Chapter Summary:
In this chapter, we learned all about urinary function. This chapter detailed how the kidneys process filtrate and filters out waste products and creates urine. This chapter also detailed the electrolytes that must be maintained in order to maintain proper bodily function.
Structure of the Urinary System:The urinary system consists of the kidneys, the ureters, the urinary bladder and the urethra. Blood is circulated into the kidneys where urine is created and waste products are removed. The urine then travels down through the ureters into the urinary bladder and out the urethra. Within the kidneys are micro structures called nephrons. It is within the nephrons where the filtration all takes place.
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Micrutrition is also known as urination. This process is controlled within the urinary system. As the bladder fills, sensory receptors are triggered and a message is sent to close the external urethral sphincter preventing premature urinary release. The bladder will reach a point where it is sufficiently stretched and this will evoke a voiding reflex. The voiding reflex will stimulate the detrusor muscle which is the muscle that surrounds the bladder producing contractions to force urine out of the bladder. A person has voluntary control over the external urethral sphincter. When a person decides that it is time to urinate, the external urinary sphincter will be relaxed and voiding will occur.

Polycystic Kidney Disorder:
PKD is an inherited kidney disorder that is passed down from parent to child. PKD is a disorder that is characterized by multiple cysts on the kidneys causing them to become very large in size. These cysts form clusters and can impair kidney function. The disorder also causes the overproduction of erythropoietin which stimulates red blood cell production. A person with PKD will often have too many blood cells in their body which can lead to high blood pressure, brain aneurysms and cysts of the liver and pancreas. Symptoms of PKD include flank pain on one or both sides, blood in the urine, abdominal pain and increased urine at night. Below is a picture of two kidneys that were removed from a person with PKD. Each weighed approximately 16-18 pounds.

Application to Nursing:
Nurses must be aware of changes in a patients urinary status.This includes an increase or decrease in urine output, urinary retention, or dysuria. Each of these can signify problems that a physician needs to be made aware of. One thing that if often checked on patients is their creatinine clearance. The creatinine clearanceis a measure of how well the kidneys are functioning. The higher the creatinine clearance is, the better the kidneys are functioning. The lower the creatinine clearance is, the worse the kidneys are functioning. This is because the creatinine clearence is a measure of the rate at which the creatinine is flushed from the kidneys. If a patient is going to have a procedure done that requires any type of dye (say a contrast CT scan), the creatinine level of the blood and the creatinine clearance will be checked. This is checked because it needs to be determined before any test is done if the patient will be able to properly flush out the dye from their system. Creatinine is a product that is produced by the kidneys and in normal functioning kidneys, creatinine levels should remain constant and relatively low. By knowing how well a patient's kidney are functioning ahead of time, the nurse is able to determine if a patient should have a test done or not if it includes contrast dye.

Essential Question:

During filtration, the fluid that is being filtered passes through 3 filtration layers. These filtration layers are the capillary fenestrate, the glomular basement membrane and the slit diaphragm. The filtrate then enters the glomerular capsule where the filtrate is filtered further. Protein molecules will usually not get beyond the slit membrane. If they do, then the urine will show that there is protein in it, resulting in proteinuria. The protein that gets stuck in the slit membrane is usually reabsorbed into the blood stream by a process of receptor-mediated endocytosis. The kidneys have about 180 liters of filtrate that runs through them each day. About 85% of this amount is reabsorbed back into the blood stream. Osmosis facilitates the ability of this filtrate to be reabsorbed back into the blood stream in a constant flow. In order for reabsorbtion to occur, sodium molecules must be released into the blood. The sodium is needed to create a concentration gradient with the filtrate and the plasma to facilitate osmosis. The filtrate and the plasma are isomotic without the sodium, osmosis will not occur.When secretion occurs, waste products are secreted into the urine and the body gets rid of them through urination. Alcohol is a toxin that is filtered out of the blood stream via the kidneys and the secreted into the urine and voided out. Excretion is the equivalent of filtration-reabsorbtion + secretion. Excretion is the total discharging of waste products from the blood.

The electrolytes sodium, potassium, phosphate, bicarbonate and chloride are essential to maintain body functions. Potassium is essential for proper cardiac function. Too little potassium can cause problems such as congestive heart failure, fatigue and mood changes. A serious complication of potassium deficiency is cardiac arrhythmia. Patients who are on drugs like diuretics must have their potassium levels watched to ensure that a potassium deficiency does not occur. High potassium levels are usually not an issue for people who have normally functioning kidneys and who are not on potassium supplement therapy. The kidneys ca secret out any excess potassium that the body may be carrying. In people with decreased kidney function excess potassium can pose a major threat to their system. Cardiac arrhythmia is the most serious complication that can arise from excessive potassium levels. Bicarbonate is another important electrolyte that must be present in the body. Bicarbonate is essential for keeping the blood at a safe pH level. If there is not enough bicarbonate in the bloodstream, the blood could become too acidic. Bicarbonate also keeps the blood from becoming too basic.