Renal System, Differences between Peritoneal and Hemodialysis - Essay Example

The renal system represents the body’s plumbing system as it eliminates wastes and helps secure homeostasis. Its primary functioning parts include the nephrons which help manage the filtration system of the body. The kidneys are also part of the endocrine system and assists in the management of blood pressure. The two types of dialysis include the peritoneal and the hemodialysis. The peritoneal dialysis uses the peritoneal cavity in the filtration process whereas in hemodialysis, the filtration process occurs through the dialysis machine. Both methods are beneficial for patients and depending on recommendations of medical practitioners, the appropriate method of dialysis can be used for the patient. Renal System Introduction The renal system is basically the body’s plumbing system. It eliminates waste from the blood and helps maintain homeostasis, enabling the normal functioning of the organs and the body in general. This paper will discuss the different functions of the kidney. It will also describe the anatomy of the kidney, specifically the nephron. A discussion on how the kidney manages the excretion of the hypertonic solute load will also be established. The different types of dialysis treatment would also be presented, including the similarities and differences in their working. The functions of the kidney replaced by dialysis will also be discussed in this paper. This paper is being carried out in order to secure a thorough understanding of the renal system and how it effectively assists in securing efficient bodily functions. Body The kidney is the primary organ which assists in ensuring the body’s homeostasis, including its acid-base balance (O’Callaghan, 2009). The kidney also regulates blood pressure, and it helps balance the electrolyte concentration in the body (O’Callaghan, 2009). The kidney helps secure these functions with the assistance of other organs, including the endocrine system. Endocrine hormones like the renin, angiotensin II as well as the atrial natriureptic peptide, helps the kidney manage homeostasis (Field, et.al., 2010). Most of the kidney functions revolve around filtration and secretion processes which take place in the nephron. The kidneys also excrete the body’s waste products, including urea and uric acid (Field, et.al., 2010). Urine is also a by-product of the metabolism process which happens in the renal system. Aside from filtration and secretion processes, the kidney is also tasked with acid-base homeostasis (Desmukh and Wong, 2009). The kidneys and the lungs are the organs primarily involved in maintaining the body’s homeostasis. Such homeostasis is detected through stable pH values (Desmukh and Wong, 2009). The renal system is also very much involved in blood pressure regulation. The regulation of the pressure of the blood through the arterial walls is one of the main functions of the kidney (Dusso and Tokumoto, 2011). This process is accomplished through the renin-angiotensin system where any change in the renin affects the system output, mostly angiotensin II and aldosterone (Dusso and Tokumoto, 2011). These hormones use several mechanisms, and both hormones trigger the uptake of sodium chloride, increasing the extracellular fluid compartment and increasing the blood pressure. When the levels of renin are increased, angiotensin II and aldosterone also increase, often causing a rise in sodium chloride reabsorption, thereby increasing blood pressure (Schlaich, et.al., 2009). On the other hand, where the renin concentration is low, angiotensin II and aldosterone also decreases, leading to a lowering of the blood pressure. Anatomy of the kidney The kidney is shaped like a bean. The concave area is known as the renal hilum where the artery and the vein pass out and into the kidneys (Jackson and Ott, 2005). The kidney is mostly made up of tough fibrous tissues on the outside known as the renal capsule (Jackson and Ott, 2005). The peritoneum forms the anterior of these tissues, and the posterior is made up of the transversalis fascia. The upper border of the right kidney is located near the liver, and the spleen is found near the left kidney (Jackson and Ott, 2005). Downward movement is therefore expected during inhalation. The parenchyma has two major structures – the renal cortex and the renal medulla (Rosdahl and Kowalski, 2008). These two structures make up 8 to 18 renal lobes which include the renal cortex supported by a renal pyramid. Renal columns form projections within the cortex and the nephrons span the length of the cortex and the medulla (Rosdahl and Kowalski, 2008). Initially, the renal corpuscle is the first filtering area of the nephron. Nephrons are the primary functioning parts of the kidney. Their main function is to manage the consistency of water as well as other soluble elements through the process of filtration (Rosdahl and Kowalski, 2008). Reabsorption occurs and helps