Digestion General Revision Flashcards
(246 cards)
1
Q
Describe the layers in the wall of the alimentary canal and what is found within them?
A
Mucosa: glands, transport
Submucosa: blood vessels, nerves
Muscularis externa: concentrical and longitudinal - for mixing and peristalsis
Serosa: outer connective tissue
2
Q
What is the difference between and intrinsic and an extrinsic glans
A
Intrinsic: in wall, don’t need duct
Extrinsic: outside wall, require duct
3
Q
Define the nine regions of the abdomen moving right to left, caudally.
A
r. hypochondria –> xipoid –> l. hypochondria
r. flank –> umbilical –> l. flank
r. inguinal –> pubic –> l.inguinal
4
Q
What are the lateral body wall muscles?
A
- internal abdominal oblique: ilium –> thorax
- external abdominal oblique: lumbar region to pubis
- transverse abdominal
5
Q
What are the ventral muscles of the abdomen?
A
l&r rectus abdominus
6
Q
What colour and consistency is peritoneal fluid and when and how much is it produced?
A
Viscous and straw coloured
small volume: 1-2ml
Constantly produced, lymphatics drain
7
Q
What is the role of the ameloblast?
A
Makes enamel - hardest biological substance
stops after eruption
8
Q
What does the odontoblast do?
A
Produces cementum - continues after eruption
9
Q
What is the difference between secondary and tertiary dentine - do they take up stain?
A
Secondary dentine is laid down after eruption, narrows pulp cavity - takes up stain
Tertiary in response to injury, no pigment
10
Q
Where is cementum found in brachydont and hypsodonts? What produces them?
A
Brachydont: cemetum around neck and root of tooth in gingiva
Hypsodont: cementum covering lateral exposed surfaces of tooth and infundibulum
Cementoblasts produce cementum –> strength and bulk of cell. Allows anchorage to periodontal ligament. Some remain in tooth.
11
Q
What is the periodontal ligament?
A
Ligament joining the cementum to the alveolar bone. Made of collagen fibres with cemetoblasts and osteoblasts
12
Q
Outline the steps in tooth development
A
oral cavity lined by ectoderm
1) thickening of ectoderm and invagination = dental bud
2) cap stage and enamel organ development
3) bell stage: differentiation, forming primordium for permanent tooth, dental same with tooth
4) roots grow, pushing teeth up - eruption = loss of ameloblasts/enamel organ
primordium of permanent tooth grows = pressure on root of temporary = loss and replacement
13
Q
What teeth do not have a primordium?
A
Molars - no milk teeth
14
Q
What species has 3131/3121 as its formula?
A
A cat
15
Q
What does heterodont mean?
A
Different shaped teeth with different functions (incisors, canines, premolars, molars)
16
Q
How many teeth does a dog have - what is the formula
A
42 teeth. 3142/3143.
17
Q
What are shearing teeth?
A
Upper 4th premolar
Lower 1st molar
in a dog has two different surfaces
18
Q
How many roots do tricuspid incisors have? In what species are they found?
A
Dog
1 root
19
Q
Is a pig hypsodont or brachydont?
A
Both
has a hypsodont tusk (canine) and brachydont cheeck teeth and incisors
20
Q
What is the pigs dental formula?
A
3143/3143
21
Q
What are needle teeth, how many are there?
A
Teeth that pig is born with, very sharp, 8 of them.
22
Q
What kind of teeth are found in horses?
A
Hypsodont and brachydont (canines, long reserve crown but not continuous growth)
23
Q
On what side is the dental star found?
A
On the labial side
24
Q
What are the four shapes a horses incisors migrate through with age?
A
wider than long, rectangular
trapezoid
traingular
taller than long, rectangular
25
Do wolf teeth have deciduous precursors?
No, even though they are premolars
26
What is a horses dental formula? Why does it vary?
31(0)3(4)3/31(0)3(4)0
varies as not all horses have a canine (more common in males)
varies as not all horses have a/all wolf tooth (first premolar)
27
Why does a hook form in horse teeth?
The maxilla is wider than the mandible = occlusion on buccal side
28
When do deciduous teeth erupt and how are they different to their permanent replacements?
```
Much whiter and smaller
6 days (medial) --> 6 weeks --> 6 months
```
29
What kind of teeth do ruminants have?
brachydont (lower incisors and canines) and hypsodont
30
What is the dental formula of a ruminant?
0033/3133
31
With no upper incisors how does a ruminant prehend food?
dental pad of maxilla - keratinised
| head movement helps in prehension
32
What is the dental formula of a camelid. What type of teeth do they have?
111(2)3/311(2)3
| Brachydonr
33
What kind of teeth do rabbits have? What are peg teeth?
| What is their dental formula?
They have aradicular hypsolodont teeth
Peg teeth are their caudal pair of incisors of maxilla
2033/1023
as no canines - long diastema
34
What type of teeth are found in rodents? What does this depend on?
