The Digestive The Digestive SystemSystem

1.Digestion1.Digestion The The mechanical mechanical and and chemical chemical

breakdown of food into molecules breakdown of food into molecules that can be absorbed across the that can be absorbed across the lining of the small intestine and lining of the small intestine and into the bloodstream as nutrients into the bloodstream as nutrients for the body.for the body.

2,3 Mechanical Digestion2,3 Mechanical Digestion

Mechanical digestion breaks food up into Mechanical digestion breaks food up into small pieces that are more accessible to small pieces that are more accessible to digestive enzymes.digestive enzymes.

It includes the chewing of teeth, the It includes the chewing of teeth, the churning of food in the stomach and churning of food in the stomach and peristalsis throughout the entire digestive peristalsis throughout the entire digestive process.process.

4,5,6 Chemical Digestion 4,5,6 Chemical Digestion

Chemical digestion refers to the Chemical digestion refers to the action of the digestive enzymes.action of the digestive enzymes.

The various digestive juices contain The various digestive juices contain enzymes that digest particular types of enzymes that digest particular types of food.food.

Examples:Examples: Salivary amylase: breaks starch down into Salivary amylase: breaks starch down into

maltosemaltose Pepsin: breaks proteins down into amino Pepsin: breaks proteins down into amino

acidsacids

7,8,9. Flow chart of 7,8,9. Flow chart of Digestion:Digestion:

Mouth Pharnyx Esophagus

StomachSmall IntestineLarge Intestine

Rectum Anus

Pancreas Liver Gallbladder

Salivary Glands

10-13 Mouth10-13 Mouth Food enters the mouth, where it is Food enters the mouth, where it is

mechanically digested. The teeth, the palate mechanically digested. The teeth, the palate (roof of mouth) and the tongue break the food (roof of mouth) and the tongue break the food down into small pieces.down into small pieces.

The Salivary Glands secrete Salivary Amylase The Salivary Glands secrete Salivary Amylase into the mouth that begins the chemical into the mouth that begins the chemical digestion of carbohydrates. digestion of carbohydrates.

Carbohydrates are broken down into simple Carbohydrates are broken down into simple sugars. (glucose)sugars. (glucose)

Food leaves the mouth in a bolus (moist, ball of Food leaves the mouth in a bolus (moist, ball of food)food)

CLEFT PALATECLEFT PALATE

CLEFT PALATECLEFT PALATE

CLEFT PALATE: BEFORE CLEFT PALATE: BEFORE AND AFTERAND AFTER

14,15 Pharynx14,15 Pharynx Food (bolus) travels through the Food (bolus) travels through the

throat “pharynx” on the way to throat “pharynx” on the way to the esophagus. the esophagus.

There is a flap of tissue called There is a flap of tissue called the epiglottis that prevents food the epiglottis that prevents food from going down the trachea. from going down the trachea.

Pharynx

16-20 16-20 EsophagusEsophagus

The esophagus is a muscular tube that joins the The esophagus is a muscular tube that joins the pharynx with the stomach.pharynx with the stomach.

Swallowing pushes the bolus into the esophagus.Swallowing pushes the bolus into the esophagus. Rhythmical contractions called peristalsis pushes Rhythmical contractions called peristalsis pushes

food through the esophagus to the stomach.food through the esophagus to the stomach. When the bolus reaches the end of the esophagus it When the bolus reaches the end of the esophagus it

goes through the cardiac sphincter into the stomach.goes through the cardiac sphincter into the stomach. This is the sphincter muscle that prevents the acidic This is the sphincter muscle that prevents the acidic

contents of the stomach from entering the contents of the stomach from entering the esophagus.esophagus.

21,22 Heartburn21,22 Heartburn Normally, the cardiac sphincter Normally, the cardiac sphincter

prevents the acidic contents of prevents the acidic contents of the stomach from entering the the stomach from entering the esophagus.esophagus.

Sometimes, heartburn, which Sometimes, heartburn, which feels like a burning pain rising up feels like a burning pain rising up into the throat, occurs when into the throat, occurs when some of the contents of the some of the contents of the stomach escape into the stomach escape into the esophagus.esophagus.

