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▶ Digestion in Human Beings 3D CBSE Class 7 Science (www.iDaaLearning.com) - YouTube

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▶ Digestion in Human Beings 3D CBSE Class 7 Science (www.iDaaLearning.com) - YouTube

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Digestion in Human Beings 3D CBSE Class 7 Science (www.iDaaLearning.com)

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BBC - GCSE Bitesize: The digestive system

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BBC - GCSE Bitesize: The digestive system

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BBC - GCSE Bitesize: The digestive system

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A secondary school revision resource for AQA GCSE Additional Science about tissues, organs and organ systems

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The Digestion Process: Facts About Digestive Problems

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The Digestion Process: Facts About Digestive Problems

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Digestion definition

The energy required for all the processes and activities that take place in our bodies is derived from the foods we ingest. The digestive system allows us to utilize food from such diverse sources as meat from an animal and the roots of a plant, and utilize them as an energy source. Whether it is the ability to coordinate the chewing of the food without injuring our tongue and lips or the propulsion of the food from the stomach into the duodenum while releasing the appropriate enzymes, our digestive system allows us to manage the process without much thought and often while performing other tasks.

What is digestion?

The process of digestion is a fascinating and complex one that takes the food we place in our mouth and turns it into energy and waste products. This process takes place in the gastrointestinal tract, a long, connected, tubular structure that starts with the mouth and ends with the anus. The food is propelled forward within the system, altered by enzymes and hormones into usable particles and absorbed along the way. Other organs that support the digestive process are the liver, gallbladder, and pancreas. The time it takes for food to travel from entering the mouth to be excreted as waste is around 30 to 40 hours.

The mouth

The mouth is the entry point for food, but the digestive system often gets ready before the first piece of food even enters our mouth. Saliva is released by the salivary glands into our oral cavity when we smell food. Once the food enters the mouth, chewing (mastication) breaks food into smaller particles that can be more easily attacked by the enzymes in saliva. Our teeth can perform a cutting as well as grinding function to accomplish this task. The tongue assists in mixing the food with the saliva and then the tongue and roof of the mouth (soft palate) help move the food along to the pharynx and esophagus.

The pharynx and esophagus

The pharynx (throat) is the transition area from the mouth to the esophagus. From the pharynx there are two paths that the food bolus can take; 1) the wrong path, which is down the windpipe into the lungs, or 2) the correct path into the esophagus and then the stomach. The act of swallowing is a complex process that closes the windpipe (to protect our lungs) and moves food into the esophagus. This process is mostly automatic (reflex) but it is also partially under our direct control.

Once it enters the esophagus, food is moved down the esophagus and into our stomach. The esophagus is a muscular tube that contracts in a synchronized fashion (peristalsis) to move food down towards the stomach. While the muscles behind the food product contract, the muscles ahead of the food relax, causing the forward propulsion of the food. Peristalsis is the main mechanism by which food moves through our digestive system.

Once the food approaches the stomach, a muscular valve (the lower esophageal sphincter) relaxes and lets the food pass into the stomach. This sphincter has the important function of closing the stomach so no food or stomach acid reenters the esophagus (and therefore avoiding heartburn or regurgitation).

The stomach and small intestine

From glands that line the stomach, acid and enzymes are secreted that continue the breakdown process of the food. The stomach muscles further mix the food. At the end of this process, the food you placed in your mouth has been transformed to a thick creamy fluid called chyme.

This thick fluid is then pushed into the duodenum (the first part of the small intestine). With the help of enzymes from the pancreas and bile from the liver, further breakdown of the food occurs in the small intestine.

The small intestine has three segments. The first segment is the duodenum where further breakdown of the food takes place. The next two parts of the small intestine (jejunum and ileum) are mostly responsible for the absorption of nutrients from the processed food into the bloodstream through the walls of the intestine.

After the small intestine, the leftover waste leaves the upper gastrointestinal tract (upper GI tract) which is made up of everything above the large intestine, and moves into the large intestine or colon (the beginning of the lower GI tract).

