# Find how much times blood is filtered in the kidney?

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The blood that circulates in our body is about 1/12 of our mass. If the kidneys filter 7.5 liter of blood a hour, then how many times does it filter in the kidney the whole blood of a person will mass 60kg?

Here's what my teacher did:

1/12*60=5 liter blood

0.55*5=2.75 liter plasma of blood.

The plasma is filtered 60 times is 24 hours. (how did she find that?)

24 hours ->60 times the plasma filters

1 hour -> x

x=2.5 times

Do you understand her explanation? What should I do next?

1/12*60=5 liter blood

no explanation required here

0.55*5=2.75 liter plasma of blood.

only the plasma is filtered in the kidney (the 45% cell content remains in the blood stream), so out of the 5 l blood, only 2.75 l need to be filtered.

The plasma is filtered 60 times is 24 hours. (how did she find that?)

the kidney filteres 7.5 l per hour so if the whole blood plasma has 2.75 l, then in one hour the whole blood is filtered 7.5/2.75=2.73 times. In one day the whole blood is filtered 2.73*24=65.5 times (the numbers are slightly rounded).

## Kidney

The kidney is a paired vital organ that removes waste products from the blood and regulates fluid and electrolyte levels within the body. Only one is necessary, but this organ’s importance means that we have two should one shut down, there is a backup. Kidneys contain numerous nephrons – miniature filtration systems that regulate salt, water, glucose, and amino acid levels in the blood plasma filtrate that eventually becomes urine. The kidney also secretes two hormones, renin and erythropoietin.

## Processes of the Kidneys

Filtration is the mass movement of water and solutes from plasma to the renal tubule that occurs in the renal corpuscle. About 20% of the plasma volume passing through the glomerulus at any given time is filtered. This means that about 180 liters of fluid are filtered by the kidneys every day. Thus, the entire plasma volume (about 3 liters) is filtered 60 times a day! Filtration is primarily driven by hydraulic pressure (blood pressure) in the capillaries of the glomerulus.

Note that the kidneys filter much more fluid than the amount of urine that is actually excreted (about 1.5 liters per day). This is essential for the kidneys to rapidly remove waste and toxins from the plasma efficiently.

Reabsorption is the movement of water and solutes from the tubule back into the plasma. Reabsorption of water and specific solutes occurs to varying degrees over the entire length of the renal tubule. Bulk reabsorption, which is not under hormonal control, occurs largely in the proximal tubule. Over 70% the filtrate is reabsorbed here. In addition, many important solutes (glucose, amino acids, bicarbonate) are actively transported out of the proximal tubule such that their concentrations are normally extremely low in the remaining fluid. Further bulk reabsorption of sodium occurs in the loop of Henle.

Regulated reabsorption, in which hormones control the rate of transport of sodium and water depending on systemic conditions, takes place in the distal tubule and collecting duct.

Even after filtration has occured, the tubules continue to secrete additional substances into the tubular fluid. This enhances the kidney's ability to eliminate certain wastes and toxins. It is also essential to regulation of plasma potassium concentrations and pH. (See Fluid and electrolyte balance).

Excretion is what goes into the urine, the end result of the above three processes. Although the original concentration of a substance in the tubule fluid may initially be close to that of plasma, subsequent reabsorption and/or secretion can dramatically alter the final concentration in the urine.

The amount of a particular substance that is excreted is determined by the formula:

The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus it stays in the renal cortex. The second part is called the loop of Henle, or nephritic loop, because it forms a loop (with descending and ascending limbs) that goes through the renal medulla. The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex. The DCT, which is the last part of the nephron, connects and empties its contents into collecting ducts that line the medullary pyramids. The collecting ducts amass contents from multiple nephrons and fuse together as they enter the papillae of the renal medulla.

The capillary network that originates from the renal arteries supplies the nephron with blood that needs to be filtered. The branch that enters the glomerulus is called the afferent arteriole. The branch that exits the glomerulus is called the efferent arteriole. Within the glomerulus, the network of capillaries is called the glomerular capillary bed. Once the efferent arteriole exits the glomerulus, it forms the peritubular capillary network, which surrounds and interacts with parts of the renal tubule. In cortical nephrons, the peritubular capillary network surrounds the PCT and DCT. In juxtamedullary nephrons, the peritubular capillary network forms a network around the loop of Henle and is called the vasa recta.

