Unit F: Digestive System

Day 1: Intro to the Digestive System

What is Digestion?

• The process of changing complex solids foods into simpler soluble forms that cells can absorb.

• Enzyme – chemical substance that can promote reactions in living things

Also known as the: Alimentary Canal, Digestive Tract, and Gastrointestinal Tract (Lower & Upper GI)

Primary Structures: Body cannot do process without it

• Mouth

• Esophagus

• Stomach

• Small Intestines

• Large Intestines

Accessory Structures

• Tongue

• Teeth

• Salivary Glands

• Pancreas

• Liver

• Gall Bladder

4 Layers of the Alimentary Canal

• Innermost - Mucosa

  • Made of epithelial cells; secrets digestive juices (protection and lubrication)

• Submucosa

  • Connective tissue with fibers, blood vessels, and nerve endings

• Muscularis

  • Skeletal muscles that assist with swallowing

• Serosa

  • Visceral Peritoneum

Lining the Digestive System

• Peritoneum

  • Double Layered Serous Membrane that lines the abdominal cavity

• Mouth

  • Buccal Cavity or Oral Cavity

    • Tounge

    • Teeth

    • Salivary Glands

    • Palate

    • Uvula

Mouth Assists in

• Ingestion (food in mouth)

• Mechanical Breakdown (chewing) - mastication

• Chemical breakdown (enzymes in saliva)

• Ptyalin (Salivary Analyse) - converts starches into simple sugars - under control of the nervous system

• Preistalis - propulsion (pushing food back to pharynx for swallowing)

Lips

• Grab good and pull into mouth

Tongue

• Contain papillae that help to grip food better (sense of taste from taste buds)

Palate (roof of mouth)

• Hard and soft

Uvula

• Keeps food out of nasal cavity when swallowing

Tongue

• Attached to floor of mouth

• Made of skeletal muscle attached to 4 bones

  • Taste buds on surface: Sweet, Bitter, Sour, Salty

Teeth

• Primary (deciduous) 20 baby teeth

• Begin to appear at 6 months, Visible by 2 years

• Secondary (permanent)

  • 32 “adult teeth”

• Begin by 6 years of age

• 16 in mandible, 16 in maxilla

• Wisdom teeth - Last

  • Teens to early 20s

Teeth and Gums (Gingiva)

• Digestive enzymes help to chemically break down food once chewing begins

• Mastication – process of chewing (mechanical digestion)

Salivary Glands

• Secrete saliva into the mouth via connecting ducts. Contains mucus, antibodies, and enzymes to help moisten food and protect the mouth from bacterial infection.

• Parotid (largest)- under skin, just below and in front of the ears.

• Submandibular – medial side of the lower back part of the mandible.

• Sublingual – under each side of the tongue

Saliva Fun Fact

• 99.5% water

• The remainder is chlorides

• Salivary Amalyse (Ptyalin)

• Mucin

• Lysozyme-destroys bacteria

• Salivary Amalyse begins the breakdown of complex carbohydrates into simple sugars.

Pharynx

• Passage way for food and air

• 5” long

• Propulsion of food by peristalsis

• Food at this point is called a BOLUS-rounded mass (makes it easier to swallow)

• Most commonly considered part of the respiratory system

• Epiglottis at end that guides food to the esophagus when swallowing – Remember ---- Air goes to the trachea

• Swallowing = deglutination

Esophagus

• Flexible muscular tube that connects the pharynx to the stomach.

• About 10 inches long

• Travels through the diaphragm

• Food is propelled through by waves of peristalsis (muscular contraction to push food downward)

Stomach

• It is located in the upper left part of the abdominal cavity filled with gastric juices.

• Reservoirs where food is broken down both mechanically and chemically.

• Acidic in nature – protected by mucus membrane

  • Pepsin- breaks down protein

  • Hydrochloric acid destroys unwanted bacteria

• It contains the cardiac sphincter (top)- a circular muscular layer that controls the passage of food into the stomach from the esophagus.

• Pyloric sphincter (bottom) – a valve that regulates the entrance of food into the duodenum of the small intestine.

• The SPINCTERS open or close.

• Rugae – wrinkles or folds in the stomach wall that allow for size change.

• Peristalsis continues in the stomach

• The bolus of food now is known as CHYME – a semi-liquid, creamy substance

• Chyme leaves the stomach through the pyloric sphincter

• Fundus- upper part

• Body – middle part

• Pyloric region – lower end

Small intestines

• Gets its name from its diameter….much smaller than the large intestine even though it is longer

• Site of most of the chemical breakdown of food. Food is broken down into usable substances which can now be used by the tissue in the body.