The colon, rectum, and anus

The role of the lower GI tract is to solidify the waste product (by absorbing water), store the waste product until it can be evacuated (going to the bathroom) and help with the evacuation process.

The large intestine (colon) has four parts:

1. ascending colon,

2. transverse colon,

3. descending colon and

4. sigmoid colon.

All together the colon is approximately 7 feet long and connects to the rectum. Here as in most other parts of the GI system, the waste product is moved along by peristalsis. As the waste product passes through the colon, water is absorbed and stool is formed.

The stool from the colon is stored in the rectum. The anal sphincter provides the control over releasing stool or holding it. Once stool arrives in the rectum, a feedback to the brain makes the person aware of the need for a bowel movement. Voluntary control over the anal sphincter lets us hold the stool until we go to the toilet.

Three accessory digestive organs (pancreas, liver, gallbladder)

Three other organs are instrumental in the digestive process.

1. Pancreas: Although the pancreas is mostly known for its blood sugar regulatory function with the production of insulin (as part of the endocrine system -- he insulin goesdirectly from the gland into the bloodstream), it is the main producer of digestive enzymes as part of the exocrine system (the enzymes produced by the gland pass through a duct into the intestines). These enzymes are released into the duodenum and help with the digestion of fats, proteins, and carbohydrates..

2. Liver: The liver produces bile for fat digestion and elimination. In addition, nutrients are stored in the liver, and toxins and chemicals are filtered by liver.

3. Gallbladder: Bile is stored and released from the gallbladder. When fatty food enters the duodenum, the gallbladder contracts and releases bile.

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Medically Reviewed on 9/12/2016

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REFERENCE:

"Digestive System." Stanford Health Library.

Complete List

Top The Digestion Process (Organs and Functions) Related Articles

Anal Fissure

An anal fissure is a small tear or cut in the skin lining of the anus. Pain and/or rectal bleeding during bowel movements are common symptoms of anal fissures. Treatment involves:

increasing liquid intake,

using stool softeners,

prescription medications, and

surgery.

Appendicitis

Appendicitis is an inflammation of the appendix. Appendicitis often causes sings and symptoms such as abdominal pain in the lower right quadrant, nausea, vomiting, abdominal tenderness, fever, and loss of appetite.

Delay in surgery can result in appendix rupture with potentially serious complications.

Cirrhosis

Cirrhosis of the liver refers to a disease in which normal liver cells are replaced by scar tissue caused by alcohol and viral hepatitis B and C. This disease leads to abnormalities in the liver's ability to handle toxins and blood flow, causing:

internal bleeding,

kidney failure,

mental confusion,

coma,

body fluid accumulation, and

frequent infections.

Symptoms include yellowing of the skin, itching, and fatigue.

Clostridium Difficile Colitis

Clostridium difficile (C. difficile) is a bacterium, and is one of the most common causes of infection of the colon. C. difficile spores are found frequently in hospitals, nursing homes, extended care facilities, and nurseries for newborn infants. They can be found:

on bedpans,

furniture,

toilet seats,

linens,

telephones,

stethoscopes,

fingernails,

rings,

floors,

infants'

rooms, and

diaper pails.

They even can be carried by pets. Antibiotic-associated (C. difficile) colitis is an infection of the colon caused by C. difficile that occurs primarily among individuals who have been using antibiotics. Treatment for C. difficile colitis includes:

hydration,

replenishment of electrolyte deficiencies,

discontinuing the antibiotic that caused the colitis, and

using antibiotics to eradicate the C. difficile bacterium.

Endoscopy

Endoscopy is a broad term used to described examining the inside of the body using an lighted, flexible instrument called an endoscope. Endoscopy procedure is performed on a patient to examine the esophagus, stomach, and duodenum; and look for causes of symptoms such as:

abdominal pain,

nausea,

vomiting,

difficulty swallowing, or

intestinal bleeding.

