Chapter 11 - Digestive System Flashcards
What is prehension
The grasping of food
What are the functions of the digestive system
Prehension, ingestion, mastication, digestive tract , Absorption of nutrients and water, elimination of waste
What is ingestion
The taking in of food
What is mastication
Chewing of food
What is the digestive tract
Also known as G.I. tract, alimentary canal
List the layers of tissue that compose the wall of the G.I. tract from superficial to deep
- Serosa.
- Muscularis composed of longitudinal muscle layer and circular muscle layer
- Submucosa
- Mucosa
What is the serosa.
Serosa is a serous membrane which is the outermost layer of the wall of the G.I. tract
What is the serosa composed of
Epithelium, basement membrane, lamina propria
What is the function of the serosa
Protection and secretion, serous fluid reduces friction between layers
What is the muscularis externa composed of
Mainly composed of involuntary smooth muscle. Longitudinal and circular
What is the longitudinal smooth muscle do in the muscularis externa
Shorten tube
What does the circular smooth muscle layer of the muscularis externa do
Constricts the tube
What do the longitudinal and circular smooth muscle in the muscularis externa aid in
The aid in the propulsion of food from the esophagus to the rectum. By means of peristalsis and segmentation
What are sphincters
Thickened rings of circular smooth muscle which act like valves throughout the tract
Where is skeletal muscle found
Mouth, pharynx, cranial portion of the esophagus, and external anal sphincter
What is the skeletal muscle used for
Aids in chewing and swallowing, and defecation
What is peristalsis
Progressive contractions of smooth muscle propelling food down the G.I. tract
What is segmentation
Alternating contractions move food back-and-forth to mix and slow progress down in G.I. tract
What is the submucosa and what does it contain
The submucosa is a layer of loose connective tissue containing blood vessels, lymphatic vessels, follicles, nerves. Elastic fibers allow stretching and restoration of shape
What is the mucosa and what does it contain
The mucosa is a mucous membrane which is the innermost layer. Contains epithelium, basement membrane, lamina propria, muscularis mucosae
What are the functions of the mucosa
Secretion: mucus, digestive enzymes and hormones. Absorption of nutrients and water. Protection against disease
What are the two anal sphincter’s
Internal: internal anal sphincter that’s involuntarily controlled
External: external anal sphincter voluntarily controlled
What are two serous membranes in the body
Parietal layer which lines the cavities. Visceral layer which covers organs
Where is plural membrane located
Thoracic cavity
Where is the peritoneal membrane located
Abdominal cavity
What is the mesentery
Bands of peritoneal tissue that suspend the digestive tract from the body wall. Contain blood and lymphatic vessels and nerves
What are the digestive organs
Oral cavity, pharynx, esophagus, stomach, small intestine and, large intestine
What is the small intestine composed of
Duodenum, jejunum, ileum
What is the large intestine composed of
Colon, caecum, rectum, anus
What are the secondary organs
Salivary glands, pancreas, gallbladder, liver
What are the functions of the oral cavity
Location of prehension and ingestion. Beginning of mechanical breakdown and chemical digestion. Moistening/lubrication of food which aids in swallowing. Site of evaporative cooling a.k.a. Panting
What is the oral cavity lined with
Mucosa. Gums cover the jawbone
What are the structures of the oral cavity
Lips, tongue, salivary gland, teeth, hard palate, soft palate, oropharynx
What are the salivary glands
Paired exocrine glands with ducts that lead to oral cavity. Produces and releases saliva. Continuous production is increased or decreased by various stimuli
What does the saliva of non-carnivores contain
The enzymes amylase and lipase
What are the functions of the salivary glands
Lubricate and find food together, chemical digestion of carbs and fat, neutralization of bicarbonate stomach acid, evaporative cooling and flush away debris’s, reduce overgrowth of microbial populations
What are the functions of teeth
Grasping, tearing, mastication
Where is the upper arcade contained
Contained in the maxilla and incisive bones
Where is the lower arcade contained
Contained in the mandible
What is the occlusial surface
Where the teeth come together
What are the four types of teeth
Incisors, canines, premolars, molars
What is the purpose of the incisors
Grasping and snipping teeth. Most rostral teeth of upper and lower arcade
What are canines for
Tearing teeth located caudal to incisors. Longer than other teeth and pointed at the tip
What are premolars for
Cutting teeth known as the rostral cheek teeth. Has sharp points and surfaces in carnivores
What are the molars for
Grinding teeth known as caudal cheeks teeth. Contain longer, flatter occlusal surfaces
Describe the teeth shape of herbivores
Have flat occlusal surfaces that are good for grinding plant material
Describe the teeth shape of carnivores
More pointed at their occlusal surface, slightly curved caudally. Good for holding pray, tearing, cutting and shredding. They are also have carnassial Teeth
What are carnassial teeth
Found in carnivores, has a scissor like action. In the upper arcade it’s the last premolar. In the lower arcade it’s the first molar
What is the crown of the tooth
The top of the tooth
What is the apex of the tooth
Bottom of the tooth
What is the pulp of the tooth
Center of tooth
What is the Dentin
Surrounds and protects the tooth pulp
What is the cementum
The calcified layer covering the root of the tooth
What is enamel
Covers the crown of the tooth
What is the gingiva
The gums
What are brachydont
Low crown teeth. Carnivores and omnivores
What is hypsodont
High Crown teeth, continual growth which allows for eating of gritty abrasive material. Herbivores.
