Gastrointestinal SystemGastrointestinal System

Structure and Function

Gastrointestinal systemGastrointestinal system

Where does digestion Where does digestion occur?occur?

Begins in the mouth

Ends at the anus

Types of DigestionTypes of DigestionMechanical

digestion: mastication (teeth, tongue)

Chemical digestion: salivary glands secrete ptyalin; CHO digestion

The MouthThe Mouth

Mechanical: mastication

Chemical: saliva contains “ptyalin” that begins breakdown of carbohydrates

The TongueThe Tongue

Moves food around

Saliva that is produced coats and lubricates the food for easier chewing and swallowing.

Taste buds occur in different areas of tongue: bitter, sweet, salty, sour

The TeethThe Teeth

Chew and break food down into small morsels

The Gingivae (gum) support and protect the teeth

The Salivary GlandsThe Salivary Glands Located in and around

the mouth and throat. Saliva is secreted into

the oral cavity by three pairs of salivary glands: ◦ Parotid salivary

glands – largest salivary gland, swell during an attack of mumps

◦ Submandibular gland - about the size of a walnut, its secretions contain both mucin and ptyalin

◦ Sublingual glands – the smallest, secrete mainly mucus and contain no ptyalin

The PharynxThe PharynxServes as a

passageway for food (swallowing)and air

When a person swallows the back of the tongue helps close the epiglottis which directs food away from the larynx and into the esophagus.

The PeritoneumThe PeritoneumTwo layered membraneLines the abdominal cavityParietal layer: lines entire abdominal cavityVisceral layer: covers the outside of each

abdominal organMesentary: attached to posterior abdominal

wall; small intestines anchored hereGreater Omentum: 2 layers of peritoneum

containing fat; hangs over abdominal organs

The EsophagusThe Esophagus Connects the pharynx

to the stomach Carries food, liquids,

and saliva from the mouth to the stomach

When food (bolus) is swallowed it enters the upper portion of the esophagus

The walls of the esophagus have four layers: the mucosa, submucosa, muscular, and external serous layer

The StomachThe Stomach Muscular organ

located in LUQ Chemical and

mechanical digestion continues; semisolid solution “chyme”

Secretes HCl: aids in protein breakdown, kills bacteria, & aids Fe absorption

Secretes intrinsic factor: vitamin B12 absorption

Secretes “lipase”: fat digestion

Rennin: infant stomachs – milk digestion

Contains rugae for expansion

Cardiac sphincter: separates esophagus and stomach

Pyloric sphincter: separates stomach and duodenum

The Stomach Continued…The Stomach Continued…Secretes “lipase”: fat

digestionRennin: infant

stomachs – milk digestion

Contains rugae for expansion

Cardiac sphincter: separates esophagus and stomach

Pyloric sphincter: separates stomach and duodenum

The StomachThe Stomach

The Small IntestineThe Small IntestineDuodenum: first 10 inchesJejunum: middle sectionIleum: terminal sectionEntire section is approximately 20 ft.

in length and 1 inch in diameterAbsorption of nutrients (CHO, fats,

proteins, vitamins, minerals)Digestion completed

The DuodenumThe Duodenum Bile and pancreatic juices enter here; calcium, fat,

and iron digestion/absorption begin

The JejunumThe JejunumMiddle sectionFats, proteins, CHO absorption

The IleumThe IleumTerminal end of small intestineVitamin B12 and bile salts absorbed

hereSeparated from large intestine by

ileocecal valve or cecumDigestion is completed in small

intestineVilli and microvilli: fingerlike

projections on inside of small intestine; increase surface area for absorption

The Villi and microvilliThe Villi and microvilli

Nutrient absorptionNutrient absorptionVilli contain blood capillaries to

absorb sugars and proteinsLacteals, in the villi, absorb fats

The Large Intestine The Large Intestine Approximately 5 – 6 feet longSeparated from small intestine

by ileocecal valveForms framework around small

intestineAbsorbs waterEliminates wasteContains bacteria that produce

vitamin K and B12

The Large intestineThe Large intestineAscending colonTransverse colonDescending colonSigmoid colonRectum: stores

solid wasteAnus: terminal

opening of GI tract

The Vermiform appendixThe Vermiform appendixSmall blind pouch located at

ileocecal valveContains lymphatic type tissueMay aid in infection control

The LiverThe LiverLocated in RUQMakes bile for fat

breakdownStores sugar in

form of glycogenStores Fe and fat

soluble vitaminsProduces clotting

factorsDetoxifies harmful

substances

The GallbladderThe Gallbladder

Located beneath liver

Stores bile and releases it when fat enters duodenum

The PancreasThe Pancreas Located behind

stomach in LUQ Produces enzymes for

digestion Amylase: breakdown

sugar Trypsin, chymotrypsin:

breakdown protein Lipase: breakdown fats Produces hormone

insulin Insulin needed for

sugar to enter cells

Digestive systemDigestive systemGI tractStarts with

mouth and ends with anus

Chemical and mechanical digestion