The Digestive System “alimentary canal”

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Overall Function Digestion is the chemical and physical breakdown of food into a form usable by cells.

Organs of Digestive System MAJOR ORGANS Mouth Oropharynx Esophagus Stomach Small intestine Large intestine Rectum ACCESSORY ORGANS salivary glands Tongue Teeth Liver Gallbladder Pancreas Vermiform appendix

Digestive Tract Also known as alimentary canal or gastrointestinal (GI) tract. It forms a tube that separates from digesting food from the body’s internal cavity.

Layers of GI tract Mucosa Muscularis Inner layer of the lumen (open space) & villi Submucosa Made of connective tissue, glands, blood vessels and nerves Muscularis Surrounds submucosa, smooth muscle that contains nerves that form part of the intramural plexus Serosa Outermost layer made of connective tissue

The Mouth Lips Cheeks Hard & soft palate Tongue When closed form the oral fissure Cheeks Formed by muscle and adipose tissue Hard & soft palate Uvula suspends from soft palate Tongue Muscle movements aid in mastication

The Mouth

Salivary Glands Pairs include parotids, submandibular, and sublingual Secrete ~1L of saliva per day Buccal glands in the mucosa lining produces a small amount of saliva

The Teeth Three main parts Deciduous teeth(20) are baby teeth Crown Neck Root Deciduous teeth(20) are baby teeth Permanent teeth(32) show up from 6-13 yrs

The Pharynx Deglutition is the act of swallowing a bolus, rounded mass of food and saliva from the mouth to the stomach.

The Esophagus ~10 inches longs Sits posterior to trachea and heart It is normally flatted in resting state Each end is guarded be a sphincter Upper esophageal (UES) Lower (cardiac) esophageal (LES) Esophageal hiatus is opening in diaphragm where esophagus passes When enlarged can lead to hiatal hernia GERD- gastro esophageal reflux disorder, severe acid reflux and indigestion caused by weakened LES.

The Stomach Located directly below the diaphragm Normally holds 1-1.5 L 3 parts Fundus (upper left) Body (central) Pyloris (lower) 2 sphincter LES(cardiac) Pyloric Esophageal hiatis fundus body pyloris

The Stomach Gastric Mucosa, lining of the stomach contain many folds called rugae and depression called gastric pits Cells in the stomach produce HCL and intrinsic factor Intrinsic factor binds to B12 molecules keeping them from being broken down so they can be absorbed in the sm. Intestines

The Stomach Gastric muscles, muscularis, is made of longitudinal, circular and oblique layers. This gives it strong grinding power.

The Stomach Overall Functions Secrete gastric juices and intrinsic factor Store partially digested food Churn food with digestive juices and move it into duodenun Limited absorption, alcohol, some H2O and some fats Release hormones that regulate digestive functions Destroy pathogenic bacteria with acidic pH

The Small Intestine ~6m in length 3 parts Duodenum- first section, shaped like a C Jejunum- 2.5m, begins with abrupt turn Ileium- last 3.5m Small projections called villi line the sm. Intestine. Each contain an arteriole, venuole and lacteal Microvilli present on the villi increase the surface area of intestinal wall

The Small Intestine Secretion of digestive enzymes and absorption occur in small intestine Small pockets at the base of the villi, called crypts, contain cells that reproduce rapidly These cells push up and constantly replace older cells that are shed

Large Intestine 1.5-1.8m 3 parts Cecum- first 5-8cm Colon Ascending Transverse Descending Sigmoid (s-shaped) Rectum17-20cm Anal canal has folds with a vein and artery Hemorrhoids are enlargement of those veins Anus is made up of two sphincters

The Large Intestines

Accessory Structures Vermiform appendix- thought to hold beneficial flora Peritoneum- serous membrane that lines abdominal cavity Mesentery- fan shaped part of peritoneum which attaches to small intestine Omentum- attached to greater curvature of the stomach and is laced with fat deposits

The Liver Weighs ~1.5kg Made of two lobes Left lobe is smaller Right lobe has 4 parts Liver is made of small units called hepatic lobules

The Liver Blood enters the lobules from the hepatic portal system to be “cleaned” The liver: Destroys old RBCS, bacteria Vitamins and nutrients are metabolized Toxins are absorbed and detoxified Bile formed collects in small bile ducts

Bile Ducts The right and left bile ducts emerge from under the liver to form the common hepatic duct The common hepatic duct joins with the cystic duct (gallbladder) to form the common bile duct Common bile duct empties into the duodenum

Function of the Liver Detoxify substance-alcohol, medicines Bile production Metabolize fats, proteins and carbohydrates Store substances- Fe, vitamins A, B12, D Bile salt released by liver aid in absorption of fats

Gall Bladder Main function is to store and concentrate bile Contain tiny folds of rugae that contract to secrete bile during digestion Jaudice is caused by a buildup of bile in the blood Cholelithiasis is the formation of gallstones

Pancreas Fish shaped textured organ that is exocrine and endocrine gland Rests below stomach on top of duodenum Exocrine portion secrete digestive enzymes that collect in the pancreatic duct, that joins the common bile duct Endocrine islets cells secrete insulin and glucagon directly into the blood