The Digestive System Chapter 11

Introduction to Digestive System AKA: Digestive tract, gastrointestinal tract, GI tract, Alimentary canal, gut System that takes complex food and breaks it down into simple nutrient molecules through process of digestion. After digestion takes place, nutrient molecules are absorbed into the bloodstream for use by the body’s cells. Tube with a LUMEN that runs from the mouth to the anus. Accessory digestive organs aid in the process of digestion and absorption. Salivary glands, liver, and pancreas

Species Variation Requirements for digestion and absorption of foodstuffs vary depending on diet ____vores - plant-eating animals ____vores - meat-eating animals ____vores - eat plant material and meat ______________ animals - simple (single) stomachs ______________ - multiple compartments

Function of GI tract 1. Prehension (grasping) of food with the lips or teeth 2. Mastication - mechanical grinding and breaking down of food (chewing) 3. Chemical digestion of food 4. Absorption of nutrients and water 5. Elimination of wastes

Digestive Tract Structure Four layers: _____________ –lining; consists of the epithelium and some loose connective tissue _____________ - beneath the mucosa; made of dense connective tissue. contains glands _____________- circular and longitudinal muscle layers _____________- outermost layer

Digestive Tract Structure ______________ - Sheets of connective tissue Suspends intestines from dorsal body wall Contains blood vessels, lymph vessels, and nerves that supply GI tract

Digestive Tract Epithelium ________ ________ epithelium Thick and tough Lines mouth, pharynx, esophagus, and anus ________ ________ epithelium From junct of esoph/stom to junct of rectum/anus Nutrients are absorbed through this thinner epithelium

Digestive Tract Musculature  Skeletal muscle - voluntary control Mouth, pharynx, cranial esophagus, ext anal sphincter Facilitates chewing, mixing saliva with food, initiation of swallowing, and control of defecation Smooth muscle Majority of esophagus, stomach, s. intestines, l. intestines, and internal anal sphincter Primarily arranged in circular and longitudinal layers Contraction of circular muscle fibers __________ tract Contraction of longitudinal fibers __________ tract

Peristalsis Circular muscle contractions Wavelike movement along tract ________ contents along digestive tract

Segmental Contractions Periodic circular muscle contractions Occur in different adjacent sites _______ digestive tract contents and slows their movement through tract

Salivary glands - saliva helps with evaporative _________, __________, and ___________; usually three pairs with ducts to oral cavity _________ salivary glands - ventral to ear canals __________salivary glands - ventral to parotid glands at the caudal angle of the mandible ____________ salivary glands - medial to the shafts of the mandible just under the base of the tongue SALIVARY GLANDS

Teeth Incisors, Canines, Premolars, and Molars are found in both herbivores and carnivores _______________ - chewing; physically break down food into smaller pieces Increases the surface area of the food that is exposed to digestive processes _________ arcade – teeth in maxilla and incisive bones _________ arcade – teeth in mandible

Teeth: Shape Carnivore teeth - _________ on occlusal surface; slightly curved toward back of mouth Good for holding prey, tearing, cutting, shredding Herbivore teeth - ________ occlusal surfaces Good for grinding plant and grain material

Types of Teeth Incisors _____________ teeth Most rostral teeth of upper and lower arcade Canines _____________ teeth Located at corners of incisors Longer than other teeth Pointed at tip ** Ruminants lack upper incisors AND canines. They have a _________ _____ instead**

Types of Teeth Premolars _____________ teeth Rostral cheek teeth Sharp points and surfaces in carnivores Molars ____________ teeth Caudal cheek teeth Larger, flatter occlusal surfaces

Species Dental Formula Total Number of Teeth Canine - puppy i3/3 c1/1 p3/3 28 Canine - adultI3/3 C1/1 P4/4 M2/3 42 Feline - kitteni3/3 c1/1 p3/2 26 Feline - adultI3/3 C1/1 P3/2 M1/1 30 Equine - adultI3/3 C1/1 P3-4/3 M3/3 40 or 42 Porcine - adultI3/3 C1/1 P4/4 M3/344 Bovine - adultI0/3 C0/1 P3/3 M3/332 Dental Formulas for Several Domestic Species

Dogs: 1 st Molar in lower arcade and 4 th Premolar in upper arcade Abscesses that form at the root of the apex of the upper carnassial tooth often break through the thin bone of the maxilla and begin to drain through the skin below the eye. Removing the carnassial teeth is difficult due to their deeply entrenched roots Carnassial Teeth