The Digestive SystemHealth Science 1

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What is Digestion The process of changing complex solids

foods into simpler soluble forms which can be absorbed by cells.

Enzyme – chemical substance that can promote reactions in living things

Terminology Alimentary canal

› Also known as the GI (gastrointestinal tract)

› Begins with the mouth and ends with the anus

› Include Mouth Pharynx Esophagus Stomach Small intestines Large intestine

• Accessory Organs• Teeth• Tongue• Salivary glands• Pancreas• Liver• Gallbladder

• Connected to the GI tract by series of ducts

• Aid in chemical breakdown and absorption of food.

Alimentary canal

Accessory Organs included

Lining the Digestive System Peritoneum

› Double layered serous membrane that lines the abdominal cavity

Digestive System Functions Physical Breakdown of food Chemical digestion of food into the end

products of fat, carbohydrates and protein

Absorb nutrients into blood capillaries of the small intestines

Eliminate waste products of digestion

6 Activities of Digestion (in order)

1 – Ingestion› Getting food into the body› Mouth, teeth, lips and tongue

2 – Mechanical Breakdown › Smaller pieces of food (chewing, churning in

stomach, churning by muscular contraction in small intestine)

3 – Propulsion› Initiated by swallowing (pharynx)› Peristalsis (symmetrical contraction of muscles

that moves food along the GI tract

6 Activities of Digestion (in order)

4 – Chemical breakdown› Commonly called “digestion”› Enzymes breakdown food

5 – Absorption› Movement of small molecules from small

intestine into the blood to be carried to other parts of the body

6 – Defecation› Expulsion of the food that was not absorbed

through the anus.

Mouth (oral cavity) Assist in

› Ingestion (food in mouth)› Mechanical breakdown

(chewing)- also called mastication

› Chemical breakdown (enzymes in saliva)

› PTYALIN- converts starches into simple sugars – under control of the nervous system

› Propulsion (pushing food back to pharynx for swallowing)

Lips – grab food 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

Mouth cont… Teeth and Gums

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

› Mastication – process of chewing (mechanical digestion)

Children have 20 deciduous (temporary)› Start to appear

around 6 months› Usually all are

visible by 2 yrs of age

Permanent teeth begin to form around 6 years of age in the jawbones

32 total (16 in mandible and 16 in maxilla)

As these grow, the deciduous teeth are pushed out

The wisdom teeth are generally the last to appear, usually late teens to early twenties.

Incisors Canine Premolars molars

2123 System – 2 incisors, 1 canine, 2premolars, 3 molars

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.

Pharynx Food at this point is called a BOLUS Passage way for food and air Propulsion of food by peristalsis

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

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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 Located in upper more left part of abdominal cavity

filled with gastric juices. Acidic in nature – protected by mucus membrane

› Pepsin- breaks down protein› Hydrochloric acid destroys unwanted bacteria

Reservoir where food is broken down both mechanically and chemically.

Contains 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.

Stomach cont…. Rugae – mucous coated lining inside the

stomach (folds of tissue)

Peristalsis continues in the stomach

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

Chyme leaves the stomach through the pyloric sphincter

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Parts of the stomach 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. Undigestible parts pass on to the large intestine.

3 segments of small intestines

Duodenum – 1st segment (curves around the pancreas.

Is about 12 inches long

Jejunum- 2nd section, 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.

It also makes the hormone insulin (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 Detoxify alcohol, drugs and other harmful

substances Manufactures blood proteins Manufactures bile Stores vitamins A, D and B complex

Gallbladder Small green organ, inferior surface of the liver Stores and concentrates bile until it is needed

by the body 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

GERD – Gastroesophageal Reflux Disease

Heartburn or acid reflux symptoms include chronic cough and chest pain and burning. Knowing your triggers, such as certain foods, medications, obesity, or even stress, can help prevent heartburn. Heartburn treatment may include medications, home remedies, or diet changes.