## Kidney Disease (Nephropathy)

Kidney disease generally occurs when the nephrons (tiny blood capillaries inside the kidneys), become damaged, causing them to lose their filtering capacity.

This loss of function can cause useful protein, such as albumin – the main protein in the blood to leak out of the kidneys and into the urinary system, as well as the build up of wastes in the blood. This serious condition is also referred to as nephropathy , which means disease or damage of a kidney.

Although the exact cause is unknown, poor control of blood sugar and high blood pressure ( hypertension ) are known to increase the risk of kidney damage.

In people with diabetes, nephron damage (diabetic kidney disease) is caused by excess glucose in the blood, which can act like a poiso, while elevated blood pressure can also damage the small blood vessels.

## A safer, effective treatment for autoimmune glomerulonephritis

Kidneys are the body’s in-built, highly efficient “detox” system. The kidneys filter and clean the blood, expelling waste from the body in the form of urine. Within each kidney are more than a million tiny filtration units, called glomeruli. Each individual glomerulus consists of a tight knot of tiny capillaries, in which blood is filtered at high pressure.

Glomerulonephritis is a form of kidney disease that causes damage to the glomeruli, hindering their ability to carry out their essential functions. This damage takes the form of vasculitis, which causes changes in the walls of blood vessels, potentially hindering blood flow. When this happens, the kidneys cannot effectively remove waste products (such as urea) and excess fluids from the blood. While some types of glomerulonephritis do not necessarily cause serious symptoms, some forms of the condition can be devastating and even life-threatening, damaging the kidney to the point where dialysis or even a transplant are necessary.

Autoimmune anti-myeloperoxidase glomerulonephritis.

Glomerulonephritis is often an autoimmune condition in other words, it is caused by the body’s immune system attacking its own tissues. In autoimmune anti-myeloperoxidase glomerulonephritis (anti-MPO GN), the immune system attacks an enzyme called myeloperoxidase. This enzyme is largely found in a particular type of white blood cells, which are an important part of the body’s immune defences. Normally, these white blood cells destroy invasive pathogens such as bacteria. In anti-MPO GN, however, the white blood cells appear to target the glomeruli instead. Anti-MPO GN is a life-threatening condition that causes severe inflammation of the small blood vessels in the kidneys.

Current treatment options for anti-MPO GN are limited. The medications that are available are only partially effective, and are associated with many adverse effects in particular, as the treatments cause broad suppression of the immune system, the patient has a high risk of contracting a serious infection. Safer, more specific treatments for anti-MPO GN are needed. Ideally, these treatments should supress only the anti-MPO immune response, and thus protect the kidneys from damage.

Exploring tolerogenic dendritic cells
Dr Dragana Odobasic of Monash University, Australia, leads research into safer treatments for autoimmune kidney disease. In a recent study, Dr Odobasic and her colleagues investigated the potential of a particular group of cells, called tolerogenic dendritic cells, in developing new treatments for anti-MPO GN.

Glomerulonephritis is a form of kidney disease that causes damage to the glomeruli, hindering their ability to carry out their essential functions. Designua/Shutterstock.com

Dendritic cells play an important role in adaptive immunity – immunity that arises after exposure to a pathogen (or a vaccination). Activated, or mature, dendritic cells are also known to be a factor in some types of autoimmune disease. However, immature dendritic cells can help to prevent over-activity of the immune system, through inhibiting a type of immune cell called T-cells. These immature cells are termed tolerogenic dendritic cells, because they promote “tolerance” (unresponsiveness) in the immune system.

Tolerogenic dendritic cells promote immunosuppression, and could therefore fulfil the need for a specific, targeted treatment for anti-MPO GN.

