Digestive System: Mouth and Stomach

• The digestive system is nearly 30 feet long to digest and absorb food effectively.
• The human gut contains approximately 8 pounds (about a gallon) of bacteria.

Mouth

• Teeth chew food, easing the swallowing process.
• Incisors are used to cut food.
• Canines are used to tear food.
• Molars are used to grind and cut food.
• The tongue, a skeletal muscle, moves food around the mouth, directing it into the esophagus.
• The esophagus uses smooth muscle contractions to squeeze food down towards the stomach.
• Peristalsis refers to these involuntary muscle movements that propel food and waste through the digestive tract.

Stomach

• The stomach expands and contracts to hold food and break it into smaller pieces, taking around 4 hours to process food.
• Stomach muscles in the stomach wall aid in the mechanical digestion of food.
• The stomach lining produces gastric juices, which break down food and kill bacteria.
• The stomach, composed of smooth muscle, produces and contains acid to break down food and bacteria.
• Mucus protects the stomach lining from the acid it contains.
• Food is processed into a paste-like consistency in the stomach and then released as a liquid.
• A sphincter muscle (Esophageal at top, pyloric at bottom) controls the flow of food/waste in the digestive tract.

Digestive overview

• The small intestine further breaks down food received from the stomach, enabling the body to absorb nutrients.
• The pancreas, liver, and gallbladder support food breakdown by delivering various gastric juices to the small intestine but never touch the food.
• The pancreas produces juices that aid the body in digesting fats and proteins.

Pancreas

• The pancreas releases pancreatic juices containing enzymes for digestion and a substance to neutralize stomach acid, while also producing insulin.
• Enzymes are proteins that facilitate specific processes.
• Glucose originates from plants through photosynthesis.
• Starch is a long chain of glucose molecules.

Liver

• The liver produces bile, which helps in the absorption of fats into the bloodstream.
• The gallbladder stores extra bile for future use.

Liver Functions

• The liver filters nutrients, removing harmful substances and wastes.
• It converts some waste into bile, sending it to the small intestine or gallbladder.
• Nutrients are then distributed throughout the body via the bloodstream.
• The liver detoxifies the blood, produces bile, and stores glucose as glycogen.
• The alimentary canal is the "food tube" from mouth to anus, not including the gall bladder, liver, or pancreas.

Large Intestine

• The large intestine removes unusable liquid food parts from the small intestine.
• The colon removes water and minerals from the liquid, absorbing them into the blood.
• The rectum stores solid waste until it's expelled.
• The small intestine is 15-20 feet long, while the large intestine is 5-10 feet long.
• The three parts of the large intestine are the ascending, transverse, and descending colon.
• 11.5 Liters of fluid pass through the intestines daily from food/drink, saliva, acid, mucus, pancreatic juices, and bile, with only 0.1 L excreted as solid waste.

Digestive system processes

• The digestive system breaks down food into small molecules and absorbs them into the body.
• The two main processes are digestion and absorption.

Digestion

• Digestion involves mechanically breaking up food and using enzymes to digest its components.
• The mouth breaks food into small pieces and digests starch using enzymes.
• The stomach churns food and mixes it with mucus and gastric juices containing enzymes.
• The small intestine combines enzymes from the pancreas and liver to continue breaking down food.
• The pancreas releases enzymes that digest carbohydrates, fats, and proteins.
• The liver filters toxins from the blood and produces bile.
• The large intestine removes water from food, creating feces.
• Saliva contains the enzyme amylase, which breaks starch into glucose.

Digestion Organs

• Mouth: mechanical digestion with teeth, chemical digestion with saliva.
• Stomach: mechanical digestion with muscle contractions, chemical digestion with acid.
• Small intestine: chemical digestion using bile and pancreatic enzymes.
• Most bodily energy (80%) is stored as fats, with the remaining 20% as carbs.

Absorption

• Some water, salt, sugar, and alcohol are absorbed directly through the stomach wall.
• Vitamins, minerals, fats, carbohydrates, and proteins are absorbed into the bloodstream through the walls of the small intestine.
• Water is absorbed into the blood through the lining of the large intestine.

Absorption Organs

• Stomach absorbs some water, sugars, alcohol, and salt.
• Small intestine absorbs vitamins, minerals, fats, carbohydrates, and proteins.
• Large intestine absorbs most water.
• An individual consumes approximately 30 tons of food during their lifetime.
• Examples of carbohydrates: sugar, starch, glucose, glycogen.

Common ailments

• Common ailments affecting the digestive system include Gastroesophageal Reflux Disease (GERD), ulcers, inflammatory bowel disease, constipation/diarrhea, irritable bowel syndrome (IBS), hepatitis, and liver, pancreatic, and stomach cancer.
• Chronic conditions last a long time and reoccur.
• Acute conditions are sudden and intense.

GERD

• Gastroesophageal Reflux Disease (GERD) is a chronic condition affecting millions worldwide.
• Heartburn is the most common symptom.
• Other symptoms may include belching, difficulty swallowing, waterbrash, dysphagia, chronic sore throat, laryngitis, gum inflammation, teeth enamel erosion, chronic throat irritation, hoarseness, a sour taste, and bad breath.
• Heartburn, the most common symptom of GERD, occurs when acid enters the esophagus from the stomach, causing burning and pain.
• A weakened esophageal sphincter lets stomach acid into the esophagus.

