Structures and functions of the human digestive system
This book provided a majority of the information my daughter needed for her report. Guts tells us how the body digest food starting with our teeth and ending with the food beining made into waste. Board the battle bus and find out! I think your customers have been incredibly patient! I regularly download clips from BoardGameGeek, they used to download as flvs, now they download as MP4s but the catch is that no player can play them.
Mouth and oral cavity
The soft palate is composed of a strong, thin, fibrous sheet, the palatine aponeurosis, and the glossopalatine and pharyngopalatine muscles. A small projection called the uvula hangs free from the posterior of the soft palate. The floor of the mouth can be seen only when the tongue is raised. In the midline is a prominent, elevated fold of mucous membrane frenulum linguae that binds each lip to the gums, and on each side of this is a slight fold called a sublingual papilla , from which the ducts of the submandibular salivary glands open.
Running outward and backward from each sublingual papilla is a ridge the plica sublingualis that marks the upper edge of the sublingual under the tongue salivary gland and onto which most of the ducts of that gland open.
The gums consist of mucous membranes connected by thick fibrous tissue to the membrane surrounding the bones of the jaw. The gum membrane rises to form a collar around the base of the crown exposed portion of each tooth.
Rich in blood vessels, the gum tissues receive branches from the alveolar arteries; these vessels, called alveolar because of their relationship to the alveoli dentales, or tooth sockets, also supply the teeth and the spongy bone of the upper and lower jaws, in which the teeth are lodged.
We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Your contribution may be further edited by our staff, and its publication is subject to our final approval. Unfortunately, our editorial approach may not be able to accommodate all contributions.
Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Read More on This Topic. Page 1 of Next page The teeth. Learn More in these related Britannica articles: As the embryo folds off, the endoderm is rolled in as the foregut and hindgut.
Continued growth progressively closes both the midbody and the midgut. The esophagus remains as a simple, straight tube. The stomach grows faster on its dorsal side, thereby forming…. Loss of teeth, which is often seen in elderly people, is more apt to be the result of long-term neglect than a result of aging itself. The loss of teeth and incidence of oral disease increase with age, but, as programs of water…. In either event, pregnancy complicates their problems because the gastrointestinal disturbances that often….
Capybara, rabbits, hamsters and other related species do not have a complex digestive system as do, for example, ruminants. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft faecal pellets of partially digested food are excreted and generally consumed immediately.
They also produce normal droppings, which are not eaten. Young elephants, pandas, koalas, and hippos eat the faeces of their mother, probably to obtain the bacteria required to properly digest vegetation. When they are born, their intestines do not contain these bacteria they are completely sterile.
Without them, they would be unable to get any nutritional value from many plant components. An earthworm 's digestive system consists of a mouth , pharynx , esophagus , crop , gizzard , and intestine. The mouth is surrounded by strong lips, which act like a hand to grab pieces of dead grass, leaves, and weeds, with bits of soil to help chew.
The lips break the food down into smaller pieces. In the pharynx, the food is lubricated by mucus secretions for easier passage. The esophagus adds calcium carbonate to neutralize the acids formed by food matter decay. Temporary storage occurs in the crop where food and calcium carbonate are mixed.
The powerful muscles of the gizzard churn and mix the mass of food and dirt. When the churning is complete, the glands in the walls of the gizzard add enzymes to the thick paste, which helps chemically breakdown the organic matter. By peristalsis , the mixture is sent to the intestine where friendly bacteria continue chemical breakdown.
This releases carbohydrates, protein, fat, and various vitamins and minerals for absorption into the body. In most vertebrates , digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing. Digestion is separated into four steps:.
Underlying the process is muscle movement throughout the system through swallowing and peristalsis. Each step in digestion requires energy, and thus imposes an "overhead charge" on the energy made available from absorbed substances. Differences in that overhead cost are important influences on lifestyle, behavior, and even physical structures.
Examples may be seen in humans, who differ considerably from other hominids lack of hair, smaller jaws and musculature, different dentition, length of intestines, cooking, etc.
The major part of digestion takes place in the small intestine. The large intestine primarily serves as a site for fermentation of indigestible matter by gut bacteria and for resorption of water from digests before excretion.
In mammals , preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach. Mechanical and chemical digestion begin in the mouth where food is chewed , and mixed with saliva to begin enzymatic processing of starches.
