Exam 4 Flashcards
What is digestion
The part of the process where large molecules are broken down into their smaller components and can be absorbed at a molecular level
What are the 2 breakdown processes of digestion
Mechanical and chemical
What are the 4 tissues layers of the GIT
Mucosa, submucosa, muscular, and serosa
What is the mucosa layer
The most inner layer that is covered by epithelium, a basement membrane referred to as the lamina propria, and a muscularis mucosae that aids in contraction
What composes the submucosa layer of the GIT
Dense connective tissue
What is the muscular layers of the GIT
Smooth muscle layers responsible for peristalsis
What is the serosa layer of the GIT
Makes contact w/ the serosal layer of the peritoneum
What are the 2 systems send signals to the GIT
The CNS and the endocrine system
What is the brain of the gut
The enteric nervous system that has an intrinsic endocrine/paracrine component
What does the Brain of the Gut do
Controls motor and secretory functions of GIT and is influenced by the ANS
What are the 2 aspects of the Brain of the Gut
The submucosal plexus and myenteric plexus
What is the submucosal plexus
Aka Meissner’s plexus is in the submucosa and controls secretions such as digestive enzymes and blood flow
What is the myenteric plexus
Aka the Auerbach’s plexus is btw the circular and longitudinal layers of smooth muscle controls movement thru local flexes affecting the contraction of muscle tissue and peristalsis
Where is the soft palate
Starts right behind the hard palate and goes all the way down to the epiglottis and larynx
What is the oral fissure
Opening into mouth marked by the lips
What is the philtrum
Cleft dividing upper lip
What is another word for whiskers
Vibrissae
What is the hard palate composed of
The palantine, maxillary, and incisive bones
What is the soft palate comprised of
Muscle and CT
What is the crown of a tooth
The part of the tooth you can see
What is the root of the tooth
The portion berried beneath the gum line
What is the apex of the tooth
The bottom tip of the root where the pulp, blood vessels, and nerve root enter the tooth
What is the pulp
The living tissue of the tooth is equivalent to the bone marrow of the tooth
What is the occlusal surface
The free surface of the tooth
What is the vestibular surface
The surface next to the oral vestibule brokedown into the labial and buccal surfaces
What is the oral vestibule
The space btw lips, cheeks, and outer surface of teeth
What is the oral cavity
Bordered by inner surface of teeth, hard palates, and soft palates
What is the labial surface
the vestibular surface of the incisor and canine teeth
What is the buccal surface
Vestibular surface of the premolars and molars
What is the lingual surface
Surface next to the tongue
What is the contact surface
Surfaces in contact w/ neighboring teeth brokedown into mesial and distal surfaces
What is the mesial surface
Is the contact surface towards the midline in the arcade
What is the distal surface
Is the contact surface further away from the midline
What are the 2 classifications of teeth
Brachyodont and hypsodont
What are brachyodont teeth
The incisor teeth found in carnivores, humans, pigs, and ruminants, small crowns, well developed roots, and do not grow continually
What are hypsodont teeth
Found in horse’s incisors and cheek teeth, boar’s canine teeth, rodents, and lagomorphs, large reserve of crown beneath gingiva, and grow continually
What are the 2 types of hypsodont teeth
Radicular and aradicular
What are radicular hypsodont teeth
Apices of roots remain open for a long time, apices eventually close and stop growing, and found in cheek teeth of horses
What are aradicular hypsodont teeth
Lack of true root, grow continuously throughout life of animal, and found in lagomorphs and some rodents
What is enamel
Thin layer over the surface of the tooth, devoid of organic material, made of calcium phosphate and carbonate apatite crystals, hardest substance in the body, covers only the crown in brachydont teeth, and covers the body but not the root in hypsodont teeth
What is the cementum
Covers only the roots of brachyodont teeth and covers roots and crown in hypsodont teeth
What is dentin
Forms the bulk of the tooth under the enamel, similar to bone in composition, and surrounds the pulp cavity
What is the pulp cavity
Center of tooth where the nerve and vessels are located
What is the periodontal membrane
Dense fibrous CT that connects the wall of the alveoli and tooth’s cementum this is the bain of every vet’s existence when extracting teeth
What are deciduous teeth