What is teeth floating in horses
Occlusal surfaces are smoothed with a file or a rasp
What is the pharynx
Divided into nasal and oral pharynx by soft palate. Tonsils located in the walls between mouth and pharynx. It carries water, food, gas. Muscles in muscularis assistant swallowing. Epiglottis directs food and water down digestive tract by covering larynx
What are the layers of the esophagus wall
Mucosa, submucosa, lumen, muscularis externa(circular/longitudinal) , adventitia.
What is the esophagus
The transport tube from the pharynx to the stomach. It is flaccid/collapsed when not transporting food. Muscularis is composed of upper one third skeletal muscle middle one third mixed and lower one third smooth
Describe the cardiac sphincter
We closure exception is rabbits and horses. Aids in diaphragm and filling of stomach. Mucous glands on both sides of sphincter to reduce damage by gastric acid
What are the predisposing factors of gastroesophageal reflux
Obesity, age, genetics, anesthesia
Describe gastroesophageal reflux
Inflammation which lead to ulcers which leads to perforation
What are the clinical signs of gastroesophageal reflux
Regurgitation, dysphasia, weight loss, evidence of pain
How do you diagnose gastroesophageal reflux
Endoscopy
What is the treatment for gastroesophageal reflux
Weight loss, drugs to reduce acid production
What is a hiatal hernia
Upper portion of stomach passes through the diaphragm. Either congenital or acquired. Esophagus does not close off when stomach fills with food
What is megaesophagus
Food accumulates in esophagus and or is regurgitated. Limited peristalsis, either congenital or acquired
What is the treatment for megaesophagus
More liquid diet, feed in the vertical position
What are the concerns with mega esophagus
Reduce nutrient intake, pneumonia due to aspirated food
What are cats and dogs digestive systems considered to be
Monogastric
What are rabbits pigs and horses digestive system is considered to be
Hindgut fermenters
What a goat and cows digestive system considered to be
Ruminant
What is the monogastric stomach and who has it
A stomach that has a single chamber. Carnivores, omnivores, equines
Which regions are the monogastric stomach divided into
Cardia, fungus, body, pyloric antrum, pylorus
What is the monogastric stomach lined with
Folds called rugae
Where is the lesser omentum located
Is anchored caudal to liver by lesser and greater Omenta
What is the Cardia
Opening from the esophagus. Has a cardiac sphincter which reduces reflux
What is the fundus
Distensible blind pouch. Expense as more food is swallowed, then changes shape closing off the esophagus
What is the body
Distensible middle section. Fundus and body contains numerous glands.
What do the gastric glands contain
Parietal cells and chief cells
What do parietal cells produce
Produced hydrochloric acid
What do chief cells produce
Produce the inactive enzyme pepsinogen
What happens when Pepsinogen meets hydrochloric acid
Pepsin is created
What did the mucous cells produce
Produce the protective mucus
What does the pyloric Antrum do
Grinds up swallowed food, regulates hydrochloric acid secretion in fundus and body
What do endocrine tissue in Antrum walls contain
G cells which secretes the hormone gastrin
What is the pylorus
Muscular sphincter which regulates the movement of chime from the stomach into the duodenum. Prevents backflow
What is pyloric stenosis
Hypertrophy of muscle reduces chime passage and causes vomiting
What are the motor functions of the fundus and body
They relax with swallowing of food to allow filling
What is the function of the body of the stomach
Contracts to mix food
What is the function of the pyloric Antrum
Increases contractions in response to swallowing
What is the peristalsis in the stomach and intestine controlled by
Controlled by parasympathetic branch. The Vegas nerve. Trigger is hormones, stretch receptors
What is colic in horses
Abdominal pain which is the leading cause of death
What are some causes of colic and horses
Stress, rapid diet change, stabling, dehydration, ulcers, parasites
The different forms of colic
Gas colic, impaction, spasmodic
What are the symptoms of colic
Discomfort, sweating, rolling, wanting to lay down, kicking flank, absence of got sounds
What is the treatment for colic and horses
Pain relief, nasogastric intubation and surgery
What does the hormone gastrin do