23-31 Stomach23-31 Stomach The stomach is a thick walled “J” shaped organ that lies The stomach is a thick walled “J” shaped organ that lies

underneath the diaphragm muscle.underneath the diaphragm muscle. The stomach stores food and starts the digestion of proteins.The stomach stores food and starts the digestion of proteins. The wall of the stomach has three muscular layers and The wall of the stomach has three muscular layers and

contains deep folds called “rugae”.contains deep folds called “rugae”. The muscular walls of the stomach churn, mixing the The muscular walls of the stomach churn, mixing the

contents.contents. Gastric glands secrete gastric juice into the stomach. Gastric glands secrete gastric juice into the stomach.

Gastric Juice contains HCl acid and a digestive enzyme called pepsin.Gastric Juice contains HCl acid and a digestive enzyme called pepsin. Pepsin digests protein and breaks in down into amino acids.Pepsin digests protein and breaks in down into amino acids.

Normally the stomach empties in 2-6 hours.Normally the stomach empties in 2-6 hours. When food leaves the stomach it is semisolid mixture called When food leaves the stomach it is semisolid mixture called

chyme.chyme.

Lap bandLap band

Gastric bypassGastric bypass

Rugae

(Inside walls of stomach)

32-34 ULCER32-34 ULCER Normally the wall of the Normally the wall of the

stomach is protected by a thick stomach is protected by a thick layer of mucus, but if chance, layer of mucus, but if chance, Hydrochloric Acid penetrates Hydrochloric Acid penetrates this mucus, an ulcer can form.this mucus, an ulcer can form.

An ulcer is an open sore in the An ulcer is an open sore in the stomach wall caused by gradual stomach wall caused by gradual breakdown of the mucus breakdown of the mucus membrane that lines the membrane that lines the stomachstomach

The most frequent cause of an The most frequent cause of an ulcer is an infection caused by ulcer is an infection caused by the bacterium helicobacter the bacterium helicobacter pylori. pylori.

35-38 Small Intestine 35-38 Small Intestine

The small intestine is named for its small The small intestine is named for its small diameter. (In comparison to the large diameter. (In comparison to the large intestine)intestine)

The small intestine averages about 10 feet The small intestine averages about 10 feet in length.in length.

The small intestine receives secretions The small intestine receives secretions from the pancreas and liver.from the pancreas and liver.

The primary function of the small intestine The primary function of the small intestine is absorption.is absorption.

Note the area in which the liver and pancreas secrete into the Duodenum of the small intestine.

The digestive tractThe digestive tract

39-41 Three parts of the 39-41 Three parts of the small intestine:small intestine:

Duodenum (du”o-de’num):Duodenum (du”o-de’num): The first 25 cm of the The first 25 cm of the small intestine. This part receives the pancreatic small intestine. This part receives the pancreatic secretions and bile from the liver.secretions and bile from the liver.

Jejunum (je-joo’num):Jejunum (je-joo’num): The next 3 feet of the The next 3 feet of the small intestine. This part contains the villi. small intestine. This part contains the villi. (fingerlike extensions that absorb nutrients)(fingerlike extensions that absorb nutrients)

Ileum: (il’e-um):Ileum: (il’e-um): The last 6-7 feet of the small The last 6-7 feet of the small intestine. This part also contains villi to absorb intestine. This part also contains villi to absorb nutrients from the digestive system to the nutrients from the digestive system to the circulatory system. circulatory system.

42-45 Villi42-45 Villi

The wall of the small intestine is made up of The wall of the small intestine is made up of fingerlike extensions called villi.fingerlike extensions called villi.

The epithelial cells of each villi have The epithelial cells of each villi have extensions called microvilli.extensions called microvilli.

The large number of villi and their microvilli The large number of villi and their microvilli increase the surface area of the small increase the surface area of the small intestine to provide more area for absorption.intestine to provide more area for absorption.

The surface area of the small intestine is The surface area of the small intestine is equal to a tennis court. equal to a tennis court.

villi

46-49 Large Intestine 46-49 Large Intestine Includes the Includes the cecum, colon, cecum, colon,

rectum and anal canalrectum and anal canal.. Larger in Larger in diameter diameter than the than the

small intestinesmall intestine The The cecum (se’kum):cecum (se’kum): is the is the

first portion of the large first portion of the large intestine. This is where the intestine. This is where the small intestine attaches to the small intestine attaches to the large intestine.large intestine.