Small whiter teeth that are present in the jaw at birth and erupt thru gums at different times depending on species
What is heterodont dentition
Numbered 1-4 in order incisors, canines, premolars, and molars
What are incisors for
Grabbing/nibbling
What are canines used for
Tearing/shearing
What are premolars used for
Shearing/grinding
What are molars used for
Grinding
Will cats and dogs have the same amount of teeth that they were born w/
No they are born w/ less teeth then what they have as adults
How are deciduous teeth labeled on a dental formula
W/ lower case letters
What of the only type of tooth that does not have deciduous teeth
Molars
What is the triadan system
First broken up into quadrants 100s upper right, 200s upper left, 300s lower left, and 400s lower right then start counting at the midline and count back
What are teeth landmarks
Canines are always 04’s, largest/last premolar is always 08’s, and 1st molar is always 09’s
What teeth are cats missing
All 05’s and now lower 06’s
What is the apex of the tongue
The flap that lifts up
What is the body of the tongue
Attached to body of mouth
Where is the root of the tongue
Back by the larynx not palatable unless choking the animal
What is the tongue comprised of
Muscle tissue
What is found on the dorsal surface of the tongue and is more noticeable in cats
Papillae
What are the functions of the papillae
Mechanical such as grooming and moving food into the pharynx and specialized functions such as taste sensations, pain, temperature, touch, and thermoregulation thru panting
What is saliva
Deposited into oral cavity via ducts, production varies depending on species, and can be watery, viscous, or mixed depending on the composition
What can saliva be composed of
Mainly water, but also protein, glycoproteins, antibodies, organic molecules, electrolytes such as salivary bicarbonate, and enzymes like lysozyme an antibacterial and amylase like digest starch for carbs
What are the functions of saliva
Lubrication, antibacterial action, pH regulation, thermoregulation, and enzymatic digestion
What are the 4 main paired salivary glands
Parotid, mandibular, sublingual, and zygomatic
What is the esophagus
A muscular tube connecting the caudal pharynx to the cardia of the stomach is lined w/ folded mucosa and has a tunica muscularis w/ 2 layers
What are the 2 layers of the esophagus’ tunica muscularis
Circular and longitudinal
What species have a combination of smooth and striated muscle in their esophagus
Horses and pigs
Where does the esophagus pass through the diaphragm
The hiatus
Where is the esophagus found on the neck
To the left of the midline
What are the 2 parts of the connecting peritoneum
Mesentery and omentum
What is the mesentery
Redundant portion of the visceral peritoneum holding them to the caudal portion of the abdominal cavity
What is the omentum
Large adipose tissue surface that covers the intraperitoneal organs
Where are kidneys located
Tucked away in the retroperitoneum space
What is the lesser omentum
Lesser curvature of stomach connected to duodenum and liver
What is the greater omentum
Greater curvature of stomach connected to abdominal wall
What happens when there is trauma to organs covered by omentum
The omentum travels to the organ and surrounds it providing more vascularity to the area to protect other organs and tissues around the trauma
What is the function of the stomach
Storage of ingested food, mechanical/chemical breakdown of food, and production of intrinsic factor for vitamin B12 absorption in SI
What is chyme
Semi liquidified food that comes from the stomach
What shape does the monogastric stomach and where is it located
C shaped located just behind the diaphragm
What is the glandular portion of the monogastric stomach
The gastric pits primarily located in the body of the monogastric stomach
What are the three sections of the monogastric stomach
Cardia, fundus, and body
What is the distal portion of the monogastric stomach
Pylorus which has less glands here and pushes food along
What is the rugae
Transient folds in the gastric mucosa that allows the stomach to expand when filled w/ food increasing SA for absorption and secretion of the glandular products
What are gastric pits
Different glandular cells each w/ different secretions in horses these are only found in the pyloric region
What are the different gastric pits
Mucous neck cells secrete mucus, chief cells secrete pepsinogen, and parietal cells secrete HCL and intrinsic factor
What is pepsin
A proteolytic enzyme essential to digest proteins produced by pepsinogen and HCl
When do chief cells produce pepsinogen
When food is present in the stomach
What is the pyloric gland region of stomach