Inhibits muscle activity of the fundus to allow for filling
What is the enterogastric reflex
Distention of the intestine lines or increased acidity in the duodenum inhibit stomach contraction. Delays gastric emptying to allow more time for digestion
What does the hormone secretin do
Hormone released from duodenum in response to excess stomach acid in small intestine. It can cause fundus to relax and inhibit peristalsis of the body and the antrum of the stomach to slow gastric emptying
What does the hormone cholecystokinin do
Hormone released from duodenum in response to large amounts of fats or protein in the duodenum. Decreases gastric contractions to slow emptying
What are the different gastric secretions
Pepcinogen, intrinsic factor, hydrochloric acid, mucus, bicarbonate ions, gastrin
What is Pepcinogen
Secreted by chief cells. Precursor for the enzyme pepsin which hydrolyzes proteins
What is the intrinsic factor
Secreted by parietal cells, required for vitamin B12 absorption by small intestine time in some species. Vitamin B 12 is important to nervous systems development and blood formation
What is mucus
Complexes substances, mucin is a protein produced by goblet cells. Provides a coating for the stomach against acidic gastric environment. Must be secreted continuously. Reduction in mucus coat can lead to gastric ulcers
What is the bicarbonate ion
Alkalinizes the mucus
What is hydrochloric acid
Secreted by parietal cells as separate ions. Low pH inhibits gastrin release. Receptors on parietal cells for gastrin histamine and acetylcholine involved in regard in regulation of H+ and cl- secretion. Selectively blocking one of these receptors decreases the production of stomach acid
What are prostaglandins
Local regulators released by various tissues with a variety of actions. Initiation of inflammation , regulate estrous cycle, vasodilation or bronchial dilation. In initiation of inflammation and vasodilation inhibits gastric release. It stimulates the gastric glands to produce the bicarbonate ion. it enhances blood flow to the stomach and aids in repair of mucosa by regulating the activity of Macrophages and mast cells
What are NSAIDs
Nonsteroidal anti-inflammatory drugs
What do NSAIDs do
Reduces beneficial effects of prostaglandins on gastric mucosa. Can lead to gastritis, gastric ulcers and perforation
Describe the ruminant stomach
For chambers and three fore stomachs, reticulum, rumen, omasum. The true stomach is abomasum
What is rumination
Repeated regurgitation and swallowing of food. Adaptation for herbivorous diet
What is the reticulum
Smallest, most cranial compartment and is separated from the rumen by the ruminoreticular fold. Continuous muscular wall so compartments contract together. The lining is composed of honeycomb folds which increase surface area. Location of hardware disease
What is hardware disease
Sharp objects are consumed and become lodged in the reticulum and can pierced through stomach wall can cause pericarditis
What is the treatment of hardware disease
Oral administration of large magnets, also given product preventatively. Magnets remain in reticulum for life
What is the rumen
Large fermentation vat which is lined with finger like papilla. Series of muscular sacs partially separated by long folds of rumen walls called pillars. Pillars aid in mixing and stirring of rumen contents
What is reticuloruminal contractions
Allow partially digested plant food to be regurgitated. Allow built up carbon dioxide or methane gas to be expelled from the Rumen
What is the rumen
Site of fermentation. Anaerobic cellular respiration
Describe the anaerobic cellular respiration which occurs in the rumen
Microbes Convert cellulose into simple sugars then convert them to VFA. Proteins also digested and converted to VFA or nh3. microbes form proteins and amino acids used by ruminants. Ruminants absorbs VFA in Omasum and metabolizes them back into glucose or fats
What is the omasum or abomasum
Reticulorumen contractions move ingested material into the abomasum Muscular organ with many muscular folds. Mechanically breaks food particles down further. Absorbs VFA and water. Removes B+ carbonate ions
What is the Abomasum
True stomach which is located ventrally. Functions much the same as a monogastric stomach
What is a displaced abomasum
Abomasum is loosely anchored in abdomen. Most common after calving or if it fills with gas.
