Flashcards
10. Digestive System part 1
Cards in this deck (200)
- 1what are the functions of the digestive system?break complex foods into simple molecules, and absorb nutrients into the blood for use in the body
- 2what are the four layers of the gastrointestinal tract, from innermost layer to outermost layer?1. mucosa
2. submucosa
3. muscle layer
4. serosa - 3what is the formation and function of the mucosa?lining layer of the GI tract made of lining epithelium and some loose connective tissue
- 4what is the position and formation of the submucosa?beneath the mucosa containing glands and dense connective tissue
- 5what is the function and position of the muscle layer?moves food down the GI tract by peristalsis and lies outside the submucosa
- 6where is the serosa and what is its formation?the outermost layer of the GI tract made of thin, tough connective tissue
- 7what are the two types of epithelium in the GI tract?stratified squamous epithelium and simple columnar epithelium
- 8where in the GI tract is the simple squamous epithelium? what does it appear as?is thick and tough and covers the mouth, pharynx oesophagus and anus
- 9where is the body is the simple columnar epithelium and what is its purpose?thin so allows absorption of substances. covers where the oesophagus meets the stomach, stomach, small and large intestine and at the junction of rectum and anus
- 10what two types of muscle are used in the digestive tract?skeletal muscle and smooth muscle
- 11why is skeletal muscle used in the GI tract, and where?needed for voluntary control e.g. chewing or swallowing so is in the mouth, cranial oesophagus, and external anal sphyncter
- 12where is smooth muscle needed in the GI tract and where?all areas not using skeletal muscle, as smooth muscle is involved in involuntary movement
- 13how are muscle layers arranged in the GI tract?outer layers are longitudinal (shortens sections of the tube) and inner layers are circular (narrows sections of the tube)
- 14what are the two types of contraction in the GI tract?peristaltic contractions and segmental contractions
- 15how does peristalsis occur and what is the purpose?circular muscle contracts in waves along the tract propelling ingesta along the GI tract
- 16how does segmentation occur in the tract and why is it needed?periodic circular muscle contractions in adjacent sites causing mixture and slowing of movement of ingesta in the tract
- 17why are lips vital in eating?they are an important prehensile organ so are vital in ingesting food. if paralysed food may not be edible to the animal
- 18what animals need lips less?carnivores, lips play a passive role
- 19in the tongue, what type of muscle is: 1. the back of the tongue? 2. the bulk of the tongue?1. extrinsic
2. intrinsic - 20what direction does the tongue lay in the mouth?ventrally
- 21what are the main functions of the tongue?prehension, lapping, grooming, taste and thermoregulation
- 22what is the function of the salivary glands and why is this important?produce saliva for lubrication, digestion and thermoregulation
- 23where do all salivary ducts lead to ?the oral cavity
- 24what 3 salivary glands do all animals have and where are they located?-parotid = ventral to ear canals
-mandibular = ventral to parotid at caudal angle to the mandible
-sublingual = located medial to shafts of the mandible under base of the tongue - 25what additional salivary glands do carnivores have and where are they located?zygomatic salivary glands which are located caudally to the eye
- 26what is the pharynxjunction where respiratory tract and oral cavity meet
- 27what structures separate the oral cavity and nasal cavity?hard and soft palate, nasopharynx, oropharynx, common pharynx, epiglottis and tonsils
- 28what are the 4 main functions of the oral cavity?prehension, mastication, chemical digestion and preparation for swallowing
- 29define bolusaddition of saliva to chewed food in preparation of swallowing
- 30what is the function of salivary amylase?breaks down amylose into digestible monosaccharides
- 31what is the function of lipase and why is it vital for young animals?breaks down lipids into glycerol and fatty acids and is vital in milk digestion
- 32what are bicarbonate and phosphate buffers needed for?neutralise acids formed in the rumen and maintain a normal, healthy pH
- 33what is in control of the salivary glands?autonomic nervous system in the most, but in the fight or flight response the is inhibited by the parasympathetic nervous system
- 34what is meant by an arcade?the range of teeth
- 35what bones contain the upper arcade of teeth?maxillae and incisive bones