The last glandular portion of the stomach that is comprised of the pyloric antrum, pyloric canal, and pylorus region
What is the pyloric sphincter
The opening into the duodenum
What are the cells in the pyloric gland region
Mucous secreting cells and G cells that secrete gastrin
What is the most muscular part of the stomach
The pyloric gland region
What 3 things stimulate glandular secretion in the stomach
Acetylcholine from cholinergic neurons, gastrin from G cells, and histamine secreted by ECL cells
What is the cephalic phase of secretion
Anticipation of eating a meal
What is the gastric phase of secretion
Secretion of gastric glandular cells that begins when food enters the stomach
What stimulates the cephalic phase
Enteric nervous system stimulates via the vagus nerve
What does the enteric nervous system stimulate the release of in the cephalic phase
Acetylcholine
What casscade of events does the release of acetylcholine, gastrin, and histamine after being released and binding to receptors
Directly triggers chief cells secreting pepsinogen into the stomach directly trigging G cells that secrete gastrin (hormone) into the bloodstream directly triggering parietal cells to secrete H+ and Cl- ions and histamine released by ECL cells
What is bilious vomiting syndrome
The cephalic phase is consistently occuring making it the contributing vector this is more common in working breeds
What can bilious vomiting syndrome be treated w/
Frequent meals, increased fiber to slow digestion, omeprazole, or acid therapy to decrease production
What is the process of the gastric phase of secretion
Glandular cells stimulated by stretching of stomach wall, peptides formed by protein breakdown via pepsin triggers vagal reflexes to and from brain as well as local enteric reflexes acetylcholine is released stimulating secretion of histamine and gastrin which stimulates more histamine all three act on parietal cells to produce more H+ and Cl- ions
How acidic can stomach acid be
pH of 2
What is monogastric stomach motility
Muscle contractions of stomach wall help break down food particles and gastric contents released into small intestine at controlled rate it is a specialized smooth muscle pacemaker cells and fluctuations in resting membrane potential lead to muscle contraction
How do fluctuations in the resting membrane potential occur in monogastric stomach motility
By acetlycholine elevates resting potential (norepinephrine does the opposite) and entry of Ca++ ions into muscle cell initiates contraction
What is the function of the fundus of the monogastric stomach motility
It extends to accommodate large volumes of food
What is the function of the body of the monogastric stomach motility
It is a large mixing chamber
Where are monogastric stomach peristaltic contractions weak
In the fundus and the body
How do peristaltic contractions change in the stomach
Progressively stronger as food moves towards the pylorus
What is retropulsion
Kicks back large food particles back to the body of the stomach
What controls gastric motility
Neurotransmitters and hormones
How do neurotransmitters control gastric motility
Fibers of vagus nerve synapse on cells in gastric myenteric plexus decreasing motility when food enters and increases when food approaches pyloric region and acetylcholine is released in the pyloric region increasing peristaltic contractions
How do hormones control gastric motility
Gastin leads to exitatory functions
What is gastric emptying
Rate is controlled by the strength and degree of pyloric antral muscle contractions w/ gastrin increasing contraction strength and stomach distention increases rate of contraction
How do hormones affect gastric emptying
They are released by a dilated duodenum delaying gastric emptying by inhibiting pyloric antral contractions, constricting pyloric sphincter, decrease stomach motility, and decrease secretion of stomach enzymes
What hormones affect gastric empyting
Secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP)
What digestion occurs in the stomach
Mechanical digestion is essential to increasing food SA and chemical digestion occurs in the luminal and membranous chemical digestion via hydrolysis
What is hydrolysis
Macromolecules broken into short chain polymers
What is chemical digestion of CHO
CHO digestion begins w/ amylase in saliva continuing in stomach and SI
What is protein digestion
Begins in the stomach continuing into the SI and pepsinogen activated by HCl to pepsin
Why are forestomachs non glandular
Because they have microorganisms for fermentation in rumen and reticulum so complex CHO such as cellulose are broken down
What is the reticulum