The stomach continues to break food down mechanically and chemically through churning and mixing with both acids and enzymes. Absorption occurs in the stomach and gastrointestinal tract , and the process finishes with defecation. The human gastrointestinal tract is around 9 meters long. Food digestion physiology varies between individuals and upon other factors such as the characteristics of the food and size of the meal, and the process of digestion normally takes between 24 and 72 hours. Digestion begins in the mouth with the secretion of saliva and its digestive enzymes.
Food is formed into a bolus by the mechanical mastication and swallowed into the esophagus from where it enters the stomach through the action of peristalsis. Gastric juice contains hydrochloric acid and pepsin which would damage the walls of the stomach and mucus is secreted for protection. In the stomach further release of enzymes break down the food further and this is combined with the churning action of the stomach. The partially digested food enters the duodenum as a thick semi-liquid chyme.
In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile , pancreatic juice and intestinal juice. The intestinal walls are lined with villi , and their epithelial cells is covered with numerous microvilli to improve the absorption of nutrients by increasing the surface area of the intestine.
In the large intestine the passage of food is slower to enable fermentation by the gut flora to take place. Here water is absorbed and waste material stored as feces to be removed by defecation via the anal canal and anus.
Different phases of digestion take place including: The cephalic phase occurs at the sight, thought and smell of food, which stimulate the cerebral cortex. Taste and smell stimuli are sent to the hypothalamus and medulla oblongata.
After this it is routed through the vagus nerve and release of acetylcholine. Acidity in the stomach is not buffered by food at this point and thus acts to inhibit parietal secretes acid and G cell secretes gastrin activity via D cell secretion of somatostatin.
The gastric phase takes 3 to 4 hours. It is stimulated by distension of the stomach, presence of food in stomach and decrease in pH. Distention activates long and myenteric reflexes. This activates the release of acetylcholine , which stimulates the release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach.
Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin , which in turn stimulates parietal cells to secrete gastric acid. Gastric acid is about 0. Acid release is also triggered by acetylcholine and histamine. The intestinal phase has two parts, the excitatory and the inhibitory. Partially digested food fills the duodenum. This triggers intestinal gastrin to be released.
Enterogastric reflex inhibits vagal nuclei, activating sympathetic fibers causing the pyloric sphincter to tighten to prevent more food from entering, and inhibits local reflexes. Protein digestion occurs in the stomach and duodenum in which 3 main enzymes, pepsin secreted by the stomach and trypsin and chymotrypsin secreted by the pancreas, break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids.
The digestive enzymes however are mostly secreted as their inactive precursors, the zymogens. For example, trypsin is secreted by pancreas in the form of trypsinogen , which is activated in the duodenum by enterokinase to form trypsin.
Trypsin then cleaves proteins to smaller polypeptides. Digestion of some fats can begin in the mouth where lingual lipase breaks down some short chain lipids into diglycerides. However fats are mainly digested in the small intestine. In humans, dietary starches are composed of glucose units arranged in long chains called amylose, a polysaccharide. During digestion, bonds between glucose molecules are broken by salivary and pancreatic amylase , resulting in progressively smaller chains of glucose.
This results in simple sugars glucose and maltose 2 glucose molecules that can be absorbed by the small intestine. Lactase is an enzyme that breaks down the disaccharide lactose to its component parts, glucose and galactose.
Glucose and galactose can be absorbed by the small intestine. Approximately 65 percent of the adult population produce only small amounts of lactase and are unable to eat unfermented milk-based foods.
This is commonly known as lactose intolerance. Lactose intolerance varies widely by ethnic heritage; more than 90 percent of peoples of east Asian descent are lactose intolerant, in contrast to about 5 percent of people of northern European descent. Sucrase is an enzyme that breaks down the disaccharide sucrose , commonly known as table sugar, cane sugar, or beet sugar. As we become more reliant on these technologies, the MP4 format helps enable nearly everyone to be both a creator and a consumer of video applications.
MP4 files also permit faster, more efficient distribution over the Internet. Just about any content you can think of is available online. RealPlayer Cloud offers a one-click solution to downloading MP4 videos.
A word of caution: Be skeptical of websites offering free movie downloads, particularly of recent films. The major movie studios need to market their product, so they provide trailers, along with interviews and other background material to a number of websites to help sell their films. ComingSoon, Fandango, Metacafe, and Traileraddict are just a few that offer access to watching and downloading MP4 movie trailers. Once you have the free application, double-clicking on the thumbnail in the RealPlayer Cloud Library opens the Now Playing window and plays the video in its native format and resolution.
