Digestive System- Anatomy

Alimentary canal- open tract of major organs through which food travels Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anal canal

Accessory organs- organs that aide in digestion process Salivary glands Tongue Teeth Liver Gallbladder Pancreas Vermiform appendix

Mouth/Oral Cavity- beginning of alimentary canal 3 major pairs salivary glands- secrete 1 liter of saliva per day Parotid: largest Submandibular: Wharton ducts beside frenulum Sublingual: below floor of mouth Secrete mucous/serous saliva to aid in digestion

Teeth Used for mastication/chewing– increases surface area of food for more enzyme access Deciduous= baby teeth-20 Permanent= adult – 32 Incisors- bite into food Canines/cuspids -tear Premolars- grind & crush Molars- grind & crush

3 Main Parts of Tooth 1. crown- exposed top covered with enamel= 97% calcified material dentin= softer, more elastic than enamel, yellow 2. neck- narrow, surrounded by gums and cementum 3. root- fits into jaw, anchors tooth, surrounded by cementum

Interior of tooth= pulp cavity Contains: connective tissue, blood, lymph, nerves

Swallowing After food leaves mouth it’s called a bolus- goes through pharynx Pharynx=throat Oropharynx= 2nd division of pharynx through which food is passed  connects to esophagus

GI tract- layers of gastrointestinal tract 1. Mucosa- mucous lining the interior 2. Submucosa- CT tissue with blood vessels

Layers of GI 3. Muscularis- muscle with plexus of nerves 4. Serosa- fibroserous layer, includes mesentery (later in GI)

Esophagus

Esophagus- beginning of GI proper 10 inches long- takes about 7 seconds for food to pass through to stomach Normally flat at rest—expands during peristalsis Lined with stratified squamous epithelium– resists abrasion

Stomach Fundus– goes above level of esophagus Body Pylorus Volume about 1-1.5 liters– large size after big meal interferes with diaphragm– located to left side 3 major divisions: Fundus– goes above level of esophagus Body Pylorus

Stomach Destroys most bacteria swallowed in food or with mucus from resp. tract Stores food, churns food Limited amount of absorption– some drugs, alcohol, some fats

Gastric Mucosa Lining with folds= rugae, and depressions= gastric pits Gastric glands below pits– secrete gastric juice Have 2 main secretory cells: 1. chief cells- secrete enzymes 2. parietal cells- secrete HCl and “intrinsic factor”– binds to vitamin B1 to protect it from HCl before intestine, aids in absorption

Gastric Muscle 3 layers of smooth muscle running at different angles--longitudinal, circular, oblique-- so it can contract multiple directions

Small intestine Villi located on folds called plicae Each villi has arteriole, venule, and lymph vessel and have “brush border”– microvilli on columnar epithelium Crypts- depressions where mitosis is rapid

Parts of Large intestine Cecum- 1st few cm—pouch which appendix attaches to Ascending colon- goes up right side where ileum attaches- ileocecal valve allows material in (1 way) Transverse-horizontal Descending-goes down left side Sigmoid- S curve, joins rectum Rectum- last few inches