Stomach Pain Quiz: Nausea & Other Causes

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Read more: Stomach Pain Quiz: Nausea & Other Causes

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the digestion process organs and functions

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The Human Digestive System: Functions, Definition, Organs

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What is the function of the digestive system? Read about the human digestive system and its functions and organs. The mouth, stomach, intestines, gallbladder, pancreas and more play important rolls in digesting food and eliminating waste. Learn more facts about digestion here.

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Your Digestive System and How It Works | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

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Your Digestive System and How It Works | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

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National Institute of Diabetes and Digestive and Kidney Diseases

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What is the digestive system?

The digestive system is made up of the gastrointestinal tract-also called the GI tract or digestive tract-and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus. The liver, pancreas, and gallbladder are the solid organs of the digestive system.

The small intestine has three parts. The first part is called the duodenum. The jejunum is in the middle and the ileum is at the end. The large intestine includes the appendix, cecum, colon, and rectum. The appendix is a finger-shaped pouch attached to the cecum. The cecum is the first part of the large intestine. The colon is next. The rectum is the end of the large intestine.

The digestive system

Bacteria in your GI tract, also called gut flora or microbiome, help with digestion. Parts of your nervous and circulatory systems also help. Working together, nerves, hormones, bacteria, blood, and the organs of your digestive system digest the foods and liquids you eat or drink each day.

Why is digestion important?

Digestion is important because your body needs nutrients from food and drink to work properly and stay healthy. Proteins, fats, carbohydrates, vitamins, minerals, and water are nutrients. Your digestive system breaks nutrients into parts small enough for your body to absorb and use for energy, growth, and cell repair.

Proteins break into amino acids

Fats break into fatty acids and glycerol

Carbohydrates break into simple sugars

MyPlate offers ideas and tips to help you meet your individual health needs.

Your digestive system breaks nutrients into parts that are small enough for your body to absorb.

How does my digestive system work?

Each part of your digestive system helps to move food and liquid through your GI tract, break food and liquid into smaller parts, or both. Once foods are broken into small enough parts, your body can absorb and move the nutrients to where they are needed. Your large intestine absorbs water, and the waste products of digestion become stool. Nerves and hormones help control the digestive process.

The digestive process

How does food move through my GI tract?

Food moves through your GI tract by a process called peristalsis. The large, hollow organs of your GI tract contain a layer of muscle that enables their walls to move. The movement pushes food and liquid through your GI tract and mixes the contents within each organ. The muscle behind the food contracts and squeezes the food forward, while the muscle in front of the food relaxes to allow the food to move.

The digestive process starts when you put food in your mouth.

Mouth. Food starts to move through your GI tract when you eat. When you swallow, your tongue pushes the food into your throat. A small flap of tissue, called the epiglottis, folds over your windpipe to prevent choking and the food passes into your esophagus.

Esophagus. Once you begin swallowing, the process becomes automatic. Your brain signals the muscles of the esophagus and peristalsis begins.

Lower esophageal sphincter. When food reaches the end of your esophagus, a ringlike muscle-called the lower esophageal sphincter -relaxes and lets food pass into your stomach. This sphincter usually stays closed to keep what's in your stomach from flowing back into your esophagus.

Stomach. After food enters your stomach, the stomach muscles mix the food and liquid with digestive juices. The stomach slowly empties its contents, called chyme, into your small intestine.

Small intestine. The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine, and push the mixture forward for further digestion. The walls of the small intestine absorb water and the digested nutrients into your bloodstream. As peristalsis continues, the waste products of the digestive process move into the large intestine.

Large intestine. Waste products from the digestive process include undigested parts of food, fluid, and older cells from the lining of your GI tract. The large intestine absorbs water and changes the waste from liquid into stool. Peristalsis helps move the stool into your rectum.

Rectum. The lower end of your large intestine, the rectum, stores stool until it pushes stool out of your anus during a bowel movement.

Watch this video to see how food moves through your GI tract.

