The endocrine system is composed of various hormone-secreting organs that are spread across various parts of the body. Their fundamental function is the secretion of one or more hormones and releasing them to the target cells. Each of the hormones is vital for the normal operation of the body. The body, through the nervous systems, detects the various conditions of the body and initiates the release of the associated hormone to achieve the corrective measure (Marieb, Hoehn & Hoehn, 2019) . As noted by Neal, (2016), the failure of the body to produce a required hormone such as insulin causes diseases like type 2 diabetes. As such, the patients get cure through an artificial administration of the hormone in regimens than mimics their natural release (Rodriguez-Manas, 2017). The three fundamental hormone-producing glands are the pituitary glands, pancreas, and thyroid glands. They differ in location, size, and function. For instance, the pituitary gland is located in the brain, produces antidiuretic hormones and aldosterone. Both hormones are vital in osmoregulation.
How the Antidiuretic Hormone Affect the Amount of Water in the Body and Its Effects on the Blood Osmolarity
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The human body consists of an average of 60% water. The water needs to balance because of a strict solute concentration in the body fluids and the constant secretion of water through physiological activities. Water concentration in the extracellular body fluids is relatively stable despite having various avenues of gaining and losing. The balance depends on the regulation of water level in the body that is achieved by two main hormones; aldosterone and Antidiuretic Hormone (ADH). The two hormones' actions in the kidney differ by the ADH, focusing on increasing water reabsorption into the blood. In contrast, aldosterone acts on balancing the concentration of solutes that include sodium and potassium in the body. Consequently, the concentration of solutes affects the water balance in the body (Neal, 2016) . Therefore, ADH forms an important participant in the discussion of water balance that it achieves by a regulated release that affects the kidney and the vascular system.
Given that the ADH has a profound effect on the balance of water and blood concentration, the hypothalamus highly controls its secretion. First, it is made by the cell bodies of the neurons in the hypothalamus. Then it is stored in the infundibulum of the axons of the hypothalamus neurons. It is released is depending on the osmolarity of the plasma detected by the hypothalamus. ADH is then released into the bloodstream from the posterior pituitary glands in response to a request from the hypothalamic neurons (Marieb, Hoehn & Hoehn, 2019) . Its presence in the blood affects the kidney and the vascular system.
As discussed by Marieb, Hoehn, and Hoehn (2019), the presence of ADH in the bloodstream increases the kidney's ability to retain water. It enhances the permeability of water through the walls of the collecting duct and the distal convoluted tubule back into the blood. In detail, the presence of ADH facilitates the insertion of water channels called aquaporins into cell membranes of the kidney's distal convoluted tubules and collecting duct. Given that the kidney tubes are responsible for holding the fluid that forms urine, aquaporins facilitate water to re-enter the kidney’s cells cytosol. Then, the water travels to the blood through the extracellular fluid by osmosis.
The re-entry of water into the blood dilutes the concentration of solutes hence decreasing the osmolarity of the blood. Similarly, some species arteries react to the presence of the ADH by constricting the arterial walls. The constriction increases arterial pressure that alters the osmolarity of the blood. A feedback mechanism detects the osmolarity of blood and alters the release of ADH.
In summary, ADH is one of the vital hormones that regulate the volume of water in the body. The posterior pituitary glands release it into the blood after its manufacture in the cell bodies of the hypothalamus neurons. A variation of the concentration of ADH in the bloodstream depends on the osmolarity of the blood. An increase in the presence of ADH in the bloodstream enhances the permeability of the kidney's collecting duct and distal convolutes tubule. As a result, the reabsorbed water would have otherwise been wasted through urination. The reabsorption of the water decreases the consecration of the blood that adjusts the levels of ADH released through a feedback mechanism.
The Effect of Blocking Aldosterone Secretion
Aldosterone is one of the major hormones that participate in the regulation of water volume in the body. It is also fundamental in the regulation of the blood's volume, pressure, and osmolarity. It maintains the water level in extracellular fluid constant and balances blood’s osmolarity, pressure, and volume by controlling the reabsorption of water, sodium, and potassium ions in the kidney. Aldosterone and ADH complement each other in their functions. Thus, the blocking of aldosterone secretion at high blood osmolarity increases water reabsorption. Conversely, it decreases the reabsorption of water from the kidney fluids when the osmolarity of the blood is low, and the volume is high.
Sodium ions are the majority of ions in extracellular fluids. Therefore, aldosterone acts directly on the kidney's distal convoluted tubule and collecting duct by increasing the reabsorption of sodium ions into the extracellular fluids. As such, the osmolarity of the blood increases. Blocking the secretion of aldosterone at high blood osmolarity decreases the kidney's fluid water retaintion. Normally, a high blood osmolarity triggers the blockage of aldosterone release and enhances the secretion of ADH. The net effect is more reabsorption of water to reduce the blood's osmolarity and an increased solute concentration in the urine.
However, when the secretion is blocked when the osmolarity of the blood is low, and the blood volume is high. The body gets into a complex reaction of balancing the blood volume and osmolarity. As such, ADH concentration reduces in the blood, and more water is allowed to remain in the kidneys fluids that form urine.
In summary, the blockage of aldosterone can initiate an increase in water reabsorption or retention of water in the kidney's fluid that form urine. Blocking aldosterone when the blood osmolarity is abnormally high, initiates a high rate of water reabsorption. The body reacts by the pituitary glands releasing ADH that enhances water reabsorption to balance the blood osmolarity. However, when it is blocked when the blood osmolarity is low, and the volume is high, the reabsorption of water decreases so that the blood osmolarity can drop to the required levels.
