The Digestive System

Najelly SanchezMark TobelloJohn Venegas

Eliab HernandezPer. 1

Parts and Organs of The Digestive System

What is The Digestive What is The Digestive System?System?The digestive system is a series of hollow organs joined in

a long, twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food.

Two solid organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes. In addition, parts of other organ systems (for instance, nerves and blood) play a major role in the digestive system.

Why is digestion important?Why is digestion important?

When we eat such things as bread, meat, and vegetables, they are not in a form that the body can use as nourishment. Our food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so that the body can use them to build and nourish cells and to provide energy.

How is food digested?How is food digested?

Digestion involves the mixing of food, its movement through the digestive tract, and chemical breakdown of the large molecules of food into smaller molecules. Digestion begins in the mouth, when we chew and swallow, and is completed in the small intestine. The chemical process varies somewhat for different kinds of food.

The MouthThe MouthMastication, or the chewing

of food in the mouth, is the first step of digestion. Saliva initiates digestion and changes the chewed food into a soft mass, or bolus. Saliva makes the bolus slippery, making it easier to be swallowed and slide down the back of the throat and esophagus. The bolus passes through the esophageal sphincter before it enters the stomach.

The Oral Cavity and Its Functions:The Oral Cavity and Its Functions:

Mechanical Processing

MoisteningMixing with

salivary secretions

What is the purpose of Oral What is the purpose of Oral Cavity?Cavity?Analyzes and senses material before

swallowingProcesses material through the actions of

the teeth, tongue, and surfaces of the palate(roof the Oral Cavity)

Lubricates material by mixing it with mucus and salivary secretions

Begins the digestion of carbohydrates and lipids with salivary enzymes

Your TeethYour Teeth

They help in chewing and breaking down the food

The TongueThe Tongue

The tongue is mainly composed of muscles. It is covered with a mucous membrane. Small nodules of tissue (papillae) cover the upper surface of the tongue. Between the papillae are the taste buds, which provide the sense of taste. In addition to taste, the tongue functions in moving food to aid chewing and swallowing, and it is important in speech.

Your TongueYour Tongue

It manipulates materials inside the mouth to bring food into the oral cavity.

Functions of the Tongue:1.Processes by compressing and distorting2.Manipulates to assist in chewing and to

prepare the material for swallowing3.Analyzes material by touch, temperature,

and taste receptors

Where are your Salivary Glands?Where are your Salivary Glands?The glands are found in and around your mouth and throat. We call the major salivary glands the parotid, submandibular, and sublingual glands.They all secrete saliva into your mouth, the parotid through tubes that drain saliva, called salivary ducts, near your upper teeth, submandibular under your tongue, and the sublingual through many ducts in the floor of your mouth.

The PharynxThe Pharynx

Serves as a passageway for solid food, liguids, and air.

Movement of Food Through the Movement of Food Through the SystemSystem

The large, hollow organs of the digestive system contain muscle that enables their walls to move. The movement of organ walls can propel food and liquid and also can mix the contents within each organ. Typical movement of the esophagus, stomach, and intestine is called peristalsis. The action of peristalsis looks like an ocean wave moving through the muscle. The muscle of the organ produces a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.

The first major muscle movement occurs when food or liquid is swallowed. Although we are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.

The EsophagusThe Esophagus

The esophagus is the organ into which the swallowed food is pushed. It connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike valve closing the passage between the two organs. However, as the food approaches the closed ring, the surrounding muscles relax and allow the food to pass.

The StomachThe Stomach The food then enters the

stomach, which has three mechanical tasks to do. First, the stomach must store the swallowed food and liquid. This requires the muscle of the upper part of the stomach to relax and accept large volumes of swallowed material. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. The third task of the stomach is to empty its contents slowly into the small intestine.

The Stomach cont.The Stomach cont.Several factors affect emptying of the

stomach, including the nature of the food (mainly its fat and protein content) and the degree of muscle action of the emptying stomach and the next organ to receive the contents (the small intestine). As the food is digested in the small intestine and dissolved into the juices from the pancreas, liver, and intestine, the contents of the intestine are mixed and pushed forward to allow further digestion.

DuodenumDuodenum

Located at the junction of the stomach and the small intestine, the duodenum is the first part of the small intestine. It is C-shaped and about 25 cm long.

What does the duodenum do?What does the duodenum do? The duodenum receives the thick liquid mixture of partly-

digested food and acid from the stomach. This acid is quickly neutralised in the alkaline environment of the duodenum.