How does my digestive system break food into small parts my body can use?

As food moves through your GI tract, your digestive organs break the food into smaller parts using:

motion, such as chewing, squeezing, and mixing

digestive juices, such as stomach acid, bile, and enzymes

Mouth. The digestive process starts in your mouth when you chew. Your salivary glands make saliva, a digestive juice, which moistens food so it moves more easily through your esophagus into your stomach. Saliva also has an enzyme that begins to break down starches in your food.

Esophagus. After you swallow, peristalsis pushes the food down your esophagus into your stomach.

Stomach. Glands in your stomach lining make stomach acid and enzymes that break down food. Muscles of your stomach mix the food with these digestive juices.

Pancreas. Your pancreas makes a digestive juice that has enzymes that break down carbohydrates, fats, and proteins. The pancreas delivers the digestive juice to the small intestine through small tubes called ducts.

Liver. Your liver makes a digestive juice called bile that helps digest fats and some vitamins. Bile ducts carry bile from your liver to your gallbladder for storage, or to the small intestine for use.

Gallbladder. Your gallbladder stores bile between meals. When you eat, your gallbladder squeezes bile through the bile ducts into your small intestine.

Small intestine. Your small intestine makes digestive juice, which mixes with bile and pancreatic juice to complete the breakdown of proteins, carbohydrates, and fats. Bacteria in your small intestine make some of the enzymes you need to digest carbohydrates. Your small intestine moves water from your bloodstream into your GI tract to help break down food. Your small intestine also absorbs water with other nutrients.

Large intestine. In your large intestine, more water moves from your GI tract into your bloodstream. Bacteria in your large intestine help break down remaining nutrients and make vitamin K. Waste products of digestion, including parts of food that are still too large, become stool.

What happens to the digested food?

The small intestine absorbs most of the nutrients in your food, and your circulatory system passes them on to other parts of your body to store or use. Special cells help absorbed nutrients cross the intestinal lining into your bloodstream. Your blood carries simple sugars, amino acids, glycerol, and some vitamins and salts to the liver. Your liver stores, processes, and delivers nutrients to the rest of your body when needed.

The lymph system, a network of vessels that carry white blood cells and a fluid called lymph throughout your body to fight infection, absorbs fatty acids and vitamins.

Your body uses sugars, amino acids, fatty acids, and glycerol to build substances you need for energy, growth, and cell repair.

How does my body control the digestive process?

Your hormones and nerves work together to help control the digestive process. Signals flow within your GI tract and back and forth from your GI tract to your brain.

Hormones

Cells lining your stomach and small intestine make and release hormones that control how your digestive system works. These hormones tell your body when to make digestive juices and send signals to your brain that you are hungry or full. Your pancreas also makes hormones that are important to digestion.

Nerves

You have nerves that connect your central nervous system-your brain and spinal cord-to your digestive system and control some digestive functions. For example, when you see or smell food, your brain sends a signal that causes your salivary glands to "make your mouth water" to prepare you to eat.

You also have an enteric nervous system (ENS)-nerves within the walls of your GI tract. When food stretches the walls of your GI tract, the nerves of your ENS release many different substances that speed up or delay the movement of food and the production of digestive juices. The nerves send signals to control the actions of your gut muscles to contract and relax to push food through your intestines.

Clinical Trials

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) conduct and support research into many diseases and conditions.

What are clinical trials, and are they right for you?

Clinical trials are part of clinical research and at the heart of all medical advances. Clinical trials look at new ways to prevent, detect, or treat disease. Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. Find out if clinical trials are right for you.

What clinical trials are open?

Clinical trials that are currently open and are recruiting can be viewed at www.ClinicalTrials.gov.

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Your Digestive System & How it Works | NIDDK

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The digestive system is made up of the gastrointestinal tract-also called the GI tract or digestive tract-and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus.

