Digestive Tract

Some Definitions

• Enzymes-proteins that help control a biochemical reaction

• Gland-an organ that produces specific enzymes or hormones

• Duct-a type of tube• Gastric-related to the stomach• Metabolism-breaking down big

molecules into smaller molecules• Pathology-study of the

characteristics, causes, and effects of diseases

Oral Cavity

Oral Cavity Functions

• Teeth help break food into smaller pieces

• Tongue helps form bolus of food

• Salivary glands provide moisture for the bolus

• Salivary glands produce an enzyme (amylase) to start breaking down starch into sugars

Tongue Pathologies

• Hairy Tongue

• Geographical Tongue

• Leukoplakia

• Glossodynia

• Painful papillae

• Yellow Tongue

Hairy Tongue

Leukoplakia of the Tongue

Glossodynia of the Tongue

Salivary Gland Pathologies

• Salivary gland infections

• Salivary gland stones

• Salivary gland tumors

Pharynx

• Initial point of entry for the bolus of food

• Epiglottis prevents food from going down the respiratory tract (trachea).

Location of Pharynx

Pharynx

Epiglottis

Location of the Esophagus

Esophageal Functions

• Pathway for the bolus into the stomach

• Very muscular to help food get into the stomach

• Esophagus moves in waves (peristaltic action) to force bolus downward

Esophageal Pathologies

• Gastroesophageal reflux disease (GERD)

• Heartburn

• Esophageal cancer

Esophageal Cancer

Cancer

Stomach

• Storage site for ingested food (bolus)

• Produces acid and gastric enzymes• Entry and exit of stomach is

controlled by sphincters (cardiac on top and pyloric on bottom)

• Very muscular gland to help mix and break up bolus

• Action of acid and enzymes convert bolus in chyme

Stomach

Stomach (Gastric) Pathologies

• Indigestion

• Heartburn

• Peptic ulcers

• GERD

• Gastric tumors

Early Gastric Tumor

Small Intestine

• Comprised of duodenum, jejunum, and ileum

• Duodenum contains the entry site for the bile duct and pancreatic duct

• Proteins, Fats, and Carbohydrates are metabolized in the small intestine

Small Intestine (cont.)

• Proteins are broken down into peptides and amino acids

• Fats are broken down into fatty acids and glycerol

• Carbohydrates are broken down into simple sugars

• Harmful acid from the stomach is neutralized by bicarbonate in the small intestine

Small Intestine (cont.)

• Fine capillaries are found in structures called the microvilli which allow absorption of nutrients into the blood stream

• Some water is also absorbed by the small intestine

Small Intestine Components

Small Intestine Pathologies

• Bleeding• Celiac disease• Crohn's disease• Infections• Intestinal cancers• Intestinal obstructions• Irritable bowel syndrome• Peptic ulcers

Crohn’s Disease

Cancer of the Small Intestine

Peptic Ulcer

Ulcer

Large Intestine

• Comprised of cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum

• Major site for reabsorption of water

• Majority of food metabolism has occurred

Large Intestine (cont.)

• Possibly up to 700 different species of “normal” bacteria occupy the large intestine

• Normal bacteria help break down some undigested food into smaller molecules as well as gas formation (carbon dioxide and nitrogen and some methane, hydrogen sulfide, and hydrogen

Large Intestine Components

Large Intestine Pathologies

• Constipation• Diarrhea• Celiac disease• Colon polyps• Diverticulitis• Irritable bowel syndrome• Intestinal parasites• Lactose intolerance• Ulcerative colitis• Appendicitis

Colon Polyps

Diverticulitis

Ulcerative Colitis

Appendicitis

Liver

• Large organ comprised of four lobes

• Large amount of blood flow throughout this organ

• Controls both metabolic (larger to smaller molecules and anabolic reactions (smaller to larger molecules

Liver Biochemical Reactions• Amino acid synthesis• Carbohydrate metabolism• Cholesterol synthesis• Lipogenesis (making of fats)• Synthesis of blood clotting factors• Makes red blood cells (in the fetus)• Bile synthesis (emulsifies fats)• Makes many enzymes and hormones• Breaks down hemoglobin (makes pigment in bile)• Converts ammonia to urea (to be excreted in the

urine)• Makes albumin for blood serum• Stores vitamins and minerals• Alters toxicity of chemicals (e.g., drug

metabolism)

Liver

Liver Pathologies

• Liver cancer

• Cirrhosis of the liver

• Jaundice

• Hepatitis

• Liver parasites

• Variety of metabolic disorders

Liver Cancer

Cirrhosis of the Liver

Liver Parasites (E. histolytica)

Abscess

Gall Bladder

• Stores the bile that is made in the liver

• Bile is introduced into the small intestine (duodenum) by the common bile duct

• Bile contains biliary salts that emulsify fats (make them more soluble in water; can be used as detergents)

• Many of the bile chemicals are pigmented and add color to the content of the small and large intestines)

Gall Bladder

                                                                   

                             

               

 

Gall Bladder

Bile Duct

Gall Bladder Pathologies

• Gall stones

• Spastic bile duct

• Gall bladder cancers

Gall Stones

Stones

Pancreas

• Produces both digestive enzymes and hormones

• Pancreatic hormones include insulin (removes glucose) and glucagon (releases glucose)

• Insulin is made in specialized cells called the islets of Langerhans

• Releases pancreatic juice which is a mixture of enzymes that breaks down the proteins, fats, and carbohydrates in the chyme

• Pancreatic juice travels from the pancreas through the pancreatic duct into the duodenum of the small intestine

Location of Pancreas

Pancreatic Pathologies

• Pancreatitis

• Pancreatic cancer

• Diabetes

Pancreatic Cancer

Cancer

The End of the Digestive Tract