Digestive(1).ppsx

The Digestive System Chapter 16 Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.  https://www.youtube.com/watch?v=YN_n 8WEHg5U Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Learning Objectives  Recognize the anatomy of...

The Digestive System Chapter 16 Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.  https://www.youtube.com/watch?v=YN_n 8WEHg5U Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Learning Objectives  Recognize the anatomy of the digestive system  List the functions of the digestive system.  List the structures of the oral cavity.  Describe the epithelial and muscle layers of the gastrointestinal tract.  Explain the process of peristalsis.  Name the types of teeth found in carnivores Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.  List the structures that make up the monogastric stomach and describe the function of each area.  List the segments of the small and large intestine and describe the general functions of each segment. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.  Mouth        Teeth Pharynx Esophagus Stomach Small intestines Large intestines Anus Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. The Digestive System   Digestive tract, gastrointestinal (GI) tract, alimentary canal, gut Tube that runs from the mouth to the anus; accessory digestive organs Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Species Variation    Requirements for digestion and absorption of foodstuffs varies depending on the diet of the animal.  Herbivores - plant-eating animals (cattle, sheep, goats)  Carnivores - meat-eating animals (cats)  Omnivores - animals that eat plant material and meat Monogastric animals - simple, single stomachs Ruminants - multiple mixing and fermentation compartments in addition to the stomach Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Digestive Tract Functions 1. 2. 3. 4. 5. Prehension (grasping) of food with the lips or teeth Mastication - mechanical grinding and breaking down of food (chewing) Chemical digestion of food Absorption of nutrients and water Elimination of wastes Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.      Digestive Tract Structure Listing layers from inner to outer Mucosa - lining of GI tract; epithelium and loose connective tissue Submucosa - dense connective tissue; may contain glands Muscle layer - outside the submucosa Serosa - outermost layer; thin, tough connective tissue. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Digestive Tract Structure  Mesentery Sheets of connective tissue Suspend digestive tube in the abdomen from the dorsal body wall  Contains blood and lymph vessels and nerves that supply the GI tract  Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Digestive Tract Musculature  Skeletal muscle - voluntary control Found in the mouth, pharynx, the cranial part of the esophagus, and the external anal sphincter  Allows the processes of chewing, mixing saliva with food, and initiation of swallowing  Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Digestive Tract Musculature  Smooth muscle Wall of the majority of the esophagus, the stomach, the small intestine, the large intestine, and the internal anal sphincter  Primarily arranged in circular and longitudinal layers   Contraction of circular muscle fibers narrows the tract  Contraction of longitudinal fibers shortens the tract Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Peristalsis    Circular muscle contractions Wavelike movement along the tract Propel digestive tract contents along the tube ahead of them Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Segmental Contractions  Periodic circular muscle contractions  Occur in different adjacent sites  Mixes digestive tract contents and slows their movement through Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Buccal Cavity Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Buccal Cavity    Lips, tongue, teeth, salivary glands, hard palate, soft palate, and oropharynx Lips may play role in prehension Salivary glands - produce saliva; usually three pairs with ducts that carry the saliva to the oral cavity 1. Parotid salivary glands - ventral to the ear canals 2. Mandibular salivary glands - ventral to the parotid glands at the caudal angle of the mandible 3. Sublingual salivary glands - medial to the shafts of Mosby theitemsmandible base and derived items © 2008just by Mosby, under Inc., an affiliate ofthe Elsevier Inc. Teeth    Mastication - chewing; physically break down food into smaller pieces Upper arcade - contained in maxilla and the incisive bones Lower arcade - contained in the mandible Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Teeth Shape  Carnivore teeth - more pointed on their occlusal surface; slightly curved toward back of mouth   Good for holding prey, tearing, cutting, shredding Herbivore teeth have flat occlusal surfaces  Good for grinding plant and grain material Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Types of Teeth  Incisors    Grasping teeth Most rostral teeth of upper and lower arcade Canines     Tearing teeth Located at the corners of the incisors Longer than other teeth Pointed at the tip Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Types of Teeth  Premolars     Cutting teeth Rostral cheek teeth Sharp points and surfaces in carnivores Molars     Grinding teeth Caudal cheek teeth Larger, flatter occlusal surfaces Used for