- 36what bones contain the lower arcade of teeth?mandible
- 37what is the difference between carnivore and herbivore teeth?herbivore teeth grow continually and are ground down, so aren't completely covered by enamel. carnivore teeth are also pointier as they are used for tearing while herbivore teeth are flatter as they are used for grinding
- 38what are the 4 main types of teeth and what is their main purpose?incisors = grasping teeth
canines = tearing teeth
premolars = cutting teeth
molars = grinding teeth - 39in dental formulae how do we differentiate between deciduous and permanent teeth?deciduous are lower case and permanent are upper case (in incisors deciduous = i, permanent = I)
- 40what do the numbers represent in dental formulae?first number is amount in upper arcade, second number is number in lower arcade
- 41how do we determine the total number of teeth in an animal?add all numbers together and multiply by 2
- 42what is different about horse teeth?not all horses have canine teeth or vestigial premolars
- 43what is different about ruminant teeth?they don't have upper incisors or canines, they have thick connective tissue to grind against
- 44what are carnassial teeth and where are they located?first molar of the lower arcade and last premolar of the upper arcade and are large teeth with deep roots present in carnivores
- 45why is knowledge of tooth structure important?they are living structures susceptible to blood, lymphatic and nerve damage so are highly susceptible to pain
- 46what is the apex of the tooth?the base of the tooth where the blood and nerve supply enter
- 47what is the pulp of the tooththe centre of the tooth giving the blood and nerve supply
- 48what is the dentin of the tooth?surrounding the pulp and is protection for the pulp as it is made of more dense bone
- 49what is the cementum of the tooth?covers the root of the tooth and is the hard connective tissue securing the tooth in its bony socket
- 50what is the enamel of the tooth?the hard layer covering the crown of the tooth providing protection from day to day usage
- 51what is the gingiva?the gums
- 52define heterodontmammals with teeth of mixed form and function
- 53define homodontreptiles and fish with all teeth of the same morphology
- 54define diphyodontmost mammals with two successive sets of teeth
- 55define bunodontomnivores with molars with low rounded cusps
- 56define polyphyodontteeth continually replaced, common in reptiles
- 57define hypsodonthorses and cows with teeth of a long crown and short root once mature and much of the crown is sub-gingivally
- 58define elodontrabbits with teeth growing continually throughout life
- 59what is the purpose of the oesophagus?muscular tube extending from pharynx to stomach with the sole role of transport. no absorption or digestion occurs here
- 60where does the oesophagus enter the stomach?cardiac sphincter. weak sphincter of smooth muscle
- 61why does the oesophagus enter the stomach at an angle?as the stomach expands with food the fold of the stomach against the oesophagus acts as a natural valve preventing reflux
- 62in what species is the angle of the oesophagus meeting the stomach so deep that vomiting is almost impossible?horses
- 63what is the monogastric stomach?a simple single stomach in most animals other than ruminants
- 64what are the 5 areas of the monogastric stomachcardia, fundus, body, pyloric antrum and pylorus
- 65where are gastric glands?in gastric pits in the fundus and pylorus
- 66what cells do gastric glands contain?parietal cells (produce hydrochloric acid)
chief cells (produce pepsinogen)
goblet cells (produce protective mucus) - 67what glands are in the pyloric antrum and what do they produce?mucous cells forming protective mucous, g cells secreting gastrin
- 68how is gastrin secretion stimulated?presence of food in the pyloric antrum
- 69what does gastrin stimulate?moves to gastric glands and stimulates the release of hydrochloric acid from the parietal cells
- 70what is the shape of the stomach and what is each side called?looks like a c shape on its side and the inner curve is the lesser curvature, while the outer curve is called the greater curvature
- 71how should the stomach appear when empty?pink and glistening with a copious amount of mucous
- 72how are the mucosa arranged?multiple long folds called rugae to allow for distention
- 73what is gastritis?inflammation of the stomach which looks like reddening of the observed surface
- 74what are stomach erosions?breaks in the surface of the mucous and underlying epithelium.
