The Digestive System
Salivary Glands Saliva: cleanses, dissolves food, moistens food (bolus), contains enzymes for starch breakdown (amylase) Slightly acidic pH 6.75-7.00
Palate Forms roof of the mouth Hard palate: rigid (palatine bones) Soft palate: skeletal muscle Uvula: closes off nasopharynx when we swallow
Tongue Skeletal muscle fibers Grips food when chewing Mixes food Filiform papillae: friction Fungiform and circumvallate papillae: tastebuds
Teeth -Lie in sockets (alveoli) -Mastication: chewing -Each tooth has a crown (exposed) and gingiva or gum (surrounds tooth) -Enamel: bears the force of chewing -Root: embedded -Dentin: bonelike-forms bulk of tooth -Deciduous teeth: baby teeth (milk) -Permanent teeth: 32 in a full set Gingivitis: tartar build up inflames gums Teeth
Alimentary canal (GI tract) Digests food Absorbs About 30 feet long
Digestive Process Ingestion Propulsion 1. swallowing 2. peristalsis Mechanical Digestion 1. chewing 2. mixing food with tongue 3. churning in stomach 4. segmentation (rhythmic local constriction of intestines (mixes food and increases absorption)
Digestion continues… Chemical digestion (enzymes) Absorption (small intestine) Defecation (elimination of indigestible substances via the anus)
Peritoneum Serous membrane Visceral peritoneum covers external surfaces of digestive organs Parietal peritoneum lines the body wall Serous fluid lubricates Mesentery is a double layer of the peritoneum-provides blood vessels, nerves, lymphatics, and holds organs together
Pharynx From mouth food passes through the oropharynx and then laryngopharynx (common passageways for food, fluids, and air) Mucosa covered skeletal muscle Bolus: ball of moistened food
Esophagus Food tube Collapsed when not involved with food propulsion
Stomach Temporary food storage tank Protein breakdown begins here Chyme: creamy food paste Rugae: longitudinal folds Gastric glands (parietal cells) secret HCl Chief cells produce pepsinogen-the presence of HCL helps convert it to pepsin to digest proteins Fundus Lesser curvature Greater curvature Body
Small Intestine Anatomy
Small Intestine Major digestive organ Digestion is completed here All absorption of nutrients occurs here 3 subdivisions: 1. duodenum: bile and pancreatic ducts about 10 inches long 2. jejunum: 8 feet long 3. ileum: 12 feet long Joins the large intestine at the ileocecal valve Villi and microvilli: increase surface area for absorption Pancreatic juices and bile from liver break down all classes of food
Liver Largest gland in the body 4 lobes Produces bile (bile salts and bilirubin-pigment) for lipid (emulsifies fat into a solution) digestion Liver Hepatitis: inflammation due to infection Cirrhosis: chronic inflammation of liver usually due to Toxins like alcohol and drugs –becomes fatty scar tissue
Gall Bladder Thin walled, green muscular sac Stores bile Found on the undersurface of the liver
Pancreas Accessory digestive gland Pancreatic juices breakdown all categories of foodstuffs (delivered to the duodenum)
Large Intestine Frames small intestine 6 meters Absorbs water from indigestible food residues Malabsorption: celiac disease - gluten Eliminates them from the body as semisolid feces Bacterial flora: help break down carbs and release gas – also synthesize B complex and K vitamins (clotting factor) Subdivisions: 1. cecum (appendix located here) 2. colon: ascending, transverse, descending 3. rectum: stores feces 4. anal canal: removal of feces
Piggy Guts