First of chambers located cranial to the rumen, contents easily enter and exit to rumen, honeycomb wall appearance, and heavy foreign objects will accumulate here
What is hardware disease
Metal accumulation in the reticulum that can evenually poke thru the wall of the stomach affecting the heart
What is the rumen
Occupies most of the left side of abdominal cavity, microorganisms ferment CHO and cellulose, papillae in mucosa increase SA for absorption, and pillars divide rumen into 3 different sectors
What is the omasum
Looks like many plies or the book stomach, connects reticulorumen to abomasum, folds of mucosa w/ papillae on surfaces, absorption of water and salts here, and links to the esophageal groove
What is the esophageal groove
Links the esophagus w/ omasum in young ruminants so the milk ingested bypasses the reticulorumen
What would happen if the esophageal groove did not close
Bacteria in reticulorrumen would ferment milk and lactic acid produced would inhibit normal microbial action
What is the abomasum
Elongated true stomach, lined w/ glandular tissue, functions like simple monogastric stomach, and has a continuous flow of ingesta in bring food directly into the duodenum
What is secreted in young ruminants abomasum and why is it secreted
Renin is secreted causing milk protein coagulation prolonging time for pepsin to break down proteins
What is reticulorumen motility consist of
Primary contractions, rumination contractions, and secondary contractions
What is the primary contraction of reticulorumen motility
Mixing contractions, ensure content movements btw reticulum and rumen, separate particles based on size
What is ruminaton contractions in reticulorumen motility
Ingesta moves from reticulorumen back into oral cavity for additional saliva and continued chewing called rumination
What are the 4 steps of rumination
Regurgitation, reinsalivation, remastication, and reswallowing
What is secondary contractions of reticulorumen motility
Eructation (belching), responsible for the release of gases such as CO2 and methane produced during fermentation, w/o gas release bloat occurs, and area of brainstem controls reticuloruminal activity
What is the reticulorumen ecosystem
A wide variety of bacteria, protozoa, and fungi that is acquired after birth and is controlled by diet, amount of food consumed, and interactions btw mother and baby
What do the microorganims consume in their environment
They quickly consume oxygen and food
What does a ruminants diet contain
Mostly roughage providing complex CHO such as cellulose, hemicellulose, and pectin plus some concentrates providing nonstructural CHO such as starches, frustosans, and simple sugars
How can the ruminant digest the microorganisms
As a source of protein
How do microorganisms use the nutrients they consume
For their own growth and development
What is used to digest complex CHOs
The cellulolytic bacteria lyces the cell walls breaking them down and hydrolysis by catalse enzymes to simple sugars
How are starches and soluble sugars digested
Hydrolysis by amylolytic bacteria to monosaccharides and polysaccharides that are absorbed by microvilli and further metabolized to pyruvate and convert into VFAs
What is the main source of energy for ruminants
VFAs
How are lipids digested in ruminants
Microorganisms in the reticulorumen hydrolyze triglycerides, glycolipids, and free FAs producing VFAs such as acetic acid, propionic acid, and butyric acid
Why should lipids be a small portion of a ruminants diet
Because high lipid diets are toxic to the bacteria causing decrease in appetite, reducing motility of reticulorumen, and decreased fermentation of cellulose
How is protein digested in the ruminant
By the microbes in the reticulorumen microbial peptidase breaks down proteins to peptide chains,the synthesize AA from ammonium, and by converting non protein nitrogen (NPN) compounds then they are further broken down in SI by enzymes to AA which are absorbed and transported to the liver producing urea
Where does urea go to after being produced by the liver
To the rumen for reuse in making microbial proteins
Why are ruminants predisposed to a glucose deficiency
Because ruminal microbes process CHO before they are exposed to intestinal enzymes
What does gluconeogenesis look like in ruminants
Occurs in the liver from non CHO sources such propionate, butyric acid, acetate, and absorbed AA
What is the SI
A tube that carries chyme away from stomach and deposits it in the large intestine
What is the SI suspended from
The ball wall by mesentery
What is the function of the duodenum
Receives chyme through pyloric sphincter