Their diet - of omnivorous= brachydont, if herbivorous = hypsodont
They don't have peg teeth or deciduous teeth. But are ridiculer and have yellow pigment.
35
What arch is found near the palatine tonsil?
Palatoglossal - forms lateral base of the tongue
36
What are the muscles of the lip innervated by?
Fascial nerve 7
37
What is the role of the caninus?
Causes expression of the canines
38
Outline the passage of food and air from the oral cavity and nasal cavity to the oesophagus and trachea respectively:
Food: oral cavity, ventral to har palate and soft palate, into oropharynx --> intrapharyngeal ostium --> laryngopharynx --> oesophagus (epiglottis closed)
Air: nasal cavity: dorsal to hard and soft palate --> nasopharynx --> intrapharyngeal osmium --> larynx --> trachea (epiglottis open)
39
What is the role of the Hyoid Apparatus?
Sits behind ear and laryngeal cartilages - opens airways, suspends larynx from skull, attaches tongue
40
Name the four mechanical papillae on the tongue and where they are found
filiform - everywhere, small, caudal projection
conical - larger than filiform, root/torus lingue
lentiform - round on torus lingo (ox)
marginal - neonatal for suckling
41
Name the three gustatory papillae and where they are found
fungiform - mushroom
foliate - lateral margin near palatoglossal arch (not gust. in cats, absent in ox)
vallate - flattened with sulcus, junction of body and neck
42
What nerves innervate the taste buds?
Rostral 2/3: cranial nerve 7 fascial
| Caudal 1/3: cranial nerve 9 glossopharyngeal
43
Name the four major muscles of the tongue
genioglossus: tongue to mandible
geniohyodeus: mandible to hyoid
hyoglossus: hyoid to tongue
styloglossus: tongue to styloid?
mylohyoideus (more ventral than geniohyoidues and perpendicular): left to right
44
What are the extrinsic muscles causing tongue movement?
- originating outside of tongue
| hyoid (stylo and hyoglossus) or mandible (genioglossus) - depress, retract or protrude tongue
45
What are the mechanical part of the tongue innervated by?
Cranial nerve 12 (hypoglossal)
46
What are the three jaw closing muscles?
temporalis
masseter
pterygoid
47
What causes jaw opening?
gravitation
| digastricus muscle
48
What two muscles are larger in herbivores? Why?
pterygoids and masseter - need more grinding action
49
What are the three main classes of muscle in the pharynx?
dilators, constrictors and shorteners - to move food
50
What are the muscles of the pharynx innervated by?
vagus and glossopharyngeal
51
Describe the vomiting pathway
Salivation: neutralising acid
Swallowing: relaxes G-O sphincter, neutralises stomach contents
- Retching: contract of abdom and diaphragm with closed glottus = increase in pressure
- Retrograde contraction
- Relaxation of stomach and spincter
--> expulsion
52
How can you tell the difference between diarrhoea from the large and small intestine?
Small: concurrent vomiting, digested blood (melena), urgent
Large: straining (tenesmus), not digested blood (haematochezia), mucoid faeces
53
What does melena and haematochezia mean?
Melena: digested blood in faeces
Haematochezia: undigested blood in faeces
54
What is more common a ventrodorsal or dorsoventral radiograph? What does it mean?
Ventrodorsal. Animal lying on its back - allows for imaging of abdomen
55
What are the five opacities seen on X-ray and what type of tissue/substance do they correlate to?
```
Black = gas
Dark grey = fat
grey = fluid and soft tissue
light grey = bone
white = metal
```
56
What is ileus?
Lack of peristalsis
57
When assessing a dogs small intestine, what is the rule of thumb for distension?
- diameter no larger than 1.6x body of L5
| - no loop greater than 2x width of others
58
When assessing a cats small intestine, what is the rule of thumb for distension?
- no greater than 12mm
| - no larger than 2x L4
59
What are oral defines mechanisms?
- oral mucosa (integrity and tight gingival cuff)
- lymphoid system (in lamina propia)
- saliva (peroxidases, lysozymes, histatins, IGs, volume)
- chevicular fluid (from sulcus)
- chewing/swallowing
- tooth anatomy
60
What is xerostomia
significant decrease in saliva, will decrease appetite and taste
Causes:
- autoimmune
- chronic renal disease, diabetes mellitus, hypertension
61
What is chevicular fluid?
Inflammatory exudate from sulcus epithelium
| Contains: Ig's, macrophages, T&B cells
62
What causes periodontal disease?
Its mulfactorial but bacteria are the primary agent.
| Progressed ginigivitis
63
What is the difference between gingivitis and periodontitis?
Gingivitis: inflamed gingiva
Periodontitis: attachment loss periodontal ligament gone, irreversible
64
What is the pellicle?
Protein film on enamel of tooth - glycoproteins bind - make it favourable for bacteria to attach, but prevent deposition of salivary calcium phosphate
65
How does plaque form?