• Site for Absorption – in small intestine, digested food passes into the bloodstream and on to body cells. Indigestible parts pass on to the large intestine.

3 Segments of Small Intestines

• Duodenum – 1st segment (curves around the pancreas),It is about 12 inches long

• Jejunum- 2nd section, it is about 8 foot long

• Ileum- final portion, 10 to 12 feet in length

Chemical digestion, absorption, and propulsion by peristalsis occur in all three segments of the small intestine.

Pancreas

• Located behind the stomach

• Secretes digestive enzyme (pancreatic juice) into the duodenum. It travels through the pancreatic duct and common bile ducts to get to small intestine.

• Enzymes here help digest proteins and fats; neutralize the acidic contents from the stomach.

• It also makes the hormone insulin and glucagon (endocrine system)

Liver

• Largest organ in body

• Located below the diaphragm, RUQ

• Connected to gallbladder and small intestine by ducts

• Produces and stores glucose in the form of glycogen

• Detoxifies alcohol, drugs and other harmful substances

• Manufactures blood proteins

• Manufactures bile-breaks down fats

• Stores vitamins A, D and B complex

Gallbladder

• Small green organ, inferior surface of the liver

• Stores and concentrates bile until the body needs it

• Releases bile to help break down fatty foods via the common bile duct

• Fat is then stored in lacteals in the intestinal wall until needed by the body

• You can live without your gallbladder, but you have to keep your liver ☺

Large Intestine

• Larger diameter than small intestine but shorter in length

• Approximately 2 inches in diameter

• Major segments – cecum, colon, rectum and anal canal (anus)

• Nutrients and water not absorbed in small intestines are absorbed here.

• Contains E. Coli (bacteria)

• Main function is propulsion and elimination of waste products not absorbed in the small intestines

• In the colon…Chyme becomes FECES

Parts of the large intestine

• Cecum – first part in lower right portion.

• Appendix – small fingerlike projection that extends from the cecum (not needed). It does contain lymphocytes.

• Colon- 4 segments- Ascending colon, transverse colon, descending colon, and sigmoid colon

• Rectum - last portion of the colon

• Anus - external opening

Defacation = Elimination of feces

Flatulence = Gas (Bacteria causes the odor)

Day 4

Functions of the Digestive System

1. Physical / Mechanical: breakdown of food

2. Chemical: Digestion of food into the end products of fat, carbohydrates, and protein

3. Absorption: nutrients blood capillaries of the small intestines

4. Elimination: Waste products of digestion

What is digestion: The process of changing complex solids foods into simpler soluble forms which can be absorbed by cells.

Activities of Digestion: Oral Cavity

• Mouth is where food gets into the body.

• Salivary glands make saliva with amylase (pytalin) enzyme that starts chemical breakdown converting starches into simple sugar and moistens food

• Teeth aid in mastication or chewing, the physical/mechanical breakdown.

• Tongue moves food and with taste buds sensing sweet, salty, sour and bitter

• Uvula keeps food out of nasal cavity

• Palate separates nasal cavity from oral cavity

Pharynx and Esophagus

• The Pharynx initiates swallowing.

• Food transforms into a bolus, a rounded food mass, which is prepared by mouth for swallowing

• The Esophagus propels food through waves of peristalsis (muscular contraction) in order to push food downward to stomach.

Chemical Breakdown in the Stomach

• The stomach takes ~2 hours to empty

• Stomach produces acidic enzymes to breakdown food

  • Enzymes – chemical substance that can promote reactions in living things

    • Pepsin- breaks down protein

    • Hydrochloric acid- destroys unwanted bacteria

• Sphincter:

  • Cardiac sphincter (top)- circular muscular layer that controls the passage of food into the stomach

  • Pyloric sphincter (bottom) – valve that regulates the entrance of food into the duodenum of small intestine

The food in the stomach is now called CHYME –semi liquid, creamy substance

Chemical Breakdown in the Small Intestine

• Food is still chemically broken down into usable substances which can now be used by the tissue in the body.

• Propulsion by peristalsis to move the chyme through small intestine

Absorption in the Small Intestine

• Absorption occurs in small intestine

• Movement of useable needed small molecules into the blood to be carried to other parts of the body

• Contains Villi: finger like projections that increase surface area to transport substances to blood stream

• Indigestible parts pass on to the large intestine.