The duodenum also receives bile from the gallbladder, and other digestive enzymes from the pancreas. These enter the duodenum through small ducts or tubes.

Other glands produce mucus that coats the digestive mixture to help ease its passage.

The food mixes with bile, mucus, and pancreatic and other digestive enzymes.

The bulk of the digestion of proteins, fats and carbohydrates takes place in the duodenum before the material travels further into the small intestine.

Jejunum and IleumJejunum and Ileum

The jejunum is the 1-2 m long, coiled mid-section of the small intestine. The ileum is the final portion of the small intestine, which leads into the large intestine. The ileum measures 2-4 m in length.

The role of the jejunum and ileumThe role of the jejunum and ileum

The inner linings of the jejunum and ileum contain very small finger-like bumps called 'villi'. The presence of these tiny bumps on the inside of the small intestine means that the surface area is much larger than if the lining were just a flat surface. This increased surface area improves the small intestine's ability to absorb nutrients.

The final stages of digestion are completed in this portion of the small intestine, where foods and liquids are fully broken down into their nutrient components such as:

smaller molecules (eg, glucose from carbohydrates; amino acids from proteins; fatty acids and cholesterol from fats)

vitamins minerals salts water As the digestive mixture travels through the small intestine, the villi

absorb the nutrients and transfer them to the bloodstream and the liver. Any food that has not been digested in the small intestine, ie fibre(along with some water and vitamins) then reaches the large intestine.

LiverLiver

The liver is a very large organ weighing up to 3 kg in adult humans.

What does the liver do?What does the liver do?The liver produces bile, a substance that

helps to break down fats. Bile produced in the liver is transferred to the gallbladder where it is stored until needed for digestion.

Once food, medicines, liquids, etc that you consume are digested in the small intestine and absorbed by the walls of the small intestine, these products of digestion (nutrients and other molecules) are then transferred to the liver for further processing.

GallbladderGallbladderThe gallbladder is

a small (10 cm long) pear-shaped organ that is located near the duodenum and the liver. The gallbladder is connected to the liver and the duodenum through small tubes.

Where is the gallbladder and what Where is the gallbladder and what does it do?does it do?

The gallbladder's main function is to store bile, a dark green digestive liquid produced by the liver. Bile is a substance that helps to break down fats. When stored in the gallbladder, bile becomes more concentrated and therefore more powerful in its ability to do its work.

When foods containing fats arrive in the small intestine, the gallbladder releases the stored bile into the duodenum. Here the bile helps to break down fats and also neutralize acids in the food that has arrived from the stomach.

Disorders/problems of the Disorders/problems of the gallbladdergallbladder

Gall StonesCholecystitisGallbladder cancer

PancreasPancreasThe pancreas is a

small flat organ (about 18-25 cm long) that is located behind the stomach and sits close to the duodenum. It is connected to the duodenum via a tube called the pancreatic duct.

The pancreas has two main The pancreas has two main functionsfunctions

1. It is the source of powerful digestive enzymes required to chemically break down fats, carbohydrates and proteins. The pancreas also secrete another substance to help neutralize stomach acid

2. The hormone insulin is made by the pancreas - insulin helps to balance blood sugar levels in the body

Pancreas cont.Pancreas cont.

When food reaches the lower stomach and then the duodenum, these organs give off signals to the pancreas telling it to secrete its many digestive enzymes. These enzymes and other substances are produced within the pancreas and then transferred to the duodenum where they neutralize acid and break down fats, carbohydrates and proteins into smaller molecules (nutrients) that can be used by the body.

Problems of the pancreas In some people, the pancreas may become inflamed,

giving rise to a condition known as 'Pancreatitis'.

The Small IntestineThe Small Intestine The liquefied bolus, now called

chyme, then passes through the pyloric sphincter and enters the duodenum, the first section of the small intestine. It is here that enzymes released from the pancreas, liver, and gallbladder further breakdown chyme into elements that can be easily absorbed and used by the body. The small intestine is lined with a heavily folded inner mucosa and small fingerlike projections called villi. The villi enable digested food to enter the bloodstream. It is here, in the small intestine, where all nutrients and vitamins are absorbed.

The Small Intestine cont.The Small Intestine cont.Finally, all of the digested nutrients are

absorbed through the intestinal walls. The waste products of this process include undigested parts of the food, known as fiber, and older cells that have been shed from the mucosa. These materials are propelled into the colon, where they remain, usually for a day or two, until the feces are expelled by a bowel movement.

