What is stomach? embryonic development and functions of stomach along with disease related to stomach

STOMACH

introduction
Like all of the other important systems operating in the body and their various important components that forms the those systems and without which body cannot work properly. Among those systems of the body of the living organisms there is a system that goes by the name of digestive system and without this system body can't digest the food taken that ultimately would be broken further and further and from which there would be energy extraction that acts as the fuel of the body on which the whole body works and the most important component of this digestive system without which the whole process of digestion is impossible goes by the name of stomach. Stomach is the most vital digestive organ of the body of the humans as well as all the other animals that have a proper digestive system. Stomach is a J-shaped muscular and a hollow organ of the gastrointestinal tract and it is located between the esophagus and the duodenum region of the small intestine. If we talk about the position of stomach in the abdomen than we can say that it lies in the upper part of the abdomen occupying the epigastric umbilical and the left hypochondriac regions. Lying behind the stomach is the Pancreas  and the top of the stomach lies against the Diaphragm. The precursor of the stomach from where this organ arises is the foregut. The only and the most crucial function of the stomach is the digestion of food specifically the protein part of the food such that it gets the food from the esophagus and after its digestion action it sends the food for further digestion to the duodenum region of the small intestine if we want to make a few points about the functions of the stomach than we can describe them as

  • food storage 
  • food digestion
  • some absorption
  • defense that HCL provides against the germs 
stomach is the only organ of the body that makes the discontinues eating possible. Stomach is one of the organ of the body that have great stretching ability and its storage capacity varies with the age such as the time of birth the storage capacity of stomach is about 30 ml where as the time of puberty it increases to about 1 litre whereas in a fully mature adult its capacity is about 1.5-2 litres whereas the stomach is about 12 inches long and is about 6 inches wide. There is a preventive measure that prevents back flow from both sides of the stomach such that of that structure prevents the digested stomach content to go back into the esophagus as it have the ability to destroy the internal lining of the esophagus because of its acidic nature and on the other hand the other structure prevents the entry of food from the duodenum into the stomach and these two structures or sphincters are named as following

  • cardiac sphincter 
  • pyloric sphincter
such as cardiac sphincter is between the stomach and the esophagus whereas the pyloric sphincter is between the stomach and the duodenum region of the small intestine. The whole structure of the stomach is made up of the following parts or we can say that these are the parts into which the whole structure of the stomach is divided into and they are

  • cardiac region 
  • pyloric region
  • fundus
  • body of the stomach
stomach is lined by peritoneum on both its surfaces. The walls of the stomach is composed up of these layers

  • serosa or also known as adventitia
  • muscularsis externa along with the submucosa
  • mucosa
the main arteries of the body that provides oxygenated blood supple to the stomach are as following

  • right gastric artery
  • left gastric artery
  • right gastro-omental artery
  • left gastro-omental artery
  • short gastric arteries
where as the veins that takes the deoxygentaed blood away from the stomach for the process of oxygenation are as following

  • right gastric vein
  • left gastric vein
  • right gastroepiploic vein 
  • left gastroepiploic vein
  • short gastric veins 
if we talk about the innervation of the stomach that we can say that nervous supply to the stomach is provided by the following

  • vagus nerve 
  • celiac ganglia 
whereas if we talk about the lymphatic supply of the stomach than we can say that it is provided to the stomach by the 
  • celiac lymph nodes
stomach is made up of specific type of cells and these cells are responsible for the different secretions of the stomach and cells of the stomach along with their secretions are as following 
  • parietal cells of oxynitic cells that secretes HCL
  • chief cells or zymogen cells that secretes pepsinogen 
  • mucous cells that secretes mucous and the role of this mucous is described below 
the sections of all these cells is collectively called gastric juice. The mucosa lining of the stomach is lined with a number of these pits that receives gastric juice secreted by almost 2 - 7 gastric glands.


embryonic development of the stomach
The precursor of the stomach is the foregut. In the second week of the embryonic development in the mother womb the ventral part touches or at the boundary of the yolk sac and as the embryo grows it begins to surround the parts of the sac which the basis for the development of the gastrointestinal tract. This covered sac is surrounded by a network of vitelline arteries than on further development this network becomes the main arteries for the gastrointestinal tract. As the precursor of the stomach is the foregut and the stomach has a dorsal and the ventral mesogastrium and the dorsal mesogastrium gives rise to the greater omentum. Developing stomach at the time of the development shows two different types of rotation. One of the rotation of the stomach is that it rotates at an angle of 90 degrees along the vertical axis that pulls the dorsal mesogastrium to the left side creating the lessor sac or the omental bursa. Whereas the other rotation is along the anteroposterior axis so that the pyloric part of the stomach moves to the right or the cardiac portion moves to the left side and these rotations are responsible for the correct placement of the stomach in the body.

