Digestive System

Digestive System

• Digestion• Process of changing complex solid

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

• Enzymes• Chemical substances that promotes

chemical reactions in living things• Alimentary Canal

• Digestive tract/gastrointestinal tract.• 30 ft tube from mouth to anus

Digestive System

• Peritoneum• Double-layered serous membrane that

lines the abdominal cavity

• Functions• Physical breakdown of food• Chemical digestion of food into the end

products of fat, carbohydrates, & protein• Absorb nutrients into blood capillaries of

the small intestines• Eliminate waste products of digestion

Structure of Organs

• Mouth• Food enters digestive system through

mouth• Inside of mouth covered with mucous

membrane• Roof of mouth is Hard Palate (bone) & soft

palate• Uvula

• Flap that hangs off soft palate• Prevents food from going up the nose

when you swallow

Structure of Organs

• Tongue• Attached to floor of mouth• Helps in chewing & swallowing• Made of skeletal muscle attached to 4

bones• Taste buds on the surface

• Salivary Glands• Three pairs of glands• Secrete saliva

• Teeth• Gingiva – gums, support & protect

teeth• Mastication – chewing, mechanical

digestion

Structure of Organs• Esophagus

• Muscular tube, 10” long• Connects pharynx & stomach

• Stomach• Cardiac sphincter – circular layer of muscle,

controls passage of food into stomach• Pyloric sphincter – valve, regulates the

entrance of food into duodenum• Rugae – mucous coat lining of stomach• Allows to contract (peristalsis) & push food

into small intestine

Structure of Organs• Small Intestine

• Duodenum – 1st segment, curves around pancreas, 12” long

• Jejunum – next section, 8 ft long

• Ileum – final portion, 10-12 ft long

• Absorption – digested food passes into bloodstream & on to body cells• Undigestible passes

on to large intestine

Structure of Organs

• Large Intestine (aka colon)• Chyme – semi-liquid

food• ~ 2” in diameter• Cecum – lower right

portion• Appendix – finger-like

projection off cecum• Rectum – last portion• Anus – external

opening

Accessory Organs

• Pancreas• Located behind stomach• Exocrine function –

secretes digestive enzymes• Also has endocrine function

• Gall Bladder• Small green organ, inferior

surface of the liver• Stores & concentrates bile

• Released when fatty foods are digested

Accessory Organs• Liver

• Largest organ in he body• Located below the diaphragm

(ULQ)• Connected to gallbladder & small

intestine by ducts• Functions:

• Produce & store glucose in the form of Glycogen

• Detoxify alcohol, drugs & other harmful substances

• Manufacture blood proteins• Manufactures bile• Store Vitamins A, D & B

complex

Digestion

• Bolus • soft, pliable ball • created from chewing & addition of

saliva • it slides down esophagus

• Peristalsis • wavelike motions, moves food

along esophagus, stomach & intestines

Digestion

• In the mouth…• Saliva softens food to make it easier to

swallow• PTYALIN in saliva converts starches into

simple sugar• In the stomach…

• Gastric (digestive) juices are released• Stomach walls churn & mix (mixture is

chyme)• Small amount of chyme enters duodenum

at a time – controlled by pyloric sphincter• Takes 2-4 hours for stomach to empty

Digestion

• In the small intestine…• Where digestion is

completed & absorption occurs

• Addition of enzymes from pancreas & bile from liver/gallbladder

Digestion• In the large intestine…

• Regulation of H2O balance by absorbing large quantities back into bloodstream

• Bacterial action on undigested food• Decomposed products excreted through colon• Bacteria form moderate amounts of B complex &

Vitamin K• Bacteria produce gas (1-3 pints/day…14 times a day)

• Feces – undigested semi-solid consisting of bacteria, waste products, mucous & cellulose

• Defecation – when lg. intestine fills, defecation reflex triggered.

Location of Parts and Function oral cavity (mouth)

physical digestion

pharynx common passage for digestion and respiration systems

tongue tasting positions food for ‘tooth work’

teeth physical digestion of food

salivary glands lubricate bolus, begin starch chemical digestion (salivary amylase)

epiglottis direct food ball into esophagus and not into trachea (the “wrong way”)

esophagus tube through which food passes into stomach

stomach physical digestion (churns) and chemical digestion (protein)

cardiac sphincter

muscular ring acts as valve to contain food in stomach (top)

duodenum

(top)1st 15 cm of sm. intestine bile duct, pancreatic duct enter here

pyloric sphincter

muscular ring; acts as valve to contain food in stomach

small intestine

chemical digestion of all foods, absorption of monomers

liver produces bile and maintains blood glucose

gall bladder

stores bile (emulsifies fats)

pancreas neutralizes pH (NaHCO3), secretes several enzymes

large intestine

absorption of H2O cultures E. coli

appendix ? protection from pathogens ? vestigial structure

rectum last 20 cm of large intestine anus undigested material passes out here

Digestive Disorders• Heartburn

• Acid reflux• Symptom – burning sensation• Rx – avoid chocolate & peppermint, coffee, citrus, fried or

fatty foods, tomato products – stop smoking – take antacids – don’t lay down 2-3 hours after eating

• Gastritis• Acute or chronic inflammation of the stomach lining

• Gastroenteritis• Inflammation of mucous membrane lining of stomach &

intestine lining. Usually caused by a virus.• Symps – diarrhea & vomiting for 24-36 hours• Complication - dehydration

Digestive Disorders

• Ulcer• Sore or lesion that forms in the mucosal lining

of the stomach. Bacteria is the primary cause.• Symptom – burning pain in the abdomen,

between meals & early morning, may be relieved by eating or taking antacid

• Colitis (Irritable Bowel Syndrome…IBS)• Large intestine inflamed• Symptom – episodes of constipation or diarrhea

Digestive Disorders

• Cirrhosis• Chronic, progressive disease of

liver• Normal tissue replaced by

fibrous connective tissue• 75% caused by excessive

alcohol consumption• Cholelithiasis (gallstones)

• May block bile duct causing pain

Digestive Disorders

• Diverticulosis• Little sacs (diverticuli) develop in

wall of colon• Most people over age 60 have this• When sacs become inflamed =

diverticulitis

Digestive Disorders

• Diarrhea• Loose, watery, frequent bowel movements

when feces pass along colon too rapidly• Caused by infection, poor diet,

nervousness, toxic substances or irritants in food

• Constipation• When defecation delayed, feces become

dry & hard• Rx – diet with cereals, fruits, vegetables

(roughage) & drinking plenty of fluids

Digestive Disorders

• Gingivitis• Inflammation of the gums

• Jaundice• Yellow color when bile pigment gets in

bloodstream• Caries

• Tooth decay (cavities)