Digestive System Flashcards

1
Q

list and describe the 5 functions of the digestive system

A
  1. prehension: the act of obtaining food
  2. mastication: chewing, mechanical breakdown
  3. digestion: chemical breakdown
  4. absorption: smaller components entering rest of body
  5. elimination of solid wastes: as feces
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2
Q

list the 4 layers of the wall of the digestive tract, from innermost to outermost

A
  1. mucosa
  2. submucosa
  3. muscularis
  4. serosa
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3
Q

describe the mucosa

A

inner layer, epithelia lining

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4
Q

list and give the locations and functions of the two types of epithelial linings of the mucosa

A
  1. stratified squamous epithelium: protective layer, prevents damage, mouth and esophagus
  2. simple columnar epithelium: more glandular for digestion and absorption
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5
Q

what tissue composes the submucosa?

A

loose areolar connective tissue

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6
Q

describe the two muscle types and their locations in the muscularis, plus the functions

A
  1. skeletal muscle: mouth and esophagus (chewing and swallowing)
  2. smooth muscle: rest of tract
    circular and longitudinal layers allows for contraction in different directions and propulsion
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7
Q

describe the serosa, including an alternate name and tissue type

A

outer layer, also called visceral peritoneum, simple squamous epithelium

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8
Q

list the 3 components of the mouth

A
  1. labia/lips
  2. teeth
  3. tongue
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9
Q

describe the labia/lips of the mouth

A

entrance to mouth, major species variation

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10
Q

list and describe the 4 types of teeth from front of the mouth to the back

A
  1. incisors: cutting, prehension
  2. canines: tearing, mastication
  3. premolars: grinding, mechanical
  4. molars: fine grinding, mechanical
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11
Q

what is the dental formula?

A

indicated the number of upper and lower incisors (i), canines (c), premolars (pm), and molars (m) on one side of the mouth

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12
Q

how many upper incisors and canines do ruminants have?

A

zero!

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13
Q

list the 4 structures of teeth

A
  1. periodontal membrane
  2. dentin
  3. root
  4. enamel
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14
Q

describe the periodontal membrane

A

attaches tooth to underlying bone in a gomphosis joint, a fibrous joint made of dense regular connective tissue

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15
Q

describe dentin

A

mineralized substance that makes up the majority of the tooth

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16
Q

describe the root of a tooth

A

contains nerves and blood vessels

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17
Q

describe enamel

A

covers the crown, which is the part of the tooth visible above the gum, is the hardest substance in the body and mineralized

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18
Q

can enamel be resynthesized?

A

no, it can not be resynthesized once worn away

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19
Q

describe the tongue, including muscle type and epithelial type

A

skeletal muscle for voluntary movement, covered with stratified squamous epithelium, contains tastebuds which allow animal to distinguish between harmful and proper food

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20
Q

what happens in the pharynx?

A

contraction of the tongue will fold epiglottis over the larynx to direct food/water to the stomach

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21
Q

where is the esophagus?

A

extends from the pharynx to the stomach

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22
Q

what muscle and epithelium make up the esophagus?

A

skeletal muscle, stratified squamous epithelium

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23
Q

where is the cardiac sphincter and what muscle is it composed of?

A

smooth muscle, at the junction on esophagus and stomach

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24
Q

what is the role of the cardiac sphincter?

A

keeps food from returning to esophagus

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25
Q

is the cardiac sphincter present in ruminants? equines?

A

not present in ruminants due to regurgitation, so well developed in equines that it is almost impossible to vomit

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26
Q

what epithelium lines the stomach?

A

simple columnar

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27
Q

what muscle makes up the stomach?

A

smooth muscle

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28
Q

list and describe the 2 curvatures of the stomach

A
  1. lesser curvature: attached to liver

2. greater curvature: situated caudally, not attached to anything

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29
Q

what does the pyloric sphincter connect?

A

stomach to duodenum

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30
Q

what is the role of the pyloric sphincter?

A

keep contents of stomach from moving immediately into duodenum and keep contents of duodenum from returning to stomach

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31
Q

what muscle makes up the pyloric sphincter?

A

smooth muscle

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32
Q

list the 4 compartments of the ruminant stomach

A
  1. reticulum
  2. rumen
  3. omasum
  4. abomasum
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33
Q

where does the esophagus empty in ruminants?

A

into the space between the reticulum and rumen

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34
Q

describe the locations and insides of the reticulum

A

most cranial compartment, sits right against the diaphragm, honeycomb inside

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35
Q

describe the function and epithelium of the reticulum

A

lined with stratified squamous epithelium, traps foreign material

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36
Q

which is the largest ruminant stomach compartment?

A

the rumen, takes up the majority of the left side of the abdomen

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37
Q

what is the function, epithelium, and special thing about the rumen?