Elimination in the Large Intestine

• Nutrients and water not absorbed in the small intestines are absorbed back into the bloodstream

• The Large Intestine’s (colon) main function is propulsion and elimination of waste products not absorbed in the small intestines

• FLATULENCE – gas formation 1-3 pints/day, pass it through rectum 14 times a day, bacteria produces the gas and its smell

• In the colon…Chyme becomes FECES – undigested semi-solid consisting of bacteria, waste products, mucous and cellulose

• DEFECATION – when large intestine fills, defecation reflex is triggered – colon and rectal muscles contract while internal sphincter relaxes – external anal sphincter under conscious control

Function of the Pancreas

• The pancreas secretes digestive enzymes like trypsin into the duodenum to help digest proteins and fats.

• Digestive enzymes travel through the pancreatic duct and common bile duct to get to small intestine.

• The pancreas also makes the hormone insulin (endocrine system) to regulate blood sugar levels

The function of the Liver

• The liver produces and stores glucose in the form of glycogen

• It detoxifies alcohol, drugs and other harmful substances

• The liver manufactures blood proteins like Vitamin K which is important in blood clotting

• It manufactures bile

• It stores Vitamins A, D, and B

Functions of the Gall Bladder

• The gall bladder stores and concentrates bile until it is needed by the body

• It releases bile to help break down fatty foods via the common bile duct.

• Fat is then stored in the intestinal wall until needed by the body

• You can live without your gallbladder, but you have to keep your liver!

Disorders of the Digestive System

Cholecystitis

• Inflammation of the gall bladder

• Can result in swelling gallbladder, pain, and possible infection

Cholelithiasis (gall stones)

• Can block bile duct causing pain and other digestive disorders

• Small ones may pass on their own, large ones are surgically removed

Surgical removal of the gallbladder: Cholecystectomy

Hiatal Hernia

• Condition in which the upper part of your stomach bulges through an opening in your diaphragm

• More common after the age of 50

• Higher risk with obesity or smoking

• Treatments include eating small meals, avoiding certain foods, not smoking or drinking alcohol, and losing weight

• Doctor may prescribe antacids or other medications

Constipation

• Painful condition where bowel movements become infrequent or difficult

  • Cause

    • Nutritional deficiencies

    • Stress

    • Pregnancy

  • Prevention / Treatment

    • Eating a healthy diet

    • Exercising

    • Drinking plenty of water

    • Laxatives and stool softener

Diarrhea

• Loose, watery bowel movement when feces pass through the colon too rapidly

  • Causes:

    • Toxic substances / antigens (food poisoning, virus, bacteria)

    • Poor Diet

    • Nervousness

  • Treatments

    • Plenty of fluids

    • take over-the-counter Immodium

    • medical attention is recommended for prolonged cases of diarrhea dehydration

Gastroenteritis

• Inflammation of mucous membrane lining of stomach and intestine

• Very contagious

Cause:

• Viral (rotaviruses or hepatitis A)

• Bacterial (e. coli or salmonella)

Symptoms: diarrhea and vomiting

Complications of possible dehydration

• Treatment / Prevention

  • Washing hands regularly

  • Stay hydrated

Gerd - Gastroesophageal Reflux Disease

Acid Reflux: food from stomach re-enters esophagus

• Symptoms: Chronic cough and chest pain and burning

• Treatment

  • Diet Changes

  • Medications (antacids, histamine 2 blockers Pepcid)

  • Don’t lay down 2-3 hours after eating

  • Loosing weight

Hepatitis Alphabet

Hepatitis A

• Infectious hepatitis

• Cause: Virus spread through contaminated food & water

• Rare

• Vaccine available

Hepatitis B & C (Serum Hepatitis)

• Caused by virus found in blood

• Transmitted by blood or body fluids, unprotected sex, contaminated needle (drug user)

• Vaccine for Hepatitis B (not c)

Cirrhosis

• Chronic slow progressive disease of the liver

• Normal tissue replaced b y fibrous connective tissue (scar tissue)

• Scar tissue causes blockage of blood flow and slows the processing of nutrients, hormones, drugs, and naturally produced toxins and production of proteins and other substances

• Causes: Excessive alcohol consumption & hepatitis; abuse of Tylenol (acetaminophen)

Irritable Bowel Syndrome (IBS)

• An intestinal disorder causing pain in the belly, gas, diarrhea, and constipation

• Most common in women

• Two types of IBS: Crohn’s disease or Ulcerative Colitis- Autoimmune Disease

• Causes are unknown

• Symptoms

  • Diarrhea

  • Constipation

  • Abdominal cramps

• Treatments

  • diet

  • lifestyle changes

  • medications

Peptic Ulcers (Stomach Ulcers)

• Sore or lesion that forms in the lining of the stomach

• Cause

  • H. pylori (bacteria)

  • Smoking & Alcohol

  • Stress

• Symptoms

  • Burning pain in the abdomen between meals and early morning

• Treatment

  • May be relieved by eating or taking an antacid