http://www.webmd.com/heartburn-gerd/ss/slideshow-heartburn-overview

Gastroenteritis Gastroenteritis is inflammation of the stomach and

intestines, which leads to diarrhea and vomiting. Gastroenteritis is most often due to a bacterial or viral infection. Gastroenteritis that results from a virus is called viral gastroenteritis. Many different viruses cause gastroenteritis, including some rotaviruses, noroviruses, and adenoviruses. Viral gastroenteritis is contagious. Bacterial gastroenteritis is often caused by infection with E. coli and salmonella. Other causes of gastroenteritis include parasite infection, exposure to harmful chemicals in seafood or water, use of certain medications, and irritation from particular foods.

http://www.webmd.com/children/ss/nausea-vomiting-remedies-treatment

Peptic ulcer http://www.webmd.com/digestive-disor

ders/tc/peptic-ulcer-disease-topic-overview

Appendicitis Appendix becomes inflamed

If it ruptures, bacteria will spread to peritoneal cavity causing a very dangerous infection.

Symptoms - fever, acute pain in LRQ

RX- surgical removal & antibiotics

Hepatitis Inflammation of the liver Types A, B, C

http://www.webmd.com/hepatitis/ss/slideshow-hepatitis-overview

CirrhosisCirrhosis is a slowly progressing disease in which healthy liver tissue is replaced with scar tissue, eventually preventing the liver from functioning properly. The scar tissue blocks the flow of blood through the liver and slows the processing of nutrients, hormones, drugs, and naturally produced toxins. It also slows the production of proteins and other substances made by the liver.

JAUNDICE – yellow discoloration of the skin and sclera of the eyes.

Cholecystitis

Cholecystitis is inflammation of the gallbladder, a small organ near the liver that plays a part in digesting food. Normally, fluid called bile passes out of the gallbladder on its way to the small intestine. If the flow of bile is blocked, it builds up inside the gallbladder, causing swelling, pain, and possible infection.

Commonly caused by CHOLELITHIASIS

Cholelythiasis A gallstone stuck in the cystic duct , a

tube that carries bile from the gallbladder, is most often the cause of sudden (acute) cholecystitis. The gallstone blocks fluid from passing out of the gallbladder. This results in an irritated and swollen gallbladder. Infection or trauma, such as an injury from a car accident, can also cause cholecystitis.

Diarrhea Diarrhea is a loose, watery bowel movement

and is not usually a serious problem in the U.S. It can occur due to illness, intestinal problems, food poisoning, and many others factors. It usually goes away on its own, but you should drink plenty of fluids and can take over-the-counter medications to help ease the discomfort. For prolonged cases of diarrhea, medical attention is recommended.

http://www.webmd.com/digestive-disorders/video/drossman-diarrhea-overview

Constipation Constipation is a common but painful

condition that occurs when bowel movements become infrequent or difficult. It can be caused by nutritional deficiencies, stress, pregnancy, cancer, depression, and more. The best way to prevent constipation is eating a healthy diet, exercising, and drinking plenty of water. Laxatives can help relieve constipation.

http://www.webmd.com/digestive-disorders/ss/slideshow-constipation-facts-10

Irritable bowel syndrome Irritable bowel syndrome or IBS affects

mostly women. Causes are unknown. IBS symptoms include diarrhea, constipation, and abdominal cramps. IBS treatments include diet and lifestyle changes and medications.

http://www.webmd.com/ibs/ss/slideshow-ibs-overview

Anorexia Nervosa Anorexia

› Intense fear of gaining weight› Restrict food intake, especially those with

fat content› Weight is 85% less than expected body

weight› Over exercising› Avoiding food altogether, or only allowing

minimal low calorie intake.

Physical Symptoms Common physical signs of malnutrition from

anorexia include: A low body weight. Constipation and slow emptying of the stomach. Thinning hair, dry skin, and brittle nails. Shrunken breasts. Stopping or never getting a monthly menstrual

period. Feeling cold, with a lower-than-normal body

temperature. Low blood pressure.

Treatment All people with anorexia need

treatment. In most cases, this involves seeing a doctor and having regular counseling sessions. A hospital stay is needed for those who are seriously underweight or who have severe medical problems. The goals of treatment are to restore a healthy weight and healthy eating habits.