighs the effect of the solute gradient. Therefore, the water potential of the blood plasma is higher than the water potential of the filtrate in the Bowman's capsule. This means that as blood flows through the glomerulus, there is an overall movement of water down the water potential gradient from the blood into the Bowman's capsule.

How does pressure affect water potential and therefore how does pressure affect ultrafiltration?

As the afferent arteriole is wider than the efferent arteriole, the blood pressure is relatively high in the glomerular capillaries
This raises the water potential of the blood plasma in the glomerular capillaries above the water potential of the filtrate in the Bowman's capsule.
Water therefore moves down the water potential gradient, from the blood plasma to the glomerular capillaries into the Bowman's capsule.

How does solute concentration affect water potential and therefore how does solute concentration affect ultrafiltration?

Plasma proteins are too big and can't pass through the basement membrane so they stay in the blood. Resultantly, the solute concentration in the blood plasma in the glomerular capillaries is higher than that in the filtrate in the Bowman's capsule. This makes the water potential of the blood plasma lower than that of the filtrate in the Bowman's capsule
This results in water moving down the water potential gradient from the Bowman's capsule into the blood plasma in the glomerular capillaries.

What are the three layers of the barrier between the blood in the capillary and the lumen of the Bowman's capsule?

1. The endothelium of the capillary
2. The basement membrane
3. The epithelial cells of the bowman's capsule

How is the endothelium of the capillary adapted to enable ultrafiltration?

There are narrow gaps between the cells of the endothelium of the capillary wall. The cells of the endothelium also contain pores (fenestrations). The gaps allow blood plasma and the substances dissolved in it to pass out of the capillary.

How is the basement membrane adapted to enable ultrafiltration?

This membrane consists of a fine mesh of collagen fibres and glycoproteins. This mesh acts as a filter to prevent the passage of molecules with a relative molecular mass of greater than 69,000. This means that most proteins are held in the capillaries of the glomerulus.

How are the epithelial cells of the bowman's capsule adapted to enable ultrafiltration?

These cells (podocytes) have a specialised shape - they have many finger-like projections, called major processes. On each major process are minor/foot processes that hold the cells away from the endothelium.

These projections ensure that there are gaps between the cells. Fluid from the blood in the glomerulus can pass between these cells from the lumen of the Bowman's capsule. They act as a filtration method. Podocytes have foot processes called pedicels. Pedicels wrap around the capillaries and leave slits between them. Blood is filtered through these slits.

What is selective reabsorption?

The uptake of specific molecules and ions from the glomerular filtrate in the nephron back into the bloodstream. Most of the reabsorption occurs in the proximal convoluted tubule.

How is the lining of the proximal convoluted tubule adapted to carry out reabsorption?

- Has microvilli \= increases the surfcace area

- Contains co-transporter proteins \= each specific co-transport protein transports a specific solute across the membrane

- High number of mitochondria \= provide energy for sodium-potassium pumps

- Tightly packed cells \= means no fluid can pass between the cells

Outline the stages of selective reabsorption:

1. On the cell surface membrane closest to the blood capillary, there are sodium-potassium pumps which actively transport sodium ions OUT of the cell and potassium ions IN the cell
2. As sodium ions move out of the cell, the concentration of sodium ions inside the cell drops, creating a concentration gradient.
3. This allows sodium ions to diffuse into the cell from the proximal tubule lumen through a cotransport protein - carrying glucose or an amino acid at the same time via facilitated diffusion
4. As this happens, the concentration of glucose and amino acids within the proximal convoluted tubule wall (cell) increases, and so these substances diffuse out of the cell and into the blood capillary.
5. The movement of ions, glucose and amino acids into the convoluted tubule wall leads to a decreased water potential so water move sinto the cell by osmosis.

What is the mechanism of reabsorption?

- The movement of sodium ions and glucose into the cell is driven by the concentration gradient created by pumping sodium ions out of the cell.
- The sodium ions move into the cell by facilitated diffusion but they cotransport glucose or amino acids against their concentration gradient.
- The movement of these substances reduces the water potential of the cells so that water is drawn in from the tubule by osmosis
- As the substances move through to the blood, the water follows

What is the Loop of Henle?

- a hairpin-shaped loop of the renal tubule
- starts in the cortex and extends deep into the medulla
- forms a counter current mechanism

What is the role of the loop of Henle?

- Creates an osmotic gradient within the medullary region
- It's main function is the recovery of water and sodium chloride from the urine causing the urine to be more concentrated and causing the tissue fluid of the medulla to become very concentrated with solutes.