ensure that essential elements would be returned to the system and the rest would be eliminated in the urine. The nephrons are elongated tubular structures with one end being closed and folded like cups (Encyclopaedia Britannica, n.d). Such structure is known as the Bowman’s capsule which covers groups of blood vessels (glomerulus). The capsule as well as the glomerulus make ups the renal corpuscle. Blood enters the glomerulus through arteriole blood vessels, these blood vessels is also the exit point of the blood (Encyclopaedia Britannica, n.d). Through the renal corpuscle, fluid is eliminated from the blood and dumped into the nephron tubule. The consistency and composition of the filtrate is changes through the introduction of various substances and through the reabsorption of water (Encyclopaedia Britannica, n.d). Urine is the final product which is then transmitted through the tubules and directed to the renal pelvis (Encyclopaedia Britannica, n.d). (UNC Kidney Center, n.d) Blood enters the kidneys through the arteries. The renal arteries divide into the segmental arteries and branching out into the interlobar arteries that enter the renal capsule and ply the renal columns and the renal pyramids (White, 2005). Such interlobar arteries bring blood to the arcuate arteries located in the cortex and medulla. The arcuate artery supports the interlobular arteries which drain into the afferent arterioles supplying the glomeruli (White, 2005). The interstitium is found underneath the filters filled with blood vessels. It allows the entry of fluid absorbed from the urine (Jorres, et.al., 2010). Different conditions can also cause scarring and congestion, eventually leading to failure and related kidney issues. After the filtration process, the blood goes through various veins culminating in the interlobular veins (Jorres, et.al., 2010). The veins also go through a similar emptying pattern with the interlobular supplying blood to the arcuate veins, then retreating to the interlobular veins forming the renal vein, and finally exiting the kidney. Kidney excretion In the glomerulus, the different molecules with low weight are extracted from the blood. Insulin is usually easily filtered in the glomerulus and is not made part of the reabsorption process (Parving, et.al., 2009). Most drugs are extracted from the blood within the glomerulus however the main renal excretion is limited by the tubules. About 90% of filtrate is then reabsorbed into the blood. Within the proximal tubule, reabsorption of water happens, including active secretion of weak electrolytes (Parving, et.al., 2009). Since this process is considered active secretion, it calls for a carrier. There is usually passive excretion in the distal tubules as well as re-absorption of fat-soluble drugs. Drugs which are seen in the glomerular filtrate can also be extracted from the tubules (Bourne, 2001). The membrane is very much permeable to lipids. Most of the water has already been extracted and the concentration gradient is reabsorbed. Types of dialysis Dialysis is the primary medical procedure used to replace and support the kidney’s filtration process. There are different types of dialysis, mainly the hemodialysis and peritoneal dialysis (Daugirdas, et.al., 2012). For purposes of this essay, hemodialysis and peritoneal dialysis will be highlighted. For hemodialysis, the patient’s blood is passed through a dialyzer where it is managed through a partially permeable membrane (Daugirdas, et.al., 2012). The dialyzer is made up of small synthetic fibres which perform semipermeable membrane functions. As the blood is sifted via the fibres, the dialysis solution gathers on the external walls of the fibres where water as well as waste materials are transported between the different solutions (Ahmad, et.al., 2008). The clean blood is then reintroduced into the circuit and moved back into the body (Daugirdas, et.al., 2012). Ultrafiltration unfolds when the hydrostatic pressure is increased within the dialyzer. This occurs when negative pressure is used on the dialysate chamber of the dialyzer (Ahmad, et.al., 2008). Such pressure would push the water and solutes out of the blood into the dialysate, ensuring the elimination of excess fluid during the dialysis treatment. The other type of dialysis is peritoneal dialysis. In this procedure, a sterile solution rich in glucose is passed through a tube and entered into the peritoneal cavity (Offer, et.al., 2007). The cavity then serves as the partially permeable membrane. The peritoneal membrane is made up of tissues rich in blood vessels which surround the abdominal cavity as well as the organs located in the abdominal region (Blake and Daugirdas, 2008). The dialysate is lodged there for a certain length of time in order to extract the waste products. The waste is then passed through the tube and then eliminated from the body. This process is repeated several times in the day and sometimes at night, depending on the