Plaque is a mass of bacteria adhering to the pellicle of a tooth - initially aerobic bacteria, gram positive, if not disrupted, continue to colonise and anaerobic bacteria migrate into gingival sulcus, releasing toxins and causing inflammation (gingivitis)
After >10 days, mature and gram negative bacteria colonise
It is a biofilm
66
What is calculus?
It is the mineralised form of plaque
67
What factors predispose animals to periodontitis?
- tooth crowding or malocclusions - gingiva is not as intact
- retention of deciduous teeth
- mouth breathing and xerostomia
- diet - if not abrasive enough to remove plaque
- concurrent disease
68
Apart from oral lesions what can periodontal disease cause?
Can have systemic effects
- increases risk of heart disease
- preterm, low weight babies
- osteoporosis, arthritis
69
What are the direct consequences of PD?
Attachment loss
- it is disease of bone = tooth mobility and loss
- -> osteomyelitis,
- -> pathologic fractures
- -> oronasal fistula formation (hole)
- -> bacteraemia
70
What is exodontia?
Tooth extraction
71
Can homecare get rid of plaque?
Not if already there - need dental for mechanical and chemical destruction of the biofilm
72
What is feline tooth resorption?
A disease of cementum, dentine and enanel
| - most of it occurs within the gingival, progressive resorption of the tooth
73
How can feline tooth resorption be identified in a clinical examination?
Easily missed - some inflammation at cement-enamel junction/gingiva
Also easily confused with furcation exposure/catching on tooth with multiple roots
Need X-ray
74
What does feline tooth resorption cause in the animal?
Anorexia, lethargy, depression, dysphagia
| It is painful - will not want to eat
75
What is being resorbed in Feline TR? How does this progress?
The odontoclasts
- resorptive phase: dentine and cementum
- reparative: deposition of bone and cementum into defects
76
What is the cause of Feline TR?
multifactorial - not exactly sure
- low calcium diet
- calicivirus
- high vit. A, D
77
How is feline TR treated?
Unsure, no effective treatment as of yet --> exodontia
78
What are the two broad classes of salivary glands - what do they secrete and where are they found?
mucous and serous glands
Mucous: scattered in lips, cheeks, soft plate and tongue - intrinsic glands --> carbohydrate rich secretions
Serous: large extrinsic glands not in oral cavity directly --> watery, protein secretions
79
What does the parotid gland secrete? Where is it found and where does it open into?
Parotid - serous saliva (except dog)
Found ventral to ear, very large in herbivores
Runs differently in different species
- dog: lateral surface of master
- horse/ox: medial/ventral border of mandible
Opens: into vestibule at upper 4th premolar
80
Where is the mandibular salivary gland found and where does it open into?
What does it secrete?
At jaw angle, underneath parotid (deeper)
Opens into sublingual caruncle near frenulum
Mixed secretion
81
Where is the sublingual salivary gland found? How many ducts does it have? What and where does it open?
Sublingually with duct running along frenulum into caruncle
Most species have polystomatic ducts
Mixed secretion
82
What species have a zygomatic salivary gland? Where does originate from and where does it open?
Dogs and cats/Carnivores
Medial to zygomatic arch
Opens opposite last upper molar
Mainly mucous secreting
83
What are acini?
Clusters of secreting cells aggregated around a lumen with a basement membrane
84
How does saliva get from the acinus to the mouth/oral cavity
Acinus --> intercalated duct --> striated duct --> interlobular duct --> primary duct
85
How do mucous secreting acini differ from serous secreting ones?
Mucous: swollen cells, pale, flattened basal nuclei
Serous: pyramidal, basophilic cytoplasm, round basal nuclei
86
Histologically how do the ducts change from intercalated to striated to interlobular?
Intercalated: low cuboidal epithelium
Striated: columnar with basal striations due to mitochondria
Interlobular: simple to stratified columnar
87
What salivary glands are innervated by the fascial (7) nerve?
mandibular, sublingual, buccal and zygomatic
88
What salivary glands are innervated by the glossopharyngeal (9) nerve?
Parotid
89
Explain the mechanism of Deglutition in six steps
Food bolus: mastication, salivation = preparation
1) tongue against palate
2) rapid contraction of mylohyoideus and extrinsic tongue muscles = to pharynx
3) contact pharyngeal mucosa = reflexes
4) soft palate raised, glottis closed, hyoid rostral (pharyngeal shorteners)
5) bolus to oesph. (pharngeal constrictors)
6) peristalsis to stomach
90
How is deglutition initiated and then continued?
Voluntarily, then taken over by reflexes in the pharynx
91
What are the three segments of the oesophagus?
1) cervical: pharynx - thoracic inlet. Dorsal to larynx, follows trachea, left lateral to dorso-medially
2) thoracic: in mediastinum of thorax, over base of heart, penetrates oesophageal hiatus of diaphragm
3) abdominal: short, passes over dorsal border of liver = groove. Joins stomach dorsally to cardia
92
What is the oesophageal hiatus of the diaphragm?