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Digestive System: Facts, Function & Diseases

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Digestive System: Facts, Function & Diseases

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Description of the digestive system

Also known as the gastrointestinal (GI) tract, the digestive system begins at the mouth, includes the esophagus, stomach, small intestine, large intestine (also known as the colon) and rectum, and ends at the anus. The entire system - from mouth to anus - is about 30 feet (9 meters) long, according to the American Society of Gastrointestinal Endoscopy (ASGE).

Digestion begins with the mouth. Even the smell of food can generate saliva, which is secreted by the salivary glands in the mouth, contains an enzyme, salivary amylase, which breaks down starch. Teeth, which are part of the skeletal system, play a key role in digestion. In carnivores, teeth are designed for killing and breaking down meat. Herbivores' teeth are made for grinding plants and other food to ease them through the digestion process.
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Swallowing pushes chewed food into the esophagus, where it passes through the oropharynx and hypopharynx. At this point, food takes the form of a small round mass and digestion becomes involuntary. A series of muscular contractions, called peristalsis, transports food through the rest of the system. The esophagus empties into the stomach, according to the National Institutes of Health (NIH).

The stomach's gastric juice, which is primarily a mix of hydrochloric acid and pepsin, starts breaking down proteins and killing potentially harmful bacteria, according to ASGE. After an hour or two of this process, a thick semi-liquid paste, called chyme, forms.

At this point the pyloric sphincter valve opens and chyme enters the duodenum, where it mixes with digestive enzymes from the pancreas and acidic bile from the gall bladder, according to the Cleveland Clinic. The next stop for the chyme is the small intestine, a 20-foot (6-meter) tube-shaped organ, where the majority of the absorption of nutrients occurs. The nutrients move into the bloodstream and are transported to the liver.

The liver creates glycogen from sugars and carbohydrates to give the body energy and converts dietary proteins into new proteins needed by the blood system. The liver also breaks down unwanted chemicals, such as alcohol, which is detoxified and passed from the body as waste, the Cleveland Clinic noted.

Whatever material is left goes into the large intestine. The function of the large intestine, which is about 5 feet long (1.5 meters), is primarily for storage and fermentation of indigestible matter. Also called the colon, it has four parts: the ascending colon, the transverse colon, the descending colon and the sigmoid colon. This is where water from the chyme is absorbed back into the body and feces are formed primarily from water (75 percent), dietary fiber and other waste products, according to the Cleveland Clinic. Feces are stored here until they are eliminated from the body through defecation.

Diagram of the digestive system

Diseases of the digestive system

Many symptoms can signal problems with the GI tract, including: abdominal pain, blood in the stool, bloating, constipation, diarrhea, heartburn, incontinence, nausea and vomiting and difficulty swallowing, according to the NIH.

Among the most widely known diseases of the digestive system is colon cancer. According to the Centers for Disease Control (CDC), 51,783 Americans died from colon cancer in 2011 (the most recent year for available data). Excluding skin cancers, colon and rectal cancer, or colorectal cancer, is the third most common cancer diagnosed in both men and women in the United States, according to the American Cancer Society.

Polyp growth and irregular cells, which may or may not be cancerous, are the most common development paths for colorectal cancers (also referred to as CRC), and can be detected during a routine colonoscopy, according to Dr. John Marks, a gastroenterologist affiliated with the Main Line Health health care system.

"The best news is that, if caught early enough, they can also be removed during the colonoscopy - eliminating the possibility that they grow further and become cancer," Marks said.

For those patients whose cancer has already spread, there are various minimally invasive surgical options that have extremely good prognoses. It is recommended that asymptomatic patients without a family history begin getting tested regularly between the ages 45 and 50, according to Marks. "Symptoms which may suggest that you need a colonoscopy at an earlier age include rectal bleeding and stool/bowel habit changes which last for more than a few days."

While CRC gets a great deal of attention, many diseases and conditions of the digestive system - including irritable bowel syndrome, diverticulitis, GERD (acid reflux) and Crohn's disease - can be chronic and are difficult to diagnose and treat, according to Dr. Larry Good, a gastroenterologist affiliated with South Nassau Communities Hospital. "With many of these diseases, blood work and colonoscopies all looks normal, so there is an absence of red flags."

