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A lot of people think that this food is now digested into products that can be absorbed into the bloodstream, but that's not the case at all, because full digestion of the food still requires a lot more work. Examples Cases Gathering Blue: What best describes you? Please check this section from time to time. Password confirm does not match password. Patrick's Day Activities St.
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Today we are going to begin talking about the skeletal system. We are going to focus on the functions of the skeletal system.
While I am handing these papers out, I want you to think why your bones are an important part of your body. If you have questions or comments, please raise your hand and wait to be called on.
Ok now that we have looked over the questions, please set aside that sheet and turn it face down in the corner of your desk. I am going to hand out an outline that I want you to follow along. These will be your notes for the day, and we are going to fill it out together as we go. Purpose of the Skeletal System: The skeleton provides the framework for the body. Bones provide the basic shape and structure for the body.
The bones are like the beams inside of a building, and all of our organs, muscles and skin are organized around the bones, just like the walls of a building.
The skeleton protects organs in the body. Bones can cover and protect many of out major organs. They are like an armor that protects our insides.
Can anyone think of any examples? Inside of the long bones in our bodies we will talk more about the different types of bones later on , there is a cavity that is filled with a substance called Bone Marrow. In this tissue, new blood cells are produced, and damaged blood cells are repaired. We are going to talk more about bone marrow in the next lesson. The bones are the levers that help the body move in different directions and in different ways. Here is a question for you all: Do bones move by themselves when we walk, talk or move around?
Or are they controlled by something else? What makes them move? Muscles move bones by contracting, which pulls the bone, causing us to move around. Can someone describe what a mineral is to the class? It is a substance that the body needs to carry out all of our bodily functions like thinking, breathing and moving around. One of the minerals that the body needs is calcium.
One major component of gastric juice is hydrochloric acid , which you may remember is a very strong acid. It can be represented by the abbreviation HCl. Because of its acidic properties, HCl kills most bacteria found in food. It also dissolves most types of tissues that we eat into a liquid form that is much more accessible to digestive enzymes. Unfortunately, HCl inactivates amylase, which leaves the polysaccharides only partially digested.
Speaking of digestive enzymes, another major component of gastric juice is pepsin. Pepsin is a digestive enzyme that breaks proteins down into smaller peptides. You can remember the function of pepsin if you remember that pepsin breaks proteins into peptides.
But this function of pepsin raises a fundamental question: The answer is that the cell makes an inactive form of pepsin named pepsinogen , which is several amino acids longer than active pepsin. The extra amino acids block the active site of pepsin, causing it to be inactive inside the cell where it can damage other proteins. However, the HCl in the gastric juice removes these amino acids and converts the inactive pepsinogen into active pepsin once it is out of the cell and inside the stomach.
To keep them from digesting components of the secretory cells, most digestive enzymes are produced in an inactive form known as a zymogen an inactive precursor of an enzyme which requires a change to be activated. In this case, pepsinogen is a zymogen that is activated by HCl and turned into active pepsin. Get access risk-free for 30 days, just create an account. So why doesn't the pepsin and hydrochloric acid digest the epithelial cells that line the stomach?
It turns out that most of the epithelial cells of the stomach secrete large amounts of mucus, which forms a barrier to protect the cells against the acid and pepsin. In addition, the stomach isn't always filled with gastric juice. Between meals, the stomach is empty and pretty much inactive. However, when a person sees, smells or otherwise anticipates eating food, the brain sends a signal to the stomach to start preparing for a meal.
As a result of this signal, the epithelial cells secrete a small amount of HCl into the stomach. The smooth muscles of the stomach are also activated and start churning the stomach at a low rate. This churning of the stomach, without food in it, is what causes your stomach to growl when it's getting close to meal time.
When food enters the stomach, it activates the full response. The epithelial cells secrete lots of gastric juice and the smooth muscles of the stomach are fully activated - causing the stomach to churn and thoroughly mix the food and gastric juice until it is liquefied.
The stomach then releases its liquefied contents into the small intestine a little at a time through the pyloric sphincter the muscular valve at the bottom of the stomach that controls the flow of partially digested food into the small intestine.
It takes about 2 to 6 hours for the stomach to completely empty its contents into the small intestine. During that time, the churning motion and release of gastric juice by the stomach is ramped down until the stomach is empty and - essentially - powered-down.
That is, until it receives the next signal from the brain to start powering-up again. As soon as you put a piece of food in your mouth, your body starts the digestive process. Salivary glands release saliva that contains amylase , a digestive enzyme found in saliva that breaks large polysaccharides into smaller polysaccharides.
Chewing begins the physical process of breaking large chunks of food into smaller pieces. The food is swallowed and directed by the epiglottis down the esophagus the tube that serves as a passage for food from the pharynx to the stomach.
The epithelial cells of the stomach secrete three major products: Pepsinogen is a zymogen , which is an inactive precursor of an enzyme that requires a change to be activated. HCl converts it to the active enzyme pepsin , which is a digestive enzyme that breaks proteins down into smaller peptides.
Together, pepsin and hydrochloric acid are the major components of gastric juice, which essentially liquefies food and continues to break it down into smaller components.
However, when a person sees, smells, or otherwise anticipates eating food, the brain sends a signal to the stomach to start preparing for a meal.
As a result of this signal, the epithelial cells secrete a small amount of hydrochloric acid into the stomach. Smooth muscle is also activated and starts churning the stomach at a low rate. When food actually enters the stomach, the epithelial cells secrete lots of gastric juice and the smooth muscle of the stomach thoroughly mixes the food and gastric juice until it is liquefied.
The stomach empties, and powers-down until it receives the next signal to prepare for a meal. To unlock this lesson you must be a Study. Did you know… We have over college courses that prepare you to earn credit by exam that is accepted by over 1, colleges and universities.
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By creating an account, you agree to Study. Explore over 4, video courses. Find a degree that fits your goals. The Upper Gastrointestinal Tract Did you know that there are digestive enzymes in your saliva? As soon as you put a piece of food in your mouth, the digestive process begins. Join us with this first of two lessons about the human digestive system, where we'll follow food through the upper gastrointestinal tract from the mouth through the stomach.
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Register to view this lesson Are you a student or a teacher? I am a student I am a teacher. What teachers are saying about Study. The Lower Gastrointestinal Tract. Are you still watching? Your next lesson will play in 10 seconds. Add to Add to Add to. Want to watch this again later? Anatomy and Physiology of the Mouth. Functions of the Lymphatic System.
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Did you know that there are digestive enzymes in your saliva? Upper Gastrointestinal Tract All is calm in the rainforest. The Mouth The digestive process begins when amylase in saliva starts to break down food As Timmy chewed the butterfly and physically broke it down into smaller pieces, his salivary glands went to work, releasing saliva containing amylase - a digestive enzyme that breaks large polysaccharides into smaller ones.
The Throat The tongue then forms the chewed-up and saliva-soaked food into a ball and directs it to the back of the mouth. The Stomach The stomach is a fairly large organ with an elastic wall. Epithelial cells lining the stomach wall secrete gastric juice One major component of gastric juice is hydrochloric acid , which you may remember is a very strong acid.
Pepsin Speaking of digestive enzymes, another major component of gastric juice is pepsin. Try it risk-free No obligation, cancel anytime. Want to learn more? Select a subject to preview related courses: When food is seen or smelled, the brain sends a signal to the stomach When food enters the stomach, it activates the full response.
Lesson Summary So, let's review. Unlock Your Education See for yourself why 30 million people use Study. Become a Member Already a member?