IndexThe Digestive SystemThe Throat and StomachThe IntestineWorks CitedThe Digestive SystemWhen you enter the body through the brain, you come across the first component of the digestive system, the hypothalamus, a section of the brain the size of an almond. The hypothalamus controls body temperature, hunger, thirst, fatigue, and circadian cycles: a daily cycle of biological activity based on a 24-hour period and influenced by regular changes in the environment, such as the alternation of day and of the night displayed by many organisms. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay As you continue down the body, the next component of the digestive system you come to is the mouth. The main digestive components of the mouth are the teeth and salivary glands. Teeth are a mechanical digester: they break food into smaller pieces by mastication (mastication). There are three main types of teeth in the mouth: incisors, canines and molars. The incisors, the first eight teeth, four at the top and four at the bottom, cut food when you chew. The next four teeth, two upper and two lower, are the canines. The canines are used to tear and tear apart food. Other animals with canines use them to hold prey. The molars – the last twenty teeth (in an adult) or eight teeth (in a young child) – are used for chewing and grinding food. The different types of teeth amount to 32 for an adult and 20 for a small child. Along with mechanical digestion in the mouth there is chemical digestion: amylase in saliva turns starch (a polysaccharide (a carbohydrate made up of many sugar molecules stuck together) ) into simple sugars, in place. When food enters the mouth, that is, is swallowed, it is mixed with saliva secreted by different groups of glands. In addition to the numerous insignificant glands that secrete saliva, there are three main pairs of salivary glands: the parotid, submandibular, and sublingual glands. The parotid glands, the largest of the pairs, are located on the side of the face, below and in front of each ear. The rounded submandibular glands are located near the inside of the lower jaw, in front of the sternomastoid muscle (the prominent muscle of the jaw). The sublingual glands are located directly under the mucous membrane that lines the floor of the mouth under the tongue. Saliva, produced by tiny glands throughout the mouth and by the three major glands, loosens some of the chewed food and acts as a lubricant, allowing food to pass through narrow passages into the digestive system. Saliva also contains a starch-digesting enzyme called amylase (ptyalin), which initiates the process of enzymatic hydrolysis (Hightower, MD Nicholas Carr. “Salivary Glands.” Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. September 30, 2014. ) Enzymatic hydrolyzation splits starch (a polysaccharide containing many sugar molecules linked in a continuous chain) into simple sugars. Throat and stomach The esophagus, the passage from the mouth to the stomach, is about 25 centimeters (10 inches) long. The esophagus is made up of 4 layers: mucosa, submucosa, muscularis and tunica adventitia. The mucosa is made up of multiple layers of tissue containing numerous mucous glands. The submucosa is a thick thread-like layer that connects the mucosa to the muscularis. The muscularis is made up of an internal layer, in which the fibers are circular, and an external layer of fibers that run longitudinally in the esophagus. The outer layer of the esophagus, the tunica adventitia, is composed of loose fibrous tissue that connects the esophagus with other internal structures. Except during the act of swallowing,the esophagus is normally empty and its canal is essentially closed by longitudinal folds. of the mucosal and submucosal layers. The upper third of the esophagus is composed of striated (voluntary) muscles. The middle third is a mixture of striated and smooth (involuntary) muscle, while the lower third is made up of smooth muscle only. The bolus, or the chewed food now mixed with saliva and moving down the esophagus, is moved by peristalsis. Peristalsis is the contraction of the muscles of the esophagus that causes the bolus to move down the throat. The trachea connects near the middle of the esophagus. When you swallow, your brain sends a message to a muscle flap called the epiglottis. The epiglottis closes over the trachea during swallowing to keep food out of the trachea. When the bolus reaches the end of the esophageal tube, the last thing blocking the bolus' path to the stomach is the cardiac sphincter. The cardiac sphincter is a muscle that controls what goes into the stomach and what comes out of the stomach. Past the cardiac sphincter, the bolus enters the stomach. The bolus will be digested in the stomach for 3-4 hours. While food is in the stomach, mechanical digestion occurs. Peristalsis, the contraction of the muscles around the stomach, stimulates the bolus as the chemicals digest it. Chemical digestion in the stomach is caused by gastric juice consisting of the enzyme pepsin and HCl (hydrochloric acid/muriatic acid). A thin layer of mucus lines the stomach to prevent hydrochloric acid, composed of hydrogen, chlorine, and water, from burning through the stomach and causing stomach ulcers. Pepsin in the stomach is used to break down proteins. While pepsin digests proteins, hydrochloric acid also digests proteins and other things in the bolus. The stomach is shaped like a bean. There are 3 sections of the stomach: the fundus, the body and the pyloric end. The lower curve