Problems/disorders of the small Problems/disorders of the small intestineintestineThere are a number of things that can go

wrong in the small intestine. Information leaflets on some of these conditions are

Coeliac diseasePeptic ulcersInfections of the digestive tract

The Large intestineThe Large intestineChyme can travel through

up to 20 feet of small intestine before it passes through the ileocecal valve to enter the large intestine. Very little digestion occurs in the large intestine. Undigested chyme that enters the large intestine is considered waste. The waste becomes more and more solid as it passes through the large intestine because water is continuously being reabsorbed from the waste.

CaecumCaecumThe caecum is the

first part of the large intestine. Shaped like a small pouch and located in the right lower abdomen, it is the connection between the small intestine and the colon.

What does the caecum do?What does the caecum do?The caecum accepts and stores processed

material from the small intestine and moves it towards the colon. As the processed food approaches the end of the small intestine, a valve separating the small and large intestines opens, the caecum expands and the material enters. At this stage, the mixture normally contains:

undigested food (fibre)a little bit of watersome vitaminssome minerals or salts

AppendixAppendixThe appendix is a small

projection emerging from the caecum.

In human beings, the appendix has no known function and is thought to be a remnant from a previous time in human evolution.

In some people, the appendix becomes infected or inflamed (a condition known as 'appendicitis'), and the appendix needs to be removed (via surgery).

AppendicitisAppendicitis Appendicitis is a painful swelling and infection of the appendix. The Appendix is attached to the large intestine and located in the lower right area of the abdomen.

Scientists are not sure what the appendix does, if anything, but removing it does not appear to affect a person’s health.

What causes Appendicitis.

trauma to the abdomen eces, parasites, or growths that clog the appendiceal lumen enlarged lymph tissue in the wall of the appendix, caused by infection in the gastrointestinal tract

or elsewhere in the body

The symptoms are:

Trouble moving around due to agonizing pain Pain gets worse within hours pain start at the belly button and moves to the bottom right Vomiting loss of appetite constipation or diarrhea. and inability to pass gas.

ColonColon

Shaped like an inverted 'U', the colon is the longest part of the large intestine.

Where is the colon?Where is the colon?

The colon has four sections that are located in the abdominal cavity.

Ascending colon - starts at the caecum at the bottom right hand side of the abdomen and ascends (ie, goes upwards) towards the liver.

Transverse colon - transverse means 'across'. This part of the colon extends across the abdomen from right to left.

Descending colon - descends (goes downwards) on the left hand side of the abdomen.

Sigmoid colon - it is the last part of the large intestine, and is located on the bottom left hand side of the abdomen. It is the S-shaped connection between the descending colon and the rectum.

What does the colon do?What does the colon do?

Within the colon, the mixture of fibre, small amounts of water, and vitamins, etc, mixes with mucus and with bacteria that live in the large intestine - and starts to form faeces.

As faeces travels through the colon, the lining of the colon absorbs most of the water and some vitamins and minerals.

The bacteria in the colon chemically break down some of the fibre to produce nutrients for their own survival and to nourish the cells lining the colon. Thus, the fibre in your diet is extremely important to maintain the long-term health of the colon.

Through muscular movements of the colon, faeces is pushed along until finally, the walls of the sigmoid colon contract, causing the faeces to move into the rectum.

The RectumThe Rectum

Waste collects in the rectum, or end of the large intestine, until the brain signals for it to be expelled from the body.

Interesting factsInteresting facts The esophagus is approximately 25cm long. Muscles contract in waves to move

the food down the esophagus. This means that food would get to a person's stomach, even if they were standing on their head.

"Gas is basically produced by foods that have indigestible orexcess carbohydrates, which are not absorbed when they get to thecolon, explains Van Thiel. "Beans, for example, have complexcarbohydrates that are maldigested. And the same holds true formushrooms. Many people don't realize that mushrooms contain aunique sugar called raffinose, which humans can't break down.Cabbages and onions do the same thing." As a group, vegetariansproduce more gas than meat-eaters because the intestinal enzymescan't digest the cellulose in vegetables' cell walls. However,the colon's bacteria relish the stuff. The outcome: When a groupof young men, in the service of science, feasted on a diet richin pork and beans, their flatus elimination increased from 15 mlto 176 ml per hour!

The average male will eat about 50 tons of food during his lifetime in order to sustain a weight of 150 pounds.

The liver performs more than 500 functions.

Any Questions?