What is the function of the jejunum
The longest part and is where most chemical digestion and absorption occurs especially for monogastrics
What is the function of the ileum
Contains the prominent Peyer’s patches and empties into the large intestine at the cecum (horses), colon (dogs and cats), or cecum and colon (ruminants and pigs)
What are plications
Folds in the mucosal lining
What is found in the mucosa of the SI
Villi which contain microvilli forming a brush border
What are intestinal crypts
Crypts of Langerhans is the space between villi
Where is the only location of cell division
The crypts of Langerhans
What are lacteals
Lymphatic capillaries that carry absorbed lipids and fat soluble substances to the thoracic duct and into the vena cava
What do blood capillaries do in the SI
Collect some absorbed nutrients and transports them to the liver
What stimulates the secretion of cholecystokinin (CCK)
High AA or FA concentrations or low pH of chyme entering duodenum
What are the functions so cholecystokinin (CCK)
Inhibits gastric emptying, causes increased secretion of bicarbonate and pancreatic digestive enzymes, and stimulates secretion of enteropeptidase converting pancreatic enzyme trypsinogen to trypsin
What stimulates the secretion of secretin
High FA concentrations or low pH of chyme entering duodenum
What are the functions of secretin
Decreases HCl production in the stomach and increases pancreatic and biliary bicarbonate secretions
What is produced by the endocrine portion of the pancreas
Pancreatic islets such as alpha cells (glucagon) and beta cells (insulin)
What does glucagon do
Increases blood glucose through gluconeogenesis
What does insulin do
Decreases blood glucose by increasing the glucose absorption in the tissues of the body
What is produced by the exocrine portion of the pancreas
the groups of acini has ducts that merge to converge into the pancreatic duct producing excretions containing bicarbonate and digestive proenzymes
What causes an increase in exocrine secretions from the pancreas
The cephalic phase, neural stimuli, and endocrine stimuli
What exocrine enzymes from the pancreas are vital for digestion
Lipase breaks down lipids, amylase breaks down carbs, nuclease breaks down nucleic acids, and proteases break down peptides
What are characteristics of proteases
They are secreted as proenzymes and are inactive until activated by CCK
What is exocrine pancreatic deficiency
When the pancreas doesnt make enough digestive enzymes poster child is german shepards
What is the largest digestive gland in the body
The liver
What are the functions of the liver
Secretes substances essential for digestion and absorption of nutrients, synthesizes nutrients and regulates their release into the bloodstream, excretes toxic substances originating w/in and from outside the body, converts AA into ketoacids, and produces plasma proteins, cholesterol, and blood coagulation factors
What are the 2 surfaces of the liver
Diaphragmatic and visceral surface
What is the diaphragmatic surface of the liver
The side of the liver that faces the diaphragm
What is the falciform ligament
Attaches the liver to a diaphragm
How is the liver strategically placed
To process blood leaving GIT preventing toxic substances from entering general circulation
What 3 things can deposit contents in the duodenum
The common bile duct, pancreatic duct, and accessory pancreatic duct
What the most amount of lobes a liver can have
Up to 6
Where is the liver triad located
At the lobule periphery
What comprises the triad
Hepatic portal vein, hepatic artery, and bile ducts
What are sinusoids
Large leaky capillaries where the hepatic artery and hepatic portal vein come together to bring blood to the liver
What are kupffer cells
Macrophages that live in sinusoids that engulf foreign objects
What are the functions of the hepatocytes
Excrete proteins to enter bloodstream through pores in adjacent sinusoids and excrete bile into canaliculi that travels in the opposite direction of the blood to the common bile duct
What carries the blood from the liver to the vena cava
The central vein
What are the functions of the gallbladder
Concentrates and stores biles until needed in the duodenum to digest high fat and peptide concentrations and provides means for the liver to excrete waste products even when animal is not eating
What is bile composed of
Bile salts, phospholipids, cholesterol, and bile pigments
What are the steps of enterohepatic circulation
Begins w/ secretion of bile salts into the canaliculi, bile salts draw water out of hepatocytes and become a liquid bile, bile is released into duodenum to emulsify fate, bile salts are reabsorbed when they reach the ileum, bile salts enter hepatic portal vein and return to liver, liver reabsorbes bile salts and recycles them back to bile