More and more that is MP4. Want to access your movie library from any device? Stream your downloaded mp4 video in RealPlayer with RealTimes.
I downloaded the latest RealPlayer release around June 15th and most. I had no problem with the previous version of RealPlayer. Hmmm… Today is June 12th.
Do you mean Version 15? Apparently there have been some reports of difficulties with MP4 files. Typically, it runs fine though. Now my real player cannot dowload the file as. RP should download and play p as p. Try the usual routine of uninstalling all your RP apps, then download and install fresh versions. I just do as you suggest but RP still download the p and p as. First time i got this laptop and installed RP it can download the file as. How should i do?
That said, FLV is a file format container that can run H. It would be unusual to have the choice of downloading a specific format. There certainly are sites where you can choose a format and even the codec, but most sites stick to a format, offering different resolution qualities. What site are you downloading from? Is there something wrong with the FLV version of the video? Look for a greatly improved codec, H.
Also, check out Vimeo and YouTube for special 4k 4 times more resolution than p content using H. I have RP version Sould I get a mp4 to flv converter?
If so, which one is best? Just a shot, but download and install QuickTime for Windows. Let me know if it works. I have RP v Download and install QuickTime for Windows. Go ahead and update RealPlayer 15 to the free version According to the software I have the latest version. When I moved the cursor over the video area, no option popped up to start download. Do I need to get rid of pop-up blocker? Also, assuming I get it to work, can I queue multiple videos to download after the present one is done downloading?
There are known problems with Chrome, which are being worked on. Try doing a clean REinstall of RealPlayer. Be sure to UNinstall all RealPlayer applications you may have on your machine. Download and install a fresh version of RP Hopefully, that will resolve the download issue. Yes, you can download multiple videos. Do this for as many videos as you want. The downloads take place simultaneously, depending on the speed of the Internet connection and your computer.
Plus also handles the H. These prompts to upgrade seem to happen every so often. Then, download and install a fresh version of RealPlayer 16 Plus.
Let us know how things go. Anyway as you suggested I uninstall RP and turnoff and restart my laptop and then I downloaded the latest version of RP but still not playing mp4 format. What else do you suggest to do? Please let me know I have very important videos and really need them. There have been some problems with comments and responses being properly displayed.
The techs are working on it. That should both fix your MP4 playback problems, plus give you advanced conversion capabilities.
This has been an ongoing problem with RealPlayers users being confused about MP4 playback and conversion capabilities. Hi, thanks for the post. Videos downloaded from an HTML5 site will have the file extension. Download codec from this link: Extract the contents of webmdshow This is an install package and will run once downloaded.
If file does not run automatically, double-click it and the file will start installing. I spent a couple of days to install and uninstall Real Player many times without success. I saw your posting and hope that you can help. I installed Real Player 16 free version for my Windows 8 64 bit laptop and when I click on a MP4 file to play, I only get a pop up to tell me to upgrade to Plus.
I clicked close and then I am back to the original library list. This is in a loop that no matter how many times I tried I am just getting the pop up. I contacted support and was told to install Quick Time and it will resolved the problem.
Sorry for the trouble, please make sure that the RealPlayer plug-in is enabled in your browser by following this link: I just downloaded the new version of Real Player How can i achieve what i want ie to play the videos in my realplayer or windows media and convert to music only for use on making my own videos.
Thanking you in advance. Sorry for the inconvenience, our technical team is aware of this issue and currently working on it, however as a workaround please try this step. Try installing QuickTime player by following this link: Please let us know your progress, and if you have additional questions, email us at help real.
However they do not play in there either. As I have mentioned already our technical team is aware of this issue and currently working on a global fix soon. Hi, I have noticed exactly the same problem asYdaltak. With QT and RP there is only a black screen and no sound even though the progress bar indicates the the video is played and with MP there is an error message saying that Windows Media Player cannot play the file.
I also have another observation that may not be directly related with Real team, but maybe they can provide some comments on that too. So the question is that has YouTube recently changed the format of all videos at their servers or are there some changes implemented the latest version of RealDownloader that prevent storing the videos in FLV format? Many thanks for you assistance! Selecting the first box to have the download this video button appear on videos does not make the button appear.