A hole/trochanter? through which the oesophagus passes from thorax into abdominal cavity
93
What kind of epithelium is found in the oesophagus? In which animals is it keratinised
Stratified squamous epithelium
Keratinised in horses, ruminants
Non-keratinised: carnivores
94
What is found in the lamina propria of the oesophagus?
Collagen and elastic fibres, leukocytes, submucosal glandular ducts
95
What role does the muscular mucosae play?
Some species not in entire oesophagus, mostly caudal end
| for localised movement of mucosa - not food
96
Where are glands found within the oesophagus? What do they secrete?
Submucosa
Mucus glands
Cranial end of oesophagus (dog - full length)
97
What is the role of the cranial and caudal oesophageal sphincters?
They are capable of maintaining intra luminal pressure higher than gastric = movement into stomach
98
What layers is the muscularis external composed of? Is it skeletal or smooth?
Mostly two layers: inner = circular, outer = longitudinal
Dogs and ruminants: all skeletal
Others: skeletal cranial, smooth caudal 1/3
99
Where would one find adventitia? What about serosa?
Both outermost layers of oesophagus wall
Adventitia only in cervical segment, connective tissue merges with that of surrounding structures
Serosa: in thorax and abdominal segment - connective tissue covered by epithelial layer
100
What supplies the oesophagus with blood?
Carotid
bronchooesphageal
left gastric arteries
101
What nerves innervate the oesophagus?
Sympathetic and vagus
102
What are some common sites of obstruction?
cranial and caudal oesophagus
thoracic inlet
over the base of the heart
immediately anterior to diaphragm hiatus
103
What is the compound stomach? Where does it sit and in what species?
It is a fermentation chamber: allows breakdown of CHO by microorganisms
In ruminants
3/4 abdominal cavity
104
What are the four compartments of compound stomach, give very brief description of each.
Forestomachs = non glandular
1) reticulum - sieve for coarse material, VFA absorption
2) rumen - mixing, fermentation by microbes --> VFA, absorption: VFA, Na+, H20
3) omasum - absorption VFA, H20, Na+, sieve
True/Glandular Stomach = Abomasum - digestive enzymes for digestion
105
What is found on the left lateral side of the ox's abdomen?
reticulum, dorsal and ventral rumen sac,
| funds of abomasum
106
What is found on the right lateral side of the ox's abdomen?
Mostly covered by omentum and liver if removed
- reticulum
- omasum
- abomasum with pyloric region (pts. upwards)
- descending duodenum
107
Where is the reticulum located? Is it large?
Mostly left
passes over midline ventral above xiphoid process
cardia to most forward pt of diaphragm
108
What are the surfaces of the reticulum?
visceral: flat against rumen
diaphragmatic: convex against diaphragm and liver
ventral: contact with sternal diaphragm, liver, omasum, abomasum
109
What are the three opening in the reticulum internally?
1) cardia: slit like, oesophagus in
2) ruminoreticular orifice: wide opening
3) reticulo-omasal orifice: round at lower end of reticular groove
110
What is the reticular groove and how is it different to the rest of the reticulum?
Found on the medial wall - runs from the cardia to reticular omasal orifice
Mucosa is smooth and pale
Used for passage of milk
111
Is the mucosal surface of the reticulum folded?
Yes has primary and secondary folds giving honey comb structure
- primary: green brown. 1cm tall, honeycomb
- secondary: low papillae in the cells of honeycomb
112
What can be seen histologically in the wall of the reticulum?
All normal layers of Gi tract
some muscular mucosa
keratinised epithelium
113
What are the main functions of the reticulum
- sieve for material, coarse back to rumen, fine into omasum
| - absorbs fatty acids, water, salt
114
Where is the rumen found? Is it large? Can you palpate?
Left half of abdominal cavity, over midline.
80% of stomach capacity
Can palpate at dorsal left flank region and per rectum
115
What curvatures does the rumen have?
Dorsal: to sublumbar muscles
Ventral: lies on abdominal wall, mental burial in between
116
What are the two surfaces of the rumen?
```
Parietal = left: diaphragm, left of abdomen, spleen, greater omentum
Visceral = right, omasum, abomasum, intestines and liver. Many grooves demarcating into sacs
```
117
List the six sacs the rumen has
- dorsal
- ventral
- caudoventral blind sac
- caudodorsal blind sac
- cranial sac
- insula ruminis - elliptical area not a proper sac
118
What do the external grooves correspond to internally?
Correspond to pillars - bands of smooth muscle
119
What is luminal tympany?
Gas found in the rumen with distension
| normally removed by eructation
120
What is the ventricular atrium?
Where the oesophagus enters the stomach
121
What is the ruminal atrium?
Area caudal to ruminal-reticular fold
122
What is the internal surface of them rumen like? How does this vary depending on blind sacs or ventral/roof surface
Has papillae with varying heights - depends on age, diet an location
- dorsal/ventral blind sacs: long and numerous
- ventral: fewer and less prominent
- roof: short and absent
123
What is the main function of the rumen?