Many of the diseases of the digestive system are tied to the foods we eat, and a number of sufferers can reduce their symptoms by restricting their diets, Good said. "Of course no one wants to hear that they can't eat certain foods, but many times, eliminating acidic things from the diet, such as tomatoes, onions, and red wine, can have an impact," Good said.

There are a number of tests to detect digestive tract ailments. A colonoscopy is the examination of the inside of the colon using a long, flexible, fiber-optic viewing instrument called a colonoscope, according the American Gastroenterological Association. Other testing procedures include upper GI endoscopy, capsule endoscopy, endoscopic retrograde cholangiopancreatography and endoscopic ultrasound.

Study of the digestive system

Gastroenterology is the branch of medicine focused on studying and treating the digestive system disorders. Physicians practicing this specialty are called gastroenterologists. The name is a combination of three ancient Greek words gastros (stomach), enteron (intestine) and logos (reason). It is an internal medicine subspecialty certified by the American Board of Internal Medicine.

To be certified as a gastroenterologist, a doctor must pass the Gastroenterology Certification Examination and undergo a minimum of 36 months of additional training.

Milestones

References to the digestive system can be traced back to the ancient Egyptians. Some milestones in the study of the gastrointestinal system include:

Claudius Galen (circa 130-200) lived at the end of the ancient Greek period and reviewed the teachings of Hippocrates and other Greek doctors. He theorized that the stomach acted independently from other systems in the body, almost with a separate brain. This was widely accepted until the 17th century.

In 1780, Italian physician Lazzaro Spallanzani conducted experiments to prove the impact of gastric juice on the digestion process.

Philipp Bozzini developed the Lichtleiter in 1805. This instrument, which was used to examine the urinary tract, rectum and pharynx, was the earliest endoscopy.

Adolf Kussmaul, a German physician, developed the gastroscope in 1868, using a sword swallower to help develop the diagnostic process.

Rudolph Schindler, known to some as the "father of gastroscopy," described many of the diseases involving the human digestive system in his illustrated textbook issued during World War I. He and Georg Wolf developed a semi-flexible gastroscope in 1932.

In 1970, Hiromi Shinya, a Japanese-born general surgeon, delivered the first report of a colonoscopy to the New York Surgical Society and in May 1971 presented his experiences to the American Society for Gastrointestinal Endoscopy.

In 2005, Australians Barry Marshall and Robin Warren were awarded the Nobel Prize in Physiology or Medicine for their discovery of Helicobacter pylori and its role in peptic ulcer disease.

Editor's Note: If you'd like more information on this topic, we recommend the following book:

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Digestive System: Facts, Function & Diseases

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Also known as the gastrointestinal (GI) tract, the digestive system begins at the mouth, includes the esophagus, stomach, small intestine, large intestine (also known as the colon) and rectum, and ends at the anus. The entire system - from mouth to anus - is about 30 feet (9 meters) long, according to the American Society of Gastrointestinal Endoscopy (ASGE).

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Digestive System | Everything You Need to Know, Including Pictures

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Digestive System | Everything You Need to Know, Including Pictures

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Continued From Above... To achieve the goal of providing energy and nutrients to the body, six major functions take place in the digestive system:

Ingestion

Secretion

Mixing and movement

Digestion

Absorption

Excretion

Digestive System Anatomy

Mouth

Food begins its journey through the digestive system in the mouth, also known as the oral cavity. Inside the mouth are many accessory organs that aid in the digestion of food-the tongue, teeth, and salivary glands. Teeth chop food into small pieces, which are moistened by saliva before the tongue and other muscles push the food into the pharynx.

Teeth. The are 32 small, hard organs found along the anterior and lateral edges of the mouth. Each tooth is made of a bone-like substance called dentin and covered in a layer of enamel-the hardest substance in the body. Teeth are living organs and contain blood vessels and nerves under the dentin in a soft region known as the pulp. The teeth are designed for cutting and grinding food into smaller pieces.