Explain what the loop of Henle does:

The loop of Henle acts as a countercurrent multiplier to establish a concentration gradient in the renal medulla.
The upper part of the ascending limb pumps NaCl out of the urine and into the tissue fluid, but H20 cannot follow, because this region of the tubule is impermeable to water. Continued pumping of NaCl from the thick, upper part of the ascending limb sets up a concentration gradient in the renal medulla
Increased concentration of NaCl in the tissue fluid causes the osmotic absorption of water from the descending limb, thus concentrating the tubule fluid that enters the ascending limb.
The urine entering the collecting duct is less concentrated than the tissue fluid, so as urine passes down the collecting duct it loses water to the tissue fluid and becomes more and more concentrated.
Water reabsorbed from the descending limb and the collecting duct leaves the medulla in the vasa recta.
The lower collecting duct is permeable to urea as well as water. Urea is concentrated in the urine at this point, so it diffuses into the tissue fluid. This increased osmolarity of the tissue fluid enhances the countercurrent multiplier effectiveness. Urea enters the ascending limb and is recycled.

What happens when sodium ions are actively pumped out of the upper part of the ascending limb?

Sodium ions and chloride ions actively pumped out of the upper part of the ascending limb to make medulla fluid more concentrated to create a gradient.

Sodium ions are positive and repel each other. This causes sodium ions to move down further into the medulla, meaning there are more sodium ions the further you go down the medulla. This results in an ever-decrasing water potential gradient.

Thus the solution becomes more dilute as you go up the ascending limb. This is not only because more solutes leave by active transport, but also because the top part of the ascending limb is impermeable to water so no water can leave anymore.

Explain the role of the loop of Henle in the production of urine

In the ascending limb, sodium and chloride ions are pumped out which increases the concentration of sodium and chloride ions in the interstitial fluid. As the water potential of the interstitial fluid is now lower than in the descending limb, water is lost by osmosis. As filtrate flows through the loop of Henle, at the base of the descending limb, sodium and chloride ions leave by simple diffusion. This occurs as there is a higher concentration of such ions in the limb than in the interstitial fluid, so they move down the concentration gradient. As filtrate continues to flow into the ascending limb, solute potential is low and water potential is higher, so sodium and chloride ions are pumped out by active transport into the interstitial fluid. This is known as the hairpin countercurrent multiplication system.

What is a counter-current multiplier?

A set of parallel tubes in which the contents move in opposite directions.
When 2 liquids flow in opposite directions past one another, the exchange of substances between them is greater than if they flowed int he same direction next to each other. This allows a concentration gradient to form in the interstitial fluid.

What is osmoregulation?

Osmoregulation is the control of water potential in the body.

Osmoregulation involves controlling levels of both water and salt in the body.

Why must there be a correct water balance?

The correct water balance between cells and the surrounding fluids must be maintained to prevent water entering cells and causing lysis or leaving cells and causing crenation.

How do the kidneys alter the volume of urine produced?

By altering the permeability of the collecting ducts
- if you need to conserve less water, the walls of the collecting ducts become less permeable so less water is reabsorbed and a greater volume of urine is produced
- if you need to conserve more water, the collecting duct walls are made more permeable so that more water can be reabsorbed into the blood and a smaller volume is produced

What type of feedback is osmoregulation?

negative feedback

Where is ADH produced and stored?

Produced by neurosecretory cells in the hypothalamus and stored in the posterior pituitary gland

How does osmoregulation work?

Osmoreceptors in the hypothalamus detect a decrease in blood plasma water potential.
A signal is sent along sensory neurones to the posterior pituitary gland which releases the hormone ADH into the bloodstream, which is carried to the kidney and binds to the receptor points on the walls of the collecting duct and distal convoluted tubule. Aquaporins are intrinsic protein channels which are added to the cell membranes by fusing with the membrane and allow more water to be absorbed by osmosis, which increases the water potential of the blood back towards the set point.
This information is fed back to the hypothalamus and less ADH (no ADH) is produced.

How does ADH alter the permeability of the collecting duct wall and distal convoluted tubule wall?

The cells in the walls have membrane-bound receptors for ADH.
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell.
The end result of these reactions is to cause vesicles containing aquaporins to fuse with the cell surface membrane
This makes the walls more permeable to water.
As the level of ADH in the blood rises, more water-permeable channels are inserted. This allows more water to be reabsorbed by osmosis into the blood

What do osmoreceptors do?

These are sensory receptors that detect the stimulus - they monitor the water potential of the blood.

These cells respond to the effects of osmosis. When the water potential of the blood is low, the osmoreceptor cells lose water by osmosis and shrink. This resultantly stimulates the neurosecretory cells in the hypothalamus.

What happens when neurosecretory cells are stimulated by osmoreceptors?

The neurosecretory cells produce and release ADH. When the neurosecretory cells are stimulated, they carry action potentials down their axons and cause the release of ADH by exocytosis

What happens if there is an increase in the water potential of the blood?

1. detected by osmoreceptors in hypothalamus
2. less ADH released from posterior pituitary
3. collecting duct walls less permeable
4. Less water reabsorbed into blood and more urine produced
5. Decrease in water potential of blood to achieve normal water potential of blood

What happens if there is a decrease in the water potential of the blood?