To mix ingesta and ferment ingest --> VFA
| Absorb VFA, H20 and salts
124
What role do papillae play in the rumen?
- mix and increase SA for absorption
| - heating rods = increased speed of fermentation
125
Is there muscularis mucosae in the papillae of the rumen?
No
126
What is the omasum also known as? Why?
Butcher bible. Has omasal laminae - four different sized parallel folds from greater curvature
127
What are inter laminal recesses?
Space between the folds
128
Where is the omasum located? Is it large?
Located right of midline, has liver and body wall to its right.
It is the smallest compartment in sheep and goats.
129
Where is the greater curvature found?
Dextrocaudally
130
What does the lower pole attach to?
Fundic region of abomasum and around omaso-abomasal orifice
131
What is the right surface covered by?
Lesser omentum
132
What are the two openings in the omasum?
1) reticulo-omasal orifice
| 2) omasal-abomasal orifice
133
What is the omasal groove? What is the mucosa like?
Runs between two openings at floor
| Smooth mucosa with few ridges
134
Are papillae found in the omasum? And if - is mucosa muscularis present?
Yes cover surface and have extensive muscular mucosae
135
What are the functions of the omasum?
Absorption: VFA, H20, salts
Pumping: two stage, from reticulum to abomasum
Sieve
136
What is the abomasum?
The true stomach
| elongated on abdominal floor, between ventral sac of rumen and reticulum
137
What is the cranial pole of the abomasum? What is it attached to?
Fundus and body of abomasum
| - connected to reticulum, ruminal atrium and ventral sac of rumen by muscle
138
What is the caudal pole of the abomasum and where does it pass to?
Pyloric region. Narrower
| Abomasum transverses to right, terminates at pylorus. Caudal to omasum
139
What two openings does it have?
1) omaso-abomaso orifice
| 2) pylorus
140
Describe the internal surface of the abomasum
dark mucosa
spiral folds (increase SA) decreasing near flexure
Folds form plug at orifice (oa) stop reflux
141
What is the torus?
The lesser curvature to narrow pyloric passage of the abomasum
Lighter mucosa
low rug with swelling
142
Is there muscularis external?
Yes surrounded by smooth muscle
thicker inner circular
thinner outer longitudinal
143
Is there serosa?
No - only at origin of omentum
144
What function does the abomasum have?
Many glands = digestive enzymes and acid = digestion and mucus for protection
145
What are the three segments of the gastric groove?
1) reticular groove: two prominent muscular folds
2) omasal groove: reticulo-omasal-abomasal orifice. not prominent muscular folds
3) Abomasal groove: not proper groove - no gastric folds along lesser curvature
146
How is the stomach supplied with blood?
By the celiac artery
147
What nerves innervate the stomach?
Dorsal and ventral trunks of vagus
148
Which of the caudoventral blind sacs is more caudal in sheep?
The dorsal blind sac
149
What are the two regions of the simple stomach that join?
- larger cardiac, fundic and body region - into which oesophagus opens. Sits on left, contacts diaphragm
- pyloric, narrower, thick wall. Passes to right into duodenum
150
What are the two surfaces of the stomach?
```
Parietal = to liver and diaphragm, concave
Visceral = to intestines, convex
```
151
What are the curvatures of the stomach?
Lesser: sharply concave, lesser omentum to left kidney lobe
Greater: convex, greater omentum, gastrosplenic ligament
152
What is the position of the stomach like?
More left but mainly transverse from left to right
153
What are the four regions of the stomach?
1) cardiac - around cardiac sphincter
2) fundic region - large, dorsal part
3) body - cardia to ventral angle
4) pylorus - right directed:
- pyloric antrum = proximal
- pyloric canal = more distal
- pyloric sphincter = into duodenum
154
What kind of membrane is the greater oment? What is it rich in? What is the omental bursa? Where does it open?
serous membrane, rich in fat, for protection
omental bursa - cavity formed by greater omentum, parietal and visceral layer
opens at epiploic foramen
155
What are the two parts of the lesser omentum?
1) hepatogastric ligament
| 2) hepatoduodenal ligament containing portal vein, hepatic artery, bile duct, lymphatic duct
156
Where does the blood supply stem from?
| What nerves supply the stomach?
From celiac artery
| Branches of Vagus and sympathetic nerves
157
What are the two different zones within the stomach? What is this determined by?
Gland distribution
- non-glandular/oesophageal: like oesophagus but with muscular mucosa, no glands
- glandular: fundic gland region, cardiac gland region, pylorus
158
Outline the four layers of the glandular stomach
a) mucosa: rugae, surface invaginations = gastric pits, simple columnar.
tubular glands in lamina propria to muscularis mucosae and some lymphoid follicles
b) submucosa: no glands, many blood vessels, collagen fibres, nerves
c) muscularis externa - 3 layers
inner oblique, middle circular (sphincter), outer longitudinal thin
d) serosa: reduce friction
159
On what basis its the glandular region of the stomach divided?
the types of glands present
160
What is the cardiac zone comprised of?