The The appendixappendix is a small is a small projection from the cecum.projection from the cecum.

Superior to the Superior to the cecumcecum the large intestine is the large intestine is termed the termed the ascending colonascending colon. .

At the level of the liver, the large intestine At the level of the liver, the large intestine bends sharply and becomes the bends sharply and becomes the transverse transverse coloncolon, it travels across where it bends again , it travels across where it bends again and becomes the and becomes the descending colondescending colon..

50,5150,51

At the lower region of the large intestine, At the lower region of the large intestine, the descending colon turns in to form an the descending colon turns in to form an S shaped bend known as the sigmoid S shaped bend known as the sigmoid colon.colon.

The last 20 cm of the large intestine is The last 20 cm of the large intestine is known as the rectum, which ends in the known as the rectum, which ends in the anal canal, which opens at the anus. anal canal, which opens at the anus. (The out shoot) 52,53(The out shoot) 52,53

The large intestine absorbs water and electrolytes.The large intestine absorbs water and electrolytes. It prepares and stores non-digestible material It prepares and stores non-digestible material

(feces)(feces) Feces contain bile pigments and large quantities Feces contain bile pigments and large quantities

of bacteria (E-coli)of bacteria (E-coli) The E-coli bacteria live off of the fecal matter. The E-coli bacteria live off of the fecal matter.

When they break down this material, they emit When they break down this material, they emit odorous molecules that cause the characteristic odorous molecules that cause the characteristic fecal odor.fecal odor.

Some of the vitamins (Vitamin K and some B Some of the vitamins (Vitamin K and some B vitamins) and amino acids are produced by the E-vitamins) and amino acids are produced by the E-coli bacteria and absorbed by the intestinal lining. coli bacteria and absorbed by the intestinal lining.

The E-coli bacteria are beneficial for humans in The E-coli bacteria are beneficial for humans in this matter. 54-59this matter. 54-59

60,61 APPENDIX60,61 APPENDIX

The appendix is a fingerlike extension of The appendix is a fingerlike extension of the cecum of the large intestine.the cecum of the large intestine.

The appendix can become infected, The appendix can become infected, resulting in appendicitis, a very painful resulting in appendicitis, a very painful condition in which the fluid content of the condition in which the fluid content of the appendix can increase to the point that it appendix can increase to the point that it bursts.bursts.

62-64 Diarrhea & Constipation62-64 Diarrhea & Constipation

Two common everyday complaints Two common everyday complaints associated with the large intestine are associated with the large intestine are diarrhea and constipation.diarrhea and constipation.

In In diarrheadiarrhea, too little water is absorbed by , too little water is absorbed by the large intestine.the large intestine.

In In constipationconstipation, too much water is , too much water is absorbed by the large intestine.absorbed by the large intestine.

DiarrheaDiarrhea The major causes of diarrhea are The major causes of diarrhea are

infection of the lower tract and nervous infection of the lower tract and nervous stimulation.stimulation.

In the case of infection, such as food In the case of infection, such as food poisoning caused by eating poisoning caused by eating contaminated food, the intestinal wall contaminated food, the intestinal wall becomes irritated and peristalsis becomes irritated and peristalsis increases.increases.

Lack of water absorption is a Lack of water absorption is a protective measure by the body, and protective measure by the body, and diarrhea serves to rid the body of the diarrhea serves to rid the body of the infectious organisms.infectious organisms.

When a person is under stress, the When a person is under stress, the Nervous System sometimes stimulates Nervous System sometimes stimulates the intestinal wall, resulting in diarrhea.the intestinal wall, resulting in diarrhea.

