Digestive system

Food substances are changed into Food substances are changed into forms that can be absorbed through forms that can be absorbed through

cell membranescell membranes

Basic divisions

Alimentary canalAlimentary canal - extends from mouth to - extends from mouth to anusanus

Accessory organsAccessory organs - release secretions into - release secretions into canal canal

Alimentary Canal

muscular tube, 9 meters longmuscular tube, 9 meters long Substances move through it by Substances move through it by peristalsisperistalsis Sphincter musclesSphincter muscles – circular muscles that – circular muscles that

control movement of food from one section control movement of food from one section to another to another

MouthMouth – mechanically reduces size of solid – mechanically reduces size of solid particles, mixes them with salivaparticles, mixes them with saliva

a.     Cheeks – musculara.     Cheeks – muscular b.     Lips – muscular, have sensory receptors c.     b.     Lips – muscular, have sensory receptors c.    

Tongue – muscular, mix food particles, taste, Tongue – muscular, mix food particles, taste, move to back of pharynxmove to back of pharynx

d.     Palate – roof of oral cavity, hard anterior, soft d.     Palate – roof of oral cavity, hard anterior, soft posteriorposterior

e.     Uvula – structure that hangs down in the back e.     Uvula – structure that hangs down in the back of the throat, seals nasopharynx while swallowingof the throat, seals nasopharynx while swallowing

Teeth – primary; 20(deciduous) permanent; 32Teeth – primary; 20(deciduous) permanent; 32

PharynxPharynx – connects nasal and oral cavities – connects nasal and oral cavities with larynx and esophaguswith larynx and esophagus

EsophagusEsophagus – straight, collapsible tube 25cm – straight, collapsible tube 25cm long, provides a passageway for substances long, provides a passageway for substances between pharynx and stomachbetween pharynx and stomach

StomachStomach – J-shaped; can hold 1 liter of – J-shaped; can hold 1 liter of food; inner lining is folded until distended. food; inner lining is folded until distended. Functions to receive food, mix it with Functions to receive food, mix it with gastric juicesgastric juices, begin digestion of proteins, , begin digestion of proteins, do a little bit of absorption, and move food do a little bit of absorption, and move food into small intestineinto small intestine

Small IntestineSmall Intestine – Completes digestion, absorbs – Completes digestion, absorbs products, and transports leftovers to large products, and transports leftovers to large intestine. Lined with intestine. Lined with villivilli – small fingerlike – small fingerlike projections that increase surface area.projections that increase surface area.

Large IntestineLarge Intestine – reabsorbs water and electrolytes; – reabsorbs water and electrolytes; forms and stores feces until defecation. Includes forms and stores feces until defecation. Includes the colon, rectum, and anusthe colon, rectum, and anus Feces Feces – materials that were not digested or – materials that were not digested or

absorbed, together with water, electrolytes, and absorbed, together with water, electrolytes, and bacteria. 75% water; color is due to bile bacteria. 75% water; color is due to bile pigments; odor due to bacteria and their pigments; odor due to bacteria and their productsproducts

Appendix – near the beginning of the colonAppendix – near the beginning of the colon

Accessory Organs

Salivary GlandsSalivary Glands – secrete – secrete salivasaliva; moistens ; moistens food particles, holds them together, and food particles, holds them together, and begins digestion of carbohydratesbegins digestion of carbohydrates

PancreasPancreas – secretes digestive enzymes that – secretes digestive enzymes that digest carbohydrates, fats, proteins and digest carbohydrates, fats, proteins and nucleic acids (exocrine function)nucleic acids (exocrine function)

LiverLiver – located below diaphragm, mostly on the – located below diaphragm, mostly on the right sideright side Metabolism of carbs, lipids, & proteinsMetabolism of carbs, lipids, & proteins Storage of substances (glycogen)Storage of substances (glycogen) Filtering of blood – esp. from intestinesFiltering of blood – esp. from intestines Destruction of toxic chemicalsDestruction of toxic chemicals Secretion of Secretion of bilebile (emulsifies fats) (emulsifies fats)

Gall BladderGall Bladder – pear shaped green sac attached to – pear shaped green sac attached to liverliver Stores bile between mealsStores bile between meals Concentrates bile by reabsorbing waterConcentrates bile by reabsorbing water Releases bile into small intestineReleases bile into small intestine

Sphincters

Esophageal – between esophagus and Esophageal – between esophagus and stomachstomach

Pyloric – between stomach and sm. Int.Pyloric – between stomach and sm. Int. Ileocecal – between large and sm. Int.Ileocecal – between large and sm. Int. Anal – 2 sets between rectum and anusAnal – 2 sets between rectum and anus