Digestive System

A. Functions a. Break food down into usable nutrients

Functions b. Absorb nutrients into the bloodstream

Functions c. Rid body of indigestible remains

Accessory Digestive Organs Two Main Groups: Alimentary Canal Accessory Digestive Organs

B. Alimentary Canal (gastrointestinal tract) continuous tube from mouth to anus

Alimentary Canal a. About 9 meters long in cadavers

Alimentary Canal b. Job – breaks down food and absorbs nutrients c. Organs – mouth, pharynx, esophagus, stomach, small intestine, and large intestine

C. Accessory Digestive Organs a. Job – aid in the breakdown and absorption of nutrients b. Organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas

Digestive Processes Ingestion Propulsion Mechanical Digestion Chemical Digestion Absorption Defecation

Ingestion A. Taking food into the body

Propulsion B. Moving food through the GI tract a. Swallowing – voluntary b. Peristalsis - involuntary

Peristalsis Wave-like muscle contractions that move food through the GI tract So powerful it defies gravity

C. Mechanical Digestion Breaks food into smaller pieces a. Chewing – mouth b. Churning – stomach c. Segmentation – small intestine

Segmentation Squeezing and mixing food with digestive juices in segments

D. Chemical Digestion Enzymes break food down into smaller, simpler molecules

E. Absorption Movement of vitamins, minerals, water from GI tract to blood Mostly happens in small intestines

F. Defecation Eliminating indigestible substances from the body a. Feces – solid waste matter

Organs of the Digestive System

A. Mouth – oral cavity, where ingestion occurs

Mouth a. Lips and Cheeks – keep food inside the mouth while chewing

Mouth b. Palate – roof of the mouth

Hard palate rigid surface helps with food breakdown during chewing

Soft palate initiates swallowing, contains uvula

Uvula Closes nasal passage when swallowing to keep food out

Uvula

B. Teeth a. 32 permanent b. 20 deciduous (baby teeth)

Teeth c. Incisors – 8, for biting, cutting, shearing

Teeth d. Canines – (cuspids) 4, for stabbing and tearing

Teeth e. Premolars – (bicuspids) 8, for crushing

Teeth f. Molars – 12, for crushing and grinding

Wisdom Teeth – 3rd molars

Wisdom Teeth Extraction

Teeth

Gingiva g. Gums that surround base of teeth

Problems Gingivitis Periodontal Disease

So take good care of them…

C. Tongue Forms base of mouth, highly muscular

a. Jobs of Tongue Mixes food with saliva Speech Taste Swallowing

Bolus b. Ball of food that is ready to be swallowed

Frenulum c. Membrane that attaches tongue to floor of mouth

Tongue-tied

Papillae d. Peg-like projections that cover the tongue surface

Taste buds e. Found in grooves, detect taste

Tastes – Sweet, Salty, Sour, Bitter, Umami (steak and cheese)

D. Salivary Glands Produce saliva to begin chemical digestion

3 pairs Parotid – large, in front of ear Submandibular – along the jaw Sublingual – below the tongue

Saliva b. Made of water, digestive enzymes, mucus, and antibacterial agents

Mouths are covered in bacteria

E. Pharynx - back of the throat a. Connects oral cavity to esophagus Both Respiratory and Digestive Systems

What can you see?

F. Esophagus Long muscular tube that carries food to the stomach

Esophagus a. About 10 inches long b. Longitudinal folds collapse when empty

Esophagus

Esophagus

Esophagus

Diaphragm c. Esophagus passes through hole in diaphragm to reach the stomach

Lower Esophageal Sphincter d. Acts as a valve to keep food and juices in the stomach

Heartburn LES is relaxed and allows stomach acids back up into the esophagus

Other Damage Barretts, Acid reflux, Ulcers, Cancer