1. detected by osmoreceptors in hypothalamus
2. more ADH released from posterior pituitary
3. collecting duct walls more permeable
4. more water reabsorbed into blood and less urine produced
5. increase in water potential of blood to achieve normal water potential of blood

What happens if the kidneys fail?

If the kidneys fail, they are unable to regulate the levels of water and electrolytes in to body or to remove waste products such as urea from the blood. This eventually leads to death

- Urea, water, salts and various toxins are not excreted
- Less blood is filtered by the glomerulus
- Build up of toxins in the blood
- Electrolyte balance is disrupted as the concentration of ions is not maintained

How does kidney failure occur?

Blood loss in an accident
High blood pressure
Diabetes
Overuse of certain drugs
Certain infections

What are the main treatments for kidney failure?

Renal dialysis and kidney transplant

What is renal dialysis?

Renal dialysis is a mechanism used to artificially regulate the concentrations of solutes in the blood.
- Waste products, excess fluid and mineral ions are removed from the blood by passing it over a partially permeable dialysis membrane that allows the exchange of substances between the blood and dialysis fluid.
- Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
- Any substances that are too low in concentration diffuse int the blood from the dialysis fluid.

What are the 2 types of dialysis?

hemodialysis and peritoneal dialysis

What is haemodialysis?

uses a dialysis machine that seperates the blood to be 'cleaned' and a dialysis fluid with a selectively permeable membrane

blood leaves the patient's body from an artery and flows into the dialysis membrane. This membrane mimics the basement membrane of the bowman's capsule.

How is the loss of substances in haemodialysis controlled?

The loss of glucose and mineral ions is prevented by careful control of dialysis fluid.
The dialysis fluid contains normal plasma levels of glucose to ensure there is no net movement of glucose out of the blood.
The dialysis fluid also contains normal plasma levels of mineral ions, so any excess mineral ions in the blood move out by diffusion down a concentration gradient into the dialysis fluid, thus restoring the correct electrolyte balance of the blood.
The dialysis fluid contains no urea meaning there is a very steep concentration gradient from the blood to the fluid, and as a result, much of the urea leaves the blood.

How is haemodialysis set up?

Your blood is circulated outside your body through a machine containing special filters, via a thin, flexible tube (a catheter) inserted into a vein. The filter removes the waste products from your blood. After passing through the dialysis machine, your blood returns to your body via a second catheter.
In other words, you are connected to an artificial kidney

Explain haemodialysis

The patient requires regular treatment in a hospital or at home using a machine known as a hemodialyzer, which acts as an artificial kidney
In this dialysis machine, partially permeable dialysis membranes separate the patient's blood from the dialysis fluid (known as the dialysate)
The blood is passed through tubes of dialysis membrane, which are surrounded by dialysate
The dialysate contains substances needed in the blood (e.g glucose and sodium ions) in the right concentrations (i.e concentrations similar to a normal level in blood)
As the dialysate contains a glucose concentration equal to a normal blood sugar level, this prevents the net movement of glucose across the membrane as no concentration gradient exists
As the dialysis fluid contains a salt concentration similar to the ideal blood concentration, movement of salts across the membrane only occurs where there is an imbalance
The fluid in the machine is continually refreshed so that concentration gradients are maintained between the dialysis fluids and the blood
Importantly, the dialysate contains no urea
This causes urea to diffuse down its concentration gradient from the blood into the dialysate and is eventually disposed of
The hemodialyse is designed so that the patient's blood and the dialysate flow in opposite directions, creating a concentration gradient along the length of the dialyser component of the machine
This means that each time blood circulates through the machine, some more of the urea it contains passes into the dialysate, until almost all of it is removed
The drug heparin is added to the blood as it is an anticoagulant (blood thinner) that prevents the formation of blood clots

What is peritoneal dialysis?

Use the peritoneal membrane as a filter to filter waste products from the blood.

During treatment, a dialysate is inserted into your abdomen through the catheter in your abdomen. The dialysate fluid is poured through the tube and fills the space between the abdominal wall and organs. It is then left for 6-24 hours. During this time, toxins, waste products and excess water all move from your bloodstream into the dialysis, which is then drained out of your abdomen through the catheter. Another bag of dialysate fluid is then inserted.

What are the two types of peritoneal dialysis?

CAPD (Continuous Ambulatory Peritoneal Dialysis) - doesn't require a machine

CCPD (Continuous Cycle Peritoneal Dialysis) - overnight + requires a machine

What is a kidney transplant?

The transfer of a healthy kidney from one person into the body of a person who has little or no kidney activity.

What are 2 problems with kidney transplants?

Shortage of donors
Rejections

What are the advantageous of a kidney transplant?

- no time consuming renal dialysis
- physically fit
- improved quality of life
- improved self image
- works more efficiently than dialysis in restoring the natural functions of a kidney

What are the disadvantageous of a kidney transplant?

- need to take immunosuppressant drugs
- need major surgery
- need regular checks for signs of rejection
- side effects of immunosuppressants\= high blood pressure + susceptibility to infections