grinding Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Teeth Terminology  Lingual –  Palatal –  Labial –  Buccal - Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Dental Formula  Represents the typical number of each type of tooth found in the upper and lower arcade  Tooth type designated I for incisor, C for canine, P for premolar, and M for molar Upper case for adult teeth  Lower case for deciduous teeth  Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Dental Formula  Ruminants have no upper incisors or upper canine teeth  Dental pad - flat thick connective-tissue structure on the maxilla opposite the lower incisors and canine teeth Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Dental Formula  Tooth type followed by two numbers separated by a slash mark or expressed as a fraction of one number over the other First number - number of teeth in half of the upper arcade  Second number - number of teeth in half of the lower arcade   Total number determined by summing all the numbers and multiplying by 2 Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Dental Formulas for Several Domestic Species Species Dental Formula Canine - puppy Canine - adult Feline - kitten Feline - adult Equine - adult Porcine - adult Bovine - adult Total Number of Teeth i3/3 c1/1 p3/3 28 I3/3 C1/1 P4/4 M2/3 42 i3/3 c1/1 p3/2 26 I3/3 C1/1 P3/2 M1/1 30 I3/3 C1/1 P3-4/3 M3/3 40 or 42 I3/3 C1/1 P4/4 M3/3 44 I0/3 C0/1 P3/3 M3/3 32 Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Table 11-1 Structure of Teeth  Pulp - center of tooth  Blood and nerve supply enter at the apex of the tooth root  Dentin surrounds and protects the tooth pulp  Cementum - hard connective tissue   Covers tooth root Helps fasten the tooth securely in its bony socket Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Structure of Teeth  Enamel - covers the crown of the tooth   Hardest, toughest tissue in the body Gingiva - epithelial tissue that composes the gums around the teeth Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Oral Cavity Functions 1. 2. Prehend the food Initiate mastication (mechanical digestion)  3. Initiate chemical digestion  4. Breaks food into smaller particles that increase the surface area available for exposure to the enzymes involved in chemical digestion Saliva - added to food as it is chewed; moistens, softens, and shapes food into a form that is more readily swallowed Prepare food for swallowing Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Esophagus  Transports swallowed material from oropharynx to stomach  Enters the stomach at an angle in cardia region   Surrounded by cardiac sphincter muscle As stomach expands, folds of the stomach against esophagus closes the lower end of esophagus   Reduces the risk for reflux In some species, the closure is strong enough to prevent reflux or vomiting (horse, rabbit) Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Monogastric Stomach  Five different areas 1. Cardia 2. Fundus 3. Body 4. Pyloric antrum 5. Pylorus Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. The Stomach  Functions storage of ingested food  mechanical and chemical breakdown of food  production of intrinsic factor for Vitamin B12 absorption in small intestine   Food leaves stomach in semi-liquid form = chyme Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. Monogastric Stomach    Cardia - opening from the esophagus Fundus - distensible blind pouch; expands as more food is swallowed Body - distensible middle section , is a large mixing chamber  Fundus and body contain numerous glands Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Monogastric Stomach  Pyloric antrum - acts like a pump  grinds up swallowed food; regulates hydrochloric acid  Glands  contain G cells - secrete gastrin Pylorus - muscular sphincter; regulates the movement of chyme from the stomach into the duodenum  Prevents backflow of duodenal contents into the stomach Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Gastric Motility  Each area of the stomach has different motor functions. Fundus and body relax with swallowing of food  Body of the stomach contracts to help mix food  Pyloric antrum increases contractions in response to swallowing; stimulates mixing, grinding, and propulsive contractions that move food toward the pylorus   Peristalsis also occurs in stomach and intestines Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Gastric Motility  Parasympathetic stimulation causes fundus to relax and increases contractions in the antrum   Parasympathetic stimulation involved in small intestinal motility, secretions, and blood flow Sympathetic stimulation can cause a decrease in motility - gastric atony  Sympathetic stimulation decreases blood flow Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Small Intestines  Divided into three segments: Duodenum  Jejunum  Ileum   Ileocecal sphincter   There is no clear demarkation between the three segments All three can perform the functions of the small intestines which are: Peristalsis  Absorption of fluids and nutrients  Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Small Intestines   Suspended from the body wall by mesentery duodenum   receives chyme through pyloric sphincter jejunum longest part  most chemical digestion and absorption occur here   ileum  empties into large intestine at cecum (horse), at colon (dog and cat), or at cecum and colon (ruminant and pig) Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. The Omentum A double