Kidney Structure and Function
The kidney is an internal body organ used for cleaning the blood. It is worth mentioning that the vital function takes place in three stages. The first stage is the filtration of small molecules including glucose, urea, ions, and water from the blood as it moves through the blood vessels to the kidney. The second step is the selective reabsorption where all of the glucose is filtered out, the essential amount of water is supplied to the blood plasma, and the ions are reabsorbed in accordance with body demand (Zhu, Wang & Zhongguo, 2010). Finally, the last step is the formation of urine constituting of the urea, excess water and ions.
To start with, the blood is cleaned as it passes through the various parts of the kidney. First of all, the blood enters the kidney through the renal artery and then to the medulla through the smaller blood vessels. Each of medulla arranged in the form of pyramids containing about 2 million nephrons upon which the filtration, reabsorption and formation of urine take place. Some of the filtered-in blood components are reabsorbed and forced to rejoin the bloodstream through the renal vein (Britt & Peitzman, 2012). The urine constituting of water, urea, and ions moves out of the kidney through the ureter.
In addition, the stress hormones including norepinephrine, epinephrine and cortisol affect the functions of the kidney. Especially, epinephrine responds to stress by increasing heart rate leading to rushing blood to the muscles and brain. The hormone also helps in the conversion of glycogen to glucose to increase blood sugar level. In contrast, norepinephrine works with epinephrine to cause the narrowing of blood vessels resulting in high blood pressure (Zhu, Wang & Zhongguo, 2010). Lastly, cortisol triggers the releasing of stored glucose from the liver by increasing the energy supply in the body. The hormone also assists in the retention of sodium and fluid to keep the blood volume high.
The pathway in the response to stress follows a range of activities. Especially, the first step is that the stressor activates the Hypothalamic Pituitary Axis which in turn stimulates the pituitary gland that secretes corticotrophin hormone stimulating the adrenal glands to produce the hormones cortisol and epinephrine. The hormones enable the body to maintain steady supplies of blood sugar. Additionally, noradrenaline is released from the sympathetic nervous system and works in combination with epinephrine in narrowing of blood vessels and increasing the blood pressure.
Dehydration is the situation when the amount of water in the body is inadequate. The situation affects the functionality of the body cells, tissues, and muscles and can lead to death if the dysfunction is prolonged. The problem can arise when one loses a lot of water through sweating and urination while the intake is relatively low. The primary remedy to the problem is to increase the intake of water. Nevertheless, the body has a system to respond to the situation with the kidney playing a vital role. Especially, the brain detects that there is a shortage of water and released the anti-diuretic hormone (ADH) (Koeppen, 2012). ADH travels to the kidney through the blood flow and triggers the tubules to reabsorb an increased amount of water. Eventually, the dehydration problem is controlled, and the urine released to the bladder is more concentrated.
Caffeine is the most abused drug in the world. Particularly, the excessive intake of the substances with the drug affects the functionality of kidney. It is evident that methylxanthines, to which caffeine belongs, is a mild diuretic and prevents reabsorption of water leading to more urine output. Moreover, the drug makes the arteries in the kidney less flexible. Such unstable surface of blood vessels can increase the blood pressure and reduce the effectiveness of the kidney. Ultimately, the loop of Henle is the most likely part of nephron to be affected because it is the place where water absorption occurs.
