TABLE OF CONTENTS I Description of the digestive organs 2 II Process of digestion 3 2 1 Digestion in the Oral Cavity 3 2 2 Digestion in the Stomach 3 2 3 Digestion in the Small Intestine 4 2 4 Digesti. TABLE OF CONTENTS I. Description of the digestive organs 2 II. Process of digestion 3 2.1. Digestion in the Oral Cavity 3 2.2. Digestion in the Stomach 3 2.3. Digestion in the Small Intestine 4 2.4. Digestion in the Large Intestine 4 III. Accessory organs 4 IV. Interesting facts about the digestive system 5 V. Diseases of the Accessory Organs 5 VI. Importance of the digestive system 6 REFERENCE 7 I. Description of the digestive organs The head and neck contain the mouth, oral cavity, and pharynx. Food enters the oral cavity through the mouth, which is bounded by the lips. The roof of the oral cavity is formed by a bony palate, the hard palate. At the posterior end of the hard palate, the bone ends and the roof of the mouth becomes soft, i.e., the soft palate. (The distinction in surface isnt striking on the models, however bone is displayed in the hard sense of taste) The oral cavity is that part of the digestive tract from the lips to the end of the hard palate. Digestion begins in the oral cavity, as digestive enzymes such as amylases secreted in saliva are mixed with the food during chewing. Amylase catalyzes the breakdown of amylose, or starch, into more straightforward carbohydrates. The tongue pushes food from the oral cavity into the region ventral to the soft palate called the oropharynx. Projecting into the oropharynx is a flap, the epiglottis, which partially surrounds an opening at its base, called the glottis. The glottis eventually leads to the lungs. Note the two doors in the pharynx. One goes to the trachea, which is always open due to its cartilage rings, and the other opening is to the esophagus. When food enters the oropharynx, a reflex makes the epiglottis fold back, closing the glottis and allowing food to slide into the esophagus. Once in the esophagus, peristaltic contractions of the esophagus push the food to the Stomach. No digestion occurs in the esophagus. It is just a passageway that connects the pharynx to the Stomach. II. Process of digestion Figure 1: Illustration showing the various organs that form part of the digestive system. 2.1. Digestion in the Oral Cavity When food is taken in through the mouth, chewing and mixing of the food occurs. There is also a chemical breakdown of carbohydrates due to the action of saliva from the salivary glands. 30% of the starch is hydrolyzed by the action of amylase, which is a salivary enzyme. The other enzyme, lysozyme, is an antibacterial agent that prevents infections. Starch + Salivary amylase → Maltose As saliva is added, it mixes with the food particles, slowly moistening and lubricating the food. This small ball is called a bolus, which is then swallowed. 2.2. Digestion in the Stomach
TABLE OF CONTENTS I Description of the digestive organs II Process of digestion 2.1 Digestion in the Oral Cavity 2.2 Digestion in the Stomach .3 2.3 Digestion in the Small Intestine 2.4 Digestion in the Large Intestine III Accessory organs .4 IV Interesting facts about the digestive system V Diseases of the Accessory Organs VI Importance of the digestive system .6 REFERENCE I Description of the digestive organs The head and neck contain the mouth, oral cavity, and pharynx Food enters the oral cavity through the mouth, which is bounded by the lips The roof of the oral cavity is formed by a bony palate, the hard palate At the posterior end of the hard palate, the bone ends and the roof of the mouth becomes soft, i.e., the soft palate (The distinction in surface isn't striking on the models, however bone is displayed in the hard sense of taste) The oral cavity is that part of the digestive tract from the lips to the end of the hard palate Digestion begins in the oral cavity, as digestive enzymes such as amylases secreted in saliva are mixed with the food during chewing Amylase catalyzes the breakdown of amylose, or starch, into more straightforward carbohydrates The tongue pushes food from the oral cavity into the region ventral to the soft palate called the oropharynx Projecting into the oropharynx is a flap, the epiglottis, which partially surrounds an opening at its base, called the glottis The glottis eventually leads to the lungs Note the two doors in the pharynx One goes to the trachea, which is always open due to its cartilage rings, and the other opening is to the esophagus When food enters the oropharynx, a reflex makes the epiglottis fold back, closing the glottis and allowing food to slide into the esophagus Once in the esophagus, peristaltic contractions of the esophagus push the food to the Stomach No digestion occurs in the esophagus It is just a passageway that connects the pharynx to the Stomach II Process of digestion Figure 1: Illustration showing the various organs that form part of the digestive system 2.1 Digestion in the Oral Cavity When food is taken in through the mouth, chewing and mixing of the food occurs There is also a chemical breakdown of carbohydrates due to the action of saliva from the salivary glands 30% of the starch is hydrolyzed by the action of amylase, which is a salivary enzyme The other enzyme, lysozyme, is an antibacterial agent that prevents infections Starch + Salivary amylase → Maltose As saliva is added, it mixes with the food particles, slowly moistening and lubricating the food This small ball is called a bolus, which is then swallowed 2.2 Digestion in the Stomach When food reaches the stomach, it stays for approximately to hours There are various gastric glands in the mucosa lining of the Stomach The mucus neck cells secrete mucus The Peptic