Digestive System Flashcards
1
Q
list and describe the 5 functions of the digestive system
A
- prehension: the act of obtaining food
- mastication: chewing, mechanical breakdown
- digestion: chemical breakdown
- absorption: smaller components entering rest of body
- elimination of solid wastes: as feces
2
Q
list the 4 layers of the wall of the digestive tract, from innermost to outermost
A
- mucosa
- submucosa
- muscularis
- serosa
3
Q
describe the mucosa
A
inner layer, epithelia lining
4
Q
list and give the locations and functions of the two types of epithelial linings of the mucosa
A
- stratified squamous epithelium: protective layer, prevents damage, mouth and esophagus
- simple columnar epithelium: more glandular for digestion and absorption
5
Q
what tissue composes the submucosa?
A
loose areolar connective tissue
6
Q
describe the two muscle types and their locations in the muscularis, plus the functions
A
- skeletal muscle: mouth and esophagus (chewing and swallowing)
- smooth muscle: rest of tract
circular and longitudinal layers allows for contraction in different directions and propulsion
7
Q
describe the serosa, including an alternate name and tissue type
A
outer layer, also called visceral peritoneum, simple squamous epithelium
8
Q
list the 3 components of the mouth
A
- labia/lips
- teeth
- tongue
9
Q
describe the labia/lips of the mouth
A
entrance to mouth, major species variation
10
Q
list and describe the 4 types of teeth from front of the mouth to the back
A
- incisors: cutting, prehension
- canines: tearing, mastication
- premolars: grinding, mechanical
- molars: fine grinding, mechanical
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
12
Q
how many upper incisors and canines do ruminants have?
A
zero!
13
Q
list the 4 structures of teeth
A
- periodontal membrane
- dentin
- root
- enamel
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
15
Q
describe dentin
A
mineralized substance that makes up the majority of the tooth
16
Q
describe the root of a tooth
A
contains nerves and blood vessels
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
18
Q
can enamel be resynthesized?
A
no, it can not be resynthesized once worn away
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
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
21
Q
where is the esophagus?
A
extends from the pharynx to the stomach
22
Q
what muscle and epithelium make up the esophagus?
A
skeletal muscle, stratified squamous epithelium
23
Q
where is the cardiac sphincter and what muscle is it composed of?
A
smooth muscle, at the junction on esophagus and stomach
24
Q
what is the role of the cardiac sphincter?
A
keeps food from returning to esophagus
25
is the cardiac sphincter present in ruminants? equines?
not present in ruminants due to regurgitation, so well developed in equines that it is almost impossible to vomit
26
what epithelium lines the stomach?
simple columnar
27
what muscle makes up the stomach?
smooth muscle
28
list and describe the 2 curvatures of the stomach
1. lesser curvature: attached to liver
| 2. greater curvature: situated caudally, not attached to anything
29
what does the pyloric sphincter connect?
stomach to duodenum
30
what is the role of the pyloric sphincter?
keep contents of stomach from moving immediately into duodenum and keep contents of duodenum from returning to stomach
31
what muscle makes up the pyloric sphincter?
smooth muscle
32
list the 4 compartments of the ruminant stomach
1. reticulum
2. rumen
3. omasum
4. abomasum
33
where does the esophagus empty in ruminants?
into the space between the reticulum and rumen
34
describe the locations and insides of the reticulum
most cranial compartment, sits right against the diaphragm, honeycomb inside
35
describe the function and epithelium of the reticulum
lined with stratified squamous epithelium, traps foreign material
36
which is the largest ruminant stomach compartment?
the rumen, takes up the majority of the left side of the abdomen
37
what is the function, epithelium, and special thing about the rumen?
microbial fermentation, stratified squamous, has tiny papillae projections
38
what does the inside of the omasum look like?
sheets
39
give the function and epithelium of the omasum
thin sheets filter by particle size, stratified squamous epithelium
40
what is the only ruminant stomach compartment not lined with stratified squamous epithelium, and what epithelium does line it?
the abomasum, simple columnar epithelium
41
what is the function of the abomasum?
same as the monogastric stomach, chemical digestion
42
what epithelium lines the small intestine?
simple columnar
43
list and describe the 3 parts of the small intestine
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
44
what is the epithelial surface of the small intestine arranged into?
small projections called villi
45
what are microvilli?
projections on surface of each epithelial cell
46
what is the role of villi and microvilli?
to increase the surface area for absorption
47
what are all 3 components of the large intestine lined with?
simple columnar epithelium
48
what is the cecum?
the blind pouch where the large intestine and ileum join
49
list and describe the 3 parts of the colon
1. ascending colon: runs back up cranially
2. transverse colon: runs across body
3. descending colon: runs down caudally
50
what is the anus? what epithelium lines it?
the external opening at the end of the digestive tract; stratified squamous
51
what is different about the avian mouth?
no teeth
52
what is different about the avian esophagus?
it enlarges into the crop, then reforms and leads to the proventriculus
53
what does the avian crop do?
stores and moistens food
54
what does the avian proventriculus do?
where chemical digestion starts
55
what does the avian gizzard do?
mechanical digestion; swallowed grit is their form of chewing here
56
are there species variations between mammalian and avian small intestine?
none
57
how does the avian large intestine differ from the mammalian?
paired ceca, small colon (no ascending, descending, or transverse
58
list 3 accessory components of all digestive tracts
1. mesenteries
2. lesser omentum
3. greater omentum
59
describe and give epithelium of mesenteries
membranes continuous with visceral peritoneum, composed of simple squamous epithelium, holds intestines in place
60
describe what the lesser omentum connects an is attached to, and epithelial type
membrane that connects stomach to liver, attached to lesser curvature of stomach, simple squamous epithelium
61
describe what the greater omentum connects to, covers, and give connective tissue type
connected to greater curvature of stomach, covers ventral surface of abdominal cavity, composed of adipose tissue
62
how many pairs of and what is the function of the salivary glands?
