Last Updated 20 Mar 2021

Human Biology Digestive and Urinary System Essay

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The human body needs to maintain proper homeostasis to survive. There are several different organ systems in the human body. Two of those systems are the digestive system and the urinary system. Both systems remove waste from the body but in an entirely different way. They also maintain homeostasis within our blood stream. Both systems are critical for survival. This paper will describe how each of those systems works on its own and also how they work together to maintain homeostasis for the body.

How the Urinary and Digestive Systems Work Together to Maintain Homeostasis

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The digestive system works to bring nutrients into the body with a series of hollow organs working together extending from the mouth to the anus. These hollow organs are the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus. These hollow organs make up the gastrointestinal (GI) tract. The GI tract is aided by four accessory organs, the salivary glands, liver, gallbladder, and pancreas. Johnson) There are five basic processes of the digestive system. These processes are motility, secretion, digestion, absorption, and excretion.

Motility is the mechanical processing and movement of food taken into the body. Chewing breaks food into smaller pieces, and two types of movement mix the contents of the lumen and propel it forward. The lumen is the inside lining of the GI tract. Secretion is the fluid, digestive enzymes, acid, alkali, bile, and mucus that are secreted into the GI tract at various places.

Digestion is where the contents of the lumen are broken down mechanically and chemically into smaller and smaller particles, culminating in nutrient molecules. Absorption is what happens when the nutrient molecules pass across the GI tract and into the blood. Elimination is all of the undigested material is eliminated from the body through the anus. (Johnson) These GI tract and the four accessory organs of the digestive tract work together to complete the five processes in order to bring nutrients into the body, and eliminate waste. The large intestine absorbs nutrients and eliminates waste.

The small intestine absorbs nutrients and water. The water and nutrients absorbed from the intestines go into the blood stream . (Johnson) The urinary system consists of the kidneys, ureters, bladder, and urethra. The ureters, bladder, and urethra transport and store urine until it is eliminated from the body. The kidneys produce urine. Urine is the nitrogenous waste removed from the blood stream. It is essential to the body to remove this waste in order to maintain homeostasis. (Johnson) The kidneys perform all of the main functions in the urinary system.

They regulate water levels in the body. When you take in water every day it is up to the kidneys to excrete the excess water or to conserve as much as possible. The kidneys have a great capacity to adjust water excretion as necessary. Normally with a minimum of a half liter per day to one liter per hour. (Johnson) The kidneys also regulate the nitrogenous waste and other solutes in our blood. One waste that is toxic to our cells is ammonia. Ammonia is detoxified quickly by the liver by being combined with carbon dioxide to create urea.

Urea is the main waste product in urine. Sodium and chloride are both regulated by the kidneys as well. Sodium and chloride are both very important to determine the volume of extracellular fluids, like blood. This directly affects blood pressure. (Johnson) Other substances that the kidneys regulate are potassium, calcium, hydrogen, and creatinine. It is up to the kidneys to maintain homeostasis with each of these substances. Creatinine is a waste product that is produced during metabolism. This is one of the wastes that give urine a yellow color. (Johnson) The digestive system removes nutrients and water from the food that we eat and drink and transports it to our blood stream. Any solid wastes that are unable to be digested are then eliminated from the GI tract. Our urinary system then removes any of the unwanted and unneeded substances and wastes from the blood stream and excretes them in urine. This is how homeostasis is maintained in our body with waste, so that there is no toxic build up in our body from certain substances. Homeostasis is critical to be maintained within the body for survival.

Homeostasis is the body’s ability to maintain relatively stable internal conditions even though the outside world is continuously changing. (Marieb) All living things must maintain an internal environment compatible with life, and the range of chemical and physical conditions compatible with life is very narrow. (Johnson) In order for the digestive and urinary systems to work together to maintain homeostasis both systems must be functioning properly. First we consume food and water. Then our digestive system absorbs the nutrients and water into our blood stream.

Once the nutrients and water is in our blood stream our urinary system the filters the blood and removes any additional waste and maintains the proper homeostasis with the nutrients we consume. If our digestive system is not functioning properly then we are not able to absorb the proper nutrients and fluids in order to allow our kidneys to filter our blood and maintain homeostasis. If our urinary system is not functioning properly than the nutrients and fluids we consume can cause a buildup in our blood stream of toxic wastes and fluids and throw off homeostasis.

Either way it would be detrimental to our body for this to happen. Our blood pressure would be affected severely and this would cause issues with not only our cardiovascular system but also our respiratory system. It is critical to keep both systems healthy to ensure that our body’s have the proper water and nutrients to survive and that all waste is secreted from our systems.


  • Johnson, Michael D. Human Biology: Concepts and Current Issues-sixth edition. Pearson Education. 2012. Print.
  • Marieb, Elaine Nicpone. Essentials oh Human Anatomy and Physiology-tenth edition. Pearson Education. 2012. Print.

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