- 75what are deep stomach erosions called?gastric ulcers
- 76what are the motor functions of the fundus and body of the stomach?relaxes with the swallowing of food allowing it to expand and fill with food. body contracts to help mix food
- 77what are the motor function of the pyloric antrum?increases contractions with swallowing of food and stimulates mixing of food. responsible for most of the grinding in the stomach
- 78where other than the oesophagus is peristalsis found?the stomach and intestines to allow movement of bolus throughout the GI tract
- 79what layers does the stomach contain?inner mucosal layer, submucosa, muscular layer and outer serosal layer
- 80what is the purpose of the circular muscle fibres in the stomach?contract in the antrum to account for strong grinding activity
- 81what are the motor functions in the pylorus?concentration of circular muscle fibres to maintain constant tone but never close. allows movement of liquefied food into duodenum. chime is forced through by contractions in the antrum
- 82define chymepartially digested, liquified food
- 83what is the result of stimulating the stomach via the parasympathetic nervous system through the vagus nerve?fundus relaxes allowing it to fill, increases contractions in the antrum and body to mix food
- 84what affect does the sympathetic nervous system have on the stomach?normally has little effect unless activated by stressful situations which can cause a decrease in motility
- 85define gastric atonydecreased muscle tone in stomach decreasing motility usually as a result of stress
- 86what effect does gastrin have on the stomach?increases production of hydrochloric acid and inhibits muscular activity of the fundus leading to relaxation and greater filling capacity
- 87what is the enterogastric reflex?factors causing distension of intestines or increased acidity in duodenum which inhibits stomach contraction. leads to delayed emptying of gastric contents
- 88what is the purpose of the enterogastric reflex?prevents stomach emptying into the intestine before it is ready
- 89what is the purpose of the gastrocolic reflex?gastric distension and stretching leading to an increase in colonic motility. results in urge to defacate
- 90what is the purpose of the gastrocolic reflex?helps make room for more food
- 91what is secretin?hormone released from the duodenum in response to stomach acid presence in the small intestine
- 92what is the result of secretin being secreted?causes fundus to relax and inhibits peristalsis of stomach body and antrum to slow gastric emptying
- 93what is cholecystokinin?a hormone which inhibits the contractions of the antrum, body and fundus
- 94when is cholecystokinin released and why?released when there are large amounts of fat or protein in the duodenum to slow gastric emptying
- 95what is intrinsic factor?must combine with vitamin B12 for the vitamin to absorbed into the small intestine
- 96where is pepsinogen secreted from?chief cells
- 97what is pepsinogen?a precursor to the enzyme pepsin
- 98how is pepsin formed?when pepsinogen is converted by hydrochloric acid
- 99what is meant by pepsin is proteolytic?it breaks down proteins
- 100what does pepsin do?breaks down complex proteins into amino acid chains, and presence of pepsin causes G cells to release gastrin, so more HCl is made and more pepsinogen is converted into pepsin
- 101when is pepsin inactivated?when it moves into the more alkaline pH of the duodenum
- 102what is the purpose of mucus in the GI tract?provides a gelatinous coating for the stomach
- 103what are mucins?complex molecules produced by goblet cells in gastric pits which are the main component of mucus coating in the stomach
- 104what is the purpose of bicarbonate ions in the mucus?makes coating more alkaline to partially neutralise the HCl
- 105why must components of mucus be continually secreted?to keep stomach continually protected as mucus is fragmented by hydrochloric acid in the stomach
- 106what may result from ineffective mucus lining?gastritis and gastric ulcers
- 107how is the hydrochloric stomach acid in the stomach produced?parietal cells in the gastric glands secrete hydrogen ions and chloride ions by active transport and they combine to form hydrochloric acid
- 108what receptors are on the blood side of parietal cells?for gastrin, acetylcholine and histamine
- 109what is the purpose of the receptors on the blood side of the parietal cells?regulate acid production
- 110when is the optimum amount of hydrogen and chloride ions secreted?when all three receptors are stimulated
- 111what happens when the pH of stomach contents in the antrum is below 3?gastrin release is inhibited and hydrochloric acid production declines
- 112what 2 drugs reduce gastric acidity?H2 receptor antagonists and proton pump inhibitors
- 113what are prostaglandins?small molecular structures produced by some tissues
- 114what is the function of prostaglandins?involved in inflammation, regulation of kidney blood supply, regulation of oestrous cycle and maintaining health of GI tract
- 115which prostaglandins reduce hydrochloric acid production and how?types E and I by inhibiting gastrin release and by inhibiting parietal cells
- 116how do prostaglandins maintain the mucous barrier?stimulating bicarbonate ion production to neutralise pH of stomach acid
