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