- simple columnar mucus secreting gastric pits
| - branched or coiled glands - cuboidal mucus secreting cells
161
What is the fundic zone composed of?
- gastric pits (simple columnar, mucus)
| - glands with neck, body and base
162
What cells are found in the glands of the fundic zone?
- upper 1/3: mucus neck = mucus producing, flat nuclei, basophilic cytoplasm
- body base: chief cells = pepsinogen producing (HCl makes pepsin), cuboidal/pyramidal, spherical nucleus, basophilic, apical is lacy and vacuolated
- all along: parietal, HCl producing, large occur singularly, eosinophil cytoplasm (mitochondria), pyramidal
difficult to see: endocrine cells --> gastrin, secretin, incl. enterochromaffin like cells (--> histamine)
163
What is found in the pyloric zone?
Deep gastric pits (half of mucosa thickness).
| branched, coiled short glands with mucous cells.
164
What is the right most portion of a dogs stomach?
The pyloric region, related to portal fissure of liver and pancreas
165
What shape does the dogs stomach have and where does it sit? What other species stomach is similar?
C- shaped
Sits if empty cranial to last rib, separated from ventral abdominal wall by liver and intestine
if distended can stretch past xiphoid and umbilical regions
Cat is similar
166
How much of the dogs stomach makes up funds region? What colour is the mucosa and what is prominent?
2/3
| thick, red brown mucosa with longitudinally oriented rugae
167
What is the pyloric region stained by post-mortem?
Regurgitated bile, normally thin and pale
168
What is the saccus caecus? In what animal is it found?
Large non-glandular region of the horses stomach, easily irritated, separated from glandular region by margo plicatus
169
What shape does the equine stomach make? What animal is similar?
Why can the horse not vomit?
J shape - like pig
| oesoph enters at acute angle with strong cardiac sphincter that closes with expansion of stomach
170
What is the left most extremity of the pig stimach
the fundic region - diverticulum
171
What is the pro ventricular region?
Around cardia of stomach - non glandular with number of folds, demarcated from rest of stomach
172
What colour is the cardiac gland region?
pale and grey, soft, thin
173
What is the torus pyloric?
Projection of tissue - lesser curvature into pylorus, glandular, strong fibro-muscular. Assists in sphincter closing,
174
What is the isthmus? In which species is it found?
In birds, separation of proventriculus and gizzard
175
How does GI smooth muscle function?
desmosomes and gap junction = syncytium with pacemaker cells can initiate action potential
circular and longitudinally orientated --> contraction = mixing and propulsion periodically release
176
How is the threshold of smooth muscle modulated, three mechanisms?
mechanically by stretch and by changes in quality of chyme (osmo/chemo receptors)
hormonally by gastrin
neurally by vagus nerve and intrinsic nerve plexuses in gut wall
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What is the enteric nervous system?
Consists of intrinsic nerve plexuses with short reflexes, sensory nerves, interneurons, excitatory, inhibitory
178
What cells detect a change in the quality of chyme? What do they secrete?
What are they important for?
Enterochromaffin cells - secrete enterogastrones
| For enterogastric reflex when chyme enters duodenum reflex causes change in motility and secretion
179
What can extrinsic nerves do?
Able to modulate activity of intrinsic nerves and enterogastrone activity
180
Is filling associated with increased intraluminal pressure?
No as
1) the length tension relationship of gastric muscles = greater plasticity
2) vagal stimulation to relax for accommodation of filling
181
How is food mixed?
Pacemaker cells from funds to pyloric region increase force of contraction and thicker muscle at pylorus for grinding/reducin particles size
182
How is motility altered?
mechano (stretch, tactile) and chemo (pH, protein) promote by modulating intrinsic pathway, vagal stimulation (cephalic phase) or gastrin release (G cells in pyloric mucosa)
183
When does the pyloric sphincter contract and what does this allow?
With every propulsive wave
solid particles propulsed backwards
luquid chyme can escape through semi-closed pylorus
regulated closely so duodenum not overwhelmed
184
What promotes gastric emptying?
protein, low pH, stretch = gastrin release, intrinsic nerve pathway
185
What inhibits gastric emptying?
duodenum chyme changes
- low pH = secretin
- high osmolality = CCK, gastric inhibit. peptide, secretin
- fat = CCK
- gastoenteric reflex to intrinsic nerves
186
What are migrating motor complexes?
Peristaltic waves propelling chyme
187
Where are giant peristaltic contraction formed? How are they different?
Distal S. I. and colon - longer in duration and greater in intensity
188
What drugs are used to normalise motility?
Prokinetics, increase ACh in parasymp cleft
| i.e. metaclopramide, cisapride
189
What drugs are used to reduce motility/activity:
antispasmodics: antag. ACh at parasymp receptor
- -> important to think about in oesoph as not all smooth muscle
- -> can also act as a stimulus for more vomiting
- -> overuse = atony and increased endotoxin absorption through damages mucosa
i. e. Hyoscine
190
What species have skeletal muscle in their oesophagus?