Tolerogenic dendritic cells promote immunosuppression in a specific manner, and could therefore fulfil the need for a more targeted treatment for anti-MPO GN. These cells have already been used in phase 1 trials (which test the safety and toxicity of a drug) in patients with other autoimmune diseases. The results have been promising. Dr Odobasic and her colleagues suspected that the treatment could be particularly successful in anti-MPO GN, as the aberrant immune response targets a specific, known protein (myeloperoxidase). Also, in many patients with acute anti-MPO GN, damage to the kidneys can be at least partially reversed with effective treatment, reducing the need for a kidney transplant or dialysis.

In their recent study, Dr Odobasic and her team investigated whether tolerogenic dendritic cells can effectively suppress MPO-specific autoimmunity and thereby limit the associated kidney damage – and, if so, exactly how this occurs.

In anti-MPO GN the white blood cells appear to target the glomeruli.

Mouse model sheds light on autoimmunity
To understand more about the disease pathway of anti-MPO GN, Dr Odobasic and her team previously developed a mouse model that closely resembles the condition in humans. In this study, the team first created suitable tolerogenic dendritic cells by culturing mouse bone marrow cells with a range of carefully-selected substances. These included an inhibitor of the protein complex NFκB, which plays a major role in the pathogen-fighting and proinflammatory abilities of dendritic cells. Importantly, the dendritic cells were also treated with MPO so they can present it and therefore turn off MPO-specific T cells which cause anti-MPO GN. Through this process, the team successfully created tolerogenic dendritic cells that are able to specifically turn off only autoimmunity against myeloperoxidase.

Next, the team induced anti-MPO GN disease in a number of mice. These mice were then treated with the tolerogenic dendritic cells. As the team had hoped, the results showed that injecting tolerogenic dendritic cells can successfully, and precisely, “switch off” anti-MPO autoimmunity, without affecting the immune response to other proteins. Specifically, the researchers discovered that the dendritic cells suppressed the activity of several types of injurious white blood cells, including CD4 T cells, CD8 T cells and B-cells. In this way, the dendritic cells prevented the damage to blood vessels that is characteristic of glomerulonephritis.

Generating and using autologous myeloperoxidase (MPO)-presenting tolerogenic dendritic cells (DCs) as a therapy in anti-MPO vasculitis patients.

The team also discovered that the tolerogenic dendritic cells were able to suppress anti-MPO autoimmunity by inducing a type of immune cell called regulatory T-cells. Regulatory T cells, as the name suggests, regulate the activity of the immune system crucially, these cells maintain tolerance of self-antigens (proteins expressed by the body’s own cells) and help to prevent auto-immune disease.

Injecting MPO-presenting tolerogenic dendritic cells can successfully and precisely “switch off” anti-MPO autoimmunity.

Dr Odobasic suspects that, although the tolerogenic dendritic cells only survive in the recipient for a few weeks, their effects may last for much longer. In addition, administering multiple doses of tolerogenic dendritic cells should create stronger, longer-lasting effects, enhancing the treatment’s ability to protect the kidneys.

Generation of myeloperoxidase (MPO)-presenting tolerogenic dendritic cells (DCs) for use in the murine model of anti-MPO glomerulonephritis (GN):
1. Isolate bone marrow from mice.
2. Culture mouse bone marrow cells for 8 days
(in the presence of GM-CSF & NFκB inhibitor).
3. Enrich DCs by anti-CD11c microbeads
(95% CD11c+ cells).
4. Pulse DCs with recombinant
mouse MPO (2 hours).

A targeted treatment for autoimmune disease
Dr Odobasic’s work has demonstrated, for the first time, that injecting tolerogenic dendritic cells can specifically “switch off” anti-MPO autoimmunity and protect the glomeruli from vasculitis. In addition, other researchers have used tolerogenic dendritic cells in studies of different autoimmune diseases, with similarly promising results.

Together, these results strongly suggest that tolerogenic dendritic cells could be a new, effective and safe treatment for anti-MPO GN. Such a treatment would be a huge benefit for anti-MPO GN patients, improving their quality of life and allowing them to avoid the dangerous side effects that accompany many of the current, non-specific, treatments. In fact, these cells could potentially offer an effective cure for anti-MPO GN, by preventing damage to the tiny blood vessels of the glomeruli.