A

microbial fermentation, stratified squamous, has tiny papillae projections

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38
Q

what does the inside of the omasum look like?

A

sheets

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39
Q

give the function and epithelium of the omasum

A

thin sheets filter by particle size, stratified squamous epithelium

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40
Q

what is the only ruminant stomach compartment not lined with stratified squamous epithelium, and what epithelium does line it?

A

the abomasum, simple columnar epithelium

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41
Q

what is the function of the abomasum?

A

same as the monogastric stomach, chemical digestion

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42
Q

what epithelium lines the small intestine?

A

simple columnar

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43
Q

list and describe the 3 parts of the small intestine

A
  1. duodenum: connected to stomach via pyloric sphincter; receives ducts from pancreas and gallbladder
  2. jejunum: longest part; site of digestion and absorption of digested nutrients
  3. ileum: connects to large intestine
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44
Q

what is the epithelial surface of the small intestine arranged into?

A

small projections called villi

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45
Q

what are microvilli?

A

projections on surface of each epithelial cell

46
Q

what is the role of villi and microvilli?

A

to increase the surface area for absorption

47
Q

what are all 3 components of the large intestine lined with?

A

simple columnar epithelium

48
Q

what is the cecum?

A

the blind pouch where the large intestine and ileum join

49
Q

list and describe the 3 parts of the colon

A
  1. ascending colon: runs back up cranially
  2. transverse colon: runs across body
  3. descending colon: runs down caudally
50
Q

what is the anus? what epithelium lines it?

A

the external opening at the end of the digestive tract; stratified squamous

51
Q

what is different about the avian mouth?

A

no teeth

52
Q

what is different about the avian esophagus?

A

it enlarges into the crop, then reforms and leads to the proventriculus

53
Q

what does the avian crop do?

A

stores and moistens food

54
Q

what does the avian proventriculus do?

A

where chemical digestion starts

55
Q

what does the avian gizzard do?

A

mechanical digestion; swallowed grit is their form of chewing here

56
Q

are there species variations between mammalian and avian small intestine?

A

none

57
Q

how does the avian large intestine differ from the mammalian?

A

paired ceca, small colon (no ascending, descending, or transverse

58
Q

list 3 accessory components of all digestive tracts

A
  1. mesenteries
  2. lesser omentum
  3. greater omentum
59
Q

describe and give epithelium of mesenteries

A

membranes continuous with visceral peritoneum, composed of simple squamous epithelium, holds intestines in place

60
Q

describe what the lesser omentum connects an is attached to, and epithelial type

A

membrane that connects stomach to liver, attached to lesser curvature of stomach, simple squamous epithelium

61
Q

describe what the greater omentum connects to, covers, and give connective tissue type

A

connected to greater curvature of stomach, covers ventral surface of abdominal cavity, composed of adipose tissue

62
Q

how many pairs of and what is the function of the salivary glands?

A

3 main pairs, produce saliva

63
Q

list and give location of the 3 main salivary glands

A
  1. parotid gland: ventral to ear; parotid duct runs under mandible to mouth
  2. mandibular gland: caudal to mandible
  3. sublingual gland: ventral to tongue
64
Q

list and give the locations of 3 accessory glands of the digestive tract

A
  1. pancreas: alongside duodenum
  2. liver: largest gland in body, lobed, sits caudal to diaphragm
  3. gallbladder: dorsal side of liver
65
Q

give the function of the gallbladder, and do horses have?

A

stores bile produced by liver, horses don’t have

66
Q

list the 2 types of contraction/movement of the digestive tract

A
  1. peristalsis

2. segmentation

67
Q

describe peristalsis

A

unidirectional waves of contraction that propel contents down digestive tract, contraction on cranial side to push down

68
Q

describe segmentation

A

back and forth mixing of contents of digestive tract, alternating areas of contraction

69
Q

what is prehension?

A

animals using lips, tongue, and/or teeth to obtain food/water

70
Q

what is mastication?

A

when food is reduced to smaller pieces by chewing and mixed with saliva

71
Q

what 3 things make up saliva?

A

water, mucus, enzymes

72
Q

list and describe 2 enzymes in salive

A
  1. lysozyme: antibacterial

2. alpha amylase: starts to digest starch

73
Q

is alpha amylase found in ruminants or carnivores?

A

no

74
Q

what is deglutition?

A

the process of swallowing

75
Q

list and describe the 3 steps of deglutition

A
  1. passage of food through the mouth: food is chewed and mixed with saliva and formed into a bolus, tip of tongue moves to roof of mouth, which pushes food bolus up and back towards pharynx
  2. passage through pharynx: contractions of the tongue fold epiglottis over trachea= no breathe while swallow, peristaltic contractions move food through pharynx
  3. passage through esophagus: peristaltic contractions propel food down esophagus and into stomach, very quick process
76
Q

list and describe the 4 steps of rumination

A
  1. regurgitation: food bolus returns to mouth via reverse peristalsis
  2. remastication: food is thoroughly chewed
  3. reinsalvation: food is mixed with more saliva
  4. redeglutition: food returns to stomach
77
Q

which steps of rumination occur at the same time?