Cows - all striated
| Sheep - skeletal, with smooth at distal end
191
Can intrinsic movement occur with severing of nerves to reticulorumem are severed?
Yes low amplitude waves, from pacemaker, myogenic plexuses of leaky smooth muscle
192
What nerves have to be intact for extrinsic movement?
Vagal and splanchnic
| from gastric centre in medulla oblongata
193
What is involved in the extrinsic nerves' stimulation pathway?
```
Vagus = parasympathetic = ACh release to increase activity
Splanchnic = sympathethic = NA = decrease in activity
```
194
How does the oesophageal groove contract? Does this still occur in adults?
What nerve innervates this?
It is a reflex action by taste and machine receptors in buccal and pharyngeal cavities
yes also in adults with ingestion of salts
Vagal stimulation
195
How often does the reticule-rumen contract - in what direction and for what?
Split into two sequences
a) mixing: reticulum, dorsal rumen, ventral rumen = every minute
b) eructation: dorsal rumen, ventral rumen, reticulum = every second mixing sequence
196
Which animals have diphasic contraction of reticulum and rumen?
Sheep and goat, only slight relaxation between the two
197
How far apart are contraction sequences in cattle between rumen and reticulum?
3-4 seconds between rumen and reticulum
198
What happens at peak of contraction?
inspiration against closed glottis
199
What types of afferent reflexes are involved in reticular-rumen contraction
- buccal and pharyngeal - priced swallowing - detect type of feed, fresh/regurgitated
- oesophageal - stretch = saliva flow, contraction frequency increase
- reticulum - receptors, passive stretch = contract, excessive stretch = inhibit to secrete saliva, contract
- rumen - chemical change, gastric distension (= reflex eructation)
200
What does presence of VFA and lactic acid in rumen cause
inhibition od reticulum and rumen
201
what stimulates omasal motility? What inhibits it?
Receptors at ruminal-omasal orifice
| Inhibition by excessive distension = cease rumination, reduce contraction
202
What does a fall in abomasal pH cause?
reticular contraction increase
203
Distension in duodenum has what consequence?
inhibition of reticular luminal motility
204
What is the purpose of regurgitation?
To remasticate = increase in SA or particles for microbes to ferment into VFA
205
How often does regurgitation occur and how?
Depends on quality of roughage, roughly 1 minute intervals
Its a reflex that occurs when animal inspires against closed glottis = lowered pressure in oesophagus, positive pressure in rumen --> ingesta into oesophagus then waves of reverse peristalsis up
206
why is eructation necessary?
To remove the gas (CO2 and CH4) produced by microbes
207
How does eructation occur? What two factors are necessary for this to occur?
Its a reflex starting at dorsal blind sac where the rumen roof is lowered to push gas forwards and into oesophageal opening
Reticulum must be empty, and must be free gas (frothy = no stimulation)
208
What are the three major salivary glands found in a ruminant?
parotid, madibular and sublingual
209
Where does the parotid empty into? how does the duct path vary between sheep and cow?
At papilla of third upper molar
sheep: duct over masseter
cows: duct ventrally over mandible
210
What nerve is the parotid gland innervated by and what is its function?
By glossopharyngeal nerve (9)
- High volume, serous, high in bicarb to keep pH at 7.4. Buffered. Spontaneous flow. Reflex, parasymp. increases flow. stretch, tactile and chemical.
if symp stimulation - some protein added = trophic effect
211
What nerve innervates the mandibular and sublingual glands?
| Is there spontaneous flow?
facial nerve 7
| no spontaneous flow and lower output, reflex mainly from buccal region
212
What happens if parasympathetic stimulation of sublingual gland?
increased flow, minimal mucous content, vasdolidation
213
What happens if sympathetic stimulation of submandibular glands occurs
major increase in mucous content, vasoconstriction and trophic effect
214
Why is there a large water reserve in the ruminant fore stomach?
Needed for digestion, homeostasis and thermoregulation
215
Where is the water recycled?
Omasum (but ingest needs to be moist to pass)
| Parotid glands - both salt and water recycled and returned to rumen with saliva
216
Outline some strengths and weaknesses of ruminants
Strengths: diverse climates (head, salt), low quality feed, reproductive capacity reasonable and motility post partum, can travel
Weaknesses: high birth wt, limited defence, long and complicated digestion and need much pasture, susceptible to parasitic infection, overpopulation from seasonal breeding
217
What coordinates the vomiting reflex? Is it reverse peristalsis?
The vomiting centre in the medulla - the
brain stem.
Not reverse peristalsis, the stomach, oesophagus, and sphincters are relaxed
218
What signs are evident before vomit?
salivation, increased heart rate, pallor
219
How does vomiting proceed?
- inspiration with closed glottis = low pressure in oesphagus
- contraction of diaphragm and abdominal muscles = increase in abdominal pressure
- relaxation of stomach and sphincters = contents pushed into oesophagus
- high pressure in oesoph = pharyngo-oesoph sphincter opening --> vomitus in mouth
220
What are some stimuli that cause vomiting?