In future, Dr Odobasic and her colleagues plan to further their research by collecting blood cells from patients with vasculitis. These blood cells would then be purified and treated with an NFκB inhibitor, and incubated with human myeloperoxidase. The cells would then be injected back into the same patient, eliminating the risk of rejection. Hopefully, this will allow the researchers to demonstrate that a patient’s own tolerogenic dendritic cells have the ability to switch off their autoimmunity to MPO. Dr Odobasic also plans to test other types of tolerogenic dendritic cells in anti-MPO GN because the effectiveness and precise mechanism of immunosuppression varies between different types of tolerogenic dendritic cells. This will allow the team to identify the best dendritic cell candidate to be tested clinically.

Ultimately, the researchers hope that positive results from this research will allow them to lead a world-first clinical trial of tolerogenic dendritic cells in treating anti-MPO GN from their base at Monash University, Australia.

### Personal Response

Do you plan to explore the use of tolerogenic dendritic cells in any other conditions?

Our published results in anti-MPO GN have formed a strong basis for testing tolerogenic DCs as a therapy for other serious autoimmune kidney diseases such as Goodpasture’s syndrome and anti-Proteinase3 vasculitis. For those conditions, the current therapies consist of the same toxic, non-specific immunosuppressants and the target autoantigens are also known. So, we plan to test tolerogenic dendritic cells in those diseases, too.

## Biology AQA Homeostasis question HELP

The efficiency with which the kidneys filter blood can be measured by the rate at which they remove a substance called creatinine from the blood. The rate at which they filter the blood is called the glomerular filtration rate (GFR).
In 24 hours, a person excreted 1660 mg of creatinine in his urine. The concentration of creatinine in the blood entering his kidney was constant at 0.01 mg cm-3
calculate the GFR in cm3 minute-1.

can someone tell me how to get to this answer and tell me the equation for rate?
It is a 1 marker
Thanks

### Not what you're looking for? Try&hellip

(Original post by kathy9)
The efficiency with which the kidneys filter blood can be measured by the rate at which they remove a substance called creatinine from the blood. The rate at which they filter the blood is called the glomerular filtration rate (GFR).
In 24 hours, a person excreted 1660 mg of creatinine in his urine. The concentration of creatinine in the blood entering his kidney was constant at 0.01 mg cm-3
calculate the GFR in cm3 minute-1.

can someone tell me how to get to this answer and tell me the equation for rate?
It is a 1 marker
Thanks

As the unit of measurement tells you, the GFR = amount of blood filtered in cm3 /time in minutes

The challenge is how to work out how much blood needed to be filtered over 24 hours in order to excrete 1660mg of creatinine.

Start by turning 24 hours into minutes (that's the unit of measurement you need)

So the person excreted 1660mg creatinine in 1440 minutes = 1660 /1440 = 1.1527mg creatine per minute

Now all you need to find is what volume of blood needed to be filtered through the glomerulus over this time to get this amount of creatinine filtered out. You aren't given the volume directly, but you are given the concentration of creatinine per cm3 i.e for every cm3 filtered, you will get 0.01mg creatinine.

So you just divide the amount of creatinine removed (1.1527 mg per minute) by how much is in each cm3 of blood filtered (0.01 mg/cm3)

## Revision:Gcse biology - the kidneys

Urea is produced in the liver where proteins (which can&rsquot be stored) are broken down into fats and carbohydrates, with the waste product as urea it is filtered out of the blood by the kidneys, because urea is poisonous.

Salts are eaten, and while the body needs some salts, a salty meal (for example) however, will have far too much salt, so kidneys will filter out the excess salts.

Water which is taken in can be lost from the body in three ways in the breath, in the sweat and in the urine. Because the water lost from breath is constant, the water content has to be balanced between the amount you sweat and the amount dumped from the kidneys. Therefore on a cold day, if you don&rsquot sweat then you will produce more urine which will be pale and dilute, while on a hot day if you sweat a lot, you will produce less, but it will be concentrated. The name of this process is osmo-regulation and is an example of homeostasis

The kidneys are made up of the medulla and the cortex. The cortex is the lighter exterior, while the medulla is an area made up of feathery like structures closer to the centre which are attached to the ureter.