3 main pairs, produce saliva
63
list and give location of the 3 main salivary glands
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
list and give the locations of 3 accessory glands of the digestive tract
1. pancreas: alongside duodenum
2. liver: largest gland in body, lobed, sits caudal to diaphragm
3. gallbladder: dorsal side of liver
65
give the function of the gallbladder, and do horses have?
stores bile produced by liver, horses don't have
66
list the 2 types of contraction/movement of the digestive tract
1. peristalsis
| 2. segmentation
67
describe peristalsis
unidirectional waves of contraction that propel contents down digestive tract, contraction on cranial side to push down
68
describe segmentation
back and forth mixing of contents of digestive tract, alternating areas of contraction
69
what is prehension?
animals using lips, tongue, and/or teeth to obtain food/water
70
what is mastication?
when food is reduced to smaller pieces by chewing and mixed with saliva
71
what 3 things make up saliva?
water, mucus, enzymes
72
list and describe 2 enzymes in salive
1. lysozyme: antibacterial
| 2. alpha amylase: starts to digest starch
73
is alpha amylase found in ruminants or carnivores?
no
74
what is deglutition?
the process of swallowing
75
list and describe the 3 steps of deglutition
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
list and describe the 4 steps of rumination
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
which steps of rumination occur at the same time?
remastication and reinsalvation
78
what does rumination allow ruminants to do?
obtain a lot of food quickly and then digest in safety
79
where does microbial fermentation occur?
in the rumen in ruminants and in the cecum in hindgut fermentors
80
what do microbes have to break down cellulose?
cellulase
81
what is cellulose?
the main fiber component of food
82
what do microbes release after breaking down cellulose? (2)
1. volatile fatty acids: acetate, proprionate, and butyrate, which are absorbed via rumen wall
2. gases: CH4 (methane), and CO2
83
what is eructation?
removes gases; belching
84
what is bloat? how to fix?
occurs when gases build up in rumen due to failure of eructation, pass a tube down the esophagus to fix
85
how do microbes alter fat?
by converting unsaturated fatty acids into saturated fatty acids
86
what do microbes do to protein?
break down protein and synthesize microbial proteins
87
list and describe the 3 phases of the stomach/abomasum secreting gastric juice
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
what is gastric juice?
a combination of the secretions of cells in the stomach
89
list and describe the 2 things that parietal cells in the stomach secrete for gastric juice
1. HCl: very acidic, kills bacteria, denatures protein
| 2. Intrinsic factor: binds to vitamin B12 and allows for its absorption
90
list and describe the 3 things that chief cells in the stomach secrete for gastric juice
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
what is emesis?
the emptying of the stomach towards the mouth, a protective measure; species variations in ease/difficulty
92
can ruminants perform emesis?
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
when does the duodenum secrete hormones?
when partially digested material enters
94
list and describe the 3 hormones the duodenum secretes
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
list and describe the 3ish enzymes released by the pancreas
1. amylase: breaks down carbohydrates
2. lipase: breaks down fat
3. trypsin and chymotrypsin: break down protein
96
what is the function of bile?
emulsifies fat in small intestine, allows for digestion and free movement of fat in small intestine
97
what is bile made of and what does this mean?
a lipid material; won't mix well with aqueous environment
98
where does absorption occur?
along the epithelial surface of jejunum
99
where are transporters for nutrients found in the jejunum?
along the intestinal villi
100
list and describe the 4 things that are absorbed in the jejunum
1. glucose: major carbohydrate
2. amino acids: from protein
3. fatty acids: from fat digestion
4. vitamins and minerals
101
which 3 of the things that are absorbed in the jejunum enter the hepatic portal system?
glucose, amino acids, vitamins and minerals
102
where do fatty acids go after absorption?
to the lymphatic system
103
describe the hepatic portal system
blood returning from the heart takes a pit stop at the liver first, and then reforms capillaries
104
what does the hepatic portal system allow the liver to do?
choose what happens with nutrients
105
what does the lymphatic system do with fatty acids?
causes fat to be pumped through body before entering bloodstream
106
what is the function of the colon in everyone except hindgut fermentors?
water absorption
107
what is the function of the colon in hindgut fermentors?
microbial fermentation to produce volatile fatty acids which are absorbed in the colon for use
108
give 3 examples of hindgut fermentors
horses, rabbits, guinea pigs
109
who do strong contractions of the descending colon do?
push contents into rectum, signaling the need to defecate
110
what does the relaxation of the anal sphincter and contraction of abdominal muscles result in?
defecation