Tongue. The is located on the inferior portion of the mouth just posterior and medial to the teeth. It is a small organ made up of several pairs of covered in a thin, bumpy, skin-like layer. The outside of the tongue contains many rough papillae for gripping food as it is moved by the tongue's muscles. The taste buds on the surface of the tongue detect taste molecules in food and connect to nerves in the tongue to send taste information to the brain. The tongue also helps to push food toward the posterior part of the mouth for swallowing.

Salivary Glands. Surrounding the mouth are 3 sets of salivary glands. The salivary glands are accessory organs that produce a watery secretion known as saliva. Saliva helps to moisten food and begins the digestion of carbohydrates. The body also uses saliva to lubricate food as it passes through the mouth, pharynx, and esophagus.

Pharynx

The pharynx, or throat, is a funnel-shaped tube connected to the posterior end of the mouth. The pharynx is responsible for the passing of masses of chewed food from the mouth to the esophagus. The pharynx also plays an important role in the respiratory system, as air from the nasal cavity passes through the pharynx on its way to the larynx and eventually the . Because the pharynx serves two different functions, it contains a flap of tissue known as the epiglottis that acts as a switch to route food to the esophagus and air to the .

Esophagus

The is a muscular tube connecting the pharynx to the stomach that is part of the upper gastrointestinal tract. It carries swallowed masses of chewed food along its length. At the inferior end of the esophagus is a muscular ring called the lower esophageal sphincter or cardiac sphincter. The function of this sphincter is to close of the end of the esophagus and trap food in the stomach.

Stomach

The is a muscular sac that is located on the left side of the abdominal cavity, just inferior to the . In an average person, the stomach is about the size of their two fists placed next to each other. This major organ acts as a storage tank for food so that the body has time to digest large meals properly. The stomach also contains hydrochloric acid and digestive enzymes that continue the digestion of food that began in the mouth.

Small Intestine

The small intestine is a long, thin tube about 1 inch in diameter and about 10 feet long that is part of the lower gastrointestinal tract. It is located just inferior to the stomach and takes up most of the space in the abdominal cavity. The entire small intestine is coiled like a hose and the inside surface is full of many ridges and folds. These folds are used to maximize the digestion of food and absorption of nutrients. By the time food leaves the small intestine, around 90% of all nutrients have been extracted from the food that entered it.

Liver and Gallbladder

The liver is a roughly triangular accessory organ of the digestive system located to the right of the stomach, just inferior to the diaphragm and superior to the small intestine. The liver weighs about 3 pounds and is the second largest organ in the body.

The liver has many different functions in the body, but the main function of the liver in digestion is the production of bile and its secretion into the small intestine. The gallbladder is a small, pear-shaped organ located just posterior to the liver. The gallbladder is used to store and recycle excess bile from the small intestine so that it can be reused for the digestion of subsequent meals.

Pancreas

The pancreas is a large gland located just inferior and posterior to the stomach. It is about 6 inches long and shaped like short, lumpy snake with its "head" connected to the duodenum and its "tail" pointing to the left wall of the abdominal cavity. The pancreas secretes digestive enzymes into the small intestine to complete the chemical digestion of foods.

Large Intestine

The large intestine is a long, thick tube about 2.5 inches in diameter and about 5 feet long. It is located just inferior to the stomach and wraps around the superior and lateral border of the small intestine. The large intestine absorbs water and contains many symbiotic bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients. Feces in the large intestine exit the body through the anal canal.

