Introduction
The body is made up of various organ systems which perform various functions. One of this is the urinary system which is responsible for excretion of various metabolic wastes. An important organ in the urinary system is the kidney. In the kidney, blood undergoes ultra filtration; nutrients such as glucose are reabsorbed back while waste products such as urea and excess water form urine which is excreted. The kidney maintains electrolyte and water balance in the body. During sustained physical activity, the body looses a lot of water through sweating. This disrupts the electrolyte balance in the body and leads to dehydration. Besides reduced physical performance, dehydration can lead to hypotension and result in health complications. In this paper, the structure and functioning of the kidneys is evaluated in light to the case study of Rivka.
Background
Rivka is a 21 year old university student. She went to the beach on a hot day and played beach volleyball with other people there. However, since she had not planned on playing volleyball, Rivka had not carried energy drinks and sodas to keep her body hydrated and to maintain electrolyte balance. Soon Rivka went down with symptoms of dizziness. She had not used the washroom all day. This is an indication of a problem with her urinary system. Since she had felt dizzy after sustained physical activity with no drinks to maintain electrolyte balance and keep the body hydrated, Rivka had experienced a dehydration episode. She regained composure after taking energy drinks. Understanding the structure and functioning of the kidney can help nurses to provide better care not only to patient suffering from renal failure, but those who are dehydrated too.
Structure of the Kidney and functioning of the kidney
A human being has two kidneys found in the abdominal cavity. The kidneys are bean shaped organs which serve various functions in the body such as excretion, homeostasis, acid-base balance, and regulating blood pressure. The kidneys are supplied with blood through the renal artery and drained by the renal vein. In the kidney, the arteries divide into arterioles which supply the glomeruli. The nephron is the functional unit of the kidney. It consists of a renal corpuscle (Bowman’s capsule), the distal convoluted tubule and the loop of Henle (Porth, 2010). The glomeruli are a collection of arterioles which are partially surrounded by the Bowman’s capsule. Blood from the renal artery is under high pressure and undergoes ultra-filtration with the filtrate consisting of all blood components except the cells and the large plasma proteins. In the convoluted tubule and the loop of Henle, vital nutrient are reabsorbed leaving metabolic wastes such as urea and excess water which forms urine. Up to 180 liters of blood is filtered every day to produce two liters of urine after re-absorption (Bellomo, Kellum & Ronco, 2009).
Kidney functioning is characterized by the Glomerular filtration rate (GFR). This is a test which estimates how much blood is filtered in the kidney per minute. The Normal GFR is 90-120 mL/min/1.73m2 with older people having a lower GFR than younger people. Low GFR levels indicate chronic kidney disease and levels below 15 mL/min/1.73m2 indicate renal failure and can be fatal (Israni & Kasiske, 2007).
The kidney is responsible for long term maintenance of blood pressure. This is done through the maintenance of exracellular fluid levels and through response to the hormones angiotensin II and adolsterone which promote absorption of sodium chloride in the kidneys. Excess sodium chloride expands extracellular fluid compartments raising blood pressure (Porth, 2010). Participating in sustained physical exercises can lead to water and solute loss through sweating. If the lost water and solutes are not replenished, dehydration occurs. In the case study, Rivka had dehydration for playing volleyball for many hours in the sun without taking energy drinks or water. The Renin-angiotensin system which is responsible for maintenance of blood pressure is affected by the level of sodium chloride in the blood. Loss of sodium chloride through sweating reduces the level of renin in the blood. This in turn reduces the level of angiotensin II and adolsterone leading to contraction in the extracellular fluid compartment (Porth, 2011). This has a direct effect of lowering blood pressure leading to a physiological state called hypotension. Hypotension is the opposite of hypertension and is characterized by low blood pressure in the systemic circulation.
Rivka underwent hypotension as a result of dehydration. Hypotension can readily be inferred from the symptom of dizziness and stopping to sweat. GFR depends on blood pressure to effect ultra filtration the Bowman’s capsule. Hypotension reduces GFR rate leading to accumulation of waste products in the body. This can be life threatening as sustained hypotension and blood rich in waste products affects the functioning of key body organs such as the brain, heart and the liver. The juxtaglomerular apparatus regulates the functioning of the nephrones and is found between the renal corpuscle and the distal convoluted tubule. When a person suffers from hypotension such as Rivka did, the granulated cells in the juxtaglomerular secrete renin.
Effects of Adosterone on the distal convoluted tubule
Adosterone is an endocrine steroid hormone produced in the adrenal cortex of the adrenal gland. The action of adosterone is to increase the re-absorption of ions and water in the kidney. Adosterone affects the distal convoluted tubule in the kidneys by activating the basolateral Na+/K+ pumps, which actively absorb sodium ions back into the blood and secrete potassium ions into the kidney lumen to form urine (Arroyo et al., 2011). Since sodium chloride has a high osmotic potential, absorption of sodium ions causes absorption of water into the blood. The additional water increases blood volume and raises blood pressure. In addition, adosterone promotes the absorption of sodium ions and water from the digestive system and glands such as sweat glands and salivary glands in exchange to potassium ions.
The overall action of adolsterone is to increase blood pressure. This would be very useful to Rivka since she has developed hypotension after sustained loss of water and solutes during the volleyball game. Hypotension can lead to shock when the brain and other organs do not receive sufficient oxygen and nutrients. Therefore, Rivka needs a higher blood pressure in order to recover from this physiological state. Adolsterone promotes absorption of water and sodium ions from the digestive canal sand sweat gland. Absorption of water and sodium ions from sweat glands reduces sweating and prevents loss of water and sodium ions hence increase blood pressure. In addition, excess water is absorbed from the intestines when she takes energy drinks and this reverses her dehydration.
Specific Gravity test for Urine
The specific gravity test is conducted with a fresh urine sample to determine water balance in the body and urine concentration. According to Landry & Barazi, normal values for the urine specific gravity test range from 1.000 to 1.030 (2011). The kidney concentrates metabolic waste products to ensure that they are excreted with little loss of water and nutrients. There are several factors can lead to abnormal results which are either above or below the normal range. Rivka had an episode of dehydration. Dehydration causes an increase in the specific gravity of urine above the normal range. Therefore, if one tested Rivka’s urine, the specific gravity would be above the normal range. This indicates dehydration and is caused by highly concentrated urine. As the body struggles to reduce water loss and the effects of dehydration, a lot of water is reabsorbed in the kidney leading to a low rate of urine formation. The formed urine has a high concentration of waste products such as urea and low concentration of water. This leads to high concentration of urine hence a higher than normal urine specific gravity test result.
Conclusion
The kidneys are responsible for excretion of waste products and maintenance of blood pressure. When one participates in sustained physical activity and does not replenish water and solutes lost through sweating, dehydration can occur. A common symptom of dehydration is hypotension which is a physiological state of reduced blood pressure. Rivka underwent dehydration and as the kidney reacts to control water loss, she produces concentrated urine with high specific gravity. Taking energy drinks with solutes and water reverses dehydration and hypotension when normal kidney functioning is restored
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