A Comparison of Three Hormone Producing Organs in the Human Body
The human body consists of various hormone-producing organs that are called glands. Glands and are fundamental for its normal functioning. Three of the fundamental hormones producing organs are the pituitary glands, the pancreas, and thyroid glands. The three glands share similarities, such as the production of hormones. They, however, differ in the type of hormones they produce, their location, size, and the functions of the hormones they produce.
The first difference between the three hormone-producing organs is their location. The pituitary glands are located in the brain just behind the nose bridge. It lies between the pineal gland and the hypothalamus. On average, it is the size of a pea that is divided into the posterior and frontal lobe. It is attached to the brain by a stem consisting of nerve cells and blood cells. The pancreas is the second hormone-producing organ. It is located in the abdominal cavity behind the stomach. It stretches an average of fifteen centimeters from the right of the abdominal cavity at the start of the small intestine towards the left. It is attached to the small intestine by a small duct called a pancreatic duct. Finally, the thyroid gland is located on the front part of the neck just below Adam's apple. It surrounds the windpipe in a manner that mimics a butterfly though smaller than an average butterfly.
The three hormone-producing organs also differ in the range of hormones they produce and their functions in the body. For instance, the pituitary glands produce seven types of hormones. They are; Antidurentic hormone, oxytocin, prolactin, endorphins, enkephalins, Beta-melanocytes, and growth hormones such as somatropin. The antidiuretic hormone is responsible for the regulation of water reabsorption in the kidney. As such, it targets the kidneys collection duct and the distal convoluted tubule by enhancing its permeability. Oxytocin, on the other hand, targets the uterus and the mammary glands contraction. Hence it controls milk secretion, birth, and sustenance of pregnancy. As discussed by Burgstaller, Paulus, and Pfundmair, (2019), oxytocin is also responsible for enhancing prediction through processing and perception of social cues . The pituitary glands also produce the prolactin. Prolactin is responsible for the stimulation of milk production in the cells of the mammary glands. Other functions of the hormones secreted by the pituitary glands include the darkening of the skin cells that are accomplished by Beta-melanosis. Endorphins are other hormones that regulate the immune system and inhibit pain receptors when working in conjunction with Enkephalins. Finally, growth hormones such as somatropin target the non-specialized body cells and enhance their cell division. The growth hormone also enhances cell health and increase metabolism that enhances growth.
The pancreas, on the other hand, produces five hormones. The hormones are insulin, somatostatin, glucagon, gastrin, and vasointestinal peptide (VIP). Insulin acts on the body cells by encouraging them to absorb and break down the glucose. On the contrary, glucagon targets the body cell by encouraging them to release glucose when regulating the level of glucose in the body. Somatostatin is secreted to balance the glucose level in the blood. Gastrin is another pancreatic hormone. It targets the stomach cells by encouraging them to produce hydrochloric acid. Finally, VIP targets the intestinal cells. VIP controls water absorption and secretion in the intestines.
The thyroid glands produce three hormones. The hormones are tetraiodothyronine triiodothyronine and calcitonin. The calcitonin is a hormone that regulates the level of phosphates and calcium in the body. It acts by suppressing tetraiodothyronine and triiodothyronine. Tetraiodothyronine and triiodothyronine act on the body cells by increasing the basal metabolic rate (Hammam, Jouda & Hashem, 2016) . An increase in the basal metabolic rate increases the body temperature, heart rate, promotes growth, activates the nervous system, and enhances the body’s utilization of food.
In summary, the fundamental hormone-producing organs in the human body are the pituitary glands, the pancreas, and thyroid glands. They share the similarity of producing hormones that are vital for the normal functioning of the body. On the contrary, they are located on different parts of the body, differ in size, and produce different numbers of hormones that have unique functions. For instance, the pituitary gland is the smallest of the three glands, yet it produces seven hormones that act on the various cells in the body that include the mammary glands cells, the skin cells, and the kidney cells. Some of the main functions of the various hormones include regulation of body functions such as reabsorption of water done by ADH and secretion of milk controlled by prolactin. Other functions include inhibition, such as endorphins that inhibit pain receptors.
Conclusion
From the discussion above, the pituitary glands, pancreas, and thyroid gland produce several hormones that are vital for the functioning of the body. However, they are located in different parts of the body. For instance, the pituitary gland is located in the brain. It is responsible for controlling functions of the body in other parts of the body, like the kidney, skin, and the brain. One of its main functions in the kidney is osmoregulation. The pituitary glands release two hormones; ADH and aldosterone that directly affect the reabsorption of water and solutes into the blood. The pancreas, on the other hand, is located in the abdominal cavity. It mainly controls metabolism and water reabsorption in the small intestine. Finally, the thyroid glands are located in the neck. They control metabolism by synthesizing hormones that alter the metabolic base rate and levels of calcium and phosphorus in the body.
References
Burgstaller, J., Paulus, M., & Pfundmair, M. (2019). Oxytocin promotes action prediction. Hormones And Behavior , 107 , 46-48. DOI: 10.1016/j.yhbeh.2018.09.004
Hammam, A., Jouda, A., & Hashem, M. (2016). Serum Total Triiodothyronine versus Free Tetraiodothyronine and TSH in Patients with HCV Related Cirrhosis and Their Correlation to the Severity of Cirrhosis. Open Journal Of Gastroenterology , 06 (03), 75-82. DOI: 10.4236/ojgas.2016.63010
Marieb, E., Hoehn, K., & Hoehn, K. (2019). Anatomy & physiology (11th ed., pp. 586-628). Pearson Education.
Neal, J. (2016). How the endocrine system works (2nd ed.). Wiley.
Rodriguez-Manas, L. (2017). How to manage diabetes in the elderly?. Endocrine Abstracts . DOI: 10.1530/endoabs.49.mte1
