• Joanna Cartwright

(http://purchon.com/biology/?page_id=140)

The kidneys are organs that filter blood, removing excess waste, regulate blood pressure and secrete vital hormones into our bodies. They are a complex filtration system, made up of various sections. Kidneys are bean shaped organs that sit behind our digestive system, under the ribs and are approximately 12cm long and 7cm wide. Each kidney is made up of 3 regions. The renal cortex is the outer layer of the kidney, the cortex extends down between the pyramids of the kidney to form the renal columns which separate the pyramids. Blood enters the kidney via the renal artery and is filtered in the cortex by glomeruli. The majority of plasma leaked into the Bowman’s capsules will be re-absorbed back into the body via the medulla. The filtered clean blood leaves the kidney via the renal vein. The renal medulla is the middle section of the kidney, this forms the renal pyramids, triangle shaped sections that point towards the renal pelvis and are made up of millions of henle that control the amount of salt and water within the urine. The pyramids produce the urine and this passes through into the renal papilla where the minor calix collects the urine. The final region is the renal pelvis, this is where the ureter is attached to the kidney, transporting urine to the bladder. The edges of the renal pelvis closest to the pyramids are cup shaped to collect the urine, these are called calyces. Urine that is produced passes through the papilla, then the minor calyx, before passing through the major calix. The major calyx is made up of a number of minor calyces to form a funnel shaped cavity. The urine passes through the major calyx then out through the ureter to the bladder.

Anatomy of the urinary system (2:1)

(http://www.innerbody.com/image/urinov.html) The urinary system is made up of 2 kidneys, 2 ureters, the bladder and the urethra. The purpose of the urinary system is to filter blood to remove waste from the body, regulate blood pressure, secrete vital hormones and balance PH levels, in turn excrete the waste products from the body.

• The kidneys – Each person has 2 kidneys although a human can function perfectly well with just 1 healthy kidney. The kidneys are organs that filter blood pumped into them by the heart under high pressure. The blood is filtered within a complex system and clean blood re-enters the body. The kidneys produce urine to excrete the bodies waste products. The kidneys also regulate blood pressure by the production and release of renin and produces erythropoietin, a hormone that stimulates the production of red blood cells.

• The ureters – The ureters are the muscular tubes that transport the urine from the kidneys to the bladder. The ureters are approximately 10 inches long and are placed on the left and right side of the body, parallel to the vertebrae column. The right side ureter is slightly shorter than the left due to the left kidney being slightly higher within the body. The urine is carried from the kidney to the bladder by muscular waves that occur within the ureter 5 times a minute. The ureters enter the bladder and are sealed by the ureterovesical valves that prevent the urine from going back to the kidneys.

• The bladder – The bladder is the part of the urinary system that stores the collected urine before urination occurs. The bladder is like a stretchy oval shaped bag that sits within the pelvis. An adult bladder can store upto 600 mls of urine. The bladder has 3 openings, 2 of which are where the ureters enter and 1 where the urethra leaves the bladder. Once the bladder is full nerves cause the bladder to contract and the internal sphincter to involuntarily relax, giving the sensation that the person needs to urinate. To urinate the person must voluntarily relax the external sphincter, this is learned during toilet training in early years.

• The urethra – The urethra is the tube that carries the urine to exit the body. The urethra is different in females than in males. In females the urethra is approximately 2 inches long and the external opening is anterior to the vaginal opening. Within males the urethra is approximately 6-8 inches with the external opening at the tip of the penis. The external sphincter must be relaxed before urination can occur, this process is called the micturition reflex.

Renal tubular system (2:3)

The kidneys tubular system is the main filtration system of the kidneys. Blood enters the kidneys via the renal artery and is first filtered and passed through the thousands of nephrons in the outer cortex. At the start of the nephron is the renal copsucle, made up of the glomerulus (filters blood) and the Bowman’s capsule (collects filtered blood). The majority of ultrafiltration is reabsorbed when it enters the proximal convoluted tubule which is the first duct of the renal tubular system. The next duct in the tubule is the loop of henle that is found in the medulla. The loop of henle is made up of 3 sections Firstly is the proximal part which is extremely permeable to water and reabsorbs any left from previous filtration. Next is the thin part, then the thick part, both of these sections reabsorb ions, but do not allow water through. The next part of the tubule is the distal convoluted tuble which concentrates of secretion rather than re-absorption. The product left after reabsorption has occurred is urine.

The role of the kidney in the balance of water, salt and pH. (1:2)

The kidneys balance the water within our blood plasma by reabsorbing as much or as little as we need. If the bodies water level is low then the kidneys will reabsorb more water, making urine more concentrate, high levels of water will make the urine weaker. The kidneys balance the body’s sodium level in a similar way as water. When salty foods are eaten the sodium is absorbed into the blood, once this blood plasma reaches the kidneys they reabsorb as much or as little sodium that is needed, the excess is secreted into the urine. The body must maintain a neutral pH level to function healthily and prevent infection. Kidneys balance the body’s pH level by removing excess hydrogen ions that cause the blood to become too acidic and disrupt the bloods pH level.