Cells secrete the proenzyme pepsinogen The Parietal or Oxyntic Cells secrete HCl (Hydrochloric acid) and intrinsic factor essential for vitamin B12 absorption This mass of food that is semi-digested, acidic and pulpy is called the chyme It is mostly the proteins that get digested in the Stomach 2.3 Digestion in the Small Intestine In the small intestine, further digestion takes place Due to the various movements of this organ, the chyme is further mixed and churned Many enzymes are secreted into the small intestine from organs such as pancreas, liver, and intestinal juices All these react with the food particles and digest them into smaller particles that can be absorbed into the bloodstream 2.4 Digestion in the Large Intestine In the large intestine, the digestion activity is significantly less Here, bacterial action on the leftover food particles occurs Minerals, water, and certain drugs are absorbed in the large intestine The mucus secreted by the large intestine helps in holding the waste particles, apart from lubricating them III Accessory organs Inferior to the Stomach and posterior to the small intestine is the pancreas The pancreas is a long, irregularly-shaped gland with a superficial resemblance to cottage cheese Like the hormones insulin and glucagon, some of its products are dumped into the blood as they are needed (Thus, the pancreas is an endocrine gland.) The pancreas also produces enzymes that catalyze protein digestion These enzymes are released as needed into the duodenum through a duct Thus, the pancreas is also an exocrine gland Bile produced in the liver also empties into the duodenum Ducts from the liver and gall bladder join to form the common bile duct, which enters the anterior side of the duodenum right next to the pylorus Bile emulsifies fats, and the digestion of fats does not begin until they reach the small intestine IV Interesting facts about the digestive system According to Diana Wells, 19 Fun Facts About the Digestive, May 23, 2017: Stomach growling is called borborygmic and happens all the time, but it is just louder when your Stomach is empty because there is no food to muffle it The Stomach can stretch and hold up to pounds of food at one time Enzymes in your digestive system separate food into the different nutrients that your body needs You burp to release extra air you swallow if you eat fast, drink carbonated drinks, or smoke Your body can move your food through the digestive system even while you are standing on your head It is not connected to gravity because it works with muscles V Diseases of the Accessory Organs A disease that affects the pancreas is cystic fibrosis Cystic fibrosis is an inherited disease in which the body produces abnormally thick and sticky mucous The mucus blocks the duct to the duodenum in the pancreas, preventing pancreatic enzymes from reaching it As a result, proteins and lipids cannot be digested properly People with CF may take digestive enzymes by mouth to improve their digestion However, the disease has no known cure Hepatitis is inflammation of the liver It is usually caused by a viral infection Several different viruses can cause hepatitis Some of the viruses spread through contaminated foods or beverages, and others spread through sexual contact Symptoms of hepatitis include fever, headache, vomiting, and abdominal pain Another symptom is jaundice, which is yellowing of the skin and eyes If the symptoms are mild, the disease may clear up without treatment If the symptoms are more severe, the disease may damage the liver, so it can no longer produce bile This interferes with the digestion of lipids Medications are available to treat hepatitis Some types of hepatitis can also be prevented with vaccines Figure 2: Viral hepatitis is a serious public health concern VI The importance of the digestive system Digestion is important for breaking down food into nutrients, which the body uses for energy, growth, and cell repair Food and drink must be changed into smaller molecules of nutrients before the blood absorbs them and carries them to cells throughout the body The body breaks down nutrients from food and drink into carbohydrates, protein, fats, and vitamins REFERENCE Diana Wells, 19 Fun Facts About the Digestive, May 23, 2017 Ibrahim Z, Busch J, Awwad M, et al Selected physiologic compatibilities and incompatibilities between human and porcine organ systems Xenotransplantation 2006; Cook VL, Jones Shults J, McDowell M, et al Attenuation of ischaemic injury in the equine jejunum by administering systemic lidocaine Equine Vet J 2008;40:353–357 Brandtzaeg P Molecular and cellular aspects of the secretory immunoglobulin system APMIS 1995;103:1-19 DOI: 10.1111/j.16990463.1995.tb01073 Artis D Epithelial-cell recognition of commensal bacteria and maintenance of immune homeostasis in the gut Nat Rev Immunol 2008;8:411-20 DOI: 10.1038/nri2316 Biology 104 Human Digestive System Anatomy https://www.radford.edu/~jkell/Digestive%20system_Biology%20104.pdf Surprising Facts About Digestive Health | Shop high https://qualityoflife.net/blogs/news/10-surprising-facts-about-digestive-health ... Description of the digestive organs The head and neck contain the mouth, oral cavity, and pharynx Food enters the oral cavity through the mouth, which is bounded by the lips The roof of the oral cavity... palate, the hard palate At the posterior end of the hard palate, the bone ends and the roof of the mouth becomes soft, i.e., the soft palate (The distinction in surface isn''t striking on the models,... is displayed in the hard sense of taste) The oral cavity is that part of the digestive tract from the lips to the end of the hard palate Digestion begins in the oral cavity, as digestive enzymes