Ulcers

• Risk factors for ulcers include stress, family history, smoking, excess alcohol consumption, use of NSAIDs or corticosteroids, improper diet, and type O blood.
• Ulcers are small holes in the digestive tract.
• Ulcers are not caused by stress, contagious, or cancerous, and are treatable.
• Symptoms may include a burning or gnawing feeling in the stomach area, loss of appetite, and weight loss.
• Excessive salt consumption can dissolve mucus.
• Stress can exacerbate ulcers but does not cause them.
• Ulcers can occur throughout the body, not just in the stomach.

Inflammatory Bowel Disease

• Inflammatory Bowel Disease (IBD) is a group of disorders causing the intestines to become red and swollen.
• Inflammation is long-lasting and reoccurs.
• Causes are unknown.
• It is not contagious.
• Symptoms include abdominal cramps and pain, diarrhea, weight loss, and bleeding from the intestines.
• IBD involves swelling of the small and large intestines, impairing nutrient and water absorption.
• Individuals with IBD are often underweight.
• The immune system overreacts to gut bacteria in individuals with IBD.

Constipation

• Constipation is difficulty having bowel movements.
• Symptoms may include difficulty in having bowel movements, small, dry, and hard bowel movements, bowel movements less than three times a week, and feeling bloated or uncomfortable.
• Causes include not enough fiber or liquids in the diet, lack of exercise, certain medications, irritable bowel syndrome, changes in routine, abuse of laxatives, ignoring the urge to have a bowel movement, or problems with colon, rectum, or intestinal functions.
• Constipation results from excessive water absorption in the large intestine, leading to overly solid stool.
• Laxatives help by relaxing the bowels.
• Drinking more water, eating more fiber, and staying active can help.

Diarrhea

• Diarrhea involves loose, watery stools and bowel movements more than three times in one day.
• Causes include bacterial or viral infections, food intolerances, parasites, certain medications, or intestinal diseases.
• In diarrhea, the large intestines do not remove enough water.
• Diarrhea can be caused by parasites, colds, flu, or eating something the body dislikes.

Irritable Bowel Syndrome

• Irritable Bowel Syndrome (IBS) primarily affects the large intestine.
• IBS is a disorder that does not damage the bowel or large intestines.
• In IBS, the nerves and muscles in the bowel are overly sensitive.
• Symptoms include cramping, diarrhea, bloating, and gas.
• There is no cure for IBS, but symptoms can be relieved through stress relief, diet changes, or medications.
• IBS does not cause physical injury, unlike inflammatory bowel disease (IBD).

Hepatitis

• Hepatitis is inflammation of the liver, typically caused by an infection or alcohol.
• There are five types: A, B, C, D, and E.
• Hepatitis causes swelling of the liver.

Hepatitis A

• Hepatitis A is extremely common in the U.S., infecting 1 in 3 Americans at some point.
• Most people recover completely without treatment and may develop lifelong immunity.
• It is transmitted via the fecal-to-oral route through contaminated food and water, or poor hygiene.
• It is prevented by washing hands with warm water and soap.
• Symptoms include loss of appetite, fever, and fatigue.
• Hepatitis A is often contracted through contaminated hands preparing food, drinking contaminated water, or eating shellfish raised in contaminated water.

Hepatitis B

• Hepatitis B is the most widespread hepatitis virus.
• Transmitted by blood, sexual contact, or during childbirth.
• Symptoms include low-grade fever, aches, and mild abdominal pain.
• Prevented by vaccine and good hygiene.

Hepatitis C

• Hepatitis C is a common cause of chronic liver disease.
• Not related to other Hepatitis viruses and is contagious.
• Transmitted by contact with blood or blood products.
• It is a chronic condition lasting more than six months.
• Untreated Hepatitis C can lead to serious health problems.
• Symptoms are similar to Hepatitis A and B.

Hepatitis D & E

• Hepatitis D & E rare types that occur in a small percentage of the population.

Stomach cancer

• Stomach cancer, known as gastric cancer, can start in any area of the stomach.
• Symptoms include indigestion or heartburn, abdominal discomfort or pain, nausea and vomiting, diarrhea or constipation, bloating after meals, loss of appetite, weakness and fatigue, bloody vomit, and blood in the stool.

Liver Cancer

• Liver cancer either originates in the liver or spreads from cancer elsewhere.
• Symptoms include weight loss, poor appetite, enlarged, hard, tender liver, fever, enlarged spleen, jaundice, confusion, and drowsiness.
• The liver cancer is a type of metastatic cancer, meaning it usually starts somewhere else and spreads to the liver.

Pancreatic Cancer

• Pancreatic cancer typically impacts people over 50.
• Adenocarcinoma is the most common form, attacking the lining of the pancreatic duct.
• Symptoms include abdominal pain, poor appetite, weight loss, jaundice, indigestion, nausea and vomiting, diarrhea, and fatigue.

Cancer treatments

• Common cancer treatments include surgery to remove cancerous tissue, radiation therapy using external beams or implanted seeds, and chemotherapy using anticancer drugs to destroy the tumor.
• Cancer cells divide rapidly, making them weaker than normal cells.
• Doctors use toxins at high enough levels to kill cancer cells without killing healthy cells.

Cancer info

• Cancer occurs when a cell's DNA gets broken and cannot stop dividing.
• Radiation and chemicals can damage DNA.
• People die from critical organs having their shapes changed from the cancer and no longer functioning.
• A tumor is when dividing cells stay in one place.