THE HUMAN DIGESTIVE SYSTEM

THE HUMAN DIGESTIVE SYSTEMGRADE 8Sir aaron rafael ranois f. san jose

QUESTIONWHAT HAPPENS TO THE FOOD ONCE DIGESTED?

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QUESTIONHOW LONG DOES IT TAKE TO DIGEST FOOD?

The meal you just ate embarks on an eighteen to twenty-four hour journey through your digestive systemand a lot of the activity takes place without you even being aware of it.3

THREE MAIN FUNCTIONSIngestion of foodBreakdown of food for cell absorptionEliminating undigested materials

DIGESTIVE SYSTEMIt is composed of different organs cooperating for food digestion.

TYPES OF DIGESTIVE ORGANSAccessory organs assist in food digestion. (salivary glands, liver, gallbladder, pancreas)Alimentary canal contains organs where food passes through (mouth, pharynx, esophagus, stomach, small and large intestines, rectum, anus)

QUESTIONWHERE DOES DIGESTION BEGIN?

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A. THE ORAL CAVITYIngestion is the process from which the body take in the food through the mouth for digestion, absorption and elimination.

A. THE ORAL CAVITYThe mouth or oral cavity is the first portion of the digestive tract or alimentary canal.

TYPES OF DIGESTIONChemical involves the action of enzymes and other chemical substances in the bodyMechanical involves the cutting, crushing or grinding of food using the teeth (mastication)

EXTERNAL TOOTH DIVISIONCrownNeckRoot

Crown visibleGingiva gumNeck between crown and root, found in gingiva11

INTERNAL TOOTH DIVISIONEnamelDentinPulpCementum

Enamel white outer part, hardest partDentin layer below enamel, made of cells that secrete calcium phosphate (substance found in enamel)Pulp soft inner layer where blood vessels and nerves are foundCementum firmly binds the roots to the gums and jawbone12

FOUR TYPES OF HUMAN TEETHIncisors (8 in adult)Cuspids (Canines)Bicuspids (Premolars) (8 in adult)Molars (12 in adult)Third molars (wisdom)

Canines tearingPremolars crushing, mashing, grindingMolars broader crown than premolarsWisodm may not be present in all humans, 18 y/o 4 in total13

FOUR TYPES OF HUMAN TEETH

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WISDOM TEETH

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THE PROCESSInitial chemical digestion depends on an accessory organ the salivary gland. Chemical digestion involves enzymatic action, which is accomplished through the saliva.

Saliva contains salivary amylase which digests carbohydrates16

SALIVARY GLANDSParotid gland lies in front of ear; empties saliva near the second upper molarSublingual gland lies under the floor of the mouth; empties saliva by numerous sublingual ductsSubmandibular gland lies deep in the mouth; empties saliva on either side of the lingual frenulum (small fold under the tongue)

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SALIVARY GLANDS

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B. PHARYNX AND ESOPHAGUSThe bolus is the end product of the food that has been chewed, partially digested, and lubricated by the saliva.

Bolus is now ready to be swallowed.The tongue pushes the bolus into the pharynx (air, food and water passage). Then food is delivered to esophagus.19

QUESTIONHOW COME THE FOOD ENTER THE ESOPHAGUS AND DOES NOT GO THE OTHER WAY? (RESPIRATORY TRACT)

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B. PHARYNX AND ESOPHAGUSA flap called epiglottis closes the air openings when food is swallowed. It prevents the bolus from entering the trachea and ensures food enters the esophagus.

The bolus in the esophagus keeps moving down by a rhythmic, involuntary action called peristalsis.21

C. THE STOMACHThe bolus passes through the stomach after leaving the esophagus. The stomach is a highly muscularized J-shaped sac that stores food and continues the digestion.

Stomach aka gut can hold upto 2 L of food23

C. THE STOMACHThe environment is highly acidic.Chief cells release pepsinogen (form pepsin once in contact with acid)Goblet cells produces mucus that lines up the cells

The lining of the stomach secretes gastric juices containing HClPepsin digests proteins25

C. THE STOMACHBolus

Chyme

Chymes breakdown more into pieces26

C. THE STOMACHSphincters prevent the stomach from leaking out gastric juicesCardiac sphincter near esophagusPyloric sphincter near s. intestine

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D. THE SMALL INTESTINEThe longest part of digestive tract.DuodenumJejunumIleum

Named such because of its diameter.7 meters long28

D. THE SMALL INTESTINEThe completion of chemical digestion depends on three accessory organs pancreas, liver and gallbladder.END OF FOOD DIGESTION!

Digestion is already completed.29

C. THE SMALL INTESTINEEnzymeDigestive organFunctionSalivary amylaseMouthBreaks down starches into simpler sugarsPepsinStomachBreaks down proteinsMaltase, lactase, sucroseSmall intestineBreaks down sugars into simpler moleculesPeptidaseBreaks down proteins into amino acidsTrypsin and chymotrypsinSmall intestine, pancreasContinue proteins breakdownAmylaseContinue starches breakdownLipaseBreaks down fats

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D. THE SMALL INTESTINEBolus

Chyme

Chyle

SEGMENTATION

The muscular walls of SI mix the intestinal juices, pancreatic juices, and chime through the process called SEGMENTATIONSI is the site for nutrient absorption31

D. THE SMALL INTESTINEThe final products are amino acids, monosaccharides, fatty acids and glycerol

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E. THE LARGE INTESTINEThe site where undigested materials are transported and water absorption happens.

LI aka COLON33

F. RECTUMThe site of feces formation and temporary storage of undigested food.

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G. ANUSThe site where feces are expelled out of the body.

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SOME COMMON DIGESTIVE DISORDERS1. Dental caries tooth decay or cavity. Characterized by demineralization and destruction of the different tooth layers (enamel, dentin, cementum).

Usually caused by the acid produced by the acid produced by the bacteria fermenting on the food debris left on tooth surface39

SOME COMMON DIGESTIVE DISORDERS2. Heartburn characterized by burning sensation in chest. It is caused by the reflux of acid from the stomach back to esophagus.

Vomiting feeling41

SOME COMMON DIGESTIVE DISORDERS3. Gastric ulcer (stomach ulcer) caused by H. pylori. The caustic effects of acid and pepsin reach the walls of the stomach and cause lesions.

Helicobacter pylori43

duodenum44

SOME COMMON DIGESTIVE DISORDERS4. Appendicitis inflammation of appendicitis. The result of obstruction of the inside space of appendix. The appendix then accumulates mucus and swells.

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SOME COMMON DIGESTIVE DISORDERS5. Diarrhea characterized by having three or more loose liquid bowel movements per day.

Caused by rotavirus, bacterial infections or toxins to name a few47