- 117what are NSAIDs and how do they work?drugs used for osteoarthritic joints and inflammatory processes which work by blocking production of inflammatory prostoglandins
- 118what is the possible issue with NSAIDs?block production of useful prostaglandins in the stomach so can lead to gastric ulceration
- 119what is the function of the small intestine?where most nutrients are absorbed
- 120how many segments are there in the small intestine and what are they?3, duodenum, jejunum and the ileum
- 121where is the duodenum?first segment of the small intestine immediately after the stomach and is directly next to the pancreas
- 122what is the longest portion of the small intestine?jejunum
- 123where is the ileum?short portion entering the colon
- 124how is the ileum separated from the colon?ileocaecal sphynchter
- 125what is the importance on the ileocaecal sphincter?regulates emptying of small intestine to large intestine
- 126how is the mucosa of the small intestine adapted and why?has villi and microvilli to increase surface area for more efficient absorption of nutrients into the blood
- 127what are the crypts of Lieberkühn?areas of the small intestine to provide new epithelial cell production. as new cells are produced, they move up to the villi to replace all those which are dead
- 128why does the small intestine have peristaltic contractions?mixing, bringing digested materials into contact with villi for absorption and for slow movement of ingesta through intestine
- 129what is the problem in decreased peristalsis and when does it occur?ingesta moves too slowly through intestine and can be caused by disease or stress common in horses and rabbits
- 130what does cholecystokinin do in the small intestine?stimulates intestinal motility
- 131where are cholecystokinin's produced in the small intestine?secreted by cells in the intestinal mucosa fasts and proteins are present
- 132what is the purpose of prostaglandins in the GI tract?stimulates GI motility and secretions
- 133how does the parasympathetic nervous system affect the small intestine?stimulates motility, secretions and blood flow
- 134how does the sympathetic nervous system affect the small intestine?decreases circulation
- 135in order to be absorbed what substances do/don't need to be broken down?don't: electrolytes and vitamins
do: carbohydrates, proteins and fats - 136where is amylase secreted?mouth and pancreas into lumen of duodenum
- 137what does amylase do?converts polysaccharides into disaccharides
- 138what happens to convert disaccharides into monosaccharides?specific enzymes to the disaccharide is used to break it down e.g. sucrase to break down sucrose
- 139where are sucrase, maltase, isomaltase and lactase found?cell membranes of microvilli
- 140name the three monosaccharidesglucose, galactose and fructose
- 141what controls number of enzymes on the brush border?the diet of the animal
- 142why do animals become lactose intolerant?when nursing the animal has a lot of lactase, but after stopping, lactase is no longer produced meaning lactose remains in the intestine and water is also held in the intestine leading to diarrhoea
- 143why does sudden change from dry to wet animal food lead to diarrhoea?more sucrose in wet food so more sucrase needed in the digestive tract for digestion. amount of sucrase increases after a few days on the diet
- 144what do proteases do?break large protein molecules into dipeptides or amino acids
- 145where does protein digestion begin?in the stomach where pepsin breaks apart protein into polypeptides
- 146why are different proteases needed?different amino acids form different chemical bonds, and specific enzymes are needed for each type of bond
- 147what proteases are produced in the pancreas?trypsin, chymotrypsin, elastase, aminopeptidase, carboxypeptidase
- 148how are pancreatic enzymes released?as inactive precursors to be activated by intestinal enzymes
- 149where is protein digestion completed?at the brush border as peptidases are embedded in cell membranes at these cells
- 150what is the break down of fat called?emulsification
- 151how are fat globules broken onto droplets?agitation of the pyloric antrum
- 152what is the role of bile acids?combine with fat droplets to emulsify fat into micelles
- 153where are bile acids produced and used?produced in the liver and used in the duodenum
- 154how do pancreatic lipases function?penetrate bile coating of micelles to digest triglyceride molcules
- 155what is formed when lipase breaks down triglycerides?glycerol, fatty acids and monoglycerides
- 156what are the 3 parts of the large intestine?caecum, colon and rectum
- 157what are the functions of the small intestine?absorb water and electrolytes and store faeces
- 158what is the caecum like in carnivores?poorly developed but in oter species microbial digestion occurs here
- 159what is the colon like in carnivores?simple tubular organ using segmental and peristaltic contractions to move contents and mucus lubricates the passage of contents
- 160why does the rectum need mucus secreting glands?lubricate passage of contents
- 161true or false the rectum is capable of less expansion than the colonfalse, rectum can expand more
- 162what is the purpose of the rectum and how does it complete this function?storage of faeces and has sensory detectors to determine extent of stretching and initiate defecation response