How has medical technology contributed towards kidney replacement? (2:4)

When a patient has chronic renal failure this means the kidneys no longer function correctly and the patient will ultimately need a kidney transplant or a form of dialysis. Dialysis is a method of doing the kidneys job via technology. A dialysis machine will filter the blood and return the clean blood back into the body and remove the waste. The most common form of dialysis is haemodialysis. During haemodialysis the patient is connected to the dialysis machine and the blood is filtered externally through the filtration system. This form of dialysis is performed 3 or 4 times a week. Peritoneal dialysis is a form of dialysis where a catheter is attached into the patient’s abdomen allowing the abdominal cavity to be filled with a cleansing liquid called dialysate. The peritoneal membrane will filter the excess waste into the dialysate which is then drained from the cavity. This process takes a minimum of 2 hours and is repeated through the day. A machine called a cycler can be used throughout the night to exchange the waste and the dialysate.

Homeostasis systems. (1:1)

Homeostatis is the function that enables the body to keep its internal environment in perfect balance and react to external factors that may alter this balance. Initially the body’s receptors will acknowledge the external change that is altering the balance. This information is sent to the control centre where the information is processed and the decision made to rectify the changes. The control centre will then send instructions to the effectors that create the change to rectify the body’s balance. To undergo homeostatis and rebalance the body must take positive or negative feedback. Positive feedback is when the body increases a function that is already present. Negative feedback is when the body stops a function to rebalance. The main organs concerned with homeostasis are kidneys, lungs, skin and liver.

Sodium and potassium. (1:3)

The kidneys play a vital role in controlling the sodium and potassium levels within our blood. When sodium levels become high it is called hyponatremia. (http://www.merckmanuals.com/home/hormonal_and_metabolic_disorders/electrolyte_balance/overview_of_sodium.html)When sodium levels heighten then increased osmosis occurs within the loop of henle and water levels within red blood cells increase. The increase of water within the plasma increases the blood volume resulting in high blood pressure. When sodium levels are dropping too low the body sends triggers to rectify the situation therefore increasing the blood volume to its correct level. The drop in sodium can cause the adrenal glands to secrete aldosterone which means the kidneys retain sodium, therefore producing less urine and increasing the blood volume. Antidiuretic hormone is released by the pituitary gland which causes the kidneys to reserve fluids and increase blood volume. Potassium is vital for healthy cell, nerve and muscle function. (http://www.merckmanuals.com/home/hormonal_and_metabolic_disorders/electrolyte_balance/overview_of_potassium.html) The kidneys regulate the body’s potassium levels by secreting excess potassium through urine. When the adrenal gland secretes aldosterone not only does it increase sodium absorption but it also increases the excretion of potassium. Potassium and sodium work together to ensure the body’s blood volume and cells stay healthy and balanced.

(3:1) (http://www.patient.co.uk/doctor/urine-dipstick-analysis)

Diabetic urine levels (3:1)

A urine sample taken from a diabetic patient would usually present high glucose levels. Normal urine glucose levels are 0.01-0.03g/100ml of urine, an untreated diabetic patient would present levels above this. Another indication of diabetes can be the presence of ketones in the urine, which would not appear in healthy urine. The presence of ketones in diabetic urine more commonly occur with type 1 diabetes. The presence of ketones can lead to ketoacidosis, the presence of high levels of ketones which then become toxic. Protein levels may be high in diabetic urine in comparison to normal urine. High protein levels are called microalbuminuria. Microalbuminuria is caused by albumin leaking into the urine of a diabetic patient. The urines pH level can be low in a diabetic patient. Normal urine pH levels are between 4.5 – 8, anything below 4.5 is low and due to the urine being acidic.

Bibliography

Gondar design biology (n.d.) The kidney, http://purchon.com/biology/?page_id=140, accessed 15/3/15

Innerbody (n.d.), urinary system, http://www.innerbody.com/image/urinov.html, accessed 15/3/15

Merck manuals (July 2013), overview of sodium, http://www.merckmanuals.com/home/hormonal_and_metabolic_disorders/electrolyte_balance/overview_of_sodium.html, accessed 16/3/2015

Merck manuals (July 2013), overview of sodium, http://www.merckmanuals.com/home/hormonal_and_metabolic_disorders/electrolyte_balance/overview_of_potassium.html, accessed 16/3/2015

Patient.co.uk (n.d.) urine dipstick analysis, http://www.patient.co.uk/doctor/urine-dipstick-analysis, accessed 16/3/15