What is the treatment for a displaced abomasum
Surgery or rolling cow on her back
Describe newborn ruminant digestion
G.I. track functions primarily as a monogastric digestive system. Rumen and reticular are nonfunctional at birth. Bypassed by Reticular groove carrying material from esophagus to Abomasum. Rate of development of the rumen and reticulum are affected by type of diet. Milk versus grain
Describe the small intestine
The site of chemical digestion and nutrient absorption
Describe the duodenum
First short segment that leaves the stomach. Separated from the stomach by the pyloric sphincter
Describe the jejunum
The longest portion of the small intestine
Describe the ileum
Separated from the colon, the large intestine by the ileocecal sphincter
Describe the ileocecal sphincter
It regulates the movement of materials from the small intestine into the colon and cecum. Parasympathetic stimulation increases activity
Describe the small intestine mucosa
Lined with folds called villi. Epithelial cells, Enterocytes have a microvilli brush border that has a few days of life. It’s job is to absorb nutrients. The folds contain blood vessels and lymph lacteals which absorb fats
What is an intestinal crypt
Invagination’s of mucosa at the base of each villus, containing a variety of cell types
What do stem cells do in the intestinal crypts
They produce new cells to replace villi cells, enterocytes
What do goblet cells do
Produce and secrete mucus
What do Entero endocrine cells do
Produce and secrete hormones such as CCK or secretin
What do paneth cells do
Produce antimicrobial peptides part of innate immune system
What is acute diarrhea or porcine epidemic diarrhea
Highly contagious viral disease causes destruction of mucosal cells, death of microflora of the large intestine. Due to pathogen and sudden diet change, drug therapy. Example parvovirus, panleukopenia virus
What are the two methods of motility in the small intestine
Peristalsis and segmentation.
What are peristalsis and segmentation considered
Coordinated contractions of muscularis externa
What is diarrhea sometimes due to
Decreased segmentation, not increased peristalsis. Some antidiarrheal drugs act to increase segmentation.
What signals the peristalsis and segmentation to start
Reflexes in response to stretching. CCK and PGs may also stimulate intestinal motility
Describe small intestine digestion
Small molecules from stomach or absorbed. Electrolytes, water and vitamins. Larger molecules require chemical digestion such as carbohydrates, proteins and peptides and fats
What does chemical digestion involve
Enzymes in the lumen of the intestine. And enzymes associated with the microvilli membrane
Describe carbohydrate digestion for a polysaccharide
Enzymes released by pancreas. Amylase. Digestion occurs in lumen of duodenum
Describe chemical digestion for disaccharides
Enzymes are in microvilli cell. membrane. Monosaccharides transported into Enterocytes then into capillaries. Enzyme production is influenced by age and diet
Describe protein digestion in general
In the stomach Pepcid digest some proteins and turns them into smaller polypeptides
What are the pancreatic proteases in protein digestion
Polypeptides are turned into smaller polypeptides by five pancreatic proteases, trypsin, chymotrypsin, elastase, aminopeptidase, carboxypeptidase
What is the peptidases in protein digestion
The peptidases and brush border make smaller peptides turn into tripeptides dipeptides And amino acids that are then absorbed by Enterocytes
What is the first step of fat digestion
Mechanical breakdown by agitation in pyloric Antrum, breaks down fat globules, triglycerides, into smaller droplets equals emulsification.
What is the second step in fat digestion
Bile coats the fat droplets in duodenum to preserve emulsification, and allow them to be water-soluble
What is the third step in fat digestion
Pancreatic Lipases turn triglycerides into glycerol, fatty acid, monoglyceride which is glycerol and a fatty acid. Then the small molecules called micelles are absorbed by Enterocytes. Fat soluble vitamins ADEK often incorporated into micelles and absorbed. They then enter lymph lacteals
What is the first step of digestion in the large intestine of herbivores
The caecum is a blind sac at ileocecal Junction which is the site of microbial digestion. The colon has some microbial digestion and all species. the rectum leads to the Anus. No enzymes released, all species have large microbial population, most important to nonruminant herbivores such as hindgut fermenters
Describe the first step of digestion in the large intestine of carnivores
The caecum is underdeveloped and largely nonfunctional. The colon is simple and tubular. It is the site of peristalsis and segmentation to form and move feces. Microbial flora assist in the production of vitamins.
Describe digestion in the large intestine of hindgut fermenters
Nonruminant herbivores such as horses and rabbits and omnivores such as rodents and swine. Large caecum and colon. both are hindgut. Both are the fermentation site similar to fermentation in ruminants.
What are bends in tracts called
Flexures. They’re areas of potential obstruction. Impaction colic.
Describe the 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
Describe the anus
Composed of internal and Extertal muscular sprinters. As was the rectum distends, stretch receptors in the rectum wall cause partial relaxation of the internal sphincter. Perianal trauma can damage muscle and nerves causing fecal incontinence
Describe the digestive system functions of the pancreas
Production of pancreatic enzymes such as amylase, proteases and lipase
Secretes bicarbonate into the duodenum which helps neutralize acidity of gastric chime and maintains the pH of the duodenum needed for enzyme function. Produces insulin and glucagon which helps regulate blood glucose levels
Describe the digestive functions of the liver
Produces bile which is stored in gallbladder. In rodents and horses there’s no gallbladder. Removes and neutralizes toxins that enters the body through the G.I. tract. Stores or metabolizes nutrients absorbed by the G.I. tract. Site of glycogenesis, glycogenolysis, gluconeogenesis.