Digestive System Physiology

The digestive system is responsible for taking whole foods and turning them into energy and nutrients to allow the body to function, grow, and repair itself. The six primary processes of the digestive system include:

1. Ingestion of food

2. Secretion of fluids and digestive enzymes

3. Mixing and movement of food and wastes through the body

4. Digestion of food into smaller pieces

5. Absorption of nutrients

6. Excretion of wastes

The first function of the digestive system is ingestion, or the intake of food. The mouth is responsible for this function, as it is the orifice through which all food enters the body. The mouth and stomach are also responsible for the storage of food as it is waiting to be digested. This storage capacity allows the body to eat only a few times each day and to ingest more food than it can process at one time.

In the course of a day, the digestive system secretes around 7 liters of fluids. These fluids include saliva, mucus, hydrochloric acid, enzymes, and bile. Saliva moistens dry food and contains salivary amylase, a digestive enzyme that begins the digestion of carbohydrates. Mucus serves as a protective barrier and lubricant inside of the GI tract. Hydrochloric acid helps to digest food chemically and protects the body by killing bacteria present in our food. Enzymes are like tiny biochemical machines that disassemble large macromolecules like proteins, carbohydrates, and lipids into their smaller components. Finally, bile is used to emulsify large masses of lipids into tiny globules for easy digestion.

The digestive system uses 3 main processes to move and mix food:

Swallowing. Swallowing is the process of using smooth and skeletal muscles in the mouth, tongue, and pharynx to push food out of the mouth, through the pharynx, and into the esophagus.

Peristalsis. Peristalsis is a muscular wave that travels the length of the GI tract, moving partially digested food a short distance down the tract. It takes many waves of peristalsis for food to travel from the esophagus, through the stomach and intestines, and reach the end of the GI tract.

Segmentation. Segmentation occurs only in the small intestine as short segments of intestine contract like hands squeezing a toothpaste tube. Segmentation helps to increase the absorption of nutrients by mixing food and increasing its contact with the walls of the intestine.

Digestion is the process of turning large pieces of food into its component chemicals. Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces. This mode of digestion begins with the chewing of food by the teeth and is continued through the muscular mixing of food by the stomach and intestines. Bile produced by the liver is also used to mechanically break fats into smaller globules. While food is being mechanically digested it is also being chemically digested as larger and more complex molecules are being broken down into smaller molecules that are easier to absorb. Chemical digestion begins in the mouth with salivary amylase in saliva splitting complex carbohydrates into simple carbohydrates. The enzymes and acid in the stomach continue chemical digestion, but the bulk of chemical digestion takes place in the small intestine thanks to the action of the pancreas. The pancreas secretes an incredibly strong digestive cocktail known as pancreatic juice, which is capable of digesting lipids, carbohydrates, proteins and nucleic acids. By the time food has left the duodenum, it has been reduced to its chemical building blocks-fatty acids, amino acids, monosaccharides, and nucleotides.

Once food has been reduced to its building blocks, it is ready for the body to absorb. Absorption begins in the stomach with simple molecules like water and alcohol being absorbed directly into the bloodstream. Most absorption takes place in the walls of the small intestine, which are densely folded to maximize the surface area in contact with digested food. Small blood and lymphatic vessels in the intestinal wall pick up the molecules and carry them to the rest of the body. The large intestine is also involved in the absorption of water and vitamins B and K before feces leave the body.

The final function of the digestive system is the excretion of waste in a process known as defecation. Defecation removes indigestible substances from the body so that they do not accumulate inside the gut. The timing of defecation is controlled voluntarily by the conscious part of the brain, but must be accomplished on a regular basis to prevent a backup of indigestible materials.

Digestive Disorders

Many diseases and health conditions - such as ulcers, GERD, IBD and celiac disease, just to name a few - lead to dysfunction in our digestive system. Learn about them by visiting our section on digestive diseases and conditions. (Also, now you can test for your genetic risk of acquiring celiac disease - learn more about DNA health testing.)

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Digestive System | Everything You Need to Know, Including Pictures

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Continued From Above... To achieve the goal of providing energy and nutrients to the body, six major functions take place in the digestive system: Ingestion Secretion Mixing and movement Digestion Absorption Excretion Food begins its journey through the digestive system in the mouth, also known as the oral cavity .