## Urinary System

The urinary system in human includes kidneys, ureter, urinary bladder and urethra that collectively constitute the urine excretion. Kidney is a major organ that assist the separation of nitrogenous wastes to the urinary bladder through a long tube called ureter. Let us look into the external structure of our urinary system.

### The kidneys

There are two kidneys in a human body, whose average weight is 120-170 grams. Its structure appears bean-shaped that is encircled by a layer of fat and connective tissue. A vertical section of kidney shows a renal capsule, cortex, medulla, pelvis and hilum.

• Renal capsule: It is a thin and tough outer covering of the kidneys that is composed of dense connective tissues.
• Renal cortex: It is found interior to the renal capsule. Renal cortex includes cluster of blood capillaries and a glomerulus.
• Renal medulla: It is found interior to the renal cortex. The renal medulla possess a radial appearance and comprises nephron tubule, vasa recta and collecting duct. It can be partitioned into an outer and inner medulla. An outer medulla comprises renal columns, which also refers as “column of Bertini”. Renal pyramids appear as cone shaped structures that constitute an inner medulla, as these extend out to form renal papillae.
• Renal pelvis: It resembles a funnel-shape that comprises around 8-18 minor and 2-3 major projections or calyces. Renal pelvis is inner to the hilum.

Ureters: It appears as two long slender tubes that originates from the region of renal pelvis and goes downwards to the urinary bladder.

Urinary Bladder: It is located in the lower part of abdominal cavity, and connected with the ureters and urethra. Urinary bladder acts like a hollow and muscular organ that comprises an elastic wall, which can expand or contract accordingly.

Urethra: The urine is expelled out from the urinary bladder out of the body by urethra.

### Nephron as a Excretory Unit

Nephrons are the functional units of the kidneys, which separates urine from the blood. In kidney, nephrons are generally categorized into cortical and juxtamedullary nephrons.

1. Cortical nephrons: It constitutes about 80-85% of nephrons. The renal corpuscles lie within outer renal cortex. Here, the loop of Henle runs very little to the medulla. It maintains the ionic balance of blood.
2. Juxtamedullary nephrons: In this the renal corpuscles lie close between the junction of renal cortex and medulla. Unlike cortical nephrons, the loop of Henle run deep into the medulla. It primarily concentrates the urine.

Malpighian or renal corpuscle and the coiled uriniferous tubules are the structural elements of nephron.

#### Malphigian Corpuscle

It comprises two components, namely glomerulus and Bowman’s capsule. A glomerulus is the capillary network of afferent arterioles, which is surrounded by the double layered epithelial cup called Bowman’s capsule. A glomerulus is composed of three layers:

• Visceral layer of epithelial cells (podocytes) and basement membrane: The epithelial cells link with the basement membrane via pedicels, and that’s why also called as “podocytes”. Over the basement membrane, the pedicles are arranged in a sequence leaving a narrow space in between that are called as “filtration slits”. A basement membrane lies within the visceral and parietal layer. It is a thin, middle layer that retains the plasma proteins from being filtered out.
• Parietal layer of squamous endothelial cells: It possesses large pores that permits the passage of solutes, plasma proteins etc.

A visceral layer participates in the urine filtration, and passes the filtrate to the capsular space of parietal layer via the capillaries.

#### Coiled Uriniferous Tubules

It consists of proximal, nephron and distal tubule that performs specific tasks inside the kidney. The proximal tubule is a 15 mm long convoluted tube that originates from the capsular space of parietal layer, and extends downwards to the medulla to form loop of Henle.

Henle’s loop or nephron tubule originates from the proximal tubule descends into a thin limb (2-14 mm long) and goes upward forming a thick limb (12 mm long). The ascending loop reaches glomerulus and passes close to its afferent and efferent arteriole forming macula densa (a part of juxtaglomerular apparatus).

Distal convoluted tubule originates from the macula densa cells of the juxtaglomerular apparatus that measures 5 mm length. It joins to the collecting duct. The filtrate from collecting tubule reaches renal pelvis, from where the urine discharge into the urinary bladder through a pair of ureter.

Everybody knows that some organs in the human body are necessary for survival: you need your brain, your heart, your lungs, your kidneys.

