The Digestive System

TheDigestive System

Endocrineand neutral control of the digestive process in the stomach and smallintestine

Theendocrine secretes hormones that drive the digestive systems and thesensations of hunger. When a hungry person smells food, the nervoussystem initiates a process that compels the person to seek the food.For example, the salivation process is involuntary, and it preparesthe mouth for food. At the same time, the stomach secreteshydrochloric acid in anticipation. When the person eats the food,there are nerve receptors in the stomach that signal satisfaction andsends signals to the person to stop eating thus, the appetite diesdown. In the stomach, the gastric phase of digestion takes place. Theprocess compels conditions such as muscle contractions thatfacilitate the digestion of the food.

Onceall the food in the stomach has moved on to the intensities and thestomach is empty once again, the entire process starts again.Meanwhile, the food leaving the stomach called the chime triggers theintestinal phase (Marieb and Hoehn 868). The phase is regulated byhormones and is characterized by absorption of food materials asneeded by the body. Where certain elements are absent, hormonestrigger a craving. For example, thirst is a craving for water createdby low levels in the blood.

Thehormones control the entire digestive system because they detectshortages of certain substances in the body and create a craving. Inaddition, hormones control the secretion of digestive enzymes. Forexample, where there are low levels of sugar in the blood, thepituitary glands secrete adrenaline, and insulin, two hormones thatincrease the process of secretion of food. The heightened feelingscaused by adrenaline are responsible for the moodiness associatedwith hunger.

Metabolismand breakdown of glucose

Themetabolism of glucose releases energy necessary for functional suchas metabolism, brain functions and other cell activity. In the body,glucose is stored in the form of glucagon. Glucagon is stored in theliver, and when the blood sugar is low, the pancreas secretesinsulin, a substance that triggers the conversation of glucagon toglucose. Glucose is soluble in the blood plasma, and it dissolves inthe plasma and is transported to all parts of the body.

Themitochondria, components of all cells, are like the engine of thebody. In the mitochondria, the glucose reacts with oxygen to releaseenergy and form water and carbon dioxide. There is a highconcentration of mitochondria in muscles because of the heavy energyrequirements in the muscular organs.

Theprocess of metabolism of glucose is in three phases, conversion fromglucagon to glucose, and transport of the glucose to the cells andfinally the chemical reaction of the glucose with oxygen to secreteenergy. The process of metabolism in the cells has two steps tomanage the levels of energy released and prevent damage to the cells(Marieb and Hoehn 922). In addition, the body requires small amountsof energy at a time.

Thefour papillary in the tongue

Filiformpapillae: They are the most common papillae, and they do not havetaste buds. They are found at the front of the tongue and have acylindrical structure. They give the tongue the rough texture inanimals such as cats, and they have no function in the digestiveprocess.

Fungiformpapillae: They are mushroom shaped when viewed longitudinally andusually located at the tip of the tongue. They have taste buds, whichextricate the five tastes: sweet, bitter, salty, sour, and Umami(Marieb and Hoehn 860). At the core, they have connective tissues,and the seventh cranial nerve innervates them. The seventh nerve alsocalled the facial nerve, controls facial expressions. Therefore, itis usually possible to tell the taste of a substance by observing thefacial expressions of a person, unless a person inhibits theseexpressions.

Foliatepapillae: These are short and vertical folds present on all sides ofthe tongue. Their services are softer than the other papillae and areoften mistaken for tumors or inflammations. They have some tastebuds, but they are not able to function as well as the taste buds onthe fungiform papillae.

Circumvallatepapillae: They are situated at the back of the tongue, and areusually between 10 and 14 in the average person. They are connectedto the Von Ebner`s glands, and they make a secretion that cleans thetongue and thus facilities fast response to new tastes. The locationof the Von Ebner`s glands resembles a moat because it is never dry.

Thethree salivary glands

TheParotid glands: The parotid glands are located close to the years.They are two, and they are the largest glands in people. They secretesaliva that helps a person to swallow food. The saliva also containshormones that initiate the digestive process of starch before it evenreaches the stomach. After eating starch, a person is left with asugary sensation at the base of the tongue because of the conversionof starch to sugar by saliva.

Submandibularglands: They are salivary glands located at the bottom part of theback of the mouth. Their location is similar to that of thesublingual glands, but instead of being at the front of the mouth,they are at the back.

Sublingualglands: they are located under the tongue, and they secrete saliva.

Allsalivary glands secrete saliva. Saliva has two components, the mucousand the serous. The mucous plays lubrication purposes and is madeprimarily of water. It keeps the mouth moist and helps people toswallow hard food. The serous is an enzyme that starts the digestionof carbohydrates.

Thefunctions and structure of the liver

Theliver is found beneath the diaphragm and is protected by the ribcage. It is the largest internal organ in the body, and it is made ofconnective tissues. It has four main lobes. However, it appears tohave two main lobes, with the right lobe larger than the left. Thebile duct is locatedon the right and the left lobes of the liver. Thefunctional units of the liver are calledlobules, and each lobule isconnected to a vein that empties into the hepatic veins (Marieb andHoehn 942).

Themain function of the liver is the filtration of blood coming out ofthe digestive track. The liver detoxifies the blood before it moveson to other body systems and metabolizes drugs. The secretion ofbile, an important chemical in detoxification of food and digestionof proteins, is also secreted in the liver. Due to the detoxificationfunction and the fact that the liver is the first organ to encounterany toxics from the digestive system, it is susceptible to manydiseases. For example, one of the biggest negative effects of alcoholis on the liver.

Theliver is among the most important organs in the body but can sufferextensive damage before it is unable to perform its functions. Someof the functions of the liver include storage of glucagon, thematerial that is later converted to glucose. The liver also convertsthe excess carbohydrates to fats for storage and metabolism ofhormones. Hormones metabolized in the liver are called steroidalhormones. Bile is also secreted by the cells of the liver and storedin the bile duct. Bile is an essentialconstituent of the digestivemethod because it helps in the process of emulsification of fats.Consequently, the liver has an imperative part in the digestiveprocess.


Marieb,Elaine Nicpon, and Katja Hoehn. Humananatomy &amp physiology.8thedition. Pearson Education, 2010.