Loss of water due to diarrhea may Loss of water due to diarrhea may lead to dehydration, a serious lead to dehydration, a serious condition in which the body tissues condition in which the body tissues lose their normal water content. 65-lose their normal water content. 65-6969

Constipation & Constipation & Hemorrhoids 70-73Hemorrhoids 70-73 When a person is constipated, the feces are When a person is constipated, the feces are

dry and hard.dry and hard. Chronic constipation is associated with the Chronic constipation is associated with the

development of hemorrhoids.development of hemorrhoids. Hemorrhoids are masses of tissue within the Hemorrhoids are masses of tissue within the

anal canal that contain blood vessels.anal canal that contain blood vessels. Internal hemorrhoids are normal. It is when the Internal hemorrhoids are normal. It is when the

hemorrhoids descend through the anal canal hemorrhoids descend through the anal canal that they become painful and irritated. that they become painful and irritated.

Severe Grade 3 Hemorrhoids

Accessory Organs: 74-75Accessory Organs: 74-75

Salivary GlandsSalivary Glands PancreasPancreas LiverLiver GallbladderGallbladder

•These organs are essential to the process of digestion, but food does not actually travel into any of these organs.

•These organs secrete important fluids into the primary organs of digestion to speed up the chemical digestive process.

The salivary The salivary glands 76-79glands 76-79

The salivary glands secrete about 1 liter of saliva each day, The salivary glands secrete about 1 liter of saliva each day, which enters the mouth by way of their ducts.which enters the mouth by way of their ducts.

Saliva contains mucus and a digestive enzyme called Saliva contains mucus and a digestive enzyme called salivary amylase.salivary amylase.

Salivary amylase begins the digestion of carbohydrates Salivary amylase begins the digestion of carbohydrates into simple sugars.into simple sugars.

There are three pairs of salivary glands: the sublingual There are three pairs of salivary glands: the sublingual glands (found underneath the tongue), the submandibular glands (found underneath the tongue), the submandibular glands (lie under the tongue at the back portion of the glands (lie under the tongue at the back portion of the mouth and the parotid glands which are located in front of mouth and the parotid glands which are located in front of and below the ears.and below the ears.

The PancreasThe Pancreas80-8280-82

The pancreas has both endocrine and exocrine The pancreas has both endocrine and exocrine functions.functions.

The exocrine functions are the ones associated The exocrine functions are the ones associated with digestion.with digestion.

The pancreas produces The pancreas produces pancreatic juicepancreatic juice, which , which contains contains sodium bicarbonatesodium bicarbonate, a chemical that , a chemical that neutralizes the HCl acid from the stomach, and neutralizes the HCl acid from the stomach, and digestive enzymesdigestive enzymes that break down that break down carbohydrates, proteins and fats into simple carbohydrates, proteins and fats into simple substances small enough to be absorbed by the substances small enough to be absorbed by the villi of the small intestine.villi of the small intestine.

The Liver 83-88 The Liver 83-88 The liver is the largest gland of the body.The liver is the largest gland of the body. The liver produces bile.The liver produces bile.

Bile is a yellowish green fluid. It contains bile salts Bile is a yellowish green fluid. It contains bile salts that emulsify fats once bile reaches the small that emulsify fats once bile reaches the small intestine.intestine.

The liver plays many other important roles in the body.The liver plays many other important roles in the body. It detoxifies the blood by removing poisonous It detoxifies the blood by removing poisonous

substances and metabolizing them.substances and metabolizing them. It stores glucose as glycogen after eating and the It stores glucose as glycogen after eating and the

breakdown of glycogen to glucose between meals to breakdown of glycogen to glucose between meals to maintain the blood glucose level. maintain the blood glucose level.

Cirrhosis of the Liver 89,90

•Cirrhosis is a chronic disease of the liver in which the organ first becomes fatty and then the liver tissue is replaced by scar tissue.

•This condition is most often the result of excessive amounts of alcohol in which the liver had to break down.

The Gallbladder 91,92The Gallbladder 91,92

The gallbladder is a pear shaped, The gallbladder is a pear shaped, muscular sac attached to the liver.muscular sac attached to the liver.

The liver produces bile and any excess The liver produces bile and any excess bile is stored in the gallbladder.bile is stored in the gallbladder.

•This is the inside of the gallbladder of a patient with gallstones.

•Gallstones are small, hard pellets that form in the gallbladder. Gallstones can range from a few millimeters to several centimeters in diameter. Most gallstones are formed from cholesterol.