A & P of the Gastrointestinal Tract

By: Sara Anderson

Food!!!!!• It is necessary for existence

– Pssstt…and it’s darn good too!!!!!– What happens once we chew &

swallow it????? •The rest of the world may never

know..but YOU will!!!!!

Digestive Tract•AKA: Alimentary Canal

–Musculoskeletal membranous tube extending from the mouth to the anus

•Approximately 30 FEET long!!!

What is peristalsis?•Coordinated, rhythmic, serial contraction of smooth muscle that forces food through the digestive tract, bile through the bile duct, and urine through the ureter.•**Interesting note**

–During peristalsis, the tract shortens from approximately 30 feet to 15 feet!

Accessory Organs• These aid in the digestive tract

but AREN’T considered part of the digestive tract:– Teeth– Tongue– Salivary Glands– Liver– Gall Bladder– Pancreas

I’m hungry..let’s eat!!!•We should all know it all begins at our MOUTHS!

–TONGUE:•Muscular appendage•Aids in chewing, swallowing and formation of speech•Papillae contain taste buds

– BITTER, SWEET, SOUR AND SALTY

TEETH•The teeth shred, grind and breakdown

–Each tooth has a special function

•Incisors (center) for biting and cutting•Canines (posterior incisors) are pointed for tearing and shredding•Molars (rear) with 4 cusps are for mastication; crushing and grinding

SALIVARY GLANDS•3 Pairs:

–Parotid–Submandibular–Sublingual–Secrete saliva – 99% water with enzymes & mucus–1,000 – 1,500 mL of saliva every day–After food is ingested, continue to secrete saliva to cleanse the mouth

•Salivary amylase (ptyalin) - major enzyme – initiates carbohydrate metabolism•Lysozyme – destroys bacteria

ESOPHAGUS•Muscular, collapsible tube approximately 10” long

–Mouth to thoracic cavity–Esophageal hiatus to stomach–No digestion takes place here–Bolus: broken down food with saliva that moves to the stomach in 5-6 seconds

Bolus Transport

STOMACH•Located in the LUQ•When full it’s the size of a football•Holds approximately 1 Liter•Entrance- Cardiac sphincter

–Churns, contracts & compresses contents with gastric juices & water–Protein digestion begins

Hydrochloric acid •softens connective tissue of meat•kills bacteria •activates pepsin, which converts proteins into proteoses & peptones

•Mucin- protects stomach lining•Intrinsic factor- absorption of B12•Broken down into viscous semiliquid called CHYME •Exit- Pyloric sphincter

STOMACH

SMALL INTESTINE•90% of digestion •20 feet long •1” diameter•Starts at the pyloric sphincter and ends at the ileocecal valve•3 major sections

–Duodenum–Jejunum–IleumLacteals absorb metabolized fats

•Intestinal juices finish carb & protein metabolism•Bile breaks molecules into smaller droplets•Pancreatic juices

– break down proteins to amino acids–Dietary fats to glycerol & fatty acids–Starch to simple sugars

SMALL INTESTINE

LARGE INTESTINE•Cecum•Appendix•Ascending colon•Transverse colon•Descending colon•Sigmoid colon•Rectum•anus

LARGE INTESTINE•2” diameter, 5’ long•4 Major functions

–Completion of absorption–Manufacture certain vitamins–Formation of feces–Expulsion of feces**NOTE**No function for appendix is known as of today

•Bacteria–Changes chyme into fecal material by releasing remaining nutrients–Synthesizes Vitamin K–Produces some B-complex vitamins

•Remaining water & vitamins are absorbed into bloodstream through OSMOSIS

RECTUM• Last 8” of Large intestine• Fecal material is expelled• This is the desired outcome….

ACCESSORY ORGANS: THE LIVER•Largest glandular organ & one of the most complex•3 lbs•Divided into 2 lobes•15oo mL of blood are delivered to the liver every minute via the portal vein & hepatic artery•Bile

–Yellow-brown or green-brown color–Necessary for metabolism of fats

•500-1,000 mL/daily

•Many functions:–Manages blood coagulation–Manufactures cholesterol–Manufactures albumin (maintains normal blood volume)–Filters old RBC’s & bacteria–Detoxifying poisons (alcohol, nicotine, drugs)–Turns ammonia into urea–Main source of body heat–Stores back up glycogen–Activates Vitamin D–Breaks down nitrogenous waste–And that’s it!!!!!!!!!!

THE LIVER

ACCESSORY ORGANS: THE PANCREAS• Endocrine & EXOCRINE• 1,000 – 1,500 mL juice to aid in

digestion• Protease (trypsin), lipase

(steapsin), & amylase (amylopsin) digest proteins, fats and carbohydrates

• Empties through the duodenum in the papilla of Vater

• Contains sodium bicarbonate to neutralize hydrochloric acid

THE PANCREAS

Regulation of food intake!!•Hypothalamus

–2 centers to stimulate to eat and to STOP eating!!!!

•And THIS..is your stomach on too much good food!!!!!!!!!!!!!