A

remastication and reinsalvation

78
Q

what does rumination allow ruminants to do?

A

obtain a lot of food quickly and then digest in safety

79
Q

where does microbial fermentation occur?

A

in the rumen in ruminants and in the cecum in hindgut fermentors

80
Q

what do microbes have to break down cellulose?

A

cellulase

81
Q

what is cellulose?

A

the main fiber component of food

82
Q

what do microbes release after breaking down cellulose? (2)

A
  1. volatile fatty acids: acetate, proprionate, and butyrate, which are absorbed via rumen wall
  2. gases: CH4 (methane), and CO2
83
Q

what is eructation?

A

removes gases; belching

84
Q

what is bloat? how to fix?

A

occurs when gases build up in rumen due to failure of eructation, pass a tube down the esophagus to fix

85
Q

how do microbes alter fat?

A

by converting unsaturated fatty acids into saturated fatty acids

86
Q

what do microbes do to protein?

A

break down protein and synthesize microbial proteins

87
Q

list and describe the 3 phases of the stomach/abomasum secreting gastric juice

A
  1. cephalic phase: gastric juice secreted due to the smell, sight, or food entering the mouth in preparation for consumption
  2. gastric phase: juice secreted due to presence of food in stomach
  3. intestinal phase: duodenum secretes gastric inhibitory peptide, which inhibits gastric juice secretion
88
Q

what is gastric juice?

A

a combination of the secretions of cells in the stomach

89
Q

list and describe the 2 things that parietal cells in the stomach secrete for gastric juice

A
  1. HCl: very acidic, kills bacteria, denatures protein

2. Intrinsic factor: binds to vitamin B12 and allows for its absorption

90
Q

list and describe the 3 things that chief cells in the stomach secrete for gastric juice

A
  1. gastric lipase: breakdown of fat
  2. pepsin (from pepsinogen: breaks down protein
  3. rennin: only found in young ruminants, coagulates milk for slower passage through tract for nutrient absorption
91
Q

what is emesis?

A

the emptying of the stomach towards the mouth, a protective measure; species variations in ease/difficulty

92
Q

can ruminants perform emesis?

A

they can, but it will be the contents of the abomasum entering the omasum and forward for neutralizing, won’t see outside of body

93
Q

when does the duodenum secrete hormones?

A

when partially digested material enters

94
Q

list and describe the 3 hormones the duodenum secretes

A
  1. gastric inhibitory peptide: inhibits gastric juice secretion
  2. secretin: acts on pancreas to secrete bicarbonate, which makes contents less acidic
  3. cholecystokinin (CCK): acts on pancreas to secrete digestive enzymes and on gallbladder to secrete bile
95
Q

list and describe the 3ish enzymes released by the pancreas

A
  1. amylase: breaks down carbohydrates
  2. lipase: breaks down fat
  3. trypsin and chymotrypsin: break down protein
96
Q

what is the function of bile?

A

emulsifies fat in small intestine, allows for digestion and free movement of fat in small intestine

97
Q

what is bile made of and what does this mean?

A

a lipid material; won’t mix well with aqueous environment

98
Q

where does absorption occur?

A

along the epithelial surface of jejunum

99
Q

where are transporters for nutrients found in the jejunum?

A

along the intestinal villi

100
Q

list and describe the 4 things that are absorbed in the jejunum

A
  1. glucose: major carbohydrate
  2. amino acids: from protein
  3. fatty acids: from fat digestion
  4. vitamins and minerals
101
Q

which 3 of the things that are absorbed in the jejunum enter the hepatic portal system?

A

glucose, amino acids, vitamins and minerals

102
Q

where do fatty acids go after absorption?

A

to the lymphatic system

103
Q

describe the hepatic portal system

A

blood returning from the heart takes a pit stop at the liver first, and then reforms capillaries

104
Q

what does the hepatic portal system allow the liver to do?

A

choose what happens with nutrients

105
Q

what does the lymphatic system do with fatty acids?

A

causes fat to be pumped through body before entering bloodstream

106
Q

what is the function of the colon in everyone except hindgut fermentors?

A

water absorption

107
Q

what is the function of the colon in hindgut fermentors?

A

microbial fermentation to produce volatile fatty acids which are absorbed in the colon for use

108
Q

give 3 examples of hindgut fermentors

A

horses, rabbits, guinea pigs

109
Q

who do strong contractions of the descending colon do?

A

push contents into rectum, signaling the need to defecate

110
Q

what does the relaxation of the anal sphincter and contraction of abdominal muscles result in?

A

defecation