I have switched off and restarted and still no luck. This worked last week and does not work since installing the latest Adobe flash player update yesterday. In managing add-ons, Flash Player v Please send an email to help real.
Running windows 7 home premium 64 bit on an HP machine. Including those shown on the RP main library screen. They all work just fine in winamp and VLC and a couple of other players as well as windows live movie maker, but not windows media player. I have installed various codec packages including k-lite, which reported a couple of broken ones. Did a system restore and a few other things and still no audio. So what is the fix? I have gone through the uninstall and reinstall process a few times with the latest version of Realplayer.
I have downloaded 4 files now from youtube mp4 and they are all the correct size. Disable Shockwave Flash Object 3. Go through the process of updating Adobe Flash Player 7. Now files should get downloaded in. After spending numerous days and hours am completely out of ideas what happened with Real Player download functionality. Not so far it started download video files from sites what i used for year, in MP4 format without sound at all.
Before, it was manage to download usually in FLV format. Not anymore… Am running Windows 7 64 bit and all possible solutions was try already. Than i find same result with many other web sites what i used to download video clips with Real Player.
I install and reinstall numerous times both v. Also used standalone dowloader. Everything enabled in Manage Add-on and Active X filtering turned off. As i mention that , it happened in last cpl weeks after upgrading to last Adobe Flash and Real Player itself.
I was able using alternative software called YTD , to download same video on top of my post with much better quality and Audio 0: AAC at Kbps 2 channels, Plz need help to clarify that. If it temporary problem and gonna be fixed by devs or permanent? Reason for that , because i cannot use YTD at some sites.
Thank you in advance. Our technical team is aware of this issue and working on it. This issue will be resolved at the earliest. Okay not to sound rude, but how long is your technical team going to take to fix this issue? I have recently download the newest version of real player and it wont play any mp4 videos. What do I do? It also wont sync the videos I added to my computer recently into real player section video. I have to drag my video in there. However, try the workaround steps from this link: The solution for downloading and playing mp4-files: Now flv-files will be downloaded und I can play them.
Am I the only one this solution does not work for?!! Same as everyone I was happy with Realplayer before , did everything I wanted. This Is so annoying, so i hope the tech team get this fixed soon. Our technical team is aware of this issue and currently working on it. However, try the troubleshooting steps provided in this link: If there is anything else we can help with, please send an email to help real.
Sorry for the inconvenience, this is due to changes made at YouTube and we are working with YouTube to resolve the issue. I want to download the videos in. However, here are some steps we think might resolve the issue. Open Internet Explorer 2. Click on Tools 3. Go to Manage Add-ons 4. Disable Shockwave Flash Object 5. Now files should get downloaded and are playable.
Sorry for the inconvenience, please be informed that we have already tested these steps with few customers and it worked on their computers. Guys, by now you should be well aware that RealPlayer Downloader 16 has a serious bug in it.
I count numerous repeats of the same issue in the thread above. How about following prudent IT practice and rolling back to the earlier versions that did work, RP Downloader 15 or earlier, until you have a fix and can either re-release version 16 or jump to version I having problems using Leawo converter.
Can someone help me in this matter please. Well having spent money on Real Player and also upgraded I too join the long queue of people unable to download and convert Mp4 videos from You Tube. I have done everything that has been suggested in mails over the last months and still unable to sucessfully download on any of my three computers.
When oh when will this be solved? Not sure that this is a RP problem, and not a website problem. However, try few work around steps provided in this link to fix this issue: Hi all, The latest workaround seems to work at least for me.
If you enable the Shockwave add-on again, the download process fails and there seems to be no other option to fix this than reinstalling the Flash Player. This is due to changes made at YouTube and we are working with YouTube to resolve the issue.
However, try few work around steps for Internet Explorer to fix the issue:. Go to Manage Add-ons. Disable Shockwave Flash Object. We have a reported issue were several customers are experiencing the same issue which you are facing. Our support team is aware of this and working on high priority to resolve it at the earliest. Once it is fixed, you will be notified by our support team.
However, try few work around steps provided in this link to fix the issue:. My realplayer only downloads in mp4 format instead of the FLV. How do we get back the older version so we can see what we have downloaded. Can you help with the sound part.
However, try few workaround steps provided in this link to fix the issue: What is the format of the downloaded video? Do you get any error message while playing the video in RealPlayer? Does it happen to all the videos? It does seem the problem is with the Flashplayer.