of the stomach is called the greater curvature because it is larger than the lesser curvature and equally so. At the end of the stomach is the pyloric sphincter. The pyloric sphincter, like the cardiac sphincter, is a muscle that controls what goes into the stomach and small intestine. After the bolus passes through the pyloric sphincter it is called chyme. The intestine The small intestine is made up of 3 parts: duodenum, jejunum and ileum. The first 22 centimeters of the small intestine is the duodenum. Digestive enzymes are added into the duodenum. Digestive juices added to the small intestine are: pancreatic juice - amylase (turns starches into sugar), trypsin (breaks down proteins such as pepsin), and lipase (breaks down fats) - and bile. Pancreatic juice – amylase, trypsin and lipase – is produced in the pancreas. Pancreatic juice aids in digestion and absorption of nutrients in the small intestine. Enzymes in pancreatic juice help break down carbohydrates, proteins, and lipids (organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents) in the chyme. The pancreas is made up of 3 sections: the head, body and tail. Although the pancreas adds digestive juices to the small intestine, food does not actually enter the pancreas. The pancreas is a digestive aide (an organ that contributes to digestion but never contains food inside it). Bile is produced in the liver. The liver is a digestive aide like the pancreas. After the liver produces bile, it sends it to the gallbladder through the liver ducts. Once in the gallbladder, the bile remains until it is needed. In case the bile is made up of too much cholesterol and remains stored for too long, it can cause gallstones. Gallstones are the excessive buildup of cholesterol in the gallbladder that causes a stone-like ball to form. WhenIf you pass a gallstone you may experience a lot of pain. Now let's get back to the more important things. When needed, the gallbladder sends bile into the cystic duct, a tube that connects the gallbladder to the bile duct. As the bile travels down the bile duct, it discharges into the ampulla, the tube that connects the pancreas to the small intestine. When digestive enzymes reach the small intestine they emulsify – mix – with chyme to form a nearly black liquid. Along with the pancreatic juice is the intestinal juice. Intestinal juice contains erepsin, lipase (breaks down fats), lactase (catalyzes the hydrolysis of lactose into glucose and galactose), enterokinase, amylase (turns starches into sugar), and mucus. Mechanical digestion also occurs in the small intestine. While pepsin, trypsin, and lipase in pancreatic juice and erepsin, lipase, lactase, enterokinase, and amylase in intestinal juice chemically break down chyme, bile, a liquid mechanical digester, breaks down the “pieces ” of fat in the chyme into smaller pieces. Peristalsis is another form of mechanical digestion in the small intestine. Although peristalsis is usually used to move food through the digestive system, the small intestine, like the stomach, also uses peristalsis to squeeze food. The next 200 centimeters of the small intestine is the jejunum. The jejunum is the part of the small intestine where pancreatic juice, the chemical digestion in the small intestine, and bile, the mechanical digester in the small intestine, digest chyme. Pepsin, trypsin and lipase present in pancreatic juice are chemical digesters. Peristalsis is again present in a digestive organ. Along the way there are tiny structures called villi. The villi increase the surface area of ​​the small intestine 600-fold and absorb nutrients from the chyme. There are so many villi within the small intestine that without the villi the surface area of ​​the small intestine would be 600 times smaller. The last 350 centimeters of the small intestine is the ileum. In the ileum, the villi absorb nutrients from the chyme. The chyme has now reached the end of the small intestine and reaches the ileocecal sphincter. The ileocecal sphincter allows what enters the large intestine. The large intestine is made up of 8 parts: cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anus. The first part of the large intestine is the cecum. When food passes through the ileocecal sphincter it reaches the cecum. The cecum is a bowl-shaped structure in the large intestine. Connected to the cecum is the appendix. The appendix is ​​a worm-like tube that stores a little of each type of bacteria in the large intestine in case the bacteria are killed in the intestine. The appendix sometimes swells and when this happens it causes a lot of pain. If the appendix swells, most people undergo an appendectomy. If left for too long, the appendix can rupture and all the bacteria stored in the appendix are secreted into the body cavity at which point you have a great chance of dying. Please note: this is just a sample. Get a custom sample. article now by our expert writers. Get a Custom Essay The next parts of the large intestine are the ascending colon, transverse colon, descending colon, and sigmoid colon. The ascending colon absorbs and recycles water and vitamins B and K. The transverse colon also absorbs and recycles water and vitamins. The descending colon stores feces, or poop, before it enters the rectum. The sigmoid colon pushes stool into the rectum. The rectum is said to be the last part of the large intestine. The rectum serves as the final storage unit for feces. Between the rectum and the anus is the anal canal. The anal canal is different from the rectum only.