functions of the stomach
The most important and the most vital function of the stomach is the breakdown of food into simple components so that it can be consumed by the body to fulfill its need for the energy and the stomach perform this process of digestion of food by  the digestion as well as somewhat absorption and the gastric juice secreted by the stomach play a very major role in the digestion and the microorganism or the unwanted microbes that can be harmful for the body are destroy at the level of the stomach through the hydrochloroic acid. If we talk about the digestion of the food in the stomach than we can describe it as following. As the food that is digested at the level of buccal cavity moves further into the gastrointestinal tract for the further breakdown such that when the food leaves the buccal cavity and enters into the esophagus it is in a small ball shape structure that is known by the name of bolus and that bolus moves through the esophagus by the peristaltic movements of the esophagus and it ultimately reaches the stomach but first it have to pass through a gate that is present between the stomach and the esophagus and that gate is the cardiac sphincter and this sphincter is opened by the peristalsis movements of the esophagus and this sphincter also prevents from the back-flow of partially digested food from the stomach into the esophagus. Once the food in the form of bolus reaches the stomach than in the stomach the process of digestion begins and for the digestion stomach produces a protein digesting enzyme whose active form goes by the name of pepsin and pepsin is responsible for the break down of the protein in the food taken and the stomach contents is mixed with the food by the process of churning and this occurs when stomach muscle contacts and these muscles are known as rugae that are present at the ridges of muscle tissues. Along with the pepsin in the stomach there is HCL that is responsible for the adjustment of the stomach's pH and makes it to about 2-3 which is the pH in which the pepsin works this HCL also softens the food kills microorganisms and coverts inactive pepsinogen into active form pepsin. After the digestion in the stomach the food that was initially in the form of bolus that is converted into a acidic fluid that is known as the chyme and this chyme moves out of the stomach and goes to the duodenum portion of the small intestine by passing through a sphincter that is known as the pyloric sphincter
Along with the digestion of food stomach is also responsible for the somewhat absorption of food and the things absorbed by the stomach. The absorption of food is mainly the function of the intestines but at the level of stomach some absorption also takes place and the absorption that takes place are of following things 
  • a very little amount of water soluble vitamins 
  • caffeine
  • amino acids
  • some medicines such as aspirin
  • water in case of dehydration
there is one thing that is to be cleared at this point and it is that stomach is responsible for the breakdown of the protein part of the food and the stomach is also made up of proteins so why this same proteins digesting enzyme do not digest the walls of the stomach as they are also proteins and if such a conditions occurs and become worse than there can also be formation of pores in the stomach' wall from where the stomach content that are highly acidic can flow out of the stomach and can cause serious problems. Stomach prevents all of this situation by secreting proteins digesting enzyme pepsin in inactive form pepsinogen so that during secretions it does not effect the internal lining of the stomach and than this inactive form pepsinogen is converted into the active form by the hydrochloroic acid that is present in the stomach and the second thing by which the stomach prevents it is that the internal lining of the stomach is also covered by a layer of mucous that prevents it from being digested.
diseases related to stomach
Like any other organ of the body stomach can also have various conditions that can cause various symptom and mainly stomach conditions occurs as a result of eating habits or eating contaminated food or it can be related to its secretions or there can be various other factors such as there can be problems in its layers cells or secretions. Some of the tests to detect any sort of stomach disorders or diseases are as following 
  • endoscopy
  • Computed tomography
  • magnetic resonance imaging
  • pH testing 
  • barium swallow
  • Helicobacter pylori test
  • stomach biopsy
a major amount of stomach disorder scan be prevented by changing and improving our life style by adopting a healthy life style. Some of the things that we can do to avoid stomach related problems and a good digestion are as following
  • avoid bedtime snacking
  • lose weight
  • quit smoking
  • eat small food
  • avoid carbonated drinks
  • taking proper fiber in the food 
  • drinking enough water
some of the conditions that are related to stomach are as following
  • gastroparesis
  • gastritis
  • zollinger Ellison syndrome
  • peptic ulcer disease
  • gastric ulcers
  • dyspepsia
  • gastro-esophageal reflux
  • pyrosis
  • food poisoning
gastroparesis
Gastroparesis is a condition of stomach in which stomach can't empty itself of food in a normal way. This condition is cased by a injury caused in the vagus nerve and this nerve is responsible for the contraction of the stomach as there would be a damage in this nerve so the stomach muscle controlled can't function properly and the main reason for the damage of vagus nerve is diabetes if we want to conclude some of the reasons as a result of which as a result of which they occur than they are
  • uncontrolled diabetes
  • vagus nerve injury because of any injury
  • Parkinson's disease
some of the symptoms of this condition are as following 
  • vomiting
  • nausea
  • felling full after few bites
  • abdominal pain
  • bloating
  • acid reflux
  • change in blood sugar level

gastritis
Gastritis is a condition of the stomach in which there is an inflammation of the protective lining of the stomach it is of two types that are
  • acute gastritis
  • chronic gastritis
generally it is caused by weakness in the stomach lining on which the digestive juices acts and inflame it or it may be infection caused by a bacterium that is Helicobacter pylori some of the thing that can increase the chances of this condition tto occur are
  • extreme alcohol consumption
  • routine use of non-steroidal inflammatory drugs  
  • aging 
  • tobacco use
  • autoimmune disorders
  • viral infections 
the most common symptoms associated with this condition are
  • vomiting
  • nausea
  • feeling full
dyspepsia
Dypepsia is a condition of stomach in which there is incomplete digestion this is itself not a disease but it can be symptoms of some other disorder or some underlying disease. Some of the symptoms associated with this disorder are 
  • heartburn
  • abdominal discomfort
  • vomiting
  • nausea
gastroesophageal reflux disease
It is a condition of stomach in which there is a back flow of the stomach acid frequently in the esophagus this back flow of stomach content can irritate the lining of esophagus people experiences this condition from time to time some of the common symptoms related to this disorder arre 
  • chest pain
  • heat burn
  • difficulty swallowing
  • sensation of lump in the throat
  • chronic cough
  • laryngitis
  • disrupted sleep
this condition usually occurs when the cardiac sphincter relaxes abnormally or weakens. 


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