type of system being used (Blake and Daugirdas, 2008). One exchange includes the process of the dialysate filling and emptying into the abdomen. Dwell times represent times when the dialysate is lodged in the patient’s abdominal cavity and all the waste materials as well as extra fluids are extracted from the blood into the dialysate and then through the peritoneum (Blake and Daugirdas, 2008). Differences between peritoneal and hemodialysis Basic differences between these two types of dialysis are very much apparent. First, in peritoneal dialysis, a catheter is directly inserted into the abdominal cavity; for hemodialysis however, a shunt between the vein and artery is indicated (Harris, et.al., 2005). Second, for peritoneal dialysis, the peritoneum itself provides a filtration process between the dialysis solution and the blood. For hemodialysis, there are various fibres in the machine which acts to clean out the blood (Harris, et.al., 2005). Third, peritoneal dialysis usually occurs several times a day, but hemodialysis is usually carried out 3-5 times a week for about six to eight hours per day. Fourth, peritoneal dialysis is usually done at home by the patient himself, but for hemodialysis, this is carried out in a clinic or hospital with the assistance of medical professionals (Harris, et.al., 2005). Fifth, osmosis is the primary process which is carried out during peritoneal dialysis; but for hemodialysis, an artificial machine is used in order to carry out the filtration process. Finally, peritoneal dialysis represents a greater degree of dietary liberty for patients, meaning, there are less restrictions on their diet. For hemodialysis patients however, they have to follow a strict diet regimen (Harris, et.al., 2005). In general, the kidneys help maintain the body’s normal balance of fluids and minerals including sodium, chloride, and sulphates. The by-products of the acid metabolism which are not eliminated during respiration are eliminated via the kidneys (Sander, 2010). The kidneys also form part of the endocrine system as it releases erythropoietin and calcitriol. The erythropoietin is part of the process which manages the release of red blood cells; calcitriol is needed in the formation of bones. Dialysis replaces majority of the kidney’s functions; however, it cannot manage the endocrine functions of the kidneys (Sander, 2010). Dialysis helps in the filtration process, mostly in the elimination of waste as well as in the elimination of fluids from the body. Dialysis functions through the process of diffusion and ultrafiltration of fluids through a semi-permeable membrane (Sander, 2010). The usual movement of substances in water is facilitated by diffusion where transportation occurs (Mosby, 2006). Filtration process of the kidney is replaced by the process of dialysis. Blood would pass through a semi-permeable membrane and dialysis fluids passes at opposite ends of the membrane. Smaller substances and fluids go through the membrane, however, the membrane prevents the entry of larger particles (Sander, 2010). This is similar to the filtration process of the kidneys, where the blood goes through the kidneys and the bigger particles are removed from the smaller particles in the glomerulus (Mosby, 2006). The two main kinds of dialysis carry out kidney functions by eliminating waste and excess fluids from the body. In general, solutes like potassium and phosphorus are highly dense in the blood, but are not seen in the dialysis solution (Gray and Sands, 2002). The solution has ideal levels of potassium and calcium, very much like those found in healthy blood. Through the interactions between the fluids and the membrane, the process of filtration of the blood is carried out. Conclusion Based on the above discussion, the renal system performs a complex process which eventually assists in the elimination of waste products and excess fluids from the body. It also helps the endocrine system in maintaining homeostasis of the body. Dialysis replaces the filtration process of the kidneys through peritoneal or hemodialysis. It cannot however replace the endocrine functions of the kidneys. Nevertheless, dialysis assists in the management of chronic kidney sufferers as well as other patients with renal system affectations. References Ahmad, S., Misra, M., Hoenich, N., and Daugirdas, J., 2008. Hemodialysis apparatus. In: Handbook of Dialysis. London: Routledge. Blake, P. and Daugirdas, J., 2008. Physiology of peritoneal dialysis. In: Handbook of Dialysis. London: Routledge Bourne, D., 2001. Renal excretion [online]. Available at: http://www.boomer.org/c/p3/c27/c2702.html [Accessed 29 December 2012]. Daugirdas, J., Blake, P., and Ing, T., 2012. Handbook of dialysis. London: Lippincott Williams & Wilkins. Desmukh, S. and Wong, N., 2009. The renal system explained: an illustrated core text. London: Paul & Company Pub Consortium. Dusso, A. and Tokumoto, M., 2011. 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