layer connects the peritoneum that links the stomach to abdominal wall From Evans H, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, 2013, Saunders Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Structure of the Intestines  Inner mucosa Villi  Microvilli      Submucosal Muscle Serosa Thickness of the layers changes and is dependent on the segment of the intestine Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Small Intestine Mucosa  Mucosa - many folds and villi   Each villus contains thousands of microvilli (brush border) Microvilli - digestive enzymes and carrier molecules embedded in cell membranes Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Small Intestinal Peristalsis   Associated with the coordinated contractions of the longitudinal and circular muscle layers Stimulated by reflexes in response to dilation of a segment of the bowel  Independent of the parasympathetic nervous system Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Small Intestine Motility  Segmental contractions - mix intestinal contents; slow movement through intestines Help mix digestive enzymes with the intestinal contents  Bring digested materials into contact with the surface of the intestinal tract for absorption  Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. The Pancreas Endocrine function: pancreatic islets Exocrine function: groups of acini Acani functional unit of pancreas From Dyce KM, Sack WO, Wenseng CJG: Textbook of veterinary anatomy, ed 4, St Louis, 2010, Saunders. Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. Digestive System Functions of Pancreas  Exocrine fx:      Secretes bicarbonate into the duodenum   Production of: Amylase-digestion of carbohydrates Protease Trypsin-break down protein Lipase-digestion of fat Helps neutralize acidity of contents and maintains the pH in the duodenum needed for proper enzyme function Endocrine fx:   Produces insulin and glucagon Help regulate blood glucose levels Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Glandular Portions of the Pancreas  Endocrine portion = pancreatic islets contain several different cell types  beta cells secrete insulin  alpha cells produce glucagon    Exocrine portion = groups of acini enzymes are vital to digestion lipase, amylase, nuclease, protease  anticipation of food causes increase of secretions  Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. The Liver Largest digestive gland in the body multitude of functions – many not related to digestion Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. The Liver   Proteins made by hepatocytes enter bloodstream through pores in adjacent sinusoids Bile is excreted by hepatocytes Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. Digestive System Functions of Liver  Produces bile - bile acids, cholesterol, bilirubin  Secreted into bile ducts, into hepatic duct, then to gallbladder for storage; bile is involved in digestion process (fat)  Removes toxins & infectious agents that enter the body through the wall of the GI tract  Stores or metabolizes nutrients absorbed from the GI tract Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. More Functions of the Liver  Protein production  nearly all the plasma proteins, including albumin and blood clotting proteins  Conversion of amino acids into ketoacids  energy production  lipid synthesis Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. The Gallbladder   Located in the abdomen underneath the liver and near the pancreas, Concentrates and stores bile until needed    bile enters duodenum to help digest high fat meals Provides means for liver to excrete waste products even when animal is not eating Composition of bile bile salts  phospholipids  cholesterol  bile pigments  Mosby items and derived items ©©2008 byby Mosby, Inc., an affiliate of Elsevier Inc. Copyright 2016 Elsevier, Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Large Intestines  Function: Recover fluids and electrolytes  Store feces until evacuation     Varies greatly between species Carnivores Simple tubular organ Cecum  Ascending  Transverse  Descending  Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Rectum     Terminal portion of large intestine Nervous system control of motility and secretions is similar to that of the colon Numerous mucus-secreting glands lubricate and aid the passage of contents Sensory receptors detect stretching and stimulates the defecation response Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Anus  Composed of internal and external muscular sphincters Internal sphincter is under autonomic control  External sphincter that is under voluntary control    As the rectum distends, stretch receptors in rectum wall cause partial relaxation of the internal sphincter Anal mucosal receptors increase the sense or need for defecation Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Review  What are the functions of the digestive system.  Describe the epithelial and muscle layers of the gastrointestinal tract.  What is the process of peristalsis.  List the structures of the oral cavity.  List and give the locations of the salivary glands.  Name the types of teeth found in carnivores and describe the structure of teeth.  List the structures that make up the monogastric stomach and describe the function of each area.  List the segments of the small and large intestine and describe the general functions of each segment. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.