KIDNEYS? Absolutely. Even though you won't find a Valentine's Day card with a kidney on the cover, the kidneys are every bit as important as the heart. You need at least one kidney to live!

### What Are Kidneys?

Kidneys normally come in pairs. If you've ever seen a kidney bean, then you have a pretty good idea what the kidneys look like. Each kidney is about 5 inches (about 13 centimeters) long and about 3 inches (about 8 centimeters) wide &mdash about the size of a computer mouse.

### What Do Kidneys Do?

One of the main jobs of the kidneys is to filter the waste out of the blood. How does the waste get in your blood? Well, your blood delivers nutrients to your body. Chemical reactions in the cells of your body break down the nutrients. Some of the waste is the result of these chemical reactions. Some is just stuff your body doesn't need because it already has enough. The waste has to go somewhere this is where the kidneys come in.

First, blood is carried into the kidneys by the renal artery (anything in the body related to the kidneys is called "renal"). The average person has 1 to 1½ gallons of blood circulating through his or her body. The kidneys filter that blood about 40 times a day! More than 1 million tiny filters inside the kidneys remove the waste. These filters, called nephrons (say: NEH-fronz), are so small you can see them only with a high-powered microscope.

### The Path of Pee

The waste that is collected combines with water (which is also filtered out of the kidneys) to make urine (pee). As each kidney makes urine, the urine slides down a long tube called the ureter (say: yu-REE-ter) and collects in the bladder, a storage sac that holds the pee.

When the bladder is about halfway full, your body tells you to go to the bathroom. When you pee, the urine goes from the bladder down another tube called the urethra (say: yu-REE-thruh) and out of your body.

The kidneys, the bladder, and their tubes are called the urinary system. Here's a list of all of the parts of the urinary system:

• the kidneys: filters that take the waste out of the blood and make pee
• the ureters: tubes that carry the urine from each kidney to the bladder
• the bladder: a sac that collects the pee
• the urethra: a tube that carries the pee from the bladder out of the body

### Keeping a Balance

The kidneys also balance the volume of fluids and minerals in the body. This balance in the body is called homeostasis (say: hoh-mee-oh-STAY-sus).

If you put all of the water that you take in on one side of a scale and all of the water your body gets rid of on the other side of a scale, the sides of the scale would be balanced. Your body gets water when you drink it or other liquids. You also get water from some foods, like fruits and vegetables.

Water leaves your body in several ways. It comes out of your skin when you sweat, out of your mouth when you breathe, and out of your urethra in urine when you go to the bathroom. There is also water in your bowel movements (poop).

When you feel thirsty, your brain is telling you to get more fluids to keep your body as balanced as possible. If you don't have enough fluids in your body, the brain communicates with the kidneys by sending out a hormone that tells the kidneys to hold on to some fluids. When you drink more, this hormone level goes down, and the kidneys will let go of more fluids.

You might notice that sometimes your pee is darker in color than other times. Remember, pee is made up of water plus the waste that is filtered out of the blood. If you don't take in a lot of fluids or if you're exercising and sweating a lot, your pee has less water in it and it looks darker. If you're drinking lots of fluids, the extra fluid comes out in your pee, and it will be lighter.

### What Else Do Kidneys Do?

Kidneys are always busy. Besides filtering the blood and balancing fluids every second during the day, the kidneys constantly react to hormones that the brain sends them. Kidneys even make some of their own hormones. For example, the kidneys produce a hormone that tells the body to make red blood cells.

Now you know what the kidneys do and how important they are. Maybe next Valentine's Day, instead of the same old heart, you can give your parents a special card featuring the kidneys!

## Glossary

glomerular filtration rate (GFR): rate of renal filtration

inulin: plant polysaccharide injected to determine GFR is neither secreted nor absorbed by the kidney, so its appearance in the urine is directly proportional to its filtration rate

net filtration pressure (NFP): pressure of fluid across the glomerulus calculated by taking the hydrostatic pressure of the capillary and subtracting the colloid osmotic pressure of the blood and the hydrostatic pressure of Bowman&rsquos capsule

systemic edema: increased fluid retention in the interstitial spaces and cells of the body can be seen as swelling over large areas of the body, particularly the lower extremities

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