- unpleasant sight, smell (cerebral cortex processes)
- abnormal motion (semicircular canals)
- visceral organs (pain, inflam)
- blood borne - toxins, chemicals
221
What five areas are inputs to the vomiting centre?
- semi-circular canals: Histamine
- kidneys
- cortex: ACh
- CRTZ: dopamine, 5HT3, Neurokinin 1
- irritation and pain: 5HT3, ACh
222
What receptors are present on the vomiting centre?
Ach, Neurokinin1, 5HT3
223
What is the CRTZ?
Chemoreceptor trigger zone, in contact with blood borne toxin, breaches BBB
224
How is regurgitation different to vomiting?
- involves reverse peristalsis
- often shortly after eating with poorly undigested material
- not active
225
What are drugs known as which inhibit vomiting?
| Why are there different classes?
Anti-emetics
| Different classes as there are numerous pathways to initiate/block vomiting
226
What are the five classes of anti-emetics?
```
Neurokinin 1 receptor antagonist
Dopamine receptor antagonist
5HT3 antagonists
Anti-histamines
Phenothiazines
```
227
Give an examples and define site of action for neurokinin 1 receptor antagonist
Maropitant
| at CRTZ and vomiting centre
228
Where does a dopamine receptor antagonist work? Give an example and outline the side effects
At the CRTZ
ie Metaclopramide
additionally promotes ACh release and sensitivity to ACh in visceral smooth muscles = increased contractile strength --> increase gastric emptying
Side effects: dopamine is also found in the CNS, causes hyperactivity, depressopn, disorientation
229
Where is the 5HT3 antagonist active? What other disease is it useful for? Give an examples
i.e. odansetron
At vomiting centre and thought to also act on CRTZ
used in cancer therapy
230
When are antihistamines used? Give an example and possible side effects
- use if vomiting associated with middle ear infection, motion sickness
- can cause sedation
- i.e. promethazine
231
Why is dosing important for promethiazines? Give an example and side effects.
low dose = dopamine receptors blocked at CRTZ and periphery
high dose = MusR blocked to ACh at vomiting centre
Side effects: tremor, inco, sedation
i.e. prochloperazine
232
What are laxatives used for? Give some examples
To treat constipation
- add bulk, to drain more H20 (wheat bran)
- soften colon content (paraffin)
- osmotic (lactulose)
- increase propulsive contraction
233
What drugs are used for diarrhoea? Why are they not usually used?
Opioids - many side effects and habituation
| -- treat underlying cause of diarrhea
234
What stimulates a parietal cell to secrete HCl?
- vagus = ACh
- Vagus --> Mast/enterochromaffin cell --> Histamine
- Gastrin --> Mast/enterochromaffin cell --> Histamine
- Gastrin itself
235
How is HCl formed?
Not formed until in gut lumen
in cell: CA: froms H+ and HCO3-
HCO3- at basolateral: exchange with Cl-
H+ to lumen: exchange with K+
236
Why does the parietal cell stain eosinophilic?
Many mitochondria due to active process of forming H, Cl
237
Why is HCl production rate limiting for digestion?
It activates pepsinogen to pepsin
238
What occurs in the cephalic phase to cause HCl release?
- vagal reflex directly
- vagal reflex to G cell (pylorus) = gastrin release
- vagal reflex to EC cell = Histamine
239
What stimulates gastrin release during the gastric phase of digestion?
Mechano and chemo - to protein receptors = intrinsic nerves activated
neurotransmitter or hormone to parietal cell = increases cAMP
240
What inhibits HCl production?
PGE - decrease cAMP levels to decrease acid secretion
241
What happens in the intestinal phase? How does this reflect on acid secretion?
high fat, acid and hyper osmotic chyme enter duodenum - gastro-enteric reflex, enterogastrone release (secretin, CCK, GIP)
242
What are the four types of anti-ulcer drugs?
- H2 receptor antagonists
- proton pump inhibitors
- cytoprotective drugs
- antacids
243
Give examples of H2 receptor antagonists? How effective are they?
cimetidine, ranitidine
can reduce by 70%
other drug interactions, share metabolic pathways
244
Give example of a proton pump inhibitors. Are they potent? When are they used?
Omeprazole
very potent - irreversibly bind to transporter of H+
use for unresponsive ulcer
245
What are the two classes of cytoprotective drugs?
1) prostaglandin analogues -
i.e. misoprostol
mimic PGE, decrease acid release and promote repair as mucosal blood flow increases = higher cell turnover and more mucus secretion
2) ulcer bandaid
i.e. sucralfate
sticky sucrose gel, alluminium hydroxide = neutralisation
246
What do antacids contain? What are they used for?
contain Alluminium and Magnesium salts - give together
Mg - increases bowel motility
Al - decreases bowel activity
they neutralise HCl, bind bile acids, decrease pepsin activity
-- only symptomatic relief