What releases bile into the duodenum
The Sphincter of Oddi
How is enterophepatic circulation a postivie feedback loop
More bile salt returning to the ileum stimulates more bile production
What influences the amount of bile is synthesized by hepatocytes
The amount of bile salts that recirculate from intestine to liver
What happens when stimuli for CCK is gone
CCK secretion stops, Sphincter of Oddi closes reducing bile flow into duodenum, bile diverted into gallbladder, reabsorption of bile salts is diminished, and bile acid synthesis is diminished
What are the steps of eliminating bilirubin through bile
Heme is converted to free unconjugated bilirubin, free bilirubin is joined to glucuronic acid in liver to form conjugated bilirubin, released into bile and enters into small intestine, intestinal bacterial enzymes convert it to urobilinogen, most urobilinogen is oxidized to urobilin and stercobilin which is excreted from body in feces, and the remainder of urobilinogen reabsorbed into enterohepatic circulation
What are the 3 reasons why there is an increased bilirubin levels in blood
Pre-hepatic bilirubinemia, hepatic bilirubinemia, and post hepatic bilirubinemia
What is pre hepatic bilirubinemia
Too much heme from broken down RBCs commonly seen w/ hemolyic anemia
What is hepatic bilirubinemia
Liver is congested/diseased/can’t keep up this is fatty liver patients
What is post hepatic bilirubinemia
bile outflow obstruction this would be caused by the common bile duct is blocked for some reason
Where is excess glucose stored as glycogen in the body
Liver, skeletal muscle, and adipose cells
What is glycogenolysis
Breaking down glycogen into glucose when needed
What is gluconeogenesis
Synthesis of glucose from noncarbohydrate sources such as fatty acids
What species primarily does gluconeogenesis
Cows
What is ketosis
The results of when FA mobilization overwhelms the oxidative capacity of the liver
What goes into small intestine motility
Peristalsis propels content and segmentation is mixing action
How are materials passively absorbed across the intestinal mucosa
Through simple diffusion
How are materials actively absorbed across the intestinal mucosa
Active transport molecules is transported using ATP, secondary active transport, antiports, and facilitated diffusion
What is secondary active transport
One molecule travels w/ another that is being actively transported
What are anitports
One molecules is exchanged for another
What is facilitated diffusion
Uses a carrier but not energy
What is the 4 step active process for lipid digestion and absorption
Emulsification, hydrolysis, micelle formation, and absorption
What is the emulsification step of lipid digestion and absorption
Lipids are warmed in stomach and bile salts in SI act like detergent
What is the hydrolysis step of lipid digestion and absorption
Pancreatic enzymes lipase and colipase are released
What is the micelle formation step of lipid digestion and absorption
Mass of monoglycerides, FAs, and bile salts act like ferry to transport to the enterocyte surface where they are diffused into the cell and chylomicrons are then expelled from the enterocytes
What is the absorption step of lipid digestion and absorption
Chylomicrons picked up by lymphatic system
What is the cecum
Blind diverticulum at the beginning of the colon that is made of the base, main body, and apex
What does segmentation in the colon and cecum do
Prolongs time for contents to stay in the large intestine to absorb some nutrients and reabsorb water
How does ingesta move thru the large intestine
Travels slowly being thoroughly mixed to allow for contact w/ absorptive surface motility patterns vary w/ species
How does segmentation move ingesta
Back and forth
What is antiperistalsis
Movement toward stomach helping slow movement
What initiates slow waves in the large intestine
Pacemaker cells
What does depolarizing waves sent to the stomach result in
ANtiperistaltic movements
What does depolarizing waves sent to the rectum do
Creates peristaltic movements
What are the functions of the large intestine
Absorption of water and ions and completion of CHO or protein microbial digestion and little absorption
What type of receptors are stimulated when feces are transported to rectum
Sensory receptors
What happens after sensory receptors are stimulated
Defecation reflex is initiated, colon and rectum contract, inner anal sphincter muscles relax, need to defecate is percieved, and outer anal sphincter muscle relax