- 163what are the two sphincters in the anus and which is under voluntary control?internal sphincter (autonomic control), external sphincter (voluntary control)
- 164explain nervous control of defecationparasympathetic nervous system causes relaxation of the internal sphincter in correspondence with colonic motility. constriction of internal anal sphincter is caused by sympathetic nervous system
- 165how is defecation indicated?as rectum fills and distends, stretch receptors cause partial relaxation of internal anal sphincter allowing faecal content to move into internal sphincter canal making contact with anal mucosa, stimulating mucosal receptors and increasing need for defecation
- 166what happens as rectum increasingly distends?internal sphincter is open for longer periods increasing conscious need for defecation
- 167what happens when defecation occurs?voluntary motor impulses to external sphincter are blocked allowing it to relax
- 168why do herbivores need a different digestive tract to omnivores and carnivores?vegetable matter is harder to digest fully so must be fermented
- 169what are types of foregut fermenters?ruminants and pseudo-ruminants
- 170what are types of hindgut fermenters?equidae +(rabbits, hares etc)
- 171give examples of: 1. ruminants 2. pseudo-ruminants 3. equidae1. cows
2. camels
3.horses/zebras - 172how many stomachs do ruminants have and what are they called?4. abomasum, reticulum, rumen and omasum
- 173what is the name of the true stomach in ruminants?the abomasum
- 174what is the order of movement through the GI tract of ruminants?oesophagus, reticulum, rumen, omasum, abomasum, duodenum
- 175what is the act of ruminating food?chewing, swallowing, regurgitating, further chewing and the finally swollowing
- 176which stomach of a ruminant is the smallest?the reticulum
- 177what separates the rumen and the reticulum?ruminoreticular fold
- 178how is the reticulum adapted?folded honeycomb like surface to increase surface area
- 179how is food moved from reticulum to rumen?the walls of the reticulum and rumen are continuous and contract in reticulorumen contractions to move food
- 180what is hardware disease ruminants?danger caused by swallowing heavy or sharp items as they can get lodged in the wall of the reticulum due to reticulorumen contractions which is dangerous due to proximity to the heart
- 181what is the function of the rumen?large fermentation vat for extracting usable energy containing compounds from the vegetable matter consumed
- 182what is the formation of the rumen?series of muscular sacs partially separated by folds of the rumen wall (pillars)
- 183why are pillars vital in digestion?they allow sacs in rumen to close off allowing for effective mixing of food compounds and digestive juices
- 184what allows food to be regurgitated for further chewing?reticulorumen contractions
- 185how is risk of bloat decreased?carbon dioxide and methane expelled at same time as food regurgitated during reticulorumen contractions
- 186what is the main benefit of ruminants regurgitating food?they can do further mechanical breakdown of food allowing more enzymes and microbes to act
- 187how is rumen motility controlled?vagus nerve
- 188what factors control rate of reticulorumen contractions?pH, presence of fatty acids, consistency of food and stretch receptors in the rumen
- 189what are the two types of rumen microbes and what do they do?-amylolytic (break down starch and soluble carbohydrates)
- cellulolytic (break down cellulose into less complex polysaccharides and monosaccharides) - 190what are volatile fatty acids?the product of cellulose and starch breakdown to give accessible energy to animals from these sources
- 191how are volatile fatty acids formed?anaerobic fermentation of cellulose and starch
- 192what do volatile fatty acids form?propanoic acid makes glucose, others form amino acids and proteins when converted by microbes
- 193what happens to proteins in ruminant digestive tracts?absorbed by microbial enzymes in the rumen and the proteases reduce them to peptides and amino acids
- 194how are amino acids and peptides used by the rumen?some are used by microbes to incorporate into their own protein structures, or convert them into ammonia
- 195what is ammonia used for in proteins?in microbes forming amino acids and proteins
- 196when is urea produced?when levels of ammonia in the liver become toxic so are converted to urea
- 197why is urea useful in ruminants?nitrogen source for rumen microbes
- 198why is urea added to food?adds nitrogen so improves lower quality feed
- 199what happens to microbes after their use in the rumen?they are flushed from the reticulorumen to the omasum, abomasum and intestines to be digested as a source of more protein
- 200describe the relationship between the ruminant and the microbes in its digestive system.a symbiotic relationship where the ruminant supplies the microbes with nutrients in the food, and the microbes supply the host with amino acids, proteins and vitamins K and B
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- level 4 VNAS 1 Flashcards on 10. Digestive System part 1, created